Journals >Acta Photonica Sinica
Contents
2020
Volume: 49 Issue 12
22 Article(s)
Export citation format
Fiber Optics and Optical Communications
FBG Demodulation Method Based on Frequency Shift Interference Digital Mixing Algorithm
Cong WEI, Ci-ming ZHOU, Xi CHEN, Yu-xiao LI, Han-jie LIU, and Dian FAN
According to the characteristics of the system that the wavelength of the optical signal is calculated by the phase of the modified frequency shift interference system， a digital mixing method based on the modified frequency-shift interference system was proposed， and the FBG wavelength demodulation was experimented. IAccording to the characteristics of the system that the wavelength of the optical signal is calculated by the phase of the modified frequency shift interference system， a digital mixing method based on the modified frequency-shift interference system was proposed， and the FBG wavelength demodulation was experimented. In the demodulation process， the algorithm combines the advantages of the frequency shift interferometric technology to accurately locate the grating， improves the frequency consistency between the local oscillator signal and the original interference signal in the signal mixing stage， and realizes the high-precision phase demodulation of the interference signal. A FBG sensor system was built based on the modified frequency-shift interference structure. In the simulation and experimental test， the wavelength information contained in the initial phase of the interference signal is accurately obtained by digital mixing method. The demodulation error of the 1.5 nm wavelength change signal is less than 0.26%. At the same time， the temperature sensing experiment of quasi dynamic signal is carried out， which has a good effect of wavelength demodulation， and has a certain application prospect in sensor monitoring..
Acta Photonica Sinica
- Publication Date: Dec. 25, 2020
- Vol. 49, Issue 12, 34 (2020)
Research on the Performance of Cantilever Low Frequency Vibration Sensor Based on Thin-diameter Excessively Tilted Fiber Grating
Xue ZOU, Ou DENG, Bin-bin LUO, De-cao WU, Ming-fu ZHAO, Nian-bing ZHONG, Tao SONG, Shang-hai JIANG, Lang XIE, Peng LIU, and En-hua LIU
In order to measure the low-frequency vibration parameters of the structure， a thin-diameter Excessively Tilted Fiber Grating （ExTFG） cantilever vibration acceleration sensor is proposed， and the characteristics and optimization methods of the sensor are studied. Firstly， the characteristics of axial strain and bendingIn order to measure the low-frequency vibration parameters of the structure， a thin-diameter Excessively Tilted Fiber Grating （ExTFG） cantilever vibration acceleration sensor is proposed， and the characteristics and optimization methods of the sensor are studied. Firstly， the characteristics of axial strain and bending strain of the thin-diameter ExTFG and the sensor model of vibration of cantilever beam are analyzed theoretically. Then， the influence of axial tension and bending strain on the vibration of the cantilever beam is analyzed by static experiments. Finally， the dynamic vibration test of cantilever beam is completed and compared with the standard-diameter ExTFG sensor. Experimental results indicate that under the effect of axial tension and bending stress， the axial strain sensitivity of TE and TM mode of the thin ExTFG is -4.68 pm/με and -3.55 pm/με， respectively， the wavelength based sensitivity of bending strain is -8.82 nm/m-1 and -7.71 nm/m-1， respectively， the intensity based sensitivity of bending strain is 6.71 dB/m-1 and 0.95 dB/m-1， respectively， and the thin ExTFG has a higher strain sensitivity than that of the standard ExTFG. In the cantilever vibration detection experiment， the maximum acceleration sensitivity at the 3 dB point is more than 500 mV/g， which is about 5 times of the standard-diameter ExTFG sensors under the same conditions. Compared with the spectral diagram after FFT transformation， the harmonic component of the thin-diameter ExTFG sensor is less than those of the standard one. Therefore， in the vibration sensing， the thin-diameter ExTFG has stronger anti-noise interference ability and higher detection accuracy..
