The development of optical fringe measurement system integrated with a CMM for products inspection

Abstract

In the field of industrial product inspection, a CMM (Coordinate Measurement Machine) is indispensable to get high precise dimensions, and it is tedious to inspect a complex shape by manual. For many products, high precise dimensions are only needed on some special features, such as cylinders, holes, and plans. In this paper, an optical fringe measurement system is implemented based on Gray code, and a Canon DSL camera with high resolution is adopted to capture the projection patterns and the coded markers glued on the CMM. The range images from the optical measurement system are automatically aligned with the CMM coordinate system through the coded markers. A greedy feature fitting algorithm is used to processing the obtained points cloud, and the special features are extracted, which are used to direct the CMM to obtain more precise parameters. In this integration system, the whole inspection procedure is automated regardless of the existence of the CAD model of the product. The data from different sensors are fused together by an overlap patch algorithm. As a result, the full surface is scanned, and the necessary precision is guaranteed on some special locations. The design principle and workflow of the integration method are presented, and a detail example is given.