Mount-induced transmitted wavefront distortion measurement of large slab matrix module
Author(s):
Haixian Ye;
Tingfen Cao;
Changchun Liu;
Zhao Xiong;
Haiping Chen
Show Abstract
We present a transmitted wavefront measuring system of large optic modules based on Shack Hartmann wavefront sensor, aiming to perform optical metrology for rectangular laser slabs arranged in a 4-high by 1-wide matrix. This system is developed to perform high-accuracy measurement for extremely high quality optical components needed for inertial confinement fusion (ICF) facility with wavefront accuracy better than 0.4λ (peak to valley, λ=632.8nm). Sensitivity analysis is put forward to specified tolerances of components to ensure the built system will perform as desired. Experiments results showed that added wavefront of each slab of 32 matrix modules is controlled under 1λ successfully.
Research on the photoelectric measuring method of warhead fragment velocity
Author(s):
Ji Liu;
Lixia Yu;
Bin Zhang;
Xiaoyan Liu
Show Abstract
The velocity of warhead fragment is the key criteria to determine its mutilation efficiency. But owing to the small size, larger quantity, irregular shape, high speed, arbitrary direction, large dispersion of warhead fragment and adverse environment, the test of fragment velocity parameter is very difficult. The paper designed an optoelectronic system to measure the average velocity of warhead fragments accurately. The apparatus included two parallel laser screens spaced apart at a known fixed distance for providing time measurement between start and stop signals. The large effective screen area was composed of laser source, retro-reflector and large area photo-diode. Whenever a moving fragment interrupted two optical screens, the system would generate a target signal. Due to partial obscuration of the incident energy and the poor test condition of the explosion, fragment target signal is easily disturbed. Therefore, fragments signal processing technology has become a key technology of the system. The noise of signal was reduced by employing wavelet decomposition and reconstruction. The time of fragment passing though the target was obtained by adopting peak detection algorithm. Based on the method of search peak in different width scale and waveform trend by using optima wavelet, the problem of rolling waveform was solved. Lots of fragments experiments of the different types of the warheads were conducted. Experimental results show that: warhead fragments capture rate of system is better than 98%, which can give velocity of each fragment in the density of less than 20 pieces per m2.
The influence of relative humidity on the scattered light signal of aerosol concentration measurement system
Author(s):
Fang Gu;
Jiahong Zhang;
Yunyun Chen;
Fengpin Cui;
Yi Liu;
Yuanyuan Wei;
Lei Shen
Show Abstract
Physical properties, such as density, refractive index and morphology of the aerosol particles will be changed when the relative humidity of the environment is relatively high, which leads to a significant variation of the scattered light signal collected by the single particle light scattering measurement system. If the calibration parameters in the condition of low humidity are applied to inverse aerosol mass concentration, the measurement accuracy will certainly be degraded. Therefore, the calibration parameters of the system must be corrected. In this case, the monotonic relationship between the particle size and the scattered light signal collected by the system should be considered carefully. Combining the Mie scattering theory with the humidity growth model of the particle size and the refractive index, the influence of relative humidity on the scattered light signals of spherical particles has been investigated in this paper. The results indicate that the diameters of spherical particles grow exponentially and the refractive index decreases linearly when the relative humidity is increased between 60% and 95%. Consequently, a significant change of the angular distribution of the scattering intensity occurs. The forward-scattered light is getting stronger, while the back-scattered light becomes weaker. Meanwhile, the scattered light flux of the particle within a solid angle displays exponential growth with increasing the relative humidity. Thus, the monotonous relationship between the particle size and the scattered light flux has changed significantly in the case of the high humidity, and their quadratic coefficient decreases clearly assuming the particle density invariant, which causes an obvious increase of the calibrated proportional coefficient. The results of this work provide an important theoretical guidance for the humidity correction of calibration parameters for the inversion of aerosol mass concentration by the single particle light scattering method.
Near infrared reflective shearing point diffraction interferometer for dynamic wavefront measurement
Author(s):
Wenhua Zhu;
Lei Chen;
Donghui Zheng
Show Abstract
A near infrared reflective shearing point diffraction interferometer (NIRSPDI) is designed for large-aperture dynamic wave-front measurement. The PDI is integrated on the small substrate with properly designed thin film. The wave-front under test is reflected by the front and rear surfaces of the substrate respectively to generate an interferogram with high linear-carrier frequency, which is used to reconstruct the wave-front by means of the Fourier transform algorithm. In this article, the system error and the major parameters of NIRSPDI are discussed. In addition, we give an effective method to adjust NIRSPDI for fast measurement. Experimentally NIRSPDI was calibrated by a standard spherical surface and then it was applied to the dynamic wave-front with a diameter of 400mm. The measured results show the error of whole system which verifies that the proposed NIRSPDI is a powerful tool for large-aperture dynamic wave-front measurement.
Research on adjusting and testing of off-axis paraboloid mirror with large aperture
Author(s):
Donghui Zheng;
Lei Chen;
Wenhua Zhu
Show Abstract
Off-axis paraboloid (OAP) is widely used in optical system of large diameter, such as astronomical instruments, space optics and so on, for it produce no aberration at geometric focus. It simplifies the structure of optical system, improves imaging quality, reduces the size and weight, also cost of the system. The software Zemax was used to simulate the adjustment errors including high-low and pitch, tilt and off-axis distance, and the rotation around the secondary optical axis, by taking an off-axis paraboloid mirror with the diameter of 400mm, focal length of 4000mm, and the off-axis distance of 350mm for an example. Then the corresponding experiments were performed to verify the simulation results using PhaseCam6000 interferometer of 4D technology. It proves the simulation model in correct, will play an important role in adjusting an off-axis paraboloid mirror.
High precision calibration of line structured light sensors based on linear transformation over triangular domain
Author(s):
Yuehua Li;
Jingbo Zhou;
Fengshan Huang
Show Abstract
With the advantages of easy data processing and fast measuring speed, line structured light sensors (LSLSs) have gained more and more applications. CCD camera is a core component of the sensor. The distortion of its lens will severely degrades the measuring accuracy. To enhance the measuring quality, a numerical calibration method is brought out that is based on linear transformation over triangular domain. Based on the pinhole imaging principle, a linear transformation model was established which is easy to compute the profile’s world coordinates according to its pixel coordinates over each triangular domain. The triangle domains are achieved using Delaunary triangulation via the centers of target dots. The triangle number that each center point of the laser stripe locates is determined by T-search method. A linear approximation error model to the lens distortion is also established and the approximation errors are getting larger when the interval spacing of the calibration dots increases. Measuring results show that the relative error of this proposed method in horizontal and vertical direction can reach 0.0630% and 0.0802%, respectively. The calibration error grows with the increasing of the target’s dot interval that corresponds with the trends of the linear approximation error. This further validates the proposed calibration method.
Annular sub-aperture stitching interferometry testing for large-caliber aspheric
Author(s):
Pengfei Wu;
Shuming Yang;
Lin Sun;
Pu Zhao;
Zhuangde Jiang
Show Abstract
An annular sub-aperture stitching interferometry testing is proposed for large-caliber aspheric lens testing, expanding the dynamic range of the interferometer, broadening the scope of the measurement, and reducing the cost of the measurement to a large extent without the use of compensating elements. The large-caliber aspheric is divided into several annular sub-apertures, and there are some overlapping areas between each two adjacent sub-apertures. When testing, the test aspheric is moved along the optical axis according to path planning so that the reference spherical shape and the test aspheric interest at points of common tangency to reduce the fringe density of the sub-aperture. However, in the process of moving the test optic, six DOF (degrees of freedom) misalignment errors will occur. According to the rigid body kinematics theory, the misalignment error separation model is established so that the misalignment factors can be calculated by the information of each overlapping regions. Then all sub-apertures are unified to the same reference with proper algorithm, and subsequently, misalignment error of the reference is removed by Zernike polynomial fitting, and the whole surface error is recovered. Simulation results are shown to demonstrate the feasibility of the method we developed. By analyzing the influence of the six DOF on the stitching result, the most important factor is obtained, and some measures are taken, that is, a measurement system combining two interferometers is designed, one of which is to measure the departures between the reference and the aspheric, and another to test the piston errors to be transmitted to the control system to improve the accuracy.
Synchronous two-wavelength temporal interferometry
Author(s):
Xiaoqiong Zhang;
Zhan Gao;
Jie Qin;
Guangyu Li;
Ziang Feng;
Shengjia Wang
Show Abstract
Interferometry is an optical measuring method with the character of non-destructive, high sensitivity and high accuracy. However, its measurement range is limited by the phase ambiguity. Hence the method with two separate different wavelengths light source is introduced to enlarge the measurement range.
As for the two-wavelength interferometry case, phase shifting is the traditional way to acquire the phase map, it needs to repeat the measurement twice, which means the measurement cannot be accomplished in real time. Hence to solve the problem, a temporal sequence interferometry has been used. This method can obtain the desired phase information in real time by using the Fourier transform methods of the interferogram recorded in a sequence while the object is being deformed. But, it is difficult to retrieve the phase information directly due to the multi extreme points in one period of the cosine function.
In this paper, an algorithm based on the wavelet ridge analysis is adopted to retrieve the two wavelength phase fluctuation caused by the displacement simultaneously.
The preliminary experiment is conducted and the results are compared with theoretical simulations to validate the proposed approach. The laser emits light with two wavelengths 532 nm and 473 nm, two separated interference patterns in time sequence are detected by the CCD camera in the same time. The overlapped interferograms of two colors are analyzed by this algorithm and the corresponding phase information are obtained. The maximum error value between the simulation and theory is 0.03 um and the relative error is 0.33%.
Design of a photoelectron/ion imaging spectrometer with high temporal resolution
Author(s):
Yuzhu Liu;
Yue Guan;
Kuang Ao;
Shixin Pei;
Fang Gu;
Jing Su;
Linhua Xu
Show Abstract
A conventional VMI (velocity map imaging)-TOF (time-of-flight) spectrometer is modified by adding an extra electrode. By this small modification, the longitudinal focus can be realized for TOF mass resolution while maintaining the lateral focus for optimal VMI energy resolution simultaneously. The mass-resolving power by four-electrode ion optics is greatly enhanced. Our design is especially useful in experiment with a non-focused laser beam.
Manufacture, alignment and measurement for a reflective triplet optics in imaging spectrometer
Author(s):
Liyin Yuan;
Zhiping He;
Yueming Wang;
Gang Lv
Show Abstract
Reflective triplet (RT) optics is an optical form with decenters and tilts of all the three mirrors. It can be used in spectrometer as collimator and reimager to get fine optical and spectral performances. To alleviate thermal and assembly stress deformation, opto-mechanical integrated design suggests that as with all the machine elements and the mainframe, the mirrors substrates are aluminum. All the mirrors are manufactured by single-point diamond turning technology and measured by interferometer or profilometer. Because of retro-reflection by grating or prism and reimaging away from the object field, solo three mirrors optical path of RT has some aberrations. So its alignment and measurement needs an aberration corrected measuring optical system with auxiliary plane and sphere mirrors and in which the RT optics used in four pass. Manufacture, alignment and measurement for a RT optics used in long wave infrared grating spectrometer is discussed here.
We realized the manufacture, alignment and test for the RT optics of a longwave infrared spectromter by CMM and interferometer. Wavefront error test by interferometer and surface profiles measured by profilometer indicate that performances of the manufactured mirrors exceed the requirements. Interferogram of the assembled RT optics shows that wavefront error rms is less than 0.0493λ@10.6μm vs design result 0.0207λ.
Sub-aperture stitching test of a cylindrical mirror with large aperture
Author(s):
Shuai Xue;
Shanyong Chen;
Feng Shi;
Jinfeng Lu
Show Abstract
Cylindrical mirrors are key optics of high-end equipment of national defense and scientific research such as high energy laser weapons, synchrotron radiation system, etc. However, its surface error test technology develops slowly. As a result, its optical processing quality can not meet the requirements, and the developing of the associated equipment is hindered. Computer Generated-Hologram (CGH) is commonly utilized as null for testing cylindrical optics. However, since the fabrication process of CGH with large aperture is not sophisticated yet, the null test of cylindrical optics with large aperture is limited by the aperture of the CGH. Hence CGH null test combined with sub-aperture stitching method is proposed to break the limit of the aperture of CGH for testing cylindrical optics, and the design of CGH for testing cylindrical surfaces is analyzed. Besides, the misalignment aberration of cylindrical surfaces is different from that of the rotational symmetric surfaces since the special shape of cylindrical surfaces, and the existing stitching algorithm of rotational symmetric surfaces can not meet the requirements of stitching cylindrical surfaces. We therefore analyze the misalignment aberrations of cylindrical surfaces, and study the stitching algorithm for measuring cylindrical optics with large aperture. Finally we test a cylindrical mirror with large aperture to verify the validity of the proposed method.
A novel way of squareness measurement on ultra-precision motion stage basing on the error separation
Author(s):
Tao Lai;
Xiaoqiang Peng;
Guipeng Tie;
Junfeng Liu;
Meng Guo
Show Abstract
The precision of traditional squareness measurement on ultra-precision motion stage is mostly determined by the standard component, such as bare L-square and optical pentaprism, and the measurement precision is lower than the precision of the standard component. Based on the error separation, this paper presents a novel method of squareness measurement with an optical square brick. The angles between the guide and the four lines of the section of the brick are measured, and the squareness error distraction is achieved by the truth that the internal angle sum of a tetragon is 360°. A squareness measurement test is carried out on the coordinate measuring machine (CMM) by using an optical square brick with the squareness error of 0.3°. The results show that the local squareness and uncertainties between the X axis and Y axis of the CMM are 2.5arcsec and 0.5arcsec respectively. The measurement precision is higher than the precision of the brick and the feasibility and accuracy of the method are validated.
Stochastic dual-plane on-axis digital holography based on Mach–Zehnder interferometer
Author(s):
Fengpeng Wang;
Dayong Wang;
Lu Rong;
Yunxin Wang;
Jie Zhao
Show Abstract
For traditional dual-plane on-axis digital holography, the robustness is lower because it is difficult to maintain the
stability of the phase difference between the object beam and the reference beam, and it may be invalid when the objects
are on the surface of a medium with uneven thickness. An improved dual-plane digital holographic method based on
Mach–Zehnder interferometer is presented to address these problems. Two holograms are recorded at two different
planes separated by a small distance. Then, the zero-order image and conjugated image are eliminated by Fourier domain
processing. In order to enhance the robustness of the system, the object is illuminated by a stochastic beam that is a
speckle wave produced by a diffuser. Simulated and experimental results are shown to demonstrate that the proposed
method has greater robustness than the traditional dual-plane on-axis digital holography and it can be used to imaging on
the irregular surface of a transparent medium.
Design of a compound eye system with planar micolens array and curved folded mirrors
Author(s):
Mengchao Ma;
Xicheng Gao;
Jin Zhang;
Huaxia Deng
Show Abstract
Compound eye has the merits of large FOV (Field of View), high acuity to motion and compact structure. In order to
achieve large FOV, most natural compound eyes have curved structures. However, a 3D microlens array alone cannot
work properly with a planar image sensor, as a result, very complex relay optical design is required for beam-steering
and image formation. On the other hand, artificial compound eyes with planar structure are easy to design and fabricated,
but the field of view is very small. To address this issue, an innovated design is presented in this paper. The system
comprises of a planar structured microlens array and two curved folded mirrors. A very high fill factor can be achieved
by using planar microlens array. The design was verified with Zemax simulation and preliminary experiment. The results
show that the system can achieve large FOV imaging without significant lens distortion and ghost image, demonstrating
the feasibility and flexibility of the proposed method.
Mounting of reference surface for a transmission sphere
Author(s):
Wei-Jei Peng;
Cheng-Fang Ho;
Zong-Ru Yu;
Chien-Yao Huang;
Ching-Hsiang Kuo;
Wei-Yao Hsu
Show Abstract
The mounting design of a reference surface for a 6-in transmission sphere is presented in this paper. To achieve highprecision measurement in interferometry, the reference wavefront error should be controlled within peak-to-valley (PV) 0.1 λ (λ=0.6328 um) for subtraction in calibration. The reference wavefront error includes the system aberration error and the irregularity of the reference surface. When a transmission sphere is well aligned, the reference wavefront error is dominated by the reference surface. The mounting of the reference surface is imperative because the surface deformation of the reference surface after mounting needs to be lower than 0.1 λ. Besides the mounting deformation, self-weight deformation is also considerable for large optics, such as 6-in reference surface in our study. Consequently, a semikinematic mounting is applied using three small contact areas to avoid over constraint. The transmission sphere in our study is vertically tested on QED aspheric stitching interferometer (ASI), and then the trefoil aberration is occurred. There are two methods to decrease surface deformation after mounting, including deformation correction using computer control optical surfacing (CCOS) and adding soft supporting between hard mounting. In this study, three soft supports are used to share the loads of three rigid supports and then to minimize surface deformation due to gravity. Mounting design and experiments are described in this paper. Finally, the reference wavefront error of the prototype is successfully restrained within 0.1 λ in measurement.
Sub-nanometer asphere fabrication and testing
Author(s):
Erlong Miao;
Songtao Gao;
Jian Zhang;
Dongqi Su
Show Abstract
Lithography projection objective is one of the most precise optical systems in optical manufacture field. The required accuracy of the asphere in the objective is down to nanometer and sub-nanometer, which is a great challenge for optical fabrication and testing. In this paper, the theories and technologies of sub-nanometer asphere fabrication and testing are studied and developed. Combined the sub-nanometer interference testing method and atom level polishing technologies, sub-nanometer aspheres are realized. Two kinds of testing methods are used for the measurement of the asphere and the difference of the results is less than 1nm (RMS).
