High-precision stepwise calibration method for binocular microscopic vision system with shallow depth of field

To address the challenges posed by the shallow depth of field in the Binocular Microscopic Vision System (BMVS) of the Ophthalmic micro-Surgical Robot (OmSR), a high-precision, stepwise calibration method, which utilizes predefined movements of the calibration plate, is proposed in this study. The method innovatively decomposes the calibration of camera parameters, thereby addressing the accuracy limitations inherent in the closed-form calibration method due to insufficient constraints. Furthermore, the method integrates plane-parallel constraints with bundle adjustment to achieve global parameter optimization. Compared to the classical Zhang’s method, the proposed method yields lower reprojection error and significantly improves three-dimensional measurement accuracy. Experimental results demonstrate that the BMVS parameters calibrated using the proposed method fully meet the precision requirements for the position measurement of the OmSR’s micro-forceps.