Quantitative Carré Differential Interference Contrast Microscopy to Assess Phase and Amplitude

We present a method of using an unmodified differential interference contrast microscope to acquire quantitative information on scatter and absorption of thin tissue samples. A simple calibration process is discussed that uses a standard optical wedge. Subsequently, we present a phase-stepping procedure for acquiring phase gradient information exclusive of absorption effects. The procedure results in two-dimensional maps of the local angular (polar and azimuthal) ray deviation. We demonstrate the calibration process, discuss details of the phase-stepping algorithm, and present representative results for a porcine skin sample. © 2011 Optical Society of America OCIS codes: 120.3180, 120.5820, 170.0180, 170.3660, 170.6935, 180.3170. It is evident that the first-order properties of light (color, scatter direction, polarization) can be used to infer properties of biological tissues with which it has interacted. Further, tissue structures and the instrumentation for acquiring local properties of the scattered light are often such that the spatial coherence length (a second-order property) of the illumination is on the order of the scale size of the inhomogeneity [1]. The coherence of the field affects its interaction with the medium, and in turn the coherence evolves in response to its interaction with the medium [2,3]. Thus, we are motivated to understand how coherence propagates within complex media.