Proceedings Volume 9618

2015 International Conference on Optical Instruments and Technology: Optical Systems and Modern Optoelectronic Instruments

Yongtian Wang, Xiaodi Tan, Kimio Tatsuno
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Proceedings Volume 9618

2015 International Conference on Optical Instruments and Technology: Optical Systems and Modern Optoelectronic Instruments

Yongtian Wang, Xiaodi Tan, Kimio Tatsuno
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Volume Details

Date Published: 12 August 2015
Contents: 7 Sessions, 46 Papers, 0 Presentations
Conference: International Conference on Optical Instruments and Technology 2015 2015
Volume Number: 9618

Table of Contents

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Table of Contents

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  • Front Matter: Volume 9618
  • Optical Systems for Biomedical Applications
  • Optical Measurement and Testing
  • Digital Holography and 3D Imaging
  • Infrared Optics
  • Novel Optical System Design
  • Poster Session
Front Matter: Volume 9618
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Front Matter: Volume 9618
This PDF file contains the front matter associated with SPIE Proceedings Volume 9618 including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.
Optical Systems for Biomedical Applications
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Inertial and optical sensor fusion to compensate for partial occlusions in surgical tracking systems
To solve the occlusion problem in optical tracking system (OTS) for surgical navigation, this paper proposes a sensor fusion approach and an adaptive display method to handle cases where partial or total occlusion occurs. In the sensor fusion approach, the full 6D pose information provided by the optical tracker is used to estimate the bias of the inertial sensors when all of the markers are visible. When partial occlusion occurs, the optical system can track the position of at least one marker which can be combined with the orientation estimated from the inertial measurements to recover the full 6D pose information. When all the markers are invisible, the position tracking will be realized based on outputs of the Inertial Measurement Unit (IMU) which may generate increasing drifting error. To alert the user when the drifting error is great enough to influence the navigation, the images adaptive to the drifting error are displayed in the field of the user’s view. The experiments are performed with an augmented reality HMD which displays the AR images and the hybrid tracking system (HTS) which consists of an OTS and an IMU. Experimental result shows that with proposed sensor fusion approach the 6D pose of the head with respect to the reference frame can be estimated even under partial occlusion conditions. With the help of the proposed adaptive display method, the users can recover the scene of markers when the error is considered to be relatively high.
The research and development of the adaptive optics in ophthalmology
Chuhan Wu, Xiaofang Zhang, Weilin Chen
Recently the combination of adaptive optics and ophthalmology has made great progress and become highly effective. The retina disease is diagnosed by retina imaging technique based on scanning optical system, so the scanning of eye requires optical system characterized by great ability of anti-moving and optical aberration correction. The adaptive optics possesses high level of adaptability and is available for real time imaging, which meets the requirement of medical retina detection with accurate images. Now the Scanning Laser Ophthalmoscope and the Optical Coherence Tomography are widely used, which are the core techniques in the area of medical retina detection. Based on the above techniques, in China, a few adaptive optics systems used for eye medical scanning have been designed by some researchers from The Institute of Optics And Electronics of CAS(The Chinese Academy of Sciences); some foreign research institutions have adopted other methods to eliminate the interference of eye moving and optical aberration; there are many relevant patents at home and abroad. In this paper, the principles and relevant technique details of the Scanning Laser Ophthalmoscope and the Optical Coherence Tomography are described. And the recent development and progress of adaptive optics in the field of eye retina imaging are analyzed and summarized.
Writing trace identification using ultraviolet Fourier-transform imaging spectroscopy technique
Hang Lyu, Ningfang Liao, Wenmin Wu, et al.
Conventional identification methods of writing traces commonly utilize imaging or spectroscopic techniques which work in visible to near infrared range or short-wave infrared range. Yet they cannot be applied in identifying the erased writing traces. In this study, we perform a research in identification of erased writing traces applying an ultraviolet Fouriertransform imaging spectrometer. Experiments of classifying the reflected ultraviolet spectra of erasable pens are made. The resulting hyperspectral images demonstrate that the erased writing traces on printing paper can be clearly identified by this ultraviolet imaging spectrometer.
Optical Measurement and Testing
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Application of liquid crystal on silicon spatial light modulator
A high performance 2D Spatial Light Phase Modulator named LCOS-SLM has been developed for wide range usefulness from basic researches to practical applications. We show the fundamental characteristics of LCOS-SLM device we developed, and introduce the activity examples such as the scientific researches of singular optics, fluorescence microscopy and adaptive optics. We have also applied the device for industrial applications in laser processing and machining, and medical application using adaptive optics system in scanning laser opthalmoscope.
Lens central thickness measurement by laser reflection-confocal technology
A new laser reflection-confocal thickness measurement (LRCTM) method is proposed for the reference lens central thickness calibration of the combined focal-length. LRCTM uses the reflector to reflect the convergent beam that come from the test lens to precisely identify the vertexes of test lens first and last surface, then uses ray tracing facet iterative algorithm to obtain lens central thickness. The test lens is put in the parallel light which makes its coaxality easier to adjust, and the optical path can be shortened with the reflector reflecting the convergent beam. LRCTM has high precision and concise structure, and it is suitable to be applied in the engineering. Preliminary experiments and analysis indicate that the relative measurement accuracy can be better than 0.03%.
Model-based calibration of an interferometric setup with a diffractive zoom-lens
Alexander Bielke, Goran Baer, Christof Pruss, et al.
The fabrication of aspheres and freeform surfaces requires a high-precision shape measurement of these elements. In terms of accuracy, interferometric systems provide the best performance for specular surfaces. To test aspherical lenses, it is necessary to adapt or partially adapt the test wavefront to the surface under test.

