Review Lecture Electronic Aids to Night Vision

The human eye is a very sensitive and versatile image detector, but has a number of physical limitations. The most important of these at very low light levels is the restriction in sensitivity resulting from the statistical fluctuations in the numbers of detected photons. It is shown how electronic image intensifiers can provide a fundamental improvement in this situation by capturing a larger fraction of the available photons and using these more efficiently. The important parameters of such instruments are discussed, together with the principles of operation of their most significant component: the image intensifier tube. This is followed by a more detailed discussion of the possible performance of night vision equipments based on different types of tube, both for direct and remote viewing applications.