Two-Step Fringe Analysis for Fringe Projection Profile Measurement

Digital fringe projection method is a noncontact surface profiling technique. For accurate measurement, phaseshifting technique is usually adopted. However, the specimen may be moved during the time of image capture, and not suitable for dynamic measurement. In order to overcome this drawback, a digital fringe projection system consisting a color projector, a color CCD camera, and a PC is proposed. The phase shift is introduced between two computer-generated fringe patterns with different colors, which is projected onto the object to be measured simultaneously. The projected fringe patterns are captured by the color CCD camera and separated and processed by a two-step fringe analysis scheme using spiral phase transform and optical flow techniques. The proposed system was applied to a real specimen. The test results are reported.