3D shape reconstruction of rail and surface defect detection based on PMP
Author(s):
Fan Duan;
Jinlong Lee;
Lin Luo;
Xiaorong Gao
Show Abstract
With the rapid development of high-speed and heavy-load in modern rail transit, the abrasion and surface defect of rail
are getting serious, and the demand of measuring the rail shape and surface defect has been rising. Phase Measuring
Profilometry (PMP), due to the good characters of non-contact, high precision, easy to control automatically etc., is often
used for precise 3D shape reconstruction. In this paper, PMP technology and Stoilov phase shift algorithm are adopted,
three deformed fringe patterns of rail are collected with fixed phase shift between them, and branch cut phase
unwrapping algorithm is used, based on which the three-dimensional surface shape of the rail is reconstructed and the
artificial surface flaws are restored and measured. This method provides a good reference for the precise online detection
of the rail abrasion and surface defect.
Phase measurement profilometry based on a virtual reference plane method
Author(s):
Hongbing Ren;
Jinlong Lee;
Xiaorong Gao
Show Abstract
In Phase Measurement Profilometry(PMP), the setting of the reference plane plays an important role. It is a critical step
to capture the grating fringe projected onto the reference plane in PMP. However, it is sometimes difficult to choose and
place the reference plane in practical applications. In this paper, a virtual reference plane is introduced into PMP, with
which 3D measurement can be realized without using the physical reference plane. The virtual reference plane is
generated through extracting a partial area of the deformed fringe image that corresponds to a planar region and
employing the interpolation algorithm. The method is proved theoretically through simulation experiments, providing a
new suggestion for actual measurement by PMP.
Rapid matching of stereo vision based on fringe projection profilometry
Author(s):
Ruihua Zhang;
Yi Xiao;
Jian Cao;
Hongwei Guo
Show Abstract
As the most important core part of stereo vision, there are still many problems to solve in stereo matching technology.
For smooth surfaces on which feature points are not easy to extract, this paper adds a projector into stereo vision
measurement system based on fringe projection techniques, according to the corresponding point phases which extracted
from the left and right camera images are the same, to realize rapid matching of stereo vision. And the mathematical
model of measurement system is established and the three-dimensional (3D) surface of the measured object is
reconstructed. This measurement method can not only broaden application fields of optical 3D measurement technology,
and enrich knowledge achievements in the field of optical 3D measurement, but also provide potential possibility for the
commercialized measurement system in practical projects, which has very important scientific research significance and
economic value.
Gaussian process based intelligent sampling for measuring nano-structure surfaces
Author(s):
L. J. Sun;
M. J. Ren;
Y. H. Yin
Show Abstract
Nanotechnology is the science and engineering that manipulate matters at nano scale, which can be used to create many new materials and devices with a vast range of applications. As the nanotech product increasingly enters the commercial marketplace, nanometrology becomes a stringent and enabling technology for the manipulation and the quality control of the nanotechnology. However, many measuring instruments, for instance scanning probe microscopy, are limited to relatively small area of hundreds of micrometers with very low efficiency. Therefore some intelligent sampling strategies should be required to improve the scanning efficiency for measuring large area. This paper presents a Gaussian process based intelligent sampling method to address this problem. The method makes use of Gaussian process based Bayesian regression as a mathematical foundation to represent the surface geometry, and the posterior estimation of Gaussian process is computed by combining the prior probability distribution with the maximum likelihood function. Then each sampling point is adaptively selected by determining the position which is the most likely outside of the required tolerance zone among the candidates and then inserted to update the model iteratively. Both simulationson the nominal surface and manufactured surface have been conducted on nano-structure surfaces to verify the validity of the proposed method. The results imply that the proposed method significantly improves the measurement efficiency in measuring large area structured surfaces.
A review of relationship between optical performance and geometrical errors of freeform optics
Author(s):
Panyu Zhou;
Lingbao Kong;
Min Xu;
Jing Li
Show Abstract
Freeform has been widely applied in both imaging optics and non-imaging optics. Optical freeform surfaces can be
fabricated by ultra-precision machining process. The geometrical errors of these freeform optics can be measured by
contact or non-contact approaches. Imaging quality is one of the major criteria for imaging optics, while illumination
distribution and energy efficiency are the important performance parameters for non-imaging optics. It is necessary and
helpful to relate the geometrical errors and the optical performance of the freeform optics, so as to provide a well balance
between the machining accuracy and efficiency. This paper surveys the current research on the relationship between
optical performance and geometrical errors of optical surfaces, including the research work for the measurement of
geometrical errors of freeform surfaces, and the valuation of optical performance. It shows that there is still a lack of
research work undertaken to quantitatively analyze the relationship between the optical performance and geometrical
errors. Therefore, it is interesting to carry out some future work on the quantitative analysis of the relationship between
specific optical parameters and certain frequency surface errors.
Monitoring PMD in two-dimensional phase diagram for NRZ-DPSK systems using 0.25 bit period delay-tap sampling technique
Author(s):
Xichan Zhang;
Yunfeng Peng;
Yumin Liu;
Tonghui Ji
Show Abstract
Our study proposes a method of polarization mode dispersion (PMD) under the influence of optical signal-to-noise-ratio (OSNR) in the two-dimensional phase diagram, while the polarization mode dispersion (PMD) and optical signal-to-noise-ratio (OSNR) exist at the same time, using the controlling variable method. The study is based on 0.25 bit period delay sampling in NRZ-DPSK system, the range of the experimental optical signal-to-noise-ratio (OSNR) is from 10dB to 30dB, polarization mode dispersion (PMD) is from 0 to 20ps√km . The results show that the method can get the linear variation of polarization mode dispersion (PMD) in the two-dimensional phase diagram.
Study on the metrological performance of self-calibration angle encoder
Author(s):
Yao Huang;
Zi Xue;
Dan Qiao;
Yan Wang;
Chunran Yue;
Guixin Liu;
Zhichao Wang
Show Abstract
The self-calibration method for angle measurement is introduced, and the optimal arrangement of several equal distance
distribution groups of reading heads was proposed to realize highly effective restraint of the specified Fourier
components of angular measuring deviation in loosely restricted environment. Base on this method, a self-calibration
angle encoder system was developed using micro reading heads, glass scale disc, air bearing, and multi-channel counter.
According the method of examination of the angular measuring standard, the metrological performance of the system
was evaluated using national angle standard of China. The evaluation result revealed that the measuring deviation is
within ±1.5″, the measuring repeatability is less than 1.1″. Referring to the verification scheme of measuring
instrument for plane angle, the system can be used to calibrate the angular measuring instrument with max permissible
error worse than ±4.5″in situ.
An improved self-calibration algorithm for multilateration coordinates measuring system
Author(s):
Dongjing Miao;
Guolei Wang;
Jianshuan Li;
Mingzhao He;
Yao Kang
Show Abstract
It is difficult for the traditional self-calibration algorithm to achieve high precision calibration when measuring over a
wide range. To overcome this shortcoming, an improved self-calibration algorithm for multilateration coordinates
measuring system is proposed. Different from the traditional self-calibration algorithm, the improved algorithm preselect
certain calibration points which is fixedly mounted on stable base, the lengths between specific points are
measured precisely by laser interference method. Then the precise lengths are taken as a part of optimization objective
function, and then the system parameters are determined by iterative computation. The effectiveness of the proposed
algorithm is verified by simulations and experiments. The results show that by using the improved algorithm, the max
error is only 8.9μm, the improved algorithm helps to improve the accuracy of the multilateration system significantly.
High resolution aspheric surface measurement technology based on laser interferometer
Author(s):
Xiaofei Diao;
Zi Xue;
Yanhui Kang
Show Abstract
In order to develop an aspheric surface measurement standard device to provide reliable and traceable measurement and
calibration, a high resolution aspheric surface measurement technology based on laser interferometer is proposed in this
paper. A laser interferometer with frequency stabilized He-Ne laser is used to provide traceable measurements. The
standard device would provide calibrations for different kinds of aspheric surface, therefore the interferometer used in
the standard device would be influenced by various factors, such as roughness, reflectivity, material and slope angle. The
influences of reflectivity and roughness are analyzed. A compensation method based on the analysis is applied in the
signal processing system to reduce the influences of reflectivity and roughness. An objective lens is used to collect the
measurement beam reflected from the target. The laser interferometer is set up and tested under different conditions: the
reflectivity is 1%~100%, the surface roughness is 0.012~0.8μm. Experimental results show that the measurement
resolution of the developed interferometer is at the nanometer level.
Distributed pavement subgrade shape monitoring based on FBG sensing technique
Author(s):
Zhiguo Chen;
Boshi Wang;
Wanqiu Liu;
Zhigang Wei
Show Abstract
It is often difficult to monitor the subgrade performance of an in service highway structure due to its depth and large in size. Traditional sensors for pavement performance monitoring are usually point-wise sensors and therefore cannot fulfill the requirement for large coverage. This paper introduces a shape measurement sensor based on Fiber Bragg Grating (FBG) sensing technique for pavement structure developed by our research group. It can provide large-scale layer shape measurement using only one FBG sensing element and can bear the high compaction force and high temperature during pavement construction. The proposed sensor has been test in lab to show high accuracy in measurement. In the construction of the He-da highway in Jilin province, the proposed sensor has been applied to monitor the subgrade performance for the first time. Ten sets of the sensors with individual length of about 15 m have been embedded and the performance data have been collected twice. The embedding process and monitoring data will be introduced and discussed. The results have shown the potential of the proposed sensor for future large scale application.
Study on high-precision measurement of long radius of curvature
Author(s):
Dongcheng Wu;
Shijun Peng;
Songtao Gao
Show Abstract
It is hard to get high-precision measurement of the radius of curvature (ROC), because of many factors that affect the measurement accuracy. For the measurement of long radius of curvature, some factors take more important position than others'. So, at first this paper makes some research about which factor is related to the long measurement distance, and also analyse the uncertain of the measurement accuracy. At second this article also study the influence about the support status and the adjust error about the cat’s eye and confocal position. At last, a 1055micrometer radius of curvature convex is measured in high-precision laboratory. Experimental results show that the proper steady support (three-point support) can guarantee the high-precision measurement of radius of curvature. Through calibrating the gain of cat's eye and confocal position, is useful to ensure the precise position in order to increase the measurement accuracy. After finish all the above process, the high-precision long ROC measurement is realized.
Ultra-high accuracy point diffraction interferometer: development, acccuracy evaluation and application
Author(s):
Jie Yu;
Haitao Zhang;
Chunshui Jin;
Dongmei Ma;
Hui Wang;
Zengxiong Lu
Show Abstract
Phase-shifting Point Diffraction Interferometer (PSPDI) utilizing nearly perfect spherical wavefront diffracted by a
pinhole as reference wavefront, which diminishes the influence of reference optics used in traditional interferometers,
has been developed with high accuracy, repeatability and reproducibility. Accuracy of PSPDI is mainly limited by the
quality of diffracted reference wavefront. We analyze the quality of diffracted reference wavefront by using of Rayleigh-
Sommerfeld diffraction theory and performed FDTD numerical simulation. Based on analysis, we have developed a
phase-shifting point diffraction interferometer. Ultra-precise pinhole alignment technical, high stable mount, high stable
testing environment and error source insensitive data processing algorithm was used to achieve high stability and
accuracy. Via accuracy evaluation, a deep sub-nanometer system error of developed PSPDI is obtained. A cross
comparison of PSPDI measurement and measurement of another kind of interferometer was done, and the difference was
0.16nmRMS. The developed PSPDI has been applied in spherical mirror testing and EUV projection objective testing.
Dynamics of spiral patterns in gas discharge detected by optical method
Author(s):
Fan Yang;
Mingyi Wang;
Shuhua Liu
Show Abstract
The dynamics behavior of spiral patterns is investigated in gas discharge using optical method. Rich kinks of spiral patterns are obtained and the formation and evolution process is investigated. The process of pattern formation is breakdown → hexagon → bee comb-like → strip → spiral → chaos. Spiral pattern always formed after the strip pattern. It is found that the temperature of the water electrodes plays an important role in the spiral patterns formation. When it exceeds 20°C no spiral has been obtained. The discharge current waveform and the emission spectrum of the discharge have been measured when the filaments self-organized in spiral pattern. Electron excited temperature of forming spiral pattern is calculated using intensity ratio method. It is found that the electron excited temperature of spiral pattern increase as the power supply frequency increased. Relation between wavelength and discharge parameter has been measured. It shows that the wavelength of spiral pattern increases as the discharge gap increases, and decreases as the air ratio mixed in argon increases. Accompanying measurements proved that the wavelength is approximately linear to the square root of the spiral rotating period .This work has useful reference value for studying pattern dynamics.
Research on testing system for optical surface based on polarizing coherent technology
Author(s):
De-wei Huang;
Min Wang;
Fen Wang
Show Abstract
The optical surface deviation of the lens can directly affect the quality of the optical system. In order to improve efficiency and accuracy of optical surface detection, an on-line testing system for optical surface based on polarizing coherent technology is designed and developed. No lying walls are required for the lens. In other words, they can be checked out the deviation of radius of curvature and astigmatism online. Based on the Tyman-Green interference light path, the system joins the polarization interference measuring technology. This paper makes a theoretical derivation and ZEMAX software simulation on the light path, sets up the experimental light path of the system. At last, comparison on image of Tyman-Green interference technology, the contrast of interference fringe image is improved significantly after joining polarizing coherent technology. And background noise and stray light are significantly reduced. It provides the foundation for improving the precision of image processing.
A phase retrieval algorithm based on color-frequency encoding for fringe reflection technique
Author(s):
Suodong Ma;
Bo Li
Show Abstract
Free-form optics have a wide range of applications since they can simplify the structure of an optical system, meanwhile significantly improving the system performance. Compared to optics with traditional profiles, optical testing for freeform surface is more difficult. Although a laser interferometer can reach the surface measurement precision in nanometer scale, it has problems of a limited measurement range, a complex system configuration and relatively high requirements of working conditions. Fringe reflection technique (FRT) is gradually becoming a powerful tool for free-form surface testing owing to its advantages of simple system structure, high measurement accuracy, large dynamic range, etc. However, multiple groups of fringe images are required to display in two orthogonal directions respectively during the FRT measurement to obtain the corresponding surface gradient information. It hinders the fast detection of free-form surface to a certain extent. In order to overcome the above shortcoming, a phase retrieval algorithm based on color-frequency encoding for FRT is proposed in this paper, which can achieve the absolute phase meanwhile reducing the required number of fringe images for measurement. Experimental results demonstrate the effectiveness of the proposed method.
Spectrum synthesis for a spectrally tunable light source based on a DMD-convex grating Offner configuration
Author(s):
Suodong Ma;
Qiao Pan;
Weimin Shen
Show Abstract
As one kind of light source simulation devices, spectrally tunable light sources are able to generate specific spectral shape and radiant intensity outputs according to different application requirements, which have urgent demands in many fields of the national economy and the national defense industry. Compared with the LED-type spectrally tunable light source, the one based on a DMD-convex grating Offner configuration has advantages of high spectral resolution, strong digital controllability, high spectrum synthesis accuracy, etc. As a key link of the above type light source to achieve target spectrum outputs, spectrum synthesis algorithm based on spectrum matching is therefore very important. An improved spectrum synthesis algorithm based on linear least square initialization and Levenberg-Marquardt iterative optimization is proposed in this paper on the basis of in-depth study of the spectrum matching principle. The effectiveness of the proposed method is verified by a series of simulations and experimental works.
Test technology on divergence angle of laser range finder based on CCD imaging fusion
Author(s):
Sheng-bing Shi;
Zhen-xing Chen;
Yao Lv
Show Abstract
Laser range finder has been equipped with all kinds of weapons, such as tank, ship, plane and so on, is important component of fire control system. Divergence angle is important performance and incarnation of horizontal resolving power for laser range finder, is necessary appraised test item in appraisal test. In this paper, based on high accuracy test on divergence angle of laser range finder, divergence angle test system is designed based on CCD imaging, divergence angle of laser range finder is acquired through fusion technology for different attenuation imaging, problem that CCD characteristic influences divergence angle test is solved.
Test method on infrared system range based on space compression
Author(s):
Zhen-xing Chen;
Sheng-bing Shi;
Fu-li Han
Show Abstract
Infrared thermal imaging system generates image based on infrared radiation difference between object and background
and is a passive work mode. Range is important performance and necessary appraised test item in appraisal test for
infrared system. In this paper, aim is carrying out infrared system range test in laboratory , simulated test ground is
designed based on object equivalent, background analog, object characteristic control, air attenuation characteristic,
infrared jamming analog and so on, repeatable and controllable tests are finished, problem of traditional field test method
is solved.
Test technology on CCD anti-sunlight jamming based on complex circumstance
Author(s):
Sheng-bing Shi;
Zhen-xing Chen;
Fu-li Han
Show Abstract
Visible-light reconnaissance device based on CCD is applied to all kinds of weapons, CCD cannot work because of
saturation when it faces intense light. Sun is intense light source in nature and assignably influences CCD performance.
In this paper, aim is appraising CCD anti-sunlight ability, object reflection characteristic test system is designed, based
on typical background reflection characteristic including grant, sand and so on, complex circumstance is formulated and
test project is optimized with orthogonal design method, problem that is without test technology on CCD anti-sunlight
jamming is solved.
Longitudinal electron bunch diagnostics using coherent transition radiation at the IRFEL
Author(s):
T. Y. Zhou;
Y. L. Yang;
B. G. Sun;
L. L. Tang;
P. Lu;
Z. R. Zhou;
F. F. Wu;
X. Y. Liu
Show Abstract
A longitudinal electron bunch diagnostics system is developing to measure the longitudinal bunch charge distribution for the new IRFEL at National Synchrotron Radiation Laboratory (NSRL). We use a Martin-Puplett interferometer, which is essentially a Michelson interferometer, to measure the spectrum of the coherent transition radiation produced by electrons through a thin metallic foil. Frequency components of coherent transition radiation have a relationship with the bunch form factor, which is described by the square modulus of the Fourier transform of the bunch distribution. Then several techniques, including a Kramers-Kronig analysis, have been applied to determine the longitudinal bunch charge distribution. The details of the design and theoretical investigation will be described in this paper.
