planar mirror meaning in English

平面反射镜
平面镜

The beam - splitter comprises three pairs of fully reflecting planar mirrors and partially reflecting planar mirrors . according to the workspace size and experimental requirement , they were placed with a distance of 195 - cm between two mirrors
空间分光延时系统由三对全反镜和部分反射镜构成，根据实验平台大小和实际需要调整镜片之间的距离，使相邻光束之间的光程差为390cm 。