Using the Optical Code for Phase Analysis of the Fiber-Optic ESPI Set-Up

Abstract

Reliable information about object properties by applying ESPI (Electron Speckle Pattern Interferometry) method strongly depends on quality of speckle images. Acquisition of information about object is resulted as optical setup performance as digital processing. Digital phase extraction is the sequent step in image processing after optical acquisition. High focus quality, uniform illumination of object and CCD camera chip properties are the important parameters for consequence image processing. “Sharp focus” of speckle image on CCD camera is one of these features that would determine the object region of interest. As a rule the speckle images, speckle correlation distances and consequently unwrapped phase map suffer by distortion and brightness unevenness of image. It leads to cutting the field of credence of ESPI method. The use of ZEMAX’s Image Analysis, Illumination and Wavefront Map features for predicting and verifying the performance of optical part of fiber‐optic ESPI set‐up designs will be discussed. For digital processing of speckle images obtained we made use of a spatial phase shifting method by LabVIEW that permits the quantitative analysis of phase differences. The work results proof that ZEMAX Image Analysis is a valuable tool for ESPI designs and visualizing ESPI performance before a prototype is built. Optical image processing is the cumbersome part of optical system design, but thanks to the optical code we have possibility to simulate optical components performance including optimization.