Debonding Defect Identification Method for Multi-layer Bonded Structures Based on LDA-CPSO-SVM Optimization
ZHENG Li, LIU Chuang, REN Jiaojiao, ZHANG Dandan, LI Lijuan, and XU Jisheng
Terahertz time domain spectroscopy and support vector machine algorithm are combined to study the defect identification method for multilayer bonded structures. On the one hand, the linear discriminant analysis method was used to reduce the dimension of 14 terahertz time-domain characteristic parameters extracted by the terahertz time-domain spectrum system, and the classification accuracy of normal region, debonding region and edge region in the adhesive layer of multi-layer bonded structure was improved by 20.3%. On the other hand, chaos particle swarm optimization was used to optimize the kernel function of support vector machine, and the classification accuracy of adhesive layer Ⅰ and Ⅱ increased by 18.92% and 9.85% respectively. Linear discriminant analysis based on constructed after parameter optimization of chaotic particle swarm optimization algorithm of support vector machine for multilayer glue joint structure characteristic imaging, the results show that this imaging method can effectively distinguish between sub area of the normal, defect region and edges region, compared with the traditional characteristics of terahertz single imaging technology promoted the debonding defect recognition rate of 50% above,The recognition rate of adhesive layer Ⅰ is 91% and that of adhesive layer Ⅱ is 92%, which greatly improves the recognition ability of debonding defects of multi-layer adhesive structure.
  • Jan. 25, 2022
  • Acta Photonica Sinica
  • Vol.50 Issue, 12 1212004 (2021)
  • DOI:10.3788/gzxb20215012.1212004
Tracking Performance Evaluation Method of Photoelectric Theodolite Based on Video Signal Injection
HU Linting, LI Peijun, LI Dawei, and ZHU Minpeng
Aiming at the limitation of the current target tracking performance evaluation method of photoelectric theodolite, an improved video signal injection test method is proposed based on the advantages of traditional optical signal injection test method. Firstly, according to the planned trajectory of the target during the test, the spatial mapping relationship between the target and the optical axis of the theodolite is calculated, and the corresponding target image and background image are generated, which are projected to the photoelectric theodolite by the target simulator, so as to establish the database for target and background image respectively. Secondly, according to the spatial position of the target as well as the spatial mapping relationship between the target and the optical axis of the theodolite at each measurement time, the target image and the background image in the image database are called. The target image is blurred according to the relative motion speed of the target, and then fused with the scene image, and injected into the video processor of the theodolite, so as to realize the tracking performance test of the theodolite with no-delay signal injection. The experimental results show that, the proposed video signal injection test method can achieve the measurement accuracy of outfield evaluation. It not only makes full use of the advantages of traditional optical signal injection test method, but also effectively solves the problems of the target simulator's projection delay and the need to follow the theodolite. It provides a new and effective way for tracking performance evaluation of photoelectric theodolite.
  • Jan. 25, 2022
  • Acta Photonica Sinica
  • Vol.50 Issue, 12 1212003 (2021)
  • DOI:10.3788/gzxb20215012.1212003
Application of Optical Flow Field in Out-of-plane Displacement Measurement for Optical Fiber Material
ZHAO Ran, WANG Yanan, LI Miao, LIU Bo, SUN Yong, ZHANG Yang, and JIA Jinsheng
In order to monitor the micro-scale deformation of optical fiber material during industrial production, image wedge model is built and then a out-of-plane displacement measurement technique based on optical flow field is proposed. The experimental apparatus consists of an optical microscope with an industrial camera and a holder with a fixed image inverter and the deformation can be loaded by tilting the holder. First, 2D images before and after deformation are captured through microscope with CCD camera. Subsequently, the optical flow field between two images is obtained by Brox optical flow algorithm. Finally, according to the image wedge model, the out-of-plane displacement field between two images is extracted from the optical flow field and the results of experiment are analysed as well. The experimental results indicate that the absolute errors and the relative errors of the measurement by optical microscope with magnification of 50× are less than 0.1 μm and 1.5%, respectively. The displacement measurement can be completed by two consecutive frames which obtained by only one optical microscope with a industrial camera. The proposed method is appropriate for dynamic deformation monitoring and industrial in-situ detection and it neither need conversion of the images to frequency domain, also do not need phase envelope operation during the out-of-plane displacement extraction process. Due to the low errors, it has been applied to the industrial uniformity and micro-nano-scale deformation monitoring of optical fiber image transmission materials.
