Contents
2011
Volume: 31 Issue 11
49 Article(s)
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Atmospheric Optics and Oceanic Optics
Numerical Simulation of Wander of Ranging Laser Beam
Li Rongwang, Chang Xiang, and Xiong Yaoheng
For the application of long-distance laser ranging, such as geosynchronous satellite laser ranging and lunar laser ranging, the uplink beam is simulated by using split-step numerical method (or fast-Fourier-transform beam propagation method). Using unequal interval phase screen distribution according to the profile of For the application of long-distance laser ranging, such as geosynchronous satellite laser ranging and lunar laser ranging, the uplink beam is simulated by using split-step numerical method (or fast-Fourier-transform beam propagation method). Using unequal interval phase screen distribution according to the profile of atmosphere structural constant, the average propagation intensity is in good agreement with theoretical value. Based on this, the effect of beam wander is analyzed, which is the main reason of intensity decrease on axis. So after the removal of beam wander, without pointing error, the intensity on axis increases roughly. This improves the probability of detecting echo of laser ranging. It is found that there is a proper initial beam waist to minimize the on-axis scintillation index. The simulation results are very useful to the design of tip-tilt correction system..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1101001 (2011)
Technology of Atmospheric Refraction Compensation in Starlight Observation
Wang Haiyong, Lin Haoyu, and Zhou Wenrui
In order to eliminate the influence of atmospheric refraction when observing starlight in the atmosphere and enhance the accuracy of carrier attitude fixing, a compensation algorithm of the refraction is proposed. Firstly, the attitude transfer matrices involved in the whole process and complete the corresponding vectoIn order to eliminate the influence of atmospheric refraction when observing starlight in the atmosphere and enhance the accuracy of carrier attitude fixing, a compensation algorithm of the refraction is proposed. Firstly, the attitude transfer matrices involved in the whole process and complete the corresponding vector coordinate mapping transform are given. Then in the star sensor coordinate system, the visual zenith angle according to the interior product of two vectors is calculated. Lastly, with geometric formula, the system of equation taking the estimated position of the real starlight vector projection point to be the unknown variables is listed, which can be used as the refraction compensation algorithm model when the star sensor is in any attitude. Under the condition of no error, the simulation to model validity is carried out, and the magnitude of position estimation precision is 10-6 pixel, showing the validity of the proposed algorithm. The simulation is done again with different orders of magnitude gyroscope drift errors, and the effect on the estimation precision of refraction compensation model from the given gyroscope drift error is little. The simulation results show that under the premise that there are certain attitude errors of the strapdown carrier, the refraction compensation model is also applicable. The compensated star coordinates are used for starlight attitude determination, and further to compensate the gyroscope drift error..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1101002 (2011)
Correction of the Influence of Multiple Scattering on NO2 Emission Flux during the Pollutants Source Measurement by Mobile Differential Optical Absorption Spectroscopy
Wu Fengcheng, Xie Pinhua, Li Ang, Si Fuqi, Wang Yang, and Liu Wenqing
A large calculation error of pollutant emission flux occurs due to the influence of multiple scattering when we utilize the mobile differential optical absorption spectroscopy (DOAS), which is based on the passive differential optical absorption spectroscopy, to measure the pollutant source. The concentration of NO2 thA large calculation error of pollutant emission flux occurs due to the influence of multiple scattering when we utilize the mobile differential optical absorption spectroscopy (DOAS), which is based on the passive differential optical absorption spectroscopy, to measure the pollutant source. The concentration of NO2 that lies in the total layer increases significantly because of multi scattering in the lower atmospheric cloud. This results in large computing error of NO2 emission flux. To solve this problem, a new method is proposed. The information of O4 and SO2 vertical column density is employed during the measurement and then used to adjust the enhancement of NO2 due to multi scattering in the process of calculating flux. The experimental data from a certain Shanghai industrial district on Oct. 9th, 2010 is retrieved using this method. The flux value is 1.49 t/h and 0.5 t/h before and after correction, respectively. The results indicate that this method could effectively eliminate the influence of column density rise caused by multi scattering during the measurement. This novel method could facilitate the application of mobile DOAS on accurate measurement of emission flux from pollutant source..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1101003 (2011)
Analysis of Inherent Optical Properties in the Occurrence and Declination of a Red Tide
Hao Yanling, Cao Wenxi, Ma Yi, Cui Tingwei, and Zhang Jie
During optical buoy experiments in the Pearl River (Zhujiang) mouth regions, time series of bio-optical data of Chaetoceros socialis red tide is obtained. By using the data, variation of ocean optical properties (absorption and backscattering properties) in the occurrence and declination of red tide is analyzed. ResultDuring optical buoy experiments in the Pearl River (Zhujiang) mouth regions, time series of bio-optical data of Chaetoceros socialis red tide is obtained. By using the data, variation of ocean optical properties (absorption and backscattering properties) in the occurrence and declination of red tide is analyzed. Results show that the absorption of various components such as phytoplankton pigments, detritus and colored dissolved organic matter changes dramatically, the absorption of various components increases and reaches maximum values in red tide outbreak period, then the absorption of various components decreases and reaches minimum values in red tide declination period. Compared with red tide development and declination period, contribution of phytoplankton pigment increases by 16%, and that of colored dissolved organic matter decreases by 18%, but that of detritus has little changes for red tide out break period; backscattering coefficient increases in red tide outbreak period, and range of diurnal variation is large, backscattering coefficient is small in red tide development and declination period, and the value is minimum in red tide declination period. Correlation coefficient between backscattering coefficient and chlorophyll-a concentration is larger than that between backscattering coefficient and suspended matter concentration. Although concentration of particulate organic matter in the total suspended particulate matter dominates, correlation coefficient between the backscattering coefficient and particulate inorganic matter concentration is larger..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1101004 (2011)
Study on the Relation of Ocean Atmospheric Aerosol Optical Model Parameters
Wang Jiacheng, Qiao Yanli, Yang Shizhi, and Zhao Qiang
Aerosol optical model parameters are important for aerosol remote sensing and climate forcing study. The negative correlation between the standard deviation and number median radius has beam established based on the ocean Aerosol Robotic Network (AERONET) data worldwide empirical relation is proposed. Moderate-resolutiAerosol optical model parameters are important for aerosol remote sensing and climate forcing study. The negative correlation between the standard deviation and number median radius has beam established based on the ocean Aerosol Robotic Network (AERONET) data worldwide empirical relation is proposed. Moderate-resolution imaging spectroradiometer (MODIS) ocean aerosol models are assessed by using this relation, and some shortcomings have been discussed..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1101005 (2011)
Forward Scattering Müller Matrix Characteristics of Ship Wakes
Yang Yu, and Zhang Jiansheng
Using characteristic distribution pattern of forward-scattering Müller matrix belonging to ship wakes (FSMMBSW), relations among matrix element, bubble number density and bubble radius are discussed based on Mie scattering theory by use of single-scattering model, in which calculated results show that, m2 and m4 eUsing characteristic distribution pattern of forward-scattering Müller matrix belonging to ship wakes (FSMMBSW), relations among matrix element, bubble number density and bubble radius are discussed based on Mie scattering theory by use of single-scattering model, in which calculated results show that, m2 and m4 elements have relatively strong shocks for a single bubble with scattering angle ranging from 0 to 90\O, and amplitudes of these shocks increase with rising radius. M11 and M44 of FSMMBSW for bubbles have no clear change with different azimuths. Distributions of elements changing with different azimuths are in accordance with the law of sine shocks, and elements of FSMMBSW decay with polar radius exponentially; M11, M44 and their amplitudes change with different azimuths, increase with radius rising. Maximums of the elements occur at bubble number density of 108 m-3. Characteristics between elements are opposite with different number densities around sides. Besides intensity, information of phase reversal with bubble radius as well as number density changing is reasonably contained in M12 and M13..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1101006 (2011)