Acta Photonica Sinica
- Publication Date: Dec. 25, 2020
- Vol. 49, Issue 12, 42 (2020)
Pulse Wave Signal Feature Recognition Based on Time-domain Differential Period Ratio
Bao-cun FAN, Yan WANG, Chen-chen HUANG, Zi-yang GE, and Ping JIN
Based on the formation mechanism and distribution characteristics of the pulse wave characteristics， this paper proposes to use PDMS packaged fiber grating flexible sensor to detect the human wrist pulse wave signal， aiming at the four most common types of pulse waves： obvious， hidden and partly obvious. The pulse waveBased on the formation mechanism and distribution characteristics of the pulse wave characteristics， this paper proposes to use PDMS packaged fiber grating flexible sensor to detect the human wrist pulse wave signal， aiming at the four most common types of pulse waves： obvious， hidden and partly obvious. The pulse wave signal feature extraction method based on the time-domain differential period ratio uses the relative position and proportional relationship of each feature point in the pulse wave time-domain differential signal as feature parameters， and realizes a comprehensive algorithm from pulse wave detection to feature point extraction. The results show that for the 4 050 pieces of experimental data collected， the algorithm can accurately identify the characteristic points of the starting point and the crest. In the resting state， the identification accuracy of the tidal wave d and e points is 98.28% and 97.25%. The recognition accuracy rates of points f and g are 98.14% and 99.19%； in the state of exercise， the recognition accuracy rates of tidal waves d and e are 94.23% and 90.77%， respectively， and the recognition accuracy rates of dicrotic waves f and g are 91.93% and 95.38% respectively..
Acta Photonica Sinica
- Publication Date: Dec. 25, 2020
- Vol. 49, Issue 12, 51 (2020)
Image Processing
An Optimization Method of Ghost Imaging Based on Multiple Speckle Patterns Combination-modulation
Xiao-xia WANG, Yong TAO, Feng-bao YANG, and Jiang-tao XI
A new optimization method of ghost imaging by combining multiple speckle patterns was proposed. Firstly， the multiple speckle patterns irradiated on the target object are sorted to reduce the difference between adjacent speckle patterns in the order of smallest to largest in the value of the bucket detector. Secondly， A new optimization method of ghost imaging by combining multiple speckle patterns was proposed. Firstly， the multiple speckle patterns irradiated on the target object are sorted to reduce the difference between adjacent speckle patterns in the order of smallest to largest in the value of the bucket detector. Secondly， the adjacent speckle patterns are combined to create a new speckle pattern， and the corresponding values of the bucket detector are modulated to a new bucket detector value. This process enables effectively reduce the redundancy and number of data to be associated. Finally， using three different correlation calculation rules to reconstruct of the target object. Numerical simulation results show that for the grayscale image， the proposed method with 4 000 measurements has a higher peak value than traditional ghost imaging， differential ghost imaging， and positive-negative ghost imaging under uncombined and modulated case. The peak signal-to-noise ratio/contrast has been improved by 21.7%/27.3%， 8.3%/17.8% and 14.7%/25.7%， respectively. Through the numerical simulation and result analysis of 20 target images，it is found that 90%/85% and 50%/55% of peak signal-to-noise ratio/contrast enhancement rates are above 15% and 30% respectively， and it shows that the proposed method has good universality and popularization value..
Acta Photonica Sinica
- Publication Date: Dec. 25, 2020
- Vol. 49, Issue 12, 226 (2020)
Imaging Systems
Optimization with Demodulation Algorithm for Spatially Modulated Full Polarization Imaging System
Sun-chen WANG, Lei ZHANG, Mo-gen XUE, Yun-zhi WU, Rong JIA, and Ying XUE
In order to optimize the two-dimensional Fourier transform demodulation in spatially modulated full polarization imaging system， Bessel's correction directional selective two-dimensional Hanning apodization optimal demodulation algorithm is proposed. The characteristics of main lobe width and sidelobe attenuation oIn order to optimize the two-dimensional Fourier transform demodulation in spatially modulated full polarization imaging system， Bessel's correction directional selective two-dimensional Hanning apodization optimal demodulation algorithm is proposed. The characteristics of main lobe width and sidelobe attenuation of different apodization functions are compared and analyzed. Compared with the traditional Hanning window， the proposed algorithm has a sidelobe suppression capability improved by 12.89 dB and a main lobe width of 0.065π. At the same time， it shows a good suppression effect on the diagonal spectrum information of the relative position in the spectrum filtering process. A system imaging simulation platform based on Jones matrix is built and verified by experiments. The experimental results show that the full polarization component demodulation accuracy of the optimized demodulation algorithm is improved by 9.48% on average， which verifies the accuracy and effectiveness of the optimized demodulation algorithm..