Recently, we have proposed an interferometric setup with a diffractive zoom-lens that includes two computer generated holograms for this purpose.1 Their surface phases are a combination of a cubic function for the adaption of aberrations and correction terms necessary to compensate substrate-induced errors. With this system based on Alvarez design a variable defocus and astigmatism controlled by a lateral shift of the second element is achieved.

One of the main challenges is the calibration of the system.

We use a black-box model2 recently introduced for a non-null test interferometer, the so called tilted wave interferometer3 (TWI). With it, the calibration data are calculated by solving an inverse problem. The system is divided in the two parts of illumination and imaging optics. By the solution of an inverse problem, we get a set of data, which describes separately the wavefronts of the illumination and imaging optics. The main difference to the TWI is the flexible diffractive element, which can be used in continuous positions. To combine the calibration data of a couple of positions with the exact placement, we designed alignment structures on the hologram. We will show the general functionality of this calibration and first simulation results.
Measurement of the thickness of side-polished fiber based on digital holography
Feng Wang, Jie Ma, Zhe Chen, et al.
A novel method to measure the remaining cladding thickness of side-polished fiber (SPF) was demonstrated by using the digital holography technology. By using angular spectrum method and accurate least-squares phase unwrapping method, the phase distribution of SPF could be reconstructed. Based on the reconstructed phase distribution, the remaining cladding thickness of SPF could be directly measured. It can reduce the errors due to fiber’s asymmetries and edge diffraction. This method could also be used to measure other special optical fibers such as photonic crystal fiber and nano-fiber.
Digital Holography and 3D Imaging
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Mueller matrix imaging by use of digital holography
Takanori Nomura, Toshitaka Kobata
A Mueller matrix imaging method by use of the characteristics of digital holography is proposed. In the proposed method, only two exposures are required to obtain the Mueller matrix. The Mueller matrix can be calculated from Stokes vectors. Stokes vectors can be obtained from two fully-complex amplitude distributions. Fully complex amplitude distributions can be obtained by digital holography. The optical experiments by using two kinds of specimens which are four linear polarizers and a quarter wave plate are shown to demonstrate the proposed method.
Research on high precision timing system based on FPGA non scanning imaging laser radar
Yanbo Fu, Shaokun Han, Liang Wang, et al.
The article introduced the system structure and imaging principle of no three-dimensional imaging laser radar. This paper used the XC7K325T XILINX chip of KINTEX 7 series and used temporal interpolation method to measure distance. Rough side used PLL multiplier 400MHZ, which reached 2.5ns time accuracy. This method used a thin chip delay chains carry resources to reach 50ps accuracy and greatly improved the accuracy of the timing of imaging.

Application technique used a delay line in APD array imaging system, such that each channel distance accuracy greatly improved. Echo signal by photoelectric conversion is completed by APD array detector, and designed by the impedance amplifier and other analog signal processing circuit. FPGA signal processing circuit is to complete the back-end processing, which is the timing function. FPGA array timer clock is to achieve coarse portion through timing, and delay line technique for measuring the length of time a non-integer multiple of the period of the laser pulse emission and the moment of reception, each stage of the delay units delay accuracy of sub ns magnitude, so as to achieve precision measuring part timers. With the above device was close imaging experiments, obtaining the 5 × 5 pixel imaging test results, presented to further improve system accuracy improved method.
Infrared Optics
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Studies on suppression methodology of internal radiation for satellite-borne infrared camera
Honggang Peng, Libing Jin, Jianfeng Liu, et al.
Infrared camera, which works on cryogenic or normal temperature, has thermal radiation inside. It is called interior radiation. In the space optical remote sensor, interior radiation will produce a lot of bad effects. Firstly, it can depress image contrast. What is more, dynamic range and integral time will be decreased. Lastly, interior radiation is one of the main factors that affect the measurement accuracy. So, restraining interior radiation is one of the key technologies to enhance the quality of infrared thermal imaging technology. In this paper, the typical technology of restraining interior radiation is summarized. At the end of the paper, blue prints for restraining interior radiation are proposed.
A high spatial resolution infrared scene projector
Yang Yang, Shi Nuo, Lang Zhou, et al.
An infrared scene projector with high spatial resolution using the visible to infrared transducer is described in this paper. The film transducer is fabricated by MEMS technology. The single pixel with 25×25μm in sizes and 35um at intervals in a transducer which is 76.2mm (3 inch) diameter is realized. So, the array size of the film transducer is more than 1024×1024. Illuminated by a visible light projector with different intensities, the equivalent black body temperature of the transducer could be varied in the range of 293K to 573K. The emission spectrum is similar with the blackbody and the gray scale is more than 200.
Design of four-mirror afocal principal system for wide field multichannel infrared imaging
Bin Hu, Ying Huang, Yan Li
The image space scanning system is widely used for multichannel infrared imaging to overcome the absence of large infrared focal plane array. The field of view of afocal system directly influences the time resolution of the image space scanning system. The field of view of afocal system is generally less than 7°. Therefore, it is significant to design larger field of view of afocal system for increasing time resolution. The method of four-mirror afocal system design based on primary aberration is explored. The structural parameters are calculated according to magnification and obscuration ratio of each mirror. The conic parameters are calculated according to primary aberration coefficients. The procedure for calculating initial structural parameters is programmed. Then a four-mirror afocal system is designed with an entrance pupil diameter of 200mm, a field of view of 20°×1°, the operating wave band of 3~12μm, compression ratio of 2.5 times and the distance of exit pupil of 620mm. The results indicate that the maximum root mean square (RMS) wavefront error is less than 0.042λ(λ=7.5μm), the maximum optical path difference(OPD) is less than λ/4(λ=3~12μm). It has high imaging quality and the modulation transfer function (MTF) is approached to the diffraction limit. The method of afocal system design can be widely used for wide field multichannel infrared imaging.
Solar multi-conjugate adaptive optics performance improvement
In order to overcome the effect of the atmospheric anisoplanatism, Multi-Conjugate Adaptive Optics (MCAO), which was developed based on turbulence correction by means of several deformable mirrors (DMs) conjugated to different altitude and by which the limit of a small corrected FOV that is achievable with AO is overcome and a wider FOV is able to be corrected, has been widely used to widen the field-of-view (FOV) of a solar telescope.

