There are two kinds of night vision goggles, one is low-light night vision goggles and the other is infrared night vision goggles.
Low-light night vision device amplifies weak light, and infrared night vision device converts infrared light into visible light.
There are two kinds of infrared night vision goggles, one is active and the other is passive. The initiative is that the night vision goggles emit a beam of infrared light, which shines on the object and then reflects back, which is equivalent to a flashlight; Passivity is to amplify the infrared rays emitted by the object itself into visible light.
Therefore, in the absence of light at all, low-light night vision goggles can't see anything. Without infrared source (most things that can generate heat can become infrared source, such as creatures, vehicles, flames, etc. ), passive infrared night vision goggles can't see anything.
Active infrared night vision goggles can see things under any circumstances. Different night-vision goggles have different applications, and low-light-level night-vision goggles are suitable for use in the field with starlight or moonlight.
Because night vision goggles only display monochrome, and its display screen is green (you can notice that the display screens of many instruments are green), what you see is green.
Night vision technology is a photoelectric technology that realizes night observation with the help of photoelectric imaging devices. Night vision technology includes low light level night vision and infrared night vision. Low-light-level night vision technology, also known as image intensifier technology, is a photoelectric imaging technology that uses image intensifier tube to enhance the weak target image irradiated by nightglow, and observes it through night vision goggles. Low-light-level night vision equipment is the most abundant and widely used night vision equipment abroad at present, which can be divided into direct observation (such as night vision equipment, weapon sight, night pilot and night vision glasses) and indirect observation (such as low-light-level TV). Infrared night vision technology is divided into active infrared night vision technology and passive infrared night vision technology. Active infrared night vision technology is a kind of night vision technology which observes by active illumination and using infrared light reflected by targets in infrared light source, and the corresponding equipment is active infrared night vision device. Passive infrared night vision technology is an infrared technology that realizes observation by means of infrared radiation emitted by the target itself. It finds the target according to the temperature difference or thermal radiation difference between the target and the background or target part. It is equipped with a thermal imager. Thermal imager has unique advantages different from other night vision equipment, such as working in foggy days, rainy and snowy days, working at a long distance, recognizing camouflage and anti-interference. It has become the development focus of foreign night vision equipment, and will replace low-light-level night vision equipment to some extent.
1, low light level night vision technology
At present, low-light-level night vision equipment is widely equipped abroad. It can be divided into enhanced low-light-level night vision technology (direct observation) and low-light-level television (indirect observation).
(1) image enhancement technology
Image-enhanced low-light-level night vision technology is a photoelectric imaging technology. Through night vision goggles with intensifier tubes, the weak target image irradiated by nightglow is enhanced for observation. Its working principle is: firstly, photoelectric conversion will be carried out, then the electrical signal will be amplified by MCP, and finally photoelectric conversion will be carried out.
In 1950s and 1960s, this technology developed rapidly due to the birth of multi-alkali photocathodes, optical fiber panels, microchannel plates (MCP) and negative electron affinity (NEA) photocathodes. Because it overcomes the fatal weakness of active infrared night vision, it has become the development focus of night vision field as soon as it appears. It gradually replaced the earlier active infrared night vision technology and occupied a dominant position. Up to now&; So far, it has developed to the third generation. The first generation of products began to be developed in the early 1960s. It adopts cascade image intensifier, which is coupled with photocathode and optical fiber panel. 1966 was used by the us military to invade the battlefield, and the equipment was mass-produced in 70 years. The second generation &; The product was developed in the early 1970s, using multi-alkali photocathode and image intensifier tube with MCP. At present, the United States, Britain, France, Germany, the Netherlands, Israel and other advanced countries can produce the second generation products. Since 1980s, these countries have basically replaced the first generation products with the second generation products. In the early 1970s, we began to study the third generation products, and in the late 1980s, the US military began to equip them. At present, the third generation products developed by the United States are only sold to NATO, South Korea, Japan, Israel and Australia.
At present, the main low-light-level night vision equipment that the US military has equipped and will equip is as follows:
Aviation application
AN/AVS-6 night vision goggles for pilots were developed by Bell Ha Weier Company, with a field of vision of 40o. The U.S. Army has successively adopted the acquisition plan of "Aumigny, Bath" (Omnibus Ⅰ, Omnibus Ⅱ, Omnibus Ⅲ, Omnibus Ⅳ), and conducted four acquisitions, each of which improved its performance. At present, a large number of army aviation units are equipped with fixed-wing aircraft or helicopters. Among them, ITT signed a contract with Omnibus IV to provide improved AN/AVS-6. The core component of the improved AN/AVS-6 is MX- 10 160 image intensifier developed by ITT Company. This third-generation image intensifier uses the latest gallium arsenide technology and works in the near infrared region, replacing the early image intensifiers.
ITT also develops and produces AN/AVS-9 night vision goggles (formerly F4949), which are installed on the helmets of fixed-wing aircraft pilots.
