Imaging Systems|33 Article(s)
Technique of Adaptive Dynamic Imaging Quality Compensation for Dynamic Optics Working for High-speed Aircraft
LI Yan, HU Bin, and ZHUANG Xu-xia
Confronted with the requirement of the high resolution earth-observation system of high-speed aircraft working in near-space environment,and the imaging system with dynamic optical windows is likely to suffer from extreme dynamic aberration,complex imaging quality compensators and bad real-time character,the traditional imaging quality compensation was improved and the adaptive optical (AO) technique was explored as a novel way of solving the problems.The image sharping function optimization closed-loop adaptive wavefront correction algorithm was used.Simulations results indicate that the correction method can make the PV (peak to valley) waves of the Zernike aberration term in reduce to about 17.5% and the RMS spot radius to about 10.61% less than before correction the system which has 60°FOR (field of regard).By correction with this method,the residual aberration is much less than the baseline system and the imaging performance can be almost diffraction limited.
Acta Photonica Sinica
  • Publication Date: Feb. 01, 2015
  • Vol. 44, Issue 2, 211001 (2015)
Non-Parallel System Underwater Image Transformation Model
ZHANG Wen-ming, DENG Xi-xue, ZHANG Qiang, and LI Hai-bin
In order to solve the problem of image distortion of the three-dimensional reconstruction underwater, a model based on the non-parallel binocular stereo vision system was proposed, which could transfer the image shooted through a plat waterproof cover underwater into the image shoted in air, and general conditions were presented to use it. When the focus of lens is on the surface of the water, there is a one-to-one correspondence between the underwater image and the image-without-water. If the focus of lens is outside the water, the proposed model still valid when the distance from the focus to the object is far greater than the focal length and the distance from the focus of lens to refractive surface along z axis. Three-dimensional reconstruction of the feature points was used in experiments to verify the validity of the model. The results show that with the mentioned method, the average coordinate errors of the feature points are 2.23%(x), 1.51%(y), 1.10%(z), respectively, compared with the actual one. The proposed model provides a basis of applying the three-dimensional image reconstruction.
Acta Photonica Sinica
  • Publication Date: Feb. 01, 2015
  • Vol. 44, Issue 2, 211002 (2015)
Infrared Image Sequence Complexity Analysis Based on Multi-attribute Decision Making
QIAO Li-yong, XU Li-xin, and GAO Min
To analyse the influences of infrared sequence complexity on the target tracking performance, the infrared sequence complexity evaluation had been modeled as a multi-attribute decision making problem. The each frame complexity of the infrared sequence had been evaluated with seven image metrics based on the modified technique for order preference by similarity to ideal solution method and entropy weights. The whole infrared image sequence complexity had been evaluated with three metrics based on weighted summation method and entropy weights. The normalized correlation template matching algorithm, basic mean shift algorithm, and the variance ratio algorithm had been used to implement tracking experiments. Infrared sequences with different complexity had beed used to validate the effectiveness of the presented infrared sequence evaluation method. The experiments showed that: the proposed infrared sequence complexity evaluation solution could truly indicate the differences of the tracking task difficulties for diverse infrared sequences, there was strong correlation with the tracking performance, and could accurately reflect the major influencing factors for target tracking task.
Acta Photonica Sinica
  • Publication Date: Mar. 01, 2015
  • Vol. 44, Issue 3, 311001 (2015)
Separable Compressive Imaging with Deterministic Matrices
ZHANG Cheng, CHENG Hong, ZHANG Fen, and WEI Sui
Aiming at the heavy difficulty or high cost for the random orthogonal matrix which used in separable compressive sensing for high-dimensional signals sensing, such as large-scale image compressive reconstruction, deterministic measurement matrices was introduced, and a separable compressive sensing using deterministic matrices was proposed, matrix with deterministic structure, such as Toeplitz or Circulant matrix, could be used as a left/right separable matrix in separable compressed sensing. The proposed scheme can significantly reduce the number of independent elements, thus significantly reduce the difficulty and the cost of physical implementation. Numerical simulations evaluated comparisons of reconstruction performance of the proposed method with different downsampling rates and different image sizes. The results indicate that the proposed method can achieve similar reconstruction quality with far fewer independent elements as random orthogonal matrix′s, which demonstrates the feasibility of the proposed method.
