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Considerations For The Design And Evaluation Of Objective Lenses For Low Light Level Applications

The observation of objects under low illumination conditions is made possible using photo-electronic image intensification of the available light. The intensifier is normally used in conjunction with a large aperture objective lens so as to gather the maximum number of photons. These photons are then imaged onto the photocathode and after electronic amplification the reconstituted optical image can be viewed at the phosphor by means of an eyepiece. At present the limitation of passive night vision devices is the inadequate spatial frequency response of the image intensifier.