Contents
2016
Volume: 36 Issue 8
43 Article(s)
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Research Article
Research on White Light Color Temperature Deviation Based on Tricolor LEDs
Mei Jianjian, and Liu Lilan
In order to improve lighting quality and achieve accurate and adjustable dynamic correlated color temperature of white light, a method of tricolor light mixing is used. Based on the colorimetric light color design, one mathematical model of RGB tricolor mixing is established. Appropriate parameters of tricolor LEDs areIn order to improve lighting quality and achieve accurate and adjustable dynamic correlated color temperature of white light, a method of tricolor light mixing is used. Based on the colorimetric light color design, one mathematical model of RGB tricolor mixing is established. Appropriate parameters of tricolor LEDs are chosen to conduct the experiment of mixing white light with different correlated color temperature between 3000 K and 7500 K. The experimental color temperature of white light has a large deviation from the theoretical one. Further analysis tells us that the junction temperature is the main factor influencing the color temperature deviation. By adjusting the duty ratio to correct the output of the tricolor luminous flux, the relationship between the duty ratio and the target correlated color temperature is obtained. The experimental results show that the corrected color temperature deviation is within 50 K. The parameters for mixing white light sources match well with the theoretical ones and the white light source with different correlated color temperature is achieved. Temperature compensation can be realized by adjusting the tricolor luminous flux..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 833001 (2016)
Homogeneous Polynomial Model for Colorimetric Characterization of Camera with Variable Settings
Fang Jingyu, Xu Haisong, Wang Zhehong, and Wu Xiaomin
Based on the imaging principle of cameras, a transformation equation among response value under different capture settings is established, and a colorimetric characterization model based on the homogeneous polynomial regression is proposed, which avoids errors caused by the nonlinear extrapolation in the traditional poBased on the imaging principle of cameras, a transformation equation among response value under different capture settings is established, and a colorimetric characterization model based on the homogeneous polynomial regression is proposed, which avoids errors caused by the nonlinear extrapolation in the traditional polynomial model. A Nikon D3x digital camera is employed to conduct the colorimetric characterization experiment under variable capture settings and the effect of different numbers of terms on characterization accuracy is analyzed. The experimental results show that the homogeneous polynomial model is applicable to describing the colorimetric characterization of cameras with varible capture settings, and it shows the best performance with 6 or 7 terms. In the experiment of 28 kinds of LED light resources with 4 kinds of color temperature and 7 illumination levels, but under fixed color temperature and variable illumination, the predicted color accuracy is superior to 1.5 CIELAB units and it is comparable to the accuracy from the polynomial model with fixed parameters and light sources. In contrast, under the simultaneous change of color temperature and illumination levels, the average chromatic aberration is less than 2.0 CIELAB units, which fulfills the colorimetric accuracy requirement in the practical application of cameras..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 833002 (2016)
Atmospheric Optics and Oceanic Optics
Stochastic Characteristic Analysis of Time Series of Extinction Coefficient in Chengdu
Sun Huanhuan, Ni Changjian, Cui Lei, and Wang Chao
A correct understanding of the evolution characteristics of the extinction coefficient series under different humidity conditions is the premise and foundation to establish the correction model of atmospheric particulate matter humidity. Using the data of mass concentration of PM2.5 (excluding rainy days), together witA correct understanding of the evolution characteristics of the extinction coefficient series under different humidity conditions is the premise and foundation to establish the correction model of atmospheric particulate matter humidity. Using the data of mass concentration of PM2.5 (excluding rainy days), together with the homologous surface visibility and relative humidity data from June 2013 to May 2014 at 4th Section, South Renmin Road of Chengdu, the corresponding unit mass extinction coefficient time series is retrieved. The complex evolution of the extinction coefficient during moisture absorption is briefly discussed, and the non-universality of the existing humidity correction model is exemplified. Based on the reconstruction of phase space theories, the optimal delay time f and the embedding dimension m are determined, and several characteristic quantities, including the saturation correlation dimension, the maximum Lyapunov index and the Komogorove entropy, are also calculated. The results show that this series has the characteristics of low dimensional chaos. The Cao method is applied to excluding the possibility that the unit mass extinction coefficient time series is nonlinear. By adopting the surrogate data method, the time series is finally proved to be stochastic. The results not only clarify the characteristics of the unit mass extinction coefficient series, but also establish the theoretical foundation for the improvement of the atmospheric particulate matter humidity..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 801001 (2016)
Research of Modulation Transfer Function of Underwater Imaging System in Turbulent Environment
Sun Liying, Xia Min, Han Jiefei, and Yang Kecheng
In order to study the effect of turbulence on submarine imaging system, an optical experiment system is built using pump and tank to make the turbulence area with controllable water flow velocity. The CCD is used to imaging the sinusoidal fringe and the image quality is analyzed. The imaging results with various water In order to study the effect of turbulence on submarine imaging system, an optical experiment system is built using pump and tank to make the turbulence area with controllable water flow velocity. The CCD is used to imaging the sinusoidal fringe and the image quality is analyzed. The imaging results with various water turbidity and flow velocity are obtained through the control of imaging experiment environment. The modulation transfer function (MTF) is extracted to analyze the results. Experimental results show that the particle scattering causes modulation contrast declines in the whole spatial frequency. The effect caused by turbulence scattering is more obvious on the high frequency. With the increase of inlet flow velocity and the attenuation coefficient, the MTF curves show quick downward trends. The image distortion and decline of resolution are caused by the particle and turbulence scattering in the turbulent environment..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 801002 (2016)
Measurement and Analysis of Integral Optical Turbulence at Western Typical Zones in China
Chen Xiaowei, Li Xuebin, Liu Qing, Sun Gang, Zhang Shouchuan, Zhu Wenyue, and Weng Ningquan
The temporal and statistical properties of atmospheric coherence length and isoplanatic angle are investigated, based on the long-term measured datum of synthetic measuring system of atmospheric coherence length and isoplanatic angle in the west of China. Meanwhile the mean and standard deviation of atmospheric coherenThe temporal and statistical properties of atmospheric coherence length and isoplanatic angle are investigated, based on the long-term measured datum of synthetic measuring system of atmospheric coherence length and isoplanatic angle in the west of China. Meanwhile the mean and standard deviation of atmospheric coherence length and isoplanatic angle in three periods of daytime, nighttime and dusk are given. The probability distributions of initial data show that both atmospheric coherence length and isoplanatic angle are approximately satisfied with log-normal distribution. Besides, the distribution deviation between the sample distribution and log-normal distribution is estimated by sample skewness and sample kurtosis. The correlation between monthly mean of atmospheric coherence length and isoplanatic angle is analyzed, and the effects of the magnitude of upper air and surface turbulence on atmospheric coherence length and isoplanatic angle are evaluated qualitatively..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 801003 (2016)
