Three-dimensional imaging for micro-optical component by using dual-wavelength digital holography

The three-dimensional (3D) profiles of a plate with many micro grooves is obtained by using dual-wavelength digital holography. Two individual phase images are obtained by using two different wavelengths, respectively, and the phase image for beat wavelength is obtained after dual-wavelength phase unwrapping. Then the 3D profiles can be obtained through the phase image of the beat wavelength. This method is demonstrated by both numerical simulation and experiment. In the experiment, two lasers of the different wavelengths 632.8 nm and 671 nm are used to obtain a larger beat wavelength. The object is a plate with many micro grooves. The result shows that the average depth of the groove is 7.1 μm. This is in good agreement with the result given by the profilometer. It demonstrates that the 3D imaging result by using dual-wavelength digital holography is effective.