2023

• Record 325 of
  
  Title:Optical design of a continuous zoom MWIR lens system with large field of view
  
  Author(s):Xiaopeng, Wei(1,2); Liang, Xu(1); Jinwei, Zhao(1); Shaobo, Geng(1)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 12935  Issue: null  Article Number: 1293505  DOI: 10.1117/12.2692193  Published: 2023  
  Abstract:The aberration characteristics change with the relative position changes of zoom groups has been a key problem for continuous zoom lens design, especially those with large target surfaces. To diminish the aberration, in this study, we took a Positive-Negative-Positive-Positive（PNPP）Mechanical structure for optical compensation, and developed a continuous zoom MWIR lens system with 20x magnification. The system used a cooled detector with a large target surface of 1280×1024 pixel and a 12μm pixel size, which improved observing capability under a 66.5° field of view. We tested the transfer function of the system at Nyquist frequency, which is close to the diffraction limit in a 15~300mm zoom range and the full field of view. We further evaluated our system by ray tracing analysis, pressure angle analysis of the cam curve, and de-focusing amount analysis under a temperature range of -45℃ to +70℃. Results show that our system has a good suppression capability for cold reflection, high image quality under extreme thermal conditions, and a smooth zoom curve. © 2023 SPIE.
  Accession Number: 20235015220825
• Record 326 of
  
  Title:Lanthanide Composite as Doping Reagent for Fiber Preforms on Simplifying and Uniformizing the Deposition of Er/Yb Co-Doped Fiber Preform
  
  Author(s):Huang, Qing(1); Zhang, Yuting(2); She, Shengfei(2); Fan, Wei(1); Hou, Chaoqi(2); Xu, Hai-Bing(1)
  Source: SSRN  Volume: null  Issue: null  Article Number: null  DOI: 10.2139/ssrn.4540762  Published: August 28, 2023  
  Abstract:Controlling the volatilization and diffusion of co-dopants to afford uniform distribution of co-doping lanthanide elements with appropriate concentration, is crucial to Er/Yb co-doped fiber performs. Herein, volatile and thermostable lanthanide composite Yb0.95Er0.05(THMD)3 is demonstrated to practicably regulate the doping concentration by the fixed Yb/Er molar ratio in the formation, and suitable for continuous deposition with simply one raw material transfer line for both Yb and Er elements. Beneficial from more uniform distributions and higher Yb → Er energy transfer efficiency, stronger ErIII-based emission of the Er/Yb co-doped fiber preforms in similar content prepared with Yb0.95Er0.05(THMD)3 than that with traditional Yb(THMD)3/Er(THMD)3 is achieved. This work highlights the critical role of lanthanide composite in simplifying and uniformizing the deposition of lanthanide doped fiber preforms and the great potential of high-quality thin-film material for future (opto)electronics. © 2023, The Authors. All rights reserved.
  Accession Number: 20230294343
• Record 327 of
  
  Title:Hilbert transformation deep learning network for single-shot moiré profilometry
  
  Author(s):Ma, Pu(1); Du, Hubing(1); Ma, Yueyang(1); Zhang, Gaopeng(2); Wang, Feng(2); Zhao, Zixin(3); Feng, Leijie(1)
  Source: Optics and Lasers in Engineering  Volume: 160  Issue: null  Article Number: 107279  DOI: 10.1016/j.optlaseng.2022.107279  Published: January 2023  
  Abstract:Phase demodulation from a single moiré fringe pattern is an ill-posed inverse problem that limits the applications of moiré profilometry in dynamic three-dimensional (3D) measurement. In this paper, a deep-learning-based high-precision technique is used to solve this problem arising from highly under sampled inputs. Our novel approach termed two-dimensional (2D) Hilbert transformation network uses two Res U-Net networks paired with a dichotomous network to generate the desired quadrature fringe pattern by referring to the input. This process can be viewed as 2D Hilbert transformation of a fringe pattern. By using the proposed network, the wrapped phase can be extracted easily if the sampled fringe pattern is filtered and normalized in advance. Experimental results obtained using the proposed Hilbert transformation network trained on simulated data indicate that it is a simple, albeit robust solution for phase extraction from a single fringe pattern with a phase error of less than 0.02 rad. Thus, the proposed network represents a novel approach to reliable and practical learning-based single-shot Moiré profilometry. © 2022 Elsevier Ltd
  Accession Number: 20223812765181
• Record 328 of
  
