Optical processing of composite pattern structured light projection for high-speed depth measurement

Structured light pattern projection is a well known method of accurately extracting 3-Dimensional information of a scene. Traditional multi-frame structured light methods require several different patterns to recover the depth, without ambiguity and albedo sensitivity, and are corrupted by object motion during the projection/capture process. The authors have developed a methodology for combining multiple patterns into a single composite pattern by using spatial modulation techniques. A single composite pattern projection does not require synchronization with the camera so the data acquisition rate is only limited by the video rate and therefore suitable for high-speed depth measurement. However, the composite pattern is restrained by the spatial bandwidth directly related to the number of embedded patterns and the lateral resolution of the camera. Another problem is the processing requires image demodulation which is computational intensive. As part of a NASA Phase I STTR, we address the first limitation by analysis of the source of the error and post-processing the reconstruction data with dynamic programming approach. For the second problem we propose the use of a 4-f optical correlator, not as a correlator, but instead as an optical demodulator. Simulation results show reasonable depth reconstruction using our strategy for composite pattern after the post-processing.