Shape measurement using phase reliability evaluation value on whole-space tabulation method

Abstract

Surface profile measurement by non-contact optical methods has been extensively studied because of its importance in mechanical component inspection, reverse engineering, and 3-D solid modeling applications. Grating projection method is often used for non-contact shape measurement. Whole-space tabulation method, a kind of grating projection method, is a technique of producing phase-coordinate tables pixel-by-pixel which relates phases of the projected grating to the spatial coordinates. This method excludes a lens distortion and intensity errors of the projected grating in measurement results theoretically. Tabulation makes short-time measurement possible. One major problem is overflow of the detector. As a result, the underexposed and/or overexposed areas on the imaging device, where the phase information cannot be obtained with high accuracy. We previously proposed an evaluation method for the reliability of the analyzed phase in a phase-shifting method using Fourier transform (PSM/FT) for shape measurement. This phase reliability evaluation value is useful to merge data when the measurement condition is changed. In this paper, it is confirmed that accurate shape measurement and the whole-space tabulation method using phase reliability evaluation value can be performed.