Angle-resolved chromatic confocal microscopy for accurate free-form surface reconstruction employing back focal plane projection and ANN modeling

The increasing demand for accurate surface morphology reconstruction in semiconductor manufacturing and precision optics has exposed limitations in conventional optical measurement techniques, particularly when applied to discontinuous or inclined surfaces. These limitations often stem from optical distortions that introduce significant measurement errors. To address this challenge, we propose an angle-resolved chromatic confocal microscopy (AR-CCM) system that combines chromatic confocal microscopy with Back-Focal Plane (BFP) imaging. The proposed method leverages BFP imaging to extract surface inclination angles, thereby mitigating errors induced by surface tilt and system aberrations. Two models are developed: a surface inclination estimation model, which determines azimuth and altitude angles, and an angle-resolved depth response model, which integrates these angles with spectral data for enhanced surface reconstruction. Experimental results demonstrate that the AR-CCM system achieves over a 20% reduction in height measurement errors on inclined surfaces. The proposed approach offers a universal, efficient solution for optical metrology and holds promise for widespread application in complex surface characterization.