Fiber Optics and Optical Communications
Phase Noise Cancellation for Coherent Optical OFDM System Based on Polarization Diversity
Yu Jun, Huang Mingliu, Zou Yaozhao, Wang Wang, and Song Yingxiong
The coherent optical orthogonal frequency division multiplexing (OFDM) system based on polarization diversity is proposed. However, the coherent detection is very sensitive to phase noise and the polarization diversity reception can produce additional multiplicative phase noise. Therefore, a phase noise cancellation scThe coherent optical orthogonal frequency division multiplexing (OFDM) system based on polarization diversity is proposed. However, the coherent detection is very sensitive to phase noise and the polarization diversity reception can produce additional multiplicative phase noise. Therefore, a phase noise cancellation scheme based on digital signal processor with coherent optical OFDM system is proposed. Error-free transmission of an 8 Gbit/s 16 quadrature amplitude modulation OFDM signal over a 100 km single mode fiber is experimentally demonstrated. After the coherent detection, the phase noise through digital signal processing is cancelled, and the experimental constellation diagrams of the signals after phase noise cancellation is analyzed. In addition, the coherent optical OFDM link based on polarization diversity after phase noise cancelling is compared with other coherent optical OFDM link as the advantage of this scheme is verified..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 806001 (2016)
Golay-Differential Pulse Hybrid Coding Technology Based on Brillouin Optical Time Domain Analysis Sensors
Luo Yuan, Yan Lianshan, Shao Liyang, Li Zonglei, Pan Wei, and Luo Bin
In Brillouinoptical time domain analysis (BOTDA) sensing system, spatial resolution and sensing distance are restricted by each other. So a novel hybrid pulse coding technology which combines Golay code with differential pulse-width pair (DPP) is proposed. Compared with DPP based on Golay-BOTDA, this method shows a 6 dIn Brillouinoptical time domain analysis (BOTDA) sensing system, spatial resolution and sensing distance are restricted by each other. So a novel hybrid pulse coding technology which combines Golay code with differential pulse-width pair (DPP) is proposed. Compared with DPP based on Golay-BOTDA, this method shows a 6 dB enhancement of signal-to-noise ratio (SNR) in theory at the same sample times, as the Golay code can improve the SNR of the system and the DPP technology can ameliorate the spatial resolution. The experimental results indicate that 1.6 m spatial resolution could be achieved at the end of the fiber with the length of 25 km by using the hybrid coding technology, while the hybrid coding technology can get 4.08 dB enhancement of SNR compared with DPP based on Golay-BOTDA..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 806002 (2016)
Effect of Double-Cylinder Winding on Temperature Performance of Interferometric Fiber Optic Gyroscope
Li Xuyou, Ling Weiwei, Xu Zhenlong, Wei Yanhui, and Yang Hanrui
By deeply analyzing the characteristics of interferometric fiber optic gyroscope sensitive ring, a double-cylinder (D-CYL) winding method with a simple process is proposed. Simulation by finite element method is conducted to analyze the transient heat transfer performance of the D-CYL winding coils and a comparative anBy deeply analyzing the characteristics of interferometric fiber optic gyroscope sensitive ring, a double-cylinder (D-CYL) winding method with a simple process is proposed. Simulation by finite element method is conducted to analyze the transient heat transfer performance of the D-CYL winding coils and a comparative analysis is made to find out the different effects of D-CYL and cross winding methods on fiber optic gyroscope under the same variable temperature. The results show that, under a symmetry temperature environment, the D-CYL winding method shows almost the same performance in suppressing phase drift error as the cross winding method, and both errors are within 0.01 (°)/h, which is consistent with that from the theoretical analysis..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 806003 (2016)
Modified Photon Counting Communication Method for Underwater Application
Han Biao, Zhao Wei, Wang Wei, Su Yulong, and Liu Jifang
Underwater laser communication is influenced by the absorption and scattering of water, which causes severe signal energy attenuation during propagation. Laser communication based on the photon counting is considered as an effective way to resist signal loss and increase communication distance because of its ultra-highUnderwater laser communication is influenced by the absorption and scattering of water, which causes severe signal energy attenuation during propagation. Laser communication based on the photon counting is considered as an effective way to resist signal loss and increase communication distance because of its ultra-high detection sensitivity. However, since communication data recovery is usually realized by detecting electrical pulse at the output of single photon detector directly in traditional photon counting communication, the communication bit error rate would be easily influenced by background light noise. In this paper, an improved method is proposed and studied to solve this problem. In our approach, the photons arrived at the communication receiver are converted into electrical pulses by single photon detector first. Then, communication data is recovered through counting the electrical pulse number on unit time. The experimental result shows that detection sensitivity of 84.24 bit-1 can be realized by the proposed method, when the communication wavelength is 532 nm, the communication rate is 50 kb/s, and the signal to noise ratio is 5.14. The novel approach proposed in this paper provides a new technical idea for high-sensitivity underwater laser communication..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 806004 (2016)
Red, Green and Blue Laser Emissions from H2-Filled Hollow-Core Fiber by Stimulated Raman Scattering
Gu Bo, Chen Yubin, and Wang Zefeng
The experiment of red, green and blue laser generating simultaneously in gas-filled negative curvature hollow-core fiber is reported. A hydrogen-filled Ice-cream negative curvature hollow-core fiber is pumped with a high peak-power, narrow linewidth, subnanosecond pulsed 1064 nm microchip laser, generating 737.6, 564.2The experiment of red, green and blue laser generating simultaneously in gas-filled negative curvature hollow-core fiber is reported. A hydrogen-filled Ice-cream negative curvature hollow-core fiber is pumped with a high peak-power, narrow linewidth, subnanosecond pulsed 1064 nm microchip laser, generating 737.6, 564.2, 457.1 nm pulses corresponding to the first, second and third vibrational anti-Stokes waves by cascaded stimulated Raman scattering of hydrogen molecules. The relative intensities and output modes of red, green and blue laser can be controlled by adjusting the pump power and the pressure of hydrogen filled in the hollow-core fiber..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 806005 (2016)
Slot Synchronization Aided by Serial Concatenated Pulse Position Modulation Code System
Xiang Jingsong, Wu Tao, Huang Sheng, and Liu Huanlin
Aiming at deep space optical pulse position modulation (PPM) communications, based on the principle of expectation-maximization (EM) timing error estimation, a new solution of optical PPM slot synchronization based on serial concatenated pulse position modulation (SCPPM) code is studied. Due to that the expected value Aiming at deep space optical pulse position modulation (PPM) communications, based on the principle of expectation-maximization (EM) timing error estimation, a new solution of optical PPM slot synchronization based on serial concatenated pulse position modulation (SCPPM) code is studied. Due to that the expected value of EM estimation can not be got by the standard SCPPM decoding method, a method to convert the soft information output from SCPPM decoder to the expected value of each PPM slot is proposed. Firstly, the hard decision of output from the SCPPM decoder is made, and the accumulator state through accumulation module is got. Then, a mapping method according to the former accumulator state is chosen, and the probability and expectation of each PPM slot is obtained. Finally, EM algorithm is used to predict the clock offset and then to obtain the best sampling point. According to the simulation results, for the asynchronous sampling signal with two times PPM slot frequency, the proposed method can effectively achieve the PPM slot synchronization under the condition of the clock error among －0.5~0.5 PPM slots..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 806006 (2016)
