Diffuse light suppression of back-directional gating imaging in high anisotropic media

We experimentally demonstrate that back-directional gating in an imaging setup can potentially remove unwanted diffuse light to improve the contrast of an object embedded in a high anisotropic surrounding medium. In such back-directional gating, the high anisotropic property of the surrounding medium can serve as a waveguide to deliver the incident light to the embedded object and to isolate the ballistic or snake-like light backscattered from the object in a moderate depth. We further discuss the effects of back-directional gating in the image formation in terms of the image resolution and the depth of field. Although backscattering detections of biological tissue have recently received considerable attention, we, for the first time to our knowledge, show its potential advantage for the contrast improvement in high anisotropic media.