  • Jan. 25, 2022
  • Acta Photonica Sinica
  • Vol.50 Issue, 12 1212002 (2021)
  • DOI:10.3788/gzxb20215012.1212002
Scanning Angle Compensation of MEMS Mirror Applied in Monocular 3D Camera
YU Huijun, LI Xiaoguang, and SHEN Wenjiang
In order to improve the measurement accuracy and repeatability of monocular vision camera, a closed-loop control method for the scanning mirror in laser scanning projection is proposed to improve the stability of the projected fringe position. The closed-loop control is carried out by using the feedback signal provided by the piezoresistive sensor integrated on the scanning mirror. At the same time, according to the temperature characteristic of piezoresistive sensor, a test system is designed to calibrate the relationship between piezoresistive output and temperature. By recording the piezoresistive feedback output value at different temperature, a table of the relationship between the feedback output and temperature is generated. In the temperature range from room temperature to 70 ℃, the scanning angle change of the scanning mirror decreases from 3.52° to 0.05°. By compensating the scanning angle of the scanning mirror, the 3D testing accuracy and the repeatability of the testing data of the monocular vision camera are greatly improved.
  • Jan. 25, 2022
  • Acta Photonica Sinica
  • Vol.50 Issue, 12 1212001 (2021)
  • DOI:10.3788/gzxb20215012.1212001
Anisotropic Multi-Scale Edge Detection Algorithm
Zheng Enzhuang, and Zhong Baojiang
An anisotropic multi-scale edge detection algorithm is proposed. First, the edge strength maps of the input image are obtained by using a set of anisotropic Gaussian filters at given multiple scales. Then, the obtained edge strength maps are jointly used to produce one fused edge strength map that has higher edge resolution and lower edge diffusion effect. Finally, the fused edge strength map is incorporated into the framework of the Canny edge detection algorithm to generate the final result of edge detection. A new multi-scale fusion strategy based on "signal average" is proposed creatively, and the advantages of the new strategy compared with the existing "geometric average" fusion strategy are explained from the perspective of theoretical analysis and numerical experiments. Experimental results show that the proposed algorithm effectively solves the edge spreading problem of anisotropic filter in a single scale by using multi-scale fusion strategy, and can obtain better edge detection effect than the existing algorithms while maintaining robust noise robustness.
  • Jan. 25, 2022
  • Laser & Optoelectronics Progress
  • Vol.59 Issue, 4 0412002 (2022)
  • DOI:10.3788/LOP202259.0412002
Improvement of Wavelength Calibration Accuracy of Astronomical High-Resolution Spectrometers with Fabry-Perot Etalons
Hao Zhibo, Ye Huiqi, Tang Liang, Hao Jun, Han Jian, Zhai Yang, and Xiao Dong
Due to the wide wavelength coverage and dense transmission peak sequence of its spectrum, the Fabry-Perot etalon (FPE) for wavelength calibration of astronomical high-resolution spectra is expected to achieve higher calibration accuracy than traditional calibration sources. However, the unknown wavelengths of FPE transmission peaks pose a challenge for calibration. In this study, without precision measurement devices (such as Fourier transform spectrometers), the thorium-argon (ThAr) lamp, a conventional calibration source equipped on astronomical high-resolution spectrometers, was used to provide the FPE with wavelengths. Then, the errors in the ThAr wavelengths were corrected by using the dense transmission peak sequence of the FPE and the smooth relationship between the penetration depth of the dielectric reflective coating and the wavelength. Accurate wavelengths of the FPE transmission peaks were thus obtained, and wavelength calibration was performed. The calibration test on the fiber-fed high-resolution spectrometer of the Xinglong 2.16-m telescope showed that the wavelength calibration accuracy of the FPE reached 0.053 pm, which was significantly higher than that (0.290 pm) in the case of the ThAr being used alone.
