New optical and electronic approaches for automatic visual inspection of hydraulic cylinders

In a cooperation of an automotive supplier and a research institute a system for automated visual inspection of hydraulic cylinders has been developed. The image acquisition process uses a panoramic lens for 360 degree angle of view and a CCD camera. The acquired image is electronically warped with pipeline image processing hardware. By means of a forward movement of the borescope it was possible to acquire an image of the entire inner surface of the hydraulic cylinders. After image acquisition an automated visual inspection is performed. Flaws in the surface down to a minimal size of 0.2 mm are detected and classified into different defect types. Furthermore, cross boreholes are inspected with respect to the deburring state. The inspection time of a hydraulic cylinder with a length of 100 mm is about 15 seconds. A PC platform with pipelined image processing hardware performs image warping, texture segmentation, blob analysis and arc fitting.