Contents
2014
Volume: 34 Issue 7
49 Article(s)
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Atmospheric Optics and Oceanic Optics
Neutral Points Recognition Based on the Atmospheric Polarization Pattern′s Global Characteristics
Wang Ziqian, Fan Zhiguo, Jin Haihong, and Zhang Xudong
Neutral points are one of important distribution characteristics of the atmospheric polarization pattern, which have important value on polarotactic navigation, atmospheric environmental monitoring, remote sensing, et al.. Based on the analysis of the degree of polarization′s and the neural line′s distribution characteNeutral points are one of important distribution characteristics of the atmospheric polarization pattern, which have important value on polarotactic navigation, atmospheric environmental monitoring, remote sensing, et al.. Based on the analysis of the degree of polarization′s and the neural line′s distribution characteristics, two recognition methods of neutral points are proposed. The experimental results show that, both of these methods can recognize the neutral points from the real atmospheric polarization pattern automatically and precisely. The recognition method based on the intersection features of the neutral lines has better algorithm performance. Meanwhile, the recognition method based on the distribution characteristics of the degree of polarization has better algorithm robustness, and has much better algorithm performance than the other method at the midday. By the integrated application of two methods, the accuracy of the neutral points recognition can be further improved..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 701001 (2014)
Influence of Static Aberrations on the Accuracy of Cross Spectrum Phase Reconstruction and the Compensated Method
Zhong Libo, Tian Yu, and Rao Changhui
Speckle image reconstruction can effectively remove the influence of the atmospheric turbulence and obtain the diffraction limited images of the object. However, the static aberrations of the system can destroy the statistical information of the wavefronts and decrease the accuracy of the Fourier phase reconstruction. Speckle image reconstruction can effectively remove the influence of the atmospheric turbulence and obtain the diffraction limited images of the object. However, the static aberrations of the system can destroy the statistical information of the wavefronts and decrease the accuracy of the Fourier phase reconstruction. It shows that among defocus, astigmatism, coma and spherical aberration, only coma has residual phase on the reconstruction in ideal case. By dividing the pupil into several sub-apertures with Fried parameter as the diameter, the influence of the static aberration on the phases of the cross spectrum transfer function is analyzed. The result shows that by choosing the direction of the shift frequency in the cross spectrum transfer function, aberration balancing can be used to reduce the influence of the static aberration and improve the accuracy of the reconstruction. The simulations show desired effects of the balancing on the spherical aberration and defocus, astigmatism and defocus..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 701002 (2014)
Atomic and Molecular Physics
Angular Distribution of Ejected Electrons from Eu 4f76p1/28s Auto-Ionizing State Studied by Velocity Mapping Imaging Technique
Dong Cheng, Shen Li, Yang Jinhong, and Dai Changjian
The angular distribution of the electron ejected from Eu atom 4f76p1/28s auto-ionizing state, whose energy range covers from 60600.0 cm-1 to 61860.2cm-1, has been investigated in use of the velocity mapping imaging technique. Eu atom is stepwise excited from the 4f76s2 8S7/2 ground state to the 4f76s8s 8S7/2 Rydberg stThe angular distribution of the electron ejected from Eu atom 4f76p1/28s auto-ionizing state, whose energy range covers from 60600.0 cm-1 to 61860.2cm-1, has been investigated in use of the velocity mapping imaging technique. Eu atom is stepwise excited from the 4f76s2 8S7/2 ground state to the 4f76s8s 8S7/2 Rydberg state through the 4f76s6p 6P5/2 intermediate state, then excited to the 4f76p1/2(J=3)8s and 4f76p1/2(J=4)8s auto-ionizing states further by using the three steps isolated-core-excitation method. The value of the total angular momentum is calculated by the excitation scheme and the selection rule, the energy range and properties are deduced from the energy, angular momentum and parity conservation in auto-ionization process. The ejected electron, which is the production of the auto-ionization process, is focused and imaged by the electron lens. The kinetic energy of it is resolved by the position sensitive detector, and by using the velocity mapping imaging technique, mathematical transformation and calculation for ejected electron angular distribution is carried out. Simultaneously, by tuning the wavelength of the third dye laser, the propensity of the angular distribution and the anisotropy parameters following the variation of the photon energy has been obtained, and the physical essence has been discussed..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 702001 (2014)
Fiber Optics and Optical Communications
New Microwave Frequency Dissemination Method over Optical Fiber Based on the Phase Fluctuation Compensated at Remote Sites
Li Delong, Lu Lin, Zhang Baofu, Li Xiaoya, and Teng Yichao
In order to study the performance of microwave frequency transfer based on fiber link, a novel ultra-stable radio frequency dissemination system over optical fiber is proposed. The system utilizes a Faraday rotator mirror to reflect the optical signal back to remote sites, where the phase fluctuation introduced by tempIn order to study the performance of microwave frequency transfer based on fiber link, a novel ultra-stable radio frequency dissemination system over optical fiber is proposed. The system utilizes a Faraday rotator mirror to reflect the optical signal back to remote sites, where the phase fluctuation introduced by temperature and pressure changes is counteracted by the frequency multiplier mixer circuit at remote sites. Its validity is tested through simulation and experiment. The transmission of 1 GHz signals over 25.2 km optical fiber is experimentally demonstrated, where relative stability of 2×10-12 s-1 and 6×10-17 d-1 is obtained. The main advantages of the proposed system are that the local sites structure is simplified, and the signal conversion of optical-electronic-optical and the phase fluctuation measurement and compensation systems can be removed at local sites. In addition, the fiber-induced phase noises can be suppressed by three orders of magnitude in the long-term..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 706001 (2014)
Effect for Modulation Rate of Pulsed Fiber Laser on Pulse Position Modulation
Ren Xin, Li Hongzuo, Wang Yan, and Hao Ziqiang
The limitation of low repetition rate for pulsed fiber laser makes data transmission rate lower, which has a serious impact on its application in the field of communications. In order to improve its performance and make it better applied to the field of communications, the pulsed fiber laser is modulated by three pulseThe limitation of low repetition rate for pulsed fiber laser makes data transmission rate lower, which has a serious impact on its application in the field of communications. In order to improve its performance and make it better applied to the field of communications, the pulsed fiber laser is modulated by three pulse position modulation (PPM) modulations and its impact on performance are studied experimentally. By changing the modulaton digits of three PPM modulations method, the influence of time slot width on modulation rate of pulsed fiber laser system is investigated, and the effect of the modulations on output power bit error rate is researched. The results show that the level pulse pastion modulation (L-PPM) modulation method is most suitable for pulsed fiber lasers and the modulation rate can be enhanced to 1.387 Mbit/s under the repetition rate of 200 kHz. The findings will be benefit for pulsed fiber laser applications in communications..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 706002 (2014)
Multi-User Communication System Based on Photonic Generation of Coded Ultrawideband Signal
Liu Shuang, Qian Zuping, Wang Rong, and Pu Tao
A multi-user communication system based on photonic generation of coded ultrawideband (UWB) signal is proposed and demonstrated. The optical fiber is used for the transmission of the coded UWB signal generated by an optical method at the transmitter. The receiver calculates the cross correlation of the coded UWB signalA multi-user communication system based on photonic generation of coded ultrawideband (UWB) signal is proposed and demonstrated. The optical fiber is used for the transmission of the coded UWB signal generated by an optical method at the transmitter. The receiver calculates the cross correlation of the coded UWB signals and the signature codes to get the user information and data information. The proposed system has advantages such as simple expansion, easy receiving, long distance transmission, and tunability. The core component in the system is the optical frequency discriminator combined by multi-channel fiber Bragg grating (FBG) filter and dispersion fiber. Different chip-combinations in the signals represent different users. It needs only to tune the wavelength of the lasers for user-switching in this system. The coded UWB signals for different users are experimentally generated, and the user information and data information are recovered correctly. The proposed system realizes the whole communication process..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 706003 (2014)