Flexible Decision-Aided Maximum Likelihood Phase Estimation for Optical Coherent QAM Signals
Wang Ping, Chen Jian, You Xiaodi, Ma Zhaohui, Liu Xue, and Yu Changyuan
Flexible decision-aided maximum likelihood (DAML) phase estimation method is proposed, which extends from the phase shifted keying (PSK) system to the quadrature amplitude modulation (QAM) system, and the phase estimation error is derived. Simulation results show that the flexible DAML has a lower bound of bit error raFlexible decision-aided maximum likelihood (DAML) phase estimation method is proposed, which extends from the phase shifted keying (PSK) system to the quadrature amplitude modulation (QAM) system, and the phase estimation error is derived. Simulation results show that the flexible DAML has a lower bound of bit error ratio (BER) for different block lengths, which can eliminate the block length effect from the conventional DAML and effectively reduce the requirement of signal phase fluctuation in the process of signal detection, thereby it loosens the restriction on laser linewidth in coherent optical systems..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 806007 (2016)
Low-Complexity Optical Space-Time Trellis Code
Wang Huiqin, Xiao Bo, Jia Fei, Cao Minghua, and Sun Jianfeng
According to the characteristics of optical communication, a low-complexity optical space time trellis code based on pulse position modulation(PPM) is proposed. The scheme is based on the idea of delay diversity of the transmitter, and establishes the correlation of signals in time and space. The feedback interface canAccording to the characteristics of optical communication, a low-complexity optical space time trellis code based on pulse position modulation(PPM) is proposed. The scheme is based on the idea of delay diversity of the transmitter, and establishes the correlation of signals in time and space. The feedback interface cancellation algorithm (FICA) is used at the receiving end, and the maximum likelihood decision is used to decode the eliminated interference signal. The proposed scheme reduces the complexity of decoding by sacrificing the performance of transmitting diversity, which reduces the computational requirement of the system. The computational complexities of the algorithm and the Viterbi decoding algorithm are analyzed with the antenna numbers of 2 and 3. The simulation results show that when diversity gain is the same，the decoding complexities of the proposed scheme are reduced by 93.75% and 95.84% respectively, compared with the Viterbi decoding algorithm, and the deteriorations of the bit error rate performance are only 3 dB and 4.77 dB..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 806008 (2016)
Imaging Systems
Pixelated Source Mask Optimization Based on Multi Chromosome Genetic Algorithm
Yang Chaoxing, Li Sikun, and Wang Xiangzhao
A pixelated source mask optimization (SMO) method based on multi chromosome genetic algorithm (GA) is introduced. This method uses multi chromosome genetic algorithm to optimize the pixelated source and pixelated mask simultaneously. In comparison with the single chromosome GASMO method that uses rectilinear mask repreA pixelated source mask optimization (SMO) method based on multi chromosome genetic algorithm (GA) is introduced. This method uses multi chromosome genetic algorithm to optimize the pixelated source and pixelated mask simultaneously. In comparison with the single chromosome GASMO method that uses rectilinear mask representation, multi chromosome GASMO method can get high imaging quality and fast convergence speed. Simulation results show that the multi chromosome method can get an optimum solution with the fitness value is 7.6%, which is smaller than that of the single chromosome method. The multi chromosome method only needs 132 generations to converge to an optimal result with the fitness value of 5200, 127 generations less than the single chromosome method, and the optimization convergence speed is accelerated..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 811001 (2016)
Measuring Method of Polarization Aberration Based on Vector Aerial Image of Alternating Phase-shift Mask
Shen Lina, Wang Xiangzhao, Li Sikun, Yan Guanyong, Zhu Boer, Meng Zejiang, and Zhang Heng
A measuring method of polarization aberration based on aerial image of alternating phase-shift mask is proposed. The polarization aberration is represented by Pauli-Zernike coefficients. The image placement error and best focus shift are measured by image sensor at multiple illumination settings, combined with X and Y A measuring method of polarization aberration based on aerial image of alternating phase-shift mask is proposed. The polarization aberration is represented by Pauli-Zernike coefficients. The image placement error and best focus shift are measured by image sensor at multiple illumination settings, combined with X and Y linearly polarized illuminating light. The Pauli-Zernike coefficients are retrieved using the calibrated sensitivity matrix of polarization aberration. The validity of this proposed method is verified by numerical simulations, and the results indicate that the measuring accuracy is less than 3.07 mλ..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 811003 (2016)
Instrumentation, Measurement and Metrology
Process Dependency of Focusing and Leveling Measurement System in Nanoscale Lithography
Sun Yuwen, Li Shiguang, Ye Tianchun, and Zong Mingcheng
With the development of semiconductor manufacturing to 1x nm technological node, focus control accuracy of lithography needs to meet dozens of nanometers. In the range of nanoscale, integrated circuit (IC) process on silicon wafer has an important impact on the measurement accuracy of the focusing and leveling system. With the development of semiconductor manufacturing to 1x nm technological node, focus control accuracy of lithography needs to meet dozens of nanometers. In the range of nanoscale, integrated circuit (IC) process on silicon wafer has an important impact on the measurement accuracy of the focusing and leveling system. A process dependent error model is established based on actual focusing and leveling optical system model, trigonometry and Moire measurement principle. Research shows that process dependent error mainly results from the multiple reflections inside the photoresist. Simulation is conducted with three different photoresists. The simulation results indicate that process dependent error of different photoresists has the same trend as the photoresist thickness and process dependent error decreases with the increase of incident angle (45°~85°). Seven processed silicon wafers are measured on the experimental setup. The statistical mean of the difference between the experimental measurement and the theoretical model calculation is less than 6 nm. The results show that, in order to reduce the process dependent error, it is necessary to increase the angle of incidence of focusing and leveling system in lithography and improve the uniformity of the photoresist coating..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 812001 (2016)
Application of Adaptive Weighted Centroid Algorithm in High Accuracy Star Localization
Liu Nannan, Xu Shuyan, Cao Xiaotao, and Wang Dong
An adaptive weighted centroid localization algorithm is proposed to solve the problems caused compositely by the high magnitude stars, the image motion and the aberration of optical system in high accuracy star localization. A mathematical model based on the maximum likelihood estimation is derived and built to performAn adaptive weighted centroid localization algorithm is proposed to solve the problems caused compositely by the high magnitude stars, the image motion and the aberration of optical system in high accuracy star localization. A mathematical model based on the maximum likelihood estimation is derived and built to perform numerical simulations. The results show that the localization accuracy of the algorithm proposed is increased by over 50% compared with that of the traditional star localization algorithms such as centroid method, weighted centroid method and Gaussian fitting method. The proposed algorithm has good convergence rate, and the centroid location error is relatively stable after five iterations, which can meet the real-time requirement in practical applications.<>.