With the assistance of the multi-threaded Adaptive Optics Simulator (MAOS), we can make a 3D reconstruction of the distorted wavefront. The correction is applied by one or more DMs. This technique benefits from information about atmospheric turbulence at different layers, which can be used to reconstruct the wavefront extremely well. In MAOS, the sensors are either simulated as idealized wavefront gradient sensors, tip-tilt sensors based on the best Zernike fit, or a WFS using physical optics and incorporating user specified pixel characteristics and a matched filter pixel processing algorithm.

Only considering the atmospheric anisoplanatism, we focus on how the performance of a solar MCAO system is related to the numbers of DMs and their conjugate heights. We theoretically quantify the performance of the tomographic solar MCAO system. The results indicate that the tomographic AO system can improve the average Strehl ratio of a solar telescope by only employing one or two DMs conjugated to the optimum altitude. And the S.R. has a significant increase when more deformable mirrors are used.

Furthermore, we discuss the effects of DM conjugate altitude on the correction achievable by the MCAO system, and present the optimum DM conjugate altitudes.
Based on Narcissus of radiometric calibration technology
Libing Jin, Shaofan Tang, Jianfeng Liu, et al.
Thermal radiation is an inherent property of all objects. Generally, it is believed that the body, which temperature is above absolute zero, can keep generating infrared radiation. Infrared remote sensing, using of satellite-borne or airborne sensors, collects infrared information to identify the surface feature and inversion of surface parameters, temperature, etc. In order to get more accurately feature information, quantitative measurement is required. Infrared radiometric calibration is one of the key technologies of quantitative infrared remote sensing.