Power Allocation Method for Reducing Nonlinearity Clipping Distortion in Asymmetrically Clipped Optical Orthogonal Frequency Division Multiplexing Based Visible Light Communication
Lu Qingfeng, Ji Xinsheng, Huang Kaizhi, and Luo Wenyu
To handle the significant light emitting diode (LED) nonlinearity clipping distortion problem in asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) based visible light communication systems, an optimal power allocation method for reducing the clipping distortion is proposed. The LED noTo handle the significant light emitting diode (LED) nonlinearity clipping distortion problem in asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) based visible light communication systems, an optimal power allocation method for reducing the clipping distortion is proposed. The LED nonlinear clipping distortion of the system is analyzed based on the clipping process model that original signal directly addes nonlinear clipping distortion components. The effective signal to noise ratio (SNR) is defined to measure the clipping distortion, and the clipping distortion analysis is converted into SNR analysis. Finally, the optimal bias signal and ACO-OFDM signal power allocation under optical power constraints based on the principle of effective SNR optimum are proposed. Simulation results show that the channel noise dominants at low channel SNR value while clipping distortion dominates at high channel SNR value. Bit error rate (BER) is greater than 10-2 even the channel SNR value beyond 40 dB if the bias power is selected as the minimum output power limit value of LED without considering, while optimal power allocation can effectively reduce the LED nonlinear clipping distortion to improve the BER performance. Channel SNR values of 24 dB and 27 dB are enough to insure that BER is below 10-3 under the optical power constraints of 200 mW and 250 mW, respectively..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 706004 (2014)
Image Processing
Nonlinear Double Images Encryption Based on Double Random Phase Encoding
Chen Yixiang, and Wang Xiaogang
A new method of image encryption and decryption is proposed, where the encryption process is different from the decryption and the encryption keys are also different from the decryption keys. The encryption is nonlinear for the sake of security enhancement while the decryption is linear. Two original images are combineA new method of image encryption and decryption is proposed, where the encryption process is different from the decryption and the encryption keys are also different from the decryption keys. The encryption is nonlinear for the sake of security enhancement while the decryption is linear. Two original images are combined as a complex amplitude image and encrypted based on classical double random phase encoding (DRPE) and phase-truncated Fourier transform (PTFT). Two private keys are generated in the encryption process and the decryption can be performed by the double random phase encoding scheme. Compared with the classical DRPE and PTFT-based single-image encryption, the proposed method is more secure and has resistance against on the specific attack that is based on two-step amplitude-phase retrieval algorithm. Numerical simulations are carried out to demonstrate the validity and security of the proposed scheme..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 710001 (2014)
Underwater Imaging and Real-Time Optical Image Processing under Illumination by Light Sources with Different Wavelengths
Nie Ying, and He Zhiyi
To improve the underwater imaging quality under the complex underwater imaging environment, different water environments are simulated by adding the blue-green ink and milk for the absorption and scattering effects respectively, and light sources with different wavelengths are employed for illumination. To eliminate orTo improve the underwater imaging quality under the complex underwater imaging environment, different water environments are simulated by adding the blue-green ink and milk for the absorption and scattering effects respectively, and light sources with different wavelengths are employed for illumination. To eliminate or alleviate the effect of absorption and scattering, an optical image processing technique is proposed after analyzing the collected characteristics of images with different light sources. The experiments show that the blue-green light has better transmission to overcome the water absorption and the red light with longer wavelength exhibits clearer illumination to alleviate the scattering influence and obtain target image information. The scattering noise can be removed with the collected differential image grey-scale value of the red light and blue-green light. The image processing technique in both Windows and Android systems is demonstrated, achieving a high performance. Compared with the unsharp mask (USM) sharpening algorithms, it has the advantages of simpler computation and good real-time performance..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 710002 (2014)
Two-Dimensional Imaging Experiment of Down-Looking Synthetic Aperture Ladar under Simulated Far-Field Conditions
Luan Zhu, Sun Jianfeng, Zhi Yanan, Zhou Yu, Wang Lijuan, and Liu Liren
This paper gives experimentally the two-dimensional imaging results of a synthetic aperture ladar for an array target under simulated far-field conditions with an optical collimator of 10 m focal length. The imaging resolution of 1 mm is observed.This paper gives experimentally the two-dimensional imaging results of a synthetic aperture ladar for an array target under simulated far-field conditions with an optical collimator of 10 m focal length. The imaging resolution of 1 mm is observed..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 710003 (2014)
Imaging Systems
Analysis and Verification of Influence of Sinusoidal Vibration on Imaging of Aerial Camera
Sun Chongshang, Ding Yalin, Wang Dejiang, Huang Houtian, Tian Dapeng, and Yao Yuan
The imaging resolution of aerial camera is limited by vibration during exposure. Dynamic modulation transfer function is used to study the impact of the sinusoidal vibration on imaging. Modulation transfer function (MTF) of high-frequency and low-frequency vibrations are analyzed through the calculation method based onThe imaging resolution of aerial camera is limited by vibration during exposure. Dynamic modulation transfer function is used to study the impact of the sinusoidal vibration on imaging. Modulation transfer function (MTF) of high-frequency and low-frequency vibrations are analyzed through the calculation method based on spatial domain. When exposure time is not equal to an integer multiples of the vibration cycle, the impact of high-frequency vibrations on image quality is also random, but the randomness is less apparent than low-frequency vibration. The fast steering mirror is used to simulate vibrations, complementary metal oxide semiconductor (CMOS) sensor is used to capture images, wavelet transform is used to extract high frequency information. Exposure time is set to 20 ms, when the vibration frequency is 50 Hz, the fluctuation range of high-frequency information is only 0.0582×104, which can be ignored compared with the total number of high-frequency information. When the vibration frequency is 15 Hz, the fluctuation range is 0.6233×104 and randomness is obvious. But when the vibration frequency is 65 Hz, the fluctuation range is 0.1245×104 and randomness is not obvious. By the correspondence between high-frequency information and MTF, the correctness of theoretical analysis is proved. On the basis of theoretical analysis and experiments, the general conclusion of sinusoidal vibration′s effect on imaging is summed. This conclusion can not only be used to analyze the design of the imaging system structure, but also can be applied to image deblurring..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 711001 (2014)
Three Dimensional Flash Imaging Ladar Range Estimation Via Parameterized Blind Deconvolution
Zhao Wen, Han Shaokun, Kang Yanyan, Xia Wenze, and Li Baowei
Multi-surface ranging with the use of three dimensional (3D) flash ladar can be useful in accurately discriminating camouflaged targets of interest. In order to estimate multiple surfaces in 3D flash imaging ladar well and truly, a multiple surfaces′ range estimating algorithm in 3D flash imaging ladar via expectation Multi-surface ranging with the use of three dimensional (3D) flash ladar can be useful in accurately discriminating camouflaged targets of interest. In order to estimate multiple surfaces in 3D flash imaging ladar well and truly, a multiple surfaces′ range estimating algorithm in 3D flash imaging ladar via expectation maximization (EM) is proposed. This algorithm can estimate the point spread function of imaging ladar and the target range information simultaneously. Simulation results show that the multiple surfaces′ range estimating algorithm can improve range estimation over traditional mixed Gaussian matching and Wiener filter by up to 70% and 40% respectively..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 711002 (2014)
Imaging Crosstalk Analyzing and Suppressing for Multi-TDICCD Mosaic Remote Sensing Camera
Zhang Guixiang, Zheng Liangliang, He Xiaojun, Qu Hongsong, and Jin Guang