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 812002 (2016)
Measurement Method for Transmission Wavefront of Large Aperture Window
Liu Qiang, Xu Chen, and Li Xinnan
The windows are often used in the telescopes and large aperture collimators. A window is placed at the front of the system, and its transmitted wavefront error has great influence on the image quality of the system. The way of measurement determines the machining precision. When the window is greater than the current cThe windows are often used in the telescopes and large aperture collimators. A window is placed at the front of the system, and its transmitted wavefront error has great influence on the image quality of the system. The way of measurement determines the machining precision. When the window is greater than the current commercial plane interferometer with the maximum diameter of Φ800 mm, it′s unable to carry out the full aperture testing. To solve this problem, a new method for testing full aperture window transmission is put forward that the window is put in the optical system consisting of a spherical interferometer and a concave spherical mirror with big diameter and long focal length. The method has been successfully used to test a fused silica window, with Φ856 mm diameter and 35 mm thickness. The root mean square (RMS) value of measurement result is 0.0191λ(λ=632.8 nm), which satisfies the design requirements. The feasibility of this method used in transmission measurement of large aperture windows is verified..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 812003 (2016)
Polarization Correction for Grating Dispersive Imaging Spectrometer
Wang Hongbo, Hu Xiuqing, Zhang Lu3, Zhang Chongbing, Ren Baichuan, Huang Xiaoxian, and Wei Jun
The grating dispersive imaging spectrometer is used for ocean color remote sensing. It is operated in the visible and near infrared range. A push-broom method is applied to the instrument. 15 spectral channels and 1024 cross-track pixels comprising a total field of view of 14.2° are arranged on the focal plane. ThThe grating dispersive imaging spectrometer is used for ocean color remote sensing. It is operated in the visible and near infrared range. A push-broom method is applied to the instrument. 15 spectral channels and 1024 cross-track pixels comprising a total field of view of 14.2° are arranged on the focal plane. The spectral channels are sensitive to the polarization of the incident light. To improve the radiation measurement precision at the top of atmosphere, it is necessary to understand the polarization response characteristics of the instrument, including the polarization sensitivity and the phase angle. A polarization testing system is established before launching. The polarization sensitivity and the phase angle data of all spectral channels, which vary with the channel No. and the cross-track pixel, are measured. The 980 nm band has the highest polarization sensitivity and its mean of the cross-track pixels is about 4.69%, while the 443 nm band has the lowest sensitivity with a mean of about 1.81%. The sensitivity of middle field of view is lower than that at the edges in the same channel. A polarization response correction method is proposed for the imaging spectrometer. Verification experiments are performed by introducing the partially polarized light with a known polarization state. The result shows that the radiometric uncertainty caused by polarization response of the instrument can be reduced by 1%-6%..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 812004 (2016)
Method for Binary Grating Generation Using Defocused Projection for Three-Dimensional Measurement
Zhao Liwei, Da Feipeng, and Zheng Dongliang
Projector defocusing technique can eliminate projector nonlinearity in three-dimensional measurement of grating projection. However, the high frequency harmonics produced by binary grating can weaken the sinusoidal feature of grating and generate phase errors. A new method is proposed to generate binary grating patternProjector defocusing technique can eliminate projector nonlinearity in three-dimensional measurement of grating projection. However, the high frequency harmonics produced by binary grating can weaken the sinusoidal feature of grating and generate phase errors. A new method is proposed to generate binary grating patterns. Based on symmetry and periodicity of sinusoidal grating pattern, this method selects a smaller binary patch. Then the selected patch is randomly initialized, the binary patch is optimized through multi-pixels′ mutation, and the binary grating pattern of full size pattern is generated according to the optimized binary patch. Finally, combined with phase-shifting algorithm, required phase information for three-dimensional measurement is retrieved under the environment of defocusing measurement for the projector. Compared with the generation method of traditional binary grating patterns, the proposed method can certify high-quality phase information acquisition and suitable for the measurement environment of different defocusing amounts. Simulations and experiments are carried out to verify that the proposed method is more proper for three-dimensional measurement of defocused projection..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 812005 (2016)
Retrace Error Correction for Non-Null Testing of Optical Aspheric Surface
Shi Tu, Zang Zhongming, Liu Dong, Yang Yongying, Chong Shiyao, Zhang Lei, Bai Jian, Shen Yibing, Miao Liang, and Huang Wei
Non-null testing methods of optical aspheric surface are more common than the null testing ones. The mechanism of the production of retrace error in aspheric non-null testing are analyzed in detail. The retrace error is divided into predictable part and unpredictable part by combing calibration method and its influenceNon-null testing methods of optical aspheric surface are more common than the null testing ones. The mechanism of the production of retrace error in aspheric non-null testing are analyzed in detail. The retrace error is divided into predictable part and unpredictable part by combing calibration method and its influence on final testing result is analyzed. The principle of common retrace error calibration method in actual testing is introduced. The correction effects of each method on aspheric surface under test with different asphericities and different surface errors are compared by simulation experiment. The correction ability of retrace error of each method is analyzed by combing the method principle and simulation result, and the application range is summarized..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 812006 (2016)
Lateral Displacement Error Calibration Method for Point-Diffraction Wavefront Interferometric Measurement Without Imaging Lens
Xu Yangbo, Wang Daodang, Wang Zhichao, Liu Wei, Kong Ming, Zhao Jun, and Zhu Baohua
In order to minimize the error, the non-lens imaging method is applied in the interferometric measurement of point-diffraction spherical wavefront precision. In the case of high numerical aperture and large lateral displacement, significant additional systematic error can be introduced into point-diffraction wavefront In order to minimize the error, the non-lens imaging method is applied in the interferometric measurement of point-diffraction spherical wavefront precision. In the case of high numerical aperture and large lateral displacement, significant additional systematic error can be introduced into point-diffraction wavefront measurement result, and it cannot be removed with traditional calibration method. A high precision calibration method of structure error for point-diffraction wavefront interferometric measurement based on three-dimensional coordinate reconstruction and symmetric displacement compensation is proposed to calibrate the systematic error introduced by high numerical aperture and large lateral displacement in the measurement of point-diffraction spherical wavefront with non-lens imaging. Firstly, three-dimensional reconstruction method is used to pre-calibrate the symmetric error. Then, because the error introduced by point source lateral displacement in interferometric measurement is symmetric, the symmetric lateral displacement compensation is applied to further correct the residual structure error due to three-dimensional coordinate reconstruction error. Both the numerical simulation and experimental measurements are carried out to verify the feasibility of the proposed calibration method. According to the analyzing results, the calibration method can reach the correction precision better than λ/10000. The proposed calibration method is of great significance for the application of high precision calibration of structure error introduced by non-lens imaging interferometric measurement and high-accuracy measurement calibration of point-diffraction spherical wavefront..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 812007 (2016)
