Contents
2012
Volume: 32 Issue 4
50 Article(s)
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Atmospheric Optics and Oceanic Optics
Study of Time-Domain Spreading Model of Ultrashort Gaussian Laser Pulses in Atmospheric Turbulence
Zhang Lu, Wu Zhiyong, Gao Shijie, and Cui Ming
The temporal spreading behavior of Gaussian laser pulses propagating through atmospheric turbulence is similar to the behavior of Gaussian pulses passing through Gaussian filter. Hence, a temporal spreading model, being a Gaussian filter approximated by cascading Butterworth filters in essence, is proposed for laser coThe temporal spreading behavior of Gaussian laser pulses propagating through atmospheric turbulence is similar to the behavior of Gaussian pulses passing through Gaussian filter. Hence, a temporal spreading model, being a Gaussian filter approximated by cascading Butterworth filters in essence, is proposed for laser communication channel simulation. The 3 dB frequency point of the approximated Gaussian filter is closely associated with the physical parameters of atmospheric turbulence, including the structural constant of refractive index as well as the outer scale size of turbulence, and propagation path length. So the spreading of the Gaussian pulses is combined with the parameters of atmospheric turbulence, and an analytic expression for modeling the spreading is obtained. This model and the analytic expression represented by the model′s parameters are not only valid in weak fluctuation regime but also in weak-moderate-strong regime..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 401001 (2012)
Measurement and Analysis Method of the Complex Refractive Index on Water-Soluble Aerosol by FTIR
Feng Mingchun, Gao Minguang, Xu Liang, Wei Xiuli, Cheng Siyang, Tong Jingjing, Li Xiangxian, Jin Ling, Li Sheng, and Jiao Yang
Studies indicate that current composition of atmospheric aerosol is complex, and its water-soluble ions affect air quality. The ions can produce significant negative effect on the human health. Therefore, rapid and reliable detection of water-soluble ion is an important research work in environmental science. Take SO2－Studies indicate that current composition of atmospheric aerosol is complex, and its water-soluble ions affect air quality. The ions can produce significant negative effect on the human health. Therefore, rapid and reliable detection of water-soluble ion is an important research work in environmental science. Take SO2－4 ion as an example, the extinction coefficient of water-soluble aerosol is measured by Fourier transform infrared spectroscopy (FTIR) technology, and the complex refractive index N is also calculated through theoretical analysis. By measuring the mass extinction cross section k and extinction coefficient α of the atmospheric aerosol water-soluble ion, the imaginary part ni of the complex refractive index N is calculated according to the extinction coefficient α and the real part nr of the complex refractive index N is also calculated by using the KK (Kramers-Kronig) relationship. The experimental results are also analyzed and discussed..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 401002 (2012)
Study on a Multi-Spectral-Band Infrared Sea Surface Temperature Radiometer System
Zhang Jian, Qu Enshi, Cao Jianzhong, Fan Zheyuan, and Jiao Guohua
A multi-spectral infrared radiometer system is designed that can be used to measure sea surface temperature automatically, whose resolution ratio and accuracy are better than 0.1 ℃ and ±0.5 ℃, respectively. The system adopts four spectral bands, i.e., 3.5～4.0 μm, 8～13 μm, 10.3～11.3 μm, and 11.5～12.3 μm. Its inner A multi-spectral infrared radiometer system is designed that can be used to measure sea surface temperature automatically, whose resolution ratio and accuracy are better than 0.1 ℃ and ±0.5 ℃, respectively. The system adopts four spectral bands, i.e., 3.5～4.0 μm, 8～13 μm, 10.3～11.3 μm, and 11.5～12.3 μm. Its inner optical system carries out real time calibration by two blackbody reference cavities with different temperatures, which promises that the high accuracy of an infrared radiometer is maintained even when optical components are moderately contaminated by salt deposition. Moreover, a protection shutter which could be automatically triggered by a sensitive rain gauge is designed to resist against foul weather. Finally, the accuracy and stability of the system are tested by laboratory calibration and shoreside experiment..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 401003 (2012)
Study on Optical Transmission Effect of Optical Window′s Cavity Flow
Feng Dinghua, Li Hua, Xiao Fei, Ding Guohao, Wang Wenlong, Tian Zhengyu, and Pan Sha
When the vehicle with optical seeker in its head side window flights at high speed in aerosphere, cavity flow phenomena occurs. So, the high-precision LER/RANS hybrid algorithm model is established to solve supersonic flow. The Settles three dimensional carity′s supersonic flow is studied. And then, on the basis of accWhen the vehicle with optical seeker in its head side window flights at high speed in aerosphere, cavity flow phenomena occurs. So, the high-precision LER/RANS hybrid algorithm model is established to solve supersonic flow. The Settles three dimensional carity′s supersonic flow is studied. And then, on the basis of accurate numerically calculated flow-field data, the optical transmission effect of the cavity shear layer region is researched. The results show that, the shear layer structure of cavity flow will cause light jitter, lead to severe wave-front distortion, reduce light intensity Strehl ratio significantly, and reduce the accuracy of the optical guidance..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 401004 (2012)
Dynamic Optimization Method for Modal Control of Adaptive Optics System
Li Bangming, Li Changwei, and Zhang Sijiong
The number of correction modes, an important parameter for the modal control of an adaptive optics system, has a significant effect on the system performance. The mode space of aberrations is built up by the singular value decomposition of the system′s response function matrix. The number of correction modes is determiThe number of correction modes, an important parameter for the modal control of an adaptive optics system, has a significant effect on the system performance. The mode space of aberrations is built up by the singular value decomposition of the system′s response function matrix. The number of correction modes is determined by the root mean square estimation of the residual aberration obtained under different numbers of correction modes. A dynamic optimization method for modal control of adaptive optics system is proposed. An adaptive optical experimental system mainly based on a Hartmann-Shack wavefront sensor and a membrane deformable mirror is constructed. The above control method is verified by fitting different aberrations. Results show that the residual aberration with correction by the dynamic optimization method of modal control is smaller than the one with correction by the method of the fixed mode number, and the spatial fitting performance of the adaptive optics system can be obviously improved..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 401005 (2012)
Coherence and Statistical Optics
Characteristics Analysis of the Photons Arrival Time Interval of Laser Beat Signal
Liu Lisheng, Zhang Heyong, Zhao Shuai, and Guo Jin
In order to get the frequency of periodic laser beat signal, the probability density function (PDF) of time interval between two successive photoelectrons is derived theoretically. The difference of the shape in the PDF curve between the beat signal and stable light signal is obvious, and the beat frequency can be deriIn order to get the frequency of periodic laser beat signal, the probability density function (PDF) of time interval between two successive photoelectrons is derived theoretically. The difference of the shape in the PDF curve between the beat signal and stable light signal is obvious, and the beat frequency can be derived from the difference. An experiment system is designed in which a multi-pixel photon counter (MPPC) is used to record the photoelectrons time of the beat signal with beat frequency of 6, 8, 10 MHz and 12 MHz to give a potent verification to the theory. The experimental result is even much better in the condition that the photons count rate is 1/5 of the beat frequency, and an estimation of the mixing efficiency can be obtain using the statistics method which is 0.65 in our experiment. In the limitation of the dark count noise of the MPPC, the minimum beat frequency of periodic signal is 0.2333 MHz detected using this method..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 403001 (2012)
Detectors
Nonlinearity Property Testing of the Scientific Grade Optical CCD
Cheng Shubo, Zhang Huige, Wang Zhebin, Yi Yougen, Zhang Chen, Liu Hao, and Zheng Zhijian
