Automated Reference Arm for Online Surface Tracking in Optical Coherence Tomography

Abstract

Maintaining a stable sample position is a critical challenge in optical coherence tomography (OCT), as axial motion can shift the surface outside the imaging range or degrade image quality, particularly at high fringe frequencies with low signal-to-noise ratio (SNR). This work presents an automated motorized reference armfor online surface tracking in OCT. The surface position is extracted from OCT B-scans using an ROI-guided, column-wise infinite impulse response (IIR) edge detection method that directly identifies the air–sample interface from the depthwise filter response. The detected surface position is used as feedback for a proportional–integral–derivative (PID) controller, which adjusts the reference arm to maintain a predefined axial setpoint. The controller is integrated into a real-time OCT system and evaluated. Results demonstrate stable surface tracking with low residual error and robust step response. This approach enables OCT imaging for dynamic and robotic scanning applications without manual reference armadjustment.