  Title:A high accuracy assembling method of R-C system based on reverse optimization method
  
  Author(s):Yin, Yamei(1); Liu, Yong(1); Hou, Xiaohua(1); Wang, Peng(1)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 12976  Issue: null  Article Number: 129761V  DOI: 10.1117/12.3009535  Published: 2023  
  Abstract:R-C optical systems have been widely used in long focal length imaging and long-distance detection fields such as aerospace, remote sensing, exploration, and space optical communication. However, the significant wavefront aberration in the edge fields of R-C optical system always restrict the imaging system in a small field of view. In this paper, the improved R-C optical system is composed of two reflective mirrors as well as three refractive elements, which can correct off-Axis aberrations in large fields of view, enable the large field of view imaging. For the high accuracy assembly, optical centering assembling technology based on optical imaging principle is applied to ensure the coaxiality between the optical axis of optical element and the rotation axis of corresponding machine part. And the reverse optimization method is carried out to compensated the wavefront aberration introduced by misalignment errors. Finally, the testing optimization result of system wavefront aberration with RMS value of center of view is 0.045λ (λ=0.6328nm), and the RMS value of off-Axis field better than 0.08λ can be achieved. © COPYRIGHT SPIE.
  Accession Number: 20240315402128
• Record 329 of
  
  Title:Freeform surface compensation design for machining error of primary mirror
  
  Author(s):Huang, Cheng(1); Xie, Yongjun(1); Mao, Xianglong(1)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 12617  Issue: null  Article Number: 1261775  DOI: 10.1117/12.2666802  Published: 2023  
  Abstract:Considering the demand of high-resolution imaging and dark targets detection, large-aperture space telescopes have always been the most direct tool for human observation of the universe. However, limited by the capability of current optical manufacturing equipment, the difficulty, cycle and cost of fabricating the primary mirror increase significantly as the optical surface aperture increased, and the accuracy requirements of the mirror are also closely related. In order to reduce the machining accuracy requirements, a freeform optical wavefront compensation method was proposed to increase the tolerance on the manufacturing error of the primary mirror. In this paper, we compensated two different large aperture telescope systems, and one of their mirrors were replaced by freeform surfaces represented by 37-term Zernike fringe polynomials in the optical system to correct the system wavefront distortion caused by the machining error of the large-aperture primary mirror. A new algorithm that is based on the principle of equal optical path and ray tracing was adopted here for the construction of freeform surfaces. The design results proved the superiority of the compensation method and the new algorithm of freeform surface. The machining accuracy demand was reduced by more than one order of magnitude, and high-quality imaging of the optical system was realized with the low-precision primary mirror. © 2023 SPIE.
  Accession Number: 20232114130375
• Record 330 of
  
  Title:Study on optimization method of multi-point combined adhesive process for optical plane mirror
  
  Author(s):Xiang-Ke, Zheng(1); Shi-Fa, Kang(1); Hua, Li(1); Peng, Wang(1); Xiaoyan, Li(1); Lin-Sen, Shu(2)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 12507  Issue: null  Article Number: 1250718  DOI: 10.1117/12.2655549  Published: 2023  
  Abstract:In order to quickly obtain the optimal bonding styles in the adhesive bonded mirror, the simulation and experimental study of the adhesive bonding assembly process for plane mirror were carried out. A single-factor experiment was designed to study the variation of the PV and RMS values of the surface-shape of optical plane mirror with the change of various factors. Then, an orthogonal experiment was designed to study the optimal parameters for the optimal bonding process by taking the PV and RMS of the surface-shape as comprehensive indexes. A finite element model named "Mirror-Adhesive -Frame" was developed using ANSYS Parametric Design Language (APDL) to calculate the PV and RMS values of the surface-shape of the mirror after bonding. In addition, a interference instrument named ZYGO is used to verify the correctness of the surface shape from simulation. The results show that the prediction results of the developed simulation model are in good agreement with the measurement results. The values of surface shape index PV and RMS increase with the increase of adhesive layer diameter and thickness, and gradually decrease with the increase of adhesive layer position in R direction and H direction.The orthogonal experiment with four factors and three levels revealed that the diameter of adhesive layer is the main factor to change the shape of the surface. The optimal process parameters are as follows: adhesive layer diameter of Φ4mm, adhesive layer thickness of 0.1 mm. adhesive layer position in R-direction of 40 mm and adhesive layer position in H-direction of 9.5mm. © 2023 SPIE. All rights reserved.
  Accession Number: 20230613538012
• Record 331 of
  