Calibration of transition matrix of coordinate system for the aurora imager
Author(s):
Quanfeng Guo;
Fei He;
Yang Liu;
Yusheng Qin;
Xu Li
Show Abstract
When the meteorological satellite exploring geospace, it is necessary to confirm the imager attitude in inertial coordinate system in order to calculate the geographic situation of imaging target. In this paper, the calibration methods of the space coordinate system are described. The transformation matrix characteristics in the various methods are compared. At last the transformation matrix between aurora imager coordinates and satellite coordinates is measured by an efficient method. The results show that the calibration accuracy of the method is better than 1 arc second.
Optimal visual simulation of the self-tracking combustion of the infrared decoy based on the particle system
Author(s):
Qi Hu;
Jin Duan;
LiNing Wang;
Di Zhai
Show Abstract
The high-efficiency simulation test of military weapons has a very important effect on the high cost of the actual combat test and the very demanding operational efficiency. Especially among the simulative emulation methods of the explosive smoke, the simulation method based on the particle system has generated much attention. In order to further improve the traditional simulative emulation degree of the movement process of the infrared decoy during the real combustion cycle, this paper, adopting the virtual simulation platform of OpenGL and Vega Prime and according to their own radiation characteristics and the aerodynamic characteristics of the infrared decoy, has simulated the dynamic fuzzy characteristics of the infrared decoy during the real combustion cycle by using particle system based on the double depth peeling algorithm and has solved key issues such as the interface, coordinate conversion and the retention and recovery of the Vega Prime’s status. The simulation experiment has basically reached the expected improvement purpose, effectively improved the simulation fidelity and provided theoretical support for improving the performance of the infrared decoy.
Design of near-infrared single photon detector at 1550nm wavelength
Author(s):
Jiali Gao
Show Abstract
Technology of near-infrared single photon detection is used in quantum communication, laser ranging and weak light detection. Present single photon detectors are usually expensive and bulky. To overcome their disadvantages, a hand-held single photon detector based on InGaAs/InP avalanche photo diode (APD) is developed. A circuit program for temperature control and bias voltage is offered. The gating signal is generated and the avalanche signal is extracted by FPGA. Experiment results show that, the single photon detector yields only 8.2×10-6/ns dark count rate (DCR) when photon detection efficiency is 12%, and the maximum photon detection efficiency of 16% is obtained at temperature of -55°C.
Experimental research of improved subaperture stitching method able to eliminate high-order defocus error
Author(s):
Quan Zheng;
Lei Chen;
Le Song;
Zhigang Han
Show Abstract
Subaperture stitching is often adopted when measuring large size optic with interferometry method. To reduce the error of defocus in the process of stitching, an improved subaperture stitching method which can eliminate the high-order defocus error is presented based on the experimental study of defocused wavefront. Through detecting the wavefront difference with variable defocus, the actual defocus wavefront is proposed to replace the traditional paraboloid defocus basement so as to realize eliminating high-order defocus. A reflector sample is tested, the roughness parameter Ra is 1.252nm and 0.403nm respectively using the paraboloid and the actual decocus wavefront as the basement. The amendatory defocus basis is taken into the subaperture stitching process, for the two subaperture wavefront, different area of the actual defocus wavefront is used. A SiC super-smooth surface is measured with the improved subaperture stitching method, the Ra is 0.236nm after eliminating high-order defocus. Results show that it is a useful way to erase high-order defocus error without changing the low frequency information of test wavefront.
Design of an ultraviolet fluorescence lidar for biological aerosol detection
Author(s):
Zhimin Rao;
Dengxin Hua;
Tingyao He;
Jing Le
Show Abstract
In order to investigate the biological aerosols in the atmosphere, we have designed an ultraviolet laser induced fluorescence lidar based on the lidar measuring principle. The fluorescence lidar employs a Nd:YAG laser of 266 nm as an excited transmitter, and examines the intensity of the received light at 400 nm for biological aerosol concentration measurements. In this work, we firstly describe the designed configuration and the simulation to estimate the measure range and the system resolution of biological aerosol concentration under certain background radiation. With a relative error of less than 10%, numerical simulations show the system is able to monitor biological aerosols within detected distances of 1.8 km and of 7.3 km in the daytime and nighttime, respectively. Simulated results demonstrate the designed fluorescence lidar is capable to identify a minimum concentration of biological aerosols at 5.0×10-5 ppb in the daytime and 1.0×10-7 ppb in the nighttime at the range of 0.1 km. We believe the ultraviolet laser induced fluorescence lidar can be spread in the field of remote sensing of biological aerosols in the atmosphere.
Dual-wavelength retinal image registration based on vessel segmentation and optic disc detection
Author(s):
Yong-li Xian;
Yun Dai;
Chun-ming Gao;
Rui Du
Show Abstract
The dual-wavelength retinal image registration is one of the critical steps in the spectrophotometric measurements of
oxygen saturation in the retinal vasculature. The dual-wavelength images (570 nm and 600 nm) are simultaneously
captured by dual-wavelength retinal oximeter based on commercial fundus camera. The retinal oxygen saturation is
finally measured after vessel segmentation, image registration and calculation of optical density ratio of the two images.
Because the dual-wavelength images are acquired from different optical path, it is necessary to go through image
registration before they are used to analyze the oxygen saturation. This paper presents a new approach to
dual-wavelength retinal image registration based on vessel segmentation and optic disc detection. Firstly, the multi-scale
segmentation algorithm based on the Hessian matrix is used to realize vessel segmentation. Secondly, after optic disc is
detected by convergence index filter and the center of the optic disc is obtained by centriod algorithm, the translational
difference between the images can be determined. The center of the optic disc is used as the center of rotation, and the
registration based on mutual information can be achieved using contour and gray information of vessels through
segmented image. So the rotational difference between the images can be determined too. The result shows that the
algorithm can provide an accurate registration for the dual-wavelength retinal image.
Research of errors and fabrication method for cylindrical hologram phase grating as standard in interferometric stylus profiler
Author(s):
Hang Zha;
Xinrong Chen;
Chaoming Li;
Xiaoyang Li;
Jian Yu
Show Abstract
The stylus profiler is a conventional instrument in surface topography measurement. The interferometric stylus profiler which uses cylindrical phase grating as standard obtains the surface topography information via measuring the changes of phase. In this way, it is apt to realize wider range, higher accuracy and higher resolution simultaneously in topography measurement. Currently, cylindrical phase grating is ordinarily fabricated by means of holographic record. Subject to the present method and technics, the microstructure parameters of the grating, such as spatial frequency, groove depth and duty cycle can hardly been uniform in every area of grating. Concerning the working principle of interferometric stylus profiler with cylindrical phase grating as sensor, the quality of cylindrical hologram phase grating (80mm in radius of curvature, 1200lp/mm in center spatial frequency) is analyzed comprehensively in this paper. Effects of the inconsistency distribution of microstructure parameter of grating over cylinder surface on the phase difference between ±1st order diffraction wave-fronts in different incidence angle are discussed in detail. The theoretical analysis and numerical calculation results show that: the holographic recording parameters determine the distribution of spatial frequency of cylindrical hologram phase grating; the inconsistency of spatial frequency on the cylinder surface is the primary cause affecting measurement accuracy; the inconsistency of duty cycle of grating will have influence on measurement accuracy when the incidence angle is not equal to zero (i.e.in a small incidence angle). Therefore, the process tolerances of cylindrical phase grating are presented and a new fabrication method of high precision cylindrical phase grating is proposed.
Improved coded exposure for enhancing imaging quality and detection accuracy of moving targets
Author(s):
Baoqi Mao;
Li Chen;
Lin Han;
Weimin Shen
Show Abstract
The blur due to the rapidly relative motion between scene and camera during exposure has the well-known influence on the quality of acquired image and then target detection. An improved coded exposure is introduced in this paper to remove the image blur and obtain high quality image, so that the test accuracy of the surface defect and edge contour of motion objects can be enhanced. The improved exposure method takes advantage of code look-up table to control exposure process and image restoration. The restored images have higher Peak Signal-to-Noise Ratio (PSNR) and Structure SIMilarity (SSIM) than traditional deblur algorithm such as Wiener and regularization filter methods. The edge contour and defect of part samples, which move at constant speed relative to the industry camera used in our experiment, are detected with Sobel operator from the restored images. Experimental results verify that the improved coded exposure is better suitable for imaging moving object and detecting moving target than the traditional.
Three-dimensional profile reconstruction based on infrared multi-view vision
Author(s):
Shuqi Zhao;
Zhimin Zhang;
Xiong Wan
Show Abstract
Multi-view vision technology is use of multiple images to reconstruct three-dimensional (3D) information of the research object, and the images were captured with more than two cameras from different angles. This technology has the advantages of high efficiency, simple structure and low cast. It is very suitable for on line noncontact product test and quality control. The existent multi-view vision technology is focus on the visible information, thus it is easy to be influenced by the testing environment (weather, background, light etc.), so it’s application field has some limitations. However, in the field of medical diagnostic technology, infrared vision technology reflects its advantages, like determining whether the tissue lesions by observe certain parts temperature distribution of the body. This paper is studied on infrared Multi-vision which is based on visible binocular vision theory. Firstly, obtained the intrinsic parameter and external parameter of each infrared thermal imager by Zhang’s calibration method; Secondly, taken infrared images from different angles, then combined the infrared images two by two to do feature point detecting and matching in order to find the points to be reconstructed; Finally, reconstructing 3D profile information based on calculating point clouds of the spatial coordinates.
Research on measurement of center thickness of the lens with a hole
Author(s):
Linchao Zhang;
Xiaoming Wu;
Haozhao Li;
Hongxiao Sun
Show Abstract
In the field of modern optical measurement, the center thickness is a basic parameter of the optical lens, which will directly, affects the accuracy of the lens’ focal length and other optical parameters, and these parameters have great influence on overall performance of the optical system. Therefore center thickness requires precision test. Nowadays, the methods include contact measurement and non-contact measurement. Generally speaking, the center thickness of the lens with no hole in the center only could be measured through the both methods. The lens with a hole in the center is used widely, on the basis of principle of contact measurement, a method of measuring center thickness of the lens with a hole is proposed. A sign convention about radius and sagitta of curvature is defined and the geometrical expressions are derived in detail. Analyses and simulations between the errors of center thickness and variables are shown. To prove the right of the method, an experiment is done in use of a lens with no hole in the center. The results of indirect and direct measurements are presented, respectively. In comparison of direct measurement, the proposed method has a high precision.
Research on effects of baffle position in an integrating sphere on the luminous flux measurement
Author(s):
Fangsheng Lin;
Tiecheng Li;
Dejin Yin;
Lei Lai;
Ming Xia
Show Abstract
In the field of optical metrology, luminous flux is an important index to characterize the quality of electric light source.
Currently, the majority of luminous flux measurement is based on the integrating sphere method, so measurement
accuracy of integrating sphere is the key factor. There are plenty of factors affecting the measurement accuracy, such as
coating, power and the position of light source. However, the baffle which is a key part of integrating sphere has
important effects on the measurement results. The paper analyzes in detail the principle of an ideal integrating sphere.
We use moving rail to change the relative position of baffle and light source inside the sphere. By experiments, measured
luminous flux values at different distances between the light source and baffle are obtained, which we used to take
analysis of the effects of different baffle position on the measurement. By theoretical calculation, computer simulation
and experiment, we obtain the optimum position of baffle for luminous flux measurements. Based on the whole luminous
flux measurement error analysis, we develop the methods and apparatus to improve the luminous flux measurement
accuracy and reliability. It makes our unifying and transferring work of the luminous flux more accurate in East China
and provides effective protection for our traceability system.
A robust color image fusion for low light level and infrared images
Author(s):
Chao Liu;
Xiao-hui Zhang;
Qing-ping Hu;
Yong-kang Chen
Show Abstract
The low light level and infrared color fusion technology has achieved great success in the field of night vision, the technology is designed to make the hot target of fused image pop out with intenser colors, represent the background details with a nearest color appearance to nature, and improve the ability in target discovery, detection and identification. The low light level images have great noise under low illumination, and that the existing color fusion methods are easily to be influenced by low light level channel noise. To be explicit, when the low light level image noise is very large, the quality of the fused image decreases significantly, and even targets in infrared image would be submerged by the noise. This paper proposes an adaptive color night vision technology, the noise evaluation parameters of low light level image is introduced into fusion process, which improve the robustness of the color fusion. The color fuse results are still very good in low-light situations, which shows that this method can effectively improve the quality of low light level and infrared fused image under low illumination conditions.
The influence of low light level ICCD image on low light level and infrared image fusion
Author(s):
Qing-ping Hu;
Xiao-hui Zhang;
Chao Liu
Show Abstract
The fusion of low light level and infrared images can synthesize the advantages of low light level imaging and infrared imaging, to make the details of the scene and targets richer. The quality of low light level and infrared images are the prerequisites to ensure the quality of fused image. The quality of low light level image is vulnerable to target contrast, light distribution and environmental illumination, especially under low illumination, low light level image noise significantly increased, image quality degradation, but the infrared image is not influenced by environmental illumination. In this paper, the influence of low light level image quality on low light level and infrared image fusion was analyzed from several aspects, such as target contrast, light distribution and ambient illumination, which can analysis the quality of low light level and infrared fused image.
Online evaluation system for the photo-physical properties of organic photoelectric materials and device integrated with the device fabrication instrument
Author(s):
Hongyan Zhang;
Lingqiang Meng;
Weimin Liu;
Pengfei Wang
Show Abstract
Organic photoelectric materials have showing a wide application prospect in the fields of energy, environment, information and biology because of their unique advantages. However, it is still not clear for us to understand some basic photo-physical processes (i.e. energy transfer, charge transfer, charge separation and recombination, etc.), which has affected the performance of materials and devices. This is very incompatible with the rapidly growing demand of the organic photoelectric materials and devices, and it has been one of the core problems that constraints the further applications of organic photoelectric materials and devices. The lack of the necessary systems and means is a major reason. Thus, it is a very necessary urgent task to develop new methods and technologies to evaluate the photo-physical properties of organic photoelectric materials and equipment systems. In this paper, an on-line research system for photo-physical properties is established to detect the intrinsic character of the organic photoelectric materials and devices, which integrates the fabrication instrument of the film materials and devices with the online measuring equipment combing with the high vacuum technology and the steady state transient spectrum measurement. A standard OLED device was fabricated and the electrluminescence spectra, current density, brightness, current efficiency and the power efficiency were got using this system avoiding the affect of the air and water. The results indict this system not only plays an important promoting role for the theoretical research of organic photoelectric materials and devices, but also helps improving the research level of organic photoelectric materials and devices. This work is expected to produce some potential innovating results with the international advanced level and make contributions to needs of national strategy.
Alignment and measurement for back-end optical system of quantum communication
Author(s):
Qi-rui Xu;
Bin Fan
Show Abstract
This paper introduced the method of alignment and measurement for back-end optical system of quantum communication ground station. The alignment methods of important components of system such as 20 constriction multiplicator, single photon detector mechanism and so on were introduced at first. The alignment method of the key receiving optical path and the entanglement receiving optical path which were integrated into coaxial multi optical path with other three optical paths were described in detail. Finally the back-end optical system was tested indoors with an optical power meter and a collimator. The results shows that the quantum key signal (@850nm) receiving efficiency is 27.6%, the average polarization contrast is better than 320:1, the receiving efficiency of quantum entanglement signal (@810nm) was 28.6%, and the average polarization contrast is better than 180:1.
Performance test and image correction of CMOS image sensor in radiation environment
Author(s):
Congzheng Wang;
Song Hu;
Chunming Gao;
Chang Feng
Show Abstract
CMOS image sensors rival CCDs in domains that include strong radiation resistance as well as simple drive signals, so it is widely applied in the high-energy radiation environment, such as space optical imaging application and video monitoring of nuclear power equipment. However, the silicon material of CMOS image sensors has the ionizing dose effect in the high-energy rays, and then the indicators of image sensors, such as signal noise ratio (SNR), non-uniformity (NU) and bad point (BP) are degraded because of the radiation. The radiation environment of test experiments was generated by the 60Co γ-rays source. The camera module based on image sensor CMV2000 from CMOSIS Inc. was chosen as the research object. The ray dose used for the experiments was with a dose rate of 20krad/h. In the test experiences, the output signals of the pixels of image sensor were measured on the different total dose. The results of data analysis showed that with the accumulation of irradiation dose, SNR of image sensors decreased, NU of sensors was enhanced, and the number of BP increased. The indicators correction of image sensors was necessary, as it was the main factors to image quality. The image processing arithmetic was adopt to the data from the experiences in the work, which combined local threshold method with NU correction based on non-local means (NLM) method. The results from image processing showed that image correction can effectively inhibit the BP, improve the SNR, and reduce the NU.
The analysis of measurement accuracy of the parallel binocular stereo vision system
Author(s):
Huan Yu;
Tingwen Xing;
Xin Jia
Show Abstract
Parallel binocular stereo vision system is a special form of binocular vision system. In order to simulate the human eyes observation state, the two cameras used to obtain images of the target scene are placed parallel to each other. This paper built a triangular geometric model, analyzed the structure parameters of parallel binocular stereo vision system and the correlations between them, and discussed the influences of baseline distance B between two cameras, the focal length f, the angle of view ω and other structural parameters on the accuracy of measurement. This paper used Matlab software to test the error function of parallel binocular stereo vision system under different structure parameters, and the simulation results showed the range of structure parameters when errors were small, thereby improved the accuracy of parallel binocular stereo vision system.
Fresnel incoherent correlation holography and its imaging properties
Author(s):
Zhipeng Wang;
Haotong Ma;
Ge Ren;
Zongliang Xie;
Huan Yu
Show Abstract
The incoherent digital holography makes it possible to record holograms under incoherent illumination, which lowers requirement for the coherence of light sources and results in expanding its application to white-light and fluorescence illuminating circumstances. The Fresnel Incoherent Correlation Holography (FINCH) technology achieves diverging the incident beam and shifting phase by mounting phase masks on the phase modulator. Then it obtains holograms with phase difference and reconstructs the image. In this paper, we explain the principles of the FINCH technology, and introduce the n-step phase-shifting method which is utilized to eliminate the twin image and bias term in holograms. During the research, we studied what impact the term n may have on imaging performance, compared imaging performances when different phase masks are mounted on SLM, and established simulation system on imaging with which imaging performances are deeply inspected. At last, it is shown in the research that the FINCH technology could record holograms of objects, from which clear images could be reconstructed digitally.
