Counterpropagating optical solitons and vortices in photorefractive crystals
Author(s):
M. Belić;
M. Petrović;
D. Jović;
A. Strinić;
D. Arsenović;
J. Schröder;
P. Jander;
C. Denz
Show Abstract
Dynamical behavior of counterpropagating (CP) incoherent laser beams in photorefractive crystals is investigated. We perform experimental study displaying rich dynamics of three-dimensional CP optical solitons and formulate theory capable of capturing such dynamics. We find that our numerical simulations qualitatively agree with experimental findings for various CP beam structures. We also study numerically CP vortices in photorefractive crystals, in both space and time. The propagation of more complex CP beam arrangements, such as arrays of vortices, is also considered, and the transition from a few-beam propagation behavior to the transverse pattern formation dynamics is followed.
Photon sieves and modified Fresnel zone plates
Author(s):
Qing Cao;
Juergen Jahns
Show Abstract
Traditional Fresnel zone plates (TFZPs) can be used for the focusing and imaging of soft X-rays and extreme ultraviolet (EUV) radiations. However, the focal spot size of a TFZP is limited in technology by the minumum feature size (20-40 nm) that can be fabricated by lithography. Recently, a novel diffractive optical element called a photon sieve, which consists of a great number of pinholes properly distributed over the Fresnel zone, was proposed to overcome the resolution problem of a TFZP. Following the initial Nature paper, we have presented the simple individual far-field model for photon sieves and established the general theory for various modified FZPs. Here we present an overview of our research work in these areas. The related contents include the analytical descriptions for the diffracted fields of the individual pinholes and of the individual open rings, the selection conditions for the pinholes and for the open rings, the suppression of sidelobes, the physical limit of the resolution, the suppression of higher-order foci, the construction of a specific focal spot shape like a Gaussian focal spot, the equivalent pupil (or aperture) function theory, the diffraction efficiency, and the fast computation method for the individual diffracted fields. We also discuss the extension of the equivalent pupil function theory to apodized multilevel diffractive lenses.
3D object recognition using single exposure on-line digital holography
Author(s):
Daesuk Kim;
Bahram Javidi
Show Abstract
On-line phase shifting digital holography requires recording of multiple holograms. In this paper, we describe a real time 3-D object recognition system using single exposure on-line digital holography. In contrast to 3-D object recognition employing conventional phase shifting scheme which requires multiple exposures, this method requires only one single digital hologram to be synthesized and used to recognize 3-D objects. A benefit of the proposed 3-D recognition method is enhanced practicality of digital holography for 3-D recognition in terms of its simplicity and more robustness to external scene parameters such as moving targets and environmental noise factors. We show experimentally, that the single exposure on-line digital holography based 3-D object recognition method is capable of providing 3-D object recognition. The experimental results are compared with that of the on-line phase shifting digital holographic based 3D recognition.
Electromagnetic models for the analysis and design of complex diffractive microstructures
Author(s):
Tuomas Vallius;
Jari Turunen
Show Abstract
A review of electromagnetic models for the analysis of complex microstructures for controlling optical fields is provided. An overview of the most useful rigorous approaches and indications of their computational complexity as well as their domain of applicability is first presented. Then two types of approximate electromagnetic approaches are discusses: local interface techniques and local perturbation methods. These are compared to rigorous methods with a view on computational complexity and domain of applicability.
Measurement of ultrashort laser pulses with the splitting Dammann gratings
Author(s):
Changhe Zhou;
Enwen Dai;
Guowei Li
Show Abstract
The conventional beam splitter is a must optical element for splitting one femtosecond laser pulse, however, it suffers from the unpleasant chromatic dispersion caused by passing through the material due to the broadband spectrum of femtosecond laser. Measurement of femtosecond laser is usually realized by using an autocorrelator, frequency-resolved optical grating (FROG), GRENOUILLE and spectral phase interferometry for direct electric-field reconstruction (SPIDER). Usually they have to use the beam splitter for generating the two identical pulses for measurement of femtosecond laser. In this paper, we report another approach by using reflective Dammann gratings as the beam splitter. Two-layered reflective Dammann gratings provide an alternative solution of splitting by using the reflective structure, which has nice features of easy alignment, no chromatic dispersion, simple structure and low cost. Experimental implementation of the Dammann FROG apparatus by using two-layered reflective Dammann gratings generates the almost same result as the FROG method. This structure should be highly interesting as a novel approach for the measurement of femtosecond laser pulses. In addition, this structure has the possibility to replace the beam splitter in various applications, such as the pump-probe technique in femtochmistry and semiconductor, etc..
Invariance and image processing
Author(s):
Henri H. Arsenault;
Pascuala Garcia-Martinez
Show Abstract
Pattern recognition methods should be robust against small changes, yet be insensitive to certain modifications such as changes of position, intensity, orientation, scale and color. Those two requirements are somewhat contradictory. For example, linear filtering methods are invariant to changes in position, but by definition changes in the outputs are proportional to changes of intensity of the objects. We shall discuss recent advances in invariant pattern recognition, including nonlinear methods that allow maintaining the shift invariance of linear filtering while being insensitive to changes of intensity of objects of interest. Detection of targets in camouflage and multiobject recognition will also be discussed.
Near field diffraction of phase-shifted phase grating for side-writing fiber Bragg gratings
Author(s):
Yunlong Sheng;
Li Sun;
Joshua E. Rothenberg;
Hongpu Li;
Ying Wang
Show Abstract
The fiber Bragg grating (FBG) with a very high count, up to N=80, identical channels for dispersion compensators has been commercialized. The design utilizes the phase-only sampling, which requires η / N time higher refractive index modulation than the N times required by the amplitude sampling design. The phase sampling is implemented by inserting phase shifts in the FBG. Hence, the positive valued coupling coefficients of the FBG become complex-valued, which greatly increase the functionality and spectral performance of the FBG. In the fabrication of the phase-shifted FBG we find that the phase shifts in the phase mask for writing the FBG are not replicated into the FBG, as believed by many people, but are split into two half-magnitude phase-shifts due to the near field diffraction. We show the split of the phase shift by using the Finite Difference in Time Domain (FDTD) analysis and we show that this split of the phase shifts results in the FBG spectral asymmetry by a physical model of the phase-only sampling function distortion and by the FBG experiments. The new pre-compensating phase mask technique is introduced to remove the errors and therefore ensure the success of the high count multiple channel FBGs.
Techniques of noninvasive optical tomographic imaging
Author(s):
Joseph Rosen;
David Abookasis;
Mark Gokhler
Show Abstract
Recently invented methods of optical tomographic imaging through scattering and absorbing media are presented. In one method, the three-dimensional structure of an object hidden between two biological tissues is recovered from many noisy speckle pictures obtained on the output of a multi-channeled optical imaging system. Objects are recovered from many speckled images observed by a digital camera through two stereoscopic microlens arrays. Each microlens in each array generates a speckle image of the object buried between the layers. In the computer each image is Fourier transformed jointly with an image of the speckled point-like source captured under the same conditions. A set of the squared magnitudes of the Fourier-transformed pictures is accumulated to form a single average picture. This final picture is again Fourier transformed, resulting in the three-dimensional reconstruction of the hidden object. In the other method, the effect of spatial longitudinal coherence is used for imaging through an absorbing layer with different thickness, or different index of refraction, along the layer. The technique is based on synthesis of multiple peak spatial degree of coherence. This degree of coherence enables us to scan simultaneously different sample points on different altitudes, and thus decreases the acquisition time. The same multi peak degree of coherence is also used for imaging through the absorbing layer. Our entire experiments are performed with a quasi-monochromatic light source. Therefore problems of dispersion and inhomogeneous absorption are avoided.
Design and fabrication of micro-optical elements for the generation of various novel beams and its applications in optical tweezers
Author(s):
X. C. Yuan;
B. P. S. Ahluwalia;
W. C. Cheong;
L. S. Zhang;
W. M. Lee;
K. J. Moh;
S. H. Tao;
H. B. Niu;
X. Peng
Show Abstract
Light assisted micro-manipulation techniques have provided a non-invasive technique to investigate microscopic world. Employing micro-optical elements for laser beam shaping can aggrandize the trapping capabilities of conventional optical tweezers system. In the paper we report the design parameters and fabrication techniques of diversified micro-optical elements. High quality Laguerre-Gaussian beams, Bessel beams, self-imaged bottle beams and fractional Bessel beams were achieved using such micro-optical elements. We further integrated these micro-elements in conventional optical tweezers systems for various trapping applications. Such micro-elements were high efficient (in terms of power conversion) which is an important criteria to be incorporated with the optical trapping systems. Due to its micro-size such micro-elements are potential candidates to be integrated with lab-on-a-chip techniques to realize next generation "miniaturized optical trap".
Applications of diffuser for volume holographic memory and correlator
Author(s):
Guofan Jin;
Liangcai Cao;
Qingsheng He
Show Abstract
Correlation selectivity of the speckle encoding method with a diffuser in the reference beam or the object beam for volume holographic storage system is analyzed. Unlike Bragg selectivity, correlation selectivity has no sidelobes and does not depend on the thickness of the recording medium. Thus the intrapage crosstalk can be greatly suppressed. For a volume holographic memory, the reference beam is modulated with the diffuser, which can sharpen the diffraction efficiency curve (versus the angular deviation). It helps increase the storage density and improve the quality of the reconstructions. For a volume holographic correlator, the signal beam is modulated with the diffuser, which can sharpen the correlation peak and suppress the correlation sidelobes. It helps improve the parallelism and accuracy of the holographic correlator. It is shown that the diffuser techniques are effective and feasible to improve the performance of the volume holographic storage and correlation system.
Self-focusing in a BaTiO3 crystal without external electric fields
Author(s):
Armin Kiessling;
Anne Rausch;
Vladislav Matusevich;
Richard Kowarschik
Show Abstract
Self-trapping in photorefractive materials is a well-known effect and was widely investigated during the past decade. Usually, the light induced Pockels effect in photorefractive crystals compensates the natural divergence of the beam, therefore, creating a beam with constant diameter, a spatial soliton. The Pockels effect is based on the redistribution of charges in the crystal and can be forced by an external electric field. Due to the crystallographic structure of their elementary cell (tetragonal phase for temperatures below the Curie temperature) some crystals as BaTiO3 or SBN possess a preferential direction the so called c-axis. They are spontaneously poled but in a statistical manner. Applying an external electric field with temperatures higher than the Curie-temperature and then decreasing the temperature all elementary cells will be orientated in the same direction, the crystal will be poled. This poling remains even if the external field is switched off. This means that the crystal obtains a remanent internal electric polarization. The experiment shows that this internal polarization can be understood as an effective electric field and, therefore, the self-focusing of appropriate laser beams is possible. We show the self-focusing of beams of a HeNe-laser (Λ = 633 nm, P = 0.1 μW, 2w0 = 4 μm) in BaTiO3 without external electric fields and discuss the effect in dependence on the polarization and the intensity of the light beam at the entrance surface of the crystal. The experimental results are compared with numerical solutions of the stationary paraxial normalized wave equation.
Mapping of Hermite-Gaussian modes in ABCD systems
Author(s):
Tatiana Alieva;
Martin J. Bastiaans
Show Abstract
The orthonormal set of Hermite-Gaussian modes maps into another orthonormal set after propagation through a first-order optical system. A compact expression for these modes is derived. The introduction of a novel class of orthonormal modes is useful for non-interferometric phase recovery techniques and simplifies the design of mode converters and information processing systems.
Beam self-trapping in a BCT crystal
Author(s):
V. Matusevich;
A. Kiessling;
R. Kowarschik;
A. E. Zagorskiy;
V. V. Shepelevich
Show Abstract
We present some aspects of wave self-focusing and self-defocusing in a photorefractive Ba0.77Ca0.23TiO3 (BCT) crystal without external electric field and without background illumination. The effects depend on the cross-section of the input beam. We show that by decreasing of the diameter of the input beam from 730 μm the fanning effect disappears at 150 μm. A symmetrical self-focusing is observed for input diameters from 150 um down to 40 μm and a symmetrical self-defocusing for input diameters from 40 μm down to 20 μm. The 1D self-trapping is detected at 65 μm in BCT. Light power and wavelength are correspondingly 3 mW and 633 nm. The experimental results are supplemented with numerical calculations based on both photovoltaic model and model of screening soliton.
Self-images of periodic phase elements in the fractional Fourier transform domain
Author(s):
Mykhailo V. Shovgenyuk;
Yuri M. Kozlovskii
Show Abstract
General conditions of periodic phase elements self-images forming (Talbot effect) in the fractional Fourier transform (FrFT) domain is given. Analytical solution of the FrFT images intensity distribution for the different forms (binary, linear, parabolic and others) of periodic elements low-level cell profiles is presented. Intensity difference ▵Ι measuring of the FrFT periodic self-image allow to determine the phase difference ▵φ of periodic elements low-level cell profile. Theory of the FrFT images forming of periodic phase elements based on signal distribution method is given. We use ambiguity function Aff* (χ0;ω0) in difference conjugate coordinates (χ0;ω0) as base functional of the periodic phase element distribution. The FrFT distribution Aupup*(χ0;ω0) corresponds to the rotation matrix Tφ which describe rotation of the input signal distribution on an angle φ=pπ/2, p=0÷ - the FrFT parameter. The signal distribution method allow to obtain general formula of intensity distribution of the periodic phase element FrFT image. Theoretically proved that at condition F0/tanφ=1, where F0=T2/4λd - Fresnel number, T - phase element period, λ - wave-length, d - length, periodic phase elements self-images are forming in the FrFT domain. In this case interference term is written as δ - function and intensity distribution I(χ) of the FrFT self-images is forming as superposition of the cross displaced on a quarter of period self-images of neighboring phase low-cells. Analysis of the FrFT self-images forming at condition 2F0/tanφ is also given. The results of numerical calculations of the periodic phase elements self-images at the different values of the FrFT parameter p are presented. Analytical dependence of the FrFT self-images contrast from phase difference ▵φ is obtained and the questions about phase microrelief parameters restoration of the phase element low-cell are discussed.
The dual-wave optical bistable scheme
Author(s):
Vyacheslav A. Trofimov;
Pavel V. Dogadushkin
Show Abstract
We report about the dual-wave optical bistable scheme realized on the base of light energy absorption by molecular gas. Switching from one state to another takes place due to optical pulse action on one of the frequencies. Under certain conditions after switching of system to the upper state, it remains in this state as much as long. That allows to realize long-time dynamic memory and various logic operations. Using of dual-wave action on molecular gas leads as well to decreasing in tens and hundreds times the intensity at which switching of system takes place.
The obtained results can find wider applications, and not only to considered object - molecular gas, since we do not use its specific properties in our report. The results can be applied, for example, to a polymer, that is more preferable to practice.
Constructing a three-dimensional face model by a stereo method and its application to optical parallel face recognition
Author(s):
Eriko Watanabe;
Nobuko Arima;
Kashiko Kodate
Show Abstract
The authors have proposed and fabricated the FARCO (Fast Face Recognition Optical Correlator) based on Vanderlugt Correlator1 with a super-higher-speed of 1000 faces/s2,3. Using its rapid data processing capability, a robust recognition system can be constructed by registering three-dimensional (3-D) face data. There are a number of techniques to obtain 3-D data. Since the system deals with people, it is desirable that instant measurement and non-contact data processing are secured. To meet these requirements, we took photographs and created database of facial images adopting three digital cameras based on the stereo method. Three simultaneously-photographed images were given angular variations from top to bottom and from left to right by 3-D modeling by use of the software. Using our database and these facial images with angular variations, we proceeded on to examination of the system performance, following the algorithm for recognizing images in motion. The paper begins with the process of constructing, the first database for facial images using 3-D model, with those image files made by three cameras. Photographs were taken from the front and to right and left 15degrees. The 3-D model is constructed by these facial images. Making the database from the 3-D model, two-dimensional (2-D) facial images are clipped from part of the model at shifting in each 5degrees from top to bottom, and then from left to right. As a result, the facial images with angular variations were correctly recognized in the database. Through the assessment, the 3-D modeling system proved to be most effective.
Constructing a safety and security system by medical applications of a fast face recognition optical parallel correlator
Author(s):
Eriko Watanabe;
Mami Ishikawa;
Maiko Ohta;
Yasuo Murakami;
Kashiko Kodate
Show Abstract
Medical errors and patient safety have always received a great deal of attention, as they can be critically life-threatening and significant matters. Hospitals and medical personnel are trying their utmost to avoid these errors. Currently in the medical field, patients' record is identified through their PIN numbers and ID cards. However, for patients who cannot speak or move, or who suffer from memory disturbances, alternative methods would be more desirable, and necessary in some cases. The authors previously proposed and fabricated a specially-designed correlator called FARCO (Fast Face Recognition Optical Correlator) based on the Vanderlugt Correlator1, which operates at the speed of 1000 faces/s2,3,4. Combined with high-speed display devices, the four-channel processing could achieve such high operational speed as 4000 faces/s. Running trial experiments on a 1-to-N identification basis using the optical parallel correlator, we succeeded in acquiring low error rates of 1 % FMR and 2.3 % FNMR. In this paper, we propose a robust face recognition system using the FARCO for focusing on the safety and security of the medical field. We apply our face recognition system to registration of inpatients, in particular children and infants, before and after medical treatments or operations. The proposed system has recorded a higher recognition rate by multiplexing both input and database facial images from moving images. The system was also tested and evaluated for further practical use, leaving excellent results. Hence, our face recognition system could function effectively as an integral part of medical system, meeting these essential requirements of safety, security and privacy.
Study and manufacture of gain flattened S-band distributed dispersion compensation fiber Raman amplifier
Author(s):
Bizhi Dai;
Zaixuan Zhang;
Laixiao Li;
Haifeng Xu;
Dan Geng;
Honglina Liu;
Jianfeng Wang;
Chenxia Li;
Tiao Liu;
Insoo S. Kim
Show Abstract
Now the communication band of fiber focuses on C-band, but with increasing demand of fiber communication capacity, the communication band will extend to the S-band and L-band and fiber Raman amplifier will play a very important role in this process. In this paper, actual fiber Raman gain spectrum using single high power fiber Raman laser as pump was tested and the proper chirped Bragg fiber grating as gain flattening filter was designed to flatten actually tested gain spectrum. Besides, FWDM (film wavelength division multiplexer) is used as the multiplexer of signals and 1427nm/1505nm CWDM (coarse wavelength division multiplexer) is used as pump-signal coupler. The gain media are 50 km G652 fiber and 5km DCF (dispersion compensation fiber). The gain is 10dB of S-band fiber dispersion compensation Raman amplifier from1487.88nm~1541.88nm (total 53nm bandwidth) with gain ripple ± 0.6dB was successfully obtained. Besides, the effect caused by different location ways of different type fibers was also discussed. It is very significant for extending range of communication band of fiber and increasing the capacity of fiber communication especially for ultra-long haul and ultra-high capacity communication system.
Audio-signal watermarking in 3-D space with a virtual-optics imaging modality
Author(s):
Peng Zhang;
Xiang Peng
Show Abstract
In this paper, we present a new approach for digital audio watermarking scheme in three-dimensional (3-D) space. The architecture of 3-D digital audio watermark insertion is on the basis of virtual optics imaging system (VOIS), which relies on the propagation of virtual light wave through discrete Fresnel diffraction (DFD). The embedding strategy of a watermark with a methodology of the VOIS is analyzed in detail under the framework of Fourier optics. In order to test the robustness against signal processing, we carried out several detection experiments. Common audio signal manipulations like adding noise, filtering and data compression are used. Simulation results have shown a good agreement to theoretical predictions.
