Digital holographic microscope employing dual-Lloyd’s mirror

Abstract

We propose a digital holographic microscopy (DHM) setup employing a configuration with two Lloyd's mirrors, which is based on self-referencing and dual-wavelength optical phase unwrapping. We use two Lloyd's mirrors to fold the beam which does not exhibit sample structure and acts as the reference beam, returning onto itself to form a dual-wavelength hologram. Two wrapped phase images for every wavelength are reconstructed by angular spectrum method. Then the wrapped phase image and the three-dimensional profile image are acquired by dual-wavelength optical unwrapping method. In the experiment, we use two lasers of different wavelengths of 532 and 632 nm to record a hologram. Numerical methods are subsequently applied to reconstruct the hologram to enable direct access to both phase and amplitude information. The quantitative experimental results with dual-wavelength DHM involve a deviation less than 5% from the calibration values. The validity of this method is demonstrated.