Optical-image communication through random-phase propagation channels using phase-shifting coding

Abstract

We propose an optical-image communication system robust to random-phase propagation using phase-shifting (PS) image coding. That is, this optical-image communication system is based on digital PS interferometry principles. Each pixel of the parallel transmitted image is coded as the phase of a sequence of N phase-shifted fringe patterns. The temporal fringe patterns may be displayed on a TV screen (or a multimedia projector) for transmission through the random-phase channel. At the receiver, the PS fringe patterns are digitized with a telescopic digital camera. The received fringes are phase-demodulated using an N-steps least-squares PS algorithm (LS-PSA). We show that the received, phase-demodulated images are less blurred and have better contrast than any received image without PS coding. We propose and analyze a mathematical model for the received PS fringes degraded by random-phase propagation. This PS communication system can also be used for robust optical communications through random refractive media such as underwater, air-water, or random-thickness textured glass. In particular, we show experiments for LS-PSA imaging through textured-glass, obtaining sharper images. As far as we know, this is the first time that PS interferometry has been used for parallel optical-image communication through random-phase channels.