Retrieval of Atmospheric NO2 Vertical Profile from Multi-Axis Differential Optical Absorption Spectroscopy
Zhou Haijin, Liu Wenqing, Si Fuqi, Xie Pinhua, Xu Jin, and Dou Ke
Measurement of trace-gas vertical profile is very important for research of atmospheric pollution. The multi-axis differential optical absorption spectroscopy (MAX-DOAS) is used on trace-gas profile monitoring. Combing with radiative transfer models, trace gas vertical profile is derived from slant column densities of Measurement of trace-gas vertical profile is very important for research of atmospheric pollution. The multi-axis differential optical absorption spectroscopy (MAX-DOAS) is used on trace-gas profile monitoring. Combing with radiative transfer models, trace gas vertical profile is derived from slant column densities of several elevation angles of MAX-DOAS with optimal estimation method. The parameters setup of retrieval algorithm and the characterization of the retrieval has been described in detail. MAX-DOAS is used to monitor NO2 profile of Hefei area. The measurement result is validated with long-path differential optical absorption spectroscopy (LP-DOAS), and the correlation coefficient is 0.80. This technique provides a simple and convenient method three-dimensional observation for air pollution..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1101007 (2011)
Detectors
Dependence of the Quantum Well Infrared Photodetector Absorption Wavelength on Uniaxial Stress
Zhang Jiaxin, Xu Liping, Wen Tingdun, and Wang Zhongbin
The dependence of the bandgaps of strained superlattice and quantum wells on uniaxial stress is studied, by using of the method of electron reflection and interference. The quantitative relation between the stress and the energy levels of GaAs-AlGaAs superlattice and quantum wells is obtained. Furthermore, the dependenThe dependence of the bandgaps of strained superlattice and quantum wells on uniaxial stress is studied, by using of the method of electron reflection and interference. The quantitative relation between the stress and the energy levels of GaAs-AlGaAs superlattice and quantum wells is obtained. Furthermore, the dependence of the energy levels in conduction band on uniaxial stress is calculated for GaAs-AlGaAs-GaAs. Then the dependence of absorption wavelength on the uniaxial stress is given in a quantum well infrared photodetector (QWIP). The results show that the absorption peak moves nearly 1.1 μm when the stress is increased to 1.3 GPa and the change with stress is basically linear. The peak of absorption wavelength can be tuned from 5.57 μm to 4.46 μm continuously in QWIP..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1104001 (2011)
Experimental Investigation for Relation between Beam Splitter Coefficient and Signal-to-Noise Ratio of 2 μm Balanced Coherent System
Wang Chunhui, Gao Long, Pang Yajun, Liu Lei, Li Yanchao, and Qu Yang
Mathematical model of signal-to-noise ratio (SNR) for balanced coherent system is proposed and SNR of balanced coherent system is simulated analytically with that of conventional coherent system. Simulation results show that SNR of balanced coherent system is symmetrical with 0.5 beam splitter coefficient with the matcMathematical model of signal-to-noise ratio (SNR) for balanced coherent system is proposed and SNR of balanced coherent system is simulated analytically with that of conventional coherent system. Simulation results show that SNR of balanced coherent system is symmetrical with 0.5 beam splitter coefficient with the matched detectors. Whereas, the optimum beam splitter coefficient for maximum of SNR is deviated from 0.5 with the unmatched detectors. Experimental configuration for 2 μm balanced coherent detection is demonstrated in which the SNR is more than 19 dB higher than that of conventional coherent system with 0.5 beam-splitter coefficient and the range for SNR of balanced coherent detection near to saturation is more than 0.2 wider than that of conventional coherent system under the same optical power condition..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1104002 (2011)
Fiber Optics and Optical Communications
Design and Optimization of Chromatic Dispersion Compensation Block in Digital Coherent Optical Receiver
Xu Xia, Xi Lixia, Zhang Xiaoguang, and Tong Cheng
In digital coherent receivers of high-speed optical fiber communication, the structure and performance of chromatic dispersion compensation block determines its practical value directly. A finite impulse response (FIR) filter with simpler even-symmetric structure is designed, and the effect of different lengths of FIR In digital coherent receivers of high-speed optical fiber communication, the structure and performance of chromatic dispersion compensation block determines its practical value directly. A finite impulse response (FIR) filter with simpler even-symmetric structure is designed, and the effect of different lengths of FIR filter on chromatic dispersion compensation performance is discussed through numerical simulation. The results show that the length of FIR filter can be reduced to 65 percent of its theoretical maximum with only 1 dB penalty of optical signal-to-noise ratio (OSNR) at the receiver, in which the implementation complexity is decreased at a large scale while chromatic dispersion impairment can be compensated effectively..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1106001 (2011)
Design of All-Fiber Asymmetric Interleaver with 2×2 and 3×3 Fiber Couplers
Lu Huaiwei, Wei Yun, Wu Kaijun, Zhang Baoge, and Luo Guanwei
An all-fiber asymmetric optical interleaver of cascaded Mach-Zehnder interferometer using a 2×2 and two 3×3 fiber couplers is developed. Influences on its transmission characteristics by such factors as splitting ratio of the directional fiber couplers and the physical length differences of the interferometerAn all-fiber asymmetric optical interleaver of cascaded Mach-Zehnder interferometer using a 2×2 and two 3×3 fiber couplers is developed. Influences on its transmission characteristics by such factors as splitting ratio of the directional fiber couplers and the physical length differences of the interferometer arms are numerically analyzed in detail. One set of optimized data is validated in the experimental result. The results of numerical simulation and experiments show that all-fiber optical interleaver with -3 dB passband in odd channels and even channels can be obtained for transmission speed of 40 Gb/s and 10 Gb/s, respectively. Compared with all-fiber asymmetric optical interleaver of cascaded Mach-Zehnder interferometer using three 2×2 fiber couplers, the most advantage of the present method is that the coupling ratio of couplers can be controlled in the fabricating process accurately. Finally, a novel structure of interleaver is fabricated using fused biconical taper technics in experiment. The experimental results agree with the analytical ones well..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1106002 (2011)
Research on Theoretical Improvement of Dynamic Allan Variance and Its Application
Zhang Na, and Li Xuyou
The dynamic Allan variance (DAVAR) is an effective method for analyzing non-stationary signal. However, it has defects such as power leakage and single quantification in noise identification. Therefore, window function combination method and two-dimensional expression of noise value are introduced for their improvementThe dynamic Allan variance (DAVAR) is an effective method for analyzing non-stationary signal. However, it has defects such as power leakage and single quantification in noise identification. Therefore, window function combination method and two-dimensional expression of noise value are introduced for their improvements. They are used for analysis and quantitative measurement of various noise terms in the fiber optic gyroscope dynamic error. Based on the dynamic error resolution of fiber optic gyroscope, rectangular window and Hanning window are applied to analyze low and intermediate frequency noise and high-frequency noise, respectively. According to the principle of DAVAR, the noise variation laws with the numbers of sampling point are obtained, namely, the two-dimensional expression of noise value. The experimental results indicate that window function combination method satisfies the identification requirements of noise in different frequency ranges and reduces power leakage; moreover, the changing characteristics of every noise item in the dynamic error are accurately reflected by the two-dimensional expression of noise value..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1106003 (2011)
Holography