In inertial confinement fusion (ICF) experimental studies, scientific-grade CCD coupled with streak camera is widely used in time and space diagnosis experiment with physical processes such as shock wave. As a significant property of the scientific grade CCD, nonlinearity plays an important role in experimental dealingIn inertial confinement fusion (ICF) experimental studies, scientific-grade CCD coupled with streak camera is widely used in time and space diagnosis experiment with physical processes such as shock wave. As a significant property of the scientific grade CCD, nonlinearity plays an important role in experimental dealing. The experiment tests the nonlinearity property of the TEK 512×512DB CCD with the two schemes respectively: that the exposure time is fixed, the power density of the RS-5B is varied; power density is fixed, the exposure time is varied, and it shows the nonlinearity of the CCD is 0.595% and 0.508% respectively, meanwhile, the two experimental scheme are evaluated by analyzing kinds of factors, indicating that the first scheme is better, which provides the reference for establishment of automated testing platform..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 404001 (2012)
Dark-Current Calculation Method of Area CCD Based on Bad Pixels Detection in the Scene
Cheng Xuan, and Zhao Huijie
Bad pixels in the area CCD detector are used as temperature sensor, to estimate the CCD temperature, and to establish the function model between the CCD temperature and the dark current. In order to make the result insensitive to noise; mean filtering method is used to estimate the CCD temperature in the image of the rBad pixels in the area CCD detector are used as temperature sensor, to estimate the CCD temperature, and to establish the function model between the CCD temperature and the dark current. In order to make the result insensitive to noise; mean filtering method is used to estimate the CCD temperature in the image of the real scene. After extraction of the CCD temperature of the real scene, the dark current of area can be estimated. Based on analysis of the method, using the real dark current as standard, the result of the dark current estimation has been validated. The experiment shows that the estimation of the dark current is very exact in both different integration time and large dynamic range conditions with the rate of error under 0.4%. Furthermore, it is not sensitive to the noise within the images. The method uses the character of the image to estimate dark current, so it is not necessary to collect the dark-current data, and the image acquisition time can be saved. Therefore, this method is very suitable to the low-cost CCD imaging system without temperature control for real-time image acquisition in hyper-spectral imaging or astronomical observation fields..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 404002 (2012)
Diffraction and Gratings
Comparison of Transmission Properties of Two Kinds of Subwavelength Metallic Wave Plates
Chen Juan, Yan Lianshan, Pan Wei, Luo Bin, and Guo Zhen
Based on the equivalent medium theory and surface-plasmon-polariton (SPP) Bloch model, two kinds of novel metallic waveplates are analyzed: two-dimensional rectangular metallic grating and elliptical cylinder metallic grating. First, utilizing the finite-difference-time-domain (FDTD) method, we analyze the relation betBased on the equivalent medium theory and surface-plasmon-polariton (SPP) Bloch model, two kinds of novel metallic waveplates are analyzed: two-dimensional rectangular metallic grating and elliptical cylinder metallic grating. First, utilizing the finite-difference-time-domain (FDTD) method, we analyze the relation between characteristics of both waveplates in terms of the transmittance and phase retardation and parameters of the incident light in terms of the wavelength and polarization angle, especially transmission properties of both gratings functioning as quarter-wave plates. Simulation results show that both structures can act as quarter-wave plates when the input polarization angle is 75°. The corresponding transmittances of rectangular and elliptical cylinder gratings are 0.77 and 0.67, respectively. In addition, both gratings exhibit relatively flat transmission spectra within the wavelength range from 550 nm to 800 nm in the presence of different input polarization angles..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 405001 (2012)
Fiber Optics and Optical Communications
Study on Bit-Symbol Mapping Method of MPPM and System Performance Based on Low Density Parity Check Codes
Leng Jiaofeng, Hao Shiqi, Lü Xuguang, Zhou Jianguo, and Wang Yong
Wireless optical communication system based on low density parity check (LDPC) codes and multi-pulse position modulation (MPPM) is established, and the decoding algorithm is introduced according to the system model. Bit-symbol mapping method of (m,2) MPPM is studied, and a novel bit-symbol mapping method is presented bWireless optical communication system based on low density parity check (LDPC) codes and multi-pulse position modulation (MPPM) is established, and the decoding algorithm is introduced according to the system model. Bit-symbol mapping method of (m,2) MPPM is studied, and a novel bit-symbol mapping method is presented based on modified genetic algorithm(GA), which is simulated under turbulence channel. The simulation results show that LDPC codes have excellent error correction capabilities with MPPM, and the wireless optical communication based on multiple-beam propagating technique and LDPC codes can operate under a strong atmospheric turbulence. Bit-symbol mapping method optimized by GA can get more coding gain without increasing complication..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 406001 (2012)
Research on Power Efficient Routing Algorithm in Green Optical Networks
Guo Aihuang, Feng Shengyi, Xue Lin, and Zhang Jian
In traditional routing algorithms, shortest-path algorithm (SPA) is often used. The distance between two nodes is defined as weight, and a path from the source node is selected to the destination node which has the minimum weight to finish routing. Although SPA minimizes the distance cost, it doesn′t consider the issueIn traditional routing algorithms, shortest-path algorithm (SPA) is often used. The distance between two nodes is defined as weight, and a path from the source node is selected to the destination node which has the minimum weight to finish routing. Although SPA minimizes the distance cost, it doesn′t consider the issue of energy consumption. So the routing path generated by SPA may not have the minimum energy cost. To solve this problem, a new integrated green routing algorithm is proposed. This algorithm defines energy consumption as the weight of each link. It combines optical bypass and traffic grooming and also considers routing and wavelength assignment (RWA) problem in order to minimize the energy cost of every routing process, which leads to energy-saving. The result of simulation shows that compared with SPA, green routing algorithm can save about 40% energy consumption in large-scale networks. Its energy-saving effect is considerable..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 406002 (2012)
An Octal Modulation Scheme Based on Serial Minimum Frequency Shift Keying Modulation Format
Tao Li, and Chi Nan
An advanced serial minimum frequency-shift keying (SMSK) modulation scheme is proposed. SMSK signal has a narrow power spectrum, and continuous phase shift that changes π/2 twice during one symbol time, which is similar to traditional minimum frequency-shifts (MSK) signal. The principle of generating the optical SMSK sAn advanced serial minimum frequency-shift keying (SMSK) modulation scheme is proposed. SMSK signal has a narrow power spectrum, and continuous phase shift that changes π/2 twice during one symbol time, which is similar to traditional minimum frequency-shifts (MSK) signal. The principle of generating the optical SMSK signal and its implementation in octal multi-dimensional and multi-level modulation scheme is presented. Theoretical analysis is given to modulated spectra, residual dispersion tolerance, self-phase modulation (SPM) tolerance and effect of filter bandwidth on it. 120 Gb/s simulated transmission over 350 km fiber link with dispersion compensation is demonstrated..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 406003 (2012)
Holography
Transmission Type of Collinear Volume Holographic Storage Technology Based on LiNbO3 Crystal
Li Jianhua, Cao Liangcai, Tan Xiaodi, He Qingsheng, and Jin Guofan
Collinear (Coaxial) volume holographic data storage (CVHDS) is one of the promising technologies for the commercialization of the volume holographic data storage. In order to optimize the parameters for the construction of transmission type of CVHDS system, some CVHDS properties such as storage density, crosstalk charaCollinear (Coaxial) volume holographic data storage (CVHDS) is one of the promising technologies for the commercialization of the volume holographic data storage. In order to optimize the parameters for the construction of transmission type of CVHDS system, some CVHDS properties such as storage density, crosstalk characteristics and crystal storage property are investigated. The relation between the storage density of CVHDS and the parameters of objective lens, the pixel pitch of the spatial light modulator (SLM), the effective pixel number of the SLM and the shift pitch for multiplexing are theoretically derived. The physical interpretation for the expression of the point spread function is proposed. The crosstalk property is analyzed for different reference patterns based on point spread function. Then the polarization state in the photorefractive crystal is optimized for as larger dynamic range as possible. Finally, the transmission type of CVHDS system based on LiNbO3 crystal is constructed for the data-storage experimental test. Data-storage experimental results indicate that pictures with high resolution can be recorded and reconstructed with high fidelity by this system. Compared with the two-axis geometry, the optical setup of the CVHDS system is more concise and smaller in size..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 409001 (2012)