Lasers and Laser Optics
Molecular Dynamics Simulation of Femtosecond Laser irradiating Gold Foils
Yan Yan, and Li Ling
The heat transfer process of gold foils irradiated by a femtosecond laser pulse is simulated and studied by the molecular dynamics method combined with the two-temperature model. A local order parameter is adopted to distinguish the solid and liquid phase atoms and the changing laws of the location and temperature of tThe heat transfer process of gold foils irradiated by a femtosecond laser pulse is simulated and studied by the molecular dynamics method combined with the two-temperature model. A local order parameter is adopted to distinguish the solid and liquid phase atoms and the changing laws of the location and temperature of the solid-liquid interface versus time are obtained. On this basis, the effect of laser energy flux density on the melting process is investigated. It is shown that, with the absorption and transfer of laser energy, the lattice arrangement of Au atoms changes gradually from a regular and face-centered-cubic structure into an irregular and loosely arranged one. As time goes by, the solid-liquid interface gradually moves towards the bottom of the gold foil, and the foil volume also expands gradually. When the laser energy flux density is low, the gold foil does not melt completely and the melting is delayed. In contrast, the higher the laser energy flux density is, the melting occurs earlier and more rapidly, the melting depth is larger, and the interfacial temperature is higher..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 814001 (2016)
Acquisition and Denoising Algorithm of Laser Point Cloud Oriented to Robot Polishing
Deng Wenjun, Ye Jingyang, and Zhang Tie
For the quality of robot polishing process, the laser scanning technology is applied to the measurement and assessment of the shaping error and the clamping error of robot clamping workpiece, including the acquisition and denoising process of point cloud data. A stripe type laser scanner in uniform linear motion is useFor the quality of robot polishing process, the laser scanning technology is applied to the measurement and assessment of the shaping error and the clamping error of robot clamping workpiece, including the acquisition and denoising process of point cloud data. A stripe type laser scanner in uniform linear motion is used to scan a part clamped by robot. The approximate grid point cloud is obtained by adjusting the measurement and motion parameters. In order to remove the large scale noise in point cloud, the local mean K-nearest-neighbor mean filter (LMKMF) based on the K nearest neighbor mean filter(KNNMF) is proposed as local filter of partial large scale data point in advance. Relevant mathematical model is established. Peak signal-to-noise ratio is used as evaluation standard, and the actual measurement point cloud samples are used as the denoising test object. Results show that compared with the KNNMF, the denoising ability of the algorithm combining LMKMF with KNNMF has an improvement of 53.78% under the noise density of 30%, which proves that the proposed algorithm has greater ability of denoising and detail preserving when the noise density is high..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 814002 (2016)
Effect of Laser Shock Processing on Property and Microstructure of AM50 Magnesium Alloy
Liu Bo, Luo Kaiyu, Wu Liujun, and Lu Jinzhong
The method of laser shock processing (LSP) is used to investigate the effect of LSP on the grain structure, micro-hardness, and residual stress of the AM50 magnesium cast alloy along its depth direction. Results indicate that the micro-hardness and residual compressive stress of the alloy surface both have significant The method of laser shock processing (LSP) is used to investigate the effect of LSP on the grain structure, micro-hardness, and residual stress of the AM50 magnesium cast alloy along its depth direction. Results indicate that the micro-hardness and residual compressive stress of the alloy surface both have significant improvement after single LSP. On the LSP layer where original coarse grains are refined obviously, the surface micro-hardness value is increased by 19%, and the residual compressive stress is up to -225 MPa. Besides, the depths of the micro-hardness-improved area, grain-refined layer, and residual compressive stress layer are obviously increased. When the impact times is increased to two, the micro-hardness, grain size, and residual compressive stress are further improved..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 814003 (2016)
Probe Laser Power Stabilization for Integrated Sphere Cold Atom Clock
Li Lin, Liu Peng, Ji Jingwei, Cheng Huadong, Liu Liang, and Wang Yuzhu
A laser power stabilization system for the μW probe laser is developed. Power stabilization is realized by automatically adjusting diffraction efficiency of the acousto-optic modulator. The relative intensity noise of the probe laser is effectively suppressed to the shot noise limit, and the long-term stability is bettA laser power stabilization system for the μW probe laser is developed. Power stabilization is realized by automatically adjusting diffraction efficiency of the acousto-optic modulator. The relative intensity noise of the probe laser is effectively suppressed to the shot noise limit, and the long-term stability is better than 2×10-5 (1000 s). The loop function equation of the power stabilization system is deduced, and the suppression effect of the loop on the relative intensity noise is analyzed. The stabilized laser is applied to detecting the clock transition of the integrating sphere cold atom clock, and its contribution to the frequency stability is less than 1×10-13τ-1/2(τ is the samping time). The frequency stability of the clock is improved to better than 5×10-13τ-1/2..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 814004 (2016)
Machine Vision
Research on Underwater Stereo Matching Method Based on Color Segmentation
Zhang Qiang, Lu Shiqiang, Li Haibin, Li Yaqian, and Zhang Wenming
In term of underwater the epipolar constraint no longer meet binocular image matching, and the scale-invariant feature transform (SIFT) algorithm can only achieve sparse matching, the underwater stereo matching algorithm based on color segmentation is proposed. The calibration parameters of binocular camera are obtaineIn term of underwater the epipolar constraint no longer meet binocular image matching, and the scale-invariant feature transform (SIFT) algorithm can only achieve sparse matching, the underwater stereo matching algorithm based on color segmentation is proposed. The calibration parameters of binocular camera are obtained as well as reference image and image to be matched. Corresponding curve expression of the feature points of reference image on image to be matched is derived and the reference image is segmented by mean shift algorithm. The sum of absolute differences algorithm is used to match two images after assigning different weights to the pixels within the window based on the results of image segmentation and searching for the corresponding point in the curve, which can improve the matching accuracy. Experimental results show that the proposed algorithm is superior to feature matching SIFT algorithm, and the matching accuracy is improved. The area matching algorithm is successfully applied to underwater image dense matching..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 815001 (2016)