In order to solve the imaging crosstalk between charge coupled device (CCD) channels and improve the signal-to-noise ratio (SNR) and imaging quality of multi time delay integration (TDI) charge coupled device mosaic remote sensing camera, a mathematical model of imaging crosstalk is established based on Fourier series In order to solve the imaging crosstalk between charge coupled device (CCD) channels and improve the signal-to-noise ratio (SNR) and imaging quality of multi time delay integration (TDI) charge coupled device mosaic remote sensing camera, a mathematical model of imaging crosstalk is established based on Fourier series analysis of the periodic signal. According to the results of mathematical analysis, the root cause of multi-TDICCD imaging crosstalk between different channels is proposed to be the unsynchronized TDICCD imaging circuit working, which causes high-frequency disturbance on the power ground plane and eventually affects the effective video signals acquisition of neighboring TDICCD. Referring to practical project, isolated CCD power supply, shared unified system clock and other methods are adopted to optimize multi-TDICCD imaging circuit system to suppress the occurrence of imaging crosstalk. The imaging quality and SNR are tested after improvement. Experimental results indicate that the adopted methods which can prevent the occurrence on imaging crosstalk between different CCD channels are effective, and the SNR is improved significantly. When the radiance is 42.6 W/(m2·Sr), the camera SNR increases 18.85 dB, reaching to 50.42 dB. The image quality of outside scene imaging is also improved significantly, which can meet the requirements of practical engineering of TDICCD remote sensing camera..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 711003 (2014)
Talbot Effect in Linear Canonical Transformation
Sun Qiongge, Ma Jinpeng, Yang Yu, Li Chen, Liu Zhengjun, and Liu Shutian
It demonstrates that the periodic function after the linear canonical transform (LCT) still results in a periodic function. When certain conditions are satisfied, the periodic functions are still periodic functions, which is Talbot effect in LCT. The Talbot effect in LCT is theoretically proved, and their self-image coIt demonstrates that the periodic function after the linear canonical transform (LCT) still results in a periodic function. When certain conditions are satisfied, the periodic functions are still periodic functions, which is Talbot effect in LCT. The Talbot effect in LCT is theoretically proved, and their self-image conditions are obtained. The conditions of Talbot effect in the special forms of the LCT (such as Fresnel diffraction, fractional Fourier transform and Gyrator transform) are also presented. The self-image condition of Gyrator transform is obtained and proved by numerical simulation, which suggests the Talbot effect is extended to the domain of LCT..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 711004 (2014)
Instrumentation, Measurement and Metrology
Measuring Error of Phase Modulation Laser Doppler Shift Measuring Method
Du Jun, Qu Yancheng, Zhao Weijiang, Geng Lijie, Liu Chuang, Zhang Ruiliang, and Chen Zhenlei
By investigating distribution regularity of measuring error theoretically and experimentally, this paper builds measuring error mode of phase modulation laser Doppler shift measuring method based on its operating principle, which can be used to quantitative analyze and optimization design of Doppler shift measuring metBy investigating distribution regularity of measuring error theoretically and experimentally, this paper builds measuring error mode of phase modulation laser Doppler shift measuring method based on its operating principle, which can be used to quantitative analyze and optimization design of Doppler shift measuring method for acquiring optimum measuring results in practical application. This error mode is utilized to theoretically investigate the influence of phase modulation depth and frequency on its frequency shift measuring accuracy and so on. It is found that measuring accuracy can reach the maximum when phase modulation frequency is equal to 0.63 times of full width of half maximum of Fabry-Perot interferometer transmission curve and phase modulation depth is 1.08..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 712001 (2014)
Analysis for Influence of Element Deviation to DOLP Measured by Spatial Modulating Spectropolarimeter
Liu Qiang, Li Shuang, and Gong Ping
Matrix of deviation for spatial modulating spectropolarimeter that composed of quarter wave plate, double birefringent wedges and polarizer is educed. Magnitude of influence of element deviation to emergent light is figured out, with that the modulative phase retardance is equal to 0 or 0.5π. It is presented that, whenMatrix of deviation for spatial modulating spectropolarimeter that composed of quarter wave plate, double birefringent wedges and polarizer is educed. Magnitude of influence of element deviation to emergent light is figured out, with that the modulative phase retardance is equal to 0 or 0.5π. It is presented that, when retardant phase is 0.5π and its deviation is 0.02π, the modulating coefficient of Stokes parameter V is 0.0314. And when V=0.2, it will cause that the probability of restraint for measuring deviation of Stokes parameter U under 0.45%, is decreased from about 80% to 6%, compare with V=0. By simulation analysis, it is presented that the relative measuring deviation of degree of linear polarization (DOLP) is less than 0.5% without instrument polarization calibrating, when all the element deviations are equal to the positive maximum in their span of deviation, and the Stokes parameter V≤0.04..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 712002 (2014)
A Fast Method for Calculating the Thermal Effect in Projection Objective Lenses
Luo Cong, and Gong Yan
A new method is mentioned which can be used to simulate the thermal effect in the projection objective lens with fast speed. The method improves the solving period by separating the all solution to two steps: the first step is to obtain the transfer matrix between intensity distribution of the incident beam and thermalA new method is mentioned which can be used to simulate the thermal effect in the projection objective lens with fast speed. The method improves the solving period by separating the all solution to two steps: the first step is to obtain the transfer matrix between intensity distribution of the incident beam and thermal effect (including lens temperature and surface deformation). The second step is to express the intensity distribution with polynomial coefficients and multiply the fitting coefficients by the transfer matrix. The solving-time and the precision of the method are validated by analyzing the thermal effects on three different lenses with 0.2 s to get the node temperature and the Zernike coefficients of the surface deformation, while the general finite element analysis (FEA) method needs 600 s. Another advantage of the new method is that the solving-time isn′t lengthened with more nodes. Temperature peak valley (PV) error is 0.002 ℃, and fitting error of Zernike coefficient is 0.005 nm. The accuracy can match the requirement of calculating system aberration..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 712003 (2014)
An Infrared Reflection Measurement Method to Measure Concentrated Solar Flux Distributions of High Concentration Ratio
Dai Guilong, and Guo Yonghui
In order to measure the concentrated solar flux distributions of high concentration ratio, an infrared reflection measurement (IRM) method that bases on thermal infrared imager and water-cooled Lambert target is proposed, and the corresponding experimental apparatus are manufactured. Through the experiment at a sixteenIn order to measure the concentrated solar flux distributions of high concentration ratio, an infrared reflection measurement (IRM) method that bases on thermal infrared imager and water-cooled Lambert target is proposed, and the corresponding experimental apparatus are manufactured. Through the experiment at a sixteen-dish concentrator (SDC), clear infrared temperature images on the water-cooled Lambert surface are obtained. Then, the concentrated solar flux distributions of the SDC are simulated by the Monte Carlo ray-tracing method (MCRTM), taking into account the solar cone, the tracking error, and the slope error. By comparing with the experimental results and the simulation results, a slope error parameter of 2.5 mrad is detected. The conclusions can be used for measuring the concentrated solar flux distributions of high concentration ratio and finding out the slope error parameters of the solar concentrators..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 712004 (2014)
Phase Error Correction Algorithm for Grating Projection Measurement System
Wu Shuyu, Yang Yimin, Zhong Zhenyu, and Lu Xingjian
Based on monotonous growth characteristics of the phase of grating images, a monotonous smoothing algorithm based on least square method is proposed for phase error compensation. The monotonous characteristics and error of phase are analyzed in detail. Then a monotonous smoothing algorithm based on developed least squaBased on monotonous growth characteristics of the phase of grating images, a monotonous smoothing algorithm based on least square method is proposed for phase error compensation. The monotonous characteristics and error of phase are analyzed in detail. Then a monotonous smoothing algorithm based on developed least square method is used to correct phase error of absolute phase diagram. Experimental results show that the gamma nonlinearity of the projector is reduced by more than 60%, and the corrected absolute phase has the advantage of good smooth..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 712005 (2014)
Radiation Calibration Method for Infrared System with Large Aperture and Broad Dynamic Range
Sun Zhiyuan, Chang Songtao, and Zhu Wei