Flat-Field Concave Holographic Grating with Broad Spectral Region and High Resolution
Wu Jianfen, Zhao Lei, Chen Yongyan, Zhou Chao, Wang Taisheng, and Wang Yu
To realize flat-field concave holographic grating with high resolution and broad spectral region, Namioka concave grating theory, genetic algorithm, simultaneous free-aberration and common diffractive orders are combined to produce the ideas and method of designing flat-field concave holographic grating. A configuratioTo realize flat-field concave holographic grating with high resolution and broad spectral region, Namioka concave grating theory, genetic algorithm, simultaneous free-aberration and common diffractive orders are combined to produce the ideas and method of designing flat-field concave holographic grating. A configuration simulation based on flat-field concave holographic grating is presented, whose root mean square (RMS) spot radius of spot diagrams is given. The RMS spot radius is around 11 μm in full spectral region 200~800 nm. While a 10 μm×1 mm entrance slit is used, the illumination spectrum image show that the resolution is 0.25 nm and 0.5 nm in 200~400 nm and 400~800 nm spectral region, respectively. All prove that these ideas and methods are available in designing compact and utilitarian spectrometer..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 409002 (2012)
Depth Selectivity of Aperiodic Volume Grating in Holographic Imaging System
Lin Lin, Wan Yuhong, Chen Hao, Wu Jiangtao, Jiang Zhuqing, and Tao Shiquan
The volume grating formed by interfernce of one spherical wave and a planar wave is aperiodic due to its grating vector changes within the volume of hologram. The depth selectivity of aperiodic volume holographic gratings is investigated as spatial-spectral filters in volume holographic imaging systems. The diffractiveThe volume grating formed by interfernce of one spherical wave and a planar wave is aperiodic due to its grating vector changes within the volume of hologram. The depth selectivity of aperiodic volume holographic gratings is investigated as spatial-spectral filters in volume holographic imaging systems. The diffractive characteristics of aperiodic volume holographic grating is analyzed by regarding it as an ensemble of local planar gratings cooperating with Kogelnik coupled-wave method. The depth selectivity of an aperiodic and a periodic grating are simulated respectively, and the effect of recording angle on the depth selectivity of aperiodic grating is simulated. Experiments of recording and retrieving volume gratings in photorefractive crystal are designed and implemented in order to verify our simulation results..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 409003 (2012)
Imaging Systems
Design and Analysis of CMOS Camera Based on Time Delay and Integration in Digital Domain to Realize Spatial High-Resolution Imaging
Tao Shuping, Jin Guang, Qu Hongsong, He Xiaojun, and Yang Xiubin
In order to make the complementary metal-oxide-semiconductor (CMOS) sensor with many advantages more suitable for spatial high resolution imaging, and look for new imaging techniques, a new algorithm called rolling time delay and integration (TDI) in digital domain is proposed, which is better for low light level and pIn order to make the complementary metal-oxide-semiconductor (CMOS) sensor with many advantages more suitable for spatial high resolution imaging, and look for new imaging techniques, a new algorithm called rolling time delay and integration (TDI) in digital domain is proposed, which is better for low light level and push broom imaging. Then the noise sources and their characteristics are analyzed in detail to study the CMOS imaging system′s quality, and a mathematical model of the relation between the digital integrated images′ signal-to-noise ratio (SNR) and integration stages is established. The influence of integration time and illuminance on SNR is dissussed. Finally, validation experiments are carried out using the designed IBIS5-B-1300 TDI CMOS principle prototype. Experimental results show that the proposed algorithm could improve image quality significantly, where the image′s SNR after integrating 10 stages by the proposed algorithm increased to 29.21 dB from the non-integration′s 19.07 dB, and the SNR increased with the stage′s increasing. Theoretical analysis and experimental validation both show that the rolling TDI in digital domain can improve the image SNR by M(σAD+σCMOS)/(MσAD+MσCMOS) times, and the parameters of σAD and σCMOS are related to the selected CMOS sensor, what′s more, σCMOS is effected by the integration time and illuminance..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 411001 (2012)
Influences of Spiral Phase Plate′s Parameters on Spiral Phase Contrast Microscopy
Wang Jiong, Zhang Yudong, Li Guojun, Luo Xiangang, Zhang Xiaojun, and Yang Hansheng
The imaging law of diffraction-limited spiral phase contrast microscope under coherent illumination condition is derived. Three parameters of spiral phase plate that influence the imaging quality, i.e., central size, size and step number, are pointed out. Exhaustive investigations into the influences of the three paramThe imaging law of diffraction-limited spiral phase contrast microscope under coherent illumination condition is derived. Three parameters of spiral phase plate that influence the imaging quality, i.e., central size, size and step number, are pointed out. Exhaustive investigations into the influences of the three parameters on the imaging results are made, and their reasonable values are presented. The validity is confirmed by experiments. This method is useful in designing the spiral phase plate. Moreover, it is also valid for designing the filters based on spatial filtering..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 411002 (2012)
Instrumentation, Measurement and Metrology
Calibration of Binocular Stereo Measurement System Based on Calibration Cross
Sun Nan, Zhang Liyan, Ye Nan, and Wang Hongtao
A calibration method of binocular stereo measurement system is proposed based on calibration cross. The intrinsic parameters of the two cameras are calculated precisely and the three-dimensional (3D) target point sets are reconstructed in each camera coordinate system respectively by using the multiple-view geometricalA calibration method of binocular stereo measurement system is proposed based on calibration cross. The intrinsic parameters of the two cameras are calculated precisely and the three-dimensional (3D) target point sets are reconstructed in each camera coordinate system respectively by using the multiple-view geometrical constraint and a generic sparse bundle adjustment. Then the extrinsic parameters are calculated by using the rigid-body transform of the two 3D point sets. This method is simple and flexible for field operation because it only needs the calibration cross to be photographed by two cameras simultaneously once and then separately several times. Based on a binocular stereo measurement system calibrated by the proposed method, a staff gauge of 611.800 mm long is measured many times. The result shows that the average measurement value is 611.776 mm, and standard deviation is 0.030 mm..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 412001 (2012)
Measurement System of Optical Homogeneity of Large-Size Optical Material Based on Subaperture Stitching Technique
Xu Xinhua, Wang Qing, Song Bo, and Fu Ying
In order to realize high-precision, low-cost measurement of optical refractive-index homogeneity of large-size optical material, an interference absolute testing method based on subaperture stitching technique is proposed and a measurement system comprised of a Zygo interferometer, a sophisticated five-dimensional adjuIn order to realize high-precision, low-cost measurement of optical refractive-index homogeneity of large-size optical material, an interference absolute testing method based on subaperture stitching technique is proposed and a measurement system comprised of a Zygo interferometer, a sophisticated five-dimensional adjustment air-floatation platform, subaperture stitching software and a computer is developed. The optical component under test is placed on the five-dimensional adjustment platform and all subaperture areas of the component can be measured precisely by moving the platform. Then optical-homogeneity distribution of the whole optical component is calculated out automatically by subaperture stitching software. In the experiment, a 300 mm quartz optical component is measured in stitching mode of eight subapertures by using a 180 mm interferometer. The stitching result is compared with the direct measurement result obtained by using full-aperture interferometer. The relative error of wavefront peak-to-valley value is 0.21%, the relative error of optical homogeneity value is 0.23%. This precision can be compared with the precision of directly measured result. The practicability of subaperture stitching technology of plane-type wavefront measured by using absolute test method is realized. The whole system integrates optics, mechanics, electrics and computer together and can be operated conveniently with high accuracy..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 412002 (2012)
