The improvement of human visual performance by low-light night vision devices can be summarized as: first, prolonging the time domain and overcoming the obstacle of "night blindness"; second, increasing the airspace, so that people not only "see" farther and more clearly , and normal vision in low-light spaces (such as air-raid shelters); third, the frequency domain is expanded, and the effective spectral region is extended to the infrared frequency band. The reasons for this can be summarized as follows:

1) The pupil aperture of the objective lens of the low-light night vision device is much larger than that of the human eye, and the number of photons captured by the system increases rapidly according to the quadratic law of the ratio of the two, which effectively increases the amount of information.

2) The quantum efficiency of the cathode surface of the image intensifier is much higher than that under the dark-adapted condition of the human eye.

3) The system enhances the target image to a level suitable for human eye observation, avoiding a series of visual defects of the human eye under low light conditions (such as sharp drop in resolution, increase in contrast sensitivity threshold, and loss of some dynamic information). Wait).

4) The visual aid function of the telescope is used to increase the viewing distance and enhance the resolution.

5) With the help of the spectral response characteristics of the photocathode extending to the long wavelength band, part of the near-infrared radiation information that cannot be perceived by the naked eye is utilized.