Real-time dual-wavelength digital holographic microscopy with a single hologram acquisition

TLDR

The study presents a technique for two‑wavelength digital holographic microscopy using a single hologram acquisition. The method extends the unambiguous measurement range to microns by exploiting a synthetic wavelength from two ~80 nm‑separated wavelengths and achieves real‑time imaging with two reference waves of differing wavelengths and propagation directions. This is the first reported real‑time synthetic beat‑wavelength digital holography measurement.

Abstract

A technique to perform two-wavelengths digital holographic microscopy (DHM) measurements with a single hologram acquisition is presented. The vertical measurement range without phase ambiguity is extended to the micron-range, thanks to the resulting synthetic wavelength defined by the beating of two wavelengths with a separation of about 80nm. Real-time dual-wavelength imaging is made possible by using two reference waves having different wavelengths and propagation directions for the hologram recording. The principle of the method is exposed and experimental results concerning a 1.2mum m high test sample as well as a moving micro-mirror are presented. To the extent of our knowledge, this is the first time that real-time synthetic beat-wavelength digital holography measurements are reported.