A new multi-probe scanning method for measuring optical surface
Author(s):
Dede Zhai;
Ziqiang Yin;
Shanyong Chen;
Fujing Tian
Show Abstract
In form metrology, multi-probe scanning method based on error separation technique can be used successfully to
eliminate motion error of slideway. Due to high repeatability of flexure hinge, a virtual multiple sensor concept is
presented. The system employs a single probe with the accurate movement of flexure hinge to achieve virtual multiprobe.
This single probe scanning method can realize and extend the function of multiple-probe method. This paper
describes the principle of this new method; Measurement process of method is modeled and the predefined test curve is
reconstructed by the application of simultaneous equation and least-squares methods. It shows that scanning systems
with virtual multiple sensors allow the influence of random and systematic errors to be reduced. We also conducted the
experiment repeatedly to measure the profile of workpiece. It shows that reconstructed curves in each experiment are
nearly superposed.
Different environmental conditions from the effects of repetitive fixed focus lens of long focal distance
Author(s):
Yuan Quan;
Lin Zhang;
Huan Ren;
Yi Yang;
Zhen-dong Shi;
Hua Ma;
Ke Ma;
Yu-rong Ma;
Xiao-xuan Feng
Show Abstract
In many long focal distance lens focal length detection method, laser confocal combined focal length measurement with
ultra high focusing accuracy, more and more attention and application. The accurate measurement of the distance
between the lens focus and the focus in the measurement process is the key to improve the accuracy of the whole
measurement. By repeating the measurement of focal distance under different environmental conditions, the results of
repeated measurements of influenced by the environmental conditions. The results show that air disturbance is the
measurement repeatability factors having the greatest impact, for better use of the equipment and in the equipment
development research foundation laid the foundation.
Accuracy decline of the Brillouin optical time-domain analysis system induced by self-phase modulation
Author(s):
Yuqing Zhou;
Wei Chen;
Zhou Meng
Show Abstract
The Brillouin optical time-domain analysis system (BOTDA) is a distributed optical fiber sensing system based on the
measurement of the effective Brillouin gain, in which high power pumping pulse is demanded to fulfill optical time
domain reflectometry (OTDR) spatial orientation. As for strict rectangular pulse, BGS can maintain Lorentz line profile
along the sensor fiber, while the actual rectangular pulse has power transients like the rising edge and failing edge,
making BGS broadened or even distorted by the effect of self-phase modulation (SPM), which will induce the decline of
the measuring accuracy. A model concerning the effects of pumping pulse power transients on the BGS by means of
SPM is established based on the nonlinear Schrodinger equation (NLSE) in regular single mode fiber (SMF).
Research on auto-centering device in surface defects evaluation system of large spherical optics
Author(s):
Yihui Zhang;
Yongying Yang;
Fan Wu;
Huiting Chai;
Kai Yan;
Lin Zhou;
Yang Li;
Dong Liu;
Jian Bai;
Yibing Shen;
Pin Cao
Show Abstract
For the Spherical Surface Defects Evaluation System (SSDES), lens centering is essential to obtain the precise scanning trace and defect features without mismatch. Based on a combination of auto-collimating microscopy and Computer-Aided Alignment (CAA), an auto-centering system that can measure the deviation of large spherical center with respect to a reference rotation axis rapidly and accurately is established in this paper. The auto-centering system allows the closedloop feedback control of spherical center according to the different images of the crosshair reticle on CCD. Image entropy algorithm is employed to evaluate image clarity determined by the auto-focus experiment of 50μm step-length. Subsequently, an improved algorithm that can search the crosshair center automatically is proposed to make the trajectory of crosshair images and the position of rotation axis more reliable based on original circle fitting algorithm by the least square method (LSM). The comparison results indicates to show the high accuracy and efficiency of the proposed fitting method with LSM.
Design on electromagnetic actuator of aerostatic bearing stylus displacement sensor
Author(s):
Junwei Wang;
Suping Chang;
Xiaojun Liu;
Wenlong Lu;
Yanling Sun;
Chunbing Hu
Show Abstract
This paper discusses electromagnetic force actuator and configuration design of the aerostatic bearing stylus displacement sensor for the surface topography measurement. This stylus displacement sensor is designed based on the structure of direct metrology of stylus displacement, and aerostatic bearing is utilized to achieve the precise linear movement of stylus, with which the profiler measurement system has high precision without non-linear error. During the measurement process, the attitude of the stylus is adjusted by electromagnetic force to control the contact force between stylus and surface, thus the electromagnetic force analysis and implement is the key component to support the constant measurement force. The electromagnetic actuator combined permanent magnet with coils is designed to achieve the electromagnetic force precisely. The results of the numerical analysis and experiments indicate that the electromagnetic actuator can balance the gravity of stylus and keep a constant contacting force during the measurement. The surface topography measurement system based on aerostatic bearing stylus displacement sensor is constructed and the primarily experiment result is also given.
A method based on reflection theory to test the attenuation performance of an absorption coat to 8mm waves
Author(s):
Xuanyu Wang
Show Abstract
A testing method has been set up to evaluate the attenuation performance of an absorption coat to 8mm waves, which is based on a set of detecting system included by an 8mm wave emitter, a millimeter power meter, a point to point collimator and a reflecting plate. The power meter was aimed at the 8 mm wave emitter along the reflection optical path instead of the direction observation between incident and reflected millimeter wave. Some Al, Fe and aluminum alloy sample plates were made and painted by the dope which was complexed with chopped carbon fibers. A naked metal plate was first used to adjust the transmission path of the millimeter wave. Then the power meter was adjusted to phase locking after preheating, and the millimeter wave power was sampled as the background value. Then the other painted plates were tested under the same conditions. When the concentration of chopped carbon fibers is 0.5mg/ml and the thickness of the absorption coat is 0.5mm, the attenuation percentages of Al, Fe and aluminum alloy painted plates respectively is 54.29%, 58.31% and 41.12%. By the result, the reflection testing method may be widely used to measure the reflection capacity or attenuation performance of various surfaces to millimeter waves.
A cylinder based calibration method for integrating a line structured light sensor with a rotation-translation platform
Author(s):
Jingbo Zhou;
Yuehua Li;
Lijian Liu
Show Abstract
As a non-contact measuring apparatus, line structured light sensor (LSLS) can only get one profile of an object without the combination with other motional axes. To achieve the complete 3D measurement, a rotation-translation platform was integrated with the LSLS, and a cylinder based calibration method was also brought out. Firstly, the calibration model was proposed to determine the transformation matrix between the measuring coordinate frame (MCF) and the sensor coordinate frame (SCF). This model relies on the fact that the projection of an arbitrary intersection profile between the laser plane and the cylinder in its axis direction lies on a circle with a radius equal to the cylinder. Then, for a specified rotated angle and translated position of the object, the measured data from the SCF could all be transformed into the MCF, and the complete surface data could be obtained. Finally, a cylinder and a rectangular block were inspected by the proposed method. The surface data was successfully obtained and their intersection profiles indicate a high measuring accuracy of the proposed method. The method was further verified by the measured results of a screw surface.
Three-dimensional measurement of multilayer thin films based on scanning white light interferometer
Author(s):
Zhendong Shi;
Lin Zhang;
Huan Ren;
Quan Yuan;
Yi Yang;
Hua Ma
Show Abstract
For multilayer films system, in order to obtain the thickness and surface profile in each layer of thin film, a method to measure the 3D morphology of a multilayer films system based on scanning white light interferometer has been proposed in this article. At first, the mathematical relationship between reflection phase and thickness of each film layer has been obtained by using the electromagnetic field boundary conditions. Then, a nonlinear least square algorithm has been used to fit the reflection phase which had been found through a scanning white light interferometer, in this way the linear and nonlinear terms of the reflection phase have been separated, which made it possible to measure top-layer surface profile and thickness of each thin film layer respectively and avoided the interference with each other, because the linear term is related to the top layer’s surface profile but the nonlinear term is correlated to the thickness of each film layer in multilayer thin films system. Thus, the three-dimensional morphology of multilayer thin films system could be reconstructed. Experimental results showed this method was effective in the three-dimensional morphology measurement for multilayer thin films. And the measurement could be completed just using the existing commercial scanning white light interferometer, as a consequence the measurement cost is low, and the operation will be quite simple.
Analysis and modeling of atmospheric turbulence on the high-resolution space optical systems
Author(s):
Jiang Lili;
Xiaomei Chen;
Guoqiang Ni
Show Abstract
Modeling and simulation of optical remote sensing system plays an unslightable role in remote sensing mission
predictions, imaging system design, image quality assessment. It has already become a hot research topic at home and
abroad. Atmospheric turbulence influence on optical systems is attached more and more importance to as technologies of
remote sensing are developed. In order to study the influence of atmospheric turbulence on earth observation system, the
atmospheric structure parameter was calculated by using the weak atmospheric turbulence model; and the relationship of
the atmospheric coherence length and high resolution remote sensing optical system was established; then the influence
of atmospheric turbulence on the coefficient r0h of optical remote sensing system of ground resolution was derived;
finally different orbit height of high resolution optical system imaging quality affected by atmospheric turbulence was
analyzed. Results show that the influence of atmospheric turbulence on the high resolution remote sensing optical system,
the resolution of which has reached sub meter level meter or even the 0.5m, 0.35m and even 0.15m ultra in recent years,
image quality will be quite serious. In the above situation, the influence of the atmospheric turbulence must be corrected.
Simulation algorithms of PSF are presented based on the above results. Experiment and analytical results are posted.
Research on manufacturing method of CGH
Author(s):
Xueting Duan
Show Abstract
Computer Generated Holograms (CGH) has shown strong application potential and broad application prospect as the more and more extensive application of CGH. With respect to manufacture an available CGH, design the CGH will be easier. Therefore, this paper mainly summarizes some current feasible CGH manufacturing processes, and in this paper, the manufacturing processes of different types of CGH are presented and analyzed.
A new method of head attitude tracking based on CCD/MIMU
Author(s):
Kai Ma;
Quanxin Ding;
Qiuzhi Zhang;
Jianghua Wang;
Yongsheng Wang
Show Abstract
Head attitude tracking system based on MIMU can only maintain a short-term higher accuracy in the process of measurement. In order to overcome the defect, a new method by using CCD is proposed in this article. It introduces a CCD sensor to detect real-time head attitude, and then, delivers the posture to MIMU to accomplish the calibration process. For CCD could output a high precision data in a small field of view, the drift caused by gyroscopes and accelerometers in MIMU can be corrected effectively. Through the system authentication, we find that the method decreases the drift caused by MIMU obviously and keeps a high precision of measurement.
A testing method of optical axes parallelism of shipboard photoelectrical theodolite
Author(s):
Hui-hui Zou;
Hong-bing Wu;
Lu-jun Zhou
Show Abstract
A testing method of optical axes parallelism of shipboard photoelectrical theodolite (short for theodolite) was proposed which based on image processing by comparing disadvantages of the conventional method. Owing to the application of this method, the testing process of optical axes parallelism of theodolite was optimized as well as the adaptability of the testing method was enhanced. The trial result indicated that this method could improve the efficiency and accuracy, and it also could reduce the human vision which is the main factor affected the detection results and had some actual application values.
Detection for flatness of large surface based on structured light
Author(s):
Wenyan He;
Xuedong Cao;
Kuang Long;
Zhang Peng
Show Abstract
In order to get flatness of a large plane, this paper set up a measurement system, composed by Line Structured Light, imaging system, CCD, etc. Line Structured Light transmits parallel fringes at a proper angle onto the plane which is measured; the imaging system and CCD locate above the plane to catch the fringes. When the plane is perfect, CCD will catch straight fringes; however, the real plane is not perfect; according to the theory of projection, the fringes caught by CCD will be distorted by convex and concave. Extract the center of line fringes to obtain the distortion of the fringe, according to the functional relationship between the distortion of fringes and the height which is measured, then we will get flatness of the entire surface. Data from experiment approached the analysis of theory. In the simulation, the vertical resolution is 0.0075 mm per pixel when measuring a plane of 400mm×400mm, choosing the size of CCD 4096×4096, at the angle 85°. Helped by sub-pixel, the precision will get the level of submicron. There are two obvious advantages: method of surface sampling can increase the efficiency for auto-repairing of machines; considering the center of fringe is required mainly in this system, as a consequence, there is no serious demand for back light.
Study on paper's basis weight measurement method by double monochromatic light sources
Author(s):
Changtao Mo;
Guangming Wang;
Shuai Huan;
Jingji Wen;
Zhidan Xu;
Hailin Su;
Lili Zhang;
Jia Lv;
Ming Wang
Show Abstract
Given monochromatic infrared LED (light emitting diode) device best modulation current, frequency, distance to reach its maximum output power and improve the measuring accuracy of quantifier. Design a wavelength of 2.12 μm, 1.89 μm monochromatic infrared emissions and detection optical path, two monochromatic infrared lights which the photo source sends out after transmits the analyte across the same point to achieve the same point detection and improve the accuracy of the measurement. After the paper samples basis weight have carried out nondestructive testing, which was improved from the aspects of structure. By using the light source, halogen tungsten lamp, filter wheel, electrical equipment can be saved, and it can simplify the measuring system. The experimental results show that when measuring the thickness of the paper in the range, the relative error is within 1%.
Specular gloss scales comparison between the SIMT and the NIST
Author(s):
Dejin Yin;
Tiecheng Li;
Biyong Huang;
Weihai Cheng;
Fangsheng Lin
Show Abstract
Specular gloss is the fraction of light reflected in the specular direction for specified incident and receptor apertures, it is the perception by an observer of the mirror-like appearance of a surface. The measurement of specular gloss consists of comparing the luminous reflectance from a test sample to that from a calibrated gloss standard which generally is a polished piece of black glass, under the same experimental conditions. Gloss is a dimensionless quantity whose accurate determination requires standardized experimental conditions such as spectral distribution of the incident beam of light, incident and viewing angles, and a gloss standard. The Shanghai Institute of Measurement and Testing Technology (SIMT) provides test service to calibrate gloss reference standards. This facility is built around a reference goniophotometer, containing an instrument that measures flux as a function of angles of illumination or observation and a primary gloss standard, which is a piece of three wedges of highly polished, high-quality optical glass. The system has an overall (k=2) uncertainty of 0.5 Gloss Unit(GU). The service offers calibration measurements of working gloss standards at the geometries of 20°, 60°, and 85°, in compliance with the ISO 2813 and the ASTM D523 documentary standards. This article describes a bilateral comparison of specular gloss scales between SIMT and the National Institute of Standards and Technology (NIST) that has been performed. The results of this comparison show agreement within the combined uncertainties for the measurement of specular gloss of highly polished black glass.
Application of image stitching in rail abrasion 3D online detection
Author(s):
Jinlong Lee;
Xiaorong Gao;
Zeyong Wang;
Quanke Zhao;
Lin Luo
Show Abstract
PMP (Phase measuring Profilometry) is an excellent 3D online measurement method for its high precision. However, the
measuring range is limited. While the rail is so long that far exceeds the measuring limit, the image stitching should be
used to extent it. In this paper, based on the improved Stoilov algorithm, the rail shape is three-dimensionally
reconstructed and the abrasion is detected combines image stitching. Two types of schemes are researched: (1)image
stitching is firstly used on the deformed fringe patterns and then a larger range rail is constructed with Stoilov algorithm;
(2)the three-dimensional construction of two fringe pattern is firstly performed, and then the constructed images are
stitched into longer rail. In this paper, the improved Stoilov algorithm based on statistical approach and stitching
algorithm are analyzed. 3D Peaks function is simulated to verify the two methods, and then three-dimensional rail shape
is recovered based on these two methods and the rail abrasion is measured with the relative precision of higher than
0.1%, which is much higher than traditional methods, such as linear laser scanning.
Defect detection for end surface of ferrite magnetic tile
Author(s):
Jiayuan Tao;
Yuwei Wang;
Keyi Wang
Show Abstract
A visual automatic detection method is proposed for defect detection on end surface of ferrite magnetic tile to tackle the disadvantages generated by human work which has low efficiency and unstable accuracy. Because the defects on end surface of ferrite magnetic tile with dark colors and low contrasts are negative for defect detection, uniform illumination is provided by LED light source and a dedicated optical system is designed to extract defects conveniently. The approach uses comparison of the fitting and actual edge curves to detect defects mainly with most defects located on the edge. Firstly improved adaptive median filter is used as the image preprocessing. Subsequently the appropriate threshold is calculated by Otsu algorithm based on the extreme points in the gray-level histogram to segment the preprocessing image. Then the Sobel operator can be used to extract the edge of end surface precisely. Finally through comparing the ideal fitting and actual edge curves of end surface, to detect the defects with some relevant features. Experimental results show that the proposed scheme could detect defects on the end surface of ferrite magnetic tile efficiency and accurately with 93.33% accuracy rate, 2.30% false acceptance rate and 8.45% correct rejection rate.
The estimation method on diffusion spot energy concentration of the detection system
Author(s):
Wei Gao;
Zongxi Song;
Feng Liu;
Lijun Dan;
Zhonghan Sun;
Yunfei Du
Show Abstract
We propose a method to estimate the diffusion spot energy of the detection system. We do outdoor observation experiments in Xinglong Observatory, by using a detection system which diffusion spot energy concentration is estimated (the correlation coefficient is approximate 0.9926).The aperture of system is 300mm and limiting magnitude of system is 14.15Mv. Observation experiments show that the highest detecting magnitude of estimated system is 13.96Mv, and the average detecting magnitude of estimated system is about 13.5Mv. The results indicate that this method can be used to evaluate the energy diffusion spot concentration level of detection system efficiently.
