Contents
2025
Volume: 51 Issue 2
19 Article(s)
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Passive Non-line-of-sight imaging with known window shape
SUN Jiake, and WANG Weidong
Non-Line-of-Sight imaging is the imaging of scenes outside the line of sight, which can be divided into active Non-Line-of-Sight imaging and passive Non-Line-of-Sight imaging. Active Non-Line-of-Sight imaging uses active light sources and detectors to image Non-Line-of-Sight scenes. Passive Non-Line-of-Sight imaging reNon-Line-of-Sight imaging is the imaging of scenes outside the line of sight, which can be divided into active Non-Line-of-Sight imaging and passive Non-Line-of-Sight imaging. Active Non-Line-of-Sight imaging uses active light sources and detectors to image Non-Line-of-Sight scenes. Passive Non-Line-of-Sight imaging relies on the light emitted or reflected from the scene, using objects, corners and windows to image the Non-Line-of-Sight scene. The existing methods of passive Non-Line-of-Sight imaging using windows are only for rectangular windows, and need to know the shape, scale and position of the window. However, in real life, windows have different shapes, and it is difficult to know their specific scale and position. Therefore, a passive Non-Line-of-Sight imaging method with known window shapes is proposed. Firstly, analyze the formation principle of the diffuse reflection image of the Non-Line-of-Sight scene illuminated through the window onto the diffuse reflection surface, and construct the model. Secondly, a series of windows with different scales are selected based on the known window shape to construct the visual matrix, and the L0 gradient sparse constraint is used to solve it. Select the window scale corresponding to the minimum mean square error as the final window scale. Finally, refine the window, and optimize the scene and window jointly to obtain the final reconstructed scene. Experimental results show that for windows with different shapes, the proposed method can reconstruct Non-Line-of-Sight scenes when only the shapes of windows known and realize the Non-Line-of-Sight imaging. Compared with other methods, the average PSNR of the reconstructed imaging results is increased by 0.461dB, and the average SSIM is increased by 0.0361..
Optical Technique
- Publication Date: Apr. 22, 2025
- Vol. 51, Issue 2, 129 (2025)
Total variation and FastDVDNet based reconstruction method for compressed ultrafast photography
LONG Jiale, LI Yingrong, DING Yi, MA Zhao, ZHANG Jianmin, and XU Bin
Using compressed ultrafast photography, it is promising to reveal the transient scattering process of femtosecond laser pulses in a medium with very high temporal resolution. However, based on the two-step iterative shrinkage/thresholding algorithm (Two-step Iterative Shrinkage/Thresholding (TwIST) based compressed ultUsing compressed ultrafast photography, it is promising to reveal the transient scattering process of femtosecond laser pulses in a medium with very high temporal resolution. However, based on the two-step iterative shrinkage/thresholding algorithm (Two-step Iterative Shrinkage/Thresholding (TwIST) based compressed ultrafast camera reconstruction suffers from poor image reconstruction quality and unstable results due to the ultra-high data compression rate caused by the under sampling strategy. To overcome these problems, a method is proposed in which the use of Total Variation (TV) combined with a deep denoising network (FastDVDNet) is alternated as a plug-and-play generalized alternating projection frame reconstruction algorithm to improve the image quality of compressed ultrafast photography.Experimental results show that the algorithm proposed in this paper can significantly improve the reconstruction quality of ultrafast image sequences compared to the traditional two-step iterative shrinkage/thresholding algorithm..
Optical Technique
- Publication Date: Apr. 22, 2025
- Vol. 51, Issue 2, 136 (2025)
Reconstruction of non-viewing objects based on BRDF and NIQE
WANG Yufeng, and SUI Guorong
To address the issues of the optical transmission model being incomplete and the reconstruction algorithm parameters being unclear in passive non-line-of-sight (NLOS) target reconstruction, this study proposes an optical transmission model based on BRDF and a NIQE-integrated FISTA algorithm. The optical transmission moTo address the issues of the optical transmission model being incomplete and the reconstruction algorithm parameters being unclear in passive non-line-of-sight (NLOS) target reconstruction, this study proposes an optical transmission model based on BRDF and a NIQE-integrated FISTA algorithm. The optical transmission model for passive NLOS scenarios is established based on BRDF, discretized, and formulated into an objective function comprising data fidelity and smoothness terms. NIQE is employed as an indicator to integrate with the FISTA iterative algorithm to solve the optimization problem, yielding the optimal reconstruction results. In the reconstruction of the MNIST handwritten digit dataset, the PSNR reached 11.34 dB, and the SSIM was 0.79. Compared to polarization-enhanced methods, the PSNR of the reconstructed target improved by 96.92%, and the SSIM increased by 83.72%. Compared to deep learning methods, the PSNR increased by 74.26%, and the SSIM reached 95.18%. This approach effectively enhances the performance of passive NLOS target reconstruction..