The existing radiation calibration for infrared system with large aperture and broad dynamic range needs huge infrared collimator, but this method has poor motility and cost much. In order to settle this question, a new calibration method basing on the amendment of inner and outer calibration is put forward. This methoThe existing radiation calibration for infrared system with large aperture and broad dynamic range needs huge infrared collimator, but this method has poor motility and cost much. In order to settle this question, a new calibration method basing on the amendment of inner and outer calibration is put forward. This method set a middle-high temperature cavity blackbody in infrared system, with the help of switching reflector, the cavity blackbody radiation is imported into optics system for the inner calibration on parts of system at middle-high temperature range, and an extended source blackbody is needed for the outer calibration on the whole system at middle-low temperature range. The inner and outer calibration data at common temperature range are picked up to calculate the amendatory coefficient. In the end, the whole system′s radiation calibration data at the middle-high temperature range are caught by amending the inner calibration data. Combining the outer calibration data at the middle-low temperature range, the whole system′s radiation calibration data at broad dynamic range are gained. Carrying through this method on an Φ400 mm infrared system and calculating the luminance error and temperature error, the maximal luminance error is 1.35% and the maximal temperature error is 0.76 ℃, the results indicate that the proposed method is effective..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 712006 (2014)
Wavefront Reconstruction Based on Standard Orthonormal Vector Polynomials in a Square Area
Li Mengyang, Li Dahai, Zhao Jiwen, Zhang Chen, and Wang Qionghua
A new set of orthonormal vector polynomials in a square area, which can be used in image distortion mapping and wavefront gradient vector datum fitting, is derived. These vector polynomials are developed from the gradients of the circular Zernike polynomials orthonormalization by using Gram-Schmidt technique. When the A new set of orthonormal vector polynomials in a square area, which can be used in image distortion mapping and wavefront gradient vector datum fitting, is derived. These vector polynomials are developed from the gradients of the circular Zernike polynomials orthonormalization by using Gram-Schmidt technique. When the slope is fitted by these vector polynomials, the fitting coefficients can be derived and transformed to the wavefront description of the Zernike polynomials mode by using a linear transform, and the phase information is then extracted. Experimental results show that the slope data from Shack-Hartmann wavefront sensor over a square area are well fitted by theses vector polynomials. The vector polynomial wavefront reconstruction method can reconstruct the tested wavefront quite well and achieve the same accuracy as Southwell zonal method does..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 712007 (2014)
Advanced Study and Generalization of Rotation-Incidence-Plane Method
Liu Yongli, Zhang Jinlong, and Wang Zhanshan
Reflectance and transmittance are main optical property of optical thin films. Transmittance is easier to be measured and has a higher accuracy than reflectance. Therefore, it′s frequently used to fit the optical constant and thickness of the film. Many coatings work in the oblique incidence case in application, and itReflectance and transmittance are main optical property of optical thin films. Transmittance is easier to be measured and has a higher accuracy than reflectance. Therefore, it′s frequently used to fit the optical constant and thickness of the film. Many coatings work in the oblique incidence case in application, and its oblique transmittances Ts and Tp are needed. A perfect polarizer with high extinction ratio is needed in this case. However, it costs too much for the compact spectrophotometer to provide such a polarizer. In order to solve this problem, rotation-incidence-plane (RIP) method is investigated deeply and generalized. Because RIP method makes measurement with a partially polarized beam, and the output beam of the spectrophotometer is partially polarized, RIP method can measure the oblique transmittance under certain condition. Advanced investigation found that if the absolute value of the polarization factor of the measurement beam is bigger than 0.167 the RIP method can make an accurate measurement about the oblique transmittance of optical coatings, and the polarization factor bigger the accuracy higher. This method has a good accuracy in the wavelength region, in which the transmittance is nearly flat or not sensitive very much to the incidence angle, when it′s used to measure the Ts and Tp. What′s more, the method has a better accuracy when it′s used to measure the average transmittance..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 712008 (2014)
Lasers and Laser Optics
Research on Interference Energy Calculation Method in Laser Ultrasonic Technique
Zhang Chao, Ji Hongli, Qiu Jinhao, and Wu Yucheng
In order to evaluate the position and shape of the structural damage, a damage visualization technique using interference energy calculation method is presented. Based on the wavefield visualization technique, this study analyzes the effects on ultrasonic wave propagation caused by the damage. To extract the interferenIn order to evaluate the position and shape of the structural damage, a damage visualization technique using interference energy calculation method is presented. Based on the wavefield visualization technique, this study analyzes the effects on ultrasonic wave propagation caused by the damage. To extract the interference energy from the wavefield near the damage, Fourier transform in both time and space domains is used to separate the incident and reflected wavefields and then the inference energy is calculated to image the damage. Due to the interference energy caused by the damage spreads widely, Morlet wavelet transform is used in broadband signal processing to improve the resolution of the damage imaging. After narrowband signal extraction, interference energy calculation is followed and the signal to noise ratio of the damage imaging is improved..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 714001 (2014)
Linear Polarized Yb3+-Doped Double-Clad Fiber Laser with an Intracavity Cubic Polarization Beam Splitter as Polarization Selection
Feng Dejun, Liu Guanxiu, Zhang Maosen, Liu Xilu, Ning Ding, and Jiang Shouzhen
A single and dual-wavelength switchable linear polarization Yb-doped double-clad fiber laser configuration is proposed, in which the resonance cavity is composed of a fiber Bragg grating fabricated in a polarization maintaining fiber and a high reflectivity dichromatic mirror. A cubic polarization beam splitter (PBS) rA single and dual-wavelength switchable linear polarization Yb-doped double-clad fiber laser configuration is proposed, in which the resonance cavity is composed of a fiber Bragg grating fabricated in a polarization maintaining fiber and a high reflectivity dichromatic mirror. A cubic polarization beam splitter (PBS) rotating around its own optical axis is inserted between the high reflection cavity mirror and the collimator in the laser cavity, which is used to adjust the polarization to realize single and dual-wavelength lasing emission. The polarization hole burning is enhanced by the selective polarization feedback from the polarization maintaning fiber Bragg grating (PM-FBG). The relationship between polarization states and rotating angle of PBS is analyzed by using Jones matrix, which agrees well with the experimental results. The laser features wavelength of 1070.08 nm and 1070.39 nm, output power of 1.0 W, signal noise ratio of 48 dB, slope efficiency of 34%, as well as a very narrow linewidth of 0.02 nm. The polarization characteristics are studied by measuring the laser power transmitted through a Glan-Thomson polarizer. The polarization state of the laser is linearly polarized with a polarization degree of 13.37 dB when it is lasing at single wavelength, while it is orthogonal polarization laser for dual wavelength operating..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 714002 (2014)
Machine Vision
Depth Estimation of Urban Road Image Based on Contour Understanding
Ding Weili, Li Yong, Wang Wenfeng, and Cao Xiuyan
Estimating the depth of the road scene is a key step for intelligent transportation and robot navigation. A depth estimation algorithm for single static road image is presented. The algorithm obtains a series of closed areas of the image based on the edge growing segmentation algorithm. The statistic characteristics ofEstimating the depth of the road scene is a key step for intelligent transportation and robot navigation. A depth estimation algorithm for single static road image is presented. The algorithm obtains a series of closed areas of the image based on the edge growing segmentation algorithm. The statistic characteristics of each region are computed, including color, area, position, straight lines, vertical lines, and parallel lines. Based on these characteristics, the road vanishing point is further estimated, and the sky, road and vertical regions are estimated. The depth of the road image is estimated by using vanishing point and the statistic characteristics. The experimental results show that the proposed algorithm can effectively estimate the road vanishing point, as well as the road depth information..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 715001 (2014)
Crop Recognition and Navigation Line Detection in Natural Environment Based on Machine Vision
Meng Qingkuan, He Jie, Qiu Ruicheng, Ma Xiaodan, Si Yongsheng, Zhang Man, and Liu Gang
