Postprocessing algorithms to minimize fixed-pattern artifact and reduce trigger jitter in swept source optical coherence tomography

Abstract

Abstract:We propose methods to align interferograms affected by trigger jitter to a reference interferogram based on the information (amplitude/phase) at a fixed-pattern noise location to reduce residual fixedpattern noise and improve the phase stability of swept source optical coherence tomography (SS-OCT) systems. One proposed method achieved this by introducing a wavenumber shift (k-shift) in the interferograms of interest and searching for the k-shift that minimized the fixed-pattern noise amplitude. The other method calculated the relative k-shift using the phase information at the residual fixed-pattern noise location. Repeating this wavenumber alignment procedure for all A-lines of interest produced fixedpattern noise free and phase stable OCT images. A system incorporating these correction routines was used for human retina OCT and Doppler OCT imaging. The results from the two methods were compared, and it was found that the intensity-based method provided better results. Duker, and J. G. Fujimoto, "Phase-sensitive swept-source optical coherence tomography imaging of the human retina with a vertical cavity surface-emitting laser light source," Opt. Lett. 38(3), 338-340 (2013).

Extended axial imaging range, widefield swept source optical coherence tomography angiography

“…Postprocessing reduced the TJA by introducing a wavenumber shift (k‐shift) in the interferograms of interest and by searching for the k‐shift that minimized the fixed‐pattern noise amplitude . Here, an optimized version of the method was used to increase the processing speed.…”

4 Optical Coherence Tomography Angiography

“…Within an OCT system, phase noise can arise from scanning mirrors or a swept-source laser. 25,26 Although several methods exist to compensate for phase noise 20,27,28 and improve system phase stability, [29][30][31][32] an alternative is to use the variation in amplitude or intensity of the OCT signal to detect flow instead.…”

Phase and amplitude correction in polygon tunable laser-based optical coherence tomography

“…where m s is the misplaced point in k-space, z is the depth of sample, and N is the total number of wavenumber samples. 12 The delays among different MZI signals were not integer multiples of the sampling interval; thus, after integer pixels shift, some misplacement may still remain in the time domain, m t ¼ 1∕2. To simply demonstrate the relationship between m s and m t , we assumed wavelength distribution in wavenumber domain was approximately linear with that in time domain, and thus, there was m s ≈ cm t , in which c ¼ N∕N t and N t was the effective signal point number in time domain.…”

“…6 Hence, phase instability has been a research focus, and some researchers have proposed reducing this impact by adding a stationary mirror or glass plate to the sample arm, [7][8][9] whereas others suggest aligning interference signals. [10][11][12] However, we determined that the difference in polygon mirrors causes phase instability and also output power and sweep range fluctuation in a polygon tunable laser. This creates vertical artifacts that can impair the recognition of samples and reduce interference signal utilization during phase correction, which will reduce the image axial resolution.…”