Influencing factors and error analysis for specular gloss measurement
Author(s):
Tiecheng Li;
Leibing Shi;
Lei Lai;
Fangsheng Lin;
Dejin Yin;
Ming Xia;
Limin Wu
Show Abstract
Specular gloss has been widely used to characterize the ability of a surface to reflect light specularly. Specular gloss is theoretically related to the physical properties of a surface, such as roughness, directionality and uniformity. Specular gloss, mainly determined by incident angle and refractive index of a surface, is a relative measurement quantity. Specular gloss is usually measured by a glossmeter. The topographical and optical properties of a surface have been analyzed on how to affect the measurements. The experiment results indicate that a less rough/flatter, more isotropic and more uniform surface will result in a more accurate measurement value. Therefore, physical properties of a surface must be carefully inspected before the specular gloss measurement in order to acquire a satisfied result.
Evaluating system for SRAM-based FPGA single event upset rate
Author(s):
Yunlong Wang;
Bin Bao
Show Abstract
This paper takes static random-access-memory (SRAM)-based field-programmable-gate-array (FPGA) as the research object. Attention is focused on the configuration memory of this kind of FPGA, and the research has been devoted to the contents of the configuration memory and the configuration circuit to manage its contents. The single event upset (SEU) happening in the configuration memory doesn’t lead to a functional failure necessarily. The dynamic SEU is SEU which happens in the configuration memory and causes necessarily function failure. This paper introduces a test method of dynamic SUE rate for the SRAM-based FPGA by designing a FPGA with self-test function.
The method to reduce the spinal error in the aspheric mirror testing with the CGH
Author(s):
Fengtao Yan;
Bin Fan;
Xi Hou;
Fan Wu;
Baiping Lei;
Haitao Liu;
Hongshen Zhao
Show Abstract
Interferometric optical testing using computer-generated holograms(CGHs) has proven to supply a very good and
accurate measurements method of the aspheric surfaces. However, the CGHs are diffractive optical elements which use
diffraction to create wavefronts of light with desired amplitudes and phases. The different diffraction order of the light
would be make some ghost image to the fringe pattern. It would introduce some spinal error to the measurement results.
This error would not be avoided after the CGH designed and manufactured. In this work, we take two measurement steps
to reduce the spinal error. The first step, the apheric mirror was tested with the CGHs. The second step, the aspheric
mirror was tested with transmission sphere directly. Then the subaperture theory was used to obtain the final
measurement results of the aspheric mirror surface. The experimental demonstrations were provided by testing an
aspheric mirror. The results are shown that this method could reduce the spinal error.
Research on measurement of total luminous flux of single LED in direct comparison method
Author(s):
Biyong Huang;
Lei Lai;
Dejin Yin;
Weihai Cheng;
Fangsheng Lin
Show Abstract
This paper focuses on traceability work on total luminous flux of single LED based on the direct camparison method applied for quantity transfer of incandescent lamps. During the test different color groups of LEDs have been chosen as standard to measure total luminous flux of sample LEDs. The test is accomplished in the current integrating sphere measurement system under specific conditions according to LED characteristics. As results obtained from the experiment, the uncertainties are also evaluated.
A novel long-wave infrared high resolution continuous zoom lens with uncooled thermal detector
Author(s):
Jiaqi Bao;
Kan Yu;
Zijuan Ji
Show Abstract
Infrared imaging lens is one of the key components of a video security camera. A novel long-wave infrared continuous zoom lens is developed based on the 640×512 high resolution uncooled infrared thermal detector which can substitute the high cost cooled infrared detector. The zoom lens contains five germanium lens and one chalcogenide glass lens, which working in the wavelength range of 8~12 μm. Its F number range is in 1~ 1.1 while the focus length is changing from 20 to 120 mm. Based on the zoom lens design theory, the positive lens mechanical compensation structure is used to calculate the optical parameters and optimize the cam zoom curve, which can have a smooth continuous zoom in the range of all focus lengths. The image analysis show that the system has achieved the modulation transfer function (MTF) value above 0.45 which spatial frequency is 30 lp/mm. The spot diagrams RMS radius is less than 6.3μm which is near the diffraction limit. The real test photos indicate that the lens has the advantages of high resolution, large aperture, smooth zoom and stable image plane. Due to the high image quality and low cost, the continuous zoom lens is easily to be fabricated.
A fast algorithm for image defogging
Author(s):
Xingyu Wang;
Shuai Guo;
Hui Wang;
Haibing Su
Show Abstract
For the low visibility and contrast of the foggy image, I propose a single image defogging algorithm. Firstly, change the foggy image from the space of RGB to HSI and divide it into a plurality of blocks. Secondly, elect the maximum point of S component of each block and correct it, keeping H component constant and adjusting I component, so we can estimate fog component through bilinear interpolation. Most importantly, the algorithm deals with the sky region individually. Finally, let the RGB values of all pixels in the blocks minus the fog component and adjust the brightness, so we can obtain the defogging image. Compared with the other algorithms, its efficiency is improved greatly and the image clarity is enhanced. At the same time, the scene is not limited and the scope of application is wide.
Measurement of deformation and frequency response characteristic of PZT tube in tunable fiber laser with short period based on coherent laser beam
Author(s):
Zhi Lai;
Xiaodong Zeng;
Zhaojin Fan;
Zhichen Xu
Show Abstract
The parameters of light source in synthetic aperture ladar (SAL) is very important to both the design of system and the signal processing algorithm. As the light source in the SAL, the fiber laser use PZT (piezoelectric ceramics) tube stretching the fiber Bragg grating in order to tune the laser frequency. So it is necessary to obtain the deformation and frequency response of PZT tube driven by saw-tooth voltage of different periods. Accordingly, the homodyne detection is used to measure the girth variation of PZT tube. Meanwhile, the frequency response of PZT tube can be viewed with the homodyne signal. The results from measuring a PZT tube show that the method can work well.
Consistency check method for sighting axis and laser detection axis based on field testing
Author(s):
Hao Guo;
Linfeng Zhao;
Yanfang Liu;
Ruiguang Yin
Show Abstract
Optical axis consistency is an important index of multi-axes equipment. Most test methods of optical axis consistency are aimed at the consistency of multi sighting axes, or consistency between sighting axis and laser emission axis. It is difficult for consistency test between sighting axis and laser detection axis. A new method based on field testing was put forward to solve the difficulty of consistency check between sighting axis and laser detection axis. At first, sighting axis was set down as base, and high precision numerical turntable was used to adjust laser detection heading, and then the total field of view of laser detection channel was measured. The laser detection axis was gotten subsequently. Finally, the consistency error of sighting axis and laser detection axis was worked out, by comparing sighting axis’s angular position with the angular position of laser detection axis. There are many merits of the method, such as high precision, wide applicability, and easy to operate, etc. Meanwhile, the field of view of laser detection channel was checked out. This paper showed that the method we put forward can meet the demand of consistency check between sighting axis and laser detection axis well.
Color hologram reconstruction based on single DMD
Author(s):
Jiang Xing;
Hao Zhou;
Dan Wu;
Jun-jian Hou;
Ji-hua Gu
Show Abstract
Because of the magnification chromatic aberration and the transverse chromatic aberration caused from different wavelengths of color lasers in the process of color holographic optoelectronic reconstruction based on DMD, the reconstructed holograms of three color components can not coincide. Firstly, on the reference of blue color component, the magnification chromatic aberration of the original image is eliminated. Secondly, according to the analysis of the incident angles of three lasers, the transverse chromatic aberration is eliminated by adjusting the incident angles. At last, the synthesized color hologram is obtained by means of the experiments based on DMD. The method proposed in this paper does not use any lens, so there is no axial chromatic aberration.
General model for the pointing error analysis of Risley-prism system based on ray direction deviation in light refraction
Author(s):
Hao Zhang;
Yan Yuan;
Lijuan Su;
Fengzhen Huang;
Qing Bai
Show Abstract
The Risley-prism-based light beam steering apparatus delivers superior pointing accuracy and it is used in imaging LIDAR and imaging microscopes. A general model for pointing error analysis of the Risley prisms is proposed in this paper, based on ray direction deviation in light refraction. This model captures incident beam deviation, assembly deflections, and prism rotational error. We derive the transmission matrixes of the model firstly. Then, the independent and cumulative effects of different errors are analyzed through this model. Accuracy study of the model shows that the prediction deviation of pointing error for different error is less than 4.1×10-5° when the error amplitude is 0.1°. Detailed analyses of errors indicate that different error sources affect the pointing accuracy to varying degree, and the major error source is the incident beam deviation. The prism tilting has a relative big effect on the pointing accuracy when prism tilts in the principal section. The cumulative effect analyses of multiple errors represent that the pointing error can be reduced by tuning the bearing tilting in the same direction. The cumulative effect of rotational error is relative big when the difference of these two prism rotational angles equals 0 or π, while it is relative small when the difference equals π/2. The novelty of these results suggests that our analysis can help to uncover the error distribution and aid in measurement calibration of Risley-prism systems.
Computer-generated holograms for precision optical testing
Author(s):
Xiaohong Wei;
Yuhang He;
Kaiyuan Xu;
Bo Gao;
Qiang Li;
Liqun Chai
Show Abstract
Computer generated holograms (CGHs) are state-of-the-art components in optical systems, and are widely used in combination with standard Fizeau interferometers. The primary role of the CGHs is to generate reference wavefront with any desired shape. A method of interferometrically measuring large convex lens with CGHs is adopted, and the results from a set of experiments that demonstrate the accuracy and simplicity of performing the holographic test are presented. A direct comparison of the CGH measurement with results from a compensation method shows excellent agreement. Finally, measurement uncertainty due to substrate error and hologram fabrication processes is analyzed.
Adaboost multi-view face detection based on YCgCr skin color model
Author(s):
Qi Lan;
Zhiyong Xu
Show Abstract
Traditional Adaboost face detection algorithm uses Haar-like features training face classifiers, whose detection error rate is low in the face region. While under the complex background, the classifiers will make wrong detection easily to the background regions with the similar faces gray level distribution, which leads to the error detection rate of traditional Adaboost algorithm is high. As one of the most important features of a face, skin in YCgCr color space has good clustering. We can fast exclude the non-face areas through the skin color model. Therefore, combining with the advantages of the Adaboost algorithm and skin color detection algorithm, this paper proposes Adaboost face detection algorithm method that bases on YCgCr skin color model. Experiments show that, compared with traditional algorithm, the method we proposed has improved significantly in the detection accuracy and errors.
Application research of the balance detector on coherent detection techniques
Author(s):
Gaixia Wang;
Yongmei Huang
Show Abstract
The principles of coherent detection and balanced detectors are analyzed respectively in this article. It mainly talked about the balance detector applications in coherent detection. Obtained by the theoretical analysis that we can not only make full use of the local oscillator optical power but also eliminate the noise of the LO light more effectively by using the balanced detector. The most important is that it can improve the SNR of the system. This paper also makes a research on the factors that affect the performance of the balanced detector. The simulation results show that the response of the photo-diode consistency should be gain at least 90% in order to improve the SNR effectively. It further validates that the laser intensity noise indeed declined by using the balanced detector.
A standard test method based on point spread function for three-dimensional imaging system
Author(s):
Tao Wen;
Jinxin Dong;
Zhixiong Hu;
Zhenggang Cao;
Wenli Liu;
Jianlin Wang
Show Abstract
Point spread function (PSF) theory has been demonstrated as proof of concept in evaluation of spatial resolution of three dimensional imaging technology like optical coherence tomography (OCT) and confocal microscopy. A robust test target and associated evaluation algorithm are in demand for keeping regular quality assurance and inter-comparison of such 3D imaging system performance. To achieve this goal, standard-size micro spheres were utilized to develop PSF phantoms. The OCT system was investigated with the microsphere PSF phantom. Differing from previous study, a statistical model comprising data from hundreds of scatterers was established to acquire the PSF distribution and variation. The research provided an effective method and a set of practical standard phantoms for evaluating resolution of three dimensional imaging modalities.
Development of glucose measurement system based on pulsed laser-induced ultrasonic method
Author(s):
Zhong Ren;
Bin Wan;
Guodong Liu;
Zhihua Xiong
Show Abstract
In this study, a kind of glucose measurement system based on pulsed-induced ultrasonic technique was established. In this system, the lateral detection mode was used, the Nd: YAG pumped optical parametric oscillator (OPO) pulsed laser was used as the excitation source, the high sensitivity ultrasonic transducer was used as the signal detector to capture the photoacoustic signals of the glucose. In the experiments, the real-time photoacoustic signals of glucose aqueous solutions with different concentrations were captured by ultrasonic transducer and digital oscilloscope. Moreover, the photoacoustic peak-to-peak values were gotten in the wavelength range from 1300nm to 2300nm. The characteristic absorption wavelengths of glucose were determined via the difference spectral method and second derivative method. In addition, the prediction models of predicting glucose concentrations were established via the multivariable linear regression algorithm and the optimal prediction model of corresponding optimal wavelengths. Results showed that the performance of the glucose system based on the pulsed-induced ultrasonic detection method was feasible. Therefore, the measurement scheme and prediction model have some potential value in the fields of non-invasive monitoring the concentration of the glucose gradient, especially in the food safety and biomedical fields.
Performance evaluation and verification of infrared imaging system based on TTP metric
Author(s):
Na Ma;
Qiong Gao;
Zhendong Ding;
Yanxiu Zhang
Show Abstract
With the development of infrared focal plane array (IRFPA) technology, the high performance staring infrared imaging system has fully substituted the scanning type, and become the third generation thermal imaging system. Meanwhile the performance evaluation model associated with the device level also should be updated accordingly. This paper compares the traditional distance evaluation model with the latest model that is based on Target Task Performance (TTP) metric, and analyzes the problems and deficiencies when we evaluate a staring imaging system using the traditional model. Taking a certain type of infrared imaging equipment for example, we simulate its performances by using the two models respectively, and analyze the simulation results. Finally we verified the simulation results through field experiments, the results show that the value predicted by the model basing on the rule of TTP is closer to the measured value. This paper suggests that the TTP model is more accurate than traditional model in the design, optimization and evaluation of the high performance staring infrared imaging system.
Research on testing method for combined aspheric surface with non-rotational symmetric
Author(s):
Wencai Zhou;
Feng Xu;
Xiaoxiao Wei
Show Abstract
Non-rotational symmetric aspheric surface has many significant advantages, but it still can not be widely used because the limiting that there is no method can tests it precisely. At present, the coordinate contour measuring machine is the main testing method for the aspheric surface with non-rotational symmetric, but the measurement accuracy of this method is not high. In this paper, the method of diffraction compensator (computed graphic holograph) has been adopted to test the combined aspheric surface, which can compensate the phase caused by tested lens. The sample surface is the combined aspheric surface with diameter of 33.84mm, and the process from optical software simulation design, the fabrication of the computed graphic holograph (CGH) to experimental platform built is given in detail after testing via the CGH technology. The simulation results show that the root mean square (RMS) of remnant wave-front error is 0.004 λ, and the peak to valley (PV) is 0.0245 λ. The free-from surface has been tested by Zygo interferometer, and the experimental results show that the RMS is 0.49 λ, the PV is 4.69 λ. The accuracy of the result is higher than that of coordinate contour measuring machine. The system error caused by optical elements analysed is 0.1149λ. The accurate result means that the CGH technology for testing the combined aspheric surface is realized.
Design and fabrication of CGH for 600mm diameter SiC primary mirror surface figure testing
Author(s):
Zhihai Pang;
Zhen Ma;
Xuewu Fan;
Gangyi Zou
Show Abstract
Computer-generated hologram (CGH) is an effective way to compensate wavefront aberration in null test of aspheric
surfaces and freeform surfaces. Our strategies of CGH design for 600mm diameter SiC primary mirror surface figure
testing are presented, and an experiment demonstrating the compensation test results of CGH is reported. We design a
CGH including two sections on the same substrate in order to align the CGH to the incident wavefront: main section for
compensating wavefront in null test, alignment section for adjusting the relative position between CGH and
interferometer. In order to isolate different orders of diffraction, we used power carrier to make different orders of
diffraction come to focus at different position along the axis to avoid ghost reflections. We measured the 600mm
diameter SiC primary mirror using this CGH, and the surface test result is 0.033λ rms.
A new method for COD analysis with full-spectrum based on Artificial Neural Network
Author(s):
Wei-wei Feng;
Dan Li;
Zong-qi Cai;
Fu-guo Hao
Show Abstract
A new on-line monitoring system was developed for the determination of chemical oxygen demand (COD) in water based on full-spectrum analysis. In this system, Artificial Neural Net (ANN) work was used to obtain the transmission equation between absorbance and COD value by measuring absorption spectra of water with known COD value, and then the established equation could inverse the COD values of the unknown water samples. For the COD determination of simulated complicated water samples, the instrumental reliability was well validated by a comparison made between the ANN method and the PLS method. The monitoring system of the ANN method provided advantages of simplicity, rapidity, high precision, no consumption of reagent. And it was demonstrated an ideal alternative to real-time and on-line monitoring of COD in water.
Generation of parallel transmission sub-pulses of spatial distribution based on polarizing splitting prism
Author(s):
Haifeng Yang;
Xiaoping Yang;
Xuna Sun;
Jun Liu;
Yong Yang
Show Abstract
Parallel processing is the forefront of femtosecond laser micro-nano processing. The key to parallel processing is obtaining multichannel parallel femtosecond laser beams. A method of spatial parallel pulse splitting based on birefringence properties of polarizing splitting prism is proposed for obtaining multichannel parallel ultra-short pulse trains. The generated sub-pulses have the characteristics of equal energy and high similarity. More than that, the compact structure of the polarizing splitting prism makes it easier to be implemented. The accurate relationship between the space interval of pulse sequences and the structural angle, dimension and the distance between the two prisms is mathematically derived. The realizable array form of sub-pulse sequences is theoretically analyzed. The feasibility of the proposed method of femtosecond laser parallel processing is analyzed by software simulation and numerical calculation. The results will provide a new research direction for application of ultrashort pulse in parallel processing.
