Time-Gated Holographic Imaging Using Photorefractive Media

摘要

Photorefractive holography is a whole-field, coherence-gating technique for 3-D imaging through turbid media that offers a unique mechanism to discriminate against a background of diffuse light. In contrast to the well-established technique of optical coherence tomography, it is a whole-field imaging technique and may be implemented with light sources of arbitrary spatial coherence, including low cost LEDs and broad-stripe, multimode diode lasers. One drawback of using broadband sources, such as LEDs, for off-axis holographic imaging is the "walk-off' resulting from the short temporal coherence length that limits the field-of-view. Furthermore, the non-collinear geometry required for off-axis holography can introduce significant image aberration. In this paper we discuss these design considerations for various sources. We have addressed the issue of walk-off for sources of arbitrary bandwidth and have designed an off-axis holographic imaging system based on a Michelson interferometer with a collinear beam geometry that minimizes aberration. In this paper we review our work with high-powered LEDs and discuss these issues associated with spatially incoherent sources. Also, we present a novel, spatially coherent, broadband diode-pumped laser source that may also find application in OCT.