Depth Resolved Polarization Sensitive Imaging of the Eye using a Confocal Mueller Matrix Ellipsometer – Proof of Principle

Abstract

Abstract: : Purpose:Conventional imaging systems can only be used to record the intensity of light that has been scattered from the object under observation. Hence, some tissues appear to be homogenous even when they may possess some kind of internal structure. In this work we discuss a new technique to obtain polarization-sensitive three dimensional images, which can reveal the anatomical condition of the ocular tissue that possesses polarization dependent signatures, such as the retinal nerve fiber layer and the cornea. Methods:The state of polarization of light can be fully described by a 4-vector (the Stokes vector) and the effect of any optical element that modifies the state of polarization can then be represented by a 4*4 matrix (the Mueller matrix). We used a Division-of-Amplitude Mueller matrix ellipsometer in which the state of polarisation of the light incident on the sample was modulated using a pair of Pockel's cells. We measured simultaneously the 4 components of the Stokes vector of the light that was scattered from the sample and passed through a confocal imaging optical system. For these measurements we used four linearly independent polarisation analysers. We recorded the 4 modulated signals and used Fourier analysis to obtain the 16 Mueller matrix elements of the sample. Results:We present depth resolved measurements of different polarizing and birefringent stacked samples. Conclusions: To the best of our knowledge we have presented for the first time the combination of a confocal imaging system with a Mueller matrix ellipsometer as a polarization-sensitive imaging device with depth resolution. We discussed the effects of using a confocal optical system on the measurement of the Mueller matrix that represents a sample. One of the advantages of the ellipsometer we used is the high speed of the measurements. This important feature may allow our technique to be implemented on devices such as a Confocal Scanning Laser Ophthalmoscope.

Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, S • retina • nerve fiber layer