Most high-resolution thermal imaging systems are cooling. For the infrared optical system which is having a cooled detector, there are some special phenomenons. Since the temperature of the detector’s photosensitive surface is generally low, which is very different from system temperature, it is a very strong cold radiation source. Narcissus refers to the case that the cooled detector can “see” its own reflecting image, which may affect the image quality of infrared system seriously. But for radiometric calibration of satellite-borne infrared camera, it can sometimes take advantage of the narcissus instead of cold cryogenic radiometric calibration. In this paper, the use of narcissus to carry out radiometric calibration is summarized, and simulation results show the feasibility.
Novel Optical System Design
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Design and manufacture of angle modulated surface plasmon resonance spectrometer
Xinlei Zhou, Ke Chen, Xuefeng Mao, et al.
As an emerging biosensing technology, Surface Plasmon Resonance (SPR) technique, characterized by high sensitivity, label-free detection and real-time monitoring, has been extensively applied in biochemical analysis, environmental monitoring and refractive index measurement. In this paper, an angle modulated SPR spectrometer with high resolution is designed and manufactured. First, according to the modeling and simulation for the SPR spectrometer, several key parameters such as the light source, the thickness of golden film and Cr film are determined. Then, an angle modulated SPR spectrometer system based on 5-layers Kretchmann prism structure is developed for biochemical analysis. System performance is tested after the SPR spectrometer established. We test the power stability of the laser first, which is up to 1.504% (5min). Different concentrations of glycerol are measured to demarcate the system. Then, we measured the deionized water ten times continuously, and a resolution of 1.5×10-5 RIU is achieved. At last, different concentrations of glucose solution are measured, and the resonance angles are used to calculate the refractive index of the glucose solutions, which is more accurate than the result of Abbe refractometer. The relationship between concentration and refractive index is presented by liner fitting.
Polarization aberration control for hyper-NA lithographic projection optics at design stage
Xiaolin Liu, Yanqiu Li, Ke Liu
For hyper numerical aperture (NA) lithographic projection optics, not only scalar aberration but also polarization aberration (PA) should be controlled. Optical interfaces, coatings and intrinsic birefringence of lens materials can induce polarization aberration, so they cannot be ignored at design phase. There are few comprehensive and systematic studies on PA control at design phase for lithographic optics. In this paper, a lithographic projection lens with 1.2 of NA is designed, the root-mean-square of scalar aberration reach 1nm. For PA control of this system, firstly the influence of different subsets of polarization aberration on imaging performance is analyzed. The results indicate that the scalar transmission and diattenuation mainly cause critical dimension error (CDE), and the scalar phase and retardance mainly cause pattern placement error (PE). The results also show the diattenuation is the main controlled object in the process of PA control. Furthermore, a cooperative design strategy for PA control is proposed, which is to cooperate between custom coating design and the optimization of crystal orientation based on optical structure design. Through the cooperative design, the PA can be greatly reduced, especially diattenuation. The simulation results of the final system reveal that the dynamic range of CDE is suppressed from -12.7nm ~ +4.3nm to -0.1nm ~ +0.9nm after PA control, while keeping PE at an acceptable level.
Design of liquid lens based optical system for microfluidic chip detection
The precision of manufacturing and installing together with the flexibility is a serious challenge for laser induced fluorescent detector (LIFD) of microfluidic chip. In this paper, a focus tunable liquid lens based on liquid zoom system for LIFD with automatic adjustment is proposed. With the help of liquid zoom lens whose surface curvature can be varied continuously by current, the system can achieve a continuous zoom. Instead of using the traditional mechanical axial displacement scanning motion mechanism, the proposed zoom system can implement axial displacement scan by means of the well-designed autofocus feedback current control function. The simulation results show that the focal length variation range of the designed optical system is 4.87mm~ 8.40mm, which is also the axial scanning displacement range. The size of scanning spot is around 15μm when a 473nm wavelength laser is used, which can meet the demand of microfluidic chip detection. With this design, the required precision of the LIFD could be reduced significantly as well as costs. Moreover, it also makes the detection of microfluidic chip qualified to adapt to different size of detecting channel.
Optical design of multi-spectral optical system for infrared camera
Tianjin Tang
This paper studies about the multi-spectral imaging system and describes the design of dual-channel mirror-lens optical system with wide-field for multi-spectral sensor. Combined with the secondary imaging technology, it achieves the one hundred percent cold stop efficiency. Off-axis three-mirror reflective optics is adopted to provide an obstructive field of view and high spatial resolution over the wide-field, which is also shared by two channels. Independent relay lens are employed not only to extract the real exit-pupil matched with the cold shield, but also adjust the multiplication factors for infrared. The dichroic mirror and filters subdivide the wide spectral range into four bands, including mid-wavelength band and long-wavelength band. Each corresponds to respective field. The result shows that the Modulation Transfer Function of each band at respective fields is near the diffraction limit, which satisfies the needs of practical applications. The wavefront of the off-axis three-mirror reflective optics is also satisfactory, which is beneficial to the later alignment and measurement.
Analysis of Moiré minimization in color LED flat-panel display
Kai Lin, Ningfang Liao, Dazun Zhao, et al.
Moiré pattern can be readily observed in the case of superimposing two periodic structures. Recently, Moiré pattern, which degrades the quality of an image, become unavoidable in many LED display and three-dimensional displays, which consist of regular structures. Therefore, a model of moiré which fit the character of human vision is important to solve the problem of image quality degradation. In this paper, we modified the the model of Moiré which proposed by Amidror to evaluate the color moiré fringes, which consider the property of human vision system of contrast sensitivity. From the modified model we conclude that moiré minimization could have two lattice form an certain angle. The experimental results show that moiré pattern are vivid when the angle is 0°, 15°, 20° and 45°. However, the spatial frequency of Moiré in 10°, 25°, 30° and 35° are fine in spatial domain. It is also reveal that changing angle is simple and effective in alleviating remarkably Moiré pattern.
