Phase estimation for global defocus correction in optical coherence tomography

In this work we investigate three techniques for estimation of the non-linear phase present due to defocus in optical coherence tomography, and apply them with the angular spectrum method. The techniques are: Least squares fitting the of unwrapped phase of the angular spectrum, iterative optimization, and sub-aperture correlations. The estimated phase of a single en-face image is used to extrapolate the non-linear phase at all depths, which in the end can be used to correct the entire 3-D tomogram, and any other tomogram from the same system.