16 - Incoherent Illumination Tomography and Adaptive Optics

Summary

Optical tomography techniques have been widely used for imaging. Among those techniques, since its development optical coherence tomography (OCT) has played an important role in imaging biological samples, especially in eye examinations. The combination of OCT with adaptive optics (AO) for aberration correction to improve the OCT performance is one of the most impactful technique advances for non-invasive and high resolution imaging. In this chapter, we are going to discuss about an en face approach of OCT, Full-Field OCT or FFOCT, and about a compact AO-FFOCT system that was coupled with a transmissive liquid crystal spatial light modulator (LCSLM) to induce or correct aberrations. We will show that, with spatially incoherent illumination, the FFOCT system point spread function (PSF) is almost independent of aberrations that mostly induce a reduction of the signal level (signal to noise ratio) without broadening the PSF width. By comparing scanning OCT with spatially coherent illumination, wide-field OCT with spatially coherent illumination and FFOCT with spatially incoherent illumination, theoretical analysis, numerical calculation as well as experimental results are demonstrated to show this specific merit of incoherent illumination in FFOCT. We will also demonstrate a compact AO-FFOCT system in which the strict pupil conjugation is abandoned for low order aberrations correction. A wavefront sensorless method is used for distortion compensation by using the FFOCT signal as the metric based on the resolution conservation property of FFOCT. AO experiment results done with USAF resolution target and biological samples will be reviewed. And the potential of this AO-FFOCT system for retinal imaging will be discussed.