What is the brightness gain of the image intensifier?

Do you understand the concept of brightness gain in image intensifier?

A brief introduction to the brightness gain: The main purpose of the image intensifier tube is to improve the brightness of the image and facilitate camera photography. The ratio of the brightness of the output screen to the brightness of the input screen image is defined as the brightness gain of the image intensifier tube.

The brightness gain is related to the following two factors:
(1) Reduce the gain: the input screen area of the enhanced tube is large, and the output screen area is small. The electrons emitted from the photocathode on the input screen are concentrated and projected to the smaller area through the electronic lens.
On the screen, the number of electrons received per unit area of the output screen is greatly increased, resulting in an increase in the brightness of the output screen, which is a reduction in gain.
(2) Flow gain: refers to the high energy of photoelectrons obtained by the acceleration of the anode potential in the enhancement tube. When it hits the phosphor layer of the output screen, it can excite multiple photons.
The greater the photoelectron energy, the more photons are excited and the stronger the fluorescence. This gain is called the flow gain.