Lambert's cosine law means that when light hits the surface of an object, the brightness of the reflected light is proportional to the cosine of the incident angle, that is, the brightness of the reflected light decreases as the incident angle increases. In the low-light night vision device, Lambert's cosine law can be used to calculate the brightness of the reflected light, so as to help the night vision device better capture the weak light in the surrounding environment.

 

The low-light night vision device includes four main components: high-light objective lens, image intensifier, eyepiece, and power supply. From the perspective of optical principles, the low-light night vision device is a special telescope with an image intensifier.

 

Weak natural light radiates through the target surface, enters the night vision device, and focuses on the photocathode surface of the image intensifier (coinciding with the rear focal plane of the objective lens) under the action of the strong optical objective lens, and excites photoelectrons; Under the action of the system, it is accelerated, focused, and imaged, and bombards the fluorescent screen of the image intensifier at a very high speed, and excites enough visible light to turn a distant target illuminated by weak natural light into an object suitable for human observation. Visible light images. Through the further magnification of the eyepiece, more effective visual observation can be realized. The above process includes two conversions from optical image to electronic image and then to optical image.