In order to solve the problems of serious illumination interference for image processing and the poor robustness of conventional navigation line detection algorithms in agricultural navigation robot based on machine vision, the methods of crop recognition and navigation line extraction in natural environment are studieIn order to solve the problems of serious illumination interference for image processing and the poor robustness of conventional navigation line detection algorithms in agricultural navigation robot based on machine vision, the methods of crop recognition and navigation line extraction in natural environment are studied. Cg component of YCrCg color model is selected for subsequent image processing to reduce the adverse effects of light change on image segmentation and navigation line extraction. The fuzzy C-means clustering method (FCM) based on two-dimensional histogram is used for Cg component segmentation, so as to identify the green crop. According to the characteristics of crop rows in mage, a method of crop line detection based on linear scanning is designed. Pixel on image bottom and top edge are selected as two endpoints of a straight line, by moving the endpoints location result in different slope lines, the line containing the most target points is chosen as the crop centerline, and then obtain the navigation line. The experimental results show that image segmentation based on YCgCr color model can effectively identify the crops under different illumination conditions. Further more, the time consumption for single image of 640 pixel×480 pixel is about 16.5 ms. The linear scanning algorithm can quickly and accurately find the navigation line. Compared with Hough transform and least square algorithm, the designed algorithm has the advantages of high speed and good robustness..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 715002 (2014)
Nonlinear Optics
Research on Ring-Like Vortex Solitons in Bessel Lattices
Yu Wensu, Qin Yali, Ren Hongliang, Li Jia, and Xue Linlin
This paper studies the propagation of a vortex beam in Bessel lattices, which are produced by optical induction in the focusing photorefractive nonlinear crystal. By numerical simulation, different results are got under different parameters, such as the intensity of the bias electric field on the lattices, the transverThis paper studies the propagation of a vortex beam in Bessel lattices, which are produced by optical induction in the focusing photorefractive nonlinear crystal. By numerical simulation, different results are got under different parameters, such as the intensity of the bias electric field on the lattices, the transverse scale coefficient and the deep of the Bessel lattices. These results show that because of existence of the lattices, the input ring vortex beam can overcome the azimuthal modulation instabilities induced by the focusing nonlinearity and form a ring-like vortex soliton which can propagate stably in a quite long distance under appropriate conditions. In addition, the input beam can evolve into a structure of two rings that the big ring surrounds the small one during propagation when the energy of input beam is not just seated in the ring-like channel of the Bessel lattices..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 719001 (2014)
Generation and Management of Optical Self-Similar Waves in Inhomogeneous Graded-Index Waveguides
Wang Dake, Wang Juanfen, Dang Tingting, Zhang Zhaoxia, and Yang Lingzhen
Based on the nonlinear Schrdinger equation with variable coefficients, which can describe the transmission of optical wave in inhomogeneous graded-index waveguide, the generation and management of bright and dark self-similar waves in different waveguides are discussed. According to the exact optical self-similar soluBased on the nonlinear Schrdinger equation with variable coefficients, which can describe the transmission of optical wave in inhomogeneous graded-index waveguide, the generation and management of bright and dark self-similar waves in different waveguides are discussed. According to the exact optical self-similar solutions of the equation, the evolutions of the self-similar waves in the Kerr nonlinear plane waveguide, the homogeneous graded-index waveguide, and the inhomogeneous graded-index waveguides with periodic distribution and with hyperbolic distribution are studied in detail respectively. The results show that the generation of the self-similar wave relates to the distributions of the linear and nonlinear refractive indexes. The self-similar waves can be compressed and amplified in both homogeneous system and hyperbolic system. However, in the hyperbolic system, the transmission distance of self-similar waves can be more limited. In a periodic oscillation system, self-similar waves with a periodic oscillation can be generated and propagate stably..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 719002 (2014)
Optical Design and Fabrication
Optical Design of Large Field and Low Distortion Coaxial Three Mirror System with Free-Form Surface
Gong Dun, and Wang Hong
Remote sensing mapping applications need optical system with long focal length, wide width, low distortion, small volume, and the optical system can be designed for integration on satellite platform. Through the structure selection, modified coaxial three mirror system is adopted to realize long focal length, wide widtRemote sensing mapping applications need optical system with long focal length, wide width, low distortion, small volume, and the optical system can be designed for integration on satellite platform. Through the structure selection, modified coaxial three mirror system is adopted to realize long focal length, wide width and low distortion at the same time. Because of the influence of the second obscuration and large field, the image quality of general aspheric optimization design cannot meet the requirements. Degrees of freedom are increased efficiently by the introduction of free-form surface. After optimization design, the optical design modulation transfer function (MTF) is greater than 0.418 at 72 lp/mm, and the maximum relative distortion is less than 0.00145%. Imaging quality is improved significantly. The free-form surface is tested and fine grinded by the application of computer-generated holography (CGH) technology, the root mean square (RMS) of remnant wavefront error is 0.007λ, and the peak to valley (PV) value is 0.027λ, remnant wavefront error meet the requirements of free-form surface irregularity tolerance. Laboratory static MTF is tested after processing and adjustment, the minimum static MTF is 0.225 at 72 lp/mm, the image quality meet the requirements of technical indicators..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 722001 (2014)
Numerical Simulation of Segmented Telescope
Liao Zhou, Qiu Qi, and Zhang Yudong
In order to have a better understanding of the optical properties of segmented telescope system and conduct an effective analysis of the impacts of various errors induced by single segmented mirror of primary mirror, this article aims at builting a model of segmented telescope system from the perspective of geometry opIn order to have a better understanding of the optical properties of segmented telescope system and conduct an effective analysis of the impacts of various errors induced by single segmented mirror of primary mirror, this article aims at builting a model of segmented telescope system from the perspective of geometry optical with optical raying tracing. This model enables to simulate the segmented telescope of different sizes, and can get the wavefront aberration and the far-field image of the segmented telescope with the piston error, tip-tilt and rotation error ect. Strehl ratio of segmented telescope with different errors is calculated. The work is expected to provide technological support for the further development of large diameter telescopes..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 722002 (2014)
Optical Devices
Surface Plasmonic Micropolarizers Based on Ag Nanorod Arrays
Yu Jie, Zhang Junxi, Zhang Lide, and Fei Guangtao
Extinction spectra of Ag nanorod arrays under incident light with different polarization directions are calculated by an electrostatics approximation theory. A longitudinal resonance mode of the localized surface plasmons (LSPs) can be excited when the polarization direction is parallel to the long axis of the nanorodsExtinction spectra of Ag nanorod arrays under incident light with different polarization directions are calculated by an electrostatics approximation theory. A longitudinal resonance mode of the localized surface plasmons (LSPs) can be excited when the polarization direction is parallel to the long axis of the nanorods, while a transversal resonance mode of the LSPs can be excited when the polarization direction is perpendicular to the long axis. In this case, high-performance plasmonic micropolarizers based on the different resonance wavelengths of the two modes can be designed by use of the Ag nanorod arrays. The polarization property of the Ag nanorod arrays at the longitudinal resonance wavelengths is prominently better than that at the transversal resonance wavelengths, and the resonance peak of the longitudinal mode can be tuned in a broad spectra region by adjusting the aspect ratio of the nanorods. The wavelength of the micropolarizers can be tuned from the visible to near-infrared spectra region by changing the aspect ratio of the nanorods. Moreover, the extinction ratio and insertion loss can also be adjusted by control of the diameter and length of the nanorods..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 723001 (2014)
External Factors Analysis for Influence of Low-Contrast Target Capture Capability on Photoelectric Tracker
