METHOD AND APPARATUS FOR DIGITAL MOIRE PROFILOMETRY CALIBRATED FOR ACCURATE CONVERSION OF PHASE INFORMATION INTO DISTANCE MEASUREMENTS IN A PLURALITY OF DIRE

摘要

Projectors and cameras disposed about an object under test obtain digital moire information of overlapping aspects (views) of the object. The system is calibrated using a calibration pattern of straight lines on a flat reference surface and a projected pattern of lines which are perpendicular to the lines of the calibration pattern and contain marker fringes between predetermined lines. Each aspect is calibrated individually by stepping the calibration pattern along the axis of each camera so as to obtain a plurality of tables which relate phase information to distance in each of a plurality of planes spaced successively closer to the camera. The calibration tables define a calibrated volume in space between the cameras and projectors. When the object under test is located in this volume, the video signals from the camera are converted into digital moire information. This information is directly related to the calibration information and is converted with the aid of the calibration information into absolute distance measurements along the perimeters of cross-sections through the object.