earticle

영어

To meet the demand of rapid, accurate and online inspection of precision parts’ defects, the CCD camera is used to collect information of the inner hole. Since the obtained source image is a concentric annular image of 360 degrees with large image distortion, meanwhile the collected source images are not suitable to be processed directly with the image processing technology. So further processing is needed to be done for the rectangle unwrapping images. The method of Hough transform is adopted in this paper to find the center of a circle and the corresponding position used the center as a reference. On the basis of positioning the circle center, a kind of circular image unwrapping algorithm is designed by the transformational relation between Cartesian and polar coordinate. During unwrapping of the image, the bilinear interpolation algorithm is adopted to improve the image quality when the image unwrapping algorithm is used. The algorithm is verified by program and the result indicates that the algorithm to unwrap the image is efficient in locating the center by Hough transform combined with the coordinate’s transformation and the bilinear interpolation. Furthermore, the algorithm can unfold the image accurately and quickly and ensure the quality of the image, which prepares the foundation for subsequent processing.