Reconstruction of Digital Inline Hologram with Compressed Sensing
Wu Yingchun, Wu Xuecheng, Wang Zhihua, Chen Linghong, Zhou Hao, and Cen Kefa
Numerical reconstruction is a key procedure of digital holography. Classical reconstruciton algorithms are characterized by the twin images, superimposition of in-focus and out-of-focus object, and so on. Application of the new compressive sensing theory to sparsity reconstruction of digital inline holography is investNumerical reconstruction is a key procedure of digital holography. Classical reconstruciton algorithms are characterized by the twin images, superimposition of in-focus and out-of-focus object, and so on. Application of the new compressive sensing theory to sparsity reconstruction of digital inline holography is investigated. Based on the linear operator of diffraction model, the algorithm for the reconstruction of digital inline holography using compressive sensing is derived. Holograms of particle field from both simulation and micro digital inline holography are reconstructed, and the reconstructed particle field with compressive sensing algorithm is compared with that of convolution algorithm. Results show that the compressive sensing algorithm can improve the quality of reconstructed planes, and can reconstruct the particle field with good accurary with even 25% of the hologram. It also shows potential in focusing performance and robustness to noise..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1109001 (2011)
Eliminaton of the Influence of Zero-Order Diffraction Using Highpass Filter in Wavefront Reconstruction
Zhang Yaping, Zhang Jianqiang, Xu Wei, Gui Jinbin, Lou Yuli, and Zhang Yong′an
Based on the spectrum analysis of digital hologram illuminated with spherical wave in the course of object wavefront reconstruction with selectable magnification, the method of eliminating the influence of zero-order diffraction is proposed, which uses highpass filter before illuminating hologram with reconstruction waBased on the spectrum analysis of digital hologram illuminated with spherical wave in the course of object wavefront reconstruction with selectable magnification, the method of eliminating the influence of zero-order diffraction is proposed, which uses highpass filter before illuminating hologram with reconstruction wave. The theoretical simulation and experimental result of wavefront reconstruction are given from two aspects: scattering and undiffused light from object surface. The result shows that the interference of the reconstructed image can be eliminated effectively when scattering occurs on the surface. However, when the surface is a smooth plane, much stricter condition should be needed in order to get a completely reconstructed image..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1109002 (2011)
Imaging Systems
Computed Tomography Reconstruction Technology for Neutron Penumbral Imaging
Yu Bo, Huang Tianxuan, Chen Bolun, Su Ming, Jiang Wei, and Liu Shenye
The useful reconstruction technologies for neutron penumbral imaging are all linear method, and computed tomography (CT) is one of linear methods. The principle of the CT reconstruction for neutron penumbral imaging is introduced, and the detecting image with penumbral imaging, which is extracted and differentiated aloThe useful reconstruction technologies for neutron penumbral imaging are all linear method, and computed tomography (CT) is one of linear methods. The principle of the CT reconstruction for neutron penumbral imaging is introduced, and the detecting image with penumbral imaging, which is extracted and differentiated along radial direction, can be reconstructed by the CT method. The detecting imaging with different noises is decoded by convoluted backprojection method, and the advantages and disadvantages of the CT reconstruction are analyzed. According to the results, the source distribution can be reconstructed by the CT method, and the higher the signal-to-noise ratio of the detecting imaging is, the better reconstruction result is. The point spread function doesn′t needs to be fully simulated before decoding, and the results will not be interfered by the useless data, because the useful data can be automatically picked from the penumbral region, and the useless data will be deleted in the bright and dark regions..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1111001 (2011)
A Novel Phase Order Self-Encoding Technique for Phase Measuring Profilometry
Liu Yuankun, Su Xianyu, and Zhang Qican
The phase measuring profilometry using a novel phase order self-encoding technique is presented, which is to use the differential of the wrapped phase as the encoded information to identify all periods of the grating. The length of the encoded sequence is the same as the number of periods. There is only one code value The phase measuring profilometry using a novel phase order self-encoding technique is presented, which is to use the differential of the wrapped phase as the encoded information to identify all periods of the grating. The length of the encoded sequence is the same as the number of periods. There is only one code value in one period, which can be identified by the information of the differential and phase jumps. For each period, the information of its several neighboring periods will form a subsequence, which is unique and can be used to find the order of each period. The absolute phase can be got after getting the order. To revise the phase errors at some phase-jump areas, Hilbert transform is employed. By embedding the encoded information in the wrapped phase, there is no extra grating needing projecting, and there is also no classical phase unwrapping process. It is promising in measuring the surface profile of the spatially isolated objects..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1111002 (2011)
Performance Analysis of Fractional Fourier Transform Optical Imaging Based on Fractional Fourier-Domain Filtering
Zhang Jingjing, Jiang Yuesong, He Yuntao, Liu Li, and Wang Jing
Combining fractional Fourier-domain filtering with optical imaging, a two cascade fractional Fourier transform (FRFT) optical imaging system with filtering aperture is proposed, which is based on Lohmann I single-lens system. Firstly, the basic theory of the FRFT optical imaging combined with the fractional Fourier-domCombining fractional Fourier-domain filtering with optical imaging, a two cascade fractional Fourier transform (FRFT) optical imaging system with filtering aperture is proposed, which is based on Lohmann I single-lens system. Firstly, the basic theory of the FRFT optical imaging combined with the fractional Fourier-domain filtering is discussed according to the relation between FRFT and Fresnel diffraction as well as fractional additivity of FRFT. Then, imaging performance for distant objects is discussed in terms of different orders, the relative sizes of filtering aperture and pupil, based on the point spread function (PSF) and modulation transfer function (MTF). The results show that, compared with the traditional Fourier optical imaging, some FRFT optical imaging systems based on fractional Fourier-domain filtering have better imaging performance and higher resolution..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1111003 (2011)
Modulation Transfer Function Measurement Method of Electro-Optical Imaging System
Xu Baoshu, Shi Zelin, and Feng Bin
Modulation transfer function (MTF) is one of significant parameters for designing and evaluating an electro-optical imaging system. By proving the linear relation between an edge spread function and an inverse cumulative histogram of edge, an MTF measurement method based on statistical histogram is presented. SimulatioModulation transfer function (MTF) is one of significant parameters for designing and evaluating an electro-optical imaging system. By proving the linear relation between an edge spread function and an inverse cumulative histogram of edge, an MTF measurement method based on statistical histogram is presented. Simulation and experiment including optics and detectors are designed. Physical experimental platform including an integrating sphere, target, collimator, digital camera and other devices is developed. Taking the theoretical model and design parameters of electro-optical imaging system as a reference, the validity of our measurement method is verified by the simulation and experiment. Experimental results indicate that, comparing with the existing MTF measurement method, the proposed method can overcome the phase effects which is caused by under-sampling of imaging detector. It is more robust to angle of knife edge and noisy environment, and can measure response properties beyond the sampling frequency of an electro-optical imaging system..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1111004 (2011)
Instrumentation, Measurement and Metrology
Error Analysis and Correction during Measurement of Tube-Shaped Super-Smooth Mirrors Using Long Trace Profiler
Li Shun, and Gong Yan
