On-line shape control is an important tool of automated fabrication, but is difficult to realize, when test cycles below one second are needed. In this paper we present a new method for the detection of three-dimensional shape deviation based on holographic projection of object-adapted fringes. If the shape of the test object is correct, the camera detects a fringe grid with constant period. Shape deviations can therefore be calculated with fast algorithms. Holographic projection allows for higher triangulation angles and therefore increased sensitivity. To overcome limitations of 3D-projection, the adapted fringes are calculated fro a selected plane of sharpness and projected coherently onto the object. A liquid crystal dispaly is used for projection. A hologram is taken from the scenery, a new plane is focussed and the hologram is exposed again. The multiple exposed hologram is reconstructed and projects adapted and sharp fringes onto the entire object. We use this technique to examine technical objects like turbine blades of a car turbo charger. Roughness parameter for holographic and LCD projection are compared.
展开▼
