Analysis and reduction of phase errors caused by nonuniform surface reflectivity in a phase-shifting measurement system

The measurement accuracy of a phase-shifting measurement system is adversely affected by phase errors. This paper presents a theoretical analysis of phase errors caused by nonuniform surface reflectivity, such as varying reflectivity and a sharp change in reflectivity. Based on the analysis, a method to adaptively adjust the maximum input gray level of each pixel in projected fringe patterns to the local reflectivity was proposed to reduce phase errors. Experimental results for a planar checkerboard show that the measurement error can be reduced by 56.6% by using the proposed method