Phtotoelectric measurement
2022, 51(8): 20210789.
doi: 10.3788/IRLA20210789
To evaluate the resolution, angular field of view (FOV), coalignment of fundus images and OCT scans, depth scaling and other key parameters of optical coherence tomography (OCT) equipment and ensure the accuracy and validity of the equipment output values. In this paper, a model eye simulating real human eye structure was designed and developed, including the main refractive structures, such as cornea and lens, and its parameters are traceable. A 3D resolution board for lateral and axial resolution detection was designed and fabricated based on 3D printing technology. A stepped concentric ring structure was designed and machined for FOV detection. At the same time, the cross fiber module for image matching detection and the parallel glass module for depth scaling detection were designed and manufactured, which can be adapted to the fundus groove of the model eye. Confocal Raman microscopy was used to trace the size of the 3D resolution board, and the minimum detectable values for lateral and axial resolutions were 9.7 μm and 5.7 μm, respectively. The sizes of the concentric rings and fiber diameter can be traced by a Nikon projector. The maximum detectable FOV is 109.03°, and the image matching minimum accuracy is 62.5 μm. The center thickness of the parallel glass plate was traced by a Nikon digital height gauge, and the measurement uncertainty was less than 5 μm. The test of commercial ophthalmic OCT equipment showed that the model eye metrology and calibration device based on 3D printing technology has the advantages of high accuracy, high integration, wide application range and strong stability, so it is suitable for metrology and calibration of ophthalmic OCT equipment.
2022, 51(8): 20210780.
doi: 10.3788/IRLA20210780
In this article, the problem of extracting star spots for star sensor in stray light is considered. Under this setting, the effect of extracting star spots becomes worse, which affects the accuracy and reliability of the estimated attitude. An extraction method based on optimal surface fitting is proposed for this task. First, the imaging characteristics of stray light in star sensor are analyzed, and the surface model with a closed-form solution is built. Then, the method of estimating optimal stray light background and extracting star spots is proposed. The performance of the proposed method is verified by the simulated star images and star sensor images. Experimental results show that the detection rate, false detection rate and centroid accuracy obtained by the proposed method are better than that obtained by the methods based on threshold and morphological, which shows that the proposed method can resist the disturbance of stray light.
2022, 51(8): 20210714.
doi: 10.3788/IRLA20210714
Industrial gases, represented by oil and natural gas, have penetrated people's lives and production processes. Gas leakage has become one of the major disasters in current industrial production, transportation and other fields. Meanwhile, methane emissions have become the main target of China’s "carbon emissions" strategic goal. Rapid and effective gas leakage detection technology and instruments have become the focus of research at home and abroad. In response to the improvement of the performance of the uncooled infrared focal plane array (IRFPA) in recent years, its low cost, long life and high reliability can adapt to industrial gas leakage of infrared imaging detection requirements of continuous work day and night, and a variety of gas leakage infrared imaging detection modes have been developed. Based on the analysis of different infrared imaging detection modes of industrial gas leakage, this paper designs and develops an infrared imaging detection experimental system of industrial gas leakage based on differential spectral filtering, analyses and puts forward five video image processing methods that need to be studied, and gives relevant processing models or typical processing examples. The results show that the imaging detection mode has the characteristics of high sensitivity and is an effective infrared imaging detection technology for gas leakage.
2022, 51(8): 20210793.
doi: 10.3788/IRLA20210793
Based on a high-precision atmospheric disturbance monitoring method for moving objects, speckle images and various satellite images were used as background, and an experimental study on the atmospheric disturbance caused by an airplane scale model was carried out with the airplane model under the impact of high-pressure air flow. It was verified that the refractive index gradient of atmospheric disturbance was 10−6 by visual optical detection method for atmospheric disturbance of moving objects under the conditions of various background images with different resolutions and different types. The visual atmospheric disturbance information in the same experimental condition was obtained by the traditional schlieren imaging experiment, which can directly display the information of atmospheric disturbance. Through contrastive analysis, the results showed that the atmospheric disturbance information obtained by the visual optical monitoring method was the same as the directly displayed information, so the correctness of the visual optical detection method on atmospheric disturbance in the background of satellite images was directly verified. The results of this paper verified that the correctness of the visual optical monitoring method for atmospheric disturbance of moving objects in the laboratory and the monitoring accuracy of atmospheric disturbance in the condition of the laboratory test.
2022, 51(8): 20210591.
doi: 10.3788/IRLA20210591
We studied the problems of large fluctuations in the dynamic friction torque data of lidar shafting and low precision of repeated measurements. The data cloud constructed based on the test spindle control system was fused with the GA-BP algorithm, and a self-updating control algorithm for lidar shafting friction torque detection equipment was proposed. The data cloud was constructed based on the actual speed, ideal speed, speed error and speed error change rate of the test spindle. The density and distance information were used to add and delete data, and the online control parameters were adjusted by the GA-BP algorithm. Taking the lidar shafting friction torque detection equipment to test the main shaft and the measured shaft system as the research object, the simulation experiment proves that this method improves the system’s anti-interference performance compared with the control system using the Z-N-PID algorithm. The friction torque is detected by lidar shafting friction torque detection equipment. The experimental results show that the proposed self-updating control algorithm reduces the average overshoot by 12.77% compared with the Z-N-PID algorithm, the data standard deviation after stability is reduced by 5.00%-40.63%, and the repeated measurement error is reduced by 24.20%-71.66%.