AN/AVS-7 night vision flight image system/head-up display (ANVIS/HUD) jointly provided by the United States and Israel is an improved version of AN/AVS-6. The system is installed on both sides of the pilot's goggles to obtain key flight information and transmit it to the goggles. After being superimposed with the goggles, the pilot can see the comprehensive night scene and the symbol system of key flight information. With this device, the time for the pilot to look down at the instrument is greatly reduced, while the time for looking up at the windshield is greatly increased. The US Army originally planned to deploy 1.904 sets of such systems, and so far, it has obtained about 1.800 sets of such systems. At present, the system is being further improved to be compatible with the improved global positioning system (GPS) used on the platforms of UH-60A/L and CH-47D. It is planned to further upgrade 65,438+0,200 such systems to "Advanced Head-up Display" in September this year, so as to obtain field programmable capability, video recording capability and faster response speed. The system is also used in the United States Marine Corps.
Ground force application
The new generation of night vision equipment used by the ground forces of the US Army is mainly monocular glasses, such as AN/PVS-7D provided by ITT Company and the most advanced AN/PVS- 14 at present. AN/PVS- 14 combines the advantages of the third generation \ "Super \" MX-1KLOC-0/60 passive image intensifier and aviation night vision goggles AN/AVS-6, which is helpful to improve observation, command and control capabilities. Better than AN/PVS-6. AN/PVS-7D is 1. 15) and lighter (0.4 kg, while AN/PVS-7D is 0.68 kg). Therefore, the commander of the infantry fighting team wears it on his head more flexibly, and the observation distance is greatly increased. 1996, ITT and Litton signed the Omnibus (Omni) ⅴ * * contract with the Night Vision and Electronic Sensor Committee (NVESD) under the Research, Development and Engineering Center of the US Army Communications-Electronics Command to produce AN/PVS- 14 device. Up to now, about 3000 AN/PVS- 14 devices have been deployed. It is estimated that ITT will deliver 30,000 such devices to the US Army by the year 2000. Omnibus ⅴ also continues to produce advanced AN/PVS-7D monocular night vision goggles and advanced I2 improved AN/AVS-6 pilot goggles, which are recommended by Litton Company for ground combat applications. These tasks are expected to be completed before March 3 1. According to the CEO of Litton, the project has extended the life of thousands of field systems and greatly improved the performance of night vision systems through appropriate improvements.
The third generation image intensifier is also a necessary part of AN/PVS- 10 sniper night vision and improved day and night fire control and observation device. The Army Special Operations Command is responsible for the purchase of extra barrels, so as to provide the special forces with instant visible images of extra barrels (I2), which can be used for aiming at medium and heavy sniper rifles and strategic reconnaissance.
The third generation image intensifier (I2) tube is also used to improve the active system of Chai H. For example, the AN/PVS-4 weapon sight used in1970s was improved to the current AN/PVS-4A. So far, more than 65,438+0,000 weapon sights have been improved, and it is planned to finally improve more than 5,000 weapon sights.
Some American combat troops carrying out global combat missions will soon equip their M- 16 series rifles with "TLOS". The system is equipped with the third generation gated image intensifier, two field objectives and a laser illuminator. The system uses near-infrared low-energy laser to directly obtain the photoelectric information of the target. The device does not have the ability of laser countermeasure, but can obtain passive target information, provide hidden lighting at night and direct shooting aiming.
The night vision of the new G22 sniper rifle provided by British Precision Instruments Company to the German Bundeswehr uses the second generation semi-image intensifier tube (model NSV80II), which can clearly find the target in the dark night. The sight is installed on the special Weaver guide rail in front of the standard optical sight. The shooter can determine the distance between the eyes and the sight at will, adjust the division at will, and shoot again after a few seconds without changing the position of the aiming point.
Technical difficulties and methods
At present, foreign night vision devices have two technical limitations: (1) When strong light shines on this night vision device, it will lose the dim light image in the distance or nearby; (2) The plane imaging plane (that is, the plane microchannel plate located on the focal plane) is used for the intensifier tube, which will cause light distortion, so that the field of view of the night vision device currently used in the army is at most 400×400, which is difficult for human eyes to adapt.
