Until the middle of the 20th century, only certain birds and animals had the privilege of recognizing objects and seeing in pitch darkness. However, with the development of military technology, the man finally got such an opportunity. Even before World War II, German manufacturers were developing the first-night vision devices that worked through active illumination in the infrared range and image amplification with an image intensifier tube with a photocathode. Prototypes were used in tank troops and made it possible to move equipment at night without fear of the enemy safely. And today, night vision devices (NVD) have received civilian use. They are used in rescue work, aviation, navigation, and even unnecessary travel. As for non-professional use, experienced hunters often use night vision devices. In addition, even though even a modern device of the latest generations remains relatively expensive, there are plenty of affordable models on the market that can allow everyone to participate in the nightlife of wildlife actively.
Night Vision Applications
Photography and videography in low light are art in their own right. While there are many camera apps for the iPhone, most of them only work with optimal lighting. For this reason, there are dedicated night vision applications that can illuminate dark environments to provide better visibility. Although there are few options, technology does not stand still. Application developers can now offer more than 20 options for high-quality night vision applications for iPhone, iPad, and Android phones.
Types of Night Vision Devices
Night vision devices are electro-optical devices based on an infrared electron-optical converter, which is placed in a protective case and equipped with a specific mounting system. In addition, many night vision devices are equipped with infrared illumination and telescopic lenses. They can be produced in monoculars, thermal cameras, glasses, telescopes, and night-vision binoculars. The principle of operation of night vision devices is significantly different. Conventional night vision goggles and binoculars differ from night vision goggles because they are optical devices that allow you to see in low light levels. They only amplify the existing light and form an image only by optical means - due to a lens with large diameter lenses. In addition to night vision binoculars, night vision telescopes and glasses work on the same principle. Astronomical binoculars are also produced - huge binoculars with a lens with lenses of huge diameter. Previously, night vision devices were used primarily by military and law enforcement agencies, but now ordinary citizens are increasingly using them. In the civilian field, they have found applications in night videography and photography, nighttime wildlife surveillance, maritime navigation, and various security-related applications. Recently, compact night vision video recorders have been installed on cars. Various types of night vision devices are produced and freely sold, the designs optimized by their purpose. The main types of NVDs include:
• Observation devices (monoculars, pseudobinoculars, binoculars);
• scopes for small arms;
•·glasses;
• devices that document the observed image (night photos and video cameras).
Consider each of the types of devices separately. Monoculars. Night monoculars (finders) have one input lens, one image intensifier tube, and one eyepiece (magnifier). Observation through such a night vision device is carried out with one eye, and the device is held with one hand. The most common in domestic sales are monoculars based on image intensifier tubes of the zero generation. Two 1.5-volt batteries usually power the power supply. The mass is about one kilogram. The main parameter of both observational and all-night vision devices is the range of vision. Its competent definition should include the following factors: the illumination of the observed scene, the size of the experimental target and its contrast with the background, and the detail of vision: detection, recognition, and identification. Such a multifactorial nature of determining the range of vision often leads to a discrepancy between this parameter's advertising and actual values.
In some cases, the buyer is offered to check the operation of night vision devices with a protective cover on the lens with a “pin” hole that simulates night illumination. Such a test gives an idea of the image quality (clarity and clarity of the field of view) but cannot be used to assess the range of vision, as it sharply changes the parameters of the input lens. From experience and elementary calculations, it follows that observational night vision devices based on a zero-generation image intensifier tube and input optics with the above parameters provide, at an illumination of 0.01 lux (description created at night by a quarter of the moon), the detection of a human growth figure against the background of greenery from 150-200 m and its recognition details from about 70-100 m. Some night vision devices of this type are equipped with small-sized infrared illuminators (radiation maximum is about 0.8 microns), with a power of several tens of milliwatts/steradians. The effective range of such illuminators is about 50 m; NVD with such an illuminator makes it possible to work in complete darkness (caves, basements) but unmasks the observer for similar or better night vision devices. Night vision devices using second-generation image intensifiers have great potential. NVD with second-generation image intensifier tubes has good noise immunity: bright flares falling into the field of view of such night vision devices are local in the output image: they do not create halos. They do not interfere with observation over the entire field of view. The mass of such night vision devices, mainly due to the large size and mass of the second-generation image intensifier tube, is at least 1.5-2 kg. The price is from one to several thousand dollars, depending on the quality of the image intensifier tube and optical components, as well as the power supply circuit, including automatic output brightness control.
