Absolute Phase Measurement Based on Combining Binary Color-Code and Phase-Shift Light Projection

Abstract

In this paper, a novel composite RGB fringe pattern projection and processing method is presented to obtain the absolute phase information of objects having surface discontinuities and/or spatially isolated surfaces. Multiple sinusoidal fringe patterns and binary fringe patterns are coded into the red, green and blue channels of composite RGB fringe pattern images. The generated composite images are projected onto object surfaces by a DLP(Digital Light Processing) projector and the deformed fringe patterns captured by a 3‐chip color CCD camera from a different viewpoint. The sinusoidal and binary fringe patterns are extracted from the acquired composite fringe pattern images. A multiple‐step phase shift algorithm calculates the wrapped phase information from the obtained sinusoidal fringe patterns, so the phase has a high resolution and dynamic range. While the binary fringe patterns determine the absolute fringe order of the wrapped phase map. Therefore, the composite RGB fringe pattern projection technique can measure the absolute phase information of objects having surface discontinuities and/or spatially isolated surfaces. Experimetal results on measuring a white plain board, two objects in the same field of view show that the proposed fringe projection and processing method can measure the 3D shape of complex objects having surface discontinuities and/or spatially isolated surfaces from four acquired composite RGB images.