Hybrid configuration for simultaneous en-face OCT imaging at different depths

By dividing both the object and reference beam in an OCT interferometer, two independent OCT imaging channels are assembled. The depth scanning proceeds simultaneously in the two OCT channels and from the same range, however a differential optical path difference can be introduced between the two channels. In this way, two simultaneous images are generated where the depth differs in each pixel by the differential optical path difference. A dual OCT system working at 850 nm was devised and we demonstrate the capability of the method by simultaneously acquiring images from the optic nerve and fovea of a volunteer. The configuration devised insures a strict pixel to pixel correspondence between the two images irrespective of the axial eye movements while the depth difference between the corresponding pixels is exactly the differential optical path difference. The images are collected by fast en-face scanning (T-scan) which allows both B-scan and C-scan acquisition.