Poster Session
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Study on computer-aided alignment method of reflective zoom systems
Jide Zhou, Jun Chang, Guijuan Xie, et al.
Computer-aided alignment is an effective method to improve the imaging quality of high-precision, complex, and off-axis optical systems. However, how to determine the misalignment quickly, exactly and constantly is essential to the technology of computer-aided alignment. Owing to the varying optical characteristics of a zoom system, sensitivity matrices are used in the alignment rather than a single matrix. Thus, the processing of sensitivity matrices is important for the computer-aided alignment of the reflective zoom system. So, the total least squares is proposed in order to solve the problems of the numerical instability and the result inaccuracy which result from the solution of the least squares method directly. Finally, the simulant calculation is processed using the numerical analysis model established in the essay. The results demonstrate that the computation method is rational and effective.
Fabrication of periodically poled MgO doped LiNbO3 crystal and its application for optical parametric oscillator
Here we report that the properties of the poling electrode is one of the most important factors in fabrication of the ferroelectric crystal poling. In this paper, systematic researches on the property of electrode coating and the forms of electrode contact have been made. By using pulse applied electric field, the periodically poled grating of 31.2μm was prepared on a 1mm thick 5% MgO-doped Lithium Niobate crystal. A wavelength of 1064nm pulse laser was used as fundamental source to operate optical parametric oscillation experiment, and 1.141W of idler output power was obtained when PPMgOLN pumped by 1064nm of 5.567W at the temperature of 80℃. The maximum conversion efficiency from incident pump power to the idler output achieved to 20.1%.
Design of integration time for the space-borne multi-spectral imager with super-wide field of view based on freeform mirror
Huan Yin, Jun Zhu, Yongchao Zhang, et al.
The freeform optics is extensively applied in the fields of aerospace, aviation, lighting, medical treatment, et al.. For the linearly push-broom space-borne imager, integration time of different field of view can be affected by the optical system design of the imager, orbits of the satellite, maneuver of the attitudes, rotation of the Earth, light delay due to the refraction and transmission of the atmosphere, terrain error and so on. The dynamically imaging quality should be affected by the accuracy and adjusting mode of the integration time. In this paper, a new method which is especially appropriate to imaging model simulating and integration time calculating for the wide-field-of-view remote sensor is proposed. Then, the integration time of specified viewing direction for the imager with a single projection center and a super-wide field of view based on freeform mirror, which is mounted on a sun-synchronous orbit satellite, is calculated. And influence on imaging quality of adjusting integration time of different grouping modes for the focal plane assembly is analyzed. The results indicate that with the constraint condition of satellite roll angle and the modulation transfer function (MTF) influence factor no more than 20°and 2% respectively, integration time of all CCDs for the whole focal plane assembly divided into two groups with each adopting the uniform integration time, can fulfill the requirements of the imaging quality for the imager.
Research on all movable reflective zoom system with three mirrors
Guijuan Xie, Jun Chang, Jide Zhou, et al.
Traditional mechanical compensation zoom system realize the continuous change of the system focal length and continuous compensation of the image plane through the motion of the zooming group and compensating group according to the precise cam curve. With the increase demand of high zoom ratio and high quality system, and combined with the theory of reflective zoom system, this paper presents the all movable reflective zoom theory, focusing on the design and analysis of the three-mirror all movable reflective zoom system.
Spatial augmented reality based high accuracy human face projection
Dong Li, Jinghui Xie, Yufeng Li, et al.
This paper discusses the imaging principles and the technical difficulties of spatial augmented reality based human face projection. A novel geometry correction method is proposed to realize fast, high-accuracy face model projection. Using a depth camera to reconstruct the projected object, the relative position from the rendered model to the projector can be accessed and the initial projection image is generated. Then the projected image is distorted by using Bezier interpolation to guarantee that the projected texture matches with the object surface. The proposed method is under a simple process flow and can achieve high perception registration of virtual and real object. In addition, this method has a good performance in the condition that the reconstructed model is not exactly same with the rendered virtual model which extends its application area in the spatial augmented reality based human face projection.
Ejection-style self-imaging system design and finite element analysis for lunar lander
Qi Li, Qifeng Pan, Zhihai Xu, et al.
Landing on surface of planet is the most direct and effective means of deep space exploration. Taking the picture of lander and surrounding environment can monitor the working status of the lander, and different exploration tasks arranged different imaging methods. Apollo 11 achieved manned lunar landing, so astronauts leaved lunar lander and installed imaging camera; Curiosity rover is equipped MAHLI (Mars Hand Lens Imager) at the end of the robot arm, and capture the own image of the rover; Chang’E-3 consists of lander and rover, which can captured image each other. In this paper, taking into account the working conditions without rover, we designed an ejection-style self-imaging apparatus for lunar lander, which consists of the optical imaging system, the tumbler structure body and the ejector body. Ejector body is mounted on the lunar lander to eject the imaging system to the appropriate distance. To make the image of lander in the center field of view, the imaging system needs to be installed on a tumbler structure body to ensure that the optical axis of imaging system can be adjusted to the direction toward the lander. We designed and developed the imaging optical system, the mechanical structure of tumbler body and ejector body, deduced reasonable compression spiral spring parameter according to the application requirements, and completed finite element analysis of tumbler structure body in the fall process. The experiments on the sand, soil and gravel ground verify the feasibility of the design scheme.
Study of the impact of petal-shape mirror segmentation on 2 m segmented telescope
Cundong Lei, Liehua Zheng, Ying Che