Huang Xin, Shen Xiangheng, and Ye Lu
The method to detect the capture capability of photoelectric tracker affected by the external factors is analyzed. The mathematical equations that involve the relations between image contrast and the external factors which include target size, target velocity, target contrast in object space, light (dark) target are puThe method to detect the capture capability of photoelectric tracker affected by the external factors is analyzed. The mathematical equations that involve the relations between image contrast and the external factors which include target size, target velocity, target contrast in object space, light (dark) target are put forward. The detection environment consists of the adjustable contrast optical target device, high-speed camera, capture simulator and turntable. Characteristic analysis of the different external factors on capture capability gets fine mutual verification by the model analysis and image analysis. The experimental results show that the fitting equations is suitable for the accurate calculation between image contrast and the external factors in the background of which the spectral radiance is 3.2 W/(sr·m2). The study on the external factors and image contrast is meaningful for the evaluation of the capture capability on photoelectric tracker..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 723002 (2014)
Terahertz Polarization Splitter Based on Filled Porous Fiber
Li Shanshan, Chang Shengjiang, Zhang Hao, and Liu Weiwei
A broadband terahertz polarization splitter based on filled porous fiber is proposed. The fiber structure is designed by using index converse matching coupling method. The numerical simulation is completed by employing full vector finite element method. The background material is TOPAS. The properties of dispersion andA broadband terahertz polarization splitter based on filled porous fiber is proposed. The fiber structure is designed by using index converse matching coupling method. The numerical simulation is completed by employing full vector finite element method. The background material is TOPAS. The properties of dispersion and birefringence for before and after filling a common porous fiber are analyzed in detail. It can be found that after interlacing filling to the porous fiber, the mode birefringence of the fiber improves an order of magnitude that changes from 10-3 to 10-2. Then we analyze the properties of terahertz polarization splitter based on filled porous fibers. The numerical simulation shows that the splitting operation can be realized in a broad frequency ranging from 0.8 THz to 2.5 THz. At 1 THz, the splitting length is only 0.77 cm, and the practical material absorption losses for x- and y- polarization are less than 0.20 dB, respectively. The extinction ratios for x- and y- polarization are -12.73 dB and -13.70 dB, respectively. Compared with other designs of dual-core-PCF based polarization splitter, porous fiber is simpler in design, easier in fabrication, and more feasible in experiment. Moreover, this structure has advantages of tunable, low loss and broadband..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 723003 (2014)
Fused-Silica Beam Splitter Grating Design Based on Modified Simplified Modal Method
Wang Bin, Hao Peng, Wu Yihui, and Li Yin
The simplified modal method (SMM), which is used to estimate the initial values of grating parameters, is modified. The reflection of dielectric grating is considered. Then grating is equivalent to multilayer thin films. Associating with the modal theory, transmission efficiency is calculated, and SMM is modified. The The simplified modal method (SMM), which is used to estimate the initial values of grating parameters, is modified. The reflection of dielectric grating is considered. Then grating is equivalent to multilayer thin films. Associating with the modal theory, transmission efficiency is calculated, and SMM is modified. The calculation results show that deviation between this modified method and RCWA is less than 2% for TE and TM polarizations which is better than SMM. With respect to SMM, which only gives starting value of grating parameters, this method can be used to optimize the grating parameters. Contrast to RCWA, it gives a clear physical explanation of grating diffraction by considering the transmission efficiency as the result of phase shift of modes and difference of grating and aerial admittance. Then a grating beam splitter with two ports is designed and optimized by this modification of simplified modal method (MSMM), which gets a good splitting result at the band of 1020~1100 nm. The transmission efficiency of 0th and -1st order for both TE and TM polarizations is near to 50% at this band..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 723004 (2014)
Quantum Optics
Dynamics of Quantum Entanglement in a Two-Qubit XXZ Heisenberg System
Guo Zhanying, Zhang Xinhai, Xiao Ruihua, Fang Jianxing, and Hu Jie
On condition that the intrinsic decoherence is taken into account, the dynamic evolution of entanglement of a two-qubit XXZ Heisenberg system under the influence of various factors is investigated. It is found that the intrinsic decoherence obviously suppresses the time evolution of the entanglement whether the initialOn condition that the intrinsic decoherence is taken into account, the dynamic evolution of entanglement of a two-qubit XXZ Heisenberg system under the influence of various factors is investigated. It is found that the intrinsic decoherence obviously suppresses the time evolution of the entanglement whether the initial state is maximally entangled or not. When the initial state is the entangled state |ψ(0)〉=c|01〉+d|10〉, the system entanglement is clearly influenced by the Dzyaloshinskii-Moriya (DM) interaction and the intrinsic decoherence, and it is independent of the anisotropy and the external magnetic field. If the initial state is the entangled state |ψ(0)〉=a|00〉+b|11〉, the system entanglement suffers from not only the intrinsic decoherence but also the external magnetic field, and has nothing to do with the DM interaction and anisotropy..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 727001 (2014)
Raman Coupling Strength in Spin-Orbit Couped Bose-Einsten Condensate
Huang Lianghui, Wang Pengjun, Fu Zhengkun, and Zhang Jing
Rabi frequency and coupling strength of the Raman transition in Bose-Einstein condensate are studied experimentally. Rabi frequency is an important parameter of the interaction between light field and atoms. It is used to measure the coupling strength between light field and atoms. Raman transition coupling strength isRabi frequency and coupling strength of the Raman transition in Bose-Einstein condensate are studied experimentally. Rabi frequency is an important parameter of the interaction between light field and atoms. It is used to measure the coupling strength between light field and atoms. Raman transition coupling strength is a crucial parameter in the experiment of spin-orbit coupling. The Rabi oscillation of Raman transition between Zeeman states |1,0〉 and |1,1〉 in hyperfine state F=1 of 87Rb is investigated with different frequency detuning of Raman laser. Moreover, Rabi oscillation coupled simultaneously in the five Zeeman energy levels of hyperfine atomic state F=2 is observed with Raman laser wavelength at 800 nm. This work is conductive to optimize the experimental parameters of 87Rb spin-orbit coupling..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 727002 (2014)
Remote Sensing and Sensors
Influence of Inner Wave-front Aberration on Down-Looking Synthetic Aperture Imaging Ladar Imaging
Lu Zhiyong, Sun Jianfeng, Zhi Yanan, Zhou Yu, Luan Zhu, Zhang Ning, and Liu Liren
Down-looking synthetic aperture imaging ladar (SAIL), with a transmitter of direct wave-front transformation in inner optical fields by parallel scanning, makes use of self-heterodyne detection to improve the resolution of images. Wave-front aberration in inner optical fields has effects on the imaging quality of the dDown-looking synthetic aperture imaging ladar (SAIL), with a transmitter of direct wave-front transformation in inner optical fields by parallel scanning, makes use of self-heterodyne detection to improve the resolution of images. Wave-front aberration in inner optical fields has effects on the imaging quality of the down-looking SAIL because the optical fields on the target plane depend on the inner optical fields at the focal plane of main lens. Zernike polynomials are proposed to represent wave-front aberrations. The influence of primary aberrations on down-looking SAIL imaging is investigated. The results show that focus, astigmatism, coma and spherical aberrations have significant influence on imaging, and the deeper the aberrations are, the more significant the influence on the resolution of images is. When the root mean square (RMS) value of primary aberrations is less than 0.05λ, the influence on resolution of images is very small. When the RMS value is up to 0.25λ, the resolution of images is up to 3 times in the condition of astigmatism and coma aberrations. Meanwhile, the target pointing at different positions has different resolutions with coma and spherical aberrations. The further the imaging targets from the center position are, the more significant the influence on the resolution of images is..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 728001 (2014)
Design of Spectral Target Used to Assess the Degradation of Multi-Spectral Sensor in Flight
Li Xin, Zhang Liming, Chen Hongyao, and Xu Weiwei
