An Integrated Measurement System for the Inspection of Extended Surfaces in Industrial Quality Control

摘要

Reliable real-time surface inspection of extended surfaces with high resolution is needed in several industrial applications. With respect to an efficient application to quality control (e.g. for in plane inspection problems such as shape verification of aircraft components), the inspection system has to perform a robust measurement with a ratio of <10~(-6) between depth resolution and lateral extension. This ratio is at least one order beyond the solutions that are offered by existing technologies. To overcome this lack of technology, a concept has been developed which is based on the assumption that high resolution data is only needed in certain areas of the object under inspection. For the application of this concept of scaled topometry to quality control of extended surfaces, different optical measurement techniques with overlapping ranges of resolution are arranged systematically in order to receive characteristic surface information with the required accuracy. In such a surface inspection system, a discrimination algorithm combines measurements on several scales of resolution and distinguishes between fault indicating structures with different extensions. We have built a laboratory setup in which global measurements of surfaces with extensions up to 1500 mm x 1000 mm x 500 mm (in x-, y- and z-direction respectively) can be realized. For the global measurement a macroscopic fringe projection system is used. The refined measurements are performed by different adaptable sensors (microscopic fringe projection, laser triangulation, white light interferometry, confocal microscopy), which are chosen according to the requirements and can be mounted to a xyz-positioning system. Using this measurement system we are able to separate the fault indicating structures on the surface from the global shape and to classify the detected structures according to their extensions and characteristic shapes simultaneously. The technique is completely scalable and can be adapted to the measurement of larger objects.