Application of digital micro-mirror device to deformation measurement

Grating projection methods have been often used for non-contacting shape and deformation measurement. An image of equal-height or equal-displacement contour images of an object can be obtained in real-time using moire topography. We have developed the phase-shifting scanning moire method for real-time shape and deformation measurement with high resolution. But there is a problem that the measuring error becomes larger when the object is moving speedily because several images are captured while shifting the grating phase. In this paper, we propose a phase-shifting scanning moire method using a DMD (Digital Micro-mirror Device), which can obtain an image showing equal-height or equal-displacement contour within a frame time. A DMD has about a million mirrors in a chip and the direction of a ray reflected at each mirror of the DMD can be selected quickly. By using the DMD, we developed a DMD reflection-type CCD camera called as 'DMD, camera'. The camera works as a camera whose each pixel has a shutter. The structure and an experimental result to confirm the algorithm to obtain an equal-height or equal-displacement contour image using the DMD camera are shown.