Acta Photonica Sinica
- Publication Date: Dec. 25, 2020
- Vol. 49, Issue 12, 146 (2020)
Simulation Research of Non-line-of-sight Imaging System Based on Bidirectional Reflectance Distribution Function
Wei-hao XU, Xiu-qin SU, Shu-chao WANG, Wen-hua ZHU, Song-mao CHEN, Ding-jie WANG, and Jing-yao WU
The Non-Line-Of-Sight （NLOS） imaging process was studied to figure out the performance of existing NLOS algorithms under different reflection characteristics， with adopting physically based rendering bidirectional reflectance distribution function. Two state-of-the-art algorithms named f-k algorithm and Light-Cone TranThe Non-Line-Of-Sight （NLOS） imaging process was studied to figure out the performance of existing NLOS algorithms under different reflection characteristics， with adopting physically based rendering bidirectional reflectance distribution function. Two state-of-the-art algorithms named f-k algorithm and Light-Cone Transform （LCT） algorithm are considered in the reconstruction using the proposed simulation system. The performance of the two algorithms are analyzed under various roughness， angles and niose. The simulation results show that： the change of reflection characteristics has a greater impact on the LCT algorithm； noise has a greater impact on the f-k algorithm. Based on the analysis of the experimental results， this article proposes an improvement to the f-k algorithm， merely using the phase information of the measured data for NLOS reconstruction. Improved algorithm is cpable to reconstruct target objects with different reflection characteristics， providing help for exploring further study..
Acta Photonica Sinica
- Publication Date: Dec. 25, 2020
- Vol. 49, Issue 12, 157 (2020)
Correction Method for the Wavelength Instability of Ptychography
Jian-tai DOU, You-you HU, and Zhong-ming YANG
If the known wavelength was inconsistent with the actual wavelength or the wavelength was shifted due to the wavelength instability， the reconstructed image would become fuzzy and the resolution of the image would be reduced. A piecewise correction method for the wavelength instability is proposed that is combined of tIf the known wavelength was inconsistent with the actual wavelength or the wavelength was shifted due to the wavelength instability， the reconstructed image would become fuzzy and the resolution of the image would be reduced. A piecewise correction method for the wavelength instability is proposed that is combined of the self-focusing method based on Tamura coefficient and ptychography， and it can correct the wavelength instability by changing the axial distance at different stages. Based on the Fresnel diffraction theory， we establish the model for the wavelength instability， and it points out that adjusting the axial distance can be used to correct the wavelength instability. The axial distance of each phase can be determined by the self-focusing method based on Tamura coefficient， and the new axial distance is taken into the next stage of the iterative calculation， until the difference between the adjacent two calculations of the axial distance meets the termination conditions. The last axial distance is again taken into the ptychography algorithm to correct the wavelength instability and obtain the distinct reconstructed image， and the correction accuracy is in the nanometer level. Simulation and experiment have proved the feasibility of the piecewise correction method for wavelength instability..
Acta Photonica Sinica
- Publication Date: Dec. 25, 2020
- Vol. 49, Issue 12, 170 (2020)
Instrumentation, Measurement and Metrology
Research on CNN Denoising Algorithm Based on an Improved Mathematical Model for the Measurement of Far-field Focal Spot
Zheng-zhou WANG, Li WANG, Meng TAN, Ya-xuan DUAN, Wei WANG, Xin-feng TIAN, and Ji-tong WEI
Aim at the shortcomings that the mathematical model for the measurement of far-field focal spot with high dynamic range does not consider the influence of noise on the measurement results， this paper optimizes the measurement method of far-field focal spot based on schlieren from three aspects. Firstly， the mathematicaAim at the shortcomings that the mathematical model for the measurement of far-field focal spot with high dynamic range does not consider the influence of noise on the measurement results， this paper optimizes the measurement method of far-field focal spot based on schlieren from three aspects. Firstly， the mathematical model for the measurement of far-field focal spot based on schlieren is improved， and the noise is added to the mathematical model， which makes the mathematical model match with the real experimental environment， and improves the practicability and theoretical support of the mathematical model； Secondly， the denoising algorithm based on Convolution Neural Network （DnCNN） is used in the de-noise processing of the main lobe and side lobe CCD image， and the original denoising algorithm is improved effectively in this paper， which can remove the noise of different levels （0~75 dB） of the mainlobe and sidelobe 12-bit images； Finally， the whole experimental process of far-field focal spot measurement is simulated， including light splitting， attenuation， adding noise， schlieren sphere occlusion， denoising， attenuation magnification， focal spot reconstruction， etc.， and the effective experimental results of reconstructed focal spot is obtained， which the correlation coefficient between the reconstructed and theoretical focal spot images is 0.998 9， and the error of dynamic range between the reconstructed and theoretical focal spot is 3.22%. The simulation results show that through the improvement of the mathematical model and the DnCNN denoising algorithm， the necessity of the improved mathematical model and the superior performance of the DnCNN denoising algorithm in improving the accuracy of the two-dimensional distribution and dynamic range of reconstructed focal spot are verified. The reliability of the measurement of far-field focal spot with high dynamic range based on schlieren is improved， and the accuracy and efficiency of the measurement of far-field focal spot in high dynamic range is met in the end..
