ACQUISITION OF 3-D DATA BY FOCUS SENSING UTILIZING THE MOIRE EFFECT OF CCD CAMERAS

A new technique was recently presented for finding the 3-D shape of diffusely reflecting object surfaces [Appl. Opt. 27, 4684-4689 (1988)]. The technique is based on grid projection with small depth of focus, confocal observation, and focus sensing by evaluation of the local grating contrast. In this paper a modification of the measuring system is demonstrated that allows the use of a 2-D CCD array instead of a vidicon as the detector. In this modification the moire effect between the projected grid and the CCD array is utilized. Depth resolution is increased, and almost no unwanted moire terms arise in the detector output as long as the grating frequency is chosen above the Nyquist frequency of the array. The technique can be useful in robot vision.