Low Brightnees Photography with Electro-optical Intensifiers

Abstract

This paper deals with the development of a System for photography al low brightness level, comprismg highly luminous optical Systems and a large size brightness intensifier. Obvious requirements for such Systems are: large aperlure optics, large brightness gain, high-sensitivity emulsions and reosonabie resolution. Less obvious, but cqually important requirements are: large dimensions of the optics, high cathode sensitivily of the image tube and low “dark current”. The size of the optics and high cathode sensitivity are important because of the noise resulting from the statistical fluctuations of a limited number of effective electrons during exposure. Optical Systems up to 20 m. diameter have been designed with aperture ratio of I : 0-7. Mirror Systems have a curved ficld which just fits the curvature of the cathode surface of the intensifier tube. A new large size intensifier tube will be described with high brightness gain, good anode résolution and extremely low “dark current”. Twin lenses f 0.75 are used between anode and film.*