Data processing methods for terahertz transmitted spectral imaging
Author(s):
Zhengwei Zhang;
Weili Cui;
Guozhong Zhao;
Yan Zhang;
Cunlin Zhang
Show Abstract
THz wave imaging is a new and promising technology for material distinguishing and non-destructive testing. The processing of the time domain waveform acquired at each pixel of the image is one of the most important aspects of the THz imaging. Due to the diversity of samples in the practical applications, signal processing approaches are quite different. A good method permits high quality of the images. In the previous papers, some methods have been adopted to generate the image of the object; however, these methods have not been compared, and the reason for choosing certain approach has not been given. Therefore, it is very important to discuss the difference of different imaging approaches for a sample and to choose the best one. In this presentation, several data processing methods for terahertz transmitted spectral imaging based on classical transmitted scanning imaging setup and the Fourier transform, including time-domain maximum-amplitude (minimum-amplitude) imaging, time-domain peak-to-peak amplitude imaging, time-domain time delay imaging, frequency-domain fixed frequency amplitude (power) imaging, as well as frequency-domain fixed frequency phase imaging, are discussed and compared. The results indicate that the imaging quality is different for different approaches; furthermore, the optimal imaging methods for the samples used in this paper are also different.
Wavelength controlled optical phased array using photonic crystal
Author(s):
Xiang Wang;
Weiwei Hu;
Anshi Xu
Show Abstract
To control optical phased array by steering the wavelength of the light source, this paper presents the method using 2-D photonic crystal waveguides, which replace the conventional waveguides to guide and form the beam in the array. As a result, we present a 1-D optical phased array, whose optical beam can scan an angle from -40 degree to +40 degree with a SNR about 15 dB by a relative simple device in ±3 nm tuning at 1550 nm.
Design and implementation of a nanometer phase-shifting interferometer for micro-surface profile measurement
Author(s):
Wei Zhu;
Wencai Jing;
Hongxia Zhang;
Dagong Jia;
Yimo Zhang;
Yan Li;
Feng Tang
Show Abstract
A vertical-shaft-type Mirau white-light phase-shifting interferometer is designed based on white-light phase-shifting interference microscopy in this paper. The interferometer is composed of an illumination and interference imaging part, a piezoelectric transducer in the vertical direction, a two-dimensional scanning part in the test surface, image collection and interferograms analysis part. The light illuminates the sample and the test surface uniformly, and the interferogram is formed. In order to get phase-shifting, the move of the objective is driven by PZT. The three-dimensional scanning system consists of a two-dimensional horizontal motorized stage and a vertical piezoelectric transducer. Multi-aperture stitching extends the measurement range in the test surface. A new pixel divided phase-extracting algorithm was put forward in combination with a residues-pretreatment phase-unwrapping algorithm based on image segmentation. The algorithm is used to minimize the phase-shifting error and nonlinearity error of the detector. The surface profile of a fiber connector with fiber inserted was measured. Mean value of the protrusion between fiber and fiber connector was measured to be 45.7nm, with 0.9 nm error. The mean height of a spot on the end surface of fiber connector was measured to be 23.6nm, with 0.7nm error.
Measurement of distributed mode coupling in high birefringence polarization-maintaining fiber with random polarization modes exited
Author(s):
Feng Tang;
Wencai Jing;
Yimo Zhang;
Ge Zhou;
Dagong Jia;
Hongxia Zhang;
Li Ren
Show Abstract
A white light Michelson interferometer is designed to measure the distributed polarization mode coupling in High birefringence polarization-maintaining fibers (HiBi-PMFs). Using a Michelson interferometer to compensate the optical path difference induced by the modal birefringence of PMF, both power coupling intensity and position of the coupling point can be acquired. Traditionally, this technique requires only one polarization mode in the PMF to be exited or both polarization modes to be exited with equal intensity. This needs precise alignment of the polarization direction with the principal axis of the PMF. In practice, it's not easy to realize. In this paper, the influence of the incident polarization extinction ratio (PER) on the measurement result was evaluated theoretically and experimentally. A polarization state adjusting mechanism is designed. An analyzer can be oriented at any angle of the PMF's principle axes. By alternating this angle between 0o, 90o and 45o, the incident PER can be calculated and the measurement can be carried out with random exited polarization mode. An instrument was designed and implemented to verify this scheme. Spatial resolution better than 7cm and coupling strength sensitivity less than -75dB are realized.
A fast fourier transform algorithm for surface profiler based on scanning white-light interferometry
Author(s):
Wendong Zou;
Nan Du;
Yanjun Fu;
Huirong Xiao;
Qiang Du
Show Abstract
In this paper, we introduce a fast Fourier transform algorithm for three-dimension surface analysis in a scanning white-light interferometry system. The interferograms, one for each pixel of the interference image, representing the variation in intensity as a function of scan position, are transformed into the spatial frequency domain and the relative surface height information for each point is extracted from the complex phase as a function of frequency. For optimal speed and efficiency with a minimum of resources, a simple frequency-based discriminator is used in data acquisition to identify the modulation region and a circular buffer technique is adopted for retaining the complete interferogram efficiently. Applying this method to the mapping of the endface topography of fiber connector, we've achieved high measurement repeatability and speed.
Wave-front reconstruction for lateral shearing interferometers with big shear
Author(s):
Peiying Liang;
Jianping Ding;
Jin Zhou;
Hui-tian Wang
Show Abstract
A novel algorithm is proposed to reconstruct two-dimensional wave-front from differential wave-fronts measured in shearing interferometer. Two 1-dimensional estimates of object wave-front are computed using Fourier transform from differential wave-fronts, and then the 2-dimensional wave-front distribution is derived by use of least-square fitting. The algorithm is applicable to cases in which the shear amount is larger than one sampling interval, and thus alleviates the limitation on the shear amount imposed by conventional algorithms. Investigations into reconstruction accuracy and reliability are carried out by computer simulation. Optical experiments are made in a lateral shearing interferometer based on double-grating, and 3-dimensional surface profile of optical element under test are measured and presented. The analysis and discussion are also given in the final part of this article.
Real-time measurement and high-speed identification of highway pavement surface deformation
Author(s):
Lin Fu;
Anzhi He;
Zhenhua Li
Show Abstract
Pavement distress status is very important to investigate and evaluate pavement condition, which is characterized by distress types, degree and area. The measurement of three dimensions structure of pavement surface is of great value for the judgment of pavement distress status. Optical three dimensional profilometry is a well established technique for the measurement of three dimensions surface profiles, which has many advantages such as non-contact, high precision, rapid measurement and high automatization degree. Grating projection based Fourier transform profilometry encodes object height information into deformations of sine fringes projected on the object. This profilometry can measure objects in orthogonal direction. In this paper, the application of the Fourier transform profilometry is discussed in a dynamic real-time measurement system of highway pavement surface profile. By the introduction of a specific reference plane, an adapting template matching method based image characteristic identification is developed for Fourier transform profilometry. Distressed pavement surfaces can be identified by the method. It realizes real-time measurement and high-speed identification of highway pavement surface distress by quantitatively presenting pavement deformations and the coordinates of distressed pavement surfaces.
A novel method for the implementation of optical interleaving
Author(s):
Chao Shi;
Zheng Wang;
Zhangyuan Chen;
Yuping Zhao;
Juhao Li
Show Abstract
This paper proposes a new method which uses the Cross Gain Modulation (XGM) in the Semiconductor Optical Amplifier (SOA) to realize optical interleaving. Different from the traditional optical wavelength interleaving, the proposed optical interleaving is the interleaving of codes. Three modules and theoretical analysis are presented, and an experiment is designed to validate these kinds of optical interleaving modules.
A high-speed realtime vibration measusement and analysis system based on DSP technology
Author(s):
Guoming Song;
Houjun Wang;
Jingfeng Wang
Show Abstract
A real-time vibration measurement and analysis system based on fiber optic sensor and high-speed DSP processor is introduced. Measurement is emphasized in recent engineering field for checking the bearable capability of objects on vibration. Real-time processing ability, testing accuracy and dynamic testing range are crucial aspects in a measurement and analysis system. Using fiber optic displacement sensor to capture the dynamic measurements during a vibration test is presented. FFT recursion algorithms based on split-radix and twiddle vector is proposed for achieving fast speed frequency analysis of vibration signals. Experiment results show the superiority of the proposed approach compared to the one based on single-chip processor. High speed and real-time testing power is achieved in this system.
Bayesian approach to limited-projection reconstruction in moiré tomography
Author(s):
Yang Song;
Bing Zhang;
Anzhi He
Show Abstract
Reconstructions with complex flow fields and limited-projections are two main serious problems that are often encountered in practical OCT cases. While moire tomography has its inherent advantages, such as low mechanical stability demand, to be applied in these complex flow fields. But due to the complex style in its formulation, it is not used as widely as general OCT methods. A proof is given to get an equation which explicit expresses the relationship between moire tomography and general CT methods. A Bayesian maximum a posteriori (MAP) approach is used to reconstruct fields with limited-projections. Based on these works, Numerical experiments are proposed to reconstruct simulated fields with ART and MAP approaches separately.
CR image filter methods research based on wavelet-domain hidden markov models
Author(s):
Jun-li Wang;
Yun-peng Wang;
Da-yi Li;
Shi-wu Li;
Hai-lin Kui
Show Abstract
In the procedure of computed radiography imaging, we should firstly get across the characters of kinds of noises and the relationship between the image signals and noises. Based on the specialties of computed radiography (CR) images and medical image processing, we have study the filtering methods for computed radiography images noises. On the base of analyzing computed radiography imaging system in detail, the author think that the major two noises are Gaussian white noise and Poisson noise. Then, the different relationship of between two kinds of noises and signal were studied completely. By considering both the characteristics of computed radiography images and the statistical features of wavelet transformed images, a multiscale image filtering algorithm, which based on two-state hidden markov model (HMM) and mixture Gaussian statistical model, has been used to decrease the Gaussian white noise in computed images. By using EM (Expectation Maximization) algorithm to estimate noise coefficients in each scale and obtain power spectrum matrix, then this carried through the syncretized two Filter that are IIR(infinite impulse response) Wiener Filter and HMM, according to scale size ,and achieve the experiments as well as the comparison with other denoising methods were presented at last.
Individual information beam broadcasting system using a PAL-SLM based CGH beam former for the location based information services
Author(s):
Shunichi Osawa;
Hideo Itoh;
Yoshiyuki Nakamura;
Takuichi Nishimura;
Xin Lin;
Masamitsu Tokuda
Show Abstract
As an implementation of ubiquitous information service environments, we have been researching location-based information service systems at indoor and short distance area. The system should provide adequate information services, which fit the user's attributes, such as language, knowledge level and the volume of information, what is so-called "Right now, Here, and for Me" information services. Keeping privacy and security of the user is an important issue. Spatial optical communication technique is used for the system because the technique is easy to implement a location- and direction-based communication system. Information broadcasting in an area can be realized by an omnidirectional modulated light emission. However, the omnidirectional beam causes spill out of secure information to others, and has lower energy conservation than a focused beam communication. In this paper, a new spatial optical information broadcasting system, which can focus modulated beams only to intended users. CGH (Computer Generated Hologram) technique on a SLM (Spatial Light Modulator) is proposed and demonstrated. The system is composed of a PAL-SLM (Parallel Aligned Nematic Liquid Crystal Spatial Light Modulator), an eye-safe semiconductor laser or a semiconductor laser pumped YAG laser for the beam emitter, and an infrared video camera with an infrared LED illuminator for user locator. Experimental results of beam deflecting characteristics are described on beam uniformity, deflecting angle and the enhancement, communication characteristics, and real time tracking of user with a corner-reflecting sheet.
Fabrication, characterization and testing of (111) FePt L10 for heat assisted magnetic recording
Author(s):
D. Karns;
J. Y. Kim;
B. Lu;
G. Ju;
X. Wu;
E. Gage;
A. Roy
Show Abstract
The fabrication, characterization and recording of granular FePt L10 (111) oriented media are discussed. The granular structure is obtained through the addition of SiO2 during the deposition. It exhibited grain sizes less than 10 nm on average after post annealing. The effect of adding SiO2 is examined in the following manner. The crystallographic structure is examined through X-ray diffraction. The microstructures of the grains are observed by transmission electron microscopy. Hysteresis loops were obtained with a custom built polar magneto optic Kerr effect magnetometer (PMOKE) with field range up to 20 kOe and a Quantum Design SQUID magnetometer with field capability up to 50 kOe. Heat assisted magnetic recording was performed utilizing a custom designed and built heat assisted magnetic recording spin stand. The heat assisted magnetic recording spin stand was utilized to examine incident laser power requirements along with applied magnetic flux density requirements for recording. Data was successfully recorded and readout on high anisotropy FePt L10 (111) media that was not writable with perpendicular magnetic recording techniques. Recording results indicate that due to the high Curie temperature and large magnetization, a large applied magnetic flux density and a high recording temperature are required for saturation recording.
Simultaneous excitation of the low and high frequency oscillations of the space charge gratings in photorefractive crystals
Author(s):
Mikhail Bryushinin;
Vladimir Kulikov;
Igor Sokolov
Show Abstract
We study the effect of simultaneous excitation of the space charge and conductivity running gratings in photorefractive crystals. For the realization of such regime we illuminate the crystal by the interference pattern oscillating with frequency ω. The combination of external dc and ac (with frequency Ω) voltages is applied to the crystal as well. If the frequencies of the phase modulation and ac field are equal to the eigenfrequency of the conductivity grating oscillation (high-frequency branch of the space charge oscillation) ω,Ω=ωpc, and their difference is equal to the eigenfrequency of the space charge grating oscillation (low-frequency branch) |ω-Ω|=ωsc, then the former grating oscillation effectively interacts with the ac component of applied field giving rise to the latter one. The experiments are performed in the photorefractive sillenite crystals (Bi12SiO20, Bi12TiO20) using both the diffraction and non-steady-state photo-EMF techniques. The dependencies of the detected signal amplitudes on the difference frequency ω-Ω (for fixed Ω) and dependencies of the detected signal amplitudes on the frequency of phase modulation ω (for fixed ω-Ω) are measured. They demonstrate the excitation of both the low and high-frequency eigenmodes of the space charge oscillation and provide estimations of material parameters, namely, the mobility of photoelectrons: μ=(1.1-1.4)×10-2 cm2/Vs (Bi12SiO20, λ=532 nm, T=296-298 K), μ=1.5×10-2 cm2/Vs (Bi12SiO20, λ=442 nm, T=293 K), and μ=3.1×10-3 cm2/Vs (Bi12TiO20, λ=532 nm, T=293 K). The application of the developed techniques for the characterization of widegap semiconductors and for the detection of optical phase-modulated signals is discussed.
Generation of chain like beams
Author(s):
M. L. Calvo;
J. A. Rodrigo;
T. Alieva
Show Abstract
Wide application of the laser beams in science, technology and biomedicine demands the generation of the beams with desirable structure. In particular for optical trapping the beams with high transversal gradient of intensity distribution or doughnut like structures which carried out the orbital angular momentum are designed. In the recent study of the diffraction on the fractal Cantor zone plates [1-5] the possibility to generate the beams with capsule like structure (closed cylinder with the axis along the direction of beam propagation) for a certain distances has been discovered [5]. This peculiar form of the beam can be used for three dimensional particle trapping. Nevertheless the fractal zone plates are not unique gratings that generate this type of structures.
Propagation law for Hermite- and Laguerre-Gaussian beams in first-order optical systems
Author(s):
Martin J. Bastiaans;
Tatiana Alieva
Show Abstract
Starting from Hermite-Gaussian beams, we generate a general class of rotationally symmetric beams. These beams are Laguerre-Gaussian beams, parameterized by two parameters h and g, representing the curvature and the width of the beam, respectively. The Wigner distribution of each member of this class is readily derived from
the Wigner distribution of the Hermite-Gaussian beam from which it is generated. If these Laguerre-Gaussian beams propagate through an isotropic abcd-system, they remain in their class, while the propagation of the complex beam parameter h ± ig satisfies the well-known abcd-law.
Design of an opt-electronic knowledge-based system
Author(s):
Xuan-Jing Shen;
Qing-Ji Qian;
Ping-Ping Liu
Show Abstract
In this paper, based on the analysis of the features of knowledge-based system and optical computing, a scheme of an opt-electronic hybrid system (OEHKBS) model and its hardware supporting system. The OEHKBS adopts a knowledge representation based on matrix and its inference and learning arithmetic which suitable for optical parallel processing. Finally, the paper analyses the performance of the OEHKBS, which can make the time complexity for solving Maze problem reduce to O(n).
A method for improving the precision of motion vector estimation based on gyroscope
Author(s):
Yongxiang Zhang;
Hui Sun;
Jingwu Xiong
Show Abstract
The piezoelectric gyroscope is regarded as an important device which measures the motion vector among frames of the dynamic image sequences; precision of its output signal directly determines the precision of the image stabilization. Analyzing the characteristics of output noise of gyroscope, it is available for us to suppress the output noise by applying the median filtering algorithm and wavelet transformation. The experiment results of electronic image stabilization have shown that this method can improve the precision of motion vector estimation effectively.
Implementation of a novel algorithm on ADCP signal processing system
Author(s):
Hao Zhu;
Wenyao Liu
Show Abstract
The ADCP (Acoustic Doppler Current Profiler) technique is the current hot topic of measuring the water velocity. Further more, the frequency estimation algorithm is critical for it. A novel frequency estimator-ELMS for a single complex sinusoid in complex white Gauss noise is proposed. The estimator needs less data than conventional FFT (Fast Fourier Transform) algorithm. The results indicate that the robust algorithm can estimate the spectrum value efficiently when the SNR=0DB.
Study on Fourier transforms profilometry based on bi-color projecting
Author(s):
Wenjin Chen;
Xianyu Su;
Yiping Cao;
Qiancan Zhang;
Liqun Xiang
Show Abstract
We propose an improved FTP based on bi-color grating projecting. Two individual sinusoidal fringe patterns with π phase difference can be decoded from the deformed bi-color sinusoidal fringe pattern captured by color digital camera. Accessing the two fringe patterns, we can not only eliminate zero order spectra but also automatically build a binary mask at the same time to mark the valid measurement area easily, by which unwrapping phase time is shorten as well as phase error from invalid area is not transferred into valid area; Furthermore, we can easily expand the captured non-full-field deformed fringe pattern to form full field fringe pattern to guarantee frequency resolution.
A new random-phase-screen time series simulation algorithm for dynamically atmospheric turbulence wave-front generator
Author(s):
Gang Wang
Show Abstract
A new simulation algorithm of random phase screen time series for the purpose of generating dynamically atmospheric turbulence distorted wave fronts using Zernike polynomials is described in this paper. Both spatial and the temporal statistics of atmospheric turbulence are considered in this technique. Turbulence phase is simulated by using a set of random-process-generated Zernike coefficients. Not only Kolmogorov but also non-Kolmogorov statistical spectrum can be modeled successfully using this algorithm. Our results show that smooth time-evolving turbulence wave fronts can be generated perfectly at given time frequency interval.
A Mach-Zehnder nonzero order joint transform correlator for polychromatic pattern recognition
Author(s):
Chungchen Lee;
Chulung Chen
Show Abstract
In this article, we apply a novel method to polychromatic pattern recognition with a Mach-Zehnder nonzero order joint transform correlator. It is achieved by using the special arrangement of separated polychromatic components of objects and reference images and Lagrange multipliers technique to synthesize a reference function in the input spatial domain. The purpose is to sharpen the correlation peak and to reduce correlation sidelobes. Besides, we cleverly utilize the Stokes relations to remove the large zero order term directly in one step in this structure. Simulation results are presented to illustrate the improvements.
