GRIN lens based polarization endoscope – from conception to application

摘要

Graded index (GRIN) lenses focus light through a radially symmetric refractive index profile. It is not widelyappreciated that the ion-exchange process that creates the index profile also causes a radially symmetricbirefringence variation. This property is usually considered a nuisance, such that manufacturing processes areoptimized to keep it to a minimum. Here, a new Mueller matrix (MM) polarimeter based on a spatiallyengineered polarization state generating array and GRIN lens cascade for measuring the MM of a region of asample in a single-shot is presented. We explore using the GRIN lens cascade for a functional analyzer tocalculate multiple Stokes vectors and the MM of the target in a snapshot. A designed validation sample is usedto test the reliability of this polarimeter. To understand more potential biomedical applications, human breastductal carcinoma slides at two pathological progression stages are detected by this polarimeter. The MM polardecomposition parameters then can be calculated from the measured MMs, and quantitatively compared withthe equivalent data sampled by a MM microscope. The results indicate that the polarimeter and the measuredpolarization parameters are capable of differentiating the healthy and carcinoma status of human breast tissueefficiently. It has potential to act as a polarization detected fiber-based probe to assist further minimally invasiveclinical diagnosis.