Spatio-temporal phase-encoding profilometry using correlation image sensor

In this paper, we propose a real-time 3-D shape measurement system which consists of 1) a moving fringe projector for spatio-temporal encoding (single frequency in time but different phase in space) of illumination angle, and 2) the three-phase correlation image sensor (3PCIS) which performs the synchronous detection and amplitude/phase demodulation of intensity-modulated light in real time on each pixel. The 3PCIS demodulates amplitude and phase of moving fringes in a scene frame by frame. Then, it is unwrapped in real-time to a sequence of projection angle maps based on an efficient use of spatial and temporal continuity of the phase maps. Compared with the phase-shift method using a color image sensor or a high speed camera, the system is shown to have novel characteristics; pixel by pixel capture of phase map in a single frame, freedom from environmental light sources and grayness nonlinearity of fringes, reduced sensitivity to object motion, etc. We implemented this system using CMOS 200 x 200 and 320 x 256 pixel 3PCIS recently developed by us.