  Title:High-Accurate Quantitative Phase Imaging Based on the Transport of Intensity Equation and Wavelet Transform
  
  Author(s):Fan, Chen(1); Zhao, Hong(1); Zhao, Zixin(1); Li, Junxiang(1); Du, Yijun(1); Zhang, Gaopeng(2)
  Source: IEEE Transactions on Instrumentation and Measurement  Volume: 72  Issue: null  Article Number: 7004211  DOI: 10.1109/TIM.2023.3280499  Published: 2023  
  Abstract:We propose a high-accurate quantitative phase imaging (QPI) method by using transport of intensity equation (TIE) and wavelet transform (WT). TIE provides a simple and fast method for QPI, but its accuracy is always limited due to the nonlinear error and noise problems caused by the defocus distance. To improve the accuracy of the phase recovered by TIE, WT is introduced to combine with TIE under several defocus distances. With the help of the multiresolution characteristics of the WT, effective information can be extracted from the phases retrieved with TIE at different defocus distances. As a result, a more accurate phase can be obtained by fusing this effective information. Moreover, to extend the applicability of our method, the problems of phase discrepancy and phase singularity in TIE are discussed and solved with an iterative WT-TIE algorithm. Numerical simulations and experiments with various types of phase maps are presented to comprehensively demonstrate the accuracy and effectiveness of our method. © 1963-2012 IEEE.
  Accession Number: 20232314199727
• Record 332 of
  
  Title:Scattering Model for Stray Light Calculations in Laser Interferometry Application to TianQin Science Interferometer
  
  Author(s):Yan, Haoyu(1,2); Chen, Qinfang(1); Wang, Hu(1,2); Wang, Xingyan(1,2); Ma, Zhanpeng(1,2)
  Source: Journal of Physics: Conference Series  Volume: 2464  Issue: 1  Article Number: 012008  DOI: 10.1088/1742-6596/2464/1/012008  Published: 2023  
  Abstract:In the field of space optics, correct estimation of the amount of stray light is necessary to evaluate system performance and guide the selection of the correct design. Given the noise target of several picometers on distance measurements, this configuration is very sensitive to stray-light noise; thus, stray-light estimation is an important part of the design process. For complex optical systems, stray-light simulations can be performed by using specific optical analysis software (FRED, Tracepro, ASAP), which require expensive licenses and excessive computing time. Herein, we consider the effects of combined roughness, mirror contamination, and surface imperfections, construct a unified physical scattering model and simulate it. According to the analysis, the stray light of the telescope system is less than 1010 of the outgoing laser power.These considerations apply to various optical systems. © Published under licence by IOP Publishing Ltd.
  Accession Number: 20231613905077
• Record 333 of
  
  Title:Multi-scale Remote Sensing Image Classification Based on Weighted Feature Fusion
  