Acta Photonica Sinica
- Publication Date: Dec. 25, 2020
- Vol. 49, Issue 12, 118 (2020)
An Effectiveness Evaluation Method for Space-based Optical Imaging Systems
Xiao-tian LU, Feng LI, Bian XIAO, Xue YANG, Lei XIN, Ming LU, and Zhi-jia LIU
A novel effectiveness evaluation method was proposed based on the Johnson criteria and minimum resolvable contrast to evaluate effectiveness. In this process， target and background contrast， atmospheric transmission， detectors， and human eyes， are considered comprehensively. The noise equivalent contrast is introduced A novel effectiveness evaluation method was proposed based on the Johnson criteria and minimum resolvable contrast to evaluate effectiveness. In this process， target and background contrast， atmospheric transmission， detectors， and human eyes， are considered comprehensively. The noise equivalent contrast is introduced to measure the noise level of the detector， and the detection efficiency is measured by the joint probability of contrast and resolution， which can quantitatively and intuitively evaluate the detection ability of space-based optical imaging system. Verification experiments are carried out based on aerial and GF-2 satellite images. In aerial images， the recognition probability of car is 46%， the identification probability of aircraft is 73%， and the NIIRS level is 4.23； in GF-2 satellite images， the recognition probability of truck is 67%， the detection probability of small ship is 63%， and the NIIRS level is 4.53. The results show that the probability calculated by our method is basically consistent with the subjective judgment of human eyes， which is basically consistent with the NIIRS. The results prove the effectiveness of the method. Our method is of great significance to the design of space-based imaging systems and the evaluation of the on-orbit satellite detection capability..
Acta Photonica Sinica
- Publication Date: Dec. 25, 2020
- Vol. 49, Issue 12, 138 (2020)
Lasers and Laser Optics
Calibration Method of 2D LIDAR and Camera Based on Indoor Structural Features
Lei ZHANG, Xiao-bin XU, Jia HE, Kai-yua ZHU, Min-zhou LUO, and Zhi-ying TAN
Aiming at the problem of LIDAR and camera data fusion， a calibration method of 2D LIDAR and color camera based on indoor structural features was proposed. According to the position relationship between the point and lines， pillar features of the indoor scene are used to derive the projection matrix equation between theAiming at the problem of LIDAR and camera data fusion， a calibration method of 2D LIDAR and color camera based on indoor structural features was proposed. According to the position relationship between the point and lines， pillar features of the indoor scene are used to derive the projection matrix equation between the 2D LIDAR and the camera coordinate systems. The Canny operator and Hough transform are employed to extract the line features of the corner image. Afterwards， the RANSAC method is used to fit the corner features from the point cloud. The projection matrix is solved by the singular value decomposition method. Finally， the calibration results are further optimized after removing the data with large reprojection errors. The experimental results show that the average reprojection error of the pillar feature point is reduced from 0.375 5 pixels to 0.045 9 pixels by adopting optimized projection matrix. Compared with the two-step calibration method， the algorithm proposed in this paper has a better reprojection effect. At the same time， this method does not require a specific calibration object， and can achieve high projection accuracy in less time..
Acta Photonica Sinica
- Publication Date: Dec. 25, 2020
- Vol. 49, Issue 12, 61 (2020)
Femtosecond Laser Ablation Characteristics of Gear Material 20CrMnTi
Xing-zu MING, Lei JIN, Yong-bo XIAO, Jia-jian LIN, Xian ZHOU, and Rui MING
The ablation mechanism of spiral bevel gear material 20CrMnTi and the ablation characteristics of tooth surface by monopulse femtosecond laser at different energy densities are studied. Considering the dynamic energy absorption effect of material and mutual coupling interaction of photon-electron-lattice system， the enThe ablation mechanism of spiral bevel gear material 20CrMnTi and the ablation characteristics of tooth surface by monopulse femtosecond laser at different energy densities are studied. Considering the dynamic energy absorption effect of material and mutual coupling interaction of photon-electron-lattice system， the energy coupling model is established. The simulation results show that the energy density of ablated gear material is at least 67 mJ/cm2， and the material removal occurs in the area within the ablation depth 40 nm. Experimental results show that when the tooth surface temperature exceeds the vaporization temperature of gear material， a good ablative morphology of tooth surface can be maintained， and the variation value of roughness is less than 0.021 μm， which verifies the effectiveness of theoretical simulation. These results could provide a reference for improving the tooth surface quality of spiral bevel gear with micro-precise machining of femtosecond laser..
