Optimization design and realization of a keratometer

To realize a simplified keratometer, we proposed a design proposal based on corneal reflex imaging. Six pointolites which arranged in a regular hexagon were used to emit parallel light to the surface of a cornea and were reflected by the cornea. Then the image was captured by a telecentric optical system in the object space to a CMOS camera. In order to obtain the corneal curvature, the distance between two pointolites located on the regular hexagonal diagonal in the corneal reflection images were calculated by using the center of gravity algorithm. The imaging quality, measuring range and measuring precision of the system were theoretically analyzed, and the Ziess's model eye and human eyes were used to conduct experiments to verify the theoretical analysis results. The experiment results have shown that the precision of the measurement error is ±0.02 mm and the measurement range is from 5.5 mm to 11.6 mm (30 m-1 to 60 m-1 in diopter of cornea). The research will provide technical supports for the design and optimization of automatic keratometer.