On the kinematics of correlated pictures or generalized moiré patterns
Author(s):
Mario Garavaglia
Show Abstract
Generalized moire patterns refer in this paper to correlated pair of finite sized transparencies T1 and T2 containing any kind of features, from the simplest sequence of parallel and equidistant opaque stripes and transparent slits -as a Ronchi grid- to more elaborate geometrical grids -bar codes or fractal Cantor grids- and, finally, up to random arranges of irregular motifs -as a white-light speckle photograph- or any type of photographs. The purpose of this paper is discussing the kinematics of correlated patterns as a function of T1 on T2 relative displacements.
Image resolution influence on determination of resin injection rock mass
Author(s):
Weixing Wang;
Eva Hakami
Show Abstract
In the context of nuclear waste repositories, an important approach to understanding brittle rock mass behavior to integrate new and powerful observational and numerical methods with multi-functional 3-D imaging and visualization techniques. Since 1994, Swedish Nuclear Fuel and Waste Management Company (SKB) have identified the need for a better understanding of radionuclide transport and retention processes in fractured rock. As a cooperation project between Sweden and China, we sampled a number of rock specimens for analyze rock fracture network by optical image technique. The samples are resin injected, in which way; opened fractures can be seen clearly by means of UV (Ultraviolet) light illumination. In the study period, we used different optical focuses to obtain the images from the same samples; we found that Image resolution influences on porosity determination of resin injected rock mass. This paper presents and discusses the six issues based on our research results: (1) Fracture porosity increases as camera focus distance decreases; (2) Porosity increases as illumination increases in resin injected fracture images; (3) To roughly estimate the porosity, the low resolution image can be used; (4) To collect more details of fracture information, the high resolution image is needed; (5) The resolution of image should be determined based on the aim of fracture analysis; (6) To acquire high resolution image, constructing a special illumination (standard) box maybe helpful to avoid light reflection and diffusion.
Study on urinary sediments classification and identification techniques
Author(s):
Mei-li Shen;
Dian-ren Chen
Show Abstract
In this paper, a kind of computer microscopic urine sediment analyzer is introduced with industry computer as image processor and controller. The system categorizes and recognizes the visible urine sediment components based on the technology of image processing and support vector machine (SVM). Firstly, microscope enlarges the visible components in the urine sediment quantitative analysis board. Then, light signals is transformed as video electrical signals by CCD camera and the image sampling board samples and saves it as files. The system preprocessing the sampled image using different methods including color image transformed gray image, filtering, image sharpening, image enhancing, segmenting visible component, edge tracking and repairing and so on. Moreover, sampled image feature is extracted, trained and classified. Using support vector machine method classifies and counts the urine sediment visible components and gets the number in the unit volume. The system not only realizes urine sediment visible components classifying and recognition, but also describes its feature from morphology. The SVM trains those features and cross validation in order to get the optimal SVM kernel function and parameters. In the end, it classifies tested image according to the model. Experimental results show that this method is provided with the characteristics of method directness, strong robustness and good stability.
Rotation-invariant volume holographic correlator by combining the synthetic discriminant function and wavelet filtering
Author(s):
Dayong Wang;
Shengtong Feng;
Zhuqing Jiang;
Shiquan Tao
Show Abstract
In this paper, it is proposed to record the matched filter in the photorefractive crystal by using the synthetic discriminant function as the input. The synthetic discriminant function is generated by training a set of rotated object images. Multiple matched filters are stored by angle-multiplexing in the same volume. Due to the large difference among the optical throughouts of the images, a wavelet transform filter is directly introduced into the experimental setup to improve the object discrimination largely. Computer simulation and experimental results demonstrate that it is possible to achieve the rotation-invariant pattern recognition with the proposed method
Wavelet-fractal based compression of ophthalmic image
Author(s):
Xiu-ying Zhao;
Lin-pei Zhai
Show Abstract
This study is designed to determine the degree and methods of digital image compression to produce ophthalmic images of sufficient quality for transmission and diagnosis. Fractal based compression techniques, which provide a large compression ratio for grayscale images have been reported in the literature. Fractal coding is based on the fractal theory of iterated transformations. But, it's searching and mapping algorithm cannot address the need of real-time. To improve the real-time performance of the algorithm, we use wavelet transforms to decompose images. The wavelet transform is a natural tool for analyzing fractal block coders since wavelet bases possess the same type of dyadic self-similarity that fractal coders seek to exploit. We propose a method of fractal coding the weighted wavelet subtree. Experimented results show that the improved hybrid image can improve the PSNR of the rebuild image at the same compression ratio.
An image hiding algorithm using Arnold transform and technique of singular value
Author(s):
Kang-lin Gao;
Mei Dong;
Feng-qi Zhou
Show Abstract
This paper presents a novel digital image information-hiding scheme that is based on digital image scrambling and matrix singular value. Firstly, this paper introduces methods to realize digital scrambling and the matrix singular value and presents new kinds of digital image information hiding schemes. In the scheme, scrambling technology is used as pre-process and post-process of digital image information hiding, and SVD is used to hide one image within another one. Secondly, the paper discusses how to use the scheme in the research area of digital image watermarking. The given examples show that the scheme can be easily realized and is secure for certain communication fields.
An edge extracting method of fuzzy thresholding value
Author(s):
Rui Gu;
Ming Zhu
Show Abstract
This paper discusses image's object edge extracting of threshold value. First, this paper introduces fundamental principle of gray image object edge extracting, after discussing the influence of object edge image's gray scale distributing characteristic and choice of threshold value to character extracting and target identification, we bring forward a sort of method, which using object edge fuzzy taxonomy and maximum fuzzy entropy theory to auto choose threshold value in the case that membership function is given, then we have a test of threshold value segmentation to edge gray image in different contrast, the result indicates this method has preferable scene adaptive faculty.
Variable window and variant threshold segmentation algorithm based on light field intensity
Author(s):
Ji-wen Cui;
Jiu-bin Tan;
Wen-jing Kang;
Lei Ao
Show Abstract
Image segmentation is a basic and key technology in image analysis and application. In order to avoid inaccurate segmentation non-homogeneous intensity in light field, a novel segmentation algorithm using variant threshold in variable window is proposed in this paper. In the algorithm, a special window for every point is selected according to special algorithm, and the grayscale of every point in the window is continued to the whole image. In the process of continuation, different weight is allocated to different point according to the weight function in the window by grayscale extremum's sum and difference. So, the grayscale of every point is monotonic in the special window, the variant threshold can be obtained in the selected window for its intensity in light filed, and the segmentation result can be acceptable. The experiment shows that the proposed segmentation algorithm can be used to correctly segment the image with non-homogeneous intensity in light field.
Optical image encryption based on cascaded iterative angular spectrum algorithm and its implementation with parallel hardware
Author(s):
Bin Yu;
Xiang Peng;
Jindong Tian;
Hanben Niu
Show Abstract
A cascaded iterative angular spectrum approach (CIASA) based on the methodology of virtual optics is presented for optical security applications. The technique encodes the target image into two different phase only masks (POM) using a concept of free-space angular spectrum propagation. The two phase-masks are designed and located in any two arbitrary planes interrelated through the free space propagation domain in order to implement the optical encryption or authenticity verification. And both phase masks can serve as enciphered texts. Compared with previous methods, the proposed algorithm employs an improved searching strategy: modifying the phase-distributions of both masks synchronously as well as enlarging the searching space. And with such a scheme, we make use of a high performance floating-point Digital Signal Processor (DSP) to accomplish a design of multiple-locks and multiple-keys optical image encryption system. An evaluation of the system performance is made and it is shown that the algorithm results in much faster convergence and better image quality for the recovered image. And two masks and system parameters can be used to design keys for image encryption, therefore the decrypted image can be obtained only when all these keys are under authorization. This key-assignment strategy may reduce the risk of being intruded and show a high security level. These characters may introduce a high level security that makes the encrypted image more difficult to be decrypted by an unauthorized person.
An efficient approach to segment man-made target from thermal image
Author(s):
Changjiang Zhang;
Xiadong Wang;
Haoran Zhang;
Huajun Feng
Show Abstract
A new fast algorithm to segment man-made target from infrared image is given employing Bezier histogram and edge information. In order to reduce computation burden, an efficient approach to select region of interest (ROI) is proposed based on prior-information. Thus a piece of region, which contains a target to be segmented, is extracted from original image. The gray level histogram of ROI is smoothed by Bezier curve to restrain noise in the ROI. Thus Bezier histogram is obtained. Peaks of curvature curve in the Bezier histogram are detected to obtained segmentation thresholds. An optimal segmentation threshold is selected with a new criterion. The optimal threshold segments the ROI well. In order to obtain better segmentation result, firstly a new algorithm, which bases on discrete stationary wavelet transform and non-linear gain operator is proposed to enhance the detail of target in the ROI. Canny operator is used to extract the edge information of target in the enhanced ROI. Finally, excellent segmentation result is obtained by combining Bezier histogram threshold method with edge information of target. Experimental results show that a man-made target can be segmented effectively from complex background in infrared image by the new algorithm.
Fourier transform profilometry based on a fringe pattern with two frequency components
Author(s):
Wenjing Chen;
Xianyu Su;
Yipping Cao;
Liqun Xiang;
Qican Zhang
Show Abstract
A modified Fourier transform profilomtry (FTP) based on a fringe pattern with two frequency components is proposed. We discuss its principle, analyze the maximum measuring range and give an expression to describe the measurable slope of the height variation limitation of this method. The modified FTP provides us another approach to eliminate frequency overlapping. When the spectra distribution of a measured object is not spherical symmetry, we can avoid the frequency aliasing through projecting a fringe pattern with two frequency components, instead of increasing the density of the projected fringe and the resolution of CCD camera. The theoretical analysis and primary experiments verified the method.
Study on Fourier transforms profilometry based on bi-color projecting
Author(s):
Wenjing Chen;
Xianyu Su;
Yiping Cao;
Qiancan Zhang;
Liqun Xiang
Show Abstract
We propose an improved FTP based on bi-color grating projecting. Two individual sinusoidal fringe patterns with π phase difference can be decoded from the deformed bi-color sinusoidal fringe pattern captured by color digital camera. Accessing the two fringe patterns, we can not only eliminate zero order spectra but also automatically build a binary mask at the same time to mark the valid measurement area easily, by which unwrapping phase time is shorten as well as phase error from invalid area is not transferred into valid area; Furthermore, we can easily expand the captured non-full-field deformed fringe pattern to form full field fringe pattern to guarantee frequency resolution.
Tomographic directional derivative of phase objects slices using 1-D derivative spatial filtering of fractional order ½
Author(s):
G. Rodríguez-Zurita;
C. Meneses-Fabián;
J.-S. Pérez-Huerta;
J.-F. Vázquez-Castillo
Show Abstract
Optical tomography of phase objects could be carried out with optical derivatives at the phase detecting stage. A particularly convenient related technique is the use of a fractional derivative of fractional order 1/2, which consists of a spatial filter with square-root amplitude transmittance. An advantage of this type of filter is that it can be implemented as a real filter when dealing with phase objects. Irradiance is proportional to the phase
derivative of order one, and it can be obtained. If a tomographic detection system is equiped with such a filter, phase gradient of projections can be determined, and directional derivatives of phase slices can be displayed. Slice images resulting from an experimental tomographic system for parallel projections includes a spatial
filter. with square-root amplitude transmittance made from a liquid crystal display operating in amplitude modulation are shown.
Iterative moire tomography and applications to measurements of temperature distribution
Author(s):
Bin Zhang;
Yang Song;
Anzhi He
Show Abstract
Moire tomography is applied in fully quantitative measurement of temperature distribution. Rotary moire deflectometer is designed to capture multidirectional optical projections, and moire patterns of temperature field can be obtained in 180 degrees. Then the temperature distribution of axisymmetric or asymmetric flow field is calculated by a new iterative reconstruction algorithm. The algorithm is derived from an existing moire deflection formula and based on an improved algebraic reconstruction technique. The method is demonstrated by reconstructing a temperature field generated above the top of two electric solding irons.
Computed tomography image measurement and analysis for dynamic configuration of polymer
Author(s):
Lifu Li;
Zengchang Wang
Show Abstract
The paper concentrates on the skills of tomography image processing and analysis for polymer configuration in polymer extrusion. Firstly, the tomography image segmentation is brought forward to resolve the problem that the amount of polymer information is small and the tomography image resolution is low, which comes from the great difference of physical dimension and material density between polymer (object) and processing equipment (background). And then, the object region extraction is performed to distinguish object region from segmentation image. Under the guidance of basic theory on polymer processing, the object configuration and its characteristics have been obtained by the tomography image measurement from the object region. The rheological property of polymer can be analyzed by the characteristics of object tomography configuration. Finally, the experiment result shows that this method can measure and analyze the polymer configuration and improve the measurement system resolution effectively. It has offered a novel experimental method to solve the problem that engineering material configuration in enclosed and complicated space is detested dynamically and nondestructively.
Reconstruction of two-temperature plasma flow by spectrum tomography
Author(s):
Yiqing Gao;
Yu Jin;
Xinmin Qi;
Jian Xing
Show Abstract
In this paper, a method, using the spectrum tomography combining with the principle of numerical calculation to rebuild two-temperature of plasma flow, is proposed. Heavy particle temperature of plasma flow is reconstructed based on numerical calculation and the electron temperature measured in experiment using the method. It is not the same as traditional one that reconstructs electron temperature and heavy particle temperature of plasma flow by calculating iteratively electron and heavy particle energy transfer equations with pure numerical simulation. The spatial distribution characteristics about electron temperature and heavy particle temperature of plasma flow and the factors that influence local-temperature equilibrium(LTE) are completely analyzed .In the diagnostic process, as is shown that the method omits multifarious boundary conditions and it is more feasible than that of pure numerical simulation for those plasma flows of which boundary conditions are difficult to confirm.
The theoretic model of the waveguide single-layer optical memory
Author(s):
Hanming Guo;
Xiangmei Dong;
Jiabi Chen;
Songlin Zhuang;
Zhongcheng Liang
Show Abstract
The waveguide multilayer optical memory is a novel and promising subject in the optical storage field compared with other 3D optical memory techniques. To our certain knowledge, how to establish the information scattering model of the single-layer waveguide optical memory is not found. In this paper, the Lippman-Schwinger equation and dyadic Green's function are used to compute an exact solution of the wave equation about the single-layer plane waveguide with information recorded. Then, the constructing method of the dyadic green function of the perfect plane waveguide with three layered structures is presented. Among the numerical calculations, a method about double integration of rapidly oscillatory function is introduced in detail. Based on the above method, the information scattering model of the waveguide single-layer optical memory will be constructed. According this theoretic model, with the computer simulation, the scattered light intensity distribution on the detector plane is showed. The scattering light intensity of the single information pit that is on behalf of information is also given.
Optical 3D shape measurement for vibrating drumhead
Author(s):
Xianyu Su;
Qican Zhang;
Jian Li;
Zeren Li
Show Abstract
In this paper, a whole-field and high-speed optical three-dimensional (3D) shape measurement for the vibration pattern of a drumhead based on Fourier Transform Profilometry (FTP) is presented and verified by experiment. A projected sinusoidal fringe pattern on the surface of measured drumhead is dynamically deformed with the vibration of the membrane and grabbed by a high-speed camera. The 3D shape deformation of the drumhead at each sampling instant can be recovered from demodulating the phase of this obtained sequence of fringe patterns. The vibration of the membrane of a Chinese drum has been measured with a high-speed sampling rate (1,000 fps) and a standard deviation (0.075 mm). This method should be helpful in studying the acoustic characteristic and the manufacture technique of the percussion instrument.
Displacement estimation by the phase-shiftings of Fourier transform in present white noise
Author(s):
Yuan-hao Wu;
Qian-yang Yu
Show Abstract
Displacement estimation is a fundamental problem in Real-time video image processing. It can be typically approached by theories based on features in spatial domain. This paper presents an algorithm which improves the theory for estimating the moving object's displacement in spatial domain by its Fourier transform frequency spectrum. Because of the characters of Fourier transform, the result is based on all the features in the image. Utilizing shift theorem of Fourier transform and auto-registration, the algorithm employs the phase spectrum difference in polar coordinate of two frame images sequence with the moving target.The method needn't transform frequency spectrum to spatial domain after calculation comparing with the traditional algorithm which has to search Direc peak, and it reduces processing time. Since the technique proposed uses all the image information, including all the white noise in the image especially, and it's hard to overcome the aliasing from noises, but the technique can be an effective way to analyze the result in little white noise by the different characters between high and low frequency bands. It can give the displacement of moving target within 1 pixel of accuracy. Experimental evidence of this performance is presented, and the mathematical reasons behind these characteristics are explained in depth. It is proved that the algorithm is fast and simple and can be used in image tracking and video image processing.
Measuring system on 3-D pose of the remote revolving target based on intersection measurement and its precision analysis
Author(s):
Qing-An Li;
Xiang-Rong Li;
Cui-Ping Liang;
Yan-Feng Qiao
Show Abstract
In this paper, a method of measuring the 3-D pose of the remote revolving target such as rocket or missile by using the intersected measuring system with a proper algorithm is described. This passage creates a math model of intersected measuring system with dual-photoelectric theodolite and the formula to calculate the target attitude angles are presented. The measuring precision of this method is analyzed in detail by using the relative error theory, and then it makes optimization design for structure parameters of intersected measuring system with dual-photoelectric theodolite by computer simulation, so different optimization results according to different location of target are obtained, and the system layout, measuring principles are also presented. By using this method we may acquire the measuring precision higher than 0.5o if the measuring stations are arranged correctly.
Fractal analysis of laser speckle for measuring roughness
Author(s):
Zhifang Li;
Hui Li;
Yishen Qiu
Show Abstract
Fractal geometry was applied to describe the laser-speckle pattern by the diffused laser light scattered reflectively from a metallic standard rough surface. The fractal dimension method with a gray scale was used in this presentation. The calculated results suggest that the fractal characteristics actually exist in the laser-speckle patterns. The fractal dimension and the lacunarity feature as well are related to the surface roughness and its style. In the same style, the fractal dimension decreases while the roughness increases. Conversely, the lacunarity increases along with the roughness increasing. On the other hand, as to the same roughness, the fractal dimension and the lacunarity feature are different to the different style, respectively. Therefore, the fractal dimension and the lacunarity feature can be used as new characteristic parameters to determine the roughness of surface. This fractal method can also be developed to be a non-invasive detection for optical property of scattering media such as biological tissue.
The security analysis and improved scheme of random phase encoding technique
Author(s):
Xu Wu;
Jiasheng Hu
Show Abstract
The robustness and security of random phase encoding technique are analyzed. We study the tolerance to data loss of the decrypting key for binary text and a grayscale image. To enhance the security, an improved phase coding scheme based on the chaos theory is proposed. The proposed optical setups for image decryption are depicted. The analyses show that the improved scheme can effectively improved the security.
Secure optical communication system based on tunable fiber Bragg grating arrays
Author(s):
Hailei Xu;
Jinfang Zhou;
Menghu Cao;
Kangsheng Chen
Show Abstract
Superstructured fiber Bragg grating (FBG) technology has emerged as an attractive means to produce compact, and potentially low-cost in-fiber devices for a variety of lightwave applications. In this paper, a secure optical communication system based on tunable FBG arrays is described. Utilizing the inherent characteristics of FBG array to decompose broadband pulses simultaneously in wavelength and time, one broadband light pulse reaching a series of different Bragg gratings may be split into a number of separated pulses, each with different wavelength and is positioned at different time. To recover the original pulse, an inverted grating array is needed at the receiver side, i.e., the transmission is secure in case that the exact structure of the FBG array is unknown. Some of the factors affecting the process of encryption/decryption are indicated. To further increase the security of the system, theories about bent functions are presented and applied to generate bent sequences so as to charge the modes of FBG arrays because of the bent functions' excellent cryptographic properties. Simulations results are presented and analyzed to show the feasibility of the system. The paper is concluded with a discussion of the advantages for such an optical encryption/decryption system.
