Absolute phase calculation from one composite RGB fringe pattern image by windowed Fourier transform algorithm

Abstract

This paper presents an absolute phase calculation method from one composite RGB fringe pattern image by using the windowed Fourier transform (WFT) algorithm and the optimum three-frequency selection method. Three fringe patterns having the optimum fringe numbers are coded into the red, green and blue channels of a composite color image. The generated composite RGB image is projected onto a measured object surface from a Digital Light Processing (DLP) projector and the deformed fringe patterns captured by a color CCD camera from a different viewpoint. The wrapped phase information will be calculated by the WFT algorithm. The WFT algorithm limits the processed image to a small area, so it can give much better phase near edges or discontinuities than FT algorithm. Applying the WFT algorithm to the three fringe patterns obtains three wrapped phase maps. An absolute phase map is calculated pixel by pixel from one composite RGB fringe pattern image after applying the optimum threefrequency selection method to the three obtained wrapped phase maps. Therefore, the proposed method can measure absolute phase of objects having discontinuous surfaces from one snapshot image. Experimental results on moving discontinuous objects show that the proposed method reliably obtains the absolute phase information.