Sub-pixel accuracy by optical measurement of large automobile components

The paper deals with two problems occurring when larger parts are manufactured by state of the art laser beam or water jet NC-cutting machines: first, the machine has to know the contour to cut; second, the contours of cut parts must be measured to ensure the required dimensions. The developed solution is applicable for both tasks. A large scale backlighted measuring table allows to handle parts up to 2000/spl times/1500 mm/sup 2/. The calibration problem is solved using an especially structured frosted glass plate, the desired accuracy will be reached using subpixel methods. For problems arising in real applications, e.g. how to handle the thickness of parts or how to fit images of different cameras together, solutions are proposed and implemented. A stressing point is the applicability of the developed system in an engineering environment.