Acta Photonica Sinica
- Publication Date: Dec. 25, 2020
- Vol. 49, Issue 12, 73 (2020)
Optical Devices
Concentration Performance Analysis of Solar Simulator Based on Compound Parabolic Concentrator
Hao WANG, Yue-gang FU, Guo-yu ZHANG, Gao-fei SUN, Shi LIU, Jian ZHANG, Da XU, Ling-hao WU, and Jun-jie YANG
To solve the problem of low irradiance caused by the low energy utilization rate of an existing solar simulator， a Compound Parabolic Concentrator （CPC） based on the basic imaging principle of the solar simulator was proposed to improve the concentrating system of the simulator. The condensing mechanism of the CPC and To solve the problem of low irradiance caused by the low energy utilization rate of an existing solar simulator， a Compound Parabolic Concentrator （CPC） based on the basic imaging principle of the solar simulator was proposed to improve the concentrating system of the simulator. The condensing mechanism of the CPC and a traditional condenser was analyzed， and the parameter design method of the CPC was derived based on the edge-ray principle. Using the LightTools software combined with a nested body light source and the CPC to build a condenser model， the ideal maximum receiving angle of the CPC was analyzed. A comparison model between the ellipsoidal condenser and the combined condenser system was established to verify the theoretical analysis. The optimal intercept ratio was obtained through an intercept analysis to optimize the initial structure and to determine the final structure of the CPC. Results show that the energy utilization rate of xenon lamps used in the CPC is as high as 94.86%. Furthermore， the irradiance of the entire solar simulator can be greatly improved. The findings of this study present a reference for designing highly energy efficient and high-irradiance solar simulators..
Acta Photonica Sinica
- Publication Date: Dec. 25, 2020
- Vol. 49, Issue 12, 1 (2020)
Study on Ionization Efficiency of Cesium Ion Source for Microchannel Plate Test
Ye-ping WANG, Yun-sheng QIAN, Yi-zheng LANG, Zi-heng WANG, and Xiang-yu KONG
In order to study the performance test technology of cesium ion bombarding microchanne plate， a cesium ion beam generator was used as an experimental device. To analyze the whole process of cesium ion beam generation and study the factors affecting the ionization efficiency of cesium plasma generated by cesium atom bomIn order to study the performance test technology of cesium ion bombarding microchanne plate， a cesium ion beam generator was used as an experimental device. To analyze the whole process of cesium ion beam generation and study the factors affecting the ionization efficiency of cesium plasma generated by cesium atom bombarding ionized filament （tantalum， with a desorption work of 4.12 eV）. From the physical process， it is found that the ionization efficiency is affected by the ionization environment temperature， the power of ionization filament and the focusing voltage. Combined with the of Saha-Langmuir equation， it is analyzed that the emitted ion current can be used as the actual characterization of the ionization efficiency. In the experiment， the ion current was measured by feedback current method of operational amplifier by changing the factors of ionization environment temperature and ionization filament power. The experimental results show that the number of cesium atoms can be kept stable by controlling the ionization environment temperature， and the ionization efficiency of cesium ion is greatly affected by the ionization environment temperature and the ionization filament power. When other working conditions remain unchanged， the ionization efficiency reaches the maximum when the ionization filament power Qc is 2.818 W； when the ionization environment temperature Tc is 110℃， the ionization process is stable and the most sufficient， and the maximum output ion current is about 25 nA. The experimental results are in good agreement with the theoretical model. By controlling these factors， the incident intensity of cesium ion beam can be stably adjusted..
Acta Photonica Sinica
- Publication Date: Dec. 25, 2020
- Vol. 49, Issue 12, 11 (2020)
Resolution Research of Low-light-level Image Intensifier Based on Electronic Trajectory Tracking
Ya-feng QIU, Wu-ling YAN, and Sang-tun HUA
Aiming at the problem that the current theoretical models for calculating the resolutions of low-light-level image intensifiers are not accurate enough and can’t provide the optimization conditions intuitively， a theoretical model based on electron tracking is proposed. Electron scattering formula of uniform-doping GaAAiming at the problem that the current theoretical models for calculating the resolutions of low-light-level image intensifiers are not accurate enough and can’t provide the optimization conditions intuitively， a theoretical model based on electron tracking is proposed. Electron scattering formula of uniform-doping GaAs photocathodes is used for obtainig the distribution of emitted electrons， which is different from the Lambertian distribution. The proximity system is approximated to a longitudinal uniform electric field to establish the electron transport model. Based on the secondary electron emission distribution， the electron transport model in the microchannel plate is established under non-abnormal working conditions. With the distribution of the electron beams on the phosphor screen， the modulation transfer function is calculated by Monte Carlo method， and the limiting resolution is obtained by taking the standard value as 0.3. The resolutions of four different types of image intensifiers are calculated， and the results show that the largest error between the model simulation results and the experimental results is only 5.0%， less than the errors from the existing models（more than 10%）， which proves the practical value and good application prospect of the model..