Outdoor Illumination Shadow Detection Based on Orthogonal Decomposition
Duan Zhigang, Qu Liangqiong, Tian Jiandong, and Tang Yandong
For detecting the shadow in outdoor illumination conditions rapidly and efficiently, a shadow detection approach based on pixel-wise orthogonal decomposition is proposed. Based on linear model in and out of shadows in an outdoor scene image, a linear equation set is built for each pixel value vector and orthogonally deFor detecting the shadow in outdoor illumination conditions rapidly and efficiently, a shadow detection approach based on pixel-wise orthogonal decomposition is proposed. Based on linear model in and out of shadows in an outdoor scene image, a linear equation set is built for each pixel value vector and orthogonally decomposed. By the decomposition of the linear equation solution space, a color illumination invariant image and an illumination variation image are obtained. The color illumination invariant image is classified into some regions using K-means algorithm, each region has the same spectral albedo. According to the classification results, a Gaussian mixture model with expectation maximization algorithm is proposed for modeling the illumination variation image, and then the shadow areas are extracted. The extracted shadow areas are optimized with morphological operator. The proposed method does not need complex learning process of feature operators and greatly reduces the time complexity of computation. It also does not require any prior knowledge and can be directly applied to the real-time scene processing..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 815002 (2016)
Materials
Synthesis and Characterization of Hexagonal Phase Wurtzite-Type ZnS Microspheres
Liu Xintong, Hu Xiaobo, and Xu Xiangang
The hexagonal phase wurtzite-type ZnS microspheres are synthesized by the hydrothermal method at relatively low reaction temperature (160 ℃), with glutathione (GSH) as the sulfur source, ZnCl2 as the zinc source, hexadecyl trimethylammonium bromide (CTAB) as the surfactant, and ethylenediamine as the reaction medium. TThe hexagonal phase wurtzite-type ZnS microspheres are synthesized by the hydrothermal method at relatively low reaction temperature (160 ℃), with glutathione (GSH) as the sulfur source, ZnCl2 as the zinc source, hexadecyl trimethylammonium bromide (CTAB) as the surfactant, and ethylenediamine as the reaction medium. The morphologies of microspheres are observed by scanning electron microscope, and their phase structures are analyzed by X-ray diffraction. In addition, the optical properties of samples synthesized under different conditions are characterized by fluorescence spectrometer and ultraviolet spectrophotometer. The experimental results show that CTAB can promote the formation of hollow spheres. The monodispersed hexagonal phase wurtzite-type ZnS microspheres at micrometer scale, which are composed of nanoparticles, can be obtained at relatively low reaction temperature when CTAB is used as the porogens. The ZnS hollow microspheres with different shell thicknesses can be synthesized by changing the reaction parameters. The test results show that the fluorescence intensity of hollow microspheres is higher than that of solid microspheres..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 816001 (2016)
Continuous Liquid Interface Production 3D Printing Technology and Its Application in Fabrication of Architecture Models
Lin Xuancheng, and Liu Huagang
In this paper, a technique to realize continuous liquid interface production 3D printing is presented by taking advantage of a new excellent gas permeable film, and is also demonstrated experimentally. The continuous liquid interface production 3D printer is constructed in a bottom-up schematic. A transparent and permeIn this paper, a technique to realize continuous liquid interface production 3D printing is presented by taking advantage of a new excellent gas permeable film, and is also demonstrated experimentally. The continuous liquid interface production 3D printer is constructed in a bottom-up schematic. A transparent and permeable film is introduced and placed between a light source and a 3D printing platform. In the process of printing, oxygen is injected into the printer and it permeates to the surface of photo-polymerizing layer through the permeable film. As a result of oxygen inhibition, an uncured liquid resin layer is generated between the permeable film and the lower surface of photo-polymerizing layer. Thanks to this uncured layer, the printing platform can be moved up continuously without interruption, achieving a high-speed continuous photo-polymerizing 3D printer with the maximum speed up to 650 mm/h in the longitudinal direction. Since the continuous liquid interface production 3D printer has various advantages such as high accuracy and efficiency, it is applied to fabricating architecture models for the experiments of wind tunnel test..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 816002 (2016)
Microscopy
Field of View-Extended Light Sheet Microscope Based on Wavefront Phase Modulation
Xu Hao, Zhang Yunhai, Zhang Xin, and Huang Wei
In order to extend the field of view (FOV) of the light sheet microscopy system, wavefront phase modulation and digital image tiling are proposed. The intensity distribution of the light sheet at the focal plane of the objective lens after wavefront phase modulation is numerically simulated. A light sheet microscopy syIn order to extend the field of view (FOV) of the light sheet microscopy system, wavefront phase modulation and digital image tiling are proposed. The intensity distribution of the light sheet at the focal plane of the objective lens after wavefront phase modulation is numerically simulated. A light sheet microscopy system is built to carry out the imaging experiments for fluorescent particles and flower pollen. The light sheet illuminates different sample positions by beam defocusing to obtain different images, which are tiled to get the FOV-extended image. FOV is extended to 3 times (about 31.93 μm) of the original field with wavelength of 488 nm and numerical aperture of 0.3 while the thickness of light sheet retains 0.81 μm. The experiment and simulation results suggest that FOV of the system can be extended by wavefront phase modulation and digital image tiling with tomographic ability not sacrificed..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 818001 (2016)
Theory and Systematic Design of Rheinberg Illumination Microscopy Based on Programmable LCD
Lin Fei, Zhang Wenwen, Fan Yao, Zuo Chao, and Chen Qian
Rheinberg illumination is an optical staining technique for microscopic imaging. The light passing through special filters provides chromatism between the specimen and background, which improves the contrast of colorless and transparent samples effectively. Rheinberg illumination microscopy based on programmable liquidRheinberg illumination is an optical staining technique for microscopic imaging. The light passing through special filters provides chromatism between the specimen and background, which improves the contrast of colorless and transparent samples effectively. Rheinberg illumination microscopy based on programmable liquid crystal display (LCD) replaces the condenser diaphragm of conventional microscope with low-cost thin film transistor liquid crystal display. By displaying different patterns, numerous microscopy imaging modalities, such as bright field, dark field, phase contrast, oblique illumination and Rheinberg illuminations can be realized. Furthermore, because it is easy to modulate both the color and the intensity of the LCD panel, the system derives completely new methods for optical staining, such as iridescent dark-field and iridescent phase-contrast imaging. The versatility and effectiveness of the system are demonstrated by microexamination of several transparent colorless specimens, such as unstained lung cancer cells, textile fibers, and slice of mouse kidney..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 818002 (2016)
Nonlinear Optics
Characteristics of Nonlinear Spectrum in Quartz Single Mode Fiber
Zhang Peng, and Tian Chunlin