Binoculars. In a typical visual process, a person uses two eyes. The images created by each eye, complementing and reinforcing each other, create in our minds one visual image that also carries information about the spatial nature of the image (stereoscopic effect). Pseudo-binocular night vision devices use one lens, one image intensifier tube, and a binocular panoramic eyepiece at the exit. Such an eyepiece faces the observer with the convex side of a flat lens, with a field of view angle of 90 degrees or more, through which the image on the image intensifier screen is viewed with two eyes. This provides greater ease of observation and, accordingly, less eye fatigue. Night binoculars of the classical design contain two lenses, two image intensifier tubes, and two eyepieces. Unlike pseudobinoculars, such a scheme provides a stereoscopic image of distant objects. The distance between the input lenses is much larger than between the eyes (base). When observing, night binoculars, like ordinary ones, are held with two hands using particular structural elements: handles, holders, and tides. Depending on the quality of the optical components and the type of image intensifiers used (zero, first, or second generation), the price of pseudo and binocular night vision devices ranges from 800 to 2500 dollars.
Scopes. In certain circumstances, it is necessary to observe the object at night and aim at it in such conditions (for example, night hunting). Night scopes solve this problem. Fundamentally, the night scope is similar to the night monocular but has the following significant differences. The area has a mechanism for attaching to a weapon and a “reconciliation” mechanism. The latter ensures the alignment of the aiming (shooting) line of the gun with a unique mark ("mark") in the NVD field of view, which plays the role of a "fly" during night shooting. The effect can be dark or luminous, preferable since a brilliant mark is more easily distinguished on an opaque object (target). Due to the enormous shock loads that occur at the time of the shot, the sight and the entire structure of the device are subject to increased requirements for impact resistance and shock resistance compared to other NVD. The range of action of night scopes is reasonable to correlate with the content of aimed fire of weapons, which is 200-400 meters for light small arms. Night scopes can also be used in the daytime, for which a unique diaphragm (cover) with a “pin” hole is put on the lens, which protects the image intensifier tube from bright light and, at the same time, provides good visibility of the target.
Night vision goggles. The principal difference between night vision goggles (NVGs) and the above-described NVDs is that NVGs are fixed on the head or a special headgear of the observer, leaving his hands free to perform various work and operations at night. The latter's scope is wide and varied: repair and rescue work, driving ground and air transport shooting at targets illuminated by laser emitters. Almost all NVDs have a single magnification and a wide field of view for familiar and quick orientation: 40 degrees or more. The classical design of the NVD contains two lenses, two image intensifier tubes, and two eyepieces in several NVDs; to reduce the price, one objective and one image intensifier tube (the so-called "cyclops" type) are used. The most accessible and cheapest are the NVDs based on image intensifier tubes of zero and first generations. The most effective in terms of range and lightest (less than 500 g) are those based on image intensifier tubes of 2+ and 3rd generations. Due to the high price of such glasses, comparable to the cost of an average car, they are used mainly for night piloting helicopters or for tasks performed by special services. The latest development in the field of NVDs is holographic NVDs.
Due to the use of holographic mirrors and filters in such glasses, the enhanced image intensifier tube of dimly lit objects was transmitted almost entirely 08 percent, while at the same time reflecting light interference that interferes with observation, which is visible as if through very dark glasses, by the same amount. The lower part of the mask of such glasses has increased transparency, which makes it convenient to observe the dashboard when using glasses for driving vehicles at night.
Night vision device with image documentation. In some cases, documentation (photography, video recording) of scenes, objects, and their actions observed with the help of night vision devices is required. The simplest solution is to join the night vision device instead of the eyepiece of a photo or movie camera. Some night vision devices are equipped with adapters for attaching cameras, which the device user easily carries out. More advanced and multifunctional is the system in which the image from the screen of the NVD image intensifier tube is optically transmitted to the CCD matrix (abbreviated from "charge-coupled device - a specialized analog integrated circuit consisting of light-sensitive photodiodes, made based on silicon, using technology CCD - charge-coupled devices. Transmission is carried out using focus (fiber-optic "image reducers") or "transfer" lens optics. The CCD matrix's electronic circuit ("framing") converts the received image into a video signal in analog and, if necessary, in digital form. The video signal can be observed on a TV screen (monitor), which is more convenient and less tiring than observation (especially long-term) through the NVD eyepiece. At the same time, simultaneous recording on a VCR and transmission to several monitors for several operators is possible. The video signal can be transmitted over cable (up to 200 m without intermediate amplifiers) or o using a miniature transmitter built into the surveillance device, the call of which is received on one of the channels of a conventional TV. The quality of such systems is determined by the number of television lines transmitted under a particular illumination of the observed scene. Such devices can be equipped with adapters for connecting to the NVD input modern lenses for CCD cameras with remotely adjustable aperture (auto-iris - aperture adjustment function in automatic mode), variable magnification (zoom - a derived value showing the ratio of the maximum and minimum focal length) and sub focus. A device with such a lens and an image intensifier tube with a good AGC scheme provides almost round-the-clock (from a moonless night to a bright day) observation with the necessary documentation.
Thus, modern photo electronics significantly expands the possibilities of human vision in terms of vision in low light conditions and ranges that are fundamentally inaccessible to the eye. The complexity of this technique, the large number of types of night vision devices available for sale, the difference in their classes and prices, as well as the inevitable advertising "overexposure" in the descriptions of devices make it highly desirable to have qualified and objective advice when choosing and purchasing such machines.