Day/night observation technology”.

Technology of day/night observation devices..

TECHNOLOGY OF DAY/NIGHT OBSERVATION DEVICES”  

To conduct special operations, devices are required to ensure round-the-clock surveillance. The issues of constructing day/night sights have already been considered in [1]. Here are presented more general principles of creation and specific technical solutions of day/night observation devices. These devices can be head-mounted, wearable, portable and transportable.

Night vision goggles are used as day/night head devices, providing round-the-clock observation. They have a magnification of 1x. When observing at night, the operator sees an image of the scene in the night channel, which contains an electron-optical converter (EOC). At the same time, using either a prism ocular system, as in the Nights Cat [2] or AN/AVS-502 night vision goggles, or holographic mirrors, as in the HNV-1 or HNV-3D [2] goggles, the operator can directly observe the image of the scene, bypassing the night channel. This is how “through vision” is achieved. When the level of external illumination increases sharply or when exposed to intense light interference (flashes of gunfire, explosions, fire flames, headlights, etc.), the night channel is switched off, and the operator directly observes the scene with “through vision”.

Single observation is convenient when driving a vehicle. However, for reconnaissance, it is advisable for the day channel to have a magnification of at least 5 — 7x. In this regard, Thomson-TRT (a division of Thomson-CSF) has developed pseudo-binocular day-night goggles NUIT-UGO [3] (Photo 1, Fig. 1). The main parameters of the device are given in Table 1. The resolving power of the night channel with a field of view angle of 400, magnification of 1x is 1.5 mrad/line/mm. When a telescopic attachment with a magnification of 3x is installed on the lens of the device, the night channel acquires the same magnification, a field of view angle of 130, a resolving power of 0.6 mrad/line/mm [3].

a) device; b) telescopic attachment
Photo 1. Day-night goggles NUIT-OGO:

Fig. 1. Optical diagram of day-night goggles NUIT-OGO, where 1 is the objective of the night channel, 2 is the image intensifier, 3 is the ocular system, 4 is the objective of the day channel, 5 is the inverting prism system of the day channel, 6 is the dichroic mirror

Table 1. Main parameters of day/night devices (according to company brochures)

Note.
1. D – human (h), tank (t) recognition range, m;
2. E – natural night illumination, lx;
3. 2w – field of view angle, deg;
4. G – magnification, times;
5. Diopter. – diopter adjustment limits, diopter;
6. U – supply voltage, V;
7. p – passive mode, a – active mode, ai active-pulse mode

The most widely used day/night technology is in head-up displays (HUD), helmet mounted displays (HMD), and helmet mounted sights (HMS). Such head-mounted devices have become widespread in aviation for equipping helicopter and airplane pilots, as well as for equipping special forces fighters – “soldiers of the 21st century”.

Photo 4. Night Viper device

Photo 5. EF 2000 device

Photo 6. AH-1Z HMD

Honeywell (USA) [11] has developed an integrated IHADSS device that provides round-the-clock operation and is available in two versions: for piloting a helicopter by the first pilot and for firing the helicopter's weapons by the second pilot. The appearance of the device is shown in photo 7. The image in the device is created by a combined thermal and television system TADS/PWVS [12]. The device is powered by an on-board network of ~115 V 400 Hz and consumes 460 W. The viewing angle in azimuth is ±1200, in pitch (-70) – (+40)0. The target designation accuracy is 5 mrad, the target tracking speed is at least 120 deg/s. The field of view of the first pilot's display is 400 (horizontal) x 300 (vertical), and that of the second pilot is 50. The total weight of the device with all its units does not exceed 22 kg. The head-mounted part of the device weighs no more than 0.5 kg. Fig. 2 shows the general block diagram of the device, where: 1 helicopter, 2 – PWVS device, 3 – TADS device, 4 guided missiles, 5 – 30-mm cannon, 6 communication unit in the helicopter, 7 – fire control system computer, 8– character generator, 9 electronic display unit, 10 – display control panel, 11 – control circuit, 12 optical output of the sighting device, 13 first pilot HUD, 14 second pilot HUD, 15 positioning system sensor, 16 sighting electronic unit, 17– the observed image of the scene. The positioning system tracks the position of the pilot's head and synchronizes this data with the direction of the weapon. Sign-symbolic and service information is projected onto the observed image via the display.