Digital speckle correlation method improved by hybrid method
Author(s):
CanLin Zhou;
Fang Li;
YiLan Kang;
FuSheng Yu
Show Abstract
Digital Speckle correlation method (DSCM) is a computer-vision- based, non-contact, whole-field surface strain measuring method. It is becoming increasingly important as experimental mechanics tool. Its working principle is to compare one digital image of the displaced/deformed surface with the original one using a mathematically well-defined correlation function based on some subset of pixels. In the evolution of DSCM, several methods and techniques have been developed to raise the search speed and precision of DSCM. Typical methods include the coarse-fine search, Newton-Raphson and quasi-Newton method based on optimization theory. However, the coarse-fine search method considers only the rigid body translation displacement, New-Raphson and quasi-Newton is sensitive to the initial values and local extremum. It is possible for Quasi-Newton method to find a local extremum instead of global extremum, even impossible to obtain the extremum because bad initial estimate in iterative computation leads to divergence. The genetic algorithm can be used to optimize the subset correlation globally. But it has large computational workload if it is applied to complete all search procedures for whole speckle pattern. Its convergence velocity becomes the slower and slower along with searching near optimum solution. We present an improved DSCM by hybrid method, which combines the genetic algorithm, quasi-Newton with adjacent point initial estimate. Genetic algorithm is used to obtain the initial estimate for Quasi-Newton iterative method, which be performed only in preliminary search window. Initial estimate for the succedent search subset is obtained by corresponding adjacent point. The simulation experiments have proved the efficiency of the new method.
Multi-photon free-space quantum key distribution system with synchronously delayed classical signals
Author(s):
Li Yang;
Lei Hu;
Songhou Liu
Show Abstract
We present a multi-photon scheme to improve the efficiency of free-space quantum key distribution system. Two essential features of free-space quantum key distribution system are its classical timing pulses and frequency tracking devices, we make use of these two features to design a new type of quantum key distribution system with multi-photon quantum signals and synchronously delayed classical signals. This scheme is much more efficient then the usual one, and in the same time, more secure since its synchronously randomizing of frequency and arriving time of quantum signals makes Eves have almost no opportunity to catch the quantum signals in time.
Fabry-Perot etalon filter
Author(s):
Qing-mei Wang;
Yi-mo Zhang;
Wei-Hui Liu
Show Abstract
The Fabry-Perot etalon is usually used for dispersing light in the receiver of the Fringe Technique Doppler Lidar for its high precision of analyzing optical spectrum. However, the paper describes a new method that a Fabry-Perot etalon combined with an aperture diaphragm can be used as a narrow-band filter of transmitted laser beam. Only when incidence of light is perpendicular to the plates of the F-P etalon, a whole number of wavelengths fits into one round trip of the cavity mλ=2d and the period of frequency Δv=k.c/(2d) or the period of wavelength Δλ=k.λ2/(2d) is k times FSR of the etalon, the spectrum can be transmitted through the filter. When these spectrum enter the F-P etalon again, the mth interference circular fringes of λ coincide with the (m∓k)th
interference circular fringes of λ∓kΔλ on the focus plane of convergent lens. Comparing the circular fringes of laser beam filtered with those of unfiltered, experiment shows that quality of light beam filtered is improved obviously. So this
technique could be useful for sensing atmospheric wind velocity.
A recursive two-circuits series analog fractance circuit for any order fractional calculus
Author(s):
Yifei Pu;
Xiao Yuan;
Ke Liao;
Jiliu Zhou;
Ni Zhang;
Xiaoxian Pu;
Yi Zeng
Show Abstract
The paper analyzes the fractional calculus's Caputo definition in time domain and Fourier transform's definition in frequency domain, then puts forward and discusses a 1/2order two-circuits series analog fractance circuit. On this bases, we further put forward and discusses a general recursive two-circuits series analog fractance circuit for any order fractional calculus. It is proved to performance correctly and efficiently by Computer simulation and circuit analog. At the same time, we probes the theoretical and engineering problems that need to be deeply researched in the area of the applications of fractional calculus to communication and information processing. The result educing by the paper is the basis for further theoretic research and engineering implement for structuring fractance circuit of any order fractional calculus.
Using one-dimensional nonlinear photonic crystal for dynamical addressing optical interconnection
Author(s):
Ming Chen;
Chunfei Li;
Mai Xu;
Weibiao Wang;
Shaojie Ma;
Yuxue Xia;
Song Chen;
Dali Liu
Show Abstract
Optical interconnection is the key technique of high-speed optical information process and optical communication. A lot of approaches for optical interconnection have been proposed since Goodman in Stanford University firstly proposed the optical interconnection for very large scale integrated circuits technology. A dynamical addressing device for optical interconnection was designed and fabricated in this paper. This optical device is based on one-dimensional nonlinear photonic crystal made on the planar waveguide. The nonlinear materials ZnS and ZnSe, which have large nonlinear refractive index coefficients, were alternately deposited on the waveguide to form one-dimensional photonic crystal. The Bragg condition is changed when the input power of the control light increased due to the nonlinear characters of the materials, thus the reflective angle of the signal light can be changed with the input power change of the control light. In our experiment, when increasing the power density of control light from 0 to 2.60X105W/cm2, the angle of the signal beam can be changed about 2o. The interconnection characteristics were investigated in theory and in experiment. The testing data agree well with theoretical predictions. This kind of devices is promising to use in the all-optical interconnection, optical information processing and optical communication
A novel high-speed magneto-optic switch design and analysis
Author(s):
Yun Zhu;
Zihua Weng;
Yuanqing Huang;
Zhimin Chen
Show Abstract
A novel type of 2×2 polarization independent magneto-optic switch with low Insertion Loss, nanosecond order switching time is designed and analyzed. The study of the magneto-optic switch involves two main parts: Faraday rotator assembly and optical route design. In faraday rotator design, magneto-optic crystal comparison and selection, two types of Faraday rotator assembly schemes design and analysis; high speed magnetic field simulation and generation; nanosecond trigger signal generator design, simulation and experiment are involved. Within optical router design, a simple but effective optical router with 2×2 mode is introduced. The nanosecond trigger signal supply to the Faraday rotator assembly is 12ns. The key characteristics, insertion loss, far-end crosstalk, switching time of magneto-optic switch that developed at a wavelength of 1550nm have been tested and root causes analyzed.
The effect on Doppler frequency shift by measurement prism 3-dimension motion
Author(s):
Zhi Zhong;
Jiubin Tan;
Hongfang Chen;
Hongwen Ma
Show Abstract
Displacement measurement with laser interferometer is based on measuring the laser Doppler frequency shift that a beam of radiation undergoes upon reflection from measuring prism connected to a moving stage. The principle error in fast ultra-precision laser heterodyne interferometric measurement is proposed in this paper. Only 1-dimension motion of the measuring prism is usually thought about in the laser Doppler frequency shift calculation. The formula of laser Doppler frequency shift taken in account of 3-dimension motion of measurement prism is established, and the error introduced by the velocity of other dimensions is analyzed. There is a lack of the second-order in v/c in traditional model of displacement measurement with laser heterodyne interferometric. The distance error lead by the second-order in v/c in Doppler frequency is analyzed and emulated, the emulation result shows that there is a residual cumulative error that is up to 17.7nm when the highest speed is up to 1m/s and the displacement is long to 3m. The residual cumulative error is cumulatived.
Impact and compensation of PMD on the performances of optical switching with NOLM
Author(s):
Minghui Yuan;
Mingde Zhang;
Xiaohan Sun
Show Abstract
The impact of the first-order and second-order PMD on the performances of optical switching with NOLM is studied by the split-step Fourier method (SSFM) based on the coupled nonlinear Schrodinger equation (CNLSE), including optical eye graphs, power transmission function of the NRZ code and the Q-factor penalty of different code patterns at different working speeds. The simulation results show that the switching performances are deteriorated badly by PMD, and using the right code pattern can reduce the impact of PMD partially. Furthermore, the compensation method of PMD by the polarization-maintaining fiber (PMF) inside the fiber loop of NOLM is put forward. It influences the original switching performances to the least extent when the PMF is located in the middle of the fiber loop.
Study of Mie extinction efficiency
Author(s):
Guang-hui Dai;
Zhi-bin Ren;
Qiang Sun;
Jian Liu
Show Abstract
This Paper analyzes the mathematical character of the extinction efficiency (normalized extinction cross section) and studies the numerical computation of it. The paper discusses the relations of the extinction efficiency and the size parameter x and the relations of the peak value of the ripple structure of the extinction efficiency and the amplitude of Mie scattering an(x, m), bn(x, m). The paper also discusses the relations of the approximate periodicity of the ripple structure and relative refractive indices m. The result shows that relation curve of the extinction efficiency and the size parameter x has ripple structure, which become faint as x is large; when the relative indices m is real and m<=2, the ripple structure has single periodicity, and positions of the peak values of the ripple structure are corresponding to the positions of peak values of Re[an(x, m)]and Re[bn(x, m)]. When m is complex and Im(m)<0.01, the ripple structure also has the same periodicity, however, the oscillation amplitude of the ripple structure becomes weaker. The larger Im(m) is, the weaker the oscillation amplitude of the ripple structure is.
Photonic DNA computing: concept and implementation
Author(s):
Jun Tanida;
Yusuke Ogura;
Seiji Saito
Show Abstract
As a novel computing paradigm extended from conventional methods in optical computing, photonic DNA (deoxyribonucleic acid) computing has been proposed. Photonic DNA computing merges two interesting computational frameworks, i.e., optical computing and DNA computing, to explore a new field of computing technology. Complementary combination of optical techniques and molecular processing is expected to provide a new generation of computing paradigm for massively parallel and high performance computing. In this paper, the concept of photonic DNA computing is introduced and the current status of research activities is presented.
Fast hologram calculation for holographic video display
Author(s):
Hiroshi Yoshikawa;
Takeshi Yamaguchi
Show Abstract
For practical holographic video system, it is important to generated holographic fringe as fast as possible. We have proposed an approximation method that can calculate the Fresnel hologram fast. With the proposed method, a hologram with more than one million pixels can be calculated less than one second with a personal computer. To compute the hologram, an object is assumed as a collection of self-illuminated points and the fringes from each object point are superposed. To determine the fringe, a distance between object point and sampling point on the hologram is used to obtain phase of the light. Since sampled hologram usually has small pixel intervals, the difference of the distance values between adjacent pixels is also small and its second order difference becomes a constant. Therefore, the distance value at certain pixel can be obtained from the neighbor pixel with simple additions. The experimental results show that the proposed method is quite effective for the holographic video display with full parallax.
Whole-field analysis of polarization state by digital holography with a fiber Faraday rotator
Author(s):
Masayuki Yokota;
Yoshitaka Terui;
Ichirou Yamaguchi
Show Abstract
Digital holographic technique has been applied to analyze the distribution of polarization state of transmitted light at the object surface by use of orthogonally polarized reference beam produced by a flint glass fiber Faraday rotator. The object composed of a glass plate and a layered sellophane tape is employed and the polarization distribution over the object surface is analyzed. It is shown that the proposed system can be applied for the whole field analysis of polarization state.
Detecting small phase modulation using photorefractive reflection hologram
Author(s):
Roman V. Romashko;
Yuri N. Kulchin;
Alexei A. Kamshilin
Show Abstract
Theoretical and experimental studying of the vectorial wave mixing in the photorefractive crystal in the reflection geometry without applying an external electric field is presented. We demonstrate that small phase modulation of the object wave is linearly transferred into the intensity modulation of the output beam without any auxiliary polarization element but just mixing light waves with different polarization states (e.g., elliptical and linear). Geometry in which anisotropic diffraction occurs was chosen. The linear phase demodulation occurs because the inherent π/2 phase difference between orthogonal components of elliptically polarized wave is transferred into the interference term of the transmitted object and diffracted reference waves.
Gaussian apodized volume grating for a holographic demultiplexer
Author(s):
Duc Dung Do;
Nam Kim;
Kwon Yeon Lee
Show Abstract
In this paper, a fabrication of Gaussian apodized volume gratings for a holographic demultiplexer is presented. The DuPont HRF-150-38 photopolymer is used because of its stability and ease of use. Based on the Gaussian apodized grating, a 42-channel demultiplexer is optically demonstrated. The interchannel spacing, the interchannel cross-talk level and the channel uniformity of 0.4 nm, -30 dB and 1.5 dB, respectively, are obtained.
Iterative reconstruction of wave front from an in-line hologram sequence
Author(s):
Yan Zhang;
De-Xiang Zheng;
Jing-Ling Sheng;
Cun-Lin Zhang;
Giancarlo Pedrini
Show Abstract
Digital holography is a powerful imaging technology in which the reconstruction processing is accomplished via a computer and no wet processing is required. Therefore, it can obtain the image of an object in real time. Furthermore, both the amplitude and phase information of a wave front can be obtained simultaneously. In-line digital holography can effectively utilize the spatial-bandwidth product of the digital recorder, such as CCD or CMOS. Reconstruction algorithms allow a continuous development and expand the applications of the digital holography. In this presentation, a novel method will be presented for reconstruction of wave front from a series of in-line holograms. After determining the phase and amplitude distribution of the wave front at a given plane, the original object can be reconstructed via the inverse propagation. Due to no reference wave is required in this approach, the optical setup is relatively simplified, the size of the recording object can be enlarged, and the signal-noise-ratio of the system can be improved. The simulation results based on the Fresnel transform are presented to demonstrate the validity of this new approach. The image reconstructed from experimentally recorded holograms by using the Rayleigh-Sommerfeld approximation corresponds to the original object well.
A new kind of storage hierarchy-volume holographic universal storage cache
Author(s):
Dongjian Luo;
Changsheng Xie;
Dezhi Han;
Jianzhong Huang;
Chengfeng Zhang
Show Abstract
The access time of Disk/RAID has not been improved as fast as the memory performance whose rate of improvement has been 25% per year and hence the disk access penalty is considerably increasing with each enhancement in the memory architecture. To solve the problem, a new kind of storage hierarchy, Volume Holographic Universal Storage Cache (short for VHUSC) is proposed. VHUSC acts as a layer between main memory and disk or disk array. VHUSC can lower the disk access latency, provide much higher I/O bandwidth and throughput, it thus greatly improve the I/O performance of computer system. In this paper, an application independent model based on queuing theory is proposed for the VHUSC performance evaluation. Based on this model, VHUSC and traditional disk/RAID performance is analyzed and compared. Result shows that in most cases VHUSC can improve the disk read/write performance by 1 order of magnitude, especially when the hit rate is larger than 99%, the performance can reach 2 orders of magnitude.
Optimization of holographic diffractive optical element used for fabricating photonic crystals
Author(s):
Ying Liu;
Shou Liu;
Xiangsu Zhang;
Xuechang Ren;
Sensen Li
Show Abstract
A technique for fabricating optimized holographic diffractive optical element (HDOE) used for fabricating photonic crystals is proposed in this paper. The HDOE consists of three identical transmission gratings symmetrically placed around the center with 120° between each other. Usually the polarization of the diffracted beam of a grating will be changed from that of the incident beam depending on the orientation of the grating. As the orientations of the three gratings in a HDOE are different, the polarizations of the diffracted beams and their diffraction efficiencies are different, resulting in low contrast of the interference pattern. This problem can be solved by controlling the parameters in grating fabrication. Rigorous coupled-wave analysis is used to calculate the influence of grating depth and polarization angle on diffraction efficiency and polarization of diffracted beams. Calculated results demonstrate that under 458 nm illumination, if the three sinusoidal gratings in a HDOE have 0.729 μm period and 0.33 μm depth, the polarization and diffraction efficiencies of the three first-order diffracted beams will be equal. The experimental results are presented to prove the practicability of the technique.
Study on influence of vibration behavior of composite material damage by holography
Author(s):
Linfeng Guo;
Zhimin Zhao;
Mingjuan Gao;
Xianzhong Zhuang
Show Abstract
Composite material has been applied widely in aeronautics, astronautics and some other fields due to their high strength, light weight and antifatigue and etc. But in the application, composite material may be destroyed or damaged, which may have impact on its further applications. Therefore, study on the influence of behavior of composite material damage becomes a hot research. In this paper, the common composite material for aircraft is used as the test object, and a study is conducted to investigate the influence of vibration behavior of composite material damage. The authors adopt the method of light-carrier wave and time-average holography. Compared the interference fringes of composite materials before and after damage, the width of the interference fringes of hologram of the damaged composite material is narrower than that of the fringes before. It means that the off-plane displacement of each point on the test object is larger than before. Based on the elastic mechanics theory, the off-plane displacement is inverse to the bending stiffness, and the bending stiffness of the test object will decrease after it is damaged. In other words, the vibration property of the composite material changes after damages occur. The research results of the paper show that the results accord with the analysis of theory.
Optical characteristics of an organic-inorganic hybrid photopolymer film for holographic storage and optical application
Author(s):
Changwon Shin;
Nam Kim;
Eunkyoung Kim;
Jiyoung Park;
Sangkeun Gil
Show Abstract
Monomer diffusion in an organic-inorganic nanocomposite films during the holographic recording was investigated. The photopolymer films with low shrinkage were prepared by dispersing an aromatic methacrylic monomer and a photo-initiator in organic-inorganic hybrid sol-gel matrices. The shrinkage of the photopolymer film and the diffusion of monomers during the holographic recording could be controlled by optimizing the content of an organically modified silica precursor (ORMOSIL) in the sol-gel matrices. The photopolymer film showed high diffraction efficiency (>90%) under an optimized condition. Photo-sensitivity, angular selectivity and application potential for holographic data storage and optical application will be discussed.
Phase-shifting real-time holography with photorefractive crystals
Author(s):
M. R. R. Gesualdi;
D. Soga;
M. Muramatsu
Show Abstract
The phase-shifting interferometry techniques is a well-known technique which has been used with great success in optical profilers, micro-displacements, micro-deformations and others applications in Non-Destructive Test in basic research, engineering and biotechnology areas. This work presents our Advances in Phase-Shifting Real-Time Holography using Photorefractive Sillenite. And we have obtained quantitative results in many applications in measurements of micro-rotation, micro-displacements, deformation, surface contouring and whole lens wave-optics. The real-time holography process is doing using the photorefractive Bi12SiO20 crystal recording medium, where the phase-shifting 4-frames method for obtained the phase map, this was filtered by sin/cos filter and was applied the unwrapping process. The experimental results agree with the expected one in these applications and with promises potentialities of this method for studies with in situ visualization, monitoring and analysis.
Resolution power in digital in-line holography
Author(s):
J. Garcia-Sucerquia;
W. Xu;
S. K. Jericho;
M. H. Jericho;
P. Klages;
H. J. Kreuzer
Show Abstract
Digital in-line holographic microscopy (DIHM) can achieve wavelength resolution both laterally and in depth with the simple optical setup consisting of a laser illuminating a wavelength-sized pinhole and a CCD camera for recording the hologram. The reconstruction is done numerically on the basis of the Kirchhoff-Helmholtz transform which yields a three-dimensional image of the objects throughout the sample volume.
Resolution in DIHM depends on several controllable factors or parameters: (1) pinhole size controlling spatial coherence, (2) numerical aperture given by the size and positioning of the recording CCD chip, (3) pixel density and dynamic range controlling fringe resolution and noise level in the hologram and (4) wavelength. We present a detailed study of the individual and combined effects of these factors by doing an analytical analysis coupled with numerical simulations of holograms and their reconstruction. The result of this analysis is a set of criteria, also in the form of graphs, which can be used for the optimum design of the DIHM setup. We will also present a series of experimental results that test and confirm our theoretical analysis. The ultimate resolution to date is the imaging of the motion of submicron spheres and bacteria, a few microns apart, with speeds of hundreds of microns per second.