Optical Technique
- Publication Date: Apr. 22, 2025
- Vol. 51, Issue 2, 141 (2025)
Discrete cosine transform-based single-pixel imaging method using ESPCN
PAN Jian, LONG Jiale, ZHANG Jianmin, LI Zaiming, and HUANG Haoming
Single-pixel imaging is a technology that reconstructs images by measuring with a small number of pixels, possessing high flexibility. since each pixel is measured indirectly, the image reconstruction quality may not be as good as traditional direct imaging techniques. A single-pixel imaging method that combines the DiSingle-pixel imaging is a technology that reconstructs images by measuring with a small number of pixels, possessing high flexibility. since each pixel is measured indirectly, the image reconstruction quality may not be as good as traditional direct imaging techniques. A single-pixel imaging method that combines the Discrete Cosine Transform (DCT) with an Efficient Sub-Pixel Convolutional Neural Network (ESPCN) is proposed. By using DCT to perform frequency domain decomposition on a small number of pixel measurements, low resolution frequency domain feature representations are obtained while preserving key frequency information. ESPCN maps low-frequency features to high-resolution images through sub-pixel convolutional layers, thereby achieving high-quality reconstruction. Simulation results show that the improved network not only enhances the signal-to-noise ratio and structural similarity of the image but also effectively improves the resolution, proving the feasibility of the network in practical applications..
Optical Technique
- Publication Date: Apr. 22, 2025
- Vol. 51, Issue 2, 153 (2025)
Research on residual aberration suppression method of conformal dome by wavefront coding
LIN Lin, ZOU Bolin, ZHANG Jialiang, ZHU Chonghui, YU Jiaqian, and SUN Chaofan
The conformal dome has good aerodynamic performance. However, the dynamic aberrations that change with the look angle will be introduced due to the structural characteristics of the conformal dome, resulting in the image quality degradation of the conformal optical system. To solve this problem, a method of suppressingThe conformal dome has good aerodynamic performance. However, the dynamic aberrations that change with the look angle will be introduced due to the structural characteristics of the conformal dome, resulting in the image quality degradation of the conformal optical system. To solve this problem, a method of suppressing the remaining aberrations of the conformal dome using wavefront coding technique is proposed. The dynamic aberrations of the conformal dome are initially corrected by designing a traditional aspherical fixed corrector, and then a well-designed phase mask is inserted into the exit pupil plane of the conformal optical system to suppress the residual aberrations. The feasibility of this method is verified by PSF, Strehl ratio, and image simulation. The design results show that the method can effectively reduce the number of optical elements and has good aberration elimination effect..
Optical Technique
- Publication Date: Apr. 22, 2025
- Vol. 51, Issue 2, 159 (2025)
Design method for freeform surface reflectors based on grid sag
LIN Yihua, LI Gang, XU Weilong, YAN Dong, and ZHAO Yixuan
Freeform surfaces play an important role in compact and complex optical systems. The design and description methods of freeform surfaces are key to their applications. A freeform surface design method based on grid sag is proposed by this paper, with light rays being taken as the research object and imaging optics beinFreeform surfaces play an important role in compact and complex optical systems. The design and description methods of freeform surfaces are key to their applications. A freeform surface design method based on grid sag is proposed by this paper, with light rays being taken as the research object and imaging optics being combined with non-imaging optics. Non-imaging theory is used to calculate the coordinates of discrete points on the freeform surface, which are then fitted to form a base surface. The deviation between the discrete points and the base surface is set as the compensation amount. Subsequently, imaging optical theory is employed to optimize both the base surface and the compensation amount simultaneously,until the system design requirements are met. Using this method, an optical shaping system with a freeform surface reflector is designed, achieving illuminance uniformity of over 90% and distortion of less than 2%. This method can be applied to the design of freeform surfaces in non-imaging fields such as tunnel lighting, automotive lighting, and photovoltaic concentrating systems, as well as in imaging systems with large field of view, off-axis, and ultra-short throw projection system..
