Abstract
An inner wall surface inspection method for metal cylindrical parts of automobiles, such as engine cylinder bores, has been developed. This method is realized by combining a specialized optical system and image processing. The specialized optical system named “Endoscopic Camera” images the texture of the cylindrical inner wall surface. The specialized image processing named “KIZUKI” algorithm detects defects such as scratches from the successively captured images. In the optical system, a lens with a concave dome-shaped reflective surface was developed. This lens will allow not only obtaining an image of the entire circumference of the cylindrical inner surface with a single shot, but also coaxial incident illumination which highlights the scratches. “KIZUKI” algorithm is a technique inspired by the peripheral vision and the involuntary eye micro-vibration of the human vision architectures. It consists of three steps : first step for forming low resolution images by a variable re-sampling, and the second step for detecting relatively salient regions at each low resolution image, and the last step for integrating these regions. To evaluate the effectiveness of the proposed method, a cylinder sample with a known flaw size was measured. As a result, a scratch small as 0.16mm × 2.0mm in size was detected, thus the validity of the proposed method was confirmed.
