Day-night sight technology.

Day-night sight technology..

DAY-NIGHT SIGHT TECHNOLOGY”.  

Modern anti-terrorist and special operations are highly dynamic and place strict demands on sights for individual weapons. One of the main requirements is to ensure round-the-clock operation. In this regard, this review examines the technology of constructing “day-night” sights.

The simplest and cheapest technical solution for ensuring round-the-clock operation is to equip the daytime sight with a powerful but compact illuminator (spotlight). In particular, the Nite Tracker SU-200 [1] spotlight from Divecon (Russia) is based on a xenon lamp operating from a DC voltage of 6 V. The spotlight consumes 20 W and provides a luminous intensity of 2×105 cd. The lamp is at the focus of the parabolic reflector. Additionally, to narrow the divergence of the spotlight beam, a heat-resistant lens is installed in the front part of its housing. The housing itself is made of ABS plastic, sealed, has increased strength and has a damping device to absorb shock loads that occur when firing. The spotlight is installed on the daytime sight in a mounting socket and is rigidly fixed in it. The spotlight is connected to the battery (capacity 2.4 2.8 A/h) by means of a cord with a waterproof push-button switch. The case with the battery is attached with Velcro to the desired side of the butt. A plate switch is attached to the fore-end in a convenient place with Velcro.

A foreign analogue of such a searchlight is the ORT-TLS 8 model from ORTEC (USA) [2]. The searchlight weighs 0.3 kg, has dimensions of W45x95 mm, and consumes 0.7 A. International Technologies (Lasers) (USA) has developed an underbarrel illuminator-target designator S-8, which illuminates targets at night at a distance of 100–150 m [2]. The illuminator, based on a halogen lamp, has an illumination angle of 0.70 at half the radiation intensity, luminous intensity of 22,500 cd, a service life of 100 hours, dimensions of W71x165 mm, and a weight of less than 950 g, including the battery (photo 1). The same company created the Set Beam illuminator based on a 150 W xenon lamp, which is mounted on the weapon next to the daytime sight (photo 2) [2]. The illuminator has an illumination angle that can be changed from 0.30 to 60, operates on a voltage of =12 V (current consumption is 17 A), =24 — 30 V or from ~220 V, and weighs 3.2 kg (without a power source). The illuminator's luminous intensity is 25×105 cd. It is equipped with an infrared (IR) filter for working with a night sight (in the spectrum range from 0.78 to 2.2 μm) and can function in pulse mode with a frequency of 7±1 Hz and a pulse duration of 400±50 μs. This mode is necessary to create optical interference for the enemy [2].

Photo 1. Under-barrel illuminator-target designator S-8
by International Technologies (Lasers), USA

Photo 2. Set Beam
illuminator by International Technologies (Lasers), USA

BeLOMO (Belarus) has developed under-barrel flashlights for light small arms – the “Znich” (photo 3a) and “Gyurza” (photo 3b) models with a range of 100 and 25 m, an illumination angle of 300 and 430, a weight of 330 and 120 g, dimensions of 155x46x42 and Ж20×130 mm, and a supply voltage of 6 V and 3 V, respectively [3].

Photo 3. Under-barrel flashlights for light
small arms manufactured by BeLOMO, Belarus

a) “Znich”

b) “Gyurza”

The advantage of daytime sights with an illuminator is the stunning effect when it is suddenly turned on in the dark and the relatively low cost. For example, the Nite Tracken SU-200 model costs $70 — 80. The disadvantage of such day-night sights is the unmasking of the work, high energy consumption, significant weight, dimensions and limited battery life.

Night sights based on image intensifier tubes (IITs) [4] with a strongly apertured objective lens can also operate during the day, but their range is limited by the relatively low resolution of the IIT and does not provide natural color rendition of the observed scene. In addition, the IIT operating life is limited — (2-3) x 103 hours, and its cost is high. Therefore, operation of a night sight based on an IIT in daytime conditions is permissible only for checking operability and ensuring alignment. To implement round-the-clock operation, it is necessary to introduce a day channel into the night sight.

An example of such a day-night sight is the OV-50 model by Sopelem (France) [5]. Photo 4 shows the sight mount on the weapon. Fig. 1 is a diagram of the sight, where 1 is a day channel with a flat mirror, 2 is an eyepiece, 3 is a cube prism, 4 is an image intensifier of generation 2+ or 3 [6], 5 is a night channel lens. The day and night channels of the sight are combined using a cube prism (3) and have a common eyepiece (2). The range of recognition of a full-length human figure in the sight in starlight is 500 m, the angle of view of the sight is 110, magnification is 3.2X, and the weight is 900 g. The disadvantage of the sight is the presence of a cube prism, which reduces the image quality. In addition, the magnification of 3.2X is not high enough for the day channel. In this connection, a more advanced “day-night” sight circuit has been developed [7], shown in Fig. 2, where 1 is the daytime channel objective, 2 is the daytime channel inversion system, 3 is the semitransparent mirror, 4 is the eyepiece, 5 is the image intensifier tube, 6 is the nighttime channel objective. The central part (1) with a diameter of 25 mm of the nighttime channel objective is used here as the daytime channel objective. The daytime channel has a magnification of 6.6X with a field of view angle of 6.50, and the nighttime channel, respectively, 3.3X at 120. The exit pupil distance is 34.6 mm with a diameter of 3.8 mm for the daytime channel and 5 mm for the nighttime channel. The semitransparent mirror provides a sufficiently high image quality in both channels. The range when using a generation 2+ image intensifier is 550 m, and the weight of the sight does not exceed 2.2 kg.