Optical Technique
- Publication Date: Apr. 22, 2025
- Vol. 51, Issue 2, 164 (2025)
Long wave infrared interferometer applied to gradient refractive index measurement
ZHANG Youcheng, ZHENG Donghui, HUANG Yifei, LI Jingjing, and CHEN Lei
The infrared gradient refractive index material has a large refractive index and a large refractive index variation, resulting in a high density and density variation of interference fringes. In order to accurately measure the infrared gradient refractive index material, a =10.6 m infrared Mach Zehnder interferometer wThe infrared gradient refractive index material has a large refractive index and a large refractive index variation, resulting in a high density and density variation of interference fringes. In order to accurately measure the infrared gradient refractive index material, a λ=10.6 μm infrared Mach Zehnder interferometer was studied, and a zoom and fixed focus synchronous imaging scheme was designed to solve the difficult measurement problem caused by dense stripes in the case of large gradient distribution of materials. The refractive index distribution of infrared gradient refractive index materials was obtained by measuring the transmitted wavefront. Using this interferometer, the axial gradient refractive index sample with a thickness of 2mm and the radial gradient refractive index sample with a thickness of 9mm were measured, and the refractive index changes of the two samples were obtained to be 0.305 and 0.053, respectively. Using this interferometer to measure the infrared gradient refractive index sample, the maximum steepness of the sample's refractive index change is 0.035. To verify the measurement accuracy of the interferometer, the transmitted wavefront of a 10mm thick silicon wafer was measured, and the results showed that the refractive index measurement error was in the range of 10-5..
Optical Technique
- Publication Date: Apr. 22, 2025
- Vol. 51, Issue 2, 169 (2025)
Ultra-low stray light coaxial four-mirror optical system
SANG Hailong, ZHENG Yang, LI Yanwei, XIE Xinwang, XIE Hongbo, and LUI Huaqui
To meet the demands for lightweight and miniaturized satellite remote sensing payloads, based on the theory of primary aberrations in coaxial four-mirror reflective optical systems, an even asphere mirror is used to design a large-field, long-focal-length coaxial four-mirror reflective imaging system. The system has a To meet the demands for lightweight and miniaturized satellite remote sensing payloads, based on the theory of primary aberrations in coaxial four-mirror reflective optical systems, an even asphere mirror is used to design a large-field, long-focal-length coaxial four-mirror reflective imaging system. The system has a field of view of ±2.5°, a focal length of 550mm, and a total length of 210mm. The Modulation Transfer Function (MTF) exceeds 0.2 at 100lp/mm, with a maximum distortion of 0.7% within a ±2.5° field of view and 0.27% within a ±1.5° field of view. Compared to traditional coaxial optical systems with a ±1.5° field of view, the monolithic processing of the main four mirrors simplifies assembly and significantly reduces stray light. Comparative analysis shows that, within the same field of view, stray light is reduced by 81% compared to traditional coaxial four-mirror reflective optical systems. This system can reduce design complexity and system weight, providing valuable reference for the design of future satellite remote sensing optical systems..
Optical Technique
- Publication Date: Apr. 22, 2025
- Vol. 51, Issue 2, 175 (2025)
Design of image-side telecentric microscope with dual fields of view based on a single moving group
YANG Yuxia, and WANG Yanyun
To address the issue of high-precision cross scale detection in precision manufacturing industries such as chips and aviation components, a dual-field-of-view image-side telecentric microscope based on a single moving group is proposed. Firstly, a theoretical analysis is conducted on the imaging principle of the variabTo address the issue of high-precision cross scale detection in precision manufacturing industries such as chips and aviation components, a dual-field-of-view image-side telecentric microscope based on a single moving group is proposed. Firstly, a theoretical analysis is conducted on the imaging principle of the variable magnification microscope optical system, and a mathematical model for image-side telecentric variable magnification imaging based on a single moving group is established. Then, based on the variable magnification imaging model, a calculation method for the initial structure of the optical system is proposed, and the initial structure of the optical system has been calculated. Finally, using optical design software Zemax for lens replacement and optimization design, a common-aperture dual-field image-side telecentric microscope optical system has been obtained. The working spectrum of the microscope optical system is 1000~1700nm, with a magnification ratio of 4×, a working distance of 50mm, and a maximum object-resolution of 4.2μm. The analysis results show that the image-side telecentric error of the optical system is less than 2.0mrad, and the microscope optical system has the advantages of good imaging quality, low distortion, and simple zoom structure..
