Projected fringe profilometry using a liquid-crystal spatial light modulator to extend the depth measuring range.

An approach using a liquid-crystal spatial light modulator (LC-SLM) to enlarge the depth measuring range of the projected fringe profilometry is presented. This approach is especially applicable to detect dynamic objects with micro-scale sizes. Compared with a typical 2D image system, the LC-SLM provides a better performance for a 3D shape sensing system. The main advantages include (1) a much higher allowance to increase in the depth measuring range, (2) easiness to compensate perspective distortion and geometric distortion, (3) very high accuracy (in the micron-range) and (4) only one phase measurement needed for operation.