Resolution, focus depth in the Fresnel-Fraunhofer domains
Author(s):
Francisco F. Medina;
Roman Castaneda;
Jorge Garcia-Sucerquia
Show Abstract
Defocused imaging can be analyzed as Fresnel diffraction. The defocus parameter, that characterizes this imaging, is related to an effective Fresnel number, which is induced by the geometry of the imaging set-up. From this point of view, perfectly focused images result from Fraunhofer diffraction. Therefore, the same criteria for distinguishing between Fraunhofer and Fresnel diffraction can be applied to determine if the image is or not focused. As a consequence, new definitions of the focus depth can be deduced. In addition, resolution of two point-objects under different states of spatial coherence and focus conditions is discussed and some resolution criteria are deduced. Then, they are compared to the classical resolution criteria, which are considered as applicable to the extreme cases of fully spatial coherence and fully spatial incoherence. Some classical examples, such as, imaging of one point object and two near point objects, are discussed to illustrate the analysis.
The influence of photovoltaic dc field on holographic correlation recognition
Author(s):
Guodong Liu;
Jianmin Wang;
Yunbo Guo;
Shengqian Wang
Show Abstract
The optical correlation technique based on volume holographic storage has a more obvious advantage on rapid processing, for the input image to be compared is computed with all stored templates simultaneously. Thus it is promising in application for pattern recognition, content addressing and associative recall. As the continuing progress in volume holographic storage, the volume holographic optical correlation technique will draw more and more attention. The volume holographic correlators always use Fe:LiNbO3 as their storage materials, in which a nonuniform photovoltaic field was created during hologram recording exposure. As we have discussed before, the field not only reduced the dynamic range of the crystal, but also degraded the volume holograms. Furthermore, the field debases the recognition rate. In this paper, we analyze the influence of the field on holographic correlation recognition according to theories and experiments. A sodium chloride solution is used to short-circuit the crystal and suppress the influence of the photovoltaic dc field. 1000 holograms, which have been stored in a common volume of the crystal placed in the sodium chloride solution, have been reorganized with the rate of more than 84%.
Multi-wavelength holographic profilometry
Author(s):
E. A. Barbosa;
M. R. Gesualdi;
M. Muramatsu
Show Abstract
A novel method for surface profilometry by holography is presented. We used a diode laser emitting at many wavelengths simultaneously as the light source and a Bi12TiO20 (BTO) crystal as the holographic medium in single exposure processes. The employ of multi-wavelength, large free spectral range (FSR) lasers leads to holographic images covered of interference fringes corresponding to the contour lines of the studied surface. In order to obtain the relief of the studied surface, the fringe analysis was performed by the phase stepping technique (PST) and the phase unwrapping was carried out by the Cellular-automata method. We analysed the relief of a tilted flat metallic bar and a tooth prosthesis.
A novel starting-point-independent wavelet coefficient shape matching
Author(s):
Shuo Hu;
Ming Zhu;
Chuan Wu;
Hua-jun Song
Show Abstract
In many computer vision tasks, in order to improve the accuracy and robustness to the noise, wavelet analysis is preferred for the natural multi-resolution property. However, the wavelet representation suffers from the dependency of the starting point of the sampled contour. For overcoming the problem that the wavelet representation depends on the starting point of the sampled contour, the Zernike moments are introduced, and a novel Starting-Point-Independent wavelet coefficient shape matching algorithm is presented. The proposed matching algorithm firstly gains the object contours, and give the translation and scale invariant object shape representation. The object shape representation is converted to the dyadic wavelet representation by the wavelet transform. And then calculate the Zernike moments of wavelet representation in different scales. With respect to property of rotation invariant of Zernike moments, consider the Zernike moments as the feature vector to calculate the dissimilarity between the object and template image, which overcoming the problem of dependency of starting point. The experimental results have proved the proposed algorithm to be efficient, precise, and robust.
A new sub-pixel detector for grid target points in camera calibration
Author(s):
D. Chen;
Y. Wang;
G. Zhang
Show Abstract
Sub-pixel detection of target points is an important task in camera calibration. Grid target points are widely used in camera calibration for their junctions can be easily detected. Traditional method detects the sub-pixel position of grid-point by calculating the intersection of two beelines fitted by centers of grid-lines. Generally, this method yields low precision because of the effect of projective distortion of camera lens. In this paper, we propose a new sub-pixel detector for grid target points. We firstly use a new shape operator based on Hessian matrix to detect the pixel position of grid-point. Then the intensity of sub-pixel points in the neighborhood of grid point is calculated by cubic interpolation. A minimum restriction for searching grid-point is deduced by the fact that the grid-point to be detected is just the extremal point of local intensity profile. According to this restriction, the sub-pixel position of grid-point is finally determined by a graded morphological shrinking operation. Computer simulation results indicate that our new algorithm is more accurate and robust than the traditional algorithm.
A segment detection method based on improved Hough transform
Author(s):
Qiu-lei Han;
Miing Zhu;
Zhi-jun Yao
Show Abstract
Hough transform is recognized as a powerful tool in shape analysis which gives good results even in the presence of noise and the disconnection of edge. However, traditional Hough transform can only detect the lines, cannot give the endpoints and length of the line segments and it is vulnerable to the quantization errors. Based on the analysis of its limitations, Hough transform has been improved in order to detect line segment feature of targets. The algorithm aims to avoid the loss of spatial information, as well as to eliminate the spurious peaks and fix on the line segments endpoints accurately, which can expediently be used for the description and classification of regular objects. The method consists of 6 steps: 1. setting up the image, parameter and line-segment spaces; 2. quantizing the parameter space; 3. applying the standard Hough transform equation to every point of the input image edge, and extracting a group of maximums according to the global threshold; 4. according to the local threshold, eliminating spurious peaks which are caused by the spreading effects; 5. fixing on the endpoints of the segments according to the dynamic clustering rule; 6. merging the segments whose extreme points are near. Experiment results show the approach not only can recognize regular geometric object but also can extract the segment feature of real targets in complex environment. So the proposed method can be used in the target detection of complicated scenes, and will improve the precision of tracking.
High-accuracy real-time automatic thresholding for centroid tracker
Author(s):
Ye Zhang;
Yanjie Wang
Show Abstract
Many of the video image trackers today use the centroid as the tracking point. In engineering, a target's centroid is computed from a binary image to reduce the processing time. Hence thresholding of gray level image to binary image is a decisive step in centroid tracking. How to choose the feat thresholds in clutter is still an intractability problem unsolved today. This paper introduces a high-accuracy real-time automatic thresholding method for centroid tracker. It works well for variety types of target tracking in clutter. The core of this method is to get the entire information contained in the histogram, such as the number of the peaks, their height, position and other properties in the histogram. Combine with this histogram analysis; we can get several key pairs of peaks which can include the target and the background around it and use the method of Otsu to get intensity thresholds from them. According to the thresholds, we can gain the binary image and get the centroid from it. To track the target, the paper also suggests subjoining an eyeshot-window, just like our eyes focus on a target, we will not miss it unless it is out of our eyeshot, the impression will help us to extract the target in clutter and track it and we will wait its emergence since it has been covered. To obtain the impression, the paper offers a idea comes from the method of Snakes; it give a great help for us to get a glancing size, so that we can compare the size of the object in the current frame with the former. If the change is little, we consider the object has been tracked well. Otherwise, if the change is bigger than usual, we should analyze the inflection in the histogram to find out what happened to the object. In general, what we have to do is turning the analysis into codes for the tracker to determine a feat threshold. The paper will show the steps in detail. The paper also discusses the hardware architecture which can meet the speed requirement.
Target track system design based on circular projection
Author(s):
Hua-Jun Song;
Ming Zhu;
Shuo Hu;
Mei-Li Shen
Show Abstract
Template matching is the process of searching the present and the location of a reference image or an object in a scene image. Template matching is a classical problem in a scene analysis: given a reference image of an object, decide whether that object exists in a scene image under analysis, and find its location if it does. The template matching process involves cross-correlating the template with the scene image and computing a measure of similarity between
them to determine the displacement. The conventional matching method used the spatial cross-correlation process which is computationally expensive. Some algorithms are proposed for this speed problem, such as pyramid algorithm, but it still can't reach the real-time for bigger model image. Moreover, the cross-correlation algorithm can't be effective when the object in the image is rotated. Therefore, the conventional algorithms can't be used for practical purpose. In
this paper, an algorithm for a rotation invariant template matching method based on different value circular projection target tracking algorithm is proposed. This algorithm projects the model image as circular and gets the radius and the sum of the same radius pixel value. The sum of the same radius pixel value is invariable for the same image and the any rotated angle image. Therefore, this algorithm has the rotation invariant property. In order to improve the matching speed and get the illumination invariance, the different value method is combined with circular projection algorithm. This method computes the different value between model image radius pixel sum and the scene image radius pixel sum so that it gets the matching result. The pyramid algorithm also is been applied in order to improve the matching speed. The high speed hardware system also is been design in order to meet the real time requirement of target tracking system. The results show that this system has the good rotate invariance and real-time property.
Multiwavelet based multispectral image fusion for corona detection
Author(s):
Xin Wang;
Feng Yan;
Yong-xin Sui;
Huai-jiang Yang;
Yun-jie Pang
Show Abstract
Image fusion refers to the integration of complementary information provided by various sensors such that the new images are more useful for human or machine perception. Multiwavelet transform has simultaneous orthogonality, symmetry, compact support, and vanishing moment, which are not possible with scalar wavelet transform. Multiwavelet analysis can offer more precise image analysis than wavelet multiresolution analysis. In this paper, a new image fusion algorithm based on discrete multiwavelet transform (DMWT) to fuse the dual-spectral images generated from the corona detection system is presented. The dual-spectrum detection system is used to detect the corona and indicate its exact location. The system combines a solar-blind UV ICCD with a visible camera, where the UV image is useful for detecting UV emission from corona and the visible image shows the position of the corona. The developed fusion algorithm is proposed considering the feature of the UV and visible images adequately. The source images are performed at the pixel level. First, a decomposition step is taken with the DMWT. After the decomposition step, a pyramid for each source image in each level can be obtained. Then, an optimized coefficient fusion rule consisting of activity level measurement, coefficient combining and consistency verification is used to acquire the fused coefficients. This process reduces the impulse noise of UV image. Finally, a new fused image is obtained by reconstructing the fused coefficients using inverse DMWT. This image fusion algorithm has been applied to process the multispectral UV/visible images. Experimental results show that the proposed method outperforms the discrete wavelet transform based approach.
Research on application of several tracking detectors in APT system
Author(s):
Zhi Liu
Show Abstract
APT system is the key technology in free space optical communication system, and acquisition and tracking detector is the key component in PAT system. There are several candidate detectors that can be used in PAT system, such as CCD, QAPD and CMOS Imager etc. The characteristics of these detectors are quite different, ie the structures and the working schemes. This paper gives thoroughly compare of the usage and working principle of CCD and CMOS imager, and discuss the key parameters like tracking error, noise analyses, power analyses etc. Conclusion is given at the end of this paper that CMOS imager is a good candidate detector for PAT system in free space optical communication system.
Restoration of moving blurred image based on TMS320C6416
Author(s):
Wei Liu;
Ming Zhu;
Xiang-rong Li
Show Abstract
To absolve image blur caused by camera's high speed, fixed-point DSP TMS320C6416 and wiener filtering algorithm are adopted to stabilize image. On the premise that cameras have uniform motion, restoration model for moving blurred image was researched, the principle of Wiener filtering is explained, the key technologies of moving blurred image restoration with TMS320C6416 are introduced: how to complete FFT calculation of 32bit and how to exert DMA function of DSP to enhance processing speed, ring effect and ghost effect in restored image are explained, and how the parameter λ of wiener filter affects ring effect and ghost effect is discussed, in addition to this, other reasons of ring effect and ghost effect are analyzed detailed. Experiments shows that One TMS320C6416 chip can restore seven frames per second, there is great hope to realize real-time restoration if adopting multi-DSP or the FFT completion by hardware.
Image mosaics system based on TMS320DM642
Author(s):
Gui-Lan Feng;
Wei-Jian Tian;
You-Shan Qu;
Wei Ge
Show Abstract
When the size of a needing scene is beyond the scope of an optical sensor, it is difficult to take the whole scene at the same time. In this case, the needing scene can be captured by several optical sensors at one time, the overlapped images can be taken. Using the images, the whole scene is reproduced. This paper presents a robust image mosaics method that employs wavelet transform technique. The new developed registration and fusion algorithm implemented automatically and simultaneously without known camera motion and focal length. Wavelet transform guarantees not only a global optimal solution, but also scale and transform invariance for image alignment. This feature guarantees that the scheme has higher performance than the traditional mosaic techniques. In the same time, the hardware structure and the software designing principle of the Image Mosaics System (IMS) based on the Digital Signal Processor are expounded. To further improve the image mosaics quality, an image enhancement approach is also employed. In the paper, the concept, algorithm and experiments are described. The test results showed that the IMS is efficient and accurate for acquisition of seamless mosaic of the overlapped images, and at the same time, is adaptive to the real-time requirements. An adaptive resolution, seamless and a wide field of view image can be acquired.
An alternative method on camera calibration with one-dimensional objects
Author(s):
Nian Wang;
Yi-Zheng Fan;
Wen-xia Bao;
Dong Liang;
Sui Wei
Show Abstract
Camera calibration is a necessary step in 3D computer vision in order to extract metric information from 2D images. In this paper, using the homography between a plane in the scene and the plane of an image, we propose an alternative method on camera calibration with one-dimensional objects, and give both a linear and nonlinear solutions for the camera intrinsic parameters. Experimental results show that our approach also has a high accuracy.
The research on image enhancement of low-quality fingerprint image
Author(s):
Bo Li
Show Abstract
Fingerprint Identification is one of the most reliable and popular personal identification methods. It can be divided into image acquisition, enhancement, feature extraction and matching steps. The enhancement stage is of great importance as it influences the performance of subsequent feature extraction and matching. In this paper, different image enhancement approaches presented in the scientific literature are reviewed. Many fingerprint enhancement algorithms were effective for medium or high quality fingerprint images. But these existing algorithms were either not suited for low quality fingerprint images, or too slow to satisfy the real-time requirements. We proposed a fingerprint enhancement algorithm based on Fourier filtering. In our algorithm the fingerprint enhancement were transformed from spatial domain to frequency domain by Fourier transforming. The fingerprints were enhanced by band-pass filter and directional filter in frequency domain. Experimental results show our algorithm is fast and has excellent enhancing performance for low quality fingerprints. In addition, Enhancement for non-minutiae based fingerprint recognition for low quality images is presented. the pre-processing stage operating on a hexagonal grid can be implemented efficiently and gives promising results. Methods of comparing the performance of enhancement methods are discussed. Conclusions are made regarding the importance of effective enhancement, especially for noisy or low quality images.
Recognition study for gray image based on optoelectronic hybrid joint transform correlator
Author(s):
Hongxia Wang;
Junhong Zhao;
Zhaoxuan Sheng
Show Abstract
In this paper a kind of optoelectronic hybrid joint transform correlator for recognition of gray images has been proposed. In order to remove low frequency components, the input gray image is preprocessed by edge enhancement using the Gauss-Laplace algorithm. The joint transform power spectrum of object and referenced image is obtained by Fourier transform with optical apparatus. The power spectrum is captured by CCD and input into computer for process. First, the joint power spectrum is modified by subtracted the power spectrum of the object image and of the reference image being only respectively. The subtracted power spectrum is filtered by Butterworth high-pass filter to further intensify high frequency components and restrain low frequency components. Then the filtered power spectrum is replicated into N copies to form a power spectrum array displayed on the Electronic-Addressing Spatial Light Modulator (EA-SLM). The N output correlation signal addition is obtained by inverse Fourier transform of the power spectrum array with optical lens. The theoretical analysis and computer simulation indicate that the correlator can make full use of the areas of the SLM, improve the light efficiency, sharpen the correlation peak effectively and eliminate the central zero-order component in correlation place.
Three dimensional object recognition with rotation-invariant
Author(s):
Jing Lv;
Xianyu Su
Show Abstract
An automatic method for rotation-invariant three-dimensional (3-D) object recognition is proposed. The method is based on the use of 3-D information contained in the deformed fringe pattern obtained when a grating is projected onto an object's surface. Since the deformed fringe pattern contains the height information of object, the method has the characteristic of intrinsic 3-D recognition. The rotation invariance is achieved by using the multi-channel phase-only filter. The filter is composed of deformed fringe patterns of the same object at different angle. The proposed method can be optically implemented by means of VanderLugt optical correlator. Experimental results show the utility of the proposed method and its ability to estimate the rotational angle of the objects.
MOGA algorithm for multi-objective optimization of aircraft detection
Author(s):
Hongguang Sun;
Yuxue Pan;
Jingbo Zhang
Show Abstract
This paper presents effective multi-objective genetic algorithms (MOGA) method, whose character lies in that evolutionary population is preference ranked based on concordance model, which was applied to a multi-objective optimization of aircraft, measure of fitness degree was discussed as an emphasis. The solutions were analyzed and compares with original BP neural networks algorithm, which is better than the network trained only on alternating momentum, which can performed well neural networks and have shown the superiority to the network structure. Based the pareto optimal approaches are equipped with a fast identifying ability in capturing the learned objects, and in the meantime it can adapt the new objects. The experiments with variety of image show that the method proposed is efficient and useful, the result demonstrates that convergence speed is faster than traditional algorithm; target was recognized by this algorithm and can increase recognition precision.
A stereo inspecting detection system based on electronic imaging and computer image processing
Author(s):
Dong Lu;
Zhihong Lu;
Aiguo Wang;
Miao Cao
Show Abstract
This paper introduces a internal flaws detected system. The internal flaws of metal tube or internal hole of mechanical device, such as crazing, rust-eaten and dropping of electroplated coating. By using xenon-light as a light source through the fiber bundle, the internal surface of tube is illuminated and imaged on the CCD optical receiver by endoscope, Then the direction and the size of the flaws are measured after processed by the imaging grab section and computer processing system. This system also can detect the pose water pipe of the aircrafts, the firebox of the aero engine, turbine and lamina which can not be viewed and detected nearly by human eye. It can measure their redundancy and size of internal flaws.
Correlation target recognition for laser radar
Author(s):
JianFeng Sun;
Wei Lu;
Qi Li;
Qian Wang;
Qi Wang
Show Abstract
The target recognition of laser radar is a hot research because laser radar can produce the intensity and range imagery. Laser radar has high space resolution, and can obtain rich target information. Correlation recognition has been used to many fields, such as infrared as well as synthetic aperture radar (SAR). In this paper, the two filters are used in experiment of laser radar. MACH filter is used to detect the target, and DCCFs are used to recognize the unknown target. The samples are generated by OpenGL technology, and the filters are designed using the simulated ladar images. The test samples are added noise according to the imaging principle of laser radar. Two sample sets, one adding noise, another filtering the noise, are used in order to contrast the different performance. At last, the experiment results are given.
Fusion algorithm for color microbiological organisms images in automatized microscopes
Author(s):
Josué Álvarez-Borrego;
Vitaly Kober;
Crisitian Gallardo-Escárate;
Maria C. Chávez-Sánchez;
Emma Fájer-Ávila;
Mario Alonso Bueno-Ibarra
Show Abstract
In this paper we present an algorithm to determine the multifocus image fusion from several color microbiological images captured from the best focusing region. This focusing region is built by including several images up and down starting from Z position of the best image in focus. The captured RGB images are converted to YCbCr color space to have the color CbCr and intensity Y channels separated with the objective to preserve the color information of the best in focus image. However this algorithm utilizes the Fourier approach by using the Y channel frequency content via analyzing the Fourier coefficients for retrieving the high frequencies in order to obtain the best possible characteristics of every captured image. After this process, we construct the fused image with these coefficients and color information for the optimum in focus image in the YCbCr color space, as a result, we obtain a precise final RGB fused image.
