Object adapted pattern projection—Part I: generation of inverse patterns

Fast and robust 3D inspection is of big importance for industrial quality control. Therefore, reliable optical techniques are needed that use as few images as possible for measurement. One promising technique for this aim is the inverse fringe projection which has the following advantages:The technique includes the information of a preceding measurement into the projected inverse pattern. Therefore, it is possible to do differential measurement using only one camera frame for each state. Because the camera takes images with user-defined patterns (e.g. fringes with constant frequency), one always has optimized patterns for sampling independently of the object shape. The hardware needs are as low as just a programmable projector and a standard camera.Till now the technique had drawbacks concerning the robust pattern generation and the quantitative (instead of only qualitative) evaluation of differential phases. In this paper, we concentrate our investigations on the robust pattern inversion. We show how the process can be simplified by separating the different inversion problems. Different methods and examples for generating the inverse pattern will be shown and compared to each other.