Study and application of high accuracy and long size measurement based on machine vision - art. no. 67234K

The visual inspection technology, which can extraordinarily reduce inspection cost, greatly speed up of development and raise the efficiency of production, has become the topic of the day in industrial online inspection in recent years which is widely used in the field of industrial inspection(1). In this paper, a method of high accuracy and long size base on machine vision is developed, and some key techniques are introduced in detail, such as lighting system, optical lens, camera, and image processing algorithm. The quality of image is improved by optical imaging and lighting system. A CMOS (Complementary Metal-Oxide Semiconductor) camera with a selected optical lens was used to capture the image of an object. The analogue signals of the image were transformed into corresponding digital grey level values. By using the binarization technique, the images of background and the object were segmented. The precision of edge detection was improved by sub-pixel technique. The precision of fitting was improved by least square method and Hough transformation. Space coordinate was transformed from an image pixel coordinate through coordination. An automatic detection system of ceramic pieces was also developed And by taking example of ceramic piece 80 nun long and 80 mm wide, the test method is applied by the detection system with accuracy about 8um. The outcome of experiment accords with the fact, this method is simple and feasible, and is of high accuracy, dependability, and high automation.