An experiment system is set up for studying the characteristics of nonlinear spectrum in quartz single mode fiber. The electro-optical Q-switched pulsed Nd3+∶YAG solid laser, frequency-doubling by potassium titanium oxide phosphate (KTP) crystal, with output pulse width of 10 ns, the maximum peak power of 50 MW, and waAn experiment system is set up for studying the characteristics of nonlinear spectrum in quartz single mode fiber. The electro-optical Q-switched pulsed Nd3+∶YAG solid laser, frequency-doubling by potassium titanium oxide phosphate (KTP) crystal, with output pulse width of 10 ns, the maximum peak power of 50 MW, and wavelength of 531.81 nm±0.26 nm, is used to pump the quartz single mode fibers with lengths of 250 m and 500 m. Based on the principle of Malus law, a polarizing plate is used to adjust the output power of the pumping source. Under the stable operation condition, multi stage nonlinear spectra of 250 m and 500 m quartz single mode fibers in the visible region are obtained, while the output powers of pumping sources are 220.6 kW and 170 kW. Based on the principle of the third-order nonlinear effects in quartz single mode fiber, the characteristics of the nonlinear spectra obtained in the experiment are analyzed. Both the theoretical analysis and experimental results indicate that the longer the length of quartz single mode fiber, the larger the relative intensity of nonlinear spectrum and the coupling gain coefficient, and the smaller the energy threshold; while the shorter the length of quartz single mode fiber, the easier the broadening of nonlinear spectra and the generation of scattering additional peak..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 819001 (2016)
Optics in Computing
Research of Satellite Shape Inversion Matching Algorithm Based on Photometric Characteristic
Du Xiaoping, Liu Hao, Chen Hang, Gou Ruixin, and Du Mingjiang
According to the characteristic of the photometric curve, the curve matching algorithm in spectral domain is applied to the field of photometry and the demand of satellite shape inversion matching algorithm based on the photometric curve characteristic is resolved. The main principle of inversion method is introduced, According to the characteristic of the photometric curve, the curve matching algorithm in spectral domain is applied to the field of photometry and the demand of satellite shape inversion matching algorithm based on the photometric curve characteristic is resolved. The main principle of inversion method is introduced, the spectral angle match-spectral information divergence (SAM-SID) is designed through SAM and SID, and the threshold is confirmed, making the success rate better than 93%. Finally, the applicability and robustness of the algorithm is tested by the measured data of Xinglong Station. Experimental results show that the cylinder satellite inversion data, which can not be matched by SAM and SID algorithms, can be matched by the SAM-SID algorithm. The SAM-SID algorithm is applicable to the shape inversion of the cylinder, cube and sphere satellites. Compared with SAM and SID algorithms, the results of SAM-SID algorithm are more intuitive, and the applicability and robustness are much stronger..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 820001 (2016)
Physical Optics
Phase Singularities of Anomalous Hollow Beams Through an Astigmatic Lens
Tang Bihua, Zheng Shangbin, He Bing, Zhang Yong, Luo Yamei, and Gao Zenghui
The phase singularity in optical field is an important subject in singular optics. Based on the generalized Huygens-Fresnel diffraction integral formula, the field distribution expressions and the phase singularity distribution expressions for anomalous hollow beams through an astigmatic lens are deduced, and used to sThe phase singularity in optical field is an important subject in singular optics. Based on the generalized Huygens-Fresnel diffraction integral formula, the field distribution expressions and the phase singularity distribution expressions for anomalous hollow beams through an astigmatic lens are deduced, and used to study the phase singularities at the geometrical focal plane emphatically. The phase singularities may appear at the geometrical focal plane when the anomalous hollow beams pass through an astigmatic lens, and are dependent on the astigmatic coefficient and waist width. Under certain conditions, the ellipse or circular edge dislocations, optical vortices will appear at the geometrical focal plane. By changing the astigmatic coefficient or waist width, the ellipse or circular edge dislocations will vary, and the optical vortices will move, annihilate and appear..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 826001 (2016)
Temperature Characteristics of Optical Calcite Crystals
Wu Fuquan, Wu Wendi, Su Fufang, and Shi Meng
Through the coefficient of thermal expansion tensor, the formula of the omnidirectional thermal expansion coefficient of the optic calcite crystal (OCC) is deduced, and the zero-expansion direction of the OCC is determined. The expression of the omnidirectional birefringence versus temperature is derived, and the relatThrough the coefficient of thermal expansion tensor, the formula of the omnidirectional thermal expansion coefficient of the optic calcite crystal (OCC) is deduced, and the zero-expansion direction of the OCC is determined. The expression of the omnidirectional birefringence versus temperature is derived, and the relationship between the omnidirectional optical path difference and temperature is also provided. These results show that the zero-expansion of the OCC occurs at the azimuth angle of 65.35° or 114.65°. The effect of temperature on the optical path difference is subject to the azimuth angle and along the direction perpendicular to the optical axis, this effect is the most..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 826002 (2016)
Remote Sensing and Sensors
Research on the Signal-to-Noise Ratio in Sliding Spotlight Mode Down-Looking Synthetic Aperture Imaging Ladar
Zhang Ning, Lu Zhiyong, Sun Jianfeng, Zhou Yu, Luan Zhu, Li Gunagyuan, and Liu Liren
Under far field simulated conditions by using collimator with 15 m focal length, we present a sliding spotlight mode of the down-looking synthetic aperture imaging ladar (SAIL). Based a single point target echo collection equation, the signal-to-noise ratio in sliding spotlight mode is analysed. Theory and experiment cUnder far field simulated conditions by using collimator with 15 m focal length, we present a sliding spotlight mode of the down-looking synthetic aperture imaging ladar (SAIL). Based a single point target echo collection equation, the signal-to-noise ratio in sliding spotlight mode is analysed. Theory and experiment confirm that the sliding spotlight mode can improve signal-to-noise ratio when we can extend the effective acquisition time length..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 828001 (2016)
Target Detection Sparse Algorithm by Recursive Dictionary Updating and GPU Implementation
Zhao Chunhui, Yao Xifeng, and Zhang Lili
Sparse representation is a potential image representation method, which has been applied to target detection for images. The process to calculate sparse coefficients is complex when the orthogonal matching pursuit (OMP) algorithm is used, which cannot satisfy the requirement of rapid processing. An idea of recursive KaSparse representation is a potential image representation method, which has been applied to target detection for images. The process to calculate sparse coefficients is complex when the orthogonal matching pursuit (OMP) algorithm is used, which cannot satisfy the requirement of rapid processing. An idea of recursive Kalman filter is introduced, and a fast OMP (FastOMP) algorithm is proposed to calculate the sparse coefficient. The Hermitian lemma is used to update the current information from the last status. The FastOMP algorithm can avoid repeated calculation of higher-dimension matrix data. In order to further improve the efficiency of the algorithm, the parallel computation method is proposed based on GPU/CUDA (graphics processing unit/compute unified device architecture). The parallel computation capacity of GPU is utilized to accelerate the FastOMP algorithm. The experimental results show that the FastOMP algorithm saves the processing time notably and improves the detection accuracy compared to the traditional OMP algorithm..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 828002 (2016)
