Spatio-temporal phase-encoding profilometry using correlation image sensor

In this paper, we propose a real-time 3D 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 200times200 and 320times256 pixel 3PCIS recently developed by us.