Photo 7. IHADSS device

Fig. 2. Block diagram of the TADS/PWVS system

Elbit (Israel) [13] produces the MiDASH modular helicopter day/night device. Photo 8 shows the appearance of the Topowl day/night device for the French Air Force Tiger helicopter [14]. Photo 9 shows the appearance of the Striker HMD day/night device from the BAE Systems family for the European fighter [14]. Sextant Avionique has developed a day/night device for a South African helicopter [15]. The monocular HUD from Elbit and El-Op (Israel) is designed for daytime operation and input of service information from the cathode-ray tube screen [16]. The pilot’s second eye can be equipped with a night monocular. Photo 10 shows the Agile Eye HUD from Kaiser Electronics (USA) for the F-16A aircraft. The field of view of the device is 200 [16]. Photo 11 shows the integral HUD from GEC Marcony. It combines the HMS Falcon Eye and the Cats Eyes night vision goggles [2]. Here, the night channels are also located on the side surfaces of the helmet [16]. Photo 12 shows the appearance of the integrated day/night system MONARC by Honeywell (USA) [16]. In recent years, the field of view of similar devices has expanded to 135×350 [17], while the traditional value of this angle is 20 — 400 with a weight of 1.27 to 2 kg and a typical resolution of 3.5 mrad [18]. Achievements in the development of day/night HUD devices are mainly associated with the optimization of displays. Until recently, cathode ray tubes were used as displays.

In recent years, liquid crystal (LCD) indicators have become serious competitors to them [19]. Kaiser Electro-Optics (USA) has achieved significant success in this area. The main parameters of this company's displays are given in Table 2. The appearance of the Pro View™ 60 model is shown in Fig. 3. The main parameters of modern displays are given in Table 3 [22]. The creation of such displays is of great importance for the development of «day/night» devices not only in the interests of aviation, but also for special forces ground forces — to equip the «soldier of the 21st century». The ideology of developing its equipment is set out in [24 — 34]. From the analysis of these works it follows that the «soldier of the 21st century» should be equipped with a head-mounted «day/night» system. The night channel is either a night monocular [2] based on a fourth-generation image intensifier, or a low-level TV system based on an image intensifier coupled with a CCD matrix [35], plus a daytime color TV camera with integrated image output to a display.

This image is projected onto the soldier's helmet visor. A map of the area is also projected onto the same visor, indicating the soldier's position and quantitative data obtained via a satellite communications system and required for tying in firing positions, controlling precision weapons, and coordinating actions with other soldiers. The device may also include a magnetic resonance sensor for measuring coordinates with an accuracy of ±10 mrad [30]. The individual weapon is equipped with a thermal imaging sight, such as the AN/PAS-13 [26], the image from which is transmitted to the helmet display. This allows the soldier to fire at any time of day or night and in adverse weather conditions. The soldier can fire from cover, using only the machine gun, as shown in photo 13. In addition to the thermal imaging sight, the weapon may be equipped with a TV camera, laser rangefinder, digital compass, and laser IR target designator, such as the AN/PAQ-4C [26].

With the help of a TV camera, the data from all these devices is also transmitted to the helmet display. It is also equipped with a sensor that signals when a soldier is exposed to laser radiation. Fig. 4 shows the equipment of a “21st century soldier” with a head-mounted “day/night” system, and photo 14 shows the individual weapon of a “21st century soldier” from Alliant Techsystems (USA), equipped with a thermal imaging sight and a TV camera with round-the-clock and all-weather aiming. The total weight of the optical-electronic device does not exceed 2.4 kg with a power consumption of 6 W. The range of human detection is 800 m, vehicle recognition – 1000 m. The laser rangefinder measures the range up to 2500 m with an accuracy of ±1 m [31]. Such a system is being developed in the interests of the US Army under the Land Warrior (LW) program. However, the Rautheon company (USA) has created a prototype system that is 1.15 kg lighter than the device developed under the LW program [31]. Thus, progress in the field of creating such systems is obvious.