Acta Photonica Sinica
- Publication Date: Dec. 25, 2020
- Vol. 49, Issue 12, 19 (2020)
Research on Auto-split GaN-based Vertical Structure LED
Xu-liang SU, Can WANG, Lei-ying YING, Huan XU, Rong-bin XU, Yang MEI, Zhi-wei ZHENG, Hao LONG, and Bao-ping ZHANG
In order to solve the problem of damage to LED chip caused by inductively coupled plasma etching and substrate cutting， and improve the yield of devices， a new process for fabricating GaN-based vertical structure LED is proposed. The auto-split vertical structure LED without substrate cutting is successfully fabricatedIn order to solve the problem of damage to LED chip caused by inductively coupled plasma etching and substrate cutting， and improve the yield of devices， a new process for fabricating GaN-based vertical structure LED is proposed. The auto-split vertical structure LED without substrate cutting is successfully fabricated. In the process of device preparation， chemical mechanical polishing is used to reduce the thickness of n-GaN instead of inductively coupled plasma etching ， which avoids the damage to the side wall and active region of the device caused by inductively coupled plasma etching. The problem of substrate cutting is solved by temporary substrate transfer technology， and a single LED chip can be obtained without substrate cutting. Compared with the regular LED， the electrical characteristics of 300 μm × 300 μm auto-split vertical structure LED are greatly improved. The forward voltage at 20 mA decreases from 3.17 V to 2.88 V， which decreases by 9%； the saturation current increases from 240 mA to 280 mA， increasing by 17%. The influence of electrode shape on the device performance is studied. The electrode shape is changed from disk shape to ring shape， the saturation current of 500 μm × 500 μm auto-split vertical structure led is increased from 450 mA to 490 mA， which is increased by 9%. The performance of auto-split vertical structure LED is expected to be improved by optimizing the electrode structure..
Acta Photonica Sinica
- Publication Date: Dec. 25, 2020
- Vol. 49, Issue 12, 27 (2020)
Scattering
Approximate Model of Three-dimensional Clouds Multiple Scattering Based on Finitely Adjacent-cloud Radiative Transfer
Yin ZHANG, Jun MA, Jun-hua YAN, Hao YAN, Xi-yang ZHI, and Jin-nan GONG
In view of the high computational cost of radiative transfer for three-dimensional clouds in high-resolution detections， an approximate model of multiple scattering based on finitely adjacent-cloud was proposed. According to the radiative coupling law between adjacent clouds in different spatial positions， the finitelyIn view of the high computational cost of radiative transfer for three-dimensional clouds in high-resolution detections， an approximate model of multiple scattering based on finitely adjacent-cloud was proposed. According to the radiative coupling law between adjacent clouds in different spatial positions， the finitely adjacent-cloud was divided into horizontally and vertically adjacent fields of clouds. The equation of variation for horizontal flux density was introduced to calculate the horizontal radiation exchange， thus characterize the radiative effects between horizontally adjacent fields of clouds. Regarding the error of flux along vertical direction， the function of compensation for flux density was used to correct it to more accurately characterize the radiative effect caused by vertically adjacent fields of clouds. A three-dimensional field of cumulus was selected as experimental scene， and the independent pixel approximation and the multiple scattering （calculated by the Eddington’s approximation） which combined with standard single scattering were compared. Experimental results show that the proposed model can improve the accuracies of upward and downward source functions by up to 47.39% and 33.93%， and the improvements are more than 8% and 10% when solar zenith angle is less than 60°； under different illuminating and observing conditions， mean relative errors of intensity for the proposed model are less than 40%； in terms of computational efficiency， the proposed model has significant advantage， which is helpful to research the rapid solution of radiative transfer in large-scale scenarios..
