Accuracy of Real-Time Shape Measurement by Phase-Shifting Grid Method Using Correlation

Abstract

Real-time and non-contact methods are desired to measure the shape of human bodies or moving objects. Grid projection methods are suitable for this purpose. To obtain accurate results, it is necessary to analyze phases of a projected grid accurately. Recently, we proposed real-time shape measurement with a phase-shifting grid method using correlation. Contour lines of objects are obtained as phase values in real time with this method. Phases are obtained without the influence of saturation of an image sensor by this method because a grid with rectangular brightness distribution is projected. In practice, however, the brightness distribution of the grid is deformed because the grid is out of focus. In this study, the accuracy of this method in measuring a moving object is examined by computer simulation. The error is 3% for a phase of 2π in the case of worst focus when the object is stable. The error increases linearly with the phase-shifting aberration ratio when the object is moving.