  • Jan. 17, 2022
  • Acta Optica Sinica
  • Vol.42 Issue, 1 0112002 (2022)
  • DOI:10.3788/AOS202242.0112002
Research and Accuracy Verification of Linear Polarization Measurement Technology Based on Spectral Modulation
Shi jingjing, Hu Yadong, Li Mengfan, Liu Wuhao, and Hong Jin
The linear polarization measurement technology based on spectral modulation can modulate the polarization information of incident light to the spectral dimension through the spectral modulation module. The spectral modulation module is composed of a achromatic quarter-wave plate, a multiple-order wave plate and a polarization beam splitter, which can obtain the linear polarization and spectral information of the target in a single measurement. With the combination of modulation module and grating spectrometer, a dual-channel polarization measurement system is designed. The polarization measurement model of the system is derived, the influence of spectral broadening on the modulation spectrum is analyzed, and the partial periodic least squares curve fitting method is used to demodulate the polarization information. Moreover, a test device is built to verify the performance of the measurement system. First, the complete linear polarization light is used to calibrate the retardation of the multiple-order wave plate and the polarimetric efficiency of the system. Then, the polarization measurement accuracy of the system is verified by using the variable polarization light source. The experimental results show that maximum absolute deviation between the theoretical value and the measured value of degree of linear polarization of the variable polarization light source is 1.11%, and the maximum deviation of angle of linear polarization is 0.7°, which means the proposed system has high polarization measurement accuracy.
  • Dec. 29, 2021
  • Acta Optica Sinica
  • Vol.42 Issue, 2 0212003 (2022)
  • DOI:10.3788/AOS202242.0212003
Radiometric Calibration Technology Based on Far Ultraviolet Hyperspectral Imaging Instrument
Xiao Si, Fu Liping, Hu Xiuqing, Pi Yanting, Jia Nan, Bai Xuesong, and Wang Tianfang
Using ultraviolet stars to finish the on-orbit calibration of far ultraviolet hyperspectral imaging spectrometer is an important step to achieve high precision remote sensing. However, in this way, the on-orbit calibration coefficients can not be directly used in target inversion. Therefore, the conversion of on-orbit calibration coefficients is of great significance to improve the on-orbit calibration accuracy of instrument. In this paper, the conversion process of the calibration coefficients is derived, a new equation of the calibration coefficients is given, the related verification experiments are carried out by using the developed instrument. The results show that the accuracy of target inversion can be improved by 40% by using the modified calibration coefficients.
  • Dec. 29, 2021
  • Acta Optica Sinica
  • Vol.42 Issue, 2 0212002 (2022)
  • DOI:10.3788/AOS202242.0212002
Photoacoustic Detection Method for Depth of Surface Narrow Defects
Li Haiyang, Zhi Binliang, Pan Qianghua, An Zhiwu, and Yu Ruien
This paper develops a depth measurement theory related to defect width for the quantitative laser ultrasonic detection of surface defect depth. A depth measurement formula with a width correction item is established, and a concept of defect size ratio is defined. Defects are divided into three types, namely narrow defects, extremely narrow defects, and wide defects. The applicability of the defect depth measurement method in measuring the three types of defects is discussed, and finite element simulation is adopted for verification. Finally, an experimental platform for laser ultrasonic detection is built to conduct depth detection of aluminum alloy samples with surface defects. The results show that quantitative detection of narrow defect depth can be achieved by introducing the width correction item. The average measurement error is less than 5%, which means that accurate measurement of the defect depth has been achieved.
  • Dec. 29, 2021
  • Acta Optica Sinica
  • Vol.42 Issue, 2 0212001 (2022)
  • DOI:10.3788/AOS202242.0212001
Research of Phase-Sensitive-Detection Algorithm Based on Adaptive Filtering
Lei Ming, Feng Zhihui, Nan Yaming, and Feng Tian
Incoherent laser off-target quantity detection relies on quadrature phase demodulation, and the application of a Kalman low-pass filter can significantly improve the phase discrimination performance of digital quadrature demodulation phasemeters. This paper proposes a solution based on Sage-Husa adaptive filtering, which uses adaptive factors to adjust the state prediction covariance array to effectively reduce the model errors and improve the filtering accuracy, to address the problem that the accuracy of the Kalman low-pass filter decreases when the noise statistics information is unknown. The adaptive Kalman filtering method may substantially improve the phase identification performance of a digital phase-locked demodulator and reduce the decoding error of off-target amount under low signal-to-noise ratio, according to Matlab simulation studies.
  • Dec. 23, 2021
  • Laser & Optoelectronics Progress
  • Vol.59 Issue, 1 0112003 (2022)
  • DOI:10.3788/LOP202259.0112003