When the multi-spectral sensor works in the space, it is affected by temperature variations, space radiation and other factors, which may produce changes in the spectral response characteristics. As a result, bias occurs in the physical measurements which cannot be corrected by radiometric calibration methods. With theWhen the multi-spectral sensor works in the space, it is affected by temperature variations, space radiation and other factors, which may produce changes in the spectral response characteristics. As a result, bias occurs in the physical measurements which cannot be corrected by radiometric calibration methods. With the help of spectral targets and appropriate degradation models, the degradation characteristics of the multi-spectral sensor can be assessed. To achieve this purpose, suitable spectral targets should be designed. Based on simulation experiments, it can be concluded that the targets with Gauss model spectral reflectance are the most suitable for on-orbit assessment, and the on-orbit experiment result verifies the conclusion above..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 728002 (2014)
Image Motion Velocity Filed of TDI-CCD Aerial Panoramic Camera
Zhao Jiaxin, Zhang Tao, Yang Yongming, Li Xinyang, and Wang Dejiang
Image motion compensation of aerial panoramic camera can be accomplished by employing scan head rotation and charge coupled device (CCD) time delay integration (TDI), whereas residual still remains. Therefore, based on the structure and the image motion compensation (IMC) mechanism of aerial panoramic camera, a rigor mImage motion compensation of aerial panoramic camera can be accomplished by employing scan head rotation and charge coupled device (CCD) time delay integration (TDI), whereas residual still remains. Therefore, based on the structure and the image motion compensation (IMC) mechanism of aerial panoramic camera, a rigor mathematical model of image motion velocity filed is derived from imaging geometry, which is built by coordinate transformation and collinear equation. Numerical analysis indicates that the closer image coordinate locates to the rear edge of CCD focal plane, the larger scan angle and forward motion compensation (FMC) angel are, and the faster the image motion velocity is. For an aerial panoramic camera with 14000 CCD pixel and 100 TDI stages, when scan angle and FMC angle is smaller than -1.5°and 4.16°, respectively, the maximum of image motion is less than 1 pixel pitch. Dynamic imaging experiments validate the rationality of the model which provides a theoretical basis for the quantitative analysis of image motion compensation residual..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 728003 (2014)
Source Analysis of Radio-Frequency Interference over Europe Land from Advanced Microwave Scanning Radiometer-E
Guan Li, and Zhang Sibo
The radio-frequency interference (RFI) over Europe land is identified and analyzed based on advanced microwave scanning radiometer-E (AMSR-E) observations from June 1 to 16, 2011 using modified principal component analysis algorithm. The X band AMSR-E measurements of England and Italy are mostly interfered by the stablThe radio-frequency interference (RFI) over Europe land is identified and analyzed based on advanced microwave scanning radiometer-E (AMSR-E) observations from June 1 to 16, 2011 using modified principal component analysis algorithm. The X band AMSR-E measurements of England and Italy are mostly interfered by the stable, persistent active surface microwave transmitters. While the RFI source of other European countries is the interference of the reflected geostationary TV satellite downlink signals to the measurements of spaceborne microwave radiometer. The RFI location and intensity derived from the geostationary TV or communication satellite changes with time within observation period. The observations of spaceborne microwave radiometer of desending portions of orbits are usully interfered over Europe land, while ascending portions of orbits are hardly interfered. The RFI location and intensity from the reflection of downlink radiation are highly dependent upon the relative geometry between the geostationary satellite and the measuring passive sensor. Only these field of views which the scanning azimuth of spaceborne instrument is close to the relative azimuth to the geostationary satellite are easily effected by RFI..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 728004 (2014)
Detection and Compensation of Satelliteflutter Based on Image from Multispectral Camera with Five Spectral Combinations
Sun Tao, Long Hui, Zhao Dong, and Li Ying
A method which uses optical satellite multispectral camera with five spectra combinations (MCFS) image in quantitative detection of satellite flutter and point spread function (PSF) space variant blurring model method for flutter compensation are proposed. The working principles of time delay integration (TDI) charge cA method which uses optical satellite multispectral camera with five spectra combinations (MCFS) image in quantitative detection of satellite flutter and point spread function (PSF) space variant blurring model method for flutter compensation are proposed. The working principles of time delay integration (TDI) charge coupled device (CCD) and the influence of satellite flutter on the TDICCD image are introduced. The method of using MCFS image in satellite flutter quantitative detection is proposed. In the flutter detection technology, the robust phase correlation scan angular correlation matching algorithm, which can achieve 1/50 pixel registration precision, is used for registration between bands. The PSF space variant blurring model method is used for image restoration. Beijing regional image from ZY-3 is used in experiments and carried out with definition, details energy, edge energy, and contrast as objective evaluation index. Results show that the objective evaluation index of restoration image is improved about 2 times. At the same time, the same regional orthophoto from SPOT5 is used for compared experiment in objective evaluation index. Comparative results also preliminarily show the evidence of better restoration of satellite flutter reduction..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 728005 (2014)
High Sensitivity Micro-Vibration Sensor Based on Distributed Bragg Reflector Fiber Laser
Lu Wengao, Sun Qizhen, Wo Jianghai, Wang He, and Liu Deming
A high sensitivity micro-vibration senor based on distributed Bragg reflector (DBR) fiber laser is designed and demonstrated. The sensor structure uses common mass-spring system. Due to gravity, the DBR laser cavity is subjected to lateral pressure caused by the mass. Because the lateral pressure that the laser cavity A high sensitivity micro-vibration senor based on distributed Bragg reflector (DBR) fiber laser is designed and demonstrated. The sensor structure uses common mass-spring system. Due to gravity, the DBR laser cavity is subjected to lateral pressure caused by the mass. Because the lateral pressure that the laser cavity suffers changes when the testing platform is vibrating, the beat frequency generated by two orthogonally polarized modes of the laser output changes. By the high-speed photodetector and multi-channel data acquisition platform, the beat frequency signal is collected. The signal can be dealed with through the LabVIEW programming and the real-time monitoring of the vibration acceleration signal is achieved. Theoretical analysis and experimental results show that, the sensor has a very high acceleration sensitivity, which is up to gigahertz for an acceleration of gravity g, and can detect very weak vibration signal. Compared with the traditional optical fiber vibration sensors, this sensor convert optical spectrum analysis to frequency spectrum analysis, which makes the signal acquisition and demodulation easier, and obtains a higher sensitivity. Further analysis shows that the measurement of this structure in the micro-gravity environment is also feasible. Therefore, it has great potential in the micro-vibration measurements of key components of aerospace craft..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 728006 (2014)
Spectroscopy
Study of Thin-Film Method X-Ray Fluorescence Spectroscopy for Detecting Heavy Metal Chromium Element
Gan Tingting, Zhang Yujun, Zhao Nanjing, Yin Gaofang, Dong Xinxin, Wang Yaping, Liu Jianguo, and Liu Wenqing
Filter membrane in heavy metal Cr element thin film method X-ray fluorescence (XRF) spectroscopy analysis is studied. The results show that Cr element preconcentrated on hydrophilic polytebrafluoroe thylene (PTFE) membranes has good uniformity, and XRF spectroscopy detection of Cr element preconcentrated on these membrFilter membrane in heavy metal Cr element thin film method X-ray fluorescence (XRF) spectroscopy analysis is studied. The results show that Cr element preconcentrated on hydrophilic polytebrafluoroe thylene (PTFE) membranes has good uniformity, and XRF spectroscopy detection of Cr element preconcentrated on these membranes has good sensitivity. Different mass concentrations of Cr element are preconcentrated by using hydrophilic PTFE membranes and measured by XRF spectroscopy. The results show that when area concentration of Cr element is in the range of 3.84~167 μg·cm-2, the fluorescence integrated intensity of Cr Kα characteristic spectral line has a very good linear relationship with the area concentration of Cr element. The linear correlation coefficient is 0.996, and the limit of detection is 0.3 μg·cm-2. The spiked recovery experiments on tap water samples of laboratory faucet are carried out. The obtained recoveries are between 93.85% and 101.95%, and the relative standard deviation is less than 2%. As a result, the thin film method XRF spectroscopy analysis with hydrophilic PTFE membrane as preconcentrated filter membrane can be well applied to the analysis and detection of heavy metal Cr element in water samples..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 730001 (2014)