To improve the accuracy of long trace profiler for measuring the surface profile of tube-shaped super-smooth mirrors, some common errors and correcting methods are studied and summed up. The errors caused by the tilt and decenter between the rotating axis of rotary table and the axis of tube-shaped mirror under test duTo improve the accuracy of long trace profiler for measuring the surface profile of tube-shaped super-smooth mirrors, some common errors and correcting methods are studied and summed up. The errors caused by the tilt and decenter between the rotating axis of rotary table and the axis of tube-shaped mirror under test during measurement will influence the result very much. These errors are in detail analyzed, and a correction method through data processing is presented. Then, a data processing code is programmed, and a numerical-simulation experiment is given to decide the properties of the code. Experimental results indicate that the code can remove the tilt and decenter errors between rotary table and mirror under test effectively, and improve the accuracy of tube-shaped mirror measurement using long trace profiler. When there is 5 μm decenter and 1′ tilt between the rotary table and mirror under test, using the code to restore the surface profile at the order of 50 nm, the restoration accuracy is root-mean-square (RMS) 2.8 nm and peak-to-valley (PV) 18.5 nm..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1112001 (2011)
Phase Retrieval for a Kind of Wavefront Sensor Based on Pupil Phase Diversity
Yang Huizhen, and Gong Chenglong
A kind of phase retrieval algorithm, which combines Zernike-mode decomposition with stochastic parallel gradient descent (SPGD), is raised to realize wavefront phase recovery based on pupil phase diversity (PPD). The performance of phase retrieval algorithm is analyzed through two different aberrated wavefronts. One isA kind of phase retrieval algorithm, which combines Zernike-mode decomposition with stochastic parallel gradient descent (SPGD), is raised to realize wavefront phase recovery based on pupil phase diversity (PPD). The performance of phase retrieval algorithm is analyzed through two different aberrated wavefronts. One is an initial shape of 32-element deformable mirror sampled by the interferometer; the other is generated through the method proposed by Roddier. Simulation results show that above two aberrated wavefronts can be restored successfully. For relatively small aberrations, satisfactory results are obtained only using the mode decomposition. When the aberrated wavefronts include many high frequency components, the algorithm only using the mode decomposition does not fit for this situation because of coupling among different orders. The results of the mode decomposition are used as the initial solution of SPGD algorithm, which searches the optimum solution. Simulation results under noise show the phase retrieval algorithm has strong anti-noise ability..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1112002 (2011)
Elimination of Nonlinear Error in Deformed Fringe Pattern by S-Transform Profilometry
Zhong Min, Chen Wenjing, and Jiang Mohua
S-Transform, a hybrid and extension of the short-time (or windowed) Fourier transform and the wavelet transform, is one of lossless and reversible time-frequency analysis methods, which is suitable to analyze non-stationary signals. It not only has advantages of linearity, multi-resolution and uniqueness of inverse, buS-Transform, a hybrid and extension of the short-time (or windowed) Fourier transform and the wavelet transform, is one of lossless and reversible time-frequency analysis methods, which is suitable to analyze non-stationary signals. It not only has advantages of linearity, multi-resolution and uniqueness of inverse, but also its inverse transform directly keeps in contact with the Fourier transform. In S-Transform, the harmonic wave is used as a basic element function, and the window function is a Gaussian function with the ability of both dilation and translation, which is controlled by a frequency parameter. Compared with the short-time (or windowed) Fourier transform, it has optimized the time-resolution and frequency resolution simultraneously. Compared with wavelet transform, it keeps in contact with the Fourier transform. S transform in the application of demodulation of fringe pattern with nonlinear parts has been deeply discussed, S-transform expression of the deformed fringe pattern considering by nonlinear effects is deduced and two ways, including S transform filtering method and S transform ridge method are proposed, which are used to eliminate the nonlinear error in three-dimensional optical measurement based on the structured light projection. Computer simulations and experiments have verified the proposed two methods. Compared with Fourier transform and wavelet transform, the proposed methods based on S transform have better reconstruction results..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1112003 (2011)
Phase Extraction Algorithms of Multi-Beam Interference Based on π/4 Phase-Shifting Averaging
Yuan Qun, Gao Zhishan, Li Jianxin, Zhou Yuxuan, and Chu Guang
The interference intensity is not strictly cosine distribution if multi-beam interference exists in Fizeau interferometer. Based on the formula of interference intensity in Fizeau interferometer, the conditions to make the interference intensity in Fizeau interferometer be approximated as the ideal formula of multi-beaThe interference intensity is not strictly cosine distribution if multi-beam interference exists in Fizeau interferometer. Based on the formula of interference intensity in Fizeau interferometer, the conditions to make the interference intensity in Fizeau interferometer be approximated as the ideal formula of multi-beam interference are brought. The calculated phase errors of 4-frame phase-shifting algorithms when using multi-beam interferograms are derived, and phase extraction algorithms of multi-beam interference based on π/4 phase-shifting averaging are proposed: two sequences of phase-shifting interferograms with π/4 interval are collected, and the two calculated phases obtained from the two sequences are averaged to suppress the error induced by multibeam interference. The calculated phase errors for test surfaces with different reflection coefficients are numerically simulated in the condition of random phase-shifting errors. A mirror with high reflection coefficient is tested by Fizeau interferometer, and 22 frames of interferograms are captured to calculate the wavefront map. The results indicate that ripple errors at 4 times the modulation frequency of fringes exist in the calculated phase when using routine phase-shifting algorithms, while the proposed π/4 phase-shifting averaging method based on the overlapping averaging 4-frame algorithm can efficiently suppress the phase error caused by multi-beam interference..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1112004 (2011)
Anti-Disturbance Phase-Shifting Interferometry Method Time-and-Frequency-Domain
Wang Ming, Hao Qun, Zhu Qiudong, and Hu Yao
Because interferometry is highly sensitive to disturbance such as vibration and air flow, a time-and-frequency domain (TFD) interferometry is proposed. A large number of continuous phase-shifting interferograms are captured. A distorted series of phase variety during fringe capturing is obtained through wide bandwidth Because interferometry is highly sensitive to disturbance such as vibration and air flow, a time-and-frequency domain (TFD) interferometry is proposed. A large number of continuous phase-shifting interferograms are captured. A distorted series of phase variety during fringe capturing is obtained through wide bandwidth filter to the spectrum of intensity series from a particular pixel, and then a linear statistic of it gives the measuring result of initial phase. With a large enough number of frames, the linear statistic efficiently reduces random noises to zero. And influences introduced by other non-random disturbances are astringed into a value which is independent of the index of pixels and therefore does not influence the shape of the whole wavefront. A simulation confirms the feasibility of the TFD method, and an experiment is carried out applying TFD method in a mechanical phase-shifting interferometric system fixed in a normal laboratory environment. The result prettily matches that from a FISBA interferometer, which verifies the anti-noise ability of TFD method..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1112005 (2011)
Theoretical Research on Lock-in Error Compensation for Mechanical Dithered Ring Laser Gyro
Fan Zhenfang, Luo Hui, Lu Guangfeng, and Hu Shaomin
The mechanical dither ring laser gyro (MDRLG) can achieve high accuracy. But the MDRLG must go across lock-in region twice every dither cycle, thus the information loss is inevitable. Random noise injection in the dither amplitude can only cancel the accumulation of lock-in error, but not the error itself. According toThe mechanical dither ring laser gyro (MDRLG) can achieve high accuracy. But the MDRLG must go across lock-in region twice every dither cycle, thus the information loss is inevitable. Random noise injection in the dither amplitude can only cancel the accumulation of lock-in error, but not the error itself. According to the lock-in equation, the side effect of lock-in phenomenon is interpreted in detail. Theoretical research on lock-in error compensation for MDRLG is carried out. Taking the constant acceleration approximation in lock-in region, the lock-in error representation is obtained. Numerical simulation results show that even in different input angle rates, the compensation is also very effective..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1112006 (2011)