Optical Technique
- Publication Date: Apr. 22, 2025
- Vol. 51, Issue 2, 183 (2025)
Analytical study of the thermal effect of Gaussian pulsed laser ablation on titanium alloys
JIANG Yongxia, LI Long, CHENG Yulu, YU Tianxi, WEN Junyao, and ZHANG Chunling
Numerical simulation calculation of the thermal effect of laser acting on metal material TC4 material is carried out by using multi-physics field coupling analysis software, and a two-dimensional axisymmetric transient physical model of Gaussian distributed pulsed laser acting on TC4 material at a single point is constNumerical simulation calculation of the thermal effect of laser acting on metal material TC4 material is carried out by using multi-physics field coupling analysis software, and a two-dimensional axisymmetric transient physical model of Gaussian distributed pulsed laser acting on TC4 material at a single point is constructed from the theory of heat conduction and a theoretical model of the distribution of the temperature field of laser processing on the surface of titanium alloy is established. By discussing the laser processing mechanism and physical phenomena mainly occurring in laser ablation of metal surfaces, the theoretical model of laser ablation of metal material surfaces as well as the heat conduction equations for solving the temperature field distribution of the material are established, and studied by finite element simulation, and the results of the influences of the spot radius, laser power, and laser pulse width on the thermal effect of the surface of the titanium alloy are obtained, and the resultant surface is in the range of the spot radius of 0.3mm, the laser The results show that the surface is better processed when the spot radius is 0.3mm, the laser power is 1500W and the pulse width is 5000ns. This study provides a theoretical basis for the next finite element simulation and experimental research on the surface laser processing of titanium alloy..
Optical Technique
- Publication Date: Apr. 22, 2025
- Vol. 51, Issue 2, 189 (2025)
The factors influencing the efficiency of holmium laser on stone ablation
CHEN Minghui, XU Shiyi, TAN Weijie, WANG Hongwang, WANG Yuanzhu, WANG Cheng, and XIANG Huazhong
In order to improve the efficiency of Holmium laser lithotripsy and reduce the operation time, the influence of the peak power of Holmium laser pulse, optical fiber core diameter and working distance on the efficiency of Holmium laser ablation was investigated. First, an in vitro model device was built to simulate the In order to improve the efficiency of Holmium laser lithotripsy and reduce the operation time, the influence of the peak power of Holmium laser pulse, optical fiber core diameter and working distance on the efficiency of Holmium laser ablation was investigated. First, an in vitro model device was built to simulate the process of Holmium laser lithotripsy in the ureter. In the experiment, a 250mg cube plaster model was used to replace human stones. Then, the parameters required for the experiment were determined. The optical power of the Holmium laser was 10W, 12W, 20W and 24W, pulse duration is 200μs and 800μs. Optical fiber uses fiber of core diameter of 272μm and 550μm, working distance is from 0mm to 4mm. The results show that the Holmium laser ablation efficiency increases with the increase of the pulse peak power. When the pulse energy is 2J, the Holmium laser lithotripsy efficiency is the highest at 1.4mg/s and when the pulse energy is 0.5J, the Holmium laser lithotripsy efficiency is the lowest at 0.1667mg/s. Short pulse width ablates 35.72~86.68% more calculus quality than long pulse width. Fiber core diameter does not affect the ablation efficiency significantly. As the working distance increases, the ablation efficiency will decrease. The laser will not ablate when the distance from the stone model is 3mm. The experimental results will be useful for clinical treatment and refined of domestic Holmium laser parameters..
