Abstract: A method for providing user adjustable variable gain for a night vision device which utilizes an image intensifier tube, wherein the image intensifier tube has a given life expectancy, the image intensifier tube is subjected to factory calibration for providing an optimum output during operation, wherein the calibration undesirably differs from tube to tube and is adjustable by variable control means coupled to the tube, whereby when one tube is substituted for another the difference in calibration causes non-optimum performance, the method including the steps of: determining minimum and maximum gain limits associated with the optimum output of the night vision device; factory calibrating gain limiting means according to the determined minimum and maximum gain limits, wherein the gain limiting means are associated with the image intensifier tube and for limiting the variable control means; and, tethering the gain limiting means to the image intensifier tube.

Abstract: A device for intensifying light images which includes an image intensifier tube assembly that is retrofittable to two different existing housings. There is a first electrical contact for electrically connecting to electrical supply contacts when positioned in the first different housing and a second electrical contact for electrically connecting to electrical supply contacts when positioned in the second different housing. The tube assembly has first spacer for effecting a predetermined spacing between the tube assembly and the first housing when positioned in the first housing, and a second spacer for effecting a predetermined spacing between the tube assembly and the second housing when positioned therein. The first spacer is inactive to control spacing when in the second housing and the second spacer is inactive for controlling spacing when in the first housing.