Method Acquiring the Demodulation Coefficients of Intensity-Modulated Spectropolarimeter by Measuring Reference Light
Song Zhiping, Hong Jin, and Qiao Yanli
A novel method is presented to acquire the demodulation coefficients of the intensity-modulated spectropolarimeter (IMS) by measuring the reference light, for the demodulation coefficients obtained by theoretical calculation cannot demodulate the measured data. The demodulation coefficients of IMS can be separated fromA novel method is presented to acquire the demodulation coefficients of the intensity-modulated spectropolarimeter (IMS) by measuring the reference light, for the demodulation coefficients obtained by theoretical calculation cannot demodulate the measured data. The demodulation coefficients of IMS can be separated from the intensity spectrum of the reference light passing through the modulator of the IMS, and it is necessary to process the intensity spectrum, such as IFFT, filtering and FFT etc. The principle of the method is analysed in details and the measured results of the demodulation coefficients for IMS prototype are presented. The measured data of quasi-natural light and polarized light from IMS prototype is demodulated by the demodulation coefficients obtained to verify their validity. Experimental results show that the polarization degree of the light from a tungsten-halogen lamp collimator directly is less than 10%, but it is about 100% when the light is polarized by a polarizer in the spectral range of 550~650 nm. These results are coincident with the theoretical results well, which verify the feasibility of the method presented before..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 412003 (2012)
Research on Method of Calibrating Sun Channels of Sun Radiometers
Zhai Wenchao, Li Jianjun, Zheng Xiaobing, Li Zhengqiang, Meng Binghuan, Zhang Wei, and Wang Xianhua
A new calibration method of absolute spectral irradiance responsivity of sun radiometer named CE318 is described. In this method, a tunable laser and a standard irradiance detector which can be traced from the cryogenic absolute radiometer are used as source and transferring standard, respectively. In the experiment, tA new calibration method of absolute spectral irradiance responsivity of sun radiometer named CE318 is described. In this method, a tunable laser and a standard irradiance detector which can be traced from the cryogenic absolute radiometer are used as source and transferring standard, respectively. In the experiment, to acquire the uniform, stable and unpolarized irradiance field, the laser which is stabilized by a laser power controller, wavelength by wavelength, is steered into an integrating sphere with which a speckle-removal device is equipped. By the vicarious calibration technique, the spectral irradiance responsivities of the 870 nm sun channels of CE318 consisting of three polarized channels (P1, P2 and P3) and an unpolarized channel (UP) are obtained and used to predict the top-of-the-atmosphere signals, respectively. In the last, the uncertainties of calibration are evaluated and reach to 1.83%, 1.98%, 1.73% and 1.2%, which are comparable to the counterparts of Langley method, the main method of calibration in this field..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 412004 (2012)
Single Color Fringe Projection for Measuring Three-Dimensional Shapes with Discontinuities
Dai Meiling, Yang Fujun, Geng Min, He Xiaoyuan, and Kang Xin
A novel fringe projection profilometry used for discontinuous shape measurement is proposed. One color fringe pattern generated by computer encoding with a sinusoidal fringe and two uniform intensity patterns is projected by a digital video projector and the deformed fringe pattern is recorded by a color CCD camera. ThA novel fringe projection profilometry used for discontinuous shape measurement is proposed. One color fringe pattern generated by computer encoding with a sinusoidal fringe and two uniform intensity patterns is projected by a digital video projector and the deformed fringe pattern is recorded by a color CCD camera. The captured color fringe pattern is separated into its RGB components and division operation is applied to red and blue channels to reduce the variable reflection intensity. Shape information of tested object is decoded by applying an arcsine algorithm on the subpixel-scale normalized fringe pattern. To determine the shadow and dark background, the separated blue component is binarized and used to guide the phase extraction. The experimental results demonstrate the validity of the proposed method for discontinuous and dynamical shape measuring..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 412005 (2012)
Phase Error Model from Gamma distortion and Gamma Calibration
Zhang Xu, and Zhu Limin
The Gamma nonlinearity is one of the most important factors for the phase error in digital phase measuring profilometry. The phase error model resulting from the Gamma distortion is deduced, which reflects the relation between the phase error and the harmonic coefficients. The recurrence formula of the harmonic coefficThe Gamma nonlinearity is one of the most important factors for the phase error in digital phase measuring profilometry. The phase error model resulting from the Gamma distortion is deduced, which reflects the relation between the phase error and the harmonic coefficients. The recurrence formula of the harmonic coefficients is proved, which is influenced by the Gamma value. Based on this recurrence rule, a Gamma calibration method based on discrete Fourier transform is proposed. Discreet Fourier transform is applied to obtain the harmonic coefficients. Then, this Gamma value is computed and adopted to correct the nonlinearity. In the experiment, the mean Gamma value in the whole image is employed into the gamma pre-encoding process. With the proposed technique, the phase error is reduced by 77.5% in the standard variance and the surface quality is enhanced..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 412006 (2012)
Measurement of Diffraction Efficiency for Diffractive Optical Elements
Yang Liangliang, Cui Qingfeng, Liu Tao, and Xue Changxi
According to the measuring principle of diffraction efficiency for diffractive optical elements, the double light-path measurement device of diffraction efficiency is set up. The advantages of double light-path measurement are briefly introduced. For the measurement device of diffraction efficiency for diffractive optiAccording to the measuring principle of diffraction efficiency for diffractive optical elements, the double light-path measurement device of diffraction efficiency is set up. The advantages of double light-path measurement are briefly introduced. For the measurement device of diffraction efficiency for diffractive optical elements, the factors having influence on the accuracy of the measurement results are discussed by the reasonable choices of the pinhole aperture of the measurement device, the light of the main diffraction order can be received by the detector, and the secondary diffraction light will be filtered out, ensuring the accuracy of the measurement results. The diffraction efficiency of the designed hybrid refractive-diffractive optical system is measured at three laser wavelengths over the visible waveband. The measurement results are simulated and analyzed. The deviation of the measurement results from the theoretical value is less than 5.0% over the 473~632.8 nm waveband. The double light-path measurement device can be used to measure the diffraction efficiency of diffractive optical elements..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 412007 (2012)
Lasers and Laser Optics
Measurement for Linewidth of an External Cavity Diode Laser Based on Monolithc Fabry-Perot Cavity with Delayed Self-Heterodyne Method
Peng Yu, Li Ye, Cao Jianping, Fang Zhanjun, and Zang Erjun
An narrow-linewidth external-cavity diode laser (ECDL) is presented based on a parallel monolithic folded Fabry-Perot (F-P) cavity. The frequency of the laser is locked to the monolithic F-P resonance by optical feedback. Linewidth of the laser is measured with delayed self-heterodyne method. Experimental results show An narrow-linewidth external-cavity diode laser (ECDL) is presented based on a parallel monolithic folded Fabry-Perot (F-P) cavity. The frequency of the laser is locked to the monolithic F-P resonance by optical feedback. Linewidth of the laser is measured with delayed self-heterodyne method. Experimental results show the linewidth of ECDL is narrower than 35 kHz. Linewidth of ECDL changes when the position of coupling on the input/output plane changes..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 414001 (2012)
Machine Vision
Mirror Pose Self-Calibration Method for Catadioptric Camera System
[in Chinese], [in Chinese], and [in Chinese]
