The Image Quality of an Image Intensifier Expressed in terms of its Equivalent Quantum Efficiency

Abstract

This chapter discusses the image quality of an image intensifier expressed in terms of its equivalent quantum efficiency. The performance of a detector in recording an optical image can only be fully described when both signal and noise in the image can be specified for an input of any spatial frequency and any spectral content. An experiment was carried out in which the granularity of photographic images was measured when using an intensifier over a range of gains. These measurements have shown that a further source of granularity can exist in the intensifier because of local variations in intensifier gain, and that under certain conditions these provide the dominant limitation in image quality. The result, of a photoelectron leaving the photocathode will follow some probability distribution, which will be independent of its point of origin. In the absence of gain variations in the intensifier the number of stored photons at low gains should be determined primarily by the film. The gain variations for the brightness distribution for single-photoelectron events are also elaborated later in the chapter.