Single-shot 3-D sensing of micro-meter height by multi-wavelength parallel phase-shifting digital holography

We propose a single-shot three-dimensional sensing technique being capable of achieving measurement of a micro-meter height by multi-wavelength parallel phase-shifting digital holography. In the proposed technique, we use the two-wavelength phase unwrapping method to expand measurement range in the height direction to measure a step of more than half a wavelength in height. To confirm the effectiveness of the proposed technique, we conducted an optical experiment in which we used the object with abrupt step of 1.90 μm. The experimental result indicated that the height of the object was 1.85 μm. Thus, we experimentally verified the proposed technique.