Photo 4. Day-night sight OV-50 by Sopelem, France

Fig. 1. Diagram of the OV-50 sight

Fig. 2. Diagram of a sight based on an image intensifier tube

Fig. 3 shows a diagram of a day-night sight with the same parameters, but with a mirror-lens objective (1), which, compared to a lens, has less weight and better image quality. The objective (4) of the day channel is introduced into the non-working central hole of the objective (1). In Fig. 3, position 2 is the image intensifier, 3 is the eyepiece, 5, 6, 8 are flat mirrors, 7 is the erecting system, 9 is the aiming scale. The weight of the sight does not exceed 1.95 kg, the range of the night channel is 600 m [7].

Fig. 3. Scheme of a day-night sight with a mirror-lens objective

The day-night sight PDN by JSC ZOMZ (Russia) (photo 5) has a field of view angle for day/night modes of 4030× – 40/7020×40, respectively, magnification 2.5 – 6.2X, angular resolution limit of 6.5?ґ/50ґґґ, weight 1.6 kg, dimensions 95х125х86 mm [8]. The sight uses a generation 2+ image intensifier. The POND-4 sight by TsKB Tochpribor and NPP Tekhnika (Russia) has a range of 300 m (at night in starlight), a field of view angle of 80 (night) and 6.50 (day), weight 2 kg, and supply voltage of 3 V [9]. The LOMO day-night sight (Russia) has a field of view of 4.20, a magnification of 9X (day) and 6X (night), dimensions of 300x100x70 mm, and a weight of 1.5 kg [10].

Photo 5. PDN sight of the Zagorsk Optical and Mechanical Plant, Russia

Litton (USA) has developed two models of the AN/PVS-10 [11] day-night sight based on a 3rd generation image intensifier tube. One model has a magnification of 8.5X, a field of view of 20, and a weight of 2.04 kg, while the other model has a magnification of 12X, a field of view of 20, and a weight of 2.27 kg.

The ITT company (USA) has developed the F4961 day-night sight (photo 6) for various types of individual weapons [2]. It combines a daytime collimator sight, which creates an image of a red luminous dot on the target, with a night channel based on a generation 3 image intensifier. The day and night images, together with the red luminous dot, which acts as a sighting mark, are observed through the same eyepiece. The sight has a magnification of 1X. The field of view is 400, the dimensions are 250x85x56 mm, the weight is 570 g, the supply voltage is 3 V, and the continuous operation time is up to 20 hours. For firing the Stinger SAM, the ITT company has created the F4960 day-night sight [2]. The night channel uses a generation 3 image intensifier. The eyepiece of the night channel is located under the right eye, and the daytime collimator sight is located under the left eye of the operator (photo 7). The sight has a range of 7 km for an aircraft, a field of view of 23.50, a magnification of 2.26X, dimensions of W102x305 mm, a weight of 1.9 kg, and with a weapon mounting bracket — 2.27 kg, a supply voltage of 3 V, and a continuous operation time of over 30 hours.

Photo 6. Sight for individual weapons F4961 by ITT, USA

Photo 7. Sight F4960 for shooting Stinger missile defense company ITT, USA

The original diagram of the KN250 day-night sight by Simrad (Norway) with a night mirror-lens attachment is shown in Fig. 4 [12], where 1 is the night attachment housing, 2 is the mirror-lens objective, 3 is the image intensifier, 4 is a prism with a roof, 5 is the transfer optics, 6 is the protective glass, 7 is a mirror with a dichroic coating that transmits visible light but reflects in the spectrum of the glow of the image intensifier screen, 9 is a day sight mounted on the weapon. The solid line in Fig. 4 shows the path of the rays in the night channel, and the dotted line in the day channel. The nature of the sight installation on the weapon is shown in photo 8. The magnification of the night attachment formed by components 1 — 4 is 1X, the field of view angle is 120. The magnification of the sight as a whole is determined by the magnification of the daytime sight (6), coupled with the attachment 1 — 4. The unified landing place of the attachment with the daytime sight allows the attachment to be coupled with various types of sights. The weight of the attachment does not exceed 790 g. It uses an image intensifier of generation 2+ or 3.