2022, 51(8): 20210750.
doi: 10.3788/IRLA20210750
In recent years, the field of civilian unmanned aerial vehicles has developed rapidly, leading to the frequent occurrence of unmanned aerial vehicle "black flying" incidents, which has brought considerable challenges to national security and social stability, and there is an urgent need to develop anti-UAV technology. In this regard, this paper proposes a follow-type directional jamming method and designs a vision-based UAV intrusion detection and automatic tracking and interception system. The HOG+nonlinear SVM scheme is used to identify the UAV, the ViBe moving target detection algorithm is added to improve the recognition speed, and UAV target tracking is realized through the KCF algorithm. Design and manufacture the hardware equipment of the UAV interception system, mainly including the tracking servo system, base and tray. Experiments show that the recognition accuracy of the system reaches 90.54%, the recognition speed is 20.56 fps, the interception platform can achieve the aim of the target UAV within 0.5 s, and the tracking effect is good. The system is tested on the built physical platform, and the results show that the system can realize the movement detection, recognition, tracking and interference of invading UAVs. The recognition accuracy is high, the real-time performance is good, and the system can automatically intercept the invading UAVs.
2022, 51(8): 20210778.
doi: 10.3788/IRLA20210778
Aiming at the problem that manual adjustment of camera parameters in structured light measurement was easy to lead to the randomness of image quality, which leads to the decline of calibration accuracy and the repetition of parameter adjustment, an adaptive parameter adjustment method for camera calibration in structured light measurement was proposed. Firstly, a set of camera automatic parameter adjustment device was designed. According to the image change mechanism of three parameter adjustment rings, three parameters of calibration plate area ratio, image clarity and image contrast were selected to define the focal length adjustment ring, focusing ring and aperture adjustment ring respectively. Secondly, in order to realize the high-precision calibration and adaptive parameter adjustment of the camera, aiming at the defects of the traditional Brenner function, an improved Brenner automatic threshold function was used to realize the accurate and rapid focusing of the image definition, segment the foreground and background of the region of interest of the calibration plate image, calculate the image contrast, and according to the calibrated reprojection error. The optimal adjustment interval of the calibration camera was determined, and the calibration parameters were adjusted by the adaptive parameter adjustment search control method. Finally, in order to improve the search and positioning speed of the motor during adaptive calibration, the parameter adjustment function model was established, and the focal length was calculated adaptively through the object distance and pixel length. The three-dimensional measurement parameter adjustment experiment shows that compared with manual calibration, the proposed parameter adjustment method can realize automatic parameter adjustment within 5 s, and the reprojection error is reduced by 66.57%.
2022, 51(8): 20210625.
doi: 10.3788/IRLA20210625
In view of light interference during indoor environment reconstruction, and phase value jump problem that occurred from the disaccord between the wrapped phase cycle and Gray-Code class cycle in phase unwrapping because of Gamma transformation in process of fringe projection and phase shift, an anti-global illumination reconstruction method based on adaptive interpolation filtering was proposed. The high speed projection method was used to reduce the influence of light source interference. Firstly, the binary defocused phase shift fringes and high frequency gray code fringes were projected onto the surface of the environment to be measured. Hilbert transform and high frequency decoding were used to solve the unwrapping phase. Secondly, the adaptive interpolation filtering algorithm was adopted to repair the unwrapping phase containing phase jumps. Finally, the morphological features of the environment to be measured were restored. The types of jump points were analyzed, and the interpolation filtering was selectively carried out to eliminate the phases jump and avoid the generation of repeated phase. Compared with other global filtering methods, our method can improve the efficiency by 90% under the condition of higher accuracy, and achieve the goal of high-speed and high-quality indoor environment reconstruction.
2022, 51(8): 20210580.
doi: 10.3788/IRLA20210580
To overcome the influence of body vibration and airflow disturbance on the alignment accuracy of the three-axis airborne optoelectronic system, a fuzzy sliding mode robust control method was proposed. First, the mathematical model of the three-axis airborne optoelectronic system was established according to the coordinate transformation relationship. Then, the fuzzy sliding mode robust control law was designed by introducing a fuzzy algorithm to estimate the interference value. Finally, the stability analysis was given, which can ensure that the three-axis airborne photoelectric system has high-precision tracking for the target orientation. The simulation results show that the proposed method has a better control effect than the fractional order control method, can track the command signal stably in 300 ms, and the maximum interference estimation error is only 0.2 N·m and has higher control accuracy, the maximum tracking error of pitch angle, roll angle and heading angle is only 0.5°, 0.7° and 0.4°, respectively, which greatly improves the alignment accuracy of the three-axis airborne optoelectronic system.