Given the parameters of the mirror shape and the camera, a self-calibration method for catadioptric camera system is proposed to estimate the mirror pose with respect to the camera by using only one image containing no special designed calibration pattern. The ellipse corresponding to the mirror boundary in the image iGiven the parameters of the mirror shape and the camera, a self-calibration method for catadioptric camera system is proposed to estimate the mirror pose with respect to the camera by using only one image containing no special designed calibration pattern. The ellipse corresponding to the mirror boundary in the image is used to compute possible mirror pose by planar circular posture estimation. With two pose candidates thereafter, the correct pose and the parameter of lens boundary simultaneously is found by matching the predicted and the observed image of lens boundary. The method features easy-operating, high accuracy and is suitable for non-single viewpoint system. Experimental results both on synthesized and real images demonstrate the validity of our method..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 415001 (2012)
Detection System for Solar Module Surface Defects Based on Constrained ICA Model and PSO Method
Gong Fang, Zhang Xuewu, and Sun Hao
According to the characteristics of infrared imaging and the electroluminescent principle of solar module, a detection system based on constrained independent component analysis (ICA) model and particle swarm optimization (PSO) method for solar module surface defects is proposed. Firstly, a constrained ICA filter is deAccording to the characteristics of infrared imaging and the electroluminescent principle of solar module, a detection system based on constrained independent component analysis (ICA) model and particle swarm optimization (PSO) method for solar module surface defects is proposed. Firstly, a constrained ICA filter is designed on the basis of the structure characteristics of infrared image for solar cells, and PSO method with multidirectional search characteristics is used to find the best demixing matrix for ICA. The constraint incorporated in the ICA model confines the source values of all training image patches of a defect-free image within a small interval of control limits and highlights the value of defect region. Then, ICA filter is used to convolve with the image. Finally, defect results are obtained through threshold segmentation. Experimental result shows that the proposed method can effectively detect the defects on solar module surface..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 415002 (2012)
Medical Optics and Biotechnology
Membrane Potential Dynamics of Nerve Fibers Fast Probed by Action-Potential-Encoded Second Harmonic Generation
Yang Hongqin, Chen Xinguang, Huang Yimei, Luo Zhihui, Li Hui, and Xie Shusen
Action potential dynamics of nerve fibers is related to the information conduction and code among neurons. Nowadays, traditional electrophysiologic approach still could not fast probe the action potential dynamics simultaneously at multiple positions on nerve fibers. Nonlinear optical second harmonic generation combineAction potential dynamics of nerve fibers is related to the information conduction and code among neurons. Nowadays, traditional electrophysiologic approach still could not fast probe the action potential dynamics simultaneously at multiple positions on nerve fibers. Nonlinear optical second harmonic generation combined with mathematical modeling is used to study the characteristics of myelinated nerve fibers. The detected sensitivity of the method is analyzed at first, and then, the information changes induced by the changes in morphology including axonal diameter and myelin thickness on a myelinated nerve fiber under a compression are investigated. The results demonstrate that changes in membrane potential induced by a compression may be fast probed via second harmonic generation. Furthermore, the action potential conduction is blocked when severe demyelination happens on the nerve fiber. It is shown that optical second harmonic generation is a potential tool to evaluate the injured states of nerve fibers..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 417001 (2012)
Monte Carlo Simulation of the Focused Beam Propagation in a Semi-Infinite Bio-Tissue
Zhang Lin, Li Xiaoxia, and Qi Shengwen
The focused beam propagation in turbid medium is analyzed. A Monte Carlo simulation model for simulating the focused flat circular beam propagation in a semi-infinite bio-tissue is constructed. Using this model, we study the absorbed photon density with different tissue parameters in the case of a focused flat circularThe focused beam propagation in turbid medium is analyzed. A Monte Carlo simulation model for simulating the focused flat circular beam propagation in a semi-infinite bio-tissue is constructed. Using this model, we study the absorbed photon density with different tissue parameters in the case of a focused flat circular beam injecting the tissue. The simulation results show the law of optical propagation in the tissue..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 417002 (2012)
Microscopy
Large Range Autofocusing Algorithm for Microscopy with Small Depth of Field
Zhai Yongping, Zhou Dongxiang, and Liu Yunhui
Auto-focusing is one of the key issues in automatic microscopy. The traditional methods suffer from the small search range and are sensitive to the starting position. An autofocusing algorithm for guiding automatic search of the optimal focal plane under large search range for microscopy with small depth of field is prAuto-focusing is one of the key issues in automatic microscopy. The traditional methods suffer from the small search range and are sensitive to the starting position. An autofocusing algorithm for guiding automatic search of the optimal focal plane under large search range for microscopy with small depth of field is proposed. The autofocusing procedures are divided into six types, including two basic types and four complex types, based on the correlations of the defocus distance, the search direction, the search range and the parameters of the focusing curve. Then, the complex types are transformed into the basic types using the changes information of the values of the focusing functions. Therefore, the large search range is transformed into small search range and the traditional extremum search method, i.e. Gaussian curve fitting method can be used for guiding automatic search of optimal focal plane. Experimental investigation has been conducted to demonstrate the validity of the proposed method..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 418001 (2012)
Nonlinear Optics
Spatiotemporal Instabilities in Nonlinear Asymmetric Oppositely Directional Coupler with a Negative-Index Metamaterial Channel
Yi Peng, Xiang Yuanjiang, Dai Xiaoyu, Ding Mingyao, and Wen Shuangchun
Spatiotemporal modulation instabilities (MI) in nonlinear asymmetric oppositely directional coupler with negative-index metamaterial are investigated. The influences of input power, power ratio of the forward- and backward-propagating waves, and coupling coefficients on the spatiotemporal MI are discussed. It is found Spatiotemporal modulation instabilities (MI) in nonlinear asymmetric oppositely directional coupler with negative-index metamaterial are investigated. The influences of input power, power ratio of the forward- and backward-propagating waves, and coupling coefficients on the spatiotemporal MI are discussed. It is found that the MI can occur only if the transverse wave numbers satisfy the threshold condition. The results also show that increasing the input power or decreasing power ratio of the forward- and backward-propagating waves promotes the spatiotemporal MI and merges different instability regions together. Moreover, decreasing the coupling coefficient can suppress the peak gain and spread the gain spectrum. The controllable electromagnetic parameters of negative-index metamaterials will provide more methods to engineer the MI and soliton formation in this coupler..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 419001 (2012)
Separate Holographic Soliton Pairs in a Biased Series Two-Photon Photorefractive Crystal Circuit
Ji Xuanmang, Jiang Qichang, and Liu Jinsong
In order to study the two-photon separate holographic soliton pairs, based on the two-wave coupling and two-photon photorefractive effect in photorefractive crystals, holographic bright (dark) screening solitons are predicted in a series circuit consisting of double two-photon photorefractive crystal connected electronIn order to study the two-photon separate holographic soliton pairs, based on the two-wave coupling and two-photon photorefractive effect in photorefractive crystals, holographic bright (dark) screening solitons are predicted in a series circuit consisting of double two-photon photorefractive crystal connected electronically by electrode in a chain with a voltage source. Each crystal can support a holographic screening soliton. The two solitons are known as a separate holographic two-photon screening soliton pair and there are three types: dark-dark, bright-bright and bright-dark. Numerical calculation results show that two solitons in a soliton pair can affect each other by light-induced current and coupling effects, which can affect the normalized spatial and the dynamical evolutions of solitons under the limit of the spatial extent of the optical beam is much less than the width of the crystal..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 419002 (2012)
Optical Design and Fabrication
Mid-Infrared Zoom Optical System with Ratio of 25
Zhou Hao, Liu Ying, and Sun Qiang