Slant-Axis Digital Image Correlation Method Based on Photogrammetric Correction
Tang Zhengzong, Liang Jin, and Guo Cheng
A novel single-camera two-dimensional digital image correlation method based on photogrammetry correction is developed for the situation that the camera axis is not perpendicular to the surface of the specimen. Before deformation, at least three control points (circle mark point) are placed on the specimen surface, andA novel single-camera two-dimensional digital image correlation method based on photogrammetry correction is developed for the situation that the camera axis is not perpendicular to the surface of the specimen. Before deformation, at least three control points (circle mark point) are placed on the specimen surface, and the three-dimensional (3D) coordinates of the control points are measured by the photogrammetry. Then the camera orientation is calculated by the space resection method, and a control plane is obtained by fitting the control points. During deformation process, for each point in the image matched by digital image correlation, its corresponding 3D point is acquired by intersecting between the point ray and the control plane. Using this method, not only the measurement error introduced by slant axis of the camera is corrected, but also the displacement in millimeters rather than in pixels can be gained directly. Experimental results comparing with the existing 3D digital image correlation method show that, the displacement measurement accuracy by the proposed method is better than 0.04 mm, and the strain measurement accuracy is better than 0.5%..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1112007 (2011)
New High-Precision Method of Measuring Spatial Azimuth Based on Magnetooptic Modulation Polarized Light
Yang Zhiyong, Huang Xianxiang, Zhou Zhaofa, and Zhang Zhili
As the medium of azimuthal information, modulated polarized light can be used to transmit azimuthal information, and this technique can be widely applied in military, aerospace and biomedicine. The principle of measuring azimuth with magnetooptic modulation polarized light is expatiated on, and the error sources by exiAs the medium of azimuthal information, modulated polarized light can be used to transmit azimuthal information, and this technique can be widely applied in military, aerospace and biomedicine. The principle of measuring azimuth with magnetooptic modulation polarized light is expatiated on, and the error sources by existing methods are analyzed. In order to improve the measurement precision theoretically, the method of calculating azimuth directly is brought forward. The extremum of modulated light signal is extracted, and the equation between the extremum and azimuth is established. The equation′s solutions are analyzed, and the formula of calculating azimuth is acquired. At the same time, the measuring range of azimuth is wider because the double angle formula is introduced. The precision of the new method is compared with those of the existing methods. The results show that the theoretic measurement precision of the new one is higher and measuring range is wider. It provides a new way to measure spatial azimuth with high precision..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1112008 (2011)
Design and Experimental Study on Micro Infrared Radiometer Chip
Liang Zhongzhu
To meet the needs of high performance and microminiaturization of solar irradiance measuring instruments, the key device of absolute radiometerthe micro infrared radiation detection chip, is designed and its theories are analyzed. The bar type diamond with high mechanical performance, high thermal conductivity and highTo meet the needs of high performance and microminiaturization of solar irradiance measuring instruments, the key device of absolute radiometerthe micro infrared radiation detection chip, is designed and its theories are analyzed. The bar type diamond with high mechanical performance, high thermal conductivity and high insulation is used for the base of chip. NiP absorbent films that have a high absorptivity in wide spectral range are used to absorb light. The surfaces of nickel-phosphorus black film for infrared absorption have many irregular pores, with the diameters ranging from 50 nm to 10 μm. The reflectivity of NiP films is less than 0.4% at 1.5~16 μm, the transmittance is less than 0.15% at 1.5~16 μm, and the absorptivity is more than 0.99. Thin film resistor is made of constantan which has a good electrical performance. The resistor is prepared by micro-electro-mechanical system (MEMS) technology. The resistance of the thin film resistor is 50.3 kΩ and does not change with temperature, which can meet the requirement of the chip..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1112009 (2011)
Analysis of Focus Dislocation Induced by the Microlens Array Measuring Based on Grating Diffraction
Zhu Xianchang, Wu Fan, Cao Xuedong, Wu Shibin, and Zhang Peng
Compared with the traditional rotational method, a method for the focal length measurement of microlens array based on grating diffraction has a higher efficiency, because this method need not rotate the collimator. As microlens array has a large number of cells generally, the disturbance diffracted from nearby cells aCompared with the traditional rotational method, a method for the focal length measurement of microlens array based on grating diffraction has a higher efficiency, because this method need not rotate the collimator. As microlens array has a large number of cells generally, the disturbance diffracted from nearby cells also needs analysis. The interferences between 0-order and ±1-order diffracted focula of grating are analyzed by Matlab. The proper wavelength and grating can be determined for different kinds of microlens array by analyzing the wavelength, grating period, sub-aperture and focal length of microlens array. The disturbance can be avoided and the focal length measuring of microlens array can be finished. The experimental results show that this method is fit for the testing of microlens array with small F-number and many cells because of its high precision and efficiency..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1112010 (2011)
Integrated Optics
Research for Measuring the Multi-Mode Cut-Off Wavelength of LiNbO3 Waveguide Modulator Fabricated by Proton Exchange
Zhang Guang, Chen Baoxue, Fu Changsong, Sui Guorong, and Wang Guande
An inverted structure of Y-branch LiNbO3 waveguide for measuring the multi-mode cut-off wavelength of the phase modulator is proposed and experimented. Analysis of the mode coupling shows that the output power of the inverted Y-branch waveguide is cyclical fluctuated with the wavelength when the waveguide is in multi-mAn inverted structure of Y-branch LiNbO3 waveguide for measuring the multi-mode cut-off wavelength of the phase modulator is proposed and experimented. Analysis of the mode coupling shows that the output power of the inverted Y-branch waveguide is cyclical fluctuated with the wavelength when the waveguide is in multi-mode. And this characteristics can be used to judge the multi-mode cut-off wavelength. The validity of the method has been verified by simulation and experiment with sample..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1113001 (2011)
Lasers and Laser Optics
Properties of 3D Nanostructures Fabricated by Laser-Focused Cr Atomic Deposition
Zhang Pingping, Ma Yan, Zhang Baowu, and Li Tongbao
Periodic nanostructures fabricated by atom lithography using standing-wave light field can be applied for nanometrology. Atom-optical properties of 3D standing-wave light field are studied with particle optics model.The initial condition of each trajectory is stochastically selected with Monte-Carlo method, where the ePeriodic nanostructures fabricated by atom lithography using standing-wave light field can be applied for nanometrology. Atom-optical properties of 3D standing-wave light field are studied with particle optics model.The initial condition of each trajectory is stochastically selected with Monte-Carlo method, where the effects of isotope, longitudinal velocity distribution and transverse Gaussian divergence are systematically evaluated. 3D nanostructures with varying laser powers are presented,which shows the effect of longitudinal Gaussian distribution of the light field. The effect of elliptical standing wave is also discussed. It is shown that well-defined nano-grating lines appear in 87% of the substrate and full width at half maximum (FWHM) obtained at the center of Gaussian laser beam is 31 nm when the laser power is 40 mW. Good results can be obtained when the shape of the cross section of the standing wave is round..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1114001 (2011)
Numerical Simulation of Target-in-the-Loop Adaptive Optic Systems Based on Fiber-Laser Array
Tao Rumao, Si Lei, Ma Yanxing, Zou Yongchao, and Zhou Pu
