也谈夫朗和费衍射近似

Study on Fraunhofer diffrsction approximation

分析信息光学和物理光学中夫朗和费衍射的差别 ,指出在研究单个物体的夫朗和费衍射二者的一致性 ,根据普适的夫朗和费衍射的定义 ,导出夫朗和费衍射的近似条件。讨论各种情况下该近似条件所体现出来的含义 ,实际测量中考虑残差时 ,被测物和衍射角的大小与测量准确度有关系 ,同时还得出 ,菲涅尔近似的衍射角受限 ,随着衍射距离的增大 ,观察屏中心区的菲涅尔衍射近似逐渐变为外环的夫朗和费衍射近似 ,当用物 -像法测微物体时 ,除满足傍轴近似等条件外 。

The difference of Fraunhofer diffraction between Information Optics and Physical Optics is analysed, the consistence of which is pointed out about one single object. According to the accustomed definition of Fraunhofer diffraction, approximation desire of which is acquired. The meanings in many cases are discussed. As the survival errors are calculated, Measurement correctness is related to the dimensions of object and diffraction angle. It can be obtained that diffraction angle of Fresnel approximation is limited. With diffraction distance increased, Fresnel approximation in the screen's centre turns into Fraunhofer approximation. Besides the condition of near axis, diffraction angle of Fresnel approximation can be met while using method of object-image to measure small objects.