There are two types of cells in the retina, cone cells and cylindrical cells, which are responsible for seeing in bright conditions and in dark conditions (I can't remember exactly which cells are responsible for bright vision and which are responsible for dark vision). After the environment becomes dark, the inhibition of the cells that control dark vision is eliminated, and gradually restored to the level that can function better, then the human eye can see the surrounding things clearly.
It is said that shortly after the liberation of the country, pilots sometimes needed to take off at night, but could not see the instruments in the cabin, and it took fifteen minutes to half an hour to get used to it, which seriously delayed the war planes. The highest decision-making departments are very anxious, looking for a lot of industry experts to solve the problem, and finally adopted the "pilots in the duty room to wear red glasses, or simply blindfolded" approach, once the order that under the darkness of the cover, immediately into the state, and ultimately overcome the "darkness of the adaptive "The first time I saw this, I was able to get a good look at it.