The final optical design for a 2m infrared telescope with segmented primary mirror is presented in this paper, in response to the “2m segmented infrared telescope” proposal by Shanghai Institute of Technical Physics, Chinese Academy of Sciences for researching on the next generation of astro-physical mission. The segmented primary mirror adopts a circular center mirror and 8 petal-shape segment mirrors. To investigate the effects of intersegment gaps, position and figure errors of segments, a wavefront aberration representation is derived through aspheric surface equation, then, the linear relation between wavefront aberration and interference bright fringe is established, therefore, a linear retrieval algorithm of stitching tolerances base on the tolerances sensitivity matrix is proposed. In order to verify the algorithm, a simulation program is developed to analyze the fringe Zernike coefficients data of ZEMAX ray tracing, and the simulation results show that the maximum retrieval deviation is in the range of ±0.5%.
Low light level color night vision technology study on triple-band
Yichao Chen, Wengang Hu
Single-channel triple-band color night vision system is able to gain low-light color imagery. The core design idea of one-channel triple-band color night vision system is increasing a scanner than traditional low-light night vision system in the front of the image intensifier. The scanner is consisted of several filters which is used for dividing the emitted light or reflected light of the aim into three parts, R, G and B. Each part is taken a frame image respectively and then fused three frames into color imagery by Color Mapping Guidelines. The addition of filters makes the SNR of each frame image decreases, it means that images detail loss and gray value is low. To overcome this difficult, on the basis of three frame images fusion, a frame image of all band is added to fusion. Experimental results show that fused image which is fused by R, G, B and all band improve image brightness and detail information obviously through calculating the variance and entropy. This fused method is more conducive to the human eye.
The design of laser radar data acquisition system based on LabVIEW
Dalong Han, Shaokun Han, Jingya Cao, et al.
Lidar has been widely used in areas of ranging and imaging. To be able to perform real-time control of the entire system, this article designed a lidar data acquisition system based on LabVIEW and the PC system allows real-time display for data acquired by lidar system. Through the serial port, the PC system can adjust part of the laser radar system parameters, such as frequency, APD (Avalanche Photo Diode) bias, the echo threshold, etc in real-time. In this way, we achieve the instruction communication between the PC system and the lidar. In addition, the PC system can also acquire data from the lidar through the Ethernet. Through the practical test, the PC system can successfully acquire and display the echo signal measured by lidar system in real-time, and function of parameter adjustment is also very sensitive.
Modulation transfer function analysis for a digitally spectrum-controllable light source
Owing to the ability of generating designated spectrums as special requirements, spectrum-controllable light source has attracted huge interesting in several fields, e.g. medical science, industrial detection, defense-related testing. In principle, optical performance of a spectrum-controllable light source can be predicted by some transfer functions of the corresponding system, e.g. modulation transfer function (MTF). Unfortunately, the aforementioned research work is still lacking at present although it is meaningful for the optical design and evaluation of this new kind of light sources. Hence, a MTF model for a modified version of our previously-proposed spectrum-controllable light source system based on a Digital Micromirror Device (DMD) and an Offner dispersion configuration with a convex grating is deduced as an example. Related preliminary analyses have been present in this paper as well.
Design of signal receiving circuit of Lidar based on APD
This paper focuses on the study of Signal Receiving Circuit of Lidar. A signal receiving circuit for a pulsed time-of-flight (TOF) Lidar has been designed. This paper introduces the theories of Lidar and high speed photoelectric detection. The circuit consists of APD array, transimpedance amplifier and differential received amplifier. In the circuit, we use an APD as a photoelectric transformer, AD8015 is used in the circuit because it’s wide bandwidth, and single supply transimpedance. The AD8130 is a differential-to-single-ended amplifier with extremely high CMRR at high frequency, therefore it is used to converting differential signals to single-ended signals. In this paper, the laser pulse signal of 905nm wavelength, 20ns pulse width is used to detect experimentally verified. It is tested that the performance of the receiving circuit of Lidar satisfies the request of the principle system.
Foreign fiber detecting system based on multispectral technique
Qi Li, Shaokun Han, Ping Wang, et al.
This paper presents a foreign fiber detecting system based on multi-spectral technique. The absorption rate and the reflectivity of foreign fibers differently under different wavelengths of light so that the characteristics of the image has difference in the different light irradiation. Contrast pyramid image fusion algorithm and adaptive enhancement is improved to extracted the foreign fiber from the cotton background. The experimental results show that the single light source can detect 6 kinds of foreign fiber in cotton and multi-spectral detection can detect eight kinds.
The method of axial drift compensation of laser differential confocal microscopy based on zero-tracking
Yajie Wang, Han Cui, Yun Wang, et al.
Laser differential confocal microscopy (DCM) has advantages of high axial resolution and strong ability of focus identification. However, the imaging mechanism of point scanning needs long measurement time, in the process due to itself mechanical instability and the influence of environment vibration the axial drift of object position is inevitable, which will reduce lateral resolution of the DCM. To ensure the lateral resolution we propose an axial drift compensation method based on zero-tracking in this paper. The method takes advantage of the linear region of differential confocal axial response curve, gets axial drift by detecting the laser intensity; uses grating sensor to monitor the real-time axial drift of lifting stage and realizes closed-loop control; uses capacitive sensor of objective driver to measure its position. After getting the axial drift of object, the lifting stage and objective driver will be driven to compensate position according to the axial drift. This method is realized by using Visual Studio 2010, and the experiment demonstrates that the compensation precision of the proposed method can reach 6 nm. It is not only easy to implement, but also can compensate the axial drift actively and real-timely. Above all, this method improves the system stability of DCM effectively.
Athermal design of LWIR hybrid refractive/diffractive optical system
