The low-light image is derived from the reflection of natural radiation illumination at night by the target and its surrounding background. The low-light imaging sensor is only sensitive to the reflection of the target scene, and has nothing to do with the thermal contrast of the target scene, so the low-light image has high definition and spatial resolution, which can provide detailed information about the geometry and texture of the scene, which is beneficial to the observer. Form an overall perception of the scene.

Therefore, low-light images have the advantages of conforming to the observation habits of the human eye, high detail resolution, and better ability to describe the details of objects.

 

On the other hand, the natural radiation at night, the radiation of the target and the background itself, and the reflected spectrum are relatively strong in the red and near-infrared regions. Green vegetation and vegetation also have strong reflections in this spectral range. The radiant energy is relatively low, and the reflection of green grass and vegetation is relatively weak. In this spectral range, it is almost impossible to distinguish vegetation and the night sky according to the reflection characteristics of objects. At the same time, because the electrical signal output by the photocathode is the result of the photocathode integral imaging of the scene in the entire spectral range to which the cathode is sensitive, therefore, for scenes with different reflection spectral distributions under night conditions, the integral imaging may have the same or similar imaging results. The signal value is the brightness value, so the contrast of the output image is small and difficult for the human eye to distinguish.

In addition, due to the effect of the image intensifier, low-light images have the following disadvantages:

1) The inconsistency of channel gain will produce serious particle noise, which becomes more and more obvious as the gain increases.

2) Charge combined element (CCD) transmission loss noise, output amplifier noise and interface state noise, etc., but they have little effect on the output image.

3) The generation of low-light images is greatly affected by the external environment, and it can not even work under all black and very bad conditions.