  Author(s):Cheng, Yinzhu(1,2); Liu, Song(1,2); Wang, Nan(1,2); Shi, Yuetian(1,2); Zhang, Geng(1)
  Source: Guangzi Xuebao/Acta Photonica Sinica  Volume: 52  Issue: 11  Article Number: 1110002  DOI: 10.3788/gzxb20235211.1110002  Published: November 2023  
  Abstract:Remote sensing image classification is a key branch in remote sensing image processing，which provides an important basis for agricultural，industrial，and military applications. With the development of remote sensing satellite，spectral imaging technique has also developed from multi-spectral technology to hyperspectral technology. Rich spectral information puts forward higher requirements for remote sensing image classification. Many hyperspectral image classification algorithms based on traditional methods，such as superpixel methods， extended morphological feature methods， space-spectral joint classification algorithms based on combined kernels，and classification algorithms based on support vector machines and graph cuts，have achieved certain results. In recent years，benefiting from the improvement of hardware conditions and the update and iteration of algorithms，various deep learning methods have emerged one after another，and have been introduced into the field of hyperspectral image classification by researchers，further improving the accuracy of hyperspectral classification. Autoencoder，Convolutional Neural Network （CNN），and capsule neural network have all been experimentally verified to be effective in this field. Different from the common two-dimensional convolutional neural network，the convolution kernel of the three-dimensional convolutional neural network（3D CNN）is a cube，which can naturally integrate the features of spatial dimension and spectral dimension，and has achieved state-of-the-art performance in the field of remote sensing image classification. Conventional 3D CNN usually extracts data cube features from a single scale，which often loses certain local information；excessively increasing the depth of the model will lead to overfitting problems；limited by actual conditions，it is often difficult to obtain hyperspectral data with a large number of labels，while conventional 3D CNN does not perform well for few-sample situations （for example，the total sample size is only a few hundred）. To solve these problems，a multi-branch 3D CNN is proposed in this paper，and the three branches are designed with three different 3D CNN structures. For the input hyperspectral data image set，this paper first utilizes the principal component analysis method to reduce the dimensionality of the data，and the dimensionality of the spectral dimension is selected as 40 after dimensionality reduction. The data cube is decomposed into many 19× 19×40 image patches，and the label of its central pixel is used as the label of the image patch，and then the method of rotating 90 degrees，180 degrees，and 270 degrees is introduced for data augmentation. In the feature extraction stage，a three-dimensional convolutional neural network connected in parallel with three branches is employed to extract features from three spatial scales of 2×2，4×4，and 6×6. In the training phase，Adam optimizer is used to optimize the parameters of the three branches，respectively，and the cross-entropy loss function is adopted. In order to alleviate overfitting，the dropout unit and Batch Normalization are introduced. In the test phase，the features extracted from the three branches are combined by weighted connection，and the optimal weighting coefficient is optimized by utilizing simulated annealing algorithm. In terms of classifiers， the logistic regression classifier is adopted， which has performance not inferior to fully connected neural networks for small-sized and medium-sized data sets. In order to verify the effectiveness of the method in this paper，10% of the labeled data were used for training on public datasets such as Indian Pines，Pavia University，and Salinas，the overall accuracy of 98.60%，99.83%，and 99.97% were respectively obtained. Our method outperforms the comparative methods such as support vector machine，2D CNN，and conventional 3D CNN. Moreover，the overall accuracy of the method in this paper is studied when the amount of data in the training phase gradually decreases，and compared with the single-branch 3D CNN with data augmentation，multi-branch 3D CNN without data augmentation，single-branch 3D CNN without data augmentation. The method in this paper is also compared with the DAMA and DBDA methods in the case of a few samples. Compared with the comparison method，the performance of the method in this paper still maintains a high classification accuracy when the sample size is small. In addition，a practical test was carried out using the method in this paper. A series of experimental results show that compared with various comparison methods，the method proposed in this paper has a good classification accuracy and has high application value for hyperspectral image classification problems. © 2023 Chinese Optical Society. All rights reserved.
  Accession Number: 20235015214385
• Record 334 of
  
  Title:Design of MWIR hyperspectral imagers based on acousto-optic tunable filters
  