Thermal properties of diffractive optical element and method of design athermal hybrid infrared optical system are introduced. Athermal LWIR hybrid infrared optical system for no cooled staring detector is designed. The system consists of three lenses, the effective focal length is 100mm,the relative aperture is 1:1,the wavelength spectrum is 8~11μm, the field view is 14° and the total optical length is just 140mm. The result shows that the modulation transformation function at 17lp/mm is greater than 0.6 between -40-60°C,which prove that the system can work correctly at a large temperature range.
A nondestructive characterization system of periodically poled crystals
Huaixi Chen, Huang Zhou, Liyuan Chen, et al.
Periodically poled crystals are widely used as SHG, DFG, SFG, OPO and THz generation, and there is a broad application prospect in some areas such as the laser display, optical fiber communication, atmospheric exploration and military confrontation. At present, to get the parameters of periodically poled crystals, like duty ratio, the main method is chemical etching of the samples. In this paper, we present a nondestructive characterization system of periodically poled crystals. When we apply a proper high voltage on both sides of the periodically poled crystal, the refractive index difference of positive and negative domain will be increased and we can observe a clear domain pattern by the a microscope so as to obtain general information. Then a single frequency laser is prepared to radiate on +z surface of the periodically poled crystal, we can get some orders of diffraction according to diffraction optics principle. Finally, we can measure the parameters such as period, duty ratio by use of numerical analysis. The testing sample size of this system can be up to 60mm, The accuracy of the testing period can be 0.1μm, and the measurement range of duty ratio is 20%-50%.
Analysis of retroreflectors in stabilization system based on 3-D ray tracing matrix
Fan Fan, Qun Hao, Xuemin Cheng, et al.
In this paper we propose a ray tracing method in 3-D space. This method, based on ABCD ray transfer matrices in 2-D spacey, is deduced to establish the matrix expression for ray tracing in 3-D space. In order to solve the attitude control problem of the plan mirror in image stabilization system, we construct a mathematical model to describe the ray passing process from incident plane, mirror reflection, to the next optical plane. Two 2*2 ABCD submatrixes, for two 2-D subspaces, have been used to describe the propagation rules of ray in a 3-D space. Furthermore, the stabilization formula has been deduced. In this way, the offset angle for stabilization and coordinate of ray in space can be got. With the simulation experiments, we verified the effectiveness and accuracy of this mathematical model. The method we put forward has the characteristics of universal and simple. This 3-D ray tracing method could be further applied to other optical area.
Research on the image fusion and target extraction based on bionic compound eye system
People attach more and more importance to bionic compound eye due to its advantages such as small volume, large field of view and sensitivity to high-speed moving objects. Small field of view and large volume are the disadvantages of traditional image sensor and in order to avoid these defects, this paper intends to build a set of compound eye system based on insect compound eye structure and visual processing mechanism. In the center of this system is the primary sensor which has high resolution ratio. The primary sensor is surrounded by the other six sensors which have low resolution ratio. Based on this system, this paper will study the target image fusion and extraction method by using plane compound eye structure. This paper designs a control module which can combine the distinguishing features of high resolution image with local features of low resolution image so as to conduct target detection, recognition and location. Compared with traditional ways, the way of high resolution in the center and low resolution around makes this system own the advantages of high resolution and large field of view and enables the system to detect the object quickly and recognize the object accurately.
A study on deformable mirrors control and error analysis
A four-group stabilized zoom lens design of two focal-length-variable elements was discussed in our early work. The focal-length of the zoom system could be adjusted by tuning the surface shape of focal-length-variable element. In this paper, we propose to use the deformable mirror (DM) as the focal-length-variable device, and then we need to control the DM to forming the required surface shape and analyze the errors between actual surface and theoretic surface. This lays the foundation for analyzing the focusing zoom errors of the stabilized zoom lens in the zoom process. This paper firstly introduces a DM flatten method applied for using OKO Technologies’ Piezoelectric Deformable Mirror (PDM) and analyzes the high order errors of flattened surface with the help of ZYGO interferometer. Then we study the method of DM control to form sphere surfaces with different curvature. The analyses of the high order error of the actual surface and the measurement of the curvature range of the sphere surface are also included in this paper.
Segmented frequency offset compensation algorithm in coherent optical sub-sampling system
An inter-partitioned FFT algorithm is proposed to estimate the difference between the frequency of local optical sampling pulse and the signal to be sampled in coherent optical sampling system. By dividing the sampled data into several parts, the frequency difference of each part is estimated using FFT, respectively. The experiment demonstrated that, with the inter-partitioned FFT algorithm, the measured Q factor of 32GB QPSK signal is improved by 6dB, and matched the results obtained by the commercially available optical signal analyzer (EXFO PSO-200).
Design and fabrication of concave-convex lens for head mounted virtual reality 3D glasses
As a kind of light-weighted and convenient tool to achieve stereoscopic vision, virtual reality glasses are gaining more popularity nowadays. For these glasses, molded plastic lenses are often adopted to handle both the imaging property and the cost of massive production. However, the as-built performance of the glass depends on both the optical design and the injection molding process, and maintaining the profile of the lens during injection molding process presents particular challenges. In this paper, optical design is combined with processing simulation analysis to obtain a design result suitable for injection molding. Based on the design and analysis results, different experiments are done using high-quality equipment to optimize the process parameters of injection molding. Finally, a single concave-convex lens is designed with a field-of-view of 90° for the virtual reality 3D glasses. The as-built profile error of the glass lens is controlled within 5μm, which indicates that the designed shape of the lens is fairly realized and the designed optical performance can thus be achieved.
Design and stray light analysis of ultra-thin geometrical waveguide