Optical Technique
- Publication Date: Apr. 22, 2025
- Vol. 51, Issue 2, 196 (2025)
Design of balanced code encoding and decoding for indoor positioning optical communication
YAO Dichang, LUAN Xinyuan, and AI Jiaming
Visible Light Communication (VLC) positioning technology holds great potential and application prospects in the field of wireless communication. To enhance the efficiency and broaden the application scope of VLC for indoor positioning, a balanced code encoding and decoding system for optical communication-based indoor Visible Light Communication (VLC) positioning technology holds great potential and application prospects in the field of wireless communication. To enhance the efficiency and broaden the application scope of VLC for indoor positioning, a balanced code encoding and decoding system for optical communication-based indoor positioning are proposed. The system first develops a light barcode encoding system based on the characteristics of LED lamps, leveraging the periodic characteristics of optical signals for data transmission. Subsequently, the advanced YOLOv8 algorithm is introduced to accurately locate the cyclic visible light codes emitted, enabling accurate capture of the coding period. Additionally, a decoding algorithm incorporating skew correction and error correction techniques is designed to optimize the decoding process of the located images, thereby improving data accuracy and stability. Experimental results show that the YOLOv8-based image recognition system can quickly and accurately identify and decode the encoded signals emitted by LED lamps, with an average recognition time of 0.324 seconds. The decoding efficiency is doubled compared to traditional methods. This approach significantly enhances and extends the performance of VLC-based indoor positioning systems, showing promising potential for future automation systems and contributing to technological advancements in related industries..
Optical Technique
- Publication Date: Apr. 22, 2025
- Vol. 51, Issue 2, 203 (2025)
CO2 spectroscopy measurement based on dual femtosecond optical frequency combs
LI Ketai, LI Xiaofeng, XIA Chuanqing, WU Tengfei, YANG Yongjun, and CAI Jing
The CO2 concentration measurement technique based on near-infrared dual-comb spectroscopy is investigated. The experiment utilized two femtosecond frequency combs with a central wavelength of 1550nm, constructing a dual-comb spectroscopy system through precise locking technology, and selected the CO2 absorption spectraThe CO2 concentration measurement technique based on near-infrared dual-comb spectroscopy is investigated. The experiment utilized two femtosecond frequency combs with a central wavelength of 1550nm, constructing a dual-comb spectroscopy system through precise locking technology, and selected the CO2 absorption spectral line at 1572nm for measurement. The results show a measurement error of 4.27% for CO2 concentration, with a spectral resolution of 113MHz. The study confirms the feasibility of the dual-comb system in near-infrared CO2 measurement and discusses methods to enhance measurement accuracy, providing significant reference value for the development of ultrafast laser spectroscopy technology..
Optical Technique
- Publication Date: Apr. 22, 2025
- Vol. 51, Issue 2, 218 (2025)
Characterization of porosity in low-permeability sandstone reservoirs using terahertz imaging
MIAO Xinyang, XIONG Shujie, AN Tiantian, LIU Xuecong, and ZHAO Kun
This study utilized reflection terahertz (THz) spectroscopic imaging technology and petrological characteristics to investigate the pore distribution in 10 tight sandstone samples from different well locations and depths, focusing on the Fuyu oil reservoir in the Songliao Basin. The results showed significant variationThis study utilized reflection terahertz (THz) spectroscopic imaging technology and petrological characteristics to investigate the pore distribution in 10 tight sandstone samples from different well locations and depths, focusing on the Fuyu oil reservoir in the Songliao Basin. The results showed significant variations in THz reflectivity due to non-uniform pore distribution. By employing a BP neural network, accurate quantification of porosity was achieved, along with the development of an evaluation model based on effective medium theory for measuring porosity levels. This approach enabled quantitative analysis of overall porosity and visualization of pore distribution within samples, providing valuable insights into reservoir fluid flow mechanisms and optimization of exploitation plan designs..
Optical Technique
- Publication Date: Apr. 22, 2025
- Vol. 51, Issue 2, 225 (2025)
Robot movement tracking measurement system based on photogrammetry
XIA Changqing, WU Long, PENG Wenjun, and Lu Guanhan
How to improve the fusion accuracy of measurement range and multi-position measurement data is the key to realize high precision measurement of large components. A mobile robot tracking measurement visual tracking system based on photogrammetry is designed to realize the fusion of multi-position measurement data with lHow to improve the fusion accuracy of measurement range and multi-position measurement data is the key to realize high precision measurement of large components. A mobile robot tracking measurement visual tracking system based on photogrammetry is designed to realize the fusion of multi-position measurement data with large precision and complete the measurement of high-speed train body. Specifically, aiming at the problem that the high-speed train body size is up to 25m×4m×4m and the range of single measuring equipment is limited, this system realizes the measurement of a wide range of the system through the robot grasping structural light equipment and guide rail to move the robot. In order to achieve high-precision measurement data fusion in multi-position pose, the system uses multiple monocular cameras to track the movement of measurement cameras, realizing rapid measurement data in multi-position pose and accurately aligning the tracking data to the same coordinate system. The system and laser tracker T-Scan measuring system are respectively used to measure the size of the door, and the experiment verifies that the measuring accuracy of the designed measuring system is equivalent to that of the laser tracker T-Scan measuring system..
