A machine vision-based automatic inspection system for satellite honeycomb sandwich panel assembly compliance is designed through image segmentation technology based on 3D reconstruction and registration and contour extraction technology based on the grayscale image for the rapid measurement of the assembly compliance of inserts of the satellite honeycomb sandwich structural panels before the cover is closed. Matching and calculating the inspection data with the read CAD model to determine the wrong and missed installed embedded parts and styrofoam and calculate their position accuracy. The effectiveness of the method has been proven through validation tests on actual satellite honeycomb sandwich structural panel products, with over 300% improvement in efficiency compared with the traditional manual visual method.
Although various camera calibration methods have been proposed, most of these methods cannot deliver accurate determination of the intrinsic camera parameters, because of the coupling errors existing between intrinsic and extrinsic camera parameters and the use of explicit distortion models. Here, we propose a model-free method for accurate camera calibration, which utilizes phase-shifted fringe patterns shown on a liquid crystal display (LCD) screen for estimating the intrinsic parameters of a camera and correcting lens distortion. Horizontal and vertical fringe patterns are consecutively displayed on the LCD screen, which is placed at two positions parallel to the camera sensor plane. These fringe patterns are captured by the camera from the front viewpoint for calculating the absolute phase maps. Then, the images with lens distortion can be transformed to the distortion-free images using an inverse mapping operation. Subsequently, the principal point coordinates are calculated according to the geometric imaging relationship between the positions of the two LCD screens. Finally, the focal length can be estimated using the similarity of triangles formed by the obtained principal point coordinates and the obtained phase maps at the two positions. Both simulated and real experiments are performed to verify the validity of the proposed method. The results demonstrate that this method not only successfully eliminates coupling errors but also perfectly corrects lens distortion.
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