Simultaneous low coherence interferometry imaging at two depths using an integrated optic modulator

A Mach-Zehnder unbalanced LiNbO3 integrated modulator with independent control of the phase of each arm is incorporated into the reference arm of a low coherence interferometer set-up. Using different RF modulation frequency and processing electronics tuned to these frequencies, the system can be used for simultaneous interrogation of the signal reflected from two different depths in tissue or from two different axial positions in profilometry. When a pair of XY scanning mirrors are incorporated into the sensing arm, then two en-face images from different axial positions can be simultaneously produced. The depth separation between the axial positions of the points or layers interrogated is equal to half of the modulator path difference. The operation of the system is illustrated by displaying simultaneously two images from a coin. © 2001 Elsevier Science B.V.