为了满足目镜轻小的功能需求，优化设计了三种不同结构的长出瞳距目镜。三种目镜的系统参数相同，在出瞳直径为7 mm的前提下实现了40 mm的出瞳距，焦距为26 mm，视场为32 °。首先，设计了由折射球面构成的纯折射式目镜，由五片透镜组成。其次，添加一个非球面优化设计得到了含有非球面的折射式目镜，由四片透镜组成。最后，添加一个衍射元件优化设计得到了折衍射目镜，由三片透镜组成。结果表明：在40 lp/mm频率处，含有非球面的折射式目镜的所有视场MTF都超过0.35，其中，0 °的中心视场MTF达到0.67；对比第一种纯折射式结构目镜，其长度减小了16.66%，重量减轻了35.88%，成像质量更好。折衍射目镜所有视场的MTF都高于0.40；对比第二种目镜，第三种目镜的长度减小了15.43%，重量减轻了37.40%，像质也得到改善。

In order to meet the light, small requirements of eyepieces, three types of eyepieces with long exit pupil distance were designed. The system parameters of the three eyepieces were the same: under the premise that the diameter of 7 mm exit pupil, 40 mm exit pupil distance was realized, the exit pupil distance was 40 mm, the exit pupil diameter 7 mm, the focal length 26 mm, and field of view was 32°. Firstly， a pure refractive eyepiece composed of five lenses was designed. Secondly, a refractive eyepiece with an aspheric surface was obtained by introducing an aspheric surface and through optimizing design, which consisted of four lenses. Finally, a diffractive element was introduced to obtain a refractive diffractive eyepiece composed of three lenses. The results show that MTF of refractive eyepiece with aspheric surface is higher than 0.35 for all fields of view at the frequency of 40 lp/mm, and the MTF of 0° field of view is above 0.67. Compared with the first pure refractive eyepiece, the length is reduced by 16.66%, the weight is reduced by 35.88%, and the imaging quality is better. The MTF of all fields of view is higher than 0.40 for the refractive diffractive eyepiece. Compared with the second eyepiece, the length is reduced by 15.43%, the weight is reduced by 37.40%, and the image quality of the third eyepiece is improved.