Scattering
Linear Depolarization Ratios Characteristics of Dust Aerosol Particles Model
Zhang Xiaolin
Linear depolarization ratios (LDR) characteristics of spheroid dust aerosol particles are studied based on discrete dipole approximation (DDA) for size parameters from 0.1 to 23 (corresponding to effective radius from 0.01 μm to 2 μm at wavelength of 0.55 μm). The effects of the particle asphericity degree on the LDRs Linear depolarization ratios (LDR) characteristics of spheroid dust aerosol particles are studied based on discrete dipole approximation (DDA) for size parameters from 0.1 to 23 (corresponding to effective radius from 0.01 μm to 2 μm at wavelength of 0.55 μm). The effects of the particle asphericity degree on the LDRs characteristics for both monodisperse and polydisperse dust aerosols are performed by comparing LDRs characteristics at different spheroid aspect ratios. For monodisperse particles, the LDRs of spheroid dust aerosol have different behaviors as a function of scattering angle in the Rayleigh and Mie domains. In the Rayleigh domain, the LDRs are small with a value of 1%, in the forward- and backward-scattering directions with the scattering angles of 0° and 180°. While the LDRs show maxima of 100%, at side-scattering angles of 90°. In the Mie domain, the LDRs have no obvious extremum distribution, and reveal significantly enhanced backscattering values. The degree of asphericity of monodisperse dust particles generally increases their LDRs in the Rayleigh domain but not in the Mie domain. However, for polydisperse particles, the degree of dust asphericity increases with the LDRs except in the side-scattering regions (80°~100°) where the LDRs reach maxima..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 829001 (2016)
Thin Films
Study and Fabrication of Polarized Waveguide with Broad Spectrum and Large Field of View in Augmented Reality System
Fu Xiuhua, Chen Zhihang, Zhang Jing, Zhang Yushuai, and Kou Yang
The effects of the two kinds of optical waveguide structures on the field of view and the size of waveguides are analyzed, and the waveguide structure and thin films are optimized. With the TFCalc software, the p polarized beam splitting films in the waveguide are designed. With the choice of H4 and MgF2 as the respectThe effects of the two kinds of optical waveguide structures on the field of view and the size of waveguides are analyzed, and the waveguide structure and thin films are optimized. With the TFCalc software, the p polarized beam splitting films in the waveguide are designed. With the choice of H4 and MgF2 as the respective high and low refractive index materials and with the combination of the Needle and Variable Metric methods, the film system is optimized. In the wave band of 450~600 nm, the average reflectivity of the p polarized beam splitting films is 30.1% at an incident angle of 25° and is less than 5% at angles of incidence from 50° to 80°. The above film fulfills the requirements for the firmness testing..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 831001 (2016)
X-Ray Optics
Projection Decomposition Algorithm for X-Ray Dual-Energy Computed Tomography Based on Isotransmission Line Fitting
Li Lei, Wang Linyuan, Cai Ailong, Han Yu, Yan Bin, and Bao Shanglian
Aiming at the nonlinear projection decomposition problem in the image reconstruction by dual-energy computed tomography (DECT), a fast projection decomposition algorithm based on isotransmission line fitting is proposed. A linearly approximated isotransmission line fitting model is established for high and low energy pAiming at the nonlinear projection decomposition problem in the image reconstruction by dual-energy computed tomography (DECT), a fast projection decomposition algorithm based on isotransmission line fitting is proposed. A linearly approximated isotransmission line fitting model is established for high and low energy projections. Based on the Taylor series expansion, the coarse-grain forward calculation and fine-grain reverse calculation are used to get the analytical solution with high accuracy, and the isotransmission line equations are generated. The nonlinear solution problem is transformed into the problem to solve intersections of high and low energy projection isotransmission lines, and thus the fast decomposition of dual energy projections is realized. The experimental results show that the proposed method avoids the nonlinear iteration and the projection matching, reduces noise fluctuation in projection decomposition, and improves the projection decomposition rate significantly. Compared to the projection matching method, the proposed method improves the decomposition rate by about two orders of magnitude..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 834001 (2016)
Multilayer Nested X-Ray Focusing Optical Device
Liu Duo, Qiang Pengfei, Li Linsen, Liu Zhe, Sheng Lizhi, Liu Yong′an, and Zhao Baosheng
Aiming at the demand on X-ray pulsar navigation and X-ray space communication, the multilayer nested X-ray focusing optical device is developed and tested. Theoretical design of focusing lenses is carried out according to the principle of grazing incidence, and key parameters of the focusing lenses are determined. The Aiming at the demand on X-ray pulsar navigation and X-ray space communication, the multilayer nested X-ray focusing optical device is developed and tested. Theoretical design of focusing lenses is carried out according to the principle of grazing incidence, and key parameters of the focusing lenses are determined. The materials of focusing lenses and the preparation technologies such as the coating process are discussed. The performance parameters of the focusing lenses are tested respectively under the conditions of visible light and X-ray. The results show that the spot diameter of visible light is 14 mm, the spot diameter of X-ray is 20 mm, and the focusing efficiency is 30.2%. The effective area is 2400 mm2 in a 10 m vacuum pipe when the photon energy is 1.5 keV..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 834002 (2016)
Synchrotron Radiation X-Ray Stereo Imaging Based on Capillary Beam Splitting
Wang Feixiang, Deng Biao, Wang Yudan, Ren Yuqi, Sun Tianxi, and Xiao Tiqiao
A stereo imaging system based on synchrotron radiation X-rays is built in the BL13W beam line of the Shanghai Synchrotron Radiation Facility. The system uses two bending capillary tubes to extract synchrotron radiation photons and divides them into two intersected beams. The experimental sample is placed at the interseA stereo imaging system based on synchrotron radiation X-rays is built in the BL13W beam line of the Shanghai Synchrotron Radiation Facility. The system uses two bending capillary tubes to extract synchrotron radiation photons and divides them into two intersected beams. The experimental sample is placed at the intersection of two X-ray beams and two projections of the sample are recorded simultaneously by a detector placed close to the sample. The depth information of each element of the sample is calculated by parallax equations and relevant algorithms, and the pseudo three-dimensional image of the sample is produced. Compared with X-ray computed tomography, the proposed method improves the time resolution notably, which is even close to the duration of a single exposure. It can be used for real-time imaging and reduce the radiation dose of the sample. A numerical simulation is performed with the projection of blood capillary in the mouse liver and achieves an ideal result. A spiral wire model is then taken as a sample to conduct stereo imaging in the experimental platform. The preliminary experimental result demonstrates that the stereo information of the spiral wire can be recognized clearly..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 36, Issue 8, 834004 (2016)
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