For 320 pixel×240 pixel cooled staring focal plane array detector, a mid-infrared zoom optical system with ratio of 25 is designed. The system consists of a zoom system and a re-imaging system. The zoom system consists of two small zoom lenses, which can realize large zoom ratio; the re-imaging system can satisfy For 320 pixel×240 pixel cooled staring focal plane array detector, a mid-infrared zoom optical system with ratio of 25 is designed. The system consists of a zoom system and a re-imaging system. The zoom system consists of two small zoom lenses, which can realize large zoom ratio; the re-imaging system can satisfy requirement of the cold shield efficiency, and the diameter of lens can be reduced because of it. The mid-infrared zoom optical system works in the range of 3.7～4.8 μm, it can realize 12～300 mm continuous zoom and satisfy requirement of 100% cold shield efficiency; F number of the system is 2.5. The zoom system has advantages such as a large zoom ratio, a large aperture, and short and smooth zoom paths..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 422001 (2012)
Design of High-Speed Photography Optical System for Air Bubbles in Water
Xie Zhengmao, Gao Limin, and He Junhua
For the purpose of study on diameter, velocity and concentration of air bubbles in water, an optical system of illumination and 3D photography based on high-speed imaging charge-coupled device is proposed. Based on Galileo structure with three cylindrical lens and semiconductor laser of wavelength 532 nm, a light sheetFor the purpose of study on diameter, velocity and concentration of air bubbles in water, an optical system of illumination and 3D photography based on high-speed imaging charge-coupled device is proposed. Based on Galileo structure with three cylindrical lens and semiconductor laser of wavelength 532 nm, a light sheet with thickness of 1.5 mm and width of 44 mm is designed. Three groups of imaging lens with magnification of 0.4×， 1× and 2.5×, having a uniform conjugate distance of 530 mm are designed. Each group relayed by collimated light includes frontal lens and focusing lens. A simple and reliable structure of 2D high-speed photography for the area of 60 mm×40 mm and 1D scan with length of 5 mm along the optical axis, is achieved by moving light sheet and frontal lens synchronously. The imaging quality of the optical system with magnification of 0.4×, 1× and 2.5× is evaluated, it shows that the modulation transfer function of 0.707ω has reached 0.58, 0.55 and 0.38 respectively at the spatial frequency of 50 lp/mm, as well as the diameter resolution of air bubbles in water has been from 10 μm to 450 μm..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 422002 (2012)
Analysis and Control of Narcissus Effect of Long-Wavelength Cooling Infrared Imaging System Based on Optical Defocusing
Liu Yang, An Xiaoqiang, Wang Qian, and Liu Pengpeng
At present the first-order parameter yni is used to quantify the focusing of retro-reflected rays on the detector plane, which causes narcissus effect. The shortage is that yni is not refrenced to the lens data and system data so it′s not useful to guide narcissus optimization. A new paramteroptical defocusing is definAt present the first-order parameter yni is used to quantify the focusing of retro-reflected rays on the detector plane, which causes narcissus effect. The shortage is that yni is not refrenced to the lens data and system data so it′s not useful to guide narcissus optimization. A new paramteroptical defocusing is defined to quantify the defocusing of retro-reflected rays, the relation between optical focusing and lens surface radius, aperture, position of intermediate image, focal length of lens before the surface and field of view is presented. Optical methods to minimize narcissus effect is summerized. The narcissus of a long-wavelength cooling infrared system is analysed with optical defocusing and the narcissus induced equivalent tempareture difference (NITD) is caculated. The major NITD contributing surfaces is optimised after which the NITD of zooming group drops by 50%, and that of fixed lens by 75%. The results demonstrate that optical defocusing can guide narcissus optimization effectively..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 422003 (2012)
Thermal-Optical Analysis for Optical Window of High-Altitude and High-Speed Aerial Camera
Shi Jinfeng, Wu Qingwen, Zhang Jianping, Huang Yong, Yang Xianwei, and Ding Yalin
Thermal-optical properties of optical window in complex environment are analyzed. From the perspective of considering thermal deformation of optical window, fused silica is selected for material of the window. In order to calculate temperature distribution of optical window within a work cycle, heat flux is assigned onThermal-optical properties of optical window in complex environment are analyzed. From the perspective of considering thermal deformation of optical window, fused silica is selected for material of the window. In order to calculate temperature distribution of optical window within a work cycle, heat flux is assigned on a scale of weight to outer surface of the window and radiation of the window is taken into account. Carrier of the window is an unmanned aerial vehicle with high-altitude and high-speed. Temperature of the window′s external surface increases sharply due to the aerodynamic heating that generated during the high-speed flight. Since thermal conductivity of fused silica is very small, a great axial temperature difference produces at the window. Heat deformation of the optical window is calculated when axial temperature difference is 55 ℃, 70 ℃ and 90 ℃, respectively. Radiuses of curvature of internal and external surface of optical window are obtained approximately by rules of its deformation. Optical path difference caused by the deformation of the surface shape and refractive index changes is analyzed. Zernike polynomial coefficients are fitted. Finally, the Zernike polynomials are put into the Code V to assess the optical properties of window glass. With the introduction of wave-front aberration, change of defocus is -0.114 mm and maximum decline value of modulation transfer function (MTF) is less than 0.01. The results show that the optical window meets optical performance requirements..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 422004 (2012)
Optical Devices
Study on Improving Light Emitting Efficiency of LED by Using Silver Nanodisk Array
Zhang Zhenming, Li Kang, Kong Fanmin, and Gao Hui
In order to improve the light emitting efficiency of GaN-based blue LED, a novel LED model, which has a layer of silver nanodisk array embedded above the quantum well, is designed. The rates of spontaneous emission change and light extraction efficiencies of the models with various geometric parameters are calculated bIn order to improve the light emitting efficiency of GaN-based blue LED, a novel LED model, which has a layer of silver nanodisk array embedded above the quantum well, is designed. The rates of spontaneous emission change and light extraction efficiencies of the models with various geometric parameters are calculated by using finite-difference time-domain method. With the analysis for near field distribution of active region (AR) and far field directivity of LED, we theoretically explain the influence of surface plasmon polaritons (SPP) formed on silver nanodisks on the improvement of LED performance. This model could contribute to the coupling between SPP and AR, leading to the enhancement of spontaneous emission of AR. Besides, due to the compensation for wave vector of SPP by lattice vector of silver nanodisk array, the localized SPP could radiate to space and light extraction efficiency of LED could be improved. Optimization results show that on the condition that the diameter of nanodisk is set to 120 nm and its thickness is chosen as 30 nm, the spontaneous emission is enhanced by 3.6 times compared to that of the conventional LED. Furthermore, as the nanodisks are arranged to the array with triangular lattice and the lattice constant is 220 nm, light extraction efficiency gets 2.5 times enhancement. These results provide a theoretical reference on the practical design and optimization of highly efficient GaN-based LED..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 423001 (2012)
Quantum Optics
Local Modulation of Electromagnetic Induction Transparent Spectrum by Microwave Field
Zhang Feng, and Hou Bangpin
When the ground state of the coupling transition in a Λ-type atom is coupled to two hyperfine levels of a lower state by two weak coherent fields, two sharp and high-contrast absorption lines induced by the microwave fields split the single electromagnetically induced transparent spectrum into three parts. The triple eWhen the ground state of the coupling transition in a Λ-type atom is coupled to two hyperfine levels of a lower state by two weak coherent fields, two sharp and high-contrast absorption lines induced by the microwave fields split the single electromagnetically induced transparent spectrum into three parts. The triple electromagnetically induced transparent spectrum can be locally modulated by adjusting the strength of microwave field and its detuning. This will be useful in multi-channel optical communication and controllable manipulation of atomic system..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 427001 (2012)
Study on the Quantum Properties of Chirped Biphotons with a Pulse Pump
Li Baihong, Yan Zhengxin, Zhang Tao, and Li Yongfang
