Differential confocal self-collimation method for high-accuracy measurements of lens decentration

A differential confocal self-collimation decentration measurement method (DCSDM) is proposed. It uses the differential confocal method to precisely identify the center and vertex positions of the tested lens surface, thereby obtaining the radius of curvature. Then, it uses the self-collimation light-path to detect the position of the reflected light during the rotation of the tested surface, thereby obtaining the center bias. Finally, it calculates the decentration. Theoretical analysis and experiments indicate that DCSDM achieves an accuracy of 0.069". Compared with existing methods, DCSDM significantly reduces the focusing error by using differential techniques, prevents multiple clamping errors by integrating the radius and center bias measurements in one system, and is a feasible method for decentration measurement.