High precision corneal curvature radius measurement system

To achieve accurate alignment of the imaging keratometer along the optical axis and improve the measurement accuracy of corneal curvature, we design a high precision imaging corneal curvature measurement system. The imaging light source, imaging optical system and interferometry system of the measurement system are studied. A light source is formed using uniform irradiation of the target ring with an LED array; The imaging objective lens adopts a double telephoto lens to enlarge the depth of its field, which is conducive to the measurement of alignment. Meanwhile, the magnification of the imaging objective lens are not affected by the depth of field. By using low coherent interferometry, the distance between the corneal vertex and the measured light source is accurately measured using a grating ruler to monitor the position of the scanning mirror. In this paper, the stability of the imaging objective magnification and the error of the corneal curvature measurement of the system are analyzed, and an experimental prototype is made based on the theory. The designed prototype is used to test the standard corneal simulators and the measurement accuracy of the system is up to ±0.02 mm, which basically meets the requirements of corneal curvature measurement.