1,Basic concepts and classification of night vision devices
The so-called night vision technology is a photoelectric technology that uses photoelectric imaging devices to achieve observation under low-light conditions, and night vision equipment is an instrument that uses photoelectric conversion equipment to convert infrared rays into visible light. Night vision devices can be divided into two categories: active and passive. Active infrared night vision devices are low in cost, clear in imaging and good in contrast, and are less affected by ambient lighting conditions during use. In military affairs, it has the disadvantage of being easily detected by enemy detection equipment. The passive night vision device uses the radiation emitted by the target itself, and uses the infrared detector to take the thermal image of the target, also called a thermal imager. Compared with active infrared night vision devices, low-light night vision devices are small in size and light in weight, and because the working method is passive, the safety is greatly improved and it is not easy to be exposed, but the disadvantages of low-light night vision devices are also obvious , its operating distance and observation effect are greatly affected by environmental conditions. It cannot work normally in rainy and foggy days, and it will completely fail in a completely dark environment.
2,The imaging principle of night vision device
1.The objective lens focuses and collects the infrared light emitted by all objects within the line of sight.
2.The collected light is sent to an image intensifier tube. In most night vision goggles, the image intensifier tube is powered by two or more batteries.
3.The photons in the light energy are converted into electrons by the image intensifier tube.
4.At the end of the image intensifier tube, electrons strike a screen with a phosphorous coating, creating an image. The phosphorous coating creates a green icon on the screen that reflects the night vision feature.
5.The green phosphor image is viewed through another lens eyepiece, which magnifies and focuses the image.
3, The use of night vision devices
It is suitable for night patrol detection and evidence collection of the army, customs, border defense, and public security guards. Banks, treasuries, cultural relics, and important material warehouses for night monitoring. Night exploration of seabed resources, monitoring of underwater parts of offshore oil platforms, and deep-sea fishing. Satellite remote sensing telemetry, night observation of weak stars in astronomical galaxies. Record the research on the growth law of plants at night, and the research on the living habits of nocturnal animals.
4. Frequently asked questions about choosing night vision devices
Will the eyes feel uncomfortable after using the night vision device for a long time?
The night vision device is an image brightening device, so once the design is not good, it will cause very uncomfortable eyes. Some brands have no investment cost in the design, and blindly increase the image contrast, which will lead to many low-end night vision devices. There will be tears.
What are the differences between different generations of night vision devices?
The main difference is the advancement of booster technology. The first generation uses an intensifier tube to enhance the brightness of the surrounding environment, thereby accelerating the flow of electrons hitting the phosphor surface, and the second and third generations improve the intensifier to increase the number of electrons hitting the phosphor surface, thereby enhancing the brightness. Due to the backward technology of the first-generation night vision device, it is necessary to use infrared auxiliary light source to find the target, and the distance of infrared auxiliary light source is generally only 50 meters, and the infrared auxiliary light source will appear red burst, which is easy to be found. Therefore, in theory, the second-generation night vision device should be selected, and its observation distance can reach 200 meters.
What is the optimal range of the night vision device?
Depending on the use environment, such as cloudy or rainy days, the range of the night vision device will be shortened. In addition, even for the same generation of night vision devices, the quality of the image tube, internal optics, and data processing are closely related.
5、 Important parameters of night vision device
Image tube level: There are currently two mainstream types, one is 2nd generation +, and the other is 3rd generation. The English display is 2+ and 3, or Gen2+ and Gen3. Of course, there are 4th-generation image tubes. The first generation of image tube night vision devices are gradually withdrawing from the market.
Resolution: Resolution is basically a parameter standard for judging the quality of night vision devices of the same level. There is a premise here that they are of the same level. The unit of the parameter that expresses the resolution of the night vision device is lp/mm, which means line pair/mm. The higher the parameter, the higher the resolution of the night vision device.
Sensitivity: Sensitivity is also the most important indicator to describe the brightness of the night vision device. The higher the sensitivity, the higher the magnification rate of the night vision device for low-light light. Or simply put, the higher the sensitivity, the stronger the brightness of the night vision device, so in low light, the brightness and contrast of the image are also higher. So the sensitivity reflects the night vision ability of the night vision device.
Magnification: magnification, using a numerical value to represent the relationship between the actual size of the object and its enlarged size. Observing an object at 700 meters through a telescope with a magnification of 7 times is the same size as the object seen with the naked eye at 100 meters. The magnification of the night vision device when seeing the target, the general magnification is 1X, 3X, 5X, 6X, 7X, etc. At present, most of the individual night vision devices are 1 times and most of them are head-mounted, because the images that are more conducive to viewing are true and reliable. Just imagine if you wear a 5x magnification night vision goggle on your head, it is impossible to judge the real distance between the target and yourself. High-power night vision devices are generally used handheld.