Photo 8. Topowl device

Photo 9. Striker HMD

Photo 10. Agile Eye device

Photo 11. Integrated HUD by GEC Marconi

Photo 12. MONARC system

Table 2. Main parameters of head-mounted displays by Kaiser Electro-Optics Inc. [21, 22]

Note. The weight of the device includes the weight of the helmet, optics, CRT

Fig. 3. Pro View™ 60 device

Photo 13. The principle of firing from cover,
ensuring the shooter’s safety

Fig. 4. Equipment of the “21st century soldier” with the head-mounted “day/night” system

Photo 14. Individual weapon of the “21st century soldier” by Alliant Techsystems

Table 3. Military displays based on liquid crystal (LCD) or active matrix liquid crystal (AMLC) indicators [23, 24]

Along with the “day/night” devices for the “soldier of the 21st century”, traditional directions of day/night devices also continue to develop. These include night vision goggles and portable devices – binoculars, such as the NUIT-UGO device by Thomson-CSF described above. The same company developed the S21T “night/day” binoculars for round-the-clock observation of targets and measurement of their parameters [24]. JSC ZOMZ developed the BDN day/night binoculars [37]. The device provides a stereoscopic image in both the day and night channels (photo 15). Synchronous channel switching is performed by a single key. The resolution limit in the “day” mode is 8°, in the “night” mode – 100°. The device is waterproof in rain, reliable and easy to operate. The built-in IR illumination source provides the ability to observe in complete darkness. The device operates at ambient temperatures from -30 to +350C. Other parameters of the device, as well as other day/night devices based on the image intensifier, are given in Table 1. Portable observation devices “day/night Bison”, “Centaur” and “Centaur-2” (Table 1) were developed at LOMO. The devices are based on the first generation image intensifier with a conversion factor of 1000. The resolution limit in the Bison device is 10″ in the “day” mode, 3.5′, in the “Centaur” device, respectively, 10″ and 3.5′. The focusing limits of the devices in the “day” mode are 2 m – Ґ, in the “night” mode – 0.5 m – Ґ [38].

Photo 15. Binoculars BDN

The company Simrad (Norway) has developed a “day/night” observation device KDN 250F (photo 16) [39]. It consists of standard modules: a night channel 1 and a day binocular 2. These modules are interfaced according to the diagram in Fig. 5a, where 1 is a mirror-lens objective, 2 is an image intensifier of generation II+ or III, 3ocular system, 4 – mirror with dichroic coating, transmitting the visible spectrum and reflecting in the spectrum of the glow of the image intensifier tube screen, 5 – day channel. In the circuit according to Fig. 5b, switching of mirror 4 allows additional coupling with the device of a video camera or photo camera 6. The company created the KDN 200 device, mounted on a tripod, using the same principle [39]. The devices can operate continuously for at least 80 hours at a temperature of 200 C. The operating temperature range is from -40 to +520 C. The resolving power of the device at night is 1 mrad/line/mm at an illumination of 10-3 lux, and during the day it is limited only by the capabilities of the eye. The focusing limits are 25 m – Ґ, and the eye base adjustment limits are 58 – 73 mm. The remaining parameters of the devices are given in Table 1. Photo 17 shows the 1PN54 “day/night” observation device [40]. It is designed to observe the terrain, reconnaissance of targets, and adjust artillery fire during the day and at night. The device is made in the form of a periscope with day and night branches. It can be mounted on a tripod or in an armored reconnaissance vehicle such as the BRDM. The vertical guidance mechanism and the scale for measuring elevation angles are located directly in the device body. The horizontal and vertical guidance mechanism with the scale for measuring azimuth angles is removable. The device is equipped with a compass and a level for leveling. The controls provide manual adjustment of the grid brightness, focusing of the night branch lens, switching between day/night modes, turning on the neutral filter in the day branch, closing the shutter of the night branch lens. Automatic adjustment of the image intensifier screen brightness is provided. The measurement range of horizontal and vertical angles is 60-00 and ±3-00, respectively*. The division value of the exact reading is 0-01. The remaining parameters are given in the table. 1.

Photo 16. KDN 250F device: 1 – night channel; 2 – daytime binocular

Photo 17. Device 1PN54

Fig. 5. Optical diagram of the KDN 250 F device

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