为减小成像角膜曲率计沿光轴方向的对准误差, 提高角膜屈光度测量精度, 设计一种高精度成像角膜曲率计光学系统。光学系统包括成像系统和低相干干涉测量系统。成像系统由成像物镜、角膜和测量靶环构成, 其中成像物镜采用双远心光路设计; 低相干干涉测量系统采用光栅尺实现扫描反射镜的位移测量, 再通过低相干干涉信号对角膜顶点和测量靶环进行定位, 实现了对角膜顶点和测量靶环距离间的精确测量。成像物镜在最大空间频率为70 lp/mm处的调制传递函数大于0.4, 畸变小于0.05%。设计结果表明, 该系统结构紧凑, 成像质量好, 操作简单, 满足成像角膜曲率计对角膜屈光度的高精度测量需求。

In order to reduce the alignment deviation of the imaging keratometer along the optical axis and improve the measurement accuracy of corneal diopter, a high precision imaging keratometer optical system was designed. The optical system includes imaging system and low coherence interferometry system. The imaging system consists of imaging objective, cornea, and measurement target ring, wherein the imaging objective lens adopts a double telocentric optical path design. The low-coherence interferometry system uses the grating scale to measure the displacement of the scanning mirror, and then locates the vertices of the cornea and the measuring target ring by low-coherence interference signals, achieving accurate measurement between the apex of the cornea and the distance of the measuring target ring. The imaging objective has a modulation transfer function greater than 0.4 at a maximum spatial frequency of 70 lp/mm, the distortion is less than 0.05%. The simulation results show that the system has a compact structure, good imaging quality and simple operation. It meets the demand for high precision measurement of corneal refractive power by an imaging keratometer.