Superresolution of ultraviolet Betelgeuse image
Author(s):
Masafumi Kawagoe;
Noriaki Miura
Show Abstract
We apply some superresolution techniques to ultraviolet Betelgeuse images observed with the Hubble Space Telescope (HST). Betelgeuse images used here were observed from 1995 to 1999. The profile of Betelgeuse drastically changed during this period, and bright areas (hotspots) sometime appeared on its surface. Their sizes were comparable to the diffraction limit of the HST. Thus, to obtain information on Betelgeuse, the improvement of the resolution is necessary. Through applying superresolution methods to observed images, we clarify their utilities in the analysis of Betelgeuse images. We obtain the positional information on hotspots from superresolved images, and then carry out model fitting of Betelgeuse profiles. We describe the results of model fitting.
Fruit image segmentation based on a novel watershed algorithm
Author(s):
Hao Zhu;
Wenyao Liu
Show Abstract
Previous research about automatic vision systems applied to fruit imaging segmentation fails. Watershed transformation is a powerful morphological tool for image segmentation. However, the performance of segmentation methods based on watershed depends largely on gradient of the image. It's not perfect to segment object with single-scale gradient. In this paper we present a multi-scale algorithm for computing morphological gradient images, after this transformation, there exists a strict causality between gradient watershed under different scales of geodesic reconstruction. The results demonstrate the superior performance of the watershed segmentation over the conventional techniques.
A new algorithm of image segmentation for overlapping grain image
Author(s):
Xun Zhang;
Guang Jin;
Xiaowei Sun
Show Abstract
Image segmentation is primary issue in image processing, at the same time it is principal problem in low level vision in computer vision field. It is the key technology to process image analysis, image comprehend and image depict successfully. Aim at measurement of granularity size of nonmetal grain, a new algorithm of image segmentation and parameters calculation for overlapping grain image is studied. The hypostasis of this algorithm is present some new attributes of graph sequence from discrete attribute of graph, consequently achieve that pick up the geometrical characteristics from input graph, and new graph sequence which in favor of image segmentation is recombined. The conception that image edge denoted with "twin-point" is put forward, base on geometrical characters of point, image edge is transformed into serial edge, and on recombined serial image edge, based on direction vector definition of line and some additional restricted conditions, the segmentation twin-points are searched with, thus image segmentation is accomplished. Serial image edge is transformed into twin-point pattern, to realize calculation of area and granularity size of nonmetal grain. The inkling and uncertainty on selection of structure element which base on mathematical morphology are avoided in this algorithm, and image segmentation and parameters calculation are realized without changing grain's self statistical characters.
Research on sampling method for three-dimensional flow field reconstruction of incomplete data
Author(s):
Hongbing Yao;
Xia Ye;
Jun Zhou;
Guilin Ding;
Anzhi He
Show Abstract
An orthogonal projection sampling method is proposed in this paper and is applied in the reconstruction of incomplete data field by using the prior knowledge algorithm based on the modified ART, by which the satisfying reconstruction results can be obtained even with less sampling directions and limited sampling angular range. The Mean Square Error (MSE) and peak value between the origin field, the reconstructed field using orthogonal projection sampling method and traditional projection sampling method are analyzed with the numerical simulation of computer. The results indicate that the orthogonal projection sampling can reduce the MSE greatly in the reconstruction of incomplete data. Thus our researches provide a new means for the reconstruction of incomplete data field.
The analysis in the problem of grooming of traffics in WDM tree networks using genetic algorithm
Author(s):
Min Cheng;
Yong Xu;
Rong Chen
Show Abstract
Traffic grooming in WDM optical networks is one of the most important and hot problem in the area of optical networks. We first systematically investigated the grooming problems in WDM optical tree networks with traffic requirements in this thesis. We first propose the genetic algorithms (GA) to deal with a variety of grooming problems in tree networks, and propose the connection model of optical tree networks, and apply the technology of wavelengths-reuse in the decoding of the individual in the genetic algorithms, and get good grooming results.
An object recognition method based on fuzzy theory and BP networks
Author(s):
Chuan Wu;
Ming Zhu;
Dong Yang
Show Abstract
It is difficult to choose eigenvectors when neural network recognizes object. It is possible that the different object eigenvectors is similar or the same object eigenvectors is different under scaling, shifting, rotation if eigenvectors can not be chosen appropriately. In order to solve this problem, the image is edged, the membership function is reconstructed and a new threshold segmentation method based on fuzzy theory is proposed to get the binary image. Moment invariant of binary image is extracted and normalized. Some time moment invariant is too small to calculate effectively so logarithm of moment invariant is taken as input eigenvectors of BP network. The experimental results demonstrate that the proposed approach could recognize the object effectively, correctly and quickly.
Grating interferometry method for torsion measurement
Author(s):
Xiang-rong Li;
Yan-feng Qiao;
Wei Liu;
Yao-yu Zhang
Show Abstract
Method of grating interferometry was presented for torsion angle measurement, moire fringe generated by two gratings is used in a new field, it breaks through moire fringe's routine application. Measurement principle is described, torsion angle can be gotten by the tilt angle or the width of moire fringe. Different from moire fringe's characteristic information extracting methods in traditional measurement fields, fringe-tilt method and fringe-width method were put forward to extract moire fringe's characteristic information. Fringe-tilt method is on the basis of moire fringe's tilt to acquire torsion angle, uniform formula was built aiming at all positions of two gratings in the coordinates, fringe-width method is on the basis of moire fringe's width to acquire torsion angle, three key problems are given about fringe-width method. Thick, middle and thin moire fringe were collected in experiments and processed by two methods, fringe-width method's result shows that magnitude of boat torsion error is satisfied with that of theoretical precision analysis, and the change rule of torsion error is also same to that of theoretical analysis, the thicker fringe is, the higher precision is, when fringe width arrives to be 1695μm, the precision is 1.7", the thinner fringe is, the lower precision is, when fringe width arrives to be 734.7μm, the precision is 6.7". In addition to these, the results of repeatability experiments, sensibility experiments are given. In a word, the measurement principle is right and the precision of fringe processing is also reliable.
An image identification system of seal with fingerprint based on CMOS image sensor
Author(s):
Xu-cheng Xue;
Shu-yan Zhang;
Yong-fei Guo
Show Abstract
CMOS image sensors now become increasingly competitive with respect to their CCD counterparts, while adding advantages such as no blooming, simpler driving requirements and the potential of on-chip integration of sensor, analog signal conditioning circuits, A/D converter and digital processing functions. Furthermore, CMOS sensors are the best choices for low-cost imaging systems. An image identification system based on CMOS image sensor is used to identify the seal images that include fingerprint, and then determine whether the seal is fake or not. The system consists of a color CMOS image sensor (OV2610), a buffer memory, a CPLD, a MCU (P89C61X2), a USB2.0 interface chip (ISP1581) and a personal computer. The CPLD implement the logic and timing of the system. The MCU and the USB2.0 interface chip deal with the communications between the images acquisition system and PC. Thus PC can send some parameters and commands to the images acquisition system and also read image data from it. The identification of the images of seal is processed by the PC. The structure and scheme of the system are discussed in detail in this paper. Several test images of seal taken by the system are also provided in the paper.
A new method for number recognition based on feature extract
Author(s):
Huaide Zhou;
Guangze Li;
Chuanwei Xiao;
Zhihang Hao
Show Abstract
In this paper, the authors put forward a new method for print number recognition when we research on the OCR (Optical Character Recognition). It's different from the traditional method such as NN (Neural Networks) recognition or model matching. By this method, the number waiting for recognizing was treated as the fingerprint lines, then, defined and extracted the features about the number for recognition. At end of the paper, an experiment result is given.
Design of beam sampling grating and study on its diffraction action
Author(s):
Quan Liu;
Jianhong Wu;
Chaoming Li
Show Abstract
The beam sampling grating (BSG) is one of the important diffractive optical elements used in the final target system of the inertial confinement fusion (ICF). The BSG is designed in this paper. By use of optical holographic theory, achromatic optical system on recording holographic BSG mask is designed. Its aberration is analyzed by using optical design software. Meantime, the diffraction efficiency of the BSG is discussed by using rigorous coupled-wave theory. Maintaining spatial uniformity of the diffraction efficiency across the grating aperture (320mm×320mm) is the most challenging processing requirement. The results shows: there are duty cycle and groove depth in grating parameter, the groove depth is more important to spatial uniformity of diffraction efficiency. Some useful information for practical fabrication of the BSG is given also. A prototype beam sampling grating will be fabricated in late 2005.
Intersectant multi-target serial number fuzzy match by multi-parameters
Author(s):
Ming-jia Wang;
Yan-jie Wang
Show Abstract
In order to match the intersectant targets' tab when these objects separate, a kind of method that makes use of fuzzy multi-parameter to match targets is proposed. Multi-parameters include the forecasted position after targets separate, target speed, target size and geometry shape, and different parameter corresponds to different influence coefficient, evaluate the integrated matching coefficient that every observation target corresponds to forecasted target, and the corresponding relationship that matching coefficient is the biggest is the best matching result. In order to locate the position and speed of forecasted target, a new method of track forecast is proposed. firstly, Hough transform is used to the object's track before objects intersect, by this, the object's positions that the warp between forecasted location and observation location is large enough is eliminated, then least square method is used for track forecast by the remainder valid positions, and get hold of the forecasted position when objects separate. The experiment results show: when tracking the bulky objects which intersect and separate, the right identification probability of traditional least square method is 87.5%, and the right identification probability of fuzzy match by multi-parameters can attain 96%, the reliability improves in evidence.
Three-dimensional shape visualization of object in impact
Author(s):
Qican Zhang;
Xianyu Su
Show Abstract
A method of three-dimensional (3D) shape measurement and visualization of object during impact based on Fourier transform profilometry (FTP) is proposed and verified by experiment. A sequence of dynamic deformed fringe images on the surface of object is grabbed by high speed CCD camera and saved on disk rapidly. Than processed them by Fourier transform, filtering, inverse Fourier transform and unwrapped these phase maps in 3D phase space, the shape deformation of object during impact can be recovered. This method is suitable for wide use in studying such high-speed motion as explosion, expansion, contraction and even shock wave. Based on the phase difference between two neighborhood frames, we propound a 3D phase unwrapping algorithm, which will be of great benefit to 3D phase unwrapping in speed and accuracy. The results of our experiment indicate that the method, presented in this paper, can efficiently deal with the surface shape measurement for rapid motion object and will be a promising one with the development of high-speed frame grabber.
Real-time quality control on a smart camera
Author(s):
Chuanwei Xiao;
Huaide Zhou;
Guangze Li;
Zhihang Hao
Show Abstract
A smart camera is composed of a video sensing, high-level video processing, communication and other affiliations within a single device. Such cameras are very important devices in quality control systems. This paper presents a prototyping development of a smart camera for quality control. The smart camera is divided to four parts: a CMOS sensor, a digital signal processor (DSP), a CPLD and a display device. In order to improving the processing speed, low-level and high-level video processing algorithms are discussed to the embedded DSP-based platforms. The algorithms can quickly and automatic detect productions' quality defaults. All algorithms are tested under a Matlab-based prototyping implementation and migrated to the smart camera. The smart camera prototype automatic processes the video data and streams the results of the video data to the display devices and control devices. Control signals are send to produce-line to adjust the producing state within the required real-time constrains.
Measurement of plant leaf area using image processing techniques
Author(s):
Zhengjun Qiu;
Hui Fang;
Yun Zhang;
Yong He
Show Abstract
It is difficult to measure the leaf area of plants by conventional methods as a result of the irregular leaf shapes. In this research, a new method was presented to measure leaf area using image processing techniques. The leaves images were acquired by MS3100 3CCD camera, and each image was composed of three channel data (green, red, near-infrared). The image data were transferred to a host computer and were stored as files in TIFF or JPEG format. Some image processing methods were applied to calibrate the leaf image, detect the margin of the leaf, and calculate the area by counting the pixels in the leaf. From the experimental results, it shows that the image method has good measurement accuracy; the relative error is less than 0.5 percent; and image processing is a rapid and non-destructive tool to measure the leaf area of plants.
A new segmentation method of CR images based on discrete wavelet transform and mathematics morphology
Author(s):
Zhe Li;
Lian-qing Huang
Show Abstract
In this paper, we propose a segmentation method of CR(computed radiography) images with being rid of under-segmentation and over-segmentation. An under-segmentation occurs when pixels belonging to different objects are grouped into a single region. Such errors are the most dangerous because they can invalidate the whole segmentation process. The phenomenon always takes place when we segment CR images because of the principle of CR. In order to depressed under-segmentation, we enhance the CR images using DWT (discrete wavelet transform) to get more detail of CR image features. As we enhance the CR image, the over-segmentation maybe occurs. Compared with under-segmentation, the over-segmentation occurs when a single objects is subdivided by segmentation into several region. For the purpose of preventing from the over-segmentation, we present a scheme for enhanced CR images based on watershed algorithm that solves over-segmentation problem. We use marker-based watershed algorithm. Together with gradient image and marker image, watershed segmentation can make sure to partition CR image into meaningful object and avoid further segmentation of homogeneous regions. The result of the proposed algorithm are compared with those of other standard methods. Experiments have shown a better result and indeed solved under-segmentation and over-segmentation problems.
Resolution analysis of digital holography
Author(s):
Qi Fan;
Jianlin Zhao
Show Abstract
The resolutions of the Charge Coupled Device (CCD), the reconstructed image, and the reconstructed image plane in digital holography are theoretically and experimentally analyzed in this paper. Three important conclusions are achieved: (1) By studying the resolution requirements of CCD in different digital holographic recording setups, it shows that lensless Fourier transform holographic recording setup can relax the requirement of the resolution and use the full bandwidth of the CCD sensor, when the object is very small. (2) The resolution of the reconstructed image is mainly determined by the highest spatial frequency of the object wave recorded using CCD, and will increase with the larger CCD size, the higher resolution of the CCD sensor, and the shorter recording distance. (3) The resolutions of the reconstructed image and the reconstructed image plane are different. The latter can influence the quality of the former on display. The resolution of the reconstructed image plane is not only relative to the reconstruction algorithms, but also the parameters of the recording setup. A simple and convenience method is presented, which can effectively increase the resolution of the reconstructed image plane in Fresnel-transform reconstruction of digital holograms. By padding zeros operation to a digital hologram recorded by CCD, the reconstructed image with high quality can be obtained. With similar method, the vision aberration of the reconstructed image due to the difference of CCD size in horizontal and vertical direction can be rectified. Experimental results show a good agreement with theoretical analysis.
Improved classification of soil salinity by decision tree on remotely sensed images
Author(s):
Ping Rao;
Shengbo Chen;
Ke Sun
Show Abstract
Soil Salinity, caused by natural or human-induced processes, is not only a major cause of soil degradation but also a major environmental hazard all over the world. This results in increasing impact on crop yields and agricultural production in both dry and irrigated areas due to poor land and water management. Multi-temporal optical and microwave remote sensing can significantly contribute to detecting spatial-temporal changes of salt-related surface features. The study area is located in the west of Jilin Province, Northeast China, which is one of most important saline-alkalized areas in semi-arid and arid area in North China. Decision tree classifiers are used to improve the classification of soil salinity on Landsat Thematic Mapper (TM) images in later autumn of 1996. The Kauth-Thomas (K-T) transformation was performed after TM image preprocessing including image registration, mosaic and resizing for the study area. Then the first component of KT transformation, TM 6 imagery (thermal infrared imagery), and NDVI (Normalized Difference Vegetation Index) from TM 4 and TM 3 images, were density-sliced respectively to establish suitable feature classes of soil salinity as the decision nodes. Thus, the classification of soil salinity was improved using decision trees based on these feature classes.
Compared with the conventional maximum likelihood classification, this method is more effective to distinguish soil salinity from mixed residential and sand areas in the west of Jilin Province, China.
Fusion of Terra-MODIS and Landsat TM data for geothermal sites investigation in Jiangsu Province, China
Author(s):
Shengbo Chen
Show Abstract
Geothermal resources are generally confined to areas of the Earth's crust where heat flow higher than in surrounding areas heats the water contained in permeable rocks (reservoirs) at depth. It is becoming one of attractive solutions for clean and sustainable energy future for the world. The geothermal fields commonly occurs at the boundaries of plates, and only occasionally in the middle of a plate. The study area, Jiangsu Province, as an example, located in the east of China, is a potential area of geothermal energy. In this study, Landsat thematic Mapper (TM) data were georeferenced to
position spatially the geothermal energy in the study area. Multi-spectral infrared data of Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the Terra platform were georeferenced to Landsat TM images. Based on the Wien
Displacement Law, these infrared data indicate the surface emitted radiance under the same atmospheric condition, and stand for surface bright temperature respectively. Thus, different surface bright temperature data from Terra-MODIS band 20 or band 31 (R), together with Landsat TM band 4 (G) and band 3 (B) separately, were made up false color composite images (RGB) to generate the distribution maps of surface bright temperatures. Combing with geologic environment and geophysical anomalies, the potential area of geothermal energy with different geo-temperature were mapped respectively. Specially, one geothermal spot in Qinhu Lake Scenery Area in Taizhou city was validated by drilling, and its groundwater temperature is up to some 51°.
Using real-time embedded system with multiple DSPs in corona detection
Author(s):
Feng Yan;
Xin Wang;
Xiao Yu;
Yong-xin Sui;
Chun-shui Jin;
Huai-jiang Yang
Show Abstract
The method how to detect and locate corona real-time by double spectrums image, UV spectrum image and visible spectrum image of the object, was introduced. And the construction of an embedded system on which the double spectrums detection method can be realized was also introduced. CCD cameras' control data and their output image data were processed respectively. Using this kind of system, we can find the corona real-time by a combined image, thus where the electric leakage is can be found quickly. Experiments indicate this method and the embedded system with multiple DSPs suits for corona detection.
An opt-electronic hybrid expert system: a model and its hardware support system
Author(s):
Xuan-Jing Shen;
Qing-Ji Qian
Show Abstract
This paper, based on the analysis of main factors which determine the efficiency of an expert system(ES), proposes an expert system model based on optical parallel matching (ESBOPM) and a scheme of opt-electronic hybrid hardware support system. The ESBOPM adopts quasi-production presentation of knowledge, and the knowledge coding and knowledge matching operation can be realized in parallel, which is suitable for optical parallel matching. The performance evaluation and experiment results show the ESBOPM and its hardware support system is valid and increase the matching speed to 30.46 times (comparing with serial matching) or 7.55 times (comparing with indexed matching).
Electromagnetic optimization of wideband spectrograph gratings
Author(s):
Juha Pietarinen;
Tuomas Vallius
Show Abstract
Electromagnetic optimization is applied to four level surface relief gratings to obtain high diffraction effciencies over wide spectral ranges. The results are compared with the classical designs and proved superior. Significant improvements in the diffraction efficiency or independence of the incident wavelength can be obtained.
Illumination independent mixed colors produced by diffractive optics
Author(s):
Noora Tossavainen;
Tuomas Vallius;
Markku Kuittinen
Show Abstract
We apply transmission gratings under Littrow incidence to produce polychromatic colors by additive color mixing. Parametric optimization of gratings is employed to confirm high efficiency. In addition, we show that the system can yield the same color from two different light sources with arbitrary spectra, i.e. system can produce metameric colors.
Numerical analysis of compound aspheric lens design and fabrication
Author(s):
Xuemin Cheng;
Duanyi Xu;
Qun Hao
Show Abstract
This paper discussed the scheme of modeling compound aspheric components during the optimization process. First, the method to model the refractive index and thickness changes of the resin layer induced in the injection-mold process is described. It demonstrated the available constraints upon the refractive index difference between the resin and the glass during the optimization run. The tolerance aspects of such components are then investigated, including the refractive index and thickness of the resin layer, as well as the conventional surface roughness, element position and rotation errors, and surface slope errors; especially for the centering tolerance. It is shown that the approximate model might be useful for different combinations with UV-curable resins and glasses for aspheric lens design and fabrication. An objective for optical
pickup system comprising one compound aspheric surface is designed with the scheme.
