光阴极灵敏度(量子效率)是微光像增强器最重要和最基本的性能参数之一，它决定着微光成像系统在低照度下的视距和图像清晰度。根据半导体光电发射物理模型及普朗克黑体辐射理论，简介了光电发射5个环节(光子不完全吸收、GaAlAs／GaAs后界面、GaAs光阴极激活层体特性缺陷、GaAs光阴极表面位垒和GaAs光阴极－MCP之间近贴电场电子隧道效应)对光阴极量子效率的影响，给出了相关数学表达式。在假定5个环节子量子效率均为100%的前提下，估算出蓝延伸GaAs光阴极在(0．41～0．93)μm波段内的极限积分灵敏度，其值为6569μA／lm。文末，对此结果的意义给予评价。

The photocathode sensitivity is one of the most important and fundamental parameters of image intensifiers,which determines the performance of the photo-electronic imaging system under low-light-level conditions. Based on the physical model of semiconductor optoelectronic emission and Plank theory of black-body radiation,the effect of 5 sub-processes on photocathode quantum efficiency is summarized. Several expressions are given to calculate the sensitivity limit under the assumption of 100% sub-quantum efficiencies in the 5 subprocesses. The ultimate sensitivity of 6 569 μA/lm is obtained for an extended blue GaAs photocathode in the waveband of (0.41～0.93)μm.