Investigating the impact of different time delays between OCT signal and k-clock signal on the structural and vascular imaging in SS-OCT.

High-quality swept-source optical coherence tomography (SS-OCT) imaging systems require precise synchronization between the OCT signal and the k-clock signal. However, in practical applications, an uncertain time delay between these signals can cause inaccurate k-space sampling, leading to degraded imaging resolution. This study first simulates the axial resolution degradation curve caused by varying time delays and experimentally validates the results. Additionally, the effects of different time delays on both OCT structural and blood flow images are systematically investigated through experiments. To address this issue, a numerical calibration method is implemented to compensate for the nonlinear phase component. This approach involves acquiring two reflection signals at different depths, unwrapping the phase, performing high-order polynomial fitting, and removing nonlinear phase components induced by time delay, which effectively corrects the resolution degradation. Experiments conducted on semi-transparent white tape, blood flow phantom, and human nailfold demonstrate that the proposed correction algorithm significantly improves the axial resolution of both structural and blood flow images. The findings indicate that our investigation and the developed calibration method are instrumental in reconstructing high-resolution SS-OCT images, which are essential for accurate diagnosis and effective treatment monitoring in clinical applications.