  Author(s):Li, Xijie(1,2); Gao, Ming(1); Liu, Jun(1); Li, Yong(2); Feng, Yutao(2)
  Source: Optik  Volume: 276  Issue: null  Article Number: 170636  DOI: 10.1016/j.ijleo.2023.170636  Published: April 2023  
  Abstract:Thermal infrared hyperspectral imagers have significant application values in the field of space optics. However, it is very difficult to obtain the spectral data cube and temperature field information of fast moving targets in a short time. An acousto-optic tunable filter (AOTF) has many advantages, such as fast tuning speed, light weight and no moving parts. It can obtain thermal infrared hyperspectral images of a fast-moving target in a very short integration time. In this paper, a collimating optical system is obtained by splicing optical path a telescope and a secondary imaging mirror. A middle wavelength infrared (MWIR) AOTF is introduced into the collimating optical system to modulate the spectrum and obtain thermal infrared hyperspectral images. The system with a focal length of 18 mm, a relative aperture of 1/2, a field of view (FOV) of 8°, a spectral resolution of 30.08 nm at 4 µm and a 100% cold diaphragm efficiency achieving is taken as a design example. The design results show that the modulation transfer function (MTF) of the system is greater than 0.6 at the Nyquist space frequency of 17 lp/mm, and the imaging quality is close to the diffraction limit. Finally, we develop a prototype of MWIR hyperspectral imager based on AOTFs and do experiments to prove its feasibility. © 2023 Elsevier GmbH
  Accession Number: 20230613558963
• Record 335 of
  
  Title:Stable Structure of a Near-infrared Doppler Asymmetric Spatial Heterodyne Interferometer
  
  Author(s):Sun, Jian(1,2); Feng, Yutao(1); Chang, Chenguang(1,2); Wang, Wei(1); Li, Juan(1); Hu, Bingliang(1)
  Source: Guangzi Xuebao/Acta Photonica Sinica  Volume: 52  Issue: 11  Article Number: 1122001  DOI: 10.3788/gzxb20235211.1122001  Published: November 2023  
  Abstract:The mounting for a space-borne Doppler Asymmetric Spatial Heterodyne （DASH）interferometer，which is a key part of the space-borne DASH wind instrument，should be able to withstand the mechanical and thermal conditions of being space-borne. As spectral resolution increases，the size of the DASH interferometer increases. The stable rugged support structure for a large-sized interferometer has become a key issue. By far，the vast majority of the vibrational energy is produced at lower frequencies. Therefore，in order to improve mechanical performance，an effort can be made to ensure that the lowest natural frequency of the mounting structure is as high as possible. In existing approaches，the natural frequency of the assembly can be increased by increasing the adhesive area. However，the（metal-to-glass）gluing surface tension breaks during the vibration tests because of the lower natural frequency. In this paper，a novel，and stable support structure is proposed，with its effectiveness exemplified for a Near-Infrared （NIR） DASH interferometer. Based on the principle of DASH interferometer technique，the materials and dimensions of the optical components were selected to compensate for the phase shift at the fringes as the arms expand with temperature，which improves the optical components' thermal stability. The mathematical model of a structure was established，and the detail optimization process was designed. Parameters affecting the spring constants were analyzed. The parameters of the structure were optimized by requiring the maximum mechanical stress of the structure and maximum shear stress at the gluing surface to be less than the strength value. The spring constants were designed to adjust the natural frequency of the DASH interferometer assembly and improve the mechanical stability. The mathematical model results show that the lower spring is much stiffer than the top spring. The maximum shear stress of the structure was 48 MPa. The maximum shear stress at the gluing surface was 1.4 MPa. The bending deformations of the gluing surfaces were less than 1 μm. The Finite Element Analysis （FEA） results show that the maximum stresses of mechanical components and optical components were 65.56 MPa and 0.56 MPa，which are less than the tensile strength of the material. The maximum shear stress at metal-to-glass gluing surfaces was 3.4 MPa. The safety margin was 3.4. The maximum shear stress at the glass-to-glass gluing surface was 0.16 MPa. The safety margin was 83.3. All values have a high safety margin. The FEA results were consistent with the model calculation results. As the DASH interferometer is thermally stabilized about 5 ℃ above the wind instrument temperature，the Finite Element Model（FEM）of the DASH interferometer assembly was established to analyze the thermal stability. Under the environmental temperature change of 5 ℃ ，the Surface Shape Error （RMS） of beam splitters was 1.671 nm. The interferogram distortion caused by thermal stress can be ignored. The vibration test results indicate that the relative error of natural frequencies between the FEM and sine sweep test was less than 4%. The results from FEA and vibration tests agree with the model calculation results. The optical results indicate that the fringe frequency did not change（the number of fringes is 50）before and after the vibration test，which directly reveals that there was no breakage in the gluing surfaces（metal-to-glass gluing and glass-to-glass gluing），and the interferometer assembly remained undamaged. The phase shift was caused by the location accuracy of the DASH interferometer assembly in the optical system. Compared with existing methods，the mechanical performance was improved. The proposed structure can meet the requirements of the launch environment. Moreover， the proposed design of the stable support structure can be used in other interferometers. And the structure was used to mount a short infrared wave DASH interferometer，which is larger than NIR DASH interferometer. © 2023 Chinese Optical Society. All rights reserved.
  Accession Number: 20235015214276
• Record 336 of
  
