Phase-measuring profilometry of colored objects based on color coding and sinusoidal correction

Abstract

To improve the phase-measuring profilometry measurement speed, phase-shifted fringes can be encoded into color channels. However, for colored objects, the intensity of the fringes in each channel is affected by surface texture. Therefore, a measurement method based on color coding and sinusoidal correction is proposed. First, two color images are encoded. The red (R) and blue (B) channels for the first image and the green (G) channel for the second image are used in a three-step phase-shifting process. Meanwhile, the G channel of the first coded image and the R and B channels of the second coded image are corresponding solid colors. Two color-coded images are projected onto the object’s surface, and the CCD captures the modulated deformed fringe pattern. After decoupling, the channels of the images are separated, the pure color channels are extracted, and the reflectivity of each point on the object surface in the RGB channels is calculated. Then, the intensity of the phase-shifted fringes in the two images is corrected by the calculated reflectivity. A 24-color standard color card and color lion mask were used to verify the method. Compared with the traditional color coding method, we were able to reduce the influence of color texture and obtain better results.