Based on nonlinear optics and quantum theory, the process of type-II spontaneous parametric down-conversion pumped by a pulsed laser is researched in quasi-phase-matched nonlinear crystal that has a linearly chirped wave vector. The influence of the pump band-width and chirp coefficient on the properties of chirped bipBased on nonlinear optics and quantum theory, the process of type-II spontaneous parametric down-conversion pumped by a pulsed laser is researched in quasi-phase-matched nonlinear crystal that has a linearly chirped wave vector. The influence of the pump band-width and chirp coefficient on the properties of chirped biphotons and Hong-Ou-Mandel (HOM) quantum interference are analyzed. It is shown that with the increase of the pump band-width, indistinguishability of biphotons and quantum interference visibility are diminished while chirp coefficient is a constant; In a constant pump band-width, as the chirp coefficient is increased, the bandwidth of chirped biphotons are also increased and HOM quantum interference dip becomes narrower, thus yields enhanced the interference resolution and quantum interference visibility. Ultrabroadband biphotons and ultranarrow HOM dip are generated in theory..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 427002 (2012)
Remote Sensing and Sensors
Analysis of Effects of Line Vibration on Imaging Quality of Synthetic Aperture Ladar
Hong Guanglie, and Guo Liang
Synthetic aperture ladar (SAL), whose carrier is laser, makes use of synthetic aperture processing to improve the resolution of images. Vibration from the platform of SAL will affect on the imaging quality of SAL. The effects of line vibration on the imaging quality are analyzed. Firstly, instantaneous range of synthetSynthetic aperture ladar (SAL), whose carrier is laser, makes use of synthetic aperture processing to improve the resolution of images. Vibration from the platform of SAL will affect on the imaging quality of SAL. The effects of line vibration on the imaging quality are analyzed. Firstly, instantaneous range of synthetic aperture ladar with vibration is unwraped and the effect of vibration is divided into two classes, the along-track and the cross-track one. After analysis, the effect of the along-track vibration can be ignored while the cross-track one cannot. And the vibration only affects the azimuth direction result in defocusing of the azimuth and the imaging quality. Finally, the simulations prove the validity of the analysis..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 428001 (2012)
Scattering
Extinction Characteristics of Soot-Silicate Mixed Agglomerates in Random Distribution
Lei Chengxin, Wu Zhensen, and Feng Dongtai
Based on fractal theory, Monte Carlo method is used to simulate the structures of mixed agglomerates in random distribution. The equivalent complex refractive index of internal mixture of agglomerates containing different volume fractions of black carbon particles is obtained by Bruggeman effective medium theory. The eBased on fractal theory, Monte Carlo method is used to simulate the structures of mixed agglomerates in random distribution. The equivalent complex refractive index of internal mixture of agglomerates containing different volume fractions of black carbon particles is obtained by Bruggeman effective medium theory. The extinction characteristic quantities including the absorption, scattering and extinction efficiency factor of mixed agglomerates in internal and external mixing states are calculated based on the discrete dipole approximation (DDA) method. Meanwhile, the influence of mixture patterns, volume content, solar radiative wavelength, the monomer diameters, and the number of monomers on the radiative properties of mixed agglomerates is mainly discussed. Comparison of the numerical results obtained by the DDA method with T matrix method shows that the numerical results obtained by two numerical methods are very similar. The results show that the scattering efficiency factor is substantially sensitive to mixing patterns, the extinction efficiency factor is weaker, while the absorption efficiency factor is not sensitive. The influence of mixing patterns on the scattering and extinction efficiency factor is becoming more obvious with the increase of the size of mixed agglomerates. The absorption, scattering and extinction efficiency factor of mixed agglomerates in internal and external mixing states increase monotonically with the increasing of the volume fraction of black carbon, and the increase varies with the size parameters of mixed agglomerates..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 429001 (2012)
Investigation of Scattering for a Uniformly Anisotropic Dielectric Sphere
Li Yingle, Li Jin, Wang Mingjun, and Dong Qunfeng
The uniformly anisotropic medium is reconstructed as a lossless isotropic one in electricity, and its scattering cross section is developed. In primary coordinate system, the scattering cross section of a lossless anisotropic dielectric sphere is obtained. It is found that when the anisotropic medium is an isotropic onThe uniformly anisotropic medium is reconstructed as a lossless isotropic one in electricity, and its scattering cross section is developed. In primary coordinate system, the scattering cross section of a lossless anisotropic dielectric sphere is obtained. It is found that when the anisotropic medium is an isotropic one, the scattering cross section of this sphere is in agreement with the famous Mie theory, so the validity of the gaining result is tested. Simulations show that the scattering cross section is proportional to the element of the dielectric constant tensor and varies with the incident wave direction. For the scattering of a complex anisotropic medium target, this result provides an evaluation criterion..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 429002 (2012)
Research on Electron Trapping by Four Intense Laser Beams
Zhang Shaoyin, Wang Jiaxiang, and Ai Shutao
Based on the basic principle of nonlinear strong-field effect induced by the free electron interaction with intense laser fields, a scheme to trap the high-energy electrons by four propagating laser beams has been proposed to improve the total probability of nonlinear process by prolonging the interaction time of free Based on the basic principle of nonlinear strong-field effect induced by the free electron interaction with intense laser fields, a scheme to trap the high-energy electrons by four propagating laser beams has been proposed to improve the total probability of nonlinear process by prolonging the interaction time of free electron and strong field. The mechanism is based upon the electron scattering by intense laser beams. The numerical simulation results show that the interaction time between electrons trapped and central optical field has been prolonged..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 429003 (2012)
Spectroscopy
Dual-Channel, Co-axial, Focusing X-Ray Crystal Spectrograph
Yang Qingguo, Li Zeren, Chen Guanghua, Huang Xianbin, Cai Hongchun, Li Jing, and Xiao Shali
A dual-channel, co-axial, focusing X-ray crystal spectrograph is developed for spectroscopy of the Z-pinch plasmas. The spectrograph uses a uniform-dispersed crystal (the linear dispersion is a constant) and a spherical crystal as the dispersion element and a double-film box as the detector to achieve the simultaneous A dual-channel, co-axial, focusing X-ray crystal spectrograph is developed for spectroscopy of the Z-pinch plasmas. The spectrograph uses a uniform-dispersed crystal (the linear dispersion is a constant) and a spherical crystal as the dispersion element and a double-film box as the detector to achieve the simultaneous measurement of the time-integrated spectra of the plasmas in almost the same spectral range. The experiment is carried out on the “Yang” accelerator at Chinese Academy of Engineering Physics (CAPE) and the H-like and He-like emission lines of Al Z-pinch plasmas are obtained. The results show that the linear dispersion obtained by the uniform-dispersed channel, is agree with the designed value very well due to satisfying the uniform dispersion condition, and the maximum relative error is only 3.48%. Compared with the spherical crystal channel, it has the advantage of easiness and veracity for spectra identification and processing and it may be useful for the complicated spectra identification and analysis..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 430001 (2012)
Extreme Ultraviolet and Visible Emission Spectroscopic Characterization of CO2 Laser Produced Tin Plasma for Lithography
Wu Tao, Wang Xinbing, Tang Jian, Wang Shaoyi, Rao Zhiming, Yang Chenguang, and Lu Hong
