Shape measurement of micro-objects using a common-path digital holographic microscopy (CDHM) with dual wavelength

Abstract

Digital holography microscopy (DHM) allows fast, nondestructive, high resolution and full-field 3D shape measurement of micro-objects. However, a drawback of many experimental arrangements of DHM is the requirement for a separate reference wave, which results in a measurement stability and interference fringe contrast decrease. In this paper, a common-path DHM (CDHM) is explored which only requires a single object illumination wave. Due to the fact that conventional phase unwrapping algorithms are not suitable for the complex and step surface of object, the dual wavelength linear regression phase unwrapping algorithm is introduced. By comparing two wrapped phase maps reconstructed at different wavelengths, the maps can be accurately unwrapped with straightforward and less timeconsuming. From the CDHM system and the phase unwrapping algorithm introduced, we experimentally obtained high quality depth profiles of micro-objects.