High-speed 3D shape measurement using array projection

Measuring the three-dimensional (3D) surface shape of objects in real time has become an important task e. g. in industrial quality management or medical sciences. Stereo vision-based arrangements in connection with pattern projection offer high data acquisition speed and low computation time. However, these coded-light techniques are limited by the projection speed which is conventionally in the range of 200 ... 250Hz. In this contribution, we present the concepts and a realized setup of a so-called 3D array projector. It is ultra-slim, but nonetheless able to project fixed patterns with high brightness and depth of focus. Furthermore, frame rates up to the 100 kHz range are achievable without any need of mechanically moving parts since the projection speed is limited mainly by the switching frequency of the used LEDs. According to the measurement requirements, type and structure of the patterns can be chosen almost freely: linear or sinusoidal fringes, binary codes such as the Gray code, square, hexagonal or random patterns and many more. First investigations on the functionality of such a 3D array projector were conducted using a prototype with a combination of Gray codes and phase-shifted sinusoidal fringes. Our contribution proves the high brightness of the proposed projector, its sharpness and the good Michelson contrast of the fringe patterns. We deal with the patterns' homogeneity and the accuracy of the phase shift between the sinusoidal patterns. Furthermore, we present first measurement results and outline future research which is, inter alia, addressed to the use of other structured light techniques with the help of new purpose-built 3D array projector prototypes.