Martinelli R U
Appl Opt. 1973 Aug 1;12(8):1841-5. doi: 10.1364/AO.12.001841.
In proximity focused electrostatic image tube; spatial resolution is a strong function of the cathode flatness.Topographic irregularities of the cathode surface establish transverse electric fields near the cathode.The fields impart a component of transverse momentum to the emitted electron, which, in turn,degrades the spatial resolution characteristic of the system. Calculations based on a simple model of a corrugated cathode show that, under a typical set of operating conditions, the point at which loss of resolution becomes considerable is 60 cycles/mm for a bump height of 0.2 microm and a bump period of 1 microm. For the resolution to be comparable to that predicted for a perfectly flat GaAs negative electron affinity (NEA) cathode, which is 160 cycles/mm, the bump period must be 0.1 microm, and its height must be 0.02 microm. Such small bumps represent a relatively smooth surface. Observations of surface irregularities on related NEA surfaces indicate that the bump period and height are about 1.0 micro and 0.2-0.5 microm, respectively, so that the spatial resolution in these cases is limited by the deviation from flatness as opposed to being limited by the finite random velocities of the emitted photoelectrons.
在近贴聚焦静电成像管中，空间分辨率与阴极平整度密切相关。阴极表面的形貌不规则会在阴极附近产生横向电场。这些电场会给发射出的电子赋予一个横向动量分量，进而降低系统的空间分辨率特性。基于波纹状阴极的简单模型进行的计算表明，在一组典型的工作条件下，对于凸起高度为0.2微米、凸起周期为1微米的情况，分辨率开始显著下降的点为60线对/毫米。为了使分辨率与预测的完美平坦的砷化镓负电子亲和势（NEA）阴极（160线对/毫米）相当，凸起周期必须为0.1微米，高度必须为0.02微米。如此小的凸起代表了一个相对光滑的表面。对相关NEA表面的表面不规则性观察表明，凸起周期和高度分别约为1.0微米和0.2 - 0.5微米，因此在这些情况下，空间分辨率受平整度偏差的限制，而非受发射出的光电子有限随机速度的限制。