Acta Photonica Sinica
- Publication Date: Dec. 25, 2020
- Vol. 49, Issue 12, 180 (2020)
Inversion of Multimodal Particle Size Distribution Based on the Artificial Bee Colony Algorithm
Liang SHAN, Hao-ran LI, Bo HONG, Dao-dang WANG, Ting-ting ZHA, and Ming KONG
This research proposes to use Artificial Bee Colony algorithm to realize the inversion of the multimodal distribution of the particle size of small angle forward scattering method based on Mie scattering theory. The inversions of uniform spherical particle systems which obeying normal distribution， Rosin-Rammler distriThis research proposes to use Artificial Bee Colony algorithm to realize the inversion of the multimodal distribution of the particle size of small angle forward scattering method based on Mie scattering theory. The inversions of uniform spherical particle systems which obeying normal distribution， Rosin-Rammler distribution or Johnson's SB distribution function were performed， and the particle group issimulated as unimodal， bimodal and trimodal distribution respectively. The particle size can be well inverted by the Artificial Bee Colony algorithm. In the case of unimodal distribution， the relative root mean square error of the particle weight frequency distribution curve can be as low as 3.53×10-8. The relative root mean square error of the particle weight frequency distribution curve of the wide bimodal distribution decreased from 3.38% and 2.70% to 1.53% when it's compared with the independent mode algorithm Philip-Twomey-NNLS and Chahine. The accuracy of the Artificial Bee Colony algorithm is higher， and as the number of peaks increases， the width of the distribution curve becomes narrower and the noise increases， the errors of the Philip-Twomey-NNLS algorithm and the Chahine algorithm increase to 44.99% and 24.36%， respectively， while the error of the Artificial Bee Colony algorithm is 18.22%. A particle measurement system based on small angle forward scattering method was constructed， and the scattering images of 35 μm particle group and 30μm and 51μm mixed particle group of national standard particles were collected for experimental study. The relative error of the characteristic particle diameter obtained by Artificial Bee Colony algorithm is within 5%， which is about 50% lower than that of Philip-Twomey-NNLS algorithm..
Acta Photonica Sinica
- Publication Date: Dec. 25, 2020
- Vol. 49, Issue 12, 191 (2020)
Study on Polarized Reflection Characteristics of Space Object Thermal Control Coatings
Kai WANG, Hong LIU, and Xiu-xing ZHANG
Focusing on the demand of polarized detection for space objects， the polarized characteristics of space object thermal control coatings are simulated based on three-component polarized Bidirectional Reflection Distribution Function （pBRDF）model， the reflected Stokes vector and Degree of Linear Polarization（DOLP） in pasFocusing on the demand of polarized detection for space objects， the polarized characteristics of space object thermal control coatings are simulated based on three-component polarized Bidirectional Reflection Distribution Function （pBRDF）model， the reflected Stokes vector and Degree of Linear Polarization（DOLP） in passive illustration condition are given， and the pBRDF matrix in active polarized detection is presented. The simulation and measurement of polarized characteristics of two typical space object thermal control coatings SR107 and S781 show the accuracy of three-component pBRDF model. The polarized properties of space object thermal coatings are analyzed with simulated and measured data. The conclusion of this paper presents important references for space object polarized detection applications..
Acta Photonica Sinica
- Publication Date: Dec. 25, 2020
- Vol. 49, Issue 12, 205 (2020)
Spectroscopy
Analysis of Influence of Spike on Phase Retrieval Accuracy of Doppler Asymmetric Spatial Heterodyne Spectrometer and Correction Method
Ting-ting YU, Yu-tao FENG, Di FU, Xuan WANG, Chen SUN, and Qing-lan BAI
The doppler asymmetric spatial heterodyne interferometer can be used to retrieve the atmospheric wind speed by measuring the phase frequency shift of interference fringes. Because of the interference from cosmic rays and “hot pixels” in CCD， some spikes that have random location and intensity occur on the interferogramThe doppler asymmetric spatial heterodyne interferometer can be used to retrieve the atmospheric wind speed by measuring the phase frequency shift of interference fringes. Because of the interference from cosmic rays and “hot pixels” in CCD， some spikes that have random location and intensity occur on the interferogram. The presence of such spikes can seriously affect the accuracy of wind speed retrieval. In this paper， the theoretical influence of various parameters of spike on the phase inversion accuracy of doppler asymmetric spatial heterodyne interferometer is discussed， and the spike correction method is proposed. Based on the characteristics of the spike and the phase retrieval model of doppler asymmetric spatial heterodyne interferometer， a theoretical model between the phase error and the intensity and position of the spike is established. The influence of the intensity， position and width of the spike on the phase retrieval accuracy is analyzed and verified by experiments. The results show that the phase retrieval error varies periodically with the position of the spike， and is positively correlated with the intensity and peak width of spike. A new method of spike correction based on nearest neighbor comparison and windowed median filter is proposed. The new method can effectively correct the spike without affecting the original interference data. The phase error caused by the spike after correction is reduced by more than 90%， which will help to improve the accuracy of subsequent interference data processing..