  Title:Design of two-color cold infrared optical system
  
  Author(s):Wang, Chenfeng(1,2); Wang, Xiaowei(1); Lu, Weiguo(1)
  Source: Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering  Volume: 52  Issue: 12  Article Number: 20230297  DOI: 10.3788/IRLA20230297  Published: December 2023  
  Abstract:Objective For the current space environment single infrared band detection target false alarm rate is high, low sensitivity and other challenges, a double_color infrared optical system design method based on cold optical technology is proposed. The front optical path of the optical system adopts a common aperture structure, and the spectral band splitting is performed by a splitting plate, and the cold apparatus matching is realized by the secondary image of the relay mirror in order to ensure the light miniaturization of the system. In order to enhance the detection sensitivity of the long_wavelength system, a cold optical design is carried out to reduce the impact of the system's own radiation of detection performance. The working wavelengths are 3.7_4.8 μm and 7.9_9.3 μm, the F_number is 1.2, the total dimension of the optical structure is 260 mm×150 mm×80 mm, the aberration of the medium_wavelength system is less than 2.8%, about 82% of the energy is concentrated in a pixel of the detector, and the aberration of the long_wavelength system is less than 0.33%, about 70% of the energy is concentrated in one image element of the detector. The system can detect dim space targets at a long distance, and has the advantages of low false alarm rate, high sensitivity and compact structure. Methods The common optical systems included refractive, reflective and reflexive, and the different optical structures have their unique advantages and disadvantages. Refractive systems have no center obscuration and high efficiency, but the variety of optical materials is small and not easy to correct chromatic aberration. Secondary image system is easy to match the cold screen, the optical components are small in size and light in weight, but the number of pieces is more. After comprehensive consideration, the refractive secondary image system is selected. Results and Discussions According to the design index of infrared optical system and the design principle of light miniaturization and high energy transmission rate, it is decided to choose refractive secondary imaging system as the initial structure. The front optical path of the system adopts a common aperture type structure, and then the spectroscopic plate is used for spectroscopy, and the relay mirror set adopts the secondary imaging method to realize the cold apparatus matching and ensure the compactness of the system. In the process of system design optimization, aspheric surface is introduced to correct the aberration. The aberration of the medium_ wavelength system is less than 2.8%, and about 82% of the energy is concentrated in one image element of the detector, while the aberration of the long_wavelength system is less than 0.33%, and about 70% of the energy is concentrated in one image element of the detector. Each mirror of the medium_wavelength system and long_ wavelength system meets the requirements of the system cold reflection. After setting a reasonable tolerance value, the system image quality still meets the use requirements. After the completion of processing and assembly, the experimental verification, the system detection distance meets the expected target, to meet the design requirements. Conclusions As the demand for space target detection grows, multi_band detection will become one of the future directions of infrared detection technology. A cold dual_color infrared detection system is designed in the paper. Through experimental verification, the detection capability of the system meets the expected target. © 2023 Chinese Society of Astronautics. All rights reserved.
  Accession Number: 20241115748252