Evaluating surface repeatability for interferometric measurement: a comparative study
Author(s):
Haiyang Quan;
Hou Xi;
Fan Wu
Show Abstract
The result of an interferometric surface figure measurement is a height map, from which single parametric descriptors (for example the RMS) or residual maps are the most commonly used methods for determining the measurement repeatability. An alternate technique based on a standard deviation matrix is used to better describe the variation among successive measurements. A standard deviation matrix is acquired by computing standard deviation of the height map pixel by pixel. Only one standard deviation matrix can provide a spatial description of the repeatability as well as parametric descriptors (for example the mean) of the standard deviation matrix. Comparative study on the evaluation of measurement repeatability among different methods is shown by both simulation and experiment. It seems that the standard deviation matrix method is more valid to detect the variation than other techniques in the measurement of surface figure.
New reconstruction algorithm for absolute shape calibration in two-flat test
Author(s):
Yuhang He;
Qiang Li;
Daoming Wan;
Liqun Chai
Show Abstract
A new reconstruction algorithm for absolute shape calibration in two-flat test is proposed. The shift-rotation method is applied to absolute shape calibration in two-flat test. Relying on the decomposition of the reconstructed shapes into rotationally asymmetric and symmetric components, an iteration algorithm is presented to reconstruct the rotationally asymmetric components, and Zernike polynomial fitting algorithm is used to calculate rotationally symmetric components. Compared to the traditional algorithms, the proposed algorithm has the characteristics of considerable accuracy and less computational effort. A simulation experiment proves the validity of the presented algorithm.
Object tracking algorithm based on contextual visual saliency
Author(s):
Bao Fu;
XianRong Peng
Show Abstract
As to object tracking, the local context surrounding of the target could provide much effective information for getting a robust tracker. The spatial-temporal context (STC) learning algorithm proposed recently considers the information of the dense context around the target and has achieved a better performance. However STC only used image intensity as the object appearance model. But this appearance model not enough to deal with complicated tracking scenarios. In this paper, we propose a novel object appearance model learning algorithm. Our approach formulates the spatial-temporal relationships between the object of interest and its local context based on a Bayesian framework, which models the statistical correlation between high-level features (Circular-Multi-Block Local Binary Pattern) from the target and its surrounding regions. The tracking problem is posed by computing a visual saliency map, and obtaining the best target location by maximizing an object location likelihood function. Extensive experimental results on public benchmark databases show that our algorithm outperforms the original STC algorithm and other state-of-the-art tracking algorithms.
Object detection based on deformable part model
Author(s):
Lei Wei;
Zhiyong Xu
Show Abstract
In complex scene, considering traditional object detection methods based on feature points have exposed many problems, such as undetected points, low detected ratio and cannot well process object occlusion and scaling situation, this paper proposes a detection method which based on a deformable part model. The method uses histogram of oriented gradient (HOG) feature as the object description, and the deformable part model includes a global template and several high-resolution templates. And the method uses the support vector machine (SVM) training the object model. In the learning process, after the HOG feature extracted, the method modifies the HOG feature, and then uses the principal component analysis (PCA) method reducing feature dimensions to avoid over-learning, and improve the detection rate in the detection process. The experiment results shows that the method proposed can better process object occlusion or scaled situation, and there’s also an improvement in detection ratio.
Studies on spectral scene reproduction systems based on multispectral LED fitting
Author(s):
Xinzhuo Lei;
Wang Zhou;
Lei Wang
Show Abstract
Utilization of the spectrum simulation in many important fields widely, it has made the target spectral simulation technique to be an important development trends. With the rapid development of the application of the LED technology, the LED have the merits of long serving life, high lighting efficiency, rapid responding time, and high wide selection of light band. Consequently, taking the demands of designing for the target spectral scene reproduction systems into consideration, LED with variable light bands as the light source, and performs Gauss Curve calculation to fit spectra in scene via Matlab software, and therefore serving as the criteria to selection of LED. Meanwhile, the system of driving a light source applies high performance embedded MCU as the main data processor. The chip for LED is a specific driver chip which was made in TI Corporation. Through analyzing the data collected from the target spectra in scene, then the processor transfers the calculated results to the driver IC (integrated circuit) of LED. The spectrum in scene is reproduced basing on the results. Moreover, this design method can also combine with spectrometer directly to realize the real-time capability of reproduction of the spectra in scene. It has a great potential application in the future.
Method used to test the imaging consistency of binocular camera's left-right optical system
Author(s):
Meiying Liu;
Hu Wang;
Jie Liu;
Yaoke Xue;
Shaodong Yang;
Hui Zhao
Show Abstract
To binocular camera, the consistency of optical parameters of the left and the right optical system is an important factor that will influence the overall imaging consistency. In conventional testing procedure of optical system, there lacks specifications suitable for evaluating imaging consistency. In this paper, considering the special requirements of binocular optical imaging system, a method used to measure the imaging consistency of binocular camera is presented. Based on this method, a measurement system which is composed of an integrating sphere, a rotary table and a CMOS camera has been established. First, let the left and the right optical system capture images in normal exposure time under the same condition. Second, a contour image is obtained based on the multiple threshold segmentation result and the boundary is determined using the slope of contour lines near the pseudo-contour line. Third, the constraint of gray level based on the corresponding coordinates of left-right images is established and the imaging consistency could be evaluated through standard deviation σ of the imaging grayscale difference D (x, y) between the left and right optical system. The experiments demonstrate that the method is suitable for carrying out the imaging consistency testing for binocular camera. When the standard deviation 3σ distribution of imaging gray difference D (x, y) between the left and right optical system of the binocular camera does not exceed 5%, it is believed that the design requirements have been achieved. This method could be used effectively and paves the way for the imaging consistency testing of the binocular camera.
Development of high power UV irradiance meter calibration device
Author(s):
Ming Xia;
Jianqiang Gao;
Dejin Yin;
Tiecheng Li
Show Abstract
With the rapid development of China's economy, many industries have more requirements for UV light applications, such as machinery manufacturing, aircraft manufacturing using high power UV light for detection, IT industry using high power UV light for curing component assembly, building materials, ink, paint and other industries using high power UV light for material aging test etc. In these industries, there are many measuring instruments for high power UV irradiance which are need to traceability. But these instruments are mostly imported instruments, these imported UV radiation meter are large range, wide wavelength range and high accuracy. They have exceeded our existing calibration capability. Expand the measuring range and improve the measurement accuracy of UV irradiance calibration device is a pressing matter of the moment. The newly developed high power UV irradiance calibration device is mainly composed of high power UV light, UV filter, condenser, UV light guide, optical alignment system, standard cavity absolute radiometer. The calibration device is using optical alignment system to form uniform light radiation field. The standard is standard cavity absolute radiometer, which can through the electrical substitution method, by means of adjusting and measuring the applied DC electric power at the receiver on a heating wire, which is equivalent to the thermo-electromotive force generated by the light radiation power, to achieve absolute optical radiation measurement. This method is the commonly used effective method for accurate measurement of light irradiation. The measuring range of calibration device is (0.2~200) mW/cm2, and the uncertainty of measurement results can reached 2.5% (k=2).
Design of measuring system for wire diameter based on sub-pixel edge detection algorithm
Author(s):
Yudong Chen;
Wang Zhou
Show Abstract
Light projection method is often used in measuring system for wire diameter, which is relatively simpler structure and lower cost, and the measuring accuracy is limited by the pixel size of CCD. Using a CCD with small pixel size can improve the measuring accuracy, but will increase the cost and difficulty of making. In this paper, through the comparative analysis of a variety of sub-pixel edge detection algorithms, polynomial fitting method is applied for data processing in measuring system for wire diameter, to improve the measuring accuracy and enhance the ability of anti-noise. In the design of system structure, light projection method with orthogonal structure is used for the detection optical part, which can effectively reduce the error caused by line jitter in the measuring process. For the electrical part, ARM Cortex-M4 microprocessor is used as the core of the circuit module, which can not only drive double channel linear CCD but also complete the sampling, processing and storage of the CCD video signal. In addition, ARM microprocessor can complete the high speed operation of the whole measuring system for wire diameter in the case of no additional chip. The experimental results show that sub-pixel edge detection algorithm based on polynomial fitting can make up for the lack of single pixel size and improve the precision of measuring system for wire diameter significantly, without increasing hardware complexity of the entire system.
Measurement of z-axis deviation angle of electro-optic crystal by conoscopic interference
Author(s):
Dong Li;
Yong Liu;
Xu Liu;
Hongzhen Jiang;
Fanglan Zheng
Show Abstract
Properties of plasma electrode pockels cell is directly affected by the Z-axis deviation angle of the electro-optic crystal. Therefore, high precision measurement of the Z-axis deviation angle is indispensable. By using conoscopic interference technique, a measurement system for Z-axis deviation angle of electro-optic crystal is introduced. The principle of conoscopic interference method is described in detail, and a series of techniques are implied in this measurement system to improve the accuracy. High-precision positioning method of the crystal based on Michelson interference is proposed to determine the normal consistency of crystal, which can ensure the high positioning repeatability of crystal in the measurement process. The positioning comparison experiment of the crystal shows that the standard deviation of our method is less than 1pixel, which is much better than the traditional method (nearly 4pixels). Moreover, melatope extraction algorithm of optical axis based on image matching technique is proposed to ensure the melatope can be extracted in high precision. Calibration method of the normal of transmission surface of crystal is also proposed. The experiment results show that the PV and rms of Z-axis deviation angle is less than 0.05mrad and 0.02mrad, respectively. The repeatability accuracy is less than 0.01mrad.
Stray light measurement for point source transmittance of space optical systems
Author(s):
Qinfang Chen;
Zhen Ma;
Xinyao Li;
Zhihai Pang;
Liang Xu;
Zhaohui Li
Show Abstract
The increased sensitivity of space-based sensors has imposed greater stray light performance goals on telescope design. To meet the demand, a stray light test station for measuring point source transmission (PST) has been built with a lower threshold and higher accuracy. The station is nearly all black with dimensions of 28m long by 8m wide by 9m high. it is coupled with a double cylindrical chamber that reflects the specular light away from the instrument under test. The chamber is a Class 6 cleanroom. The station will allow measuring the instruments with up to a 1 meters diameter, and to perform these measurements at visible and infrared wavelengths. The instrument under test will allow to scan at azimuth angles ±110°, and at elevation ±15°. The tests were performed to estimate stray light characteristics of two optical instruments. Test results demonstrated PST performance below 1×10-7 at visible wavelengths, and 1×10-6 at infrared wavelengths.
Simulation study on simultaneous phase-shifting lateral-shearing interferometer
Author(s):
XuHua Wu
Show Abstract
Phase-shifting interferometry (PSI) is widely used in optical testing because of its advantages of high accuracy, high sensitivity and untouched test characteristics. However, the environment vibration introduces a random error in the temporal phase shift, which should be presise enough to ensure the test accuracy. In this paper, an novel simultaneous phase-shifting interferometry (SPSI) device is presented. In this device, using two identical transmission gratings and double shear-plates as the beam splitter and double shear-plates as the phase shifter, the optical path difference between the original wavefront and the sheared wavefront can be achieved by adjusting the spacing and wedge angle between the double shear-plates. Then three interferograms with 90° phase shift interval are captured simultaneously and instantaneously by the same CCD. The processing of the interferograms is performed using conventional methods of phase extraction with the algorithm of three phase shifts. Overcoming the disadvantages of traditional mechanical phaseshifting mode, therefore, influence caused by the environment vibration is eliminated. The arithmetic model of this SPSI system is deduced, sheared interferograms of optical system with different wavefront heights can be obtained, which can be used to test the high precision optical surface on-line. Compared with the conventional temporal PSI, this SPSI device is easy to be realized, but some phase shift errors appears such as the spatial mismatch between phase shifted interferograms and the inaccurate light split ratio generated by the difference diffraction efficiency between the ±1th order and the 0th order transmittance lights of the gratings. Better precision can be achieved by error correction techniques such as phase shifting calibration or multiplying the right correction factor in the interferograms processing algorithm.
Axis consistency testing method based on image processing technology for non-cooperative target
Author(s):
Xin Li;
Yong Zhang;
Dongxi Ma
Show Abstract
The multi-axis consistency among optical sensors is the basic guarantee to ensure the normal operation of the entire optical equipment. In the paper the new method which is image processing technology for non-cooperative target is provided to solve the axis consistency testing question. In detail, firstly an observing object is chosen as non-cooperative target in scene in front of inspected equipment. Secondly the target is observed by the optical sensor and the central location of crosshair in image is recorded. Thirdly the same target is observed again using another optical sensor and the central location of crosshair in image is record. At last, the testing result of two optical sensors can be obtained by the position deviation of crosshair central comparing two images. The axis consistency of mechanical axis and the optical axis is detected by the CCD imaging systems, which held on the mechanical axis of the measured object. Not only the proposed method is suitable to different working band, but also it is very small, not limited by field condition and convenient for carry. Furthermore experimental results show the proposed method has high inspecting accuracy, which explain the feasibility and potential applications.
Study and analysis of catadioptric null compensating test
Author(s):
Long Zhang;
Wenqi Hu;
Liehua Zheng;
Peiming Hao
Show Abstract
Aiming at the concave aspheric mirror with large aperture or large relative aperture, catadioptric null compensating test is proposed. To carry out the null compensation test of concave aspheric surface, double lens and single mirror are used. The catadioptric compensator is set in front of curvature center of tested mirror. Based on third-order aberration theory, making spherical aberration coefficient S1=0, the calculating formulas of initial configuration structure parameters are derivated. This novel testing method is studied by design of catadioptirc compensators for the following three situations, the design results and drawings are given: 1) mirrors(F/2, e2=1.05) with different apertures; 2) mirrors(Φ0=2000mm, e2=1.05) with different relative apertures; 3) to design catadioptric compensators for mirror (Φ0=2000mm, e2=1.05, r0=8000mm) with different inner obscuration ratio. The analysis shows that this new method is available to test concave aspheric mirror with large aperture or large relative aperture.
Development and experiments of lateral shearing interferometer for parabolic surface measurement
Author(s):
Bingcai Liu;
Hongjun Wang;
Ailing Tian
Show Abstract
Large aperture parabolic mirrors are widely used in high technology areas, such as astronomical optics, space optics et.al. In order to obtain better optical performance, the lateral shearing interferometer was developed for characterizing the surface figure of parabolic mirror. Firstly, based on penta-prism and shearing optical flat, lateral shearing interferometry device was installed; secondly, the shearing phase was calculated by four-step phase shifting algorithm, the transform from shearing phase to primary phase was reconstructed through the selection of discrete sampling points and wave-front fitting, and the shearing interferometry software was programed. Lastly, through a concave parabolic mirror inspection, the precision of the shearing interferometer and the anti-vibration characteristic were verified.
Research of maneuvering target prediction and tracking technology based on IMM algorithm
Author(s):
Zheng Cao;
Yao Mao;
Chao Deng;
Qiong Liu;
Jing Chen
Show Abstract
Maneuvering target prediction and tracking technology is widely used in both military and civilian applications, the study of those technologies is all along the hotspot and difficulty. In the Electro-Optical acquisition-tracking-pointing system (ATP), the primary traditional maneuvering targets are ballistic target, large aircraft and other big targets. Those targets have the features of fast velocity and a strong regular trajectory and Kalman Filtering and polynomial fitting have good effects when they are used to track those targets. In recent years, the small unmanned aerial vehicles developed rapidly for they are small, nimble and simple operation. The small unmanned aerial vehicles have strong maneuverability in the observation system of ATP although they are close-in, slow and small targets. Moreover, those vehicles are under the manual operation, therefore, the acceleration of them changes greatly and they move erratically. So the prediction and tracking precision is low when traditional algorithms are used to track the maneuvering fly of those targets, such as speeding up, turning, climbing and so on. The interacting multiple model algorithm (IMM) use multiple models to match target real movement trajectory, there are interactions between each model. The IMM algorithm can switch model based on a Markov chain to adapt to the change of target movement trajectory, so it is suitable to solve the prediction and tracking problems of the small unmanned aerial vehicles because of the better adaptability of irregular movement. This paper has set up model set of constant velocity model (CV), constant acceleration model (CA), constant turning model (CT) and current statistical model. And the results of simulating and analyzing the real movement trajectory data of the small unmanned aerial vehicles show that the prediction and tracking technology based on the interacting multiple model algorithm can get relatively lower tracking error and improve tracking precision comparing with traditional algorithms.
A surface irregularity compensation alignment method for all-reflective optical system
Author(s):
Lian Li;
Ming Zhang;
TianMeng Ma
Show Abstract
Surface irregularity of optical elements is one of the errors caused in manufacturing process, which has a bad influence on optical system image quality. This image quality deterioration can’t be neglected especially in some all-reflective optical systems. A method by rotating the mirrors for compensating the surface irregularity is put forward in the paper. Firstly, the surface irregularity of all the mirrors is analyzed and the most closely matched mirrors are chosen for one set of system alignment. Then, the wavefront characteristic of optical system and the surface irregularity of each mirror represented by Zernike polynomial are studied, and the relationship between them is analyzed. The calculation of the rotate angle is described in detail. A numerical simulation of the method has been performed for two sets of three-mirror optical system to verify the ability and accuracy of the method. The results show that the astigmatism of the optical system caused by the surface irregularity can be decreased and the image quality of both the two systems can be improved effectively. The method is especially suitable for multiple sets of optical systems alignment.
