相比传统角膜曲率仪引入双像棱镜进行角膜屈光度的测量，提出一种新型的基于光标成像原理的角膜曲率仪光学系统，其结构紧凑，操作简单，具有满足要求的屈光度测量精度和测量范围。光学系统包括成像系统和照明系统两部分，成像系统由投影物镜、角膜、摄影物镜三部分构成，采用了外调焦方式；照明系统采用了柯勒照明方式，可以实现环形光标、角膜前表面和CCD接收器像面的均匀照明。成像系统的像面分辨率达到133 lp/mm，畸变小于1%，角膜屈光度测量精度为0.25 D（曲率半径测量精度0.02 mm），测量范围为30~60 D（曲率半径测量范围5.5~11 mm）。设计结果表明，该系统在满足角膜屈光度测量精度高和测量范围广的前提下，有效地实现了结构紧凑，操作简单的目的。

Compared with the traditional keratometer which adopts double image prism to measure the corneal refraction, a novel keratometer′s optical system, based on cursor imaging principle with impact structure and convenience in use, is proposed in this paper. The optical system includes imaging system and illumination system. Imaging system, which consists of projection objective, cornea and photographic objective, adopts exterior focusing model. Illumination system adopts Kohler illumination, which realizes uniform illumination on the ring cursor, anterior corneal surface and the image plane on the CCD receptor. The image resolution can achieve 133 lp/mm, and the distortion is less than 1%. The measurement accuracy of corneal refraction reaches to 0.25 D (0.02 mm for curve radius), and the measurement range is 30~60 D (5.5~11 mm for curve radius). With high measurement accuracy and a wide range of measurement for the corneal refraction, the optical system simplifies the keratometer′s structure and operation for practitioners effectively.