Research on tracking approach to low-flying weak small target near the sea
Author(s):
Shu-yan Zhang;
Wei-ning Liu;
Xu-cheng Xue
Show Abstract
Automatic target detection is very difficult in complicate background of sea and sky because of the clutter caused by waves and clouds nearby the sea-level line. In this paper, in view of the low-flying target near the sea is always above the sea-level line, we can first locate the sea-level line, and neglect the image data beneath the sea-level line. Thus the noise under the sea-level line can be suppressed, and the executive time of target segmentation is also much reduced. A new method is proposed, which first uses neighborhood averaging method to suppress background and enhance targets so as to increase SNR, and then uses the multi-point multi-layer vertical Sobel operator combined with linear least squares fitting to locate the sea-level line, lastly uses the centroid tracking algorithm to detect and track the target. In the experiment, high frame rate and high-resolution digital CCD camera and high performance DSP are applied. Experimental results show that this method can efficiently locate the sea-level line on various conditions of lower contrast, and eliminate the negative impact of the clutter caused by waves and clouds, and capture and track target real-timely and accurately.
An improved two-dimensional entropy method for star trail tracing in deep sky
Author(s):
Zhi-jun Yao;
Yan-Jie Wang;
Qui-lei Han
Show Abstract
The trace of star trail is an important component of deep sky detection. The stars are low contrast targets, and their self-rotation will make their brightness change in cycle. Above all, the trail trace is vulnerable to the block and disturbance of other stars. Traditional one-dimensional maximum entropy thresholding algorithm is vulnerable to the noise, and the calculation of two-dimensional entropy methods is too large and takes too much time. This paper proposes an improved two-dimensional entropy threshold algorithm. We use recursion iteration method to eliminate the redundancy calculation, and reduce the size of two-dimensional histogram based on the deep sky stars characteristic, such as low contrast, fuzziness and the centralized histogram. We also combine our algorithm with the space trail trace model to forecast the star trace. Experiments results show, when the star are blocked or they turn dark, the method still can well extrapolate the star trace. Our method improves the capability of trailing the ebb and small star, and increases the precision of tracing. It is also robust to the noise, so there is a good application foreground for the method.
Real-time image registration algorithms based on region of interest
Author(s):
Songtao Liu;
Xiadong Zhou;
Xuewei Wang
Show Abstract
Image registration is a difficult problem when dealing with images captured by different sensors, for instance, Visible and IR sensors, due to their texture, gray not matched and feature inconsistent. Since the edges of the objects present in the images are preserved in most cases, so, in this paper, a new contour-based image registration algorithm is proposed. First, an edge detection method based on multi-scale and multi-direction morphology is proposed for extracting contour. Then the matched contour pairs are found according to the following shape attributes, such as the first and second invariant moments, etc. Next, within these matched contours, several control-point pairs are selected, which has the characteristics of 1) even distribution 2) a suitable number of points 3) locally maximum curvature. In addition, the sea-sky-line is extracted in advance, which determines the region of image registration and reduces the computation time. The performance of our algorithm is demonstrated by estimating the registration accuracy and evaluating the fusion effects of the visual and IR images of ship target.
The mechanism of local 3D image restoration base on infrared grid raster
Author(s):
Quignan Liu;
Yujuan Quan;
Guixiong Liu
Show Abstract
In the circumstances of low luminance, visible assistant light is not available or convergence is very similar to the background or syncretism to each other, research on the local 3-D image restoration method is of great sense. Generally to restore 3-D image from binocular 2-D image, active vision is in need. Otherwise the application would be only constrained in objects of simple shape. A local 3-D image restoration method based on infrared grid raster was proposed in the paper. Its principal is irradiating the goal object by non-structure infrared grid raster, catching the object area image by double CCD infrared camera and distilling the grid data from the image. Then the 3-D grid image of the target was restored by the binocular image matching from the grid data. Finally, the practice 3-D image of the object is fitted from the 3-D grid image. By using the infrared grid raster, the target could be added with additional grid without frightening it and the process was quite efficient. At present, the stereo image restoration based on grid and grid raster was realized. Thus, through optimizing the existing image pretreatment technology, character distilling technology and stereo matching technology, the clear local 3-D image of the target would be restored faster even in the case of lower environment luminance while the visible assistant light is forbidden.
Adaptively image de-striping through frequency filtering
Author(s):
Zhijia Zhang;
Zelin Shi;
Weifang Guo;
Shabai Huang
Show Abstract
The paper presents a new algorithm for image de-striping. A kind of adaptive frequency filter is constructed based on two-dimension fast Fourier Transform in the proposed algorithm. To construct the adaptive filter, a stripe frequency band (SFB) and an accumulation distribution function (ADF) are defined in the fourier power spectrum. Comparing to the traditional de-striping methods, the algorithm does not take on abundant computation load and need no manual participating to outline the stripe band in frequency domain. Through the evaluation of visual effect and SNR/PSNR comparison, the experiment results demonstrate the proposed algorithm can remove the strips effectively while contain the original image information perfectly.
Transverse-adding fabrication technique of binary element and alignment error analysis
Author(s):
Min Chen;
Daxiang Yu;
Yiqing Gao;
Shenglin Yu
Show Abstract
On the basis of close analysis of the drawback in conventional fabrication techniques of binary optical element, this paper presents a new method for fabricating optical element. This method can be called transverse-adding fabrication technique(TAFT), and it is developed from the rapid prototyping technique used in microelectronic processing and micro-machining. The principal objective developing this technique is to realize the compatibility of micro-optics with microelectronics and micro-machining technique to provide technical support for the integrated single-chip micro photo-electromechanical system. An explanation for the technological principle and process of this technique is stated. By analyzing experimental data, the selection of materials and corresponding process parameters for implementing this technique were determined. The main process error of this technique, alignment error, was analyzed and calculated. In addition, a computerized simulation was carried out. Analysis shows that this technique can not only fabricate continuous phase component, its diffraction efficiency is insensitive to the alignment error as well. It is therefore clear that the transverse-adding fabrication technique is a feasible technique for fabricating binary optical elements and has an advantage over conventional techniques in fabricating precision.
Intersection measuring system of trajectory camera with long narrow photosensitive surface
Author(s):
Lixin Liu;
Lihong Liu
Show Abstract
In order to engage a precise measurement on small target highly flying in large range, adopting many CCD cameras to compose trajectory camera with long narrow photosensitive surface is in studied. Based on intersection measuring principle, it leads out computing formula of intersection measuring coordinate. The measurement accuracy is carefully analyzed by the error theory. The results prove that the capture probability can be highly improved using trajectory camera with long narrow photosensitive surface as well as the coordinate measuring accuracy.
A novel approach to fast motion vector search
Author(s):
Shengcai Li;
Zhanguo Li
Show Abstract
Motion estimation plays an important role in video compression systems, and it's the most intensively computational and the most time-consuming part at the same time. So it could significantly affect the operation efficiency of whole video coding systems and the reconstructed quality of video sequence. The latest video coding standard, H.264, provides a significant coding efficiency than previous standards. But this coding gain comes at the cost of a very computationally-intensive motion estimation module. To realize the implementation of the H.264 video coding in-time, it's desirable to develop fast motion search algorithm. In order to reduce computation complexity of the motion search at sub-pixel accuracy, a fast and effective search algorithm for half-pixel motion estimation is proposed in this paper. Based on the single valley characteristic of half-pixel error matching function inside search grid, half-pixel candidate points needing checking are predicted with the help of comparison results of SAD values for four integer-pixel points around integer-pixel motion vector, so a great number of computations associated with search process are avoided. The experimental results reveal that, to all kinds of video sequences, the proposed algorithm can obtain almost the same video quality as that of the half-pixel full search algorithm with reduced average 72% computation cost.
Experimental research on fiber Bragg grating hydrophone
Author(s):
Bo Liu;
Wencheng Niu;
ChunXian Xiao;
Guiyun Kai;
Xiaoyi Dong
Show Abstract
The FBG being used as the basic sensor unit, a hydrophone sensor has been designed and manufactured. Its principle and relevant experimental result are introduced. By using the matched fiber grating demodulation technique, dynamic signal measurement with high sensitivity is realized. The frequency range of the FBG-based hydrophone is 10~3kHz with a dynamic range is 60dB. Due to the characters of FBG itself, the measure of multiple-points underwater signal can be realized conveniently by using WDM and TDM techniques.
The information acquirement of hyperspectral detection system with harmonic diffractive element in infrared dual band
Author(s):
Qiang Sun;
Hu Xu;
Yuncui Zhang;
Yingying Gao
Show Abstract
A novel design of combination of hybrid system and zoom system in hyperspectral detection imaging is discribed based on the application of harmonic diffractive element (HDE) compared with conventional system. The principles of HDE and infrared zoom hyspectral detection system are presented and the results of a example design are given. It is show that the resolution of this hybrid system is improved and the light power received by Cassegrain system is enlarged. Wavefront aberrations are less than 1/4 wavelength and Modulation Transfer Function in the dual band on each zoom focus location approaches or attains the diffraction limit on 20 cycles/mm.
Broadband diffractive elements based on polarization gratings
Author(s):
Hanna Lajunen;
Jani Tervo;
Jari Turnnen
Show Abstract
A method for designing high-efficiency paraxial domain diffractive elements working over a broad wavelenght is introduced. These elements are based on polarization gratings that manipulate spacially the local state of polarization using form bifringent subwavelenth diffractive structures. Any scaler transmission function can realized simulataneosly for a wide band of wavelenths using such elements. In some cases it is also possible to design beam splitters that exceed the scalar paraxial-domain upper bounds of diffraction efficienty over a broad wavelength band.
Experimental study of Raman amplification on stimulated Brillouin scattering in the G652 fibers at 1520nm
Author(s):
Zaixuan Zhang;
Bizhi Dai;
Laixiao Li;
Haifeng Xu;
Dan Geng;
Honglina Liu;
Jianafeng Wang;
Chenxia Li;
Tiao Liu;
Insoo S. Kim
Show Abstract
The forward and backward cascaded stimulated Brillouin scattering(SBS) in the backward pumped S band distributed G652 fiber Raman amplifier have been researched, pumped by the tunable power at 1428nm fiber Raman laser and signal source is a tunable power external cavity laser (ECL) with narrow spectral bandwidth (<100MHz). The threshold power of backward Stokes the first and second stimulated Brillouin scattering SB1- and SB2- in the backward pumped S band distributed fiber Raman amplifier is 5mW and 67.6mW, respectively. The Stokes stimulated Brillouin scattering lines is amplified by fiber Raman amplifier and fiber Brillouin amplifier. The total GA is production of the gain of Raman GR and the gain of Brillouin amplifier GB. GA=GR×GB. In experimental work, the saturation gain of SB1- and SB2- is about 50dB and 65dB respectively and the saturation gain of 25km G652 backward FRA is about 25dB, so the gain of backward fiber Brillouin amplifier SB1- and SB2- are about 25dB and 40dB, respectively. The forward SBS does not obey the common theory that only weakening backward-SBS lines existed, according to conservation of energy and momentum and wave vector selected rule. Because the wave-guide characters weaken the wave vector rule, but the forward transmit sound wave-guide forward Brillouin scattering lines are generated and amplified in S band G652 FRA. The stimulated threshold power of the forward first Stokes SBS (SB1- ) in the backward pumped FRA is 6.6mW. In experimental work, the saturation gain of SB1- is about 49dB and the saturation gain of 25km G652 backward FRA is about 10dB, so the gain of SB1- in the forward fiber Brillouin amplifier is about 39dB.
Measurement of the three-dimensional thermal expansion coefficients of Beryllium using fiber Bragg grating sensors
Author(s):
Xiujuan Yu;
Youlong Yu;
Baojin Peng;
Min Zhang;
Yanbiao Liao;
Shurong Lai
Show Abstract
Fiber Bragg grating is simple, intrinsic sensing elements which can be photo-inscribed into a silica fiber. It has many advantages and be useful for a variety of application. In this paper, we reported the experimental results of measuring the three-dimensional thermal expansion coefficients of Beryllium by using fiber Bragg grating (FBG) sensors within a large temperature range between -50°C and +150°C. Three FBG sensors were bonded on the surface of the material in the directions of x, y, z to measure the three-dimensional thermal expansion coefficients and a reference FBG sensor was used to compensate the temperature variation. The experimental results show that it can be used in harsh environment.
A new method for fiber Bragg grating wavelength demodulation with calibration
Author(s):
Jian-wei Fu;
Li-zhi Xiao;
Yuan-zhong Zhang;
Xiao-liang Zhao;
Hai-feng Chen
Show Abstract
A wavelength calibration method is proposed to improve Fiber Bragg Grating (FBG) Wavelength detection precision. The reflected spectra of two reference FBG elements and a sensing FBG element are scanned by narrow band light from a fiber F-P tunable filter (FFP-TF) driven by triangular waveform voltage. Sequence numbers of FBG and peak position of spectra are identified with full spectrum analysis. Two reference FBG elements with fixed wavelength are used to monitor the transmission wavelength of filter and to construct the relationship between wavelength and the driving voltage, the driving voltage of the sensing FBG spectrum peak is scaled as the Bragg wavelength with the linear interpolation method. In the temperature experiment, three peak-seek methods such as centroid method, differential method and Gaussian-fit method are introduced and the temperature measurement precisions of ±1Co,±0.5Co and ±0.3Co are achieved respectively, corresponding to the wavelength error of ±10pm, ±5pm and ±3pm. Finally, multipoint FBG sensing system is accomplished with calibration and wavelength measurement precisions of ±10pm is obtained. The experimental results shows that the new method can reduce the wavelength measurement error caused by nonlinearity in piezoelectric transducer (PZT) response and wavelength drift due to PZT hysteresis.
Modeling and design of a parallel demodulation system used for EFPI and FBG sensor
Author(s):
Junfeng Jiang;
Tiegen Liu;
Yimo Zhang;
Lina Liu;
Yunxin Wang;
Ying Zha;
Fan Zhang;
Pin Long
Show Abstract
Extrinsic Fabry-Perot interferometer (EFPI) and fiber Bragg grating (FBG) sensors can construct one of most promising sensor group for simultaneous temperature and strain measurement in structure health monitoring. The demodulation of the sensor group is critical. Here, a parallel demodulation system used for the goal is presented, which is based on a Michelson interferometer and combines the method of low coherence interference of EFPI sensor and Fourier transform spectrum of FBG sensor. The parallel demodulation method is modeled with Fourier transform spectrum theory, which shows the common base that existing between low coherence interference and Fourier transform spectrum. Three data processing methods are proposed according to different application situations, and separation method for EFPI and FBG overlapping signals is emphasized. The design of system is described, and the optical path difference (OPD) scanning and sampling method without reference light are discussed in detail. Then a series of experiments were carried out. The results showed the parallel demodulation system has good performance of spectrum demodulation, low coherence interference demodulation and parallel demodulation. It can realize simultaneous strain and temperature measurement while keep the whole system configuration less complex.
Measurement of fibers' valid elastic-optic constant based on optical fiber Bragg grating sensor
Author(s):
Bao-jin Peng;
Yan-biao Liao;
Min Zhang;
Hui Wang;
Chao-fu Ying;
Shu-rong Lai
Show Abstract
With the fast development of fiber technology, a lot of new type fibers come out one after another. As the fiber core materials of these new type fibers are not as the traditional pure quartz, if we want to find out the new characteristics of these new type fibers quantitatively, we must know its valid elastic-optic constants, so how to mearsure accurately or calculate valid elastic-optic constants of these new type fibers are the questions we are facing and we must solve them exactly. Plenty of fiber cores of the new type are adulterated, and some material characteristic parameters have no interrelated formula, so someone can only gain them by experiments. There are few literatures published about detecting valid elastic-optic constants. The common method is comparison measuring with piezoelectricity crystal, which is operated complexly and the precision is not high. So this method is not suitable to measure the thin fiber. This paper reports a new method to mearsure fibers valid elastic-optic constants using a temperature referrence FBG, a sensing FBG and a kind of material with known expansion coefficient. We also establish a experimental system, the result of experiment proves that the system can solve the existent cross sensitive problem which caused by temperature and strain effectively. Measurement error is smaller than 1.3%. In addition, this text also points out two other measurement methods in use of FBG combining fiber interferometer and general Michelson interferometer.
SFDM/CWDM of fiber-optic Fizeau strain sensors
Author(s):
Y. J. Rao;
C. X. Zhou;
T. Zhu
Show Abstract
In this paper, a novel method for multiplexing a large number of fiber-optic Fizeau sensors using coarse wavelength division multiplexing (CWDM) and spatial-frequency division multiplexing (SFDM) is proposed and demonstrated. A CWDM device is used to multiplex signals from different sensor channels occupying different wavelength regions divided by the CWDM. More than 10 Fizeau sensors arranged in a single channel can be multiplexed by using SFDM due to the long cavity length of the Fizeau sensor. The experimental results show that a strain accuracy of ±5με is achieved. As up to 100 sensors can be multiplexed simultaneously, this approach can improve the multiplexing capacity of Fizeau strain sensors significantly.
High temperature characteristics of long-period fiber gratings written by high-frequency CO2 laser pulses
Author(s):
Y. J. Rao;
J. Y. Li;
T. Zhu
Show Abstract
It is for the first time that the high-temperature characteristics of long period fiber gratings, written by high-frequency CO2 laser pulses in standard telecommunication fiber, are presented. When the temperature is below 800°C the relationship between the resonant wavelength shift of the grating and the change in temperature is approximately linear, while the temperature is over 800°C such a relationship becomes nonlinear. Similar strain response of the grating under high temperature is also presented.
LS-SVM based signal processing of reflective fiber optic displacement sensor
Author(s):
Xiaodong Wang;
Haoran Zhang;
Changjiang Zhang;
Genliang Feng;
Minlan Jiang
Show Abstract
A least squares support vector machine (LS-SVM) based signal processing approach of reflective fiber optic displacement sensor is presented. The example for extending measuring range of the sensor using LS-SVM has been illustrated. From the experimental results, it can be clearly seen that not only the measuring range can be extended to the whole response characteristics of the fiber optics displacement sensor effectively, but also a desired linear relationship between the actual displacement and the LS-SVM predicted output can be obtained. This means the method proposed is very effective for the signal processing of the sensor.
Multiplexed optical fiber extrinsic Fabry-Perot interferometric sensor system
Author(s):
Zhenguo Jing;
Qingxu Yu
Show Abstract
In this paper, a multiplexed optical fiber extrinsic Fabry-Perot interferometric (EFPI) sensor system with optical switch is implemented. To obtain the absolute length of the EFPI air gap, a cross-correlation signal processing method is introduced. The multiplexing of the sensors is basically based on a 1×N optical switch directly connected to a N-element EFPI sensor array. The EFPI sensors are interrogated one after the other with the same spectrometer by activating the corresponding channel of the optical switch. A multiplexed sensor system prototype with two EFPI sensors is demonstrated to verify the performance of the multiplexing method.
The study on the temperature influence of the grain near infrared spectrum analysis
Author(s):
Jun Zhang;
Xingdan Chen
Show Abstract
Near-infrared spectroscopy was used to examine unmodified wheat powder at temperatures of 14-65oC. A self-regulating diffuse reflected assembly was used to permit collection of spectra of powder samples. Changes to the shape and peak location of the 1400-1500nm and 1900-1950nm water absorption bands, 2000-2050, 2070-2110 and 2250-2300nm bands were measured as temperature varied. Results indicated that temperature changes resulted in slight changes to the water absorption bands in 1400-1500nm and 1900-1950nm regions. From 14-65oC, the 1400-1500nm and 2050-2150nm band shifted approximately 10nm and 16nm toward shorter wavelengths, and 2000-2050nm band shifted approximately 14nm toward longer wavelengths. In addition few numbers of samples cannot constitute good temperature insensitive calibration model even though the spectra were obtained at wide temperature condition.
