Two-wavelength FMCW-digital holography for three-dimensional shape measurements

Abstract

We propose two-wavelength FMCW-Digital Holography (DH) for three-dimensional shape measurement, which is a combination of FMCW-DH and two-wavelength method. By choosing the corresponding beat frequency in the frequency domain, the complex amplitude of hologram for each wavelength can be selected, independently. Therefore, the optical system achieves a common path for two-wavelength beams and requires no mechanical moving parts. In addition, it is possible to reconstruct the object waves by effectively utilizing the whole pixels of the image sensor. In this study, the proposed technique was applied to measure the surface profile of the metallic plates having the known step height and the measurement accuracy was evaluated.