About 85% of people's understanding of the surrounding things is based on light as a medium, which causes reactions 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, some equipment must be used. For example, a telescope is needed to observe the distant scene, a microscope is needed to observe the details, and a night vision device is used to observe the scene in the dark. Light is also an electromagnetic wave, which is an electromagnetic wave with a very high frequency and a small wavelength. Its wavelength is generally between 10 and 10E+6 nanometers (1 nanometer is equivalent to 10E-9 meters), and visible light only accounts for a small part of it, about between 3 9 0 and 7 7 6 nanometers. Ultraviolet rays below 390 nm, and infrared rays above 776 nm. The necessary condition for the human eye to directly observe the scene is the presence of light, but this is not sufficient. The sufficient condition is a certain degree of ambient illumination and visible light. How do people convert invisible light into visible light and improve low illumination? Night vision technology emerged around solving these problems. As long as the different brightness of each part of the scene is converted into electrical signals (current and voltage) of different sizes, and then the light image is converted into an electrical image through scanning technology, this process is called photography. Finally, the imaging technology is used to restore the electrical image to a light image, so as to achieve the purpose of observation.
Why are the images seen by night vision devices green? The core component of the night vision device is an electronic image intensifier tube. Its function is to convert the weak light into an electron beam, and then bombard the phosphor to emit light after strengthening and amplifying. This has strict requirements on the afterglow characteristics of the phosphor (than the picture tube much longer sessions). If the afterglow time is short, the image will flicker, and if the afterglow time is long, there will be smearing. Therefore, only the special zinc sulfide phosphor can meet the requirements, and the zinc sulfide phosphor emits green light. Not only low-light night vision devices, but early radars and oscilloscopes all use this kind of phosphor, so they also display green light.
So what is the difference between low-light night vision imaging and infrared thermal imaging? Take the infrared night vision device as an example, use infrared light to shine on the target, because infrared light is invisible light, you can not expose yourself, and then use the infrared image changer tube to convert the invisible electrical image into an optical image visible to the human eye to achieve purpose of observation. Thermal imaging uses thermal contrast between the target and the surrounding environment due to differences in temperature or emissivity. Due to the difference in thermal contrast, the infrared radiation energy density distribution map is displayed as a thermal image, and then the infrared image is changed into a visible light image through the thermal image. As mentioned earlier, the color of low-light night vision imaging is mostly green, while the color of infrared thermal imaging is generally red hot, black hot or white hot.
What is the difference between the new digital night vision imaging and the traditional low-light night vision imaging? The new digital night vision device uses a low-light image sensor, that is, a type of sensor. We are not unfamiliar with this kind of image sensor. For example, digital cameras, camera phones, and digital SLR cameras all have a sensor and a lens for digital image acquisition and imaging. The digital night vision device is different in that it uses a low-light image sensor. Generally, the imaging of digital night vision devices is black and white. Of course, the display color of the display screen can be adjusted, and it can be displayed as green, but there is still a big difference between this green and the green of low-light night vision devices.
Green, black and white, or thermal imaging, which is the best viewing effect of night vision device imaging technology? Imagine what would happen if our world had no color, only black and white? Then the picture you see will have no sense of impact, no sense of layering, and you will not feel the vitality, vitality, and shock brought by everything in the world... Different colors bring different feelings to people, low-light night vision The yellow-green imaging of the instrument gives people a comfortable and gentle feeling, so the eyes will be more comfortable when using this kind of low-light night vision device. From this point of view, the low-light night vision device with green imaging is better than the digital night vision with black and white imaging. The effect is much better. Of course, it cannot be said that digital night vision devices have no advantages at all. This type of night vision device has more advantages in terms of functions, such as day and night dual-use, high-definition photo and video recording, video output, GPS positioning, motion detection and so on. Compared with the infrared thermal imaging, the green imaging of the low-light night vision device has a better viewing effect in terms of the clarity and resolution of the overall picture viewed. The infrared thermal imaging is only more effective in finding and detecting targets. Advantages, in terms of target recognition, the effect of low-light night vision devices is more widely used. There are certain reasons why low-light night vision devices have existed since their appearance and have not been replaced by any products.