Los Alamos Laboratory in the United States is using the following methods to solve the above problems: (1) The microchannel plate (MCP) is divided into different electronic regions (5% of MCP), and each electronic region uses its own automatic gain control (AGC) circuit. The strong light only passes through part of the electronic region and its AGC, so that the night vision device can still see the objects in the blurred background behind the strong light when it is irradiated by strong light. Micro-channel segmentation can be accomplished by laser grinding or "selected area" deposition (such as lithography). (2) The planar microchannel plate is replaced by an arc microchannel plate. This kind of curved microchannel plate is currently used in the X-ray telescope of Alexis spacecraft, so the night vision device developed in this way will provide at least 600×600 for each eye. When cascaded, it can provide 900× 600 (horizontal) field of view, which is more than three times of the current level. At the same time,
(2) Low light TV
Low-light-level TV is a low-light-level night vision system composed of an amplifier tube and a TV camera tube. It was born in 1940s and developed rapidly in 1970s. It has the advantages of large imaging area, intuition, continuity and long-distance multi-point and multi-person observation. Widely used in surveillance, reconnaissance, detection, guidance and tracking, more than 30 kinds have been equipped abroad. Typical products are "Carnarst" low-light-level television system for tanks in France, UVR-700 direct plane day and night dual-purpose television tracking system in the United States, V0084 low-light-level television system for navy in Britain, and 2704 long-distance (observation distance is 10 km) low-light-level television camera in Switzerland.
At present, the low-light-level night vision device can only provide monochrome images, and the use of color images will help target recognition, which will increase the recognition speed by 30% and reduce the recognition error by 60%. Therefore, color low-light-level night vision technology has attracted much attention.
American Delft Sensor System Company uses two image intensifiers with different spectral responses to observe the same scene, and uses the differences between them to produce color images through filtering and special electronic processing technology.
MIT Lincoln Lab combines low-light-level images with infrared thermal imaging to produce color images. The small color night vision system designed by Lincoln Laboratory uses charge coupled device (CCD) coupled with the third generation image intensifier to obtain the low light level image, uses uncooled imaging array to obtain the infrared thermal image, and then uses dichroic beam splitter matching and image processor to process it, and displays the vivid color image on the LCD.
American Wood Monitoring Technology Company has developed a full-color night vision camera. The camera has an addition CCD chip for each primary color, and adopts video addition technology to obtain color images similar to broadcast cameras.
The color night vision system being developed by Kazan Optical Machinery Factory in Russia can convert the received color images with different infrared frequencies, and it is estimated that it can be put into the market in a few years.
2. Infrared night vision imaging technology
Infrared night vision technology has experienced early active infrared night vision imaging technology and now passive infrared (thermal imaging) technology. Infrared detector was first used as a unit detector, and then developed into a multi-element array detector in order to improve sensitivity and resolution, and now it is developed into a multi-element area array infrared detector. The corresponding system realizes the leap from point detection to target thermal imaging.
(1) active infrared image conversion technology (near infrared region).
This technology uses the principle of photoelectric image conversion to realize night observation. This instrument includes infrared light source and night vision goggles with image converter. Infrared light source illuminates the target, and night vision goggles convert invisible infrared images into visible images. This technology began to be studied in the late 1930s, and was developed and applied in World War II. Rifle sights equipped with active infrared night vision devices are widely used in the Pacific battlefield. Around the 1960s, this technology became mature, and the observation distance could reach 3,000 meters. Later, the troops were widely equipped. However, due to its fatal weaknesses such as low sensitivity, high calorific value, high power consumption, large size, limited observation distance and easy exposure, it was gradually replaced by night vision technology developed later, and now only a few countries have a small amount of equipment.
(2) Passive infrared night vision technology (middle and far infrared region)
Infrared thermal imager is one of the most promising infrared detectors, which represents the development direction of night vision equipment. It uses a semiconductor device with photoelectric effect as a detector to convert the radiation image of the scene into a charge image, which is converted into a visible light image by a display device after information processing. Some typical models include:
The ANS/PAS- 13 thermal weapon sight (TWS) developed by Raytheon Systems for the US Army is the most advanced passive infrared night vision equipment, and it is a thermal imaging sight system using the second generation forward-looking infrared technology. The technologies used in the system include: high-sensitivity cadmium telluride focal plane technology for long-distance target acquisition by small telescope; Light weight and high transmission rate binary optical component with advanced plastic shell; Small-sized, low-power VLSI electronic components: thermoelectric refrigerator with quiet operation, high reliability and thumb size; Low brightness LED display screen; suit
1. Win effective midnight fighting time.
Night and bad weather account for a considerable proportion of the whole year. Night vision equipment makes the night transparent and greatly prolongs the effective combat time. Infrared night vision equipment has high resolution and has the advantage of detecting sea-skimming flying targets. The infrared thermal imager for ship-borne tracking can not only provide target data for launching missiles, but also detect enemy sea-skimming missiles. The photoelectric fire control system equipped with thermal imaging equipment is convenient to identify targets and shorten the reaction time of weapon system.
2. Established the military status of midnight oil.
With a large number of night vision equipment in the three armed forces, western developed countries have taken leading night operations as their winning strategy.
3. The effectiveness of multiplier weapons
The combination of night vision technology and weapons and equipment will greatly improve the effectiveness of weapons and equipment in obtaining information, carrying out strikes, commanding troops, mobile troops and coordinated operations at night and in bad weather.
4. Reduce flight accidents
Using the navigation hangar with forward-looking infrared camera and letting pilots wear goggles with night vision goggles can greatly reduce aviation accidents.