The experiments of laser-produced tin plasma are carried out using a CO2 laser with the energy of 400 mJ of each pulse and the full width at half maximum (FWHM) of 75 ns. The temporal evolution of visible emission spectrum are measured using a spectrograph coupled with an intensified charge-coupled device (ICCD) in vacThe experiments of laser-produced tin plasma are carried out using a CO2 laser with the energy of 400 mJ of each pulse and the full width at half maximum (FWHM) of 75 ns. The temporal evolution of visible emission spectrum are measured using a spectrograph coupled with an intensified charge-coupled device (ICCD) in vacuum. The plasma electron temperature is inferred by the Bolzmann plot method from five singly ionized Sn emission lines, while electron density measurements are made using Stark broadening method by assuming the conditions of local thermodynamic equilibrium. Extreme ultraviolet (EUV) spectral measurement is made throughout the wavelength region of 6.5~16.8 nm using a grazing incidence flat-field grating spectrometer coupled with an X-ray CCD for the detection of time-integrated spectrum. The results show that optical emission spectrum is mainly the continuous spectrum at the early stage of plasma expansion (within the first 100 ns) and the continuous spectrum weakens gradually while the line spectrum becomes dominating. Electron temperature is measured in the range of 2.3~0.5 eV, and electron density is measured in the range of 7.6×1017~1.2×1016 cm-3, as the time delay is varied from 0.1 to 2.0 μs. Both the electron temperature and density decrease fast at early delay time and slowly decrease at later delay time. The extreme ultraviolet emission measurement of laser-produced-tin plasma shows that the peak of the EUV spectrum is located at 13.5 nm and the FWHM of the unresolved transition arrays is 1.1 nm..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 430002 (2012)
Effect of Variable Optical Path Length on the Accuracy of the Model in Noninvasive Biochemical Detection by NIR Spectrum
Ding Haiquan, Lu Qipeng, and Chen Xingdan
For noninvasive quantitative analysis of blood biochemical components, near infrared (NIR) subtracted blood volume spectrometry is applied. However, the optical path lengths corresponding to in vivo blood spectra obtained are uncertain. In order to study the effect of optical path length difference on the prediction acFor noninvasive quantitative analysis of blood biochemical components, near infrared (NIR) subtracted blood volume spectrometry is applied. However, the optical path lengths corresponding to in vivo blood spectra obtained are uncertain. In order to study the effect of optical path length difference on the prediction accuracy of calibration model, 30 serum samples are simulated. A variable path-length cell is used to produce optical path difference, and spectra of two sample sets, with equal and different path-lengths respectively, are measured by Nicolet 6700 Fourier transform infrared (FT-IR) spectrometer. As to serum albumin, the calibration accuracies of the two groups are compared. The results show that the samples with uncertain optical path would reduce the calibration accuracy, as the root mean square error of cross validation (RMSECV) of the model increases from 110.0 mg/dL to 156.0 mg/dL. By applying multiplicative scatter correction, RMSECV of the uncertain optical path set reduces to 98.1 mg/L. It indicates that appropriate pretreatment method can effectively correct the error of spectrum caused by uncertain optical path length, thus improve the accuracy of the prediction model..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 430003 (2012)
Data Preprocessing of Broad-Spectrum Tunable-Diode-Laser Absorption Spectroscopy
Gao Nan, Du Zhenhui, Qi Rubin, Li Jinyi, Zhou Tao, Zhou Kui, and Wang Yan
The diode-laser absorption spectroscopy has been tuned with fast speed and wide wavelength range by temperature scanning. The system original data does not suit for traditional processing and operation, therefore the proper data preprocessing is the basis of the follow-up operation. The original data is processed accorThe diode-laser absorption spectroscopy has been tuned with fast speed and wide wavelength range by temperature scanning. The system original data does not suit for traditional processing and operation, therefore the proper data preprocessing is the basis of the follow-up operation. The original data is processed according to the characteristics of temperature tuning signal. The temperature detection noise in wavelength sequence is removed by Savitzky-Golay filter, then cubic spline interpolation is applied to obtain amplitude sequence with fixed wavelength position for follow-up operation. The result sequence, which has both information of amplitude and wavelength as the same starting point and fixed wavelength position, not only has 6 times higher signal-to-noise ratio than that of original signal by multi periods averaging, but also makes the comparison and evaluation between different signals possible. The consistent wavelength resolution ensures the precision of lineshape detection and decreases the frequency bandwidth of absorption peaks. The experimental results indicate that the data preprocessing provided is beneficial to follow-up operation, calculation and evaluation in such systems..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 430004 (2012)
Fluorescent Emission of Erythrocyte Suspension with Time-Resolved Fluorescence Spectrometer
Han Caiqin, Duan Peitong, Liu Ying, Luo Xiaosen, and Ni Xiaowu
The fluorescence spectrum of erythrocyte suspension irradiated by laser is studied experimentally. The decay processes of fluorescence intensity are monitored at the emission band with different fluorescence peaks. The results show that when erythrocyte suspension is irradiated by laser with wavelength of 407 nm, thereThe fluorescence spectrum of erythrocyte suspension irradiated by laser is studied experimentally. The decay processes of fluorescence intensity are monitored at the emission band with different fluorescence peaks. The results show that when erythrocyte suspension is irradiated by laser with wavelength of 407 nm, there are three fluorescence peaks locate at 596, 628 and 692 nm, respectively. The average fluorescence lifetimes of each decay process in turn are 1.97, 13.31 and 14.58 ns. The total absorptivity and total fluorescence counts are expressed based on the theory of additive property of absorptivity and fluorescence intensity. By theoretical analysis, the variations of relative concentration and relative fluorescence intensity at different peak have been obtained in erythrocyte suspension, which are protoporphyrin, zinc protoporphyrin and other free substances. The change of fluorescence intensity and average lifetime in different fluorescence peaks are illuminated..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 430005 (2012)
Vision, Color, and Visual Optics
Human Eye Neural Contrast Sensitivity Function Measurement with Wave-Front Technology
Zhao Haoxin, Dai Yun, Zhou Yifeng, and Zhang Yudong
Equipment is established for measuring neural contrast sensitivity functions (NCSF) of human eyes. The contrast sensitivity function (CSF) of whole eye and modulation transfer function of optical system of the eye can be measured synchronously, and the NSCF can be calculated from CSF and modulation transfer function coEquipment is established for measuring neural contrast sensitivity functions (NCSF) of human eyes. The contrast sensitivity function (CSF) of whole eye and modulation transfer function of optical system of the eye can be measured synchronously, and the NSCF can be calculated from CSF and modulation transfer function conveniently. Compared with achieving NSCF by measuring total-vision CSF and modulation transfer function respectively by two equipments, this method considers the dynamic character of human aberrations, and simplifies the measuring course. Compared with achieving NSCF by conventional laser interference, this method avoids the disadvantages of coherent noise and laser speckle, and can achieve NSCF of different luminance and different wavelengths by changing the luminance and color of visual target. NSCF of four normal eyes are measured with green visual target, and the results show that NSCF are variable in subjects, and the corresponding spatial frequency of NSCF peak value is higher than that of spatial CSF of whole eye..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 433001 (2012)
X-Ray Optics
Investigation on X-Ray Micro-Computed Tomography Suitable for Organic Compound Samples Based on Modifed Bronnikov Algorithm
Liu Huiqiang, Wang Yudan, Ren Yuqi, Xue Yanling, He You, Guo Han, and Xiao Tiqiao
Organic compound samples are characterized by mixed phase and amplitude, such as most polymer combination materials and biological soft tissues made from low-atomic-number materials etc, which are very hard to obtain higher resolution of density by conventional absorption computerized tomography (CT) or phase retrival Organic compound samples are characterized by mixed phase and amplitude, such as most polymer combination materials and biological soft tissues made from low-atomic-number materials etc, which are very hard to obtain higher resolution of density by conventional absorption computerized tomography (CT) or phase retrival algorithm of pure-phase object. The X-ray in-line phase contrast CT technology based on the modified Bronnikov algorithm has been utilized for the experimental investigation of high polymer mixed materials and medical samples. The experimental results show that the proposed method can realize the non-destructive imaging and precise measurement of polymer combination samples by distinguishing those electronic densities of different parts clearly. In addition, the results demonstrate the feasibility of three-dimensional measurement of medical samples with porosity by supplying with a valid threshold. The method has good potential application in material science, especially in polymers and foam porous materials, and three-dimensional nondestructive imaging of biomedicine due to the advantage of low radiation dose..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 32, Issue 4, 434001 (2012)
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