Single-shot 3D measurement by multi-wavelength parallel phase-shifting digital holography

We proposed the use of multiple wavelengths in parallel phase-shifting digital holography (PPSDH) to widen the measurement range of PPSDH. The technique simultaneously uses multiple laser lines in PPSDH to recording hologram. Processing procedure of the image reconstruction of PPSDH is applied to the single hologram recorded by using the multiple wavelengths, then multiple complex amplitudes of the object corresponding to the multiple wavelengths are obtained. By applying the multi-wavelength phase-unwrapping method to the obtained multiple complex amplitudes for the multiple wavelengths, the height of the object more than either wavelength can be measured. We conducted an experiment of the technique using lasers lines; λ = 473 and 532 nm. Single-shot measurement of the object having a 1.9 μm step was successfully demonstrated.