关键词: 图像处理, 脊波变换, 亚像素, 裂纹测量, 工业CT

Abstract: This paper mainly solves the problem of measuring the small crack in industrial CT（Computer Tomography） images.Ridgelet transform is developed from wavelet transform.The idea of ridgelet transform is that turns line singularity into point singularity according to radon transform，and then deals with point singularities using wavelet in radon domain.Therefore，it is appropriate that ridgelet transform can detect the defects in images such as cracks，which have line singularities，and it can suppress the point noises in images.In this paper，image is firstly projected，one-dimensional wavelet transform is next applied to projections，then do approach on the crack，reduce the scope of crack.Finally the edge of the crack can be obtained.But the measured width of cracks is larger than true width because of the influence of point pervasion in CT images.The width shrinkage and scale calibration are used in this paper.An industrial CT testing image is used to do experiment.The result of the measurement can reach sub-pixel accuracy.The ridgelet transform，edge approach and width shrinkage are used for measuring the small crack in industrial CT image.This presented method can also be applied to other measurements.

Key words: image processing, ridgelet transform, sub-pixel, crack measure, industrial Computer Tomography（CT）