Embedded three-dimensional shape measurement system with microprojector

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An embedded system implementing fringe encoding, image acquisition and algorithm processing has been recently designed and developed for 3D shape measurement based on structured light technology. Compared with traditional 3D shape measurement system, which has disadvantages of complex structure and slow processing speed, our embedded system is more effective in industrial quality detection. With self-developed digital micro projector based on liquid crystal on silicon, the structured light patterns are projected by high-resolution such as 720p. In the generated module of the stripes, we add a Gamma value to lower the projection error. Image acquisition sensor is synchronized with the micro projector by EP2C8 FPGA hardware circuits, which simultaneously control the phase encoding fringes according to different characteristic objects. To get high performance, accurate synchronization is crucial, especially in Phase Shifting Method, there are sequential images with shifting phases, in other words hardware circuit guarantee the processing speed before algorithm processing. We improved the three step phase algorithm, using the intensity modulation, which is a relatively simple method to solve the intensity imbalance of the three images. By implementing the digital signal processing (DSP) TMS320DM642 system, we realized three-dimensional measurement with a pipeline process of structure light encoding, image acquisition and three-dimensional reconstruction. Finally the measure experiment shows that the processing frame rate is up to 16 fps, and the measurement error is less than three percent. It means we can quickly and accurately detect three-dimensional profile with the portable device.