Acousto optic modulation based en face AO SLO OCT

Abstract

Standard optical coherence tomography (OCT) is based on acquiring depth profiles (A-scans) which can be very fast using Fourier domain techniques because the whole imaging depth can be recorded simultaneously. However, while this approach is well suited for most OCT applications, an alternative scanning protocol might bear some advantages compared to the standard imaging protocol. This becomes evident when approaching microscopic transverse resolution which results in a corresponding decrease of depth of focus (DOF) down to a few tens of micrometers. This chapter describes several aspects of the en-face OCT technology. Thereby the focus is laid on en-face OCT that uses acousto optic modulation in order to generate a carrier frequency for the OCT signal. One advantage of the en-face OCT technique is the ability to shift the focal plane simultaneously with the coherence plane through the tissue which preserves the high transverse resolution throughout imaging depth. Currently the main application of this technique can be found for retinal imaging with high transverse resolution which enables the investigation of the 3D structure of cone photoreceptors over time. Since the scanning protocol of the en-face OCT is identical to scanning laser ophthalmoscopes, it is ideally suited for a combination with adaptive optics. Thereby the transverse resolution can be further increased which allows for in vivo visualization of very small cellular structures such as rod and cone photoreceptors.