Dual-wavelength digital holographic shape measurement using speckle movements and phase gradients

Abstract

A new method to measure shape by analyzing the speckle movements in images generated by numerical propagation from dualwavelength holograms is presented. The relationship of the speckle movements at different focal distances is formulated, and it is shown how this carries information about the surface position as well as the local slope of the object. It is experimentally verified that dual-wavelength holography and numerically generated speckle images can be used together with digital speckle correlation to retrieve the object shape. From a measurement on a cylindrical test object, the method is demonstrated to have a random error in the order of a few micrometers. © The Authors.