MOGA algorithm for multi-objective optimization of aircraft detection
Author(s):
Hongguang Sun;
Yuxue Pan;
Jingbo Zhang
Show Abstract
This paper presents effective multi-objective genetic algorithms (MOGA) method, whose character lies in that evolutionary population is preference ranked based on concordance model, which was applied to a multi-objective optimization of aircraft, measure of fitness degree was discussed as an emphasis. The solutions were analyzed and compares with original BP neural networks algorithm, which is better than the network trained only on alternating momentum, which can performed well neural networks and have shown the superiority to the network structure. Based the pareto optimal approaches are equipped with a fast identifying ability in capturing the learned objects, and in the meantime it can adapt the new objects. The experiments with variety of image show that the method proposed is efficient and useful, the result demonstrates that convergence speed is faster than traditional algorithm; target was recognized by this algorithm and can increase recognition precision.
MPRML detection for the readouts of photometric multi-wavelength optical disks
Author(s):
Jiqi Jian;
Cheng Ma;
Huibo Jia
Show Abstract
Based on the readout and crosstalk analysis, a kind of multi-channel partial response maximum likelihood (MPRML) detection method which is suitable for photometric multi-wavelength optical disks has been brought forward, the PR mode and parameters have been discussed, and the optimal solution of the method has been given in the paper. Matlab simulation shows that the MPRML method is useful to improve BER performance and the optimal solution is proper. The experiments on the FPGA-based development board also show that MPRML is applicable for photometric multi-wavelength optical disks.
The fire warning system of identical fiber Bragg grating and its application in petrochemical tank and tower
Author(s):
Ciming Zhou;
Desheng Jiang;
Shenghui Liao;
Hongbo Cheng
Show Abstract
A new fire warning system based on the technique of multiplexing of Identical Fiber Bragg Grating (IFBG) and its application in petrochemical tank and tower are presented in this paper. Sensors of IFBG can largely increase the multiplexing number of sensors and can reduce the cost of demodulation. The number of multiplexed FBG in the IFBG array has come to 100. The new fire warning system has been applied in some petrochemical tank and tower, such as Sinopec Zhenhai Refining and Chemical Company Limited, and has obtained a very good effect.
Application of digital image processing technology in the data restoring process of multi-level digital holographic storage
Author(s):
Lihua Fang;
Yonqing Gong;
Liguang Fang;
Qing Wang
Show Abstract
Firstly, this paper introduces the concept of multi-level digital holographic storage. Then, application of digital image processing technology is brought forward in the data restoring process of digital holographic storage. Information in the reconstructed digital images collected from CCD camera is enhanced through digital image processing technology and threshold decision is gone on so as to decreasing bit error ratio of system. Based on above-mentioned ideal, the programming project is designed, which is applicable to binary and multi-level digital holographic storage. Finally, the quality of a binary experimental image is improved through digital image processing program and the accuracy of threshold decision can be improved.
Novel current sensor based on fiber Bragg grating
Author(s):
Ciming Zhou;
Desheng Jiang
Show Abstract
The work presented here describes a novel current sensor employing an air-core solenoid and a sensor head which is composed of a Fiber Bragg Grating (FBG) and a cup-shaped membrane. In our small-current experiment, the results show a good precision and a good sensitivity which is about 10pm/mA. So this type of sensor can be a candidate for wide applications such as in-line current monitoring and power system current metering.
On-line measurement system of displacement with PSD sensor
Author(s):
Yongcai Yang;
Junsan Ma;
Rimin Pan;
Xiang Yu
Show Abstract
Position sensitive device (PSD) is a kind of new photoelectric device which would produce different electrical signals when the inputting light point irradiates at the different position of PSD surface. In new on-line measurement system of displacement, a laser diode emits the light to measured object and PSD detects the different position of the light point which reflects from the measured object because of its displacement change so that the displacement of object can be measured. This paper will present the principle and schematic diagram of measurement device and introduce the circuits of measuring device. At last the results of experiment are also shown and discussed.
The study on the near infrared spectrum technology of sauce component analysis
Author(s):
Shangyu Li;
Jun Zhang;
Xingdan Chen;
Jingqiu Liang;
Ce Wang
Show Abstract
The author, Shangyu Li, engages in supervising and inspecting the quality of products. In soy sauce manufacturing, quality control of intermediate and final products by many components such as total nitrogen, saltless soluble solids, nitrogen of amino acids and total acid is demanded. Wet chemistry analytical methods need much labor and time for these analyses. In order to compensate for this problem, we used near infrared spectroscopy technology to measure the chemical-composition of soy sauce. In the course of the work, a certain amount of soy sauce was collected and was analyzed by wet chemistry analytical methods. The soy sauce was scanned by two kinds of the spectrometer, the Fourier Transform near infrared spectrometer (FT-NIR spectrometer) and the filter near infrared spectroscopy analyzer. The near infrared spectroscopy of soy sauce was calibrated with the components of wet chemistry methods by partial least squares regression and stepwise multiple linear regression. The contents of saltless soluble solids, total nitrogen, total acid and nitrogen of amino acids were predicted by cross validation. The results are compared with the wet chemistry analytical methods. The correlation coefficient and root-mean-square error of prediction (RMSEP) in the better prediction run were found to be 0.961 and 0.206 for total nitrogen, 0.913 and 1.215 for saltless soluble solids, 0.855 and 0.199 nitrogen of amino acids, 0.966 and 0.231 for total acid, respectively. The results presented here demonstrate that the NIR spectroscopy technology is promising for fast and reliable determination of major components of soy sauce.
The technique of thin beam scan to measure the distributing of refraction ratio of section plane of polymer optical fiber
Author(s):
Hongying Zhou;
Jiabu Chen;
Gao Qiu
Show Abstract
It is necessary to measure the section-plane-distribution of refractive index of prefabricated stick of polymer optical fiber (PSPOF) accurately, because it decides the transfer characteristic of polymer optical fiber (POF). Usually interferometer method, neat-field scan and focusing method are used in measurement. A new method of measurement, that is thin-beam-scan method, is described in this paper. When thin beam incident upon PSPOF, the light is converged for the PSPOF which act as columnar lens. After a series of refraction, light pass through PSPOF and exit from the other side of the fiber. We assume a distribution of section-plane-distribution of refractive index in PSPOF, then do the ray tracing calculation based on geometrical optics and get the theoretical location on the exit section plane of the fiber. At the same time we get the real exit location of light by experiment. We can construct a evaluation function with difference of the two results. And correct the assumption of the section-plane-distribution of refractive index in PSPOF by Monte-Carlo method until the evaluation function value limit to a small numerical value which means the theoretical result approach to the real distribution of refractive index.
Iterative detection for imaging page-oriented optical data storage systems
Author(s):
Nopparit Intharasombat;
Tawei Ho;
Alexander A. Sawchuk
Show Abstract
Imaging page-oriented optical data storage, with its high bit packing density and many parallel readout channels, offers a solution for high capacity data storage with fast data transfer rate. As in any data storage system, increasing the packing density increases the effect of inter-symbol interference (ISI) and inter-page interference (IPI). We describe a combination of modulation encoding/decoding and error correction that overcomes this interference allowing high packing density in the presence of noise while maintaining acceptable bit error rate (BER). We also describe an extension of the algorithm to multi-level (grayscale) encoding.
Variable threshold detection for 3D page-oriented optical data storage systems
Author(s):
Tawei Ho;
Nopparit Intharasombat;
Alexander A. Sawchuk
Show Abstract
We propose a new method to determine dynamically the threshold in volumetric (3D) page-oriented optical data storage (PODS) systems that use an incoherent (non-holographic) imaging format. In these systems, the inter-symbol interference (ISI) and inter-page interference (IPI) that occurs with very high data packing density are two major sources of error during data retrieval. Traditional readout systems based on a fixed binary decision threshold provide poor results. Our variable threshold detection method identifies the amount of interference from three dimensions for each data element (pixel) and adjusts the threshold value based on that information. In simulation results, the variable threshold method exhibits significant improvement over traditional detection methods.
Applications of optical feedback self-mixing interferometry
Author(s):
Yanguang Yu;
Huiying Ye;
Jiangtao Xi;
Joe F. Chicharo
Show Abstract
The paper reviewed the new emerging technique: optical feedback self-mixing interferometry (OFSMI) and its applications. Three different methods on measuring the linewidth enhancement factor (LEF) based on OFSMI are presented here and compared. The experimental results show that LEF can be measured by OFSMI with a simple set-up and good accuracy.
Study of dual-wavelength readout properties in volume holographic storage system
Author(s):
Kexin Chen;
Shoujun Luo;
Liangcai Cao;
Qingsheng He;
Guofan Jin
Show Abstract
Dual-wavelength method is a research focus in nonvolatile holographic storage. However, both theoretical analysis and experimental demonstration that nonlinear enlargement is inevitable during dual-wavelength readout. By analyzing the speciality of nonlinear enlarge factor, a method of choosing the suitable retrieving angle is proposed, which can prove the uniform enlarge factor and a least efficiency of 44% at a thin thickness such as 10 um to that of Bragg match. In this paper, At last, a novel scheme which achieves simultaneous dual-wavelength readout of two polarization multiplexed holograms is proposed and demonstrated by the experiment.
Study on CCD image compression and mass storage
Author(s):
Hong Liu;
Linpei Zhai;
Jihong Xiu;
Xiuying Zhao
Show Abstract
When CCD camera photographs massive images in the air, it is very important to compress and save CCD image timely and validly. This paper designs the CCD image compression and mass storage system. The one part is image compression: this paper introduces a reduced memory still image compression algorithm based on Listless Zerotree Coding (LZC). Compared with SPIHT, the approach significantly reduced memory requirement and no reducing the quality of the reconstructed image. The other part is image mass storage: this system uses a kind of special hard disk storage devices that can realize faster data transmission to SCSI (Small Computer System Interface) devices even if it separates oneself from PCs. In the faster data acquisition and storage system, data storage is a key technology. Normal approach is saving the data to mass memories, and then processing and saving the data after complete acquisition. The continuous acquisition time is restricted with the storage capacity in the normal method so that it can't receive the requirement of CCD image storage on many occasions. While its price will be geminate increasing, when we increase the storage capacity. So the approach in this paper is better one to use fast disks on data direct mass storage considering the storage capacity, read/write speed and unit cost. The result of the experiment shows that the system has compressed and saved CCD image validly, so it reached the anticipative purpose.
Improved confocal readout system for three-dimensional super-resolution in optical data storage
Author(s):
Xiaofeng Zhao;
Chengfang Li;
Hao Ruan
Show Abstract
We have proposed an improved confocal readout system to achieve three-dimensional superresolution. This improved system is based on a combination of two different annular binary phase filters, the one designed for increasing the transverse superresolution and the other for achieving axial superresolution. By adjusting the pupil parameters each pupil can be well designed. Simulation results show that with this improved system we successfully reduce the area of the central lobe of three-dimensional PSF of the read optics. Furthermore, the side-lobes are extinguished.
The correlation setting of the optical pickup head's laser beam measuring equipment
Author(s):
Liao Bangquan;
Zhang Yimo;
Zhao Qida
Show Abstract
For industrial producing, the same type of manufacturing equipment may lead to some product with different quality. In order to compare the measuring results of different machine easily and correctly we develop one kind of correlation setting method. We use a standard evaluator to evaluate 18 pieces of optical pickup head and record the data. Then we use one measuring equipment to measure the above 18 pieces of optical pickup head and record the data. Through comparing the skew R and skew T data of the above two group data, we can know the primary correlation coefficient of the skew R and skew T. If the coefficient is small or the offset is big we should set the correlation. Through modifying the correlation coefficient related terms and offset related terms, measuring and comparing again and again, we can control the correlation coefficient and offset in the range we wanted. Through correlation setting, we can compare the result of different measuring machine and we can determine the different error we can accept for different producing processes. It suggests that such kind of correlation setting is useful and necessary for industrial production.
Analysis on the light leakage of optical waveguide storage device
Author(s):
Haiyan Xie;
Zongcheng Liang;
Jiabi Chen;
Songlin Zhuang
Show Abstract
This paper deals with the theory of the light leakage from the slab waveguide. In the optical waveguide multilayer storage (WMS) device, the readout signals are come from the light leaking at the defective points. The efficiency of light leakage is an important issue in WMS device design. Along the direction of the wave propagating, the mono-layer structure can be regarded approximately as planar waveguide covered with periodic perturbation, or near one-dimensional (1-D) waveguide grating. This kind of 1-D waveguide grating has offered the essential structure for the coupling among the propagating modes and radiation modes. Through its interaction with the periodic structure, the propagating wave excites radiating waves which providing the output coupling. A perturbation technique is used to calculate the modes with different parameters in this grating structure. The ratio of power radiated into the outer media depends on the waveguide structure and the grating parameters. So the conversion efficiency from the propagating modes to the radiation modes can be optimally controlled by the choice of the structure parameters. This research provides a basic estimation in the design of WMS device.
Blind deconvolution of bi-level images with successive filtering
Author(s):
Edmund Y. Lam
Show Abstract
Many imaging systems are involved in the capture of bi-level objects such as documents and bar codes. However, due to optical aberrations and other degradations such as from motion, the resulting images are no longer bi-level. Restoration is therefore necessary to produce a nearly bi-level output, which is much more convenient for further
processing including recognition and identification. In this work, we tackle the problem using successive filtering, where each step is formulated as a quadratic programming optimization problem. This has the properties of fast convergence and good numerical stability. Simulation results show that by integrating the computation in the
imaging system, this method is able to restore weak signals.
Image acquisition and processing using a PC cluster toward real-time solar image improvement
Author(s):
Noriaki Miura;
Naoki Kodama;
Hiroshi Ohkama;
Hideaki Odagiri;
Naoshi Baba;
Hiroshi Kita;
Reizaburou Kitai;
Satoru Ueno;
Kiyoshi Ichimoto;
Takashi Sakurai
Show Abstract
This paper describes a PC-cluster-based observation system for improving the angular resolution of solar images. The system consists of two equipments separately working: one equipment realizes automatic acquisition of one hundred images at every fifteen seconds, and selects ten best images to be used in image processing. In the other one, image restoration and resolution improvement are carried out with a blind deconvolution method and a super-resolution method, respectively, using a PC cluster system. The system can take images at every fifteen seconds with high angular resolution. A test observation at the Hida Observatory confirmed a satisfactory performance of this system. The two equipments in the current hybrid system will be united in a future system that will realize image processing in pseudo-real time. A condition toward pseudo-real time processing is also investigated in this paper.
Quadrature phase-shifting interferometer using a polarization prism
Author(s):
Tomohiro Kiire;
Suezou Nakadate;
Masato Shibuya
Show Abstract
A new type of a phase-shifting interferometer is presented, where two fringe patterns in quadrature are simultaneously formed on an image sensor plane using a 1/8 wave plate and a polarization prism. The quadrature phaseshifting fringe patterns are acquired in each state plane of the interferometer. The phase calculation method with these four fringes patterns gives two phase distributions which are phase sum and difference between two states of the interferometer. Two interferometric systems will be presented, one of which uses one illuminating light and mechanically moving parts of the interferometer, and the other utilizes two illuminating light with different wavelengths. We will present the principles of the methods and some experimental verifications will be also given.
Phase-shifting digital holography using two low-coherence light sources with different wavelength
Author(s):
Yoshio Hayasaki;
Shingo Tamano;
Masaki Yamamoto;
Nobuo Nishida
Show Abstract
To observe an object shape in a light scattering medium, the low-coherence interferometry exercises its power to omit undesired light derived from multiple-light scattering. The phase-shifting digital holography is used to obtain the complex amplitude of the object from a few interference patterns. When the object has a height difference more than the wavelength of a light source, the obtained phase distribution has 2π ambiguity. Therefore, a phase-unwrapping technique is required to contour the object surface. When an object is in light-scattering media, the interference signal has much noise originating from multiple-light scattering, and therefore the phase unwrapping becomes harder. Two-wavelength interferometry set free from the unwrapping procedure. We propose a new method based on a combination of the phase-shifting digital holography, the two-wavelength interferometry, and the low-coherence interferometry. We demonstrate a topographic imaging of an object in light scattering media.
The erasable surface-relief grating for the thin film of PMMA doped with N-salicylideneaniline
Author(s):
Z. F. Lu;
Y. Liu;
Y. C. Liu
Show Abstract
The erasable holographic storage in the visible region for the thin film of PMMA doped with N-salicydeneaniline (SA) has been realized. By studying the dynamics of the grating growth, an intensity increase of the diffraction signal followed by a decrease with increasing the writing time was observed. The results demonstrated that the formation of surface-relief grating induced from pressure-driven mass transport, as a result, the resultant grating consisted of the phase and the surface-relief gratings was formed.
Study of removing striping noise in CCD image
Author(s):
Ji-hong Xiu;
Lin-pei Zhai;
Hong Liu
Show Abstract
Striping noise is the common system noise during formation of image using linear array CCD and has the character of periodicity, directivity and banding distributing. It can be caused by errors in internal calibration devices, or by slight gain/offset differences among the elements that conform the array of detectors. Striping noise covers up useful information in CCD image and brings adverse effect to image interpretation. On the basis of analyzing wavelet decomposed coefficient, the regularities of distribution about striping noise in wavelet coefficient is found, thereby the method of wavelet threshold selection which is suitable to striping noise distribution is put forward. According to Donoho's method about denoising using wavelet, the image including striping noise is processed. Comparing the power spectrum of processed image with the one of original image polluted by striping noise in frequency field, we find pulse brought by striping noise is removed and the goal which reserves image details and reduces stripes is achieved.
The structure design and data processing of simulating the stereo visual system
Author(s):
Zhang Yu
Show Abstract
This paper introduces the principle of imitating both eyes vision by CCD to make the orientation of objective come true. The math-model is established. The structure improves the precision of orientation of object's position with using least squre method to fit the curve and the mass center methods, and the size limit of CCD photosensitive unit is unaffected. Through the measure to different rectangle, circle and triangle, the precision of center orientation can be up to 2%. The experimented result shows: the two methods on the orientation of objective have characteristic of good precision and steadiness. They have no difference on the precision of orientation.
Study on the identifying of meat's visible spectrum based on BP artificial neural network
Author(s):
Xiaotian Li;
Tieqiang Zhang;
Bo Li;
Yongheng Jiang;
Binghui Liu;
Zhaokai Li
Show Abstract
A method to identify different meat by the visible and reflected spectra of meat with BP artificial neural net (BP-ANN) was introduced in this paper. The visible and reflected spectra (from 420 to 535nm) of different meat (beef and pork) were measured with fiber sensor spectrometer. A kind of ANN with a double-hidden layer was created to identify the different meat automatically. Its right ratio reaches 92.71%.
Design of video auto focusing based on image processing
Author(s):
Bo Meng;
Ming Zhu;
Chang-jin Cai
Show Abstract
In order to realize the auto focusing technique based on digital image processing, a video image processing system is designed by using high-performance digital signal processor TMS320VC5509 as the core, field programmable gate array FPGA for preprocessing of image. At the same time, it is proposed to use vector norm sum of image gray gradient as evaluation functions of digital image. It has the characteristics of good unbiasedness, powerful unimodality, etc., and can be applied to evaluation of defocusing. The hardware composition of the theory behind the auto focusing system, and the application of the evaluation function are discussed in details.