Acta Photonica Sinica
  • Publication Date: Mar. 01, 2015
  • Vol. 44, Issue 3, 311003 (2015)
Point Spread Function of Pinhole Imaging System for Deviating from Center of Incident γ-Ray
MA Qing-li, TANG Shi-biao, and WU Yan-hua
The Point Spread Function(PSF) of a pinhole imaging system for γ-Ray has been studied through Monte Carlo method.The PSFs under 0, 0.5, 1, 1.5 and 2 pixel bias five different conditions have been obtained and analyzed by fitting the simulating data with Gauss function, the corresponding Modulation Transfer Function(MTF) can be obtained, and the spatial resolutions under these five conditions are compared.As the results show, when the excursion is little, the PSF′ deviation obtained by Gauss function fitting will be less and can meet the requirement of accuracy, but when the excursion is larger, the fitting deviation will be more. In addition, a ideal baffle between pinhole and detector will reduce the error and improve the spatial resolution remarkably.
Acta Photonica Sinica
  • Publication Date: Mar. 01, 2015
  • Vol. 44, Issue 3, 311004 (2015)
Design of the Probe of Swept Source Optical Coherence Tomography for Endoscopic Imaging
BIAN Hai-yi, Gao Wan-rong, and LIAO Jiu-ling
A swept source endoscopic optical coherence tomography system was designed with the grin-lens, single mode fiber and fiber optic rotary joint for endoscopic imaging. The effects of the pitch of the grin lens and the distance between the single mode fiber and the grin-lens on system performance were then analyzed with Zemax. The object distance of 0.7 mm was chosen according to the diameter of esophagus and the Pitch of 0.24P was chosen according to the cost and the effects analyzed above. The measurement results shown that the axial resolution of the system is ~9 μm and the lateral resolution is ~19.5 μm with the imaging depth of 6 mm in air. The working distance of the probe is about 7 mm. The initial cross-sectional images of the intestinal tract of pig were presented to demonstrate the capability of the system for endoscopic applications. And all these results demonstrated that the probe designed is suitable for endoscopic imaging of esophagus.
Acta Photonica Sinica
  • Publication Date: Sep. 01, 2016
  • Vol. 45, Issue 9, 911001 (2016)
Intensity Spread Function Analysis of Single Compressive Sensing Ghost Imaging
CHEN Yi, FAN Xiang, CHENG Yu-bao, CHENG Zheng-dong, and LIANG Zhen-yu
In order to improve imaging quality of the single compressive sensing ghost imaging and reduce the internal and external interference, the intensity spread function analysis of single compressive sensing ghost imaging was proposed. The imaging process was analyzed based on the principle of single compressive sensing ghost imaging. It is found that Fresnel diffraction and atmospheric turbulence are main causes which result in poor imaging quality. Aiming at these two factors, the formulas of intensity spread function were derived, and the influence of focal length to aperture lens ratio and source wavelength on ghost imaging were studied. Simulation results of single compressive sensing ghost imaging indicate that the effects of diffraction can be restrained by using the projection lens with the ratio of focal length and aperture in the range of 2~5. Besides, the short wavelength is suitable for imaging under the weak atmospheric turbulence. By contrast, the long wavelength is a better choice for imaging under strong atmospheric turbulence. The experiment verifies the conclusions of simulation. Therefore, the proposed method is effective to improve imaging quality and optimize the imaging system.
Acta Photonica Sinica
  • Publication Date: Sep. 01, 2016
  • Vol. 45, Issue 9, 916002 (2016)
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 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 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)