Implicit Disparity-Blur Alignment for Fast and Precise Autofocus in Robotic Microsurgical Imaging

Creating an intelligent surgical environment requires not only advanced robotic systems but also optimized microscopic imaging. However, autofocus remains a fundamental challenge, with current methods suffering from slow iterative processes or directional ambiguity, which compromises real-time performance. This paper presents an implicit disparity-blur alignment approach for robotic microsurgical autofocus, integrating stereo geometry's monotonic depth cues with de-focus characteristics for rapid convergence. A novel physics-guided dual-stream network is developed to encode implicit depth representations through hierarchical cross-pathway feature fusion, enabling reliable focus prediction without explicit stereo matching in blur-degraded regions. An ROI-aware attention module is proposed to dynamically optimize focus-critical regions, coupled with learnable physics-guided kernel learning for precise Z-offset estimation. The approach achieves a top directional accuracy of 94.85% and a single-pass focus error of 0.20 mm with an inference time of 53 ms on a surgical dataset, which outperforms state-of-the-art methods in reducing iteration count by 22.8% and inference time by 51.8%. An intelligent robotic microscope prototype is developed, with validation through ex vivo tests demonstrating its ability to enable fast and precise multi-region focusing for microsurgeries.