Qiwei Wang, Dewen Cheng, Qichao Hou, et al.
Nowadays, the waveguide has the advantages of small thickness and light weight so that it attracts more and more attention in the field of near-eye display. However, as a major problem, stray lights generated in the waveguide seriously degrade the display quality. In this paper, a geometrical waveguide with a beam-splitting mirror array (BSMA) is designed by using the non-sequential ray-tracing software LightTools, and great efforts are paid to study the causes and solutions of the stray light. With mass calculation and optimization based on the criterion of stray light/useful light ratio, an optimum design with the least amount of stray lights is found. To further eliminate the stray light, a novel structure that couples the rays into the waveguide is designed. The optimized waveguide has a FOV of 36° in the pupil-expanding direction of the waveguide, with stray light energy reduced to 1% over the useful light, the exit pupil diameter is 11.6mm at an eye relief of 20mm and the thickness is 2.4mm.
Design of a novel panoramic lens without central blindness
The panoramic lenses are getting more and more popular in recent years. However, these lenses have the drawback of obscuring the rays of the coaxial fields, thus cause blind area in the center field of vision. We present a novel panoramic system consisting of two optical channels to overcome this issue, the system has a field of view (FOV) reaching 200 in vertical and 360 in horizontal direction without blindness area. The two channels have different focal lengths, providing design flexibility to meet application requirements where the center FOV or the marginal FOV is of more interest. The system has no half-reflecting surfaces to ensure high transmission ratio, but this feature greatly increase the design difficulty. The distortion of the novel lens is much smaller than traditional panoramic lenses since the distortion has two node points. Due to the ability of information acquisition in real-time and wide-angle, the novel panoramic lens would be very useful for a variety of real-world applications such as surveillance, short-throw projector and pilotless automobile.
Research on high precision centering assembly method of roll edge optical elements
In order to improve the imaging quality of target imaging optical system, in the special environment of large temperature difference, the centering assembly precision of roll edge optical elements was studied. According to the hole-axis coordinate error theory of mechanics, by analyzing the factors affected the precision of mechanical heating surface, combining with the existing method to eliminate error and centering assembly process, a new kind of high precision centering assembly method was put forward. Using additional grinding device to grinding roll edge of optical element, eliminate the machining error on the surface of the mechanical hot working, thus improve the centering assembly precision between the roll edge optical element and lens tube. The result of experiment shows that the centering precision can reach less than 3μm when assembled optical element after roll edge using new centering assembly method, and improved by 25% compared to the traditional method of roll edge optical elements are assembled directly after hot working. New assembly method with additional grinding device can improve the centering assembly precision of roll edge optical elements, and greatly reduce the difficulty of optical design of such optical imaging system using in large temperature difference environment, when meet the same image quality.
Research on design method of spaceborne imaging spectrometer system based on telecentric optical system
Imaging spectrometer is widely applied in the field of space remote sensing. Dispersion imaging spectrometer with prism or grating is developed rapidly and used widely. It is developed to the direction of high performance and miniaturization, such as large field of view, high resolution, small volume, etc. For meeting the demand of the development, by comparing the characteristics and the situation of development and application about the two kinds of spectrometer, based on the imaging theory of telecentric optical system, the article studied a design method of prism dispersion imaging spectrometer with telecentric Off-axis Three-Mirror imaging system. The instrument designed by using this method has smaller volume and weight than traditional instrument. It overcomes the biggest defect that traditional prism dispersion imaging spectrometer is bigger, increases its advantages in actual use in contrast to grating dispersion imaging spectrometer, and promotes the development and application of prism dispersion imaging spectrometer.
A design of PAL with astigmatism
Yefei Wei, Huazhong Xiang, Tianfeng Zhu, et al.
Progressive addition lens (PAL) is designed for those who suffer from myopia and presbyopia to have a clear vision from a far distance to a nearby distance. Additionally there are many people that also suffer from astigmatism and need to be corrected. The cylinder power can’t be simply added to the diopter of the PAL directly, because the diopter of the PAL needs to be changed smoothly. A methods has been proposed in this article to solve the problem, the freeform surface height of a PAL without astigmatism and the cylindrical lens surface height for the correction of astigmatism are calculated separately. The both two surface heights were added together, then the final surface is produced and shown with the both properties of PALs and cylindrical lenses used to correct the astigmatism.
The centering and leveling adjustment and control technology for the ultra-precision turntable
Yanrong Tian, Yun Wang, Longxiao Wang, et al.
In order to realize the centering and leveling adjustment in large aperture spherical and aspheric surface shape measurement, by combining with the aerostatic bearing rotary shaft, working platform, high performance servo motor, photoelectric encoder, the micro displacement actuator of XYZ axis, sensor and Renishaw circular grating ,a set of fast and ultra-precision centering and leveling adjustment system is developed .The system is based on large range of air lubrication technology for high precision aerostatic bearing turntable, using the principle of three point supporting method, and the driving of tens nanometer resolution are provided by a piezoelectric micro displacement actuator. To realize the automatical centering and leveling adjustment in the large aperture spherical and aspheric surface shape measurement system, a software control program is designed with VC++. Through experimental test: centering adjusting operation can eventually converges to 0.5μm, leveling adjusting operation can eventually converges to 0.2 ", the time of adjusting can be less than 120 s. The experimental results shows that, compared with the previous system, the structure of the developed measurement and control system is more simple, more flexible, it can meet the demands of high precision, high resolution, large adjusting range, no friction, easy to drive, and high bearing stiffness etc in eccentric adjusting operation of optical precision measurement well.