High dynamic defocus response method for binary defocusing fringe projection profilometry.

Abstract

The measurement accuracy of high-speed binary defocusing fringe projection profilometry depends on the fringe pitch and defocus degree. During the measurement process, the degree of defocus changes with the measurement depth of the scenes. This makes it difficult to obtain a suitable defocus degree and achieve high-precision measurement owing to dynamic changes in the measurement object or environment. To address this problem, we propose a highly dynamic defocus response method to adaptively adjust fringe pitches for binary defocusing fringe projection profilometry. As the defocus degree changes significantly, the proposed method can respond quickly and adjust the fringe pitches adaptively to the scenes. Therefore, a high-precision dynamic measurement can be achieved for the current measuring scene. In this study, considering the effect of random error and nonlinear error, we established a complete phase-error model and used it as an optimization function. Based on this function, we obtained the optimal fringe pitch expression with the defocus degree and harmonic response parameters as variables. With the proposed method, we can obtain the defocus degree and harmonic response parameters during the measurement process and calculate the optimal fringe pitches for the current scenes. Thus, the proposed method can dynamically adapt to the measuring depth change and achieve an accurate measurement without modifying any hardware parameters.