Adaptive Detection for Pollutant Gases Based on Orthogonal Subspace Projection
Cui Fangxiao, and Fang Yonghua
Identification and classification is the main purpose of hyperspectral imaging remote sensing pollutant gases, then the spatial distribution of the pollutant gases is obtained, as well as the location of the pollutant source. In practical applications, target spectrum is superimposed on intense background radiation, inIdentification and classification is the main purpose of hyperspectral imaging remote sensing pollutant gases, then the spatial distribution of the pollutant gases is obtained, as well as the location of the pollutant source. In practical applications, target spectrum is superimposed on intense background radiation, in addition, the spectra measured in open path comprise atmosphere interferences spectra which restrict identification and classification for target spectra. On the basis of linear model, orthogonal subspace projection method is used to effectively suppress the background and interferences′ information, and the subspace detector, based on gerneralized likelihood ratio test principle, is used to classify all pixels one by one. The field experiment is performed with ammonia as target gas, the data cube comes from scanning imaging Fourier transform infrared spectroscopy (FTIR) spectrometer, and the subspace vectors come from singular value decomposition (SVD). The recognition results for all pixels by subspace detector are superior to spectral angel mapper (SAM) algorithm..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 730002 (2014)
Thin Films
Research of Ultraviolet Filter Film in Solar Blind Communication System
Fu Xiuhua, Kou Yang, Liu Dongmei, Zhang Jing, and Zhu Hao
Ultraviolet solar blind communication with its excellent optical characteristics has been more and more applied in the optical system. Compared with the conventional communication systems, the advantages of ultraviolet solar band communication are simple structure, low false alarm rate, high sensitivity and strong concUltraviolet solar blind communication with its excellent optical characteristics has been more and more applied in the optical system. Compared with the conventional communication systems, the advantages of ultraviolet solar band communication are simple structure, low false alarm rate, high sensitivity and strong concealment, etc. In order to satisfy the requirement of ultraviolet communication system and to improve the efficiency of signal acquisition, a high-performance ultraviolet filter film is required to ensure the system′s steadiness. Appropriate ultraviolet film material are selected according to the thin film theory. In the aspect of film design, the independent sensitivity and errors distribution are analyzed and amended to reduce the sensitivity of the film. In the meantime, the reverse test analysis is used to solve the problem of film thickness which is due to the equipment error and control error. Eventually, the average transmittance of the film is 86% at the band of 240~280 nm and the rejection ratio is less than 0.2% at the band of 290~360 nm. The film has passed the relevant environmental tests of national military standard..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 731001 (2014)
Optimal Weak Measurements of Photonic Spin Hall Effect in Nanometal Film
Li Xing, Zhou Xinxing, and Luo Hailu
Photonic spin Hall effect (SHE) is a potential precision measurement tool, which has important physical significance in the study of detecting the change of microstructure material′s structure parameters. The photonic SHE in nanometal films is studied using the weak measurement model. The results show that when the ampPhotonic spin Hall effect (SHE) is a potential precision measurement tool, which has important physical significance in the study of detecting the change of microstructure material′s structure parameters. The photonic SHE in nanometal films is studied using the weak measurement model. The results show that when the amplification angle takes the special value (the optimal weak measurement point) in the weak measurement, the amplified transverse shift of the photonic SHE in nanometal films can reach the maximum, which greatly improves the detection precision of the photonic SHE. In addition, the amplified shift obtained in the optimal weak measurement point can be used to determine the actual thickness of the nanometal film with higher accuracy. The experimental results coincide well with the theoretical analysis. This method provides theoretical and experimental basis for the future development of precision measuring tools..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 731002 (2014)
Fabrication of a Narrow Bandpass Optical Filter with Central Wavelength at 14.95 μm
Zhang Lin, Ni Rong, Huang Chun, Li Bin, and Liu Dingquan
The design and fabrication of infrared ultra-narrow bandpass filters is presented, which have been employed in the channel No.1 in the infrared atmospheric sounder (IRAS). The filters are fabricated using Te-rich PbTe as the high-index coating material. By choosing suitable deposition rate and substrate temperature, thThe design and fabrication of infrared ultra-narrow bandpass filters is presented, which have been employed in the channel No.1 in the infrared atmospheric sounder (IRAS). The filters are fabricated using Te-rich PbTe as the high-index coating material. By choosing suitable deposition rate and substrate temperature, the carrier concentration in the layers of PbTe can be controlled to a lower level in order to obtain the higher transmittance for the filters. The filters have a central wavelength at 14.95 μm and a bandwidth of 0.065 μm. The relative bandwidth is less than 0.5%. The filter has been used in space and worked stably for five years in the data acquisition of weather forecast..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 731003 (2014)
Vision, Color, and Visual Optics
Temporal Properties Study of Ocular Wave Aberrations with High Frequency Sampling
Zheng Xianliang, Liu Ruixue, Xia Mingliang, Li Dayu, and Xuan Li
Temporal properties of ocular wave aberrations are researched to improve the performance of eye aberration correction based on adaptive optical systems and the result for retinal imaging. Using a Shack\|Hartmann wavefront sensor at a sampling rate of 330 Hz and exposure time of 3 ms, an optical system is constructed toTemporal properties of ocular wave aberrations are researched to improve the performance of eye aberration correction based on adaptive optical systems and the result for retinal imaging. Using a Shack\|Hartmann wavefront sensor at a sampling rate of 330 Hz and exposure time of 3 ms, an optical system is constructed to detect human eye′s wave aberration. The averaged root mean square (RMS) of detecting errors of the system is proved to be 0.01λ by error analysis and an experiment on schematic eye. Detection results show that the existence of fluctuations of ocular wave aberration above 150 Hz can probably impact the performance of adaptive optics systems for wave aberration correction. These fluctuations can be reduced by increasing the detection and exposure times of the detector. In order to reach the diffraction limit, for eyes in the state of steady gaze, correction residual error RMS of adaptive optical system is less than λ/14, when detecting exposure time is 3 ms and detecting correction period is less than 45 ms. while the detecting correction period can increase to 62 ms as long as the exposure time is set to 6 ms. Analysis on tilt aberration proves that exposure time of high resolution retinal imaging should be less than 9 ms to avoid horizontal movements. Weighting the tradeoff between aberration fluctuation and horizontal movements, exposure times of detection and imaging are both set to about 6 ms..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 733001 (2014)
Study on the Effect of Ambient Light Flicker in Stereoscopic Display with Active Shutter Glasses
Xia Zhenping, Li Xiaohua, Chen Lei, and Wang Jian
To optimize the flicker phenomenon in active shutter type stereoscopic display, the influence of ambient light is deeply investigated. The transient luminance response measurement system with high sampling rate is used to measure and record ambient light through shutter glasses in real time. The measured time domain siTo optimize the flicker phenomenon in active shutter type stereoscopic display, the influence of ambient light is deeply investigated. The transient luminance response measurement system with high sampling rate is used to measure and record ambient light through shutter glasses in real time. The measured time domain signal is transformed into frequency domain through Fourier transformation for the analysis of possible flicker source. Meanwhile, two perception experiments are implemented based on the multi-parameter adjustable light emitting diode (LED) lighting system. The experiment result shows that the involved factors such as frequency, maximum intensity, duty cycle and displayed image on the display, all have significant effect on the ambient light flicker felt by human eye through shutter glass, and 120 Hz or higher times frequency as matching ambient light can eliminate the flicker caused by ambient light and accomplish better visual comfort. The investigation result guides and facilitates the optimization of flicker in stereoscopic display with active shutter glasses and the improvement of visual comfort..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 34, Issue 7, 733002 (2014)
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