Multi-wavelength phase-shifting interferometry for micro-structures measurement based on color image processing in white light interference

• A single-chip color CCD camera is used to accomplish the proposed method.
• A special 7-step phase-shifting algorithm is applied to obtain the Phase.
• CWT is applied to extract the mean wavelength accurately.

Conventional multi-wavelength phase-shifting interferometry utilizes two or three monochromatic light sources, such as lasers, to realize the measurement of the surface topography with large discontinuity. In this paper, the white light source, with a single-chip CCD color camera, is used to accomplish multi-wavelength phase-shifting interferometry. In addition, we propose an algorithm which combines white light phase-shifting algorithm, equivalent wavelength method and fringe order method to achieve measuring and calibrating the micro-structures ranging from nanometer scale to micrometer scale. Finally, the proposed method is validated by a traceable step height standard.