The performance of target-in-the-loop adaptive optical systems based on fiber laser array in atmospheric environment has been investigated. A theoretic mode of target-in-the-loop adaptive optical systems based on fiber laser array has been set up. The effects of the systems on turbulence compensation under different tuThe performance of target-in-the-loop adaptive optical systems based on fiber laser array in atmospheric environment has been investigated. A theoretic mode of target-in-the-loop adaptive optical systems based on fiber laser array has been set up. The effects of the systems on turbulence compensation under different turbulence intensity are studied and the optimization of the control algorithm is discussed briefly. It is shown that the system can compensate the effect of turbulence effectively and improve the power density concentration by reducing the mean radius of the spot on the target by 9%. The performance of the system is affected by the intensity of the turbulence and the convergence rate of the control algorithm depends on the parameters of the algorithm. Finally the signal-to-noise ratio (SNR) of the detector also affect the performance of the system..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1114002 (2011)
Machine Vision
Reliability Evaluation Method and Application for Light-Stripe-Center Extraction
Wang Shun, Xu Jingzhu, Zhang Yixin, Zhang Xuping, and Xie Fei
In line structured light vision measurement, extraction of the light-stripe center is an extremely important step. The existing extraction methods simply give out the stripe center position. Few take it into account how reliable of the extraction result is. In some special occasions, such as outdoor measurement, the reIn line structured light vision measurement, extraction of the light-stripe center is an extremely important step. The existing extraction methods simply give out the stripe center position. Few take it into account how reliable of the extraction result is. In some special occasions, such as outdoor measurement, the reliability of the measurement results is greatly needed. Therefore, how to evaluate the reliability of the stripe center becomes a key problem. A reliability evaluation method for light-stripe-center extraction has been proposed, which is on the basis of the total energy of stripe cross section normalized by Gaussian model. Experimental results show that this method can effectively evaluate stripe center reliability in different situations, and the result is more consistent with practical need..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1115001 (2011)
Materials
Enhancement of Upconversion Luminescence in Li+ Codoping Er3+:Y2O3 Nanocrystals
Lü Jiantao, Wang Kejia, Liu Jinsong, Zhang Qingquan, Zhu Qihua, Zeng Xiaoming, and Yao Jianquan
The upconversion luminescent properties are investigated in Li+ and Er3+ codoped Y2O3 nanocrystals, especially the effect of the Li+ molar fraction on the crystalline structure and the luminescent intensity. Results indicate that the samples prepared by combustion method have good crystallinity even with high Li+ codopThe upconversion luminescent properties are investigated in Li+ and Er3+ codoped Y2O3 nanocrystals, especially the effect of the Li+ molar fraction on the crystalline structure and the luminescent intensity. Results indicate that the samples prepared by combustion method have good crystallinity even with high Li+ codoping concentration. The luminescent test results show that with the increase of the Li+ codoping concentration, the upconversion luminescent intensity of the nanocrystals in green and red range will enhance remarkably. The lattice symmetry of the nanocrystals is modified by codoping Li+, which increases the intra-4f transition probability in Er3+..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1116001 (2011)
Preparation and Luminescent Properties of One-Dimensional Nanorods Sr2SiO4:Eu2+ Phosphors
Zheng Jiming, Xu Yan, Lü Feng, Guo Chongfeng, and Ren Zhaoyu
Phosphors Sr2SiO4:Eu2+ with one-dimensional nanorod structure are prepared by a modified sol-gel method. The solution precursor containing SiO2 micro-spheres prepared by a Stober method is used as raw materials to synthesize. These phosphors are characterized by X-ray diffraction (XRD), field emission scanning electronPhosphors Sr2SiO4:Eu2+ with one-dimensional nanorod structure are prepared by a modified sol-gel method. The solution precursor containing SiO2 micro-spheres prepared by a Stober method is used as raw materials to synthesize. These phosphors are characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM) and energy disperse spectroscope (EDS). It is found that uniform Sr2SiO4:Eu2+ nanorods are synthesized by this method. Their luminescent properties are investigated. In addition, factors that affect their luminescent properties including the :Eu2+ ion concentration, heating time, sintering temperature and flux are also studied..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1116002 (2011)
Reaserch on Thermal and Optical Properties of Novel Ge-Te-Se-Sn Far Infrared Transmitting Chalcogenide Glasses
Sun Jie, Nie Qiuhua, Wang Xunsi, Dai Shixun, Xu Tiefeng, Zhang Xianghua, Bruno Bureau, Catherine Boussard, and Clément Conseil
A novel series of Ge20-xTe65Se15Snx(x=0,2,4) chalcogenide glasses is prepared by traditional melt-quenching method. Infrared thermal (8~12 μm) image, X-ray diffraction (XRD), differential scanning calorimetry (DSC), visible/near-infrared absorption spectroscopy and infrared transmission spectra are adopted to analyze tA novel series of Ge20-xTe65Se15Snx(x=0,2,4) chalcogenide glasses is prepared by traditional melt-quenching method. Infrared thermal (8~12 μm) image, X-ray diffraction (XRD), differential scanning calorimetry (DSC), visible/near-infrared absorption spectroscopy and infrared transmission spectra are adopted to analyze the composition, structure and performance of the Ge-Te-Se glasses system with addition of Sn. The Tauc equation is used to calculate the direct and indirect optical band gap. Based on the metallization criterion and band gap energy theory, the relation between optical band gap and composition is investigated. The results show that Ge-Te-Se-Sn glasses have good thermal stability. With the addition of Sn, the optical band gap of glass samples decreases, the short-wavelength edges shift to a longer wavelength, and the infrared cut-off wavelength almost keeps unchanged. Sn can weaken the intensity of the Ge-O absorption peak and improve the infrared transmission properties of glass samples..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1116003 (2011)
Rapid Self-Assemble of NaGdF4:Yb,Er Phosphorescent Materials by Microwave Assistant Method and Its Luminescent Properties
Tian Xueying, Liu Juan, Li Xilin, Zhao Wenxin, Li Hao, Yan Jinghui, Kang Zhenhui, and Lian Hongzhou
The Yb3+ and Er3+-codoped NaGdF4 is synthesized by microwave assistant method. The reaction time is only 25 min. The synthesized phosphor is investigated by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), energy-dispersion spectrometer (EDS) and upconversion (UC) spectrum, respectively. TThe Yb3+ and Er3+-codoped NaGdF4 is synthesized by microwave assistant method. The reaction time is only 25 min. The synthesized phosphor is investigated by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), energy-dispersion spectrometer (EDS) and upconversion (UC) spectrum, respectively. The results show that the NaGdF4Yb, Er phosphor possessed hexagonal crystal structure, which is basically spherical in shape. The sample is well-dispersity and its mean particle size is about 200 nm. When excited by the 980 nm laser, the NaGdF4Yb, Er phosphor has shown red and green upconversion emissions. The red emission intensity is stronger than green emission. Due to the unique upconversion emission property, the as-prepared NaGdF4Yb, Er might have potential application for further fundamental research and find applications in color displays and solid-state lasers..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1116004 (2011)
Medical Optics and Biotechnology
Image Reconstruction Algorithm for Endoscopic Diffuse Optical Tomography Based on Effective Detection Area
Qin Zhuanping, Zhao Huijuan, Zhou Xiaoqing, Yang Yanshuang, and Gao Feng
To reduce the cost of near-infrared endoscopic image equipment and the reconstruction time, a measurement method based on the effective detection area is proposed and the corresponding algorithm which simultaneously reconstructs the absorption coefficient and the reduced scattering coefficient is developed. Firstly, thTo reduce the cost of near-infrared endoscopic image equipment and the reconstruction time, a measurement method based on the effective detection area is proposed and the corresponding algorithm which simultaneously reconstructs the absorption coefficient and the reduced scattering coefficient is developed. Firstly, the effective detection area corresponding to an irradiation point is investigated with the Monte Carlo simulation. Secondly, the image reconstruction algorithm based on the effective detection area is studied. Finally, the impact of the number of measured points in the effective detection area on the reconstructed results is discussed, and the developed algorithm is verified by the simulation data. The results show that the reconstructed algorithm based on the effective detection area has equivalent accuracy to the traditional ones. The fidelities of the reconstructed absorption and reduced scattering coefficient can be up to 60% and 80%, respectively. The scales and positions of the reconstruced lesions are both corresponding to the true values and the reconstruction time is reduced by a half. The detection using the effective detection area and the developed reconstruction algorithm will promote the development of diffuse optical tomography which is applied to cervical and other tubular organs..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1117001 (2011)
