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The human vision is seriously degraded under a low light level environment. It is a general experience that as the light level going down, the resolution of human eyes is reduced as well. Therefore, while in a low-light level environment, increasing the target contrast will keep and the observer's viewing purposes in a better perceptible condition.
Night vision goggles is a kind of device that makes the night visibility to a great extent. With which, one of its major elements -- the image intensifier tube, may gain the light of the vague image under the feeble light.
A series of studies in this field mainly probe into the low light level environment and the items of enhancing the night visibility. Meanwhile. the study also proceeds with the analysis and the measurement of the night vision goggles, which is made of the Generation II image intensifier tube. In addition, it is revealed from the result of the measurement that as the light level arises, the resolution will increase accordingly; furthermore, the curve will initially show a steep status as the light level increases, then, the curve will turn to be a saturate status as the light level continuously increases. Apparently, this phenomenon explains that to what extent the light reflecting from the target will influence the resolution. Accordingly, under the low light level environment, the experimental data ofthe resolution measurement may offer a proper basis for specifying the types of the night vision system.
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