Online damage inspection of optics for ATP system
Author(s):
Jing Chen;
Yu Jiang;
Yao Mao;
Xun Gan;
Qiong Liu
Show Abstract
In the Electro-Optical acquisition-tracking-pointing system (ATP), the optical components will be damaged with the several influencing factors. In this situation, the rate will increase sharply when the arrival of damage to some extent. As the complex processing techniques and long processing cycle of optical components, the damage will cause the great increase of the system development cost and cycle. Therefore, it is significant to detect the laser-induced damage in the ATP system. At present, the major research on the on-line damage detection technology of optical components is for the large optical system in the international. The relevant detection systems have complicated structures and many of components, and require enough installation space reserved, which do not apply for ATP system. To solve the problem mentioned before, This paper use a method based on machine vision to detect the damage on-line for the present ATP system. To start with, CCD and PC are used for image acquisition. Secondly, smoothing filters are used to restrain false damage points produced by noise. Then, with the shape feature included in the damage image, the OTSU Method which can define the best segmentation threshold automatically is used to achieve the goal to locate the damage regions. At last, we can supply some opinions for the lifetime of the optical components by analyzing the damage data, such as damage area, damage position. The method has the characteristics of few-detectors and simple-structures which can be installed without any changes of the original light path. With the method, experimental results show that it is stable and effective to achieve the goal of detecting the damage of optical components on-line in the ATP system.
A visual tracking method based on improved online multiple instance learning
Author(s):
Xianhui He;
Yuxing Wei
Show Abstract
Visual tracking is an active research topic in the field of computer vision and has been well studied in the last decades. The method based on multiple instance learning (MIL) was recently introduced into the tracking task, which can solve the problem that template drift well. However, MIL method has relatively poor performance in running efficiency and accuracy, due to its strong classifiers updating strategy is complicated, and the speed of the classifiers update is not always same with the change of the targets’ appearance. In this paper, we present a novel online effective MIL (EMIL) tracker. A new update strategy for strong classifier was proposed to improve the running efficiency of MIL method. In addition, to improve the t racking accuracy and stability of the MIL method, a new dynamic mechanism for learning rate renewal of the classifier and variable search window were proposed. Experimental results show that our method performs good performance under the complex scenes, with strong stability and high efficiency.
Defects detection for rough magnetic tiles surface based on light sectioning
Author(s):
Yuwei Wang;
Jiayuan Tao;
Xiangcheng Chen;
Keyi Wang
Show Abstract
Magnetic tile as a kind of product of mass production and wide application in electronic motors, and defects detection is a major issue in its production line. In this paper, a machine vision method based on black-stripe projection is presented to deal with this issue. Because of magnetic tile surface with black colors, rough structure and complex grinding textures, we abandon intensity imaging and resort to light sectioning methods which provides more reliable and abundant surface information. In order to suppress the speckle diffraction effect caused by laser light source, we used the light-emitting diode (LED) with incoherent characteristics. The black-stripe images were captured by a high-speed camera. A fast algorithm was developed to extract and compare both edges of the black-stripe, which could detect defects and eliminate the effects of vibrations. The experimental results show that the simple and fast processing method proposed in this paper can detect the structural defects such as micro pits and micro cracks.
A new measurement method for color discrimination thresholds of human eyes based on PWM light-mixing technology
Author(s):
Jiyan Zhang;
Jinxin Dong
Show Abstract
The color discrimination is a powerful tool for detection of eye diseases, and it is is necessary to produce different kinds of color rapidly and precisely for testing color discrimination thresholds of human eyes. Three channels’ pulse-width modulation (PWM) and light-mixing technology is a new way to mixing color, and a new measurement method for color discrimination thresholds of human eyes based on PWM light-mix technology can generate kinds of color stimuli. In this study, 5 youth volunteers were measured via this equipment after the test for the stability of the device’s illumination and chrominance. Though the theory of Macadam ellipses and the interleaved staircase method, a psychophysical experiment was made to study the color discrimination threshold of the human eyes around a basic color center. By analyzing the data of the chromatic ellipse and the color discrimination threshold, the result shows that each color is not uniform in a single color region and the color difference threshold of normal human is around the third Macadam ellipses. The experimental results show that the repeatability and accuracy of the observer can meet the accuracy requirements of the relevant experiments, and the data is reliable and effective, which means the measurement method is an effective way to measure the color discrimination thresholds of human visual system.
Compact optical system for cesium atomic fountain clock
Author(s):
Jiang Chen;
Jun Ruan;
Junru Shi;
Fengxiang Yu;
Hui Zhang;
Xinliang Wang;
Shougang Zhang
Show Abstract
The optical system plays a significant role to cesium atomic fountain clocks, which manipulates and detects population of cesium atoms. This paper presents a compact optical system for cesium atomic fountain clocks. The optical system provides two beams with 32mW separately for cooling atoms and six beams of 12mW respectively for trapping atoms with the frequency tuning from 80MHz to 220MHz. The relative intensity noise of the detect laser beam reduces from 1.33×10-6 Hz to 1.52×10-10 Hz at 1Hz by the laser power stabilization system. The optical system operates continuously for 30 days with the fluctuation of optical power less than 3% approximately. And the frequency stability is 3×10-15 at 1000s. The results show the optical system satisfies with the needs of our cesium atomic fountain clock developed and establishes the foundation for cesium atomic fountain continuous operation.
Fizeau simultaneous phase-shifting interferometry based on extended source
Author(s):
Shanshan Wang;
Qiudong Zhu;
Yinlong Hou;
Zheng Cao
Show Abstract
Coaxial Fizeau simultaneous phase-shifting interferometer plays an important role in many fields for its characteristics of long optical path, miniaturization, and elimination of reference surface high-frequency error. Based on the matching of coherence between extended source and interferometer, orthogonal polarization reference wave and measurement wave can be obtained by Fizeau interferometry with Michelson interferometer preposed. Through matching spatial coherence length between preposed interferometer and primary interferometer, high contrast interference fringes can be obtained and additional interference fringes can be eliminated. Thus, the problem of separation of measurement and reference surface in the common optical path Fizeau interferometer is solved. Numerical simulation and principle experiment is conducted to verify the feasibility of extended source interferometer. Simulation platform is established by using the communication technique of DDE (dynamic data exchange) to connect Zemax and Matlab. The modeling of the extended source interferometer is realized by using Zemax. Matlab codes are programmed to automatically rectify the field parameters of the optical system and conveniently calculate the visibility of interference fringes. Combined with the simulation, the experimental platform of the extended source interferometer is established. After experimental research on the influence law of scattering screen granularity to interference fringes, the granularity of scattering screen is determined. Based on the simulation platform and experimental platform, the impacts on phase measurement accuracy of the imaging system aberration and collimation system aberration of the interferometer are analyzed. Compared the visibility relation curves between experimental measurement and simulation result, the experimental result is in line with the theoretical result.
Analysis of absolute flatness testing in sub-stitching interferometer
Author(s):
Xin Jia;
Fuchao Xu;
Weimin Xie;
Tingwen Xing
Show Abstract
Sub-aperture stitching is an effective way to extend the lateral and vertical dynamic range of a conventional interferometer. The test accuracy can be achieved by removing the error of reference surface by the absolute testing method. When the testing accuracy (repeatability and reproducibility) is close to 1nm, in addition to the reference surface, other factors will also affect the measuring accuracy such as environment, zoom magnification, stitching precision, tooling and fixture, the characteristics of optical materials and so on. In the thousand level cleanroom, we establish a good environment system. Long time stability, temperature controlled at 22°±0.02°.The humidity and noise are controlled in a certain range. We establish a stitching system in the clean room. The vibration testing system is used to test the vibration. The air pressure testing system is also used. In the motion system, we control the tilt error no more than 4 second to reduce the error. The angle error can be tested by the autocollimator and double grating reading head.
A review of RGB-LED based mixed-color illumination system for machine vision and microscopy
Author(s):
Lexin Hou;
Hexin Wang;
Min Xu
Show Abstract
The theory and application of RGB-LED based mixed-color illumination system for use in machine vision and optical microscopy systems are presented. For machine vision system, relationship of various color sources and output image sharpness is discussed. From the viewpoint of gray scale images, evaluation and optimization methods of optimal illumination for machine vision are concluded. The image quality under monochromatic and mixed color illumination is compared. For optical microscopy system, demand of light source is introduced and design thoughts of RGB-LED based mixed-color illumination system are concluded. The problems need to be solved in this field are pointed out.
Surface roughness measurement with laser triangulation
Author(s):
Fuzhong Bai;
Xiaoyan Zhang;
Chaoping Tian
Show Abstract
A surface roughness measurement method is introduced in the paper, which is based on laser triangulation and digital image processing technique. In the measuring system, we use the line-structured light as light source, microscope lens and high-accuracy CCD sensor as displacement sensor as well. In addition, the working angle corresponding to the optimal sensitivity is considered in the optical structure design to improve the measuring accuracy. Through necessary image processing operation for the light strip image, such as center-line extraction with the barycenter algorithm, Gaussian filtering, the value of roughness is calculated. A standard planing surface is measured experimentally with the proposed method and the stylus method (Mitutoyo SJ-410) respectively. The profilograms of surface appearance are greatly similar in the shape and the amplitude to two methods. Also, the roughness statistics values are close. The results indicate that the laser triangulation with the line-structured light can be applied to measure the surface roughness with the advantages of rapid measurement and visualized display of surface roughness profile.
Experimental study of resonance fiber optic gyroscope employing a dual-ring resonator
Author(s):
Yue Fan;
Wei Wang
Show Abstract
A dual-ring resonator which is available to alter the full width at half maximum (FWHM) without altering the free spectrum range (FSR) for practice applications is analyzed theoretically and set up in practice. The parameters of the dual-ring resonator have been optimized in simulation, the resonance depth and the dynamic range are enhanced. The prototype is set up with single mode fiber of 8 meter and two 95 : 5 couplers for open loop experiment. The FWHM of the dual-ring resonator is demonstrated less than 1.5MHz and the fineness is calculated to be 37 during the frequency sweeping experiment. The frequency locking experiment with demodulation curve method has been accomplished, and the locking time achieves less than 40ms. All these provide a basic reference for optimizing the resonance fiber optic gyro based on dual-ring resonator.
The effect analysis of conic coefficient error based on data measured from Talysurf and simulation of Zernike coefficients
Author(s):
Jiang Kai;
Kai Liu;
Chong Song;
Qiu Peng;
Wang Peng;
Gang Li
Show Abstract
Derivation of the conic coefficient error of practical aspheric optic surface is quite significant to aspheric machining accuracy, optical system imaging quality analysis and decomposition analysis of optical lenses. The primary mirror of R-c telescope system was tested by Taylor Hobson Talysurf. The practical surface was fitted using Zernike polynomials based on the date measured from Talysurf. Though taking the Zernike coefficients into the optical system, the effect of the aberration which was brought by optical machining to the optical system imaging quality was obtained. The analysis shows that the spherical aberration was brought into the optical system because of the figure error of the primary mirror. And the value of the spherical aberration was same to the practical alignment result. Then the conicoid aspherical degree of the primary mirror was tested by the Talysurf. The machining deviation of the conic coefficient was gotten though comparing the conicoid aspherical degree of the practical primary mirror with that of the perfect primary mirror. The practical conic coefficient was calculated by the deviation. Taking the practical conic coefficient into the R-c telescope system, the degradation of the optical system imaging quality was known. Also the spherical aberration was brought into the optical system. Experimental results show that the value of the spherical aberration analyzed by the two methods is same and consist with the practical alignment result. That is to say that the conic coefficient changed due to machining error of the conicoid aspherical degree. Because of the change the spherical aberration was attached to primary mirror. And which caused the optical system imaging quality declined. Finally, corrector was designed to balance the spherical aberration of the primary mirror. Ensure that the optical system imaging quality meet the requirement.
Research of mine water source identification based on LIF technology
Author(s):
Mengran Zhou;
Pengcheng Yan
Show Abstract
According to the problem that traditional chemical methods to the mine water source identification takes a long time, put forward a method for rapid source identification system of mine water inrush based on the technology of laser induced fluorescence (LIF). Emphatically analyzes the basic principle of LIF technology. The hardware composition of LIF system are analyzed and the related modules were selected. Through the fluorescence experiment with the water samples of coal mine in the LIF system, fluorescence spectra of water samples are got. Traditional water source identification mainly according to the ion concentration representative of the water, but it is hard to analysis the ion concentration of the water from the fluorescence spectra. This paper proposes a simple and practical method of rapid identification of water by fluorescence spectrum, which measure the space distance between unknown water samples and standard samples, and then based on the clustering analysis, the category of the unknown water sample can be get. Water source identification for unknown samples verified the reliability of the LIF system, and solve the problem that the current coal mine can't have a better real-time and online monitoring on water inrush, which is of great significance for coal mine safety in production.
The application of tapered multi-mode fiber in laser signal simulation
Author(s):
Ruiguang Yin;
Hao Guo;
Weiwei Liang;
Wenpan Zhang;
Hui Li
Show Abstract
According to laser signal simulation, the advantage of application of tapered multi-mode fiber on laser pulse signal transmission was analyzed. By optical system simulation, the effect on the coupling efficiency of 1.06μm laser pulse signal of different angle was analyzed. By optical experiment, the coupling efficiency and transmission mode of different incident angle and force condition were confirmed. Combining the application of simulation system, with convex lens, frosted glass and optical integrator on the outlet of fiber, the far-field energy distribution was measured. According the receiving optical system entrance pupil, the effect on the beam quality to the simulation result was analyzed. The results showed that the application of tapered multi-mode fiber on laser pulse signal simulation is feasible, and the equipment has been used in the engineering projects.
Design of short-range terahertz wave passive detecting system
Author(s):
Chao Zhang;
Guowei Lou;
Li Zhu;
Songsong Qian;
Ting Li
Show Abstract
Based on the study of radiation and transmission characteristics on THz waveband, a short-range passive detecting system
is designed. The scheme originated from microwave passive detecting system. A prototype was developed following the
design of key components including antennas and a harmonic mixer. The system operated at 0.36 THz. A dual-beam
Cassegrain antenna was adopted for receiving signals which radiated by object and background. Local oscillator signal was
generated by frequency multiplication. Harmonic mixing is adopted for reducing local oscillator signal frequency required
by half. Superheterodyne technology is employed for signal acquisition. The system implemented easily. Tests and
measurements were taken, which showed that the scheme was feasible and the performance of the prototype system met
the design requirements.
Non-null compensator design method in digital Moiré interferometry for freeform surface measurement
Author(s):
Qun Hao;
Shaopu Wang;
Yao Hu
Show Abstract
High accuracy interferometric testing for freeform optics surface has always been a great challenge because of its arbitrary form. Our group proposed a Digital Moiré Interferometric Technique (DMIT) based on partial compensator (PC) for aspheric surface testing since the year 2003. But the PC design method for non-rotational symmetric freeform surface is still a challenge. In this paper, we propose a PC design method for non-null freeform surface measurement. The PC generates non-rotational symmetry aberration by off axis and rotation round axis. Later the design criterion of PC is also analyzed. Finally an off-axis aspheric surface was measured in the simulation experiment, and the error of PV and RMS is 0.0053λ and 0.0498λ theoretically. Experimental results indicate that the designed PC is able to be utilized in freeform surface measurement.
The aberration characteristics in a misaligned three-mirror anastigmatic (TMA) system
Author(s):
Bin Wang;
Fan Wu;
Yutang Ye
Show Abstract
To realize the efficient alignment of the TMA system, the aberrations in a misaligned TMA system had been analyzed
theoretically in this paper. Firstly, based on the nodal aberration theory (NAT), the aberration types and characteristics in
the misaligned TMA system had been concluded; Secondly, a simulation validation had been carried out to testify the
analysis results, the simulation results validates the aberration characteristics; Finally, the alignment procedures were
determined according to the aberration characteristics: adjust the axial spacing of the mirrors in terms of Z9 in the center
field of TMA system first; and then, adjust the decenters and tilts of the mirrors in terms of Z5 - Z8 in the edge field of
TMA system. This method is helpful for the alignment of the TMA telescope.
An adaptive block-based fusion method with LUE-SSIM for multi-focus images
Author(s):
Jianing Zheng;
Yongcai Guo;
Yukun Huang
Show Abstract
Because of the lenses’ limited depth of field, digital cameras are incapable of acquiring an all-in-focus image of objects at varying distances in a scene. Multi-focus image fusion technique can effectively solve this problem. Aiming at the block-based multi-focus image fusion methods, the problem that blocking-artifacts often occurs. An Adaptive block-based fusion method based on lifting undistorted-edge structural similarity (LUE-SSIM) is put forward. In this method, image quality metrics LUE-SSIM is firstly proposed, which utilizes the characteristics of human visual system (HVS) and structural similarity (SSIM) to make the metrics consistent with the human visual perception. Particle swarm optimization(PSO) algorithm which selects LUE-SSIM as the object function is used for optimizing the block size to construct the fused image. Experimental results on LIVE image database shows that LUE-SSIM outperform SSIM on Gaussian defocus blur images quality assessment. Besides, multi-focus image fusion experiment is carried out to verify our proposed image fusion method in terms of visual and quantitative evaluation. The results show that the proposed method performs better than some other block-based methods, especially in reducing the blocking-artifact of the fused image. And our method can effectively preserve the undistorted-edge details in focus region of the source images.
Interferometry measurement of parallel optical plate wavefront
Author(s):
Yi Yang;
Huan Ren;
Zhendong Shi;
Yong Liu;
Xu Liu;
Quan Yuan;
Xiaoyu Yang;
Lin Zhang
Show Abstract
In this paper, a method is introduced to test wavefront aberration of parallel optical plate wavefront, which based on
Fourier transform. When testing the wavefront aberration of parallel optical plate, there is multiple-surface interference
which phase-shifting interferometry cannot handle with. With the help of wavelength-modulation phase-shifting
interferometry and Fourier transform, this method can isolate the multiple-surface interference fringes in frequency
domain. This paper expound the principle of the method, and analyze the key parameter of the testing method: the
suitable cavity/thickness ratio and sampling frame number. A simulation experiment is set up to verify the accuracy of
this method, then the comparison test with traditional method shows that the relative deviation between the two methods
is ≤5%.