Nonlinear Optics
Study of Coherent-Beat Modulation in Er3+-Doped Glass at Ultra-Low Temperature
Li Yuqiong, Zhang Yang, and Shen Jianqi
The photon echo of the Er2O3-doped TeO2-Nb2O5-ZnO glass is observed on the time-delay four-wave mixing with incoherent light (TDFWM-IL) experimental setup, at the temperature 7K and with the femtosecond pulse laser of 800 nm wavelength. Moreover, the interference-beat modulation of signal intensity versus delay time isThe photon echo of the Er2O3-doped TeO2-Nb2O5-ZnO glass is observed on the time-delay four-wave mixing with incoherent light (TDFWM-IL) experimental setup, at the temperature 7K and with the femtosecond pulse laser of 800 nm wavelength. Moreover, the interference-beat modulation of signal intensity versus delay time is found in the experiment. According to the multi-level theory of TDFWM-IL, the experimental result is fitted with the theoretical formula when the inhomogeneous broadening is dominant. The dephasing time T2=300 fs is gotten when the fitting is the best . Then the influence of the modulation parameter c on the structure of beat frequency modulation is studied. It is found that the photon echo beat frequency modulation structure appeares at the ultralow temperature, because it is affected by the coherent effect of the coherent excited states of many sub-levels. When the temperature gradually increases, the coherent-beat modulation structure disappeares, then the feature of the photon echo is similar to the TDFWM-IL two-level system. Thus a new theoretical basis for the coherent transient spectroscopy study of the rare earth materials at low temperature is provided..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1119001 (2011)
Propagation of Elegant Hermite-Gaussian Beams in Strongly Nonlocal Nonlinear Media
Zhang Xiaping
Based on the Snyder-Mitchell model that describes the paraxial beam propagating in strongly nonlocal nonlinear media and the trial solution with modulating the Gaussian beam by the parabolic cylinder functions, the close forms of elegant Hermite-Gaussian beams (EHGB) are accessed in Cartesian coordinate system. The colBased on the Snyder-Mitchell model that describes the paraxial beam propagating in strongly nonlocal nonlinear media and the trial solution with modulating the Gaussian beam by the parabolic cylinder functions, the close forms of elegant Hermite-Gaussian beams (EHGB) are accessed in Cartesian coordinate system. The collinear EHGB will evolve to be the rotating charge vortex EHGB on certain condition. It is shown that the transferring of the single EHGB and the rotating charge vortex EHGB at the critical power. The widths of the profiles of the breathers and the rotating charge vortex breathers are varied periodically in the transferring..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1119002 (2011)
Optical Design and Fabrication
Selection of Optical-System Parameters for an All-Day Used Star Sensor
Fan Qiaoyun, and Li Xiaojuan
The selection of optical-system parameters plays a key role in star sensors, which can affect the sensor′s performance. When determining the parameters, sky background radiance and parameters of image sensors should be considered. Sky background radiance under different situations is simulated by Modtran. A more accuraThe selection of optical-system parameters plays a key role in star sensors, which can affect the sensor′s performance. When determining the parameters, sky background radiance and parameters of image sensors should be considered. Sky background radiance under different situations is simulated by Modtran. A more accurate formula to estimate the detectable stellar magnitude limit is proposed, considering the effects of energy focusing degree and sensor noise. With this formula, the factors affecting the detectable stellar magnitude, detection probability and accuracy are deeply analyzed. The feasibility of typical optical-system parameters is studied. The results offer important references in the determination of optical system of all-day used star sensors..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1122001 (2011)
Research and Design of Telecentric Off-Axis Three-Mirror System with Real Entrance Pupil
Liu Xiaomei, and Xiang Yang
If in the telecentric off-axis three-mirror imaging system there is a beam-limited device in front of space remote instrument, a real entrance pupil to match is required. To meet this need, optical design of off-axis three-mirror system whose aperture stop coincides with the object focal plane in front of the primary mIf in the telecentric off-axis three-mirror imaging system there is a beam-limited device in front of space remote instrument, a real entrance pupil to match is required. To meet this need, optical design of off-axis three-mirror system whose aperture stop coincides with the object focal plane in front of the primary mirror is studied. The expressions of configuration parameters and the interval between the object focus and the primary mirror of off-axis three-mirror system are deduced in case that the primary mirror and the tertiary mirror are coplanar. The condition and solution of achieving real object focus are defined. Based on the method, with the specific requirements of 1.0～2.5 μm spectral range, F-number 4, 360 mm focal length, 5° field of view (FOV), a telecentric off-axis three-mirror system with real entrance pupil is designed. And the imaging quality of system approaches the diffraction limit at full FOV in the required wave band. The highest aspheric order is four. The result indicates that this method can be used in design of telecentric off-axis three-mirror imaging system with real entrance pupil..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1122002 (2011)
Magnification Tolerancing and Compensation for the Lithographic Projection Lens
Xu Weicai, Huang Wei, and Yang Wang
To meet the stringent overlay requirements, it is desirable to select appropriate elements to compensate and adjust the magnification of the projection lithographic lens with double telecentricity. A simple and practical method to tolerance the magnification is presented. This method uses the commercial optical design To meet the stringent overlay requirements, it is desirable to select appropriate elements to compensate and adjust the magnification of the projection lithographic lens with double telecentricity. A simple and practical method to tolerance the magnification is presented. This method uses the commercial optical design software and the finite difference algorithm to calculate the magnification sensitivity for some tolerances, and then selects the optimal magnification compensator with the consideration of the wave aberration sensitivity. By using this method, the magnification tolerance is analysed and the magnification compensator is selected for a projection lens with the working wavelength of 193 nm and numerical operture of 0.75. The results show that the lens achieves 50×10-6 magnification adjustment, and the root-mean-square degradation of lens wavefront aberration is less than 1.5 nm..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1122003 (2011)
Design of Beam Expanding Unit for Illumination System of DUV Lithography
Zhao Yang, Gong Yan, and Zhang Wei
The excimer laser beam is needed to be expanded in one dimension to meet the requirement of square cross-section distribution for beam shaping unit, because of the rectangular cross-section distribution characteristic of laser source for projected lithography which holds 90 nm exposure linewidth. The reported beam expaThe excimer laser beam is needed to be expanded in one dimension to meet the requirement of square cross-section distribution for beam shaping unit, because of the rectangular cross-section distribution characteristic of laser source for projected lithography which holds 90 nm exposure linewidth. The reported beam expanding units have the deficiencies of serious speckle effect of coherence and the strict tolerance to alignment. A kind of multi-component parallel reflective expander is proposed aiming at the shortages above. The structures of such beam expanding units are determined by calculating linear equation set. One of the structures, which is called four-component beam expanding unit, has only one transmissivity to reduce the cost of coating. A synthesis comparison is executed at the aspects of tolerance analysis, transmission efficiencies and uniformities of output beam. According to the simulation results, the designed four-component beam expanding unit is proven to be an optimal scheme by the evident reduction in speckle effect and tolerance sensitivity. Meanwhile, the homogeneity of output beam is improved, which is favorable to enhance the uniformity of the whole illumination system..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1122004 (2011)
