Gaussian beam deconvolution in optical coherence tomography

Abstract

Optical coherence tomography (OCT) is an emerging, high-resolution near-infrared imaging and microscopy technique. The axial and transverse resolutions in OCT can each be analyzed independently, with the axial resolution inversely proportional to the spectral bandwidth of the optical source and the transverse resolution defined by standard Gaussian beam optics. While high numerical-aperture objectives are preferred to improve the transverse resolution, the reduced confocal parameter limits the depth-ranging capabilities of OCT and more complex en face imaging with focus tracking must be employed. We present a method for increasing the apparent transverse resolution in OCT outside of the confocal parameter using Gaussian beam deconvolution of adjacent axial scans, and thereby reducing the limitations associated with the hourglass profile of a tightly focused Gaussian beam. Specifically, our method determines how measurements depend on the object when blurred with a Gaussian beam, and subsequently finds an estimate of the original object. Possible reconstruction estimates are explored and evaluated using a variety of regularization techniques as well as estimation maximization algorithms. Numerical simulations demonstrate effectiveness of each technique. When applied to experimentally-acquired OCT data, the use of these algorithms can improve the apparent transverse resolution outside of the confocal parameter, extending the comparable confocal parameter range along the axial direction. These results are likely to further improve the high-resolution cross-sectional imaging capabilities of OCT.