Refractive index tomography of turbid media by bifocal optical coherence refractometry

We demonstrate tomographic imaging of the refractive index of turbid media using bifocal optical coherence refractometry (BOCR). The technique, which is a variant of optical coherence tomography, is based on measurement of the optical pathlength difference between two foci simultaneously present in the medium of interest. We describe a new method to axially shift the bifocal optical pathlength, thus, avoiding the need to physically relocate the objective lens or the sample during an axial scan, and present an experimental realization based on an adaptive liquid-crystal lens. We present experimental results, which demonstrate refractive index tomography of a range of turbid liquid samples, and also in situ living tissue. BOCR has potential for in vivo refractive index tomography of biological tissue.