Optics in Computing
Analysis on Beam Directing Stability Problem Caused by Micro-Vibration of Optical Components
Liu Fang, Xu Jia, Zhang Yan, Sun Mingying, and Zhu Jianqiang
A dynamic method is proposed to analyze the beam directing stability in both time and space domains aiming at solving the expression of the effects caused by micro-vibrations of optical components. Based on the structural modal analysis and vibration effects caused by optical components, the vibrational models of opticA dynamic method is proposed to analyze the beam directing stability in both time and space domains aiming at solving the expression of the effects caused by micro-vibrations of optical components. Based on the structural modal analysis and vibration effects caused by optical components, the vibrational models of optical components are built by combining structural modality and optical system. A spatial filter in SG-II facility is numerically simulated as an example based on the method, and the temporal distribution and spatial distribution are analyzed..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1120001 (2011)
Remote Sensing and Sensors
Research on Preprocessing Algorithm for Differential Polarization Spectrum of Oil Spills on Water
Yuan Yueming, Fang Yonghua, Cui Fangxiao, and Li Dacheng
When the oil spills on water are passively detected by differential polarization Fourier transform infrared (FTIR) spectroscopy in the band of 3~5 μm, the measured differential polarization spectrum will be a mixed spectrum of the strong atmospheric absorption signal and the minute signal of oil pollutant. It brings coWhen the oil spills on water are passively detected by differential polarization Fourier transform infrared (FTIR) spectroscopy in the band of 3~5 μm, the measured differential polarization spectrum will be a mixed spectrum of the strong atmospheric absorption signal and the minute signal of oil pollutant. It brings complexity to the identification of oil spills on water. In addition, the thickness distribution and the surface coarseness of oil film on water change with the influence of environmental factors and the tension of oil film. This makes the content of effective spectral information, which is contained in the differential polarization spectrum of oil spills on water, change continuously during the process of measurement. Using this characteristic, an algorithm based on a fast fixed-point algorithm for principal component analysis (FastPCA) is proposed for preprocessing the differential polarization spectrum of oil pollutant on water. Experimental results show that this algorithm can separate the spectral information of oil pollutant from the differential polarization spectrum with strong atmospheric absorption signal. The reconstructed spectral characteristic signal of oil pollutant can be used for the further qualitative and quantitative analyses..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1128001 (2011)
Method to Realize Autofocus of Remote Sensing Camera Based on the TDI Pattern of Interline Transfer Progressive Scan CCD
Meng Xixi, Feng Huajun, Xu Zhihai, Li Qi, and Chen Yueting
The picture captured by the remote sensing camera will be degenerated since the camera constantly rotates around the earth. The degenerated image may decrease the focusing accuracy. In order to solve this problem, a method based on the time delay and integration (TDI) pattern of interline transfer progressive scan CCD The picture captured by the remote sensing camera will be degenerated since the camera constantly rotates around the earth. The degenerated image may decrease the focusing accuracy. In order to solve this problem, a method based on the time delay and integration (TDI) pattern of interline transfer progressive scan CCD is proposed. The interline transfer CCD KAI-1003 is used as the imaging device, and PLD is used to control the driving timing signal for the sake of matching the velocity between CCD and object. In this way, the motion blur can be eliminated. The experimental results show that the imaging system not only eliminates the motion blur but also increases the signal to noise ratio (SNR) of the image. After removing the motion blur, an auto-focusing method of remote sensing camera is also proposed, with the feature that the images have overlapped regions captured in a short time. Firstly, the displacement and the overlapped regions of two adjacent images in the image sequences are calculated using the image registration algorithm. Then a sequence of focusing accuracy values through performing a sharpness evaluation function on the overlapped region of each image is obtained. Finally, according to the transfer characteristic, the evaluation value is mapped in a same evaluation system, and the accurate focus position is found. The experimental results indicate that the imaging system works pretty well for auto-focusing when the object moves in a high speed..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1128002 (2011)
Spectroscopy
Electron Temperature and Density of Soil Plasma Generated by Laser Ablation Fast Pulse Discharge Spectroscopy
Li Xiafen, Zhou Weidong, Qian Huiguo, and Li Kexue
Electron number density and temperature of soil plasma generated by laser ablation-fast pulse discharge plasma spectroscopic (LA-FPDPS) technique are studied. The experimentally measured line intensities of atomic and ionic states of silicon are used for electron temperature calculation from the Saha-Boltzmann equationElectron number density and temperature of soil plasma generated by laser ablation-fast pulse discharge plasma spectroscopic (LA-FPDPS) technique are studied. The experimentally measured line intensities of atomic and ionic states of silicon are used for electron temperature calculation from the Saha-Boltzmann equation. The electron number density is determined by using the Stark broadening of silicon 250.69 nm line emitted by the plasma. In comparison to the laser-produced plasma using the same laser energy, there is a considerable enhancement both in electron number density and electron temperature in plasma generated by LA-FPDPS of using a fast micro second discharge spark, which is consistent with the line intensity enhancement in LA-FPDPS..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1130001 (2011)
Thin Films
Precise Control of Thickness Uniformity in Mo/Si Soft X-Ray Multilayer
Zhu Yadan, Fang Ming, and Yi Kui
To fabricate large area soft X-ray multilayer with uniform optical properties, the thickness uniformity of single layer in a period structure must be well controlled. The method of single layer thickness uniformity analysis and control in magnetron sputtering system is established, and variable speed rotation of sampleTo fabricate large area soft X-ray multilayer with uniform optical properties, the thickness uniformity of single layer in a period structure must be well controlled. The method of single layer thickness uniformity analysis and control in magnetron sputtering system is established, and variable speed rotation of sample holder to realize the uniformity of large area soft X-ray multilayer is explained. Variable rotation curve is acquired by theoretical analysis. It is used in the variable speed rotation of sample holder to realize the uniformity of large area soft X-ray multilayer. The low angle X-ray diffraction (LAXRD) results reveal that LAXRD curves at different points of samples prepared by optimized variable speed rotation paths have nearly the same diffraction angles at the same diffraction order. This phenomenon proves that the multilayer thicknesses are nearly the same value. The calculation results indicate that the thickness non-uniformity of Mo layer can be controlled in 1.1% and Si layer can be controlled in 1.6% on an area with 200 mm diameter..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1131001 (2011)
Designs of Near Infrared Two-Waveband Non-Polarizing Beam Splitter
Wang Wenliang, and Hao Honggang
When used at oblique angle incidence, optical thin films exhibit strong polarization effects. This phenomenon will make the optical performance worsen in most application cases. But the design of optical thin film system to control the polarization effect is very difficult. The physical mechanism of the polarization efWhen used at oblique angle incidence, optical thin films exhibit strong polarization effects. This phenomenon will make the optical performance worsen in most application cases. But the design of optical thin film system to control the polarization effect is very difficult. The physical mechanism of the polarization effect is analyzed first, and then a near-infrared two-waveband nonpolarizing beam splitter at 1300~1330 and 1535~1565 nm spectral ranges with the splitting ratio of 11 is designed. The initial thin film stack is formed with a four-layer set and an equivalent layer using three all dielectric materials. Then it is optimized in multiple steps by simplex and conjugate gradient algorithms. According to the results, in the working spectrum range with the incident angle of 45°, it maintains a very low polarization ratio whether reflectance or transmittance induces phase changes..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 31, Issue 11, 1131002 (2011)
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