Phase imaging based on modified transport of intensity equation using liquid crystal variable retarder with partial coherent illumination

Abstract

In this paper, we demonstrate a non-interferometric phase imaging technique based on modified transport of intensity equation (TIE) through a liquid crystal variable retarder (LCVR) and partial coherent illumination. The LCVR has been used in pure phase shifter configuration for creating refractive index variation. The modified TIE eliminates the need of mechanical displacement of camera or object, since it needs recording of only two intensity images with different refractive indices. A light-emitting diode (LED) has been used as a light source to avoid the usual speckle problems in coherent imaging. Although LCVR is a versatile device, its application towards phase recovery is less studied. The applicability of the method has been demonstrated through imaging a USAF resolution chart, ultra-violet glue drop, micro-lens, and onion’s peel. The result of onion’s peel has also been compared with a commercial bright-field microscope.