A simple and efficient optical 3D-Sensor based on "Photometric Stereo"

"Photometric Stereo" is a fast and simple method to acquire 3d-data of non specular surfaces. This principle has a high information efficiency [1] and allows low cost sensors. However, it is difficult to achieve a high accuracy. The reason is that the method requires the precise knowledge of the illumination parameters (direction and power). In practice, these parameters are not well known. We overcome this problem by a new calibration procedure utilising a set of calibration gauges, and by new evaluation algorithms. We present a new low-cost device that can measure local shape with medium accuracy and that can find local defects with high sensitivity. [1] C. Wagner, G. Häusler, Appl. Opt. Vol. 42, No 27, pp. 5418-5426, 20. Sep. 2003