Performance evaluation of laser line scanner for in-process inspection of 3D geometries
Author(s):
Sen Zhou;
Jian Xu;
Lei Tao;
Yu Yan
Show Abstract
Non-contact measurement techniques using laser scanning have the power to deliver tremendous benefits to most notably manufacturing, and have the advantage of high speed and high detail output. However, a major obstacle to their widespread adoption in more complex on-line producing environments is their geometric constraints and low accuracy compared to the contact-based counterparts. The work presented in this paper introduces a performance evaluation test of laser line scanning for in-process inspection of 3D geometries. Some straightforward test methods that use a designed artifact are proposed. First, one work aims to experimentally investigate the location accuracy of knee point or corner point of edge features using a commercial laser stripe scanner, which is common in mechanical parts. Another work experimentally investigates the formation of outliers that may be usually promoted by reflective surfaces around surrounding area of corner point, and these outliers are characterized with large measurement errors, which significantly deteriorate the quality of the scanned point cloud data. Scanning path planning and outlier filter design are respectively discussed.
Large-scale absolute surface reconstruction
Author(s):
Gao-feng Wu;
Hai-yang Quan;
Wei-hong Song;
Yong-qian Wu;
Fan Wu
Show Abstract
In order to realize large-scale absolute surface reconstruction, a generalized iterative optimization method for solving the three-flat problem is studied. First, the idea of model-based absolute surface reconstruction is proposed, which considers the problems of absolute surface reconstruction as inverse problems. Then we take the three-flat problems as an example, we introduced two generalized iterative optimization methods for three-flat model. Finally, by both simulation and experiment, it is concluded that the block SOR method with an optimal relaxation factor converges much faster and saves more computational costs and memory space without reducing accuracy. Both simulation and experimental results indicate that the proposed iterative optimization methods are effective for solving the three-flat problem with pixel-level spatial resolution and the measuring precision of two separate measurements is 0.6 nm rms, and the cross-check test result is 0.8 nm rms. It is concluded that the proposed method can correctly reconstruct absolute figures with high efficiency and pixel-level spatial resolution.
TRIZ theory in NEA photocathode preparation system
Author(s):
Jianliang Qiao;
Dayong Huang;
Xiangjiang Li;
Youtang Gao
Show Abstract
The solutions to the engineering problems were provided according to the innovation principle based on the theory of TRIZ. The ultra high vacuum test and evaluation system for the preparation of negative electron affinity (NEA) photocathode has the characteristics of complex structure and powerful functions. Segmentation principle, advance function principle, curved surface principle, dynamic characteristics principle and nested principle adopted by the design of ultra high vacuum test and evaluation system for cathode preparation were analyzed. The applications of the physical contradiction and the substance-field analysis method of the theory of TRIZ in the cathode preparation ultra high vacuum test and evaluation system were discussed.
New design of electronic display system for spectrometer
Author(s):
Ji-peng Huang;
Jin-huan Li;
Cheng-chang Tang;
Zhao-wei Huang;
Rui Han;
Er-ting Pan;
Wei-kun Dai
Show Abstract
There are several disadvantages in existing electronic display systems for spectrometer, such as the images with noise and fuzziness, the cross hair with low sharpness and so on. In order to solve these problems, a new type of electronic display system for spectrometer is designed in this paper, connecting the spectrometer eyepiece to a CCD Camera with a Camera Link interface, and setting up a video processing system platform with a high performance FPGA. The Camera Link signals collected by the front-end system are sent into two pieces of SDRAM. The controller of SDRAM generated on the FPGA realizes data with caching and processing high speed data streams by ping-pong operation. Then the data signals are filtered by filter module generated on the FPGA and the color space of treated signals are converted. In the back-end system, signals encoded by two coder chip are separately outputted through the CVBS and the VGA interfaces. This design solves above problems of the original system.
The effects of Ga incorporation on the crystalline quality of AlInAs metamorphic buffer using x-ray characterization
Author(s):
Y. He;
Y. Song;
Y. R. Sun;
S. Z. Yu;
Y. M. Zhao;
J. R. Dong
Show Abstract
The Al(Ga)InAs metamorphic buffers grown by metal organic chemical vapor deposition (MOCVD) on GaAs substrates with miscut angles toward (111)A exhibit anisotropic properties in the two <110> directions. The dislocation distributions of samples were examined using X-ray rocking curve along two orthogonal <110> directions and the measurement results suggested that Ga incorporation can reduce the density of α dislocation. There is an inflection point of substrate miscut above which the type of higher dislocation density switched from α to β types, while Ga incorporation can change the location of the inflection point.
The design and implementation of the full-Stokes imaging spectropolarimeter
Author(s):
Jiankang Zhou;
Yiqun Ji;
Xinhua Chen;
Yuheng Chen;
Suodong Ma;
Weimin Shen
Show Abstract
The imaging spectro-polarimetry combines the spectral imaging technology and the imaging polarization technology. It assembles the functions of camera, spectrometer and polarimeter. So the optical information quantity is increased and the detection efficiency is improved. But the acquirement of the multi-dimensional information results in the detector complex construction and large volume. The moving part is used in the current method to realize the different polarization states or spectral filtering. The images are difficult for registration and the current method can’t be used to get the motion scene. This paper presents innovative imaging spectro-polarimetry method with no moving parts. The hyper-spectral information, full-Stokes polarization information and one-dimensional spatial information are obtained by the polarization modulating and spectrum dispersing. The designed imaging spectro-polarimeter is composed of two parts, a polarization module and the spectral dispersive module. They are all employed stationary configuration. The polarization module includes two birefringent crystal wave plates and a polarizer. The thickness of the birefringent wave-plates and the polarization axes of each component are optimized and the full-Stokes polarization information is loaded on the spectrum. The polarization information can be restored by the Fourier transform. The concentric Offner configuration is adopted for spectral dispersive module. It is composed of two concave spherical mirrors and a holographic aberration-corrected convex grating. The designed dispersive configuration is compact and aligned simply. And high quality linear dispersion, low distortion spectral image are implemented. The Full-stokes imaging spectro-polarimeter our designed is validated by the model simulation and the laboratory experiment. The mixed hyper-spectral information and accuracy polarization information can be obtained.
A novel method using simplified PCNN for near infrared eye detection
Author(s):
Xiaoyan Wu;
Yongcai Guo
Show Abstract
In the near infrared image containing complex background, eye detection is a great challenge for a low signal to noise ratio and lacking of shape and texture information. Aiming at the problem of accurate eye localization and segmentation, simplified pulse coupled neural networks (SPCNN) combined with morphology method is put forward. The contributions of this work can be divided into two parts. The first contribution is that the local region of the eyes is extracted efficiently via morphology opening top-hat operator, as the region of interest for ensuring the follow-up processing without interference of the background. The second contribution is that a SPCNN model is proposed to carefully partition pixels into a corresponding cluster in iterative manner for ensuring high segmentation performance. Experiments are carried out on the near infrared images obtained by the designed acquisition system using the proposed method as well as Otsu and k-means for comparison. Experimental results show that our method achieves desired segmentation performance and has a lower misclassification error.
A simple method for focal length measurement
Author(s):
Hua Ma;
Huan Ren;
Lin Zhang;
Zhengdong Shi;
Quan Yuan;
Yi Yang
Show Abstract
A simple method for focal length measurement based on image processing is demonstrated and discussed. The collimated beam, detector, motorized translation stage and computer make up of this test system. The two spots pass through the tested lens is accepted by detector, which is transferred twice by motorized translation stage. By acquired the difference of two spots by image processing, the focal length of the tested lens can be gained. The error sources in the measurement are analyzed. Then the results of experiment show that the relative error was 0.1%. This method can be used in workshop and labs for its convenience and low cost.
Laser range profile of spheres
Author(s):
Yanjun Gong;
Mingjun Wang;
Lei Gong
Show Abstract
Profile information about a three-dimensional target can be obtained by laser range profile (LRP). A mathematical LRP model from rough sphere is presented. LRP includes laser one-dimensional range profile and laser two-dimensional range profile. A target coordinate system and an imaging coordinate system are established, the mathematical model of the range profile is derived in the imaging coordinate system. The mathematical model obtained has nothing to do with the incidence direction of laser. It is shown that the laser range profile of the sphere is independent of the incidence direction of laser. This is determined by the symmetry of the sphere. The laser range profile can reflect the shape and material properties of the target. Simulations results of LRP about some spheres are given. Laser range profile of sphere, whose surface material with diffuse lambertian reflectance, is given in this paper. Laser one-dimensional range profile of sphere, whose surface mater with diffuse materials whose retro-reflectance can be modeled closely with an exponential term that decays with increasing incidence angles, is given in this paper. Laser range profiles of different pulse width of sphere are given in this paper. The influences of geometric parameters, pulse width on the range profiles are analyzed.
Modeling and simulation of atmosphere interference signal based on FTIR spectroscopy technique
Author(s):
Yugui Zhang;
Qiang Li;
Zhengyang Yu;
Zhengmin Liu
Show Abstract
Fourier Transform Infrared spectroscopy technique, featured with large frequency range and high spectral resolution, is becoming the research focus in spectrum analysis area, and is spreading in atmosphere detection applications in the aerospace field. In this paper, based on FTIR spectroscopy technique, the principle of atmosphere interference signal generation is deduced in theory, and also its mathematical model and simulation are carried out. Finally, the intrinsic characteristics of the interference signal in time domain and frequency domain, which give a theoretical foundation to the performance parameter design of electrical signal processing, are analyzed.
Analysis of spectral mismatch error influences on short-circuit current measurement of reference solar cell
Author(s):
Chuan Cai;
Yingwei He;
Junchao Zhang;
Limin Xiong;
Taogeng Zhou;
Haifeng Meng;
Kejia Zhang;
Bifeng Zhang
Show Abstract
Spectral mismatch error should be carefully considered during the calibration of solar cells by means of solar simulator
and calibrated reference cell. Even test and reference cells with the same type should be also considered spectral mismatch
error to achieve good measurement results. Spectral mismatch error can be calculated with the relative spectral response
of the test and reference cells, and the relative spectral irradiance of the simulator and reference solar. The reference solar
spectral irradiance distribution was given according to IEC60904-3:2008. Experimental results, two cells, one test and
one ref, with two different spectra solar simulators, were presented. The calculation method and experimental data
presented could be positive reference to photovoltaic labs to obtain good calibration and test results of solar cells.
Solving surface parameters of conic asphere mirror based on computer simulation
Author(s):
Chuan-ke Huang;
Yong-qian Wu;
Bin Fan;
Bai-ping Lei
Show Abstract
Radius of curvature R and conic constant k are important parameters of aspheres.Null testing or CGH are usually used to evaluate the processing quality of aspheric mirrors in fabricating process . When the null compensator emerges a problem, additional method to ensure the accuracy of paraxial radius of curvature and conic constant is required. Based on the equation of conic aspheric, the computing model from which the paraxial radius of curvature R and conic constant k can be obtained was established, and a set of solving algorithm using singular value decomposition (SVD) method was derived. The simulating result of a 1800mm aspheric mirror is presented and the solving precision reaches R=6120±0.026mm, k=-1.0194±0.0008, thus the supplement to null testing of aspheric mirror is achieved effectively .
Analysis and design of energy monitoring platform for smart city
Author(s):
Hong-xia Wang
Show Abstract
The development and utilization of energy has greatly promoted the development and progress of human society. It is the basic material foundation for human survival. City running is bound to consume energy inevitably, but it also brings a lot of waste discharge. In order to speed up the process of smart city, improve the efficiency of energy saving and emission reduction work, maintain the green and livable environment, a comprehensive management platform of energy monitoring for government departments is constructed based on cloud computing technology and 3-tier architecture in this paper. It is assumed that the system will provide scientific guidance for the environment management and decision making in smart city.
Iterative surface construction for blind deflectometry
Author(s):
Wenchuan Zhao;
Logan R. Graves;
Run Huang;
Weihong Song;
DaeWook Kim
Show Abstract
Freeform optics provide excellent performance for a wide variety of applications. However, obtaining an accurate freeform surface measurement is highly challenging due to its large aspheric/freeform departure. It has been proven that SCOTS (Software Configurable Optical Test System), an advanced deflectometry system developed at the University of Arizona, can measure the departure of a freeform surface from the desired shape with nanometer accuracy. Here, a new data processing technique was used to measure a freeform surface without any prior knowledge of the shape of the surface. Knowing only the geometry of one point on the test surface, this method can take a blind measurement of a freeform surface and arrive at the true surface through iterative construction.
Automatic estimation of the focusing reconstruction distance of recorded object in digital holography
Author(s):
Hongzhen Jiang;
Xu Liu;
Yong Liu;
Dong Li;
Zhu Chen;
Fanglan Zheng;
Xiaoyu Yang;
Bo Chen
Show Abstract
In this paper, a method which can effectively achieve the accurate estimation of the focusing reconstruction distance of recorded object in digital holography (DH) is proposed. By analyzing the variance variety of the reconstructed intensity images corresponding to different reconstruction distances, the accurate focusing reconstruction distance of the recorded object is obtained and thus the legible reconstructed image in-focus is acquired. The effectiveness of the proposed method is successfully validated with both pure phase objects and pure amplitude objects in experiment. This method will have great potential application foreword in digital holographic measurement field.
Experimental investigation of laser transmission at 1.06um in horizontal atmosphere under fine and haze-fog conditions of summer
Author(s):
Kaixin Yin;
Chunhong Qiao;
Xiaoxing Feng;
Pengfei Zhang;
Chengyu Fan
Show Abstract
With two sets of experimental instruments, laser transmission was investigated through horizontal atmosphere at 1.06 m under fine and haze-fog events. One set of the instruments is an indirect transmission meter used to measure visibility and the other one is a direct transmission meter used to measure the attenuation of laser power. Results show that the variation of transmittance got from laser power (Tp) and that obtained by visibility (Tvis) are highly correlated. For relative humidity (RH) below 85%, the curve of Tvis fits that of Tp very well. While the RH is above 85%, the Tvis is more likely smaller than Tp under fine meteorological condition, but under haze-fog condition Tvis is larger than Tp on the contrary. For different weather condition, the relation efficient between extinction coefficient and visibility is different. Even for similar visibility, the extinction coefficient of haze-fog event is larger than that of fine event.
Computer-aided alignment method of optical lens with high accuracy
Author(s):
Song Xing;
Xiao-hua Hou;
Xue-min Zhang;
Bin-dong Ji
Show Abstract
With the development of space and aviation industry, the optical systems with high resolution and better imaging quality are required. According to the alignment technical process, the factors of every step which have big influence to the imaging quality are analyzed. It is detected that the micro-stress assembly of the optical unit and the high co-axial precision of the entire optical system are the two important factors which are supposed to determine how well the imaging quality of the optical system is; also the technical methods are discussed to ensure these two factors from the engineering view. The reflective interference testing method to measure the surface figure and the transitive interference testing method to measure the wave aberration of the optical unit are combined to ensure the micro-stress assembly of the optical unit, so it will not bring astigmatism to the whole system imaging quality. Optical alignment machining and precision alignment are combined to ensure the high co-axial precision of the optical system. An optical lens of high accuracy is assembled by using these methods; the final wave aberration of optical lens is 0.022λ.
Rigid geometric-optics autocollimation model and its theoretical analysis based on ray-tracing method
Author(s):
Fan Zhu;
Xinran Tan;
Jiubin Tan;
Zhigang Fan
Show Abstract
A rigid geometric-optics autocollimation model is established using ray-tracing method to overcome the limitations of conventional autocollimation model due to its lack of necessary parameters. The established model describes the transmission process of the light rays that are emitted from the illuminated target plane and transmit through the autocollimation system and return back to the receiving plane. Simulation results of the model indicate that the cross-talk of 2D micro-angle measurement in autocollimation can be 0.035 arcsec in a measurement range of ±1000 arcsec. The coordinate deviation of ±3 mm from the optical axis of the points on the target plane could result to a variation of -0.045 to 0.246 arcsec in autocollimation. The defocus of ±50 μm of the target plane and the receiving plane could result to an error of 0.278 arcsec. The variation of measurement distance from 200 to 2000 mm could result to a maximum error of 0.500 arcsec in autocollimation while the defocus of receiving plane is 50 μm. The established model can be used for further analysis and improvement of autocollimation.
Dual-wavelength method for measuring the thickness of HSQ photoresist
Author(s):
Shun Yao;
Bo Yu;
Jingcheng Jin;
Chun Li
Show Abstract
The reflectivity of thin film changes periodically with the increase of its thickness. According to this effect, we present a
dual-wavelength method for measuring the thickness of HSQ film. At first, the refractive index of HSQ was measured by
a spectroscopic ellipsometer. Then the relationship between the thickness of HSQ and the reflectivity was deduced. At
last, the thickness of HSQ was calculated using the reflectivity measured by a spectrograph. The method was proved to
be simple and effective.
Noise suppression performance of typical phase shifting algorithms
Author(s):
Xiaoqiang Zhu;
Yong-qian Wu;
Fengwei Liu
Show Abstract
Comparative simulations are designed to evaluate the noise suppression performance of three typical phase shifting algorithms under different testing environments. The results show that random phase shifting algorithm is robust under different level of noise and has higher testing accuracy than conventional normal steps phase shitting algorithm while it’s computationally low. Guidelines are given to choose a proper PSI algorithm under a certain testing environment with noises.
Analysis of adjustment error in aspheric null testing with CGH
Author(s):
Yiwei He;
Hou Xi;
Qiang Chen;
Fan Wu;
Chaoqiang Li;
Xiaoqiang Zhu;
Weihong Song
Show Abstract
Generally, in order to gain high accuracy in aspheric testing, a piece of high-quality CGH (computer generated hologram) is inserted behind transmission sphere to generate specified wave-front to match aspheric part. According to the difference in function, the CGH is divided into 2 parts: the center region, called as testing hologram, is used to generate specified aspheric wave-front; the outer ring, called as alignment hologram, is used to align the location of CGH behind transmission sphere. Although alignment hologram is used, there is still some adjustment error from both CGH and aspheric part, such as tilt, eccentricity and defocus. Here we will stimulate the effect of these error sources on the accuracy that is rms after the piston, tilt and power are removed, when testing a specified aspheric part. It is easy to conclude that the total measurement error is about 2 nm and the defocus of CGH contributes most.