An aberrated imaging system PSF is broadened; this broadening is responsible of the blurring of the images. A lot of effort has been carried out to correct the effects of aberrations on OCT images for eye examination or biological samples. We have worked on quantifying the effect of geometrical aberrations on Full-Field OCT images and found that there is mostly no loss of resolution but a decrease of the signal level. This is obviously why we use these signals as metric to correct the wavefront distortion. Moreover we found that this absence of blurring, which is due to the fact that we record the dot product of a diffraction limited reference signal and the distorted sample signal, is specific to the use of an incoherent illumination and did not show up with OCT approaches that use spatially coherent sources. More precisely the loss in signal is roughly proportional to the square root of the Strehl ratio: for example, a Strehl ratio of 1/9, which is considered to give a low quality image, would only be 1/3 in Full-Field OCT while keeping the sharpness of the image. Using both an USAF resolution target and a transmissive SLM we have demonstrated this unique feature of sharpness conservation. It was also confirmed by using biological samples. We think that we can thus restrict the aberration corrections in eye examination to the main aberrations (e.g. focus and astigmatism) that will increase the speed of the correction.
Peng Xiao, Mathias Fink, and A. Claude Boccara, "An optical tomography PSF almost insensitive to aberrations: the benefit of a spatial incoherent illumination
(Conference Presentation)," Proc. SPIE 9717, Adaptive Optics and Wavefront Control for Biological Systems II, 97170I (Presented at SPIE BiOS: February 14, 2016; Published: 27 April 2016); https://doi.org/10.1117/12.2210950.4848767668001.
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