Flaw Detection Using Image Registration and Fusion Techniques

Abstract

The inspection of polished metal contoured surfaces, such as silverware pieces, is much more difficult than for a flat surface, considering the complex curved surface, reflections, and shadows. It is hard to detect flaws when they overlap with shadows and specular reflections, which is typically the case. In this paper, this problem is solved using image registration and image fusion techniques. A continuous-inspection system is developed to take two images sequentially under different lighting conditions when the object is passing under the camera. Shadows and reflections shift, while the flaws do not. From the differences of these two images, flaws can be distinguished from shadows and reflections, and the lost information due to specular reflections can be made up. Fused images without specular reflections were obtained, and a new feature based image registration algorithm is developed to compare these two fused images to detect the surface flaws.

New Methods for Dishware Identification and Inspection

“…The experimental setup, inherited from Zhou (2008) is shown in Fig 2, with our modifications in lighting. After washing, it is anticipated that dish pieces will be automatically placed on the conveyor.…”

“…Let sensor size SS= 17mm, sensor resolution SR= 1038 pixels, and focal length FL= 35mm. Choose working distance WD= 600mm, which is large enough to avoid distortion when the lens is focused on an object within the working distance (Zhou, 2008). Then we calculate the smallest feature size, SFS, that the camera can detect (Edmund Industrial Optics) by:…”

“…Certain food particles, such as dried egg yolk, can be especially difficult to detect. Fifth, the definitions of a "clean dish" and a "dirty dish" are subjective and illdefined (Zhou, 2008).…”

“…He used edge detection algorithms together with template matching to inspect recognized silverware pieces. Zhou (2008) proposed an algorithm to recognize silverware pieces with incomplete (truncated) images and a fusion-based method for silverware inspection, producing very good results.…”