Portable test apparatus for low light level devices

Abstract

The disclosure relates to an apparatus for measuring the light intensity gain performance of an image intensifier. The apparatus includes a light source which illuminates the input surface of the intensifier with input light of predetermined and constant intensity, a light sensitive detector arranged at the intensifier output for receiving at least a portion of the output light produced by the intensifier in response to the input light and for providing an electrical signal having an amplitude directly related to the intensity of the output light and an indicator coupled to the detector for providing an indication of the intensifier light intensity gain performance responsive to the electrical signal provided by the detector. Also disclosed is a modification wherein a second light sensitive detector is positioned relative to the light source for receiving a portion of the input light and for providing a reference signal responsive thereto and a difference amplifier which determines the difference between the amplitudes of the electrical signal provided by the detector at the intensifier output and the reference signal provided by the detector at the intensifier input. The difference signal thereby produced is coupled to an indicator which provides an indication of the intensity gain performance of the intensifier which is directly related to the amplitude of the difference signal.