Improving 4-D shape measurement by using projector defocusing

This paper presents a real-time 3-D, or 4-D, shape measurement technique that can reach the speed limit of a digital fringe projection system without significantly increasing the system cost. Instead of generating sinusoidal fringe patterns by a computer directly, they are produced by defocusing binary structured patterns. By this means, with a relatively inexpensive camera, the 3-D shape measurement system can double the previously maximum achievable speed, and reaches the refreshing rate of a digital-light-processing (DLP) projector: 120 Hz.