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六、各种象差影响下的传递函数由光学可知,一个系统是否具有相干性并非固定不变的。文献[12]曾经明确指出:“凡是带照明的光学成象系统,都是在部分相干条件下工作的”。对于静电阴极透镜系统,光电阴极可视为本身发射电子的物,但为了便于讨论,这里设想把它分离为电子源和被照物体两个部分,前者具有阴极本身的发射特性(即初能量分布和初角度分布);后者则具有透过函数F_0(x_0,y_0)——由它反映阴极输入端所接受的图象的强度分布。这两者结合,就再现了实际的光电发射。因此,就可以运用光学中部分相干的理论来研究静电阴极透镜系统的成象问题。
Sixth, the transfer function under the influence of various aberrations can be seen by optics, whether a system has coherence is not fixed. It has been pointed out clearly in [12] that “all optical imaging systems with illumination work under partially coherent conditions.” For an electrostatic cathode lens system, a photocathode may be considered as an electron-emitting material itself, but for the sake of discussion, it is assumed herein to be separated into two parts, an electron source and an object to be photographed, the former having the emission characteristic of the cathode itself And initial angle distribution); the latter has a transmission function F_0 (x_0, y_0) - which reflects the intensity distribution of the image accepted at the cathode input. The combination of the two reproduces the actual photoemission. Therefore, the theory of partial coherence in optics can be used to study the imaging problems of electrostatic cathode lens systems.