Abstract
Purpose :
Optical coherence tomography (OCT) records depth-resolved holographic information (phase and amplitude) of the light scattered in biological tissues. Holographic retina imaging (Puyo et al., 2018) as well as OCT imaging with defocus and aberration correction was demonstrated using using fast cameras to record the interference pattern of the full lateral field of view (Hillmann et al., 2016, Sudkamp et al., 2018). Refocusing and aberration correction was also demonstrated for scanned OCT (Shemonski et al., 2015, Franke et al., 2023).
Whereas the FF-OCT with spatial coherent illumination (SC-FF-OCT) has virtually no limitation in the refocussing depth and does not sacrifice resolution or image quality, the situation is more complex in scanned OCT. Confocal gating and mixing of the different spatial frequencies in the illumination and detection influence the imaging process. In addition, motion of the tissue introduces spatially varying phase noise, which is expected to strongly influences the refocusing capability.
The objective of this work is to explore the quality of in-focus and defocused images of fiber-based point-scanning OCT imaging.
Methods :
The imaging process of a single-mode fiber-based point-scanning FD-OCT and a SC-FF-SS were numerically simulated for different objects. Simulation results were compared with experimental measurements.
Results :
The confocal properties of the point-scanning OCT systems determine the confocal OTF and the lateral resolution. A defocus-independent resolution is possible, with the refocusing depth only beeing limited by the confocal gating. Simulations and experiments show that phase noise plays a more critical role on the refocusing than previously presumed. Phase instability leds to a loss of SNR and lateral resolution for layers outside the focal plane.
Conclusions :
Lateral resolution should be fully retrievable when refocusing scanning OCT images as long as the SNR is high enough and phase noise can be avoided. The effects of motion induced phase noise can be mitigated through faster systems and improved algorithms for motion correction. Digital refocusing presents itself as an important evolution of scanning OCT.
Franke et al. (2023). SPIE, Vol. 12367-17,
Hillmann et al. (2016). Sci Rep 6, 35209.
Puyo et al. Biomed Opt Express 9, 4113-4129.
Shemonski et al. (2015). Nat Photon 9, 440 - 443.
Sudkampet al. (2018). Opt. Lett. 43, 4224-4227.
This abstract was presented at the 2024 ARVO Imaging in the Eye Conference, held in Seattle, WA, May 4, 2024.