Optical Technique
- Publication Date: Apr. 22, 2025
- Vol. 51, Issue 2, 233 (2025)
Fusion of LiDAR point cloud and monocular vision for variable height target height measurement
DENG Longbao, CHEN Maolin, PAN Jianping, and JI Cuicui
Traditional monocular vision altimetry methods generally have limitations in terms of the camera's setup orientation and lack sufficient research on the height measurement of off-ground objects. To address this issue, an innovative height measurement method is proposed. The proposed method integrates LiDAR point clTraditional monocular vision altimetry methods generally have limitations in terms of the camera's setup orientation and lack sufficient research on the height measurement of off-ground objects. To address this issue, an innovative height measurement method is proposed. The proposed method integrates LiDAR point clouds and monocular vision technology, uses geometric imaging as its theoretical foundation, incorporates prior knowledge from the point cloud data of the measured target, and applies geometric transformations to measure the height of objects on arbitrary planes. Additionally, it can accurately monitor the height of objects over time. A Xiaomi smartphone (model Xiaomi 13) was used as the experimental device, and the heights of five prisms were adjusted and measured over three rounds of testing. The experimental results indicate that the maximum relative error for a single prism is 6.559%, with an average error of 4.064%. For other target objects in the experimental environment, the height measurement accuracy reaches 98.043%..
Optical Technique
- Publication Date: Apr. 22, 2025
- Vol. 51, Issue 2, 240 (2025)
The effect of defocus error on phase diversity wavefront sensing and its solution
YU Rihui, HU Xinqi, FU Dexuan, and LI Bingchen
The classic phase diversity method in wavefront sensing, which utilizes defocusing as a means of phase diversity, necessitates precise knowledge of the defocus amount, a requirement often difficult to meet in numerous applications and thereby hindering its practical usage. Addressing the issue of potential defocus erroThe classic phase diversity method in wavefront sensing, which utilizes defocusing as a means of phase diversity, necessitates precise knowledge of the defocus amount, a requirement often difficult to meet in numerous applications and thereby hindering its practical usage. Addressing the issue of potential defocus errors encountered in practical applications, conducts a simulation analysis on the effect of the defocus amount errors on the accuracy of the classic phase diversity method in wavefront sensing was conducted, as well as its effect on the error evaluation function. Consequently, a defocus amount search algorithm based on the error evaluation function is proposed to solve the problem of inaccuracies in defocus, enhancing usability in practice. This paper also verified and analyzed the feasibility and performance level of the method through extensive simulation and statistical analysis..
Optical Technique
- Publication Date: Apr. 22, 2025
- Vol. 51, Issue 2, 247 (2025)
Thin-film ellipsometry measurement based on Fourier infrared spectroscopy
WU Chuanchao, SU Hongjin, ZHANG Zhixiang, ZHANG Jiaying, XUE Peng, and ZHANG Rui
With the development of the semiconductor integrated circuit, flat panel display, and photovoltaic solar energy etc. Thin film materials with excellent optical properties in infrared band are widely used in many fields. If the film thickness of these infrared thin-film can be measured with high precision and speed, it With the development of the semiconductor integrated circuit, flat panel display, and photovoltaic solar energy etc. Thin film materials with excellent optical properties in infrared band are widely used in many fields. If the film thickness of these infrared thin-film can be measured with high precision and speed, it is of great significance for improving performance of products. As a best means of film detection, the technology of spectral ellipsometry is with the features of non-contact, non-destructive, high-precision, and multi-parameter measurement. However, the existing spectroscopic ellipsometry cannot meet the requirements for the measurement of optical films in the infrared band. For this purpose, a technology of thin-film ellipsometry measurement based on Fourier infrared spectroscopy is proposed .According to the technical principle, an infrared ellipsometer with wavelength range of 2100~ 3200nm is established. The feasibility and accuracy of the ellipsometer are verified by testing standard SiO2 - Si sample with different thicknesses. The results show that the measurement accuracy of thin-film thickness is±0.5nm in the range of 2100~3200nm, the thickness repeatability measurement accuracy is 0.07nm, and the single point measurement time is approximately 1min..
Optical Technique
- Publication Date: Apr. 22, 2025
- Vol. 51, Issue 2, 252 (2025)
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