Correction of coherence gate curvature in high numerical aperture optical coherence imaging

We present a method for correcting coherence gate curvature caused by scanning-induced path length variations in spectral-domain high-NA optical coherence imaging systems. These variations cause curvature artifacts in optical coherence tomography and effectively restrict the field of view in optical coherence microscopy (OCM). Here we show that the coherence gate curvature can be measured and corrected by recovering the phase of the analytic signal from a calibration image. This phase information can be used directly to process OCM images allowing the coherence gate curvature, as well as any order of system dispersion, to be corrected in a computationally efficient manner. We also discuss the use of various image quality metrics that can be used to adjust the calibrated phase in order to keep the coherence and confocal gates aligned in tissue. (C) 2010 Optical Society of America