Images of Night Vision Devices

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Development of Night Vision Technology

About 85% of people's cognition of the surrounding things is caused by light as a medium and through vision. This shows the importance of light for people to observe, understand and analyze things. However, due to the limitations of human vision, in order to expand people's horizons, it is necessary to use some equipment. For example, a telescope is required for observing distant scenes, a microscope is required for observing subtleties, and night vision devices are required for observing dark scenes.

Light is also an electromagnetic wave, which is an electromagnetic wave with a high frequency and a small wavelength. Its wavelength is generally between 10 and 10E+6 nm (1 nm is equivalent to 10E-9 m), and visible light accounts for only a small part of it, about 390 to 776 nm. Below 390 nm is ultraviolet, and above 776 nm is infrared. The necessary condition for the human eye to directly observe the scene is that there is light, but this is not sufficient. The sufficient condition is that there must be a certain amount of ambient illumination and visible light.

How do people convert invisible light to visible light and increase low illumination? Night vision technology was created around solving these problems. Let's start with a characteristic of light. In the 19th century, Irishman Smith discovered a photoelectric effect, which made it possible to convert light and electricity into each other. In today's highly developed science and technology, it is not difficult to convert the frequency, phase, and amplify the electrical signal. As long as the different brightness of each part of target is converted into electrical signals (current and voltage) of different size, and then the light image is converted into an electrical image by scanning technology, this process is called photography. Finally, the electric image is restored to light image by the imaging technology to achieve the purpose of observation.

Why is the Image of the Night Vision Device all Green?

Green Images of Night Vision

The night vision device uses photoelectric conversion technology. It takes the intensifier as the core device and is mainly used for night detection. Under the weak light, the light reflected by the target passes through the visible light perception displayed by Zeng Photo Studio on the fluorescent screen, which can facilitate people to grasp some information. In people's lives, products such as night vision devices for cars and night vision devices for cameras are becoming more and more popular.

The green color of the night vision device is one of its highlights. This is because the night vision device contains an image intensification system, which contains an image intensifier tube that collects and amplifies infrared and visible light. In an image intensifier tube, a photocathode converts photons into electrons. On the other side of the intensifier tube, electrons hit a screen containing a phosphorescent layer. The energy of these electrons causes the phosphor screen to become excited, releasing photons that display a green image on the screen.

Image intensifier tube is the core component of night vision instrument, its function is to convert weak light into electron beam, and enhance the amplification of the phosphor after bombardment, which has strict requirements on the phosphor afterglow characteristics (to meet much longer than the picture tube). If the afterglow time is short, the image will flicker, and if the afterglow time is long, smear will appear. Therefore, only this special zinc sulfide phosphor can meet the requirements, and this zinc sulfide phosphor emits green light.

Different Color of Night Vision Imager

Therefore, this is also the main reason why night vision devices can display green images. But in addition to green imaging, night vision devices can also display white imaging as long as the phosphor used is replaced.

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