Performance of passive night vision systems using image intensifier tubes. I Influence of the photocathode's spectral response

A comparison is made of the performance of night vision aid systems equipped with image intensifier tubes using trialkaline photocathodes and using photocathodes of the III-V compound type. The method consists of calculating the maximum distance at which targets of different kinds can be seen as a function of illumination level. The aim is to show the importance of sensitivity and of the shape of the spectral response curve in performance. In addition, the influence of numerous parameters is studied such as the spectral reflectivity of targets, the luminance of the night sky, the photonic noise, the thermionic emission of the photocathode and the noise factor of the amplifying stage. Finally, mention is made of the influence of atmospheric scattering effects on the practical range of devices.