Acta Photonica Sinica
- Publication Date: Dec. 25, 2020
- Vol. 49, Issue 12, 83 (2020)
High Precision Temperature Control Design for TDLAS Gas Detection System
Xu LIU, Peng-shuai SUN, Xi YANG, Tao PANG, Hua XIA, Bian WU, Zhi-rong ZHANG, Zhi-feng SHU, and Chi-min SHU
According to the structure of gas cavity and the properties of optical components， an accurate circuit control method of constant temperature and stability control box is designed， and the high-precision stability control of multi-temperature state inside the box is realized.The temperature control system can be used tAccording to the structure of gas cavity and the properties of optical components， an accurate circuit control method of constant temperature and stability control box is designed， and the high-precision stability control of multi-temperature state inside the box is realized.The temperature control system can be used to study the variation of gas temperature and gas absorption spectrum parameters， and improve the detection accuracy of gas concentration.The hardware circuit system including high-precision constant-current source， two-channel temperature sampling module and conditioning circuit， A/D analog-digital conversion circuit and semiconductor refrigerator control module is designed.The corresponding system software is developed to ensure the uniformity of the temperature of the optical cavity.According to the actual temperature control box parameters， with the proportional integral differential control algorithm as the core， the temperature change inside the optical cavity is precisely controlled， realizing the optimal temperature change control fluctuation inside the temperature control box is ±0.009 ℃ and the standard deviation is lower than 0.006 ℃.Temperature control experiments are carried out under seven temperature states of 16 ℃， 20 ℃， 24 ℃， 28 ℃， 32 ℃， 36 ℃ and 40 ℃ respectively using CO2 standard gas with a concentration of 2.00%. The stability of the temperature control system is verified through the measurement results..
Acta Photonica Sinica
- Publication Date: Dec. 25, 2020
- Vol. 49, Issue 12, 93 (2020)
Baseline Fitting Algorithm of Spectral Signal Region
Cheng-bin YAO, Yun-wei JIA, Jiang-bo WU, Kun WANG, and Chen-xiang HAO
A baseline fitting algorithm for spectral signal region is proposed in order to eliminate the adverse effects of baseline distortion in spectral processing. First， a GradSuck fitting algorithm is proposed for baseline with abrupt curvature by using the idea of gradient inertia force and suction， which cover the shortagA baseline fitting algorithm for spectral signal region is proposed in order to eliminate the adverse effects of baseline distortion in spectral processing. First， a GradSuck fitting algorithm is proposed for baseline with abrupt curvature by using the idea of gradient inertia force and suction， which cover the shortage of the piecewise quadratic polynomial fitting algorithm when the baseline curvature around the signal area changes suddenly. Then this algorithm is combined with the piecewise quadratic polynomial fitting algorithm to propose a more general fitting algorithm for spectral signal region. At the same time， the proposed algorithm has been compared with different baselines fitting algorithms. Experiments under various baseline types with different SNR show that the baseline fitting algorithm of signal region has reliable accuracy and stability， and it can extract the spectral baseline better than other algorithms. The relative error of its whole fitting accuracy is only 47.0% of the quadratic polynomial fitting， 35.6% of the AirPLS fitting， and 20% of the wavelet fitting. And it also has high real-time performance because of only fitting the baseline of the signal region..
Acta Photonica Sinica
- Publication Date: Dec. 25, 2020
- Vol. 49, Issue 12, 105 (2020)
Thin Films
Development of Polycarbonate High Strength Ultra-low Reflectivity Film
Dong-mei LIU, Bo-yang WEI, Xiu-hua FU, Jing ZHANG, Suo-tao DONG, and Shuang LI
In order to reduce the problem of image quality degradation caused by stray light in the optical system， polycarbonate is used as the substrate and the electron beam ion assisted method is used to prepare the ultra-low attenuation reflective film in visible band. Vacuum annealing method was used to reduce the thermal tIn order to reduce the problem of image quality degradation caused by stray light in the optical system， polycarbonate is used as the substrate and the electron beam ion assisted method is used to prepare the ultra-low attenuation reflective film in visible band. Vacuum annealing method was used to reduce the thermal tensile stress caused by the increase of substrate temperature in the coating process， and MATLAB software was used to fit and analyze the stress of the material. By studying the ion source deposition process， the problem of film cracking was solved. MATLAB simulation was used to adjust the control parameters of Proportion Integration Differentiation（PID） controller ， so as to stabilize the film-forming rate and solve the problem of spectral drift caused by thickness error. The results show that the absolute reflectance of the film is less than 0.15% at 430 ~ 700 nm..
Acta Photonica Sinica
- Publication Date: Dec. 25, 2020
- Vol. 49, Issue 12, 216 (2020)
© Copyright 2018-2021 | Chinese Laser Press. All Rights Reserved 沪ICP备15018463号-20