Fig. 4. Scheme of the KN250 sight by Simrad, Norway

Photo 8. Fastening the night attachment to the sight

However, night attachments can also be installed in the eyepiece section of a daytime sight, for example, the Dedal-DN510 2.5 – 7.3×50 sight by Dedal-NV [13]. Fig. 5 shows a sight with interchangeable day and night modules. The night module includes an objective lens, an image intensifier, and an eyepiece. An IR illuminator is attached to the side of the sight body for operation in complete darkness (radiation power of 35, 75, or 200 mW). The range of the sight with a night module is 450 – 800 m (with an illuminator – 100 – 250 m), the field of view angle can be adjusted within the range of 5.20 to 120, and the magnification – within the range of 3 – 7.3X (generation 2 image intensifier) ​​or 2.5 – 6X (generation 3 image intensifier). The day module has the same field of view angles and adjustable magnification within the range of 2.5 – 6X. The exit pupil distance of the sight is 45 mm. The longitudinal size of the sight for day/night modes is 320/345 mm, weight is 810/850 g, the supply voltage of the night attachment is 3 V. The Dedal-NV company has developed the Dedal-DN530 3.0 (3.7) x 66 sight (gen. 2, 2+, 3) with replaceable attachments (photo 9). Unique high-quality optics provide a long observation range (450 – 1000 m at low light levels and more than 250 m in complete darkness with an IR illuminator of 75 mW and 200 mW). The field of view angle is 100, the magnification for day/night modes is 3.0X /3.7X, respectively. Exit pupil distance 50 – 70 mm. Longitudinal size of the sight for day/night modes – 305/74 mm, weight – 970/1060 g, power supply voltage of the night attachment 3 V

Fig. 5. Day-night sight Dedal-DN510 2.5 – 7.3×50
by Dedal-NV, Russia

Photo 9. Sight Dedal-DN530 3.0 (3.7) x66

The F7201 day-night sight by ITT (USA) [14] with similar attachments has a magnification variable from 2.5X to 10X and a field of view variable from 6.80 to 20. The sight weighs 900 g in day mode and 1.3 kg in night mode, with longitudinal dimensions of 336.5 and 350 mm, respectively. ITT (USA) has developed a day-night sight in which the TRIJICON A-COG collimator sight is coupled with the AN/PVS-14 night monocular [15,16]. The AN/PVS-14 monocular based on a generation 3 image intensifier has a field of view of 130 and a magnification of 3X [16]. The MANTIS night monocular by Litton (USA) has found the same application. Its magnification is 1X, the field of view is 400, and the weight is 450 g [17]. This technological design is simple, lightweight, but has a number of disadvantages. These include significant longitudinal dimensions, inconveniences associated with the need to replace attachments. The objective of the daytime sight is designed for the visible, and not for the near IR region of the spectrum, which is necessary for a night sight. This has a negative effect on the image quality. In addition, the objective has a relatively low light transmission (1:2 instead of 1:1.5 for a standard objective of a night sight), which reduces the range of the night channel.

A sighting system consisting of a laser target designator and night vision goggles has become widely used. The laser target designator is mounted on the weapon and sighted in together with it. The semiconductor laser of the target designator forms a light spot on the target, emitting either in the visible (red) region of the spectrum (630–670 nm) or in the near IR region of the spectrum (820–850 nm). In the first case, the illumination spot is visible to the naked eye, in the second case – only through night vision goggles. When firing, the bullet hits the target exactly where the light spot is aimed. Therefore, instead of the usual aiming, it is enough to align the light spot with the target – and you can open fire. Aimed shooting can be carried out from any position of the weapon, including while moving. Photo 10 shows the shooter's appearance with night vision goggles on his head and a laser designator mounted under the barrel of the machine gun. Photo 11 shows a laser designator mounted on a pistol, photo 12 shows regular ones, and photo 13 shows holographic night vision goggles.

Photo 10. The shooter's appearance with night vision goggles
and a laser designator,
mounted under the barrel of the machine gun

Photo 11. Laser designator
for the Glock pistol

Photo 12. Regular night vision goggles

Photo 13. Holographic night vision goggles

The light spot from the laser designator emitting in the red spectrum is visible around the clock. But to see the target and its surroundings at night, night vision goggles are needed. Regular goggles are inoperative when exposed to light interference (gunshot flashes, explosions, fire flames, headlights, etc.) and are automatically switched off. So-called holographic night vision goggles are more flexible in this regard, for example, the HNV-1 model from OIP (Belgium) [19, 20]. HNV-1 goggles are based on generation 2+ or 3 EOP, have a field of view of 40×300 (night) and 1000 (day), weigh 800 g, and have a supply voltage of 3 V. The disadvantage of such sights is their short range, limited by the capabilities of night vision goggles (150 — 250 m).The disadvantage of all the above-mentioned day-night sights is their inability to operate in low atmospheric transparency (haze, fog, rain, snowfall, smoke, etc.). Thermal imaging sights for individual weapons based on uncooled focal plane arrays of IR photodetectors and operating in the mid-IR spectrum region of 8–12 μm, where radiation scattering in the atmosphere is minimal, can operate in such conditions. Therefore, such sights operate in low atmospheric transparency. These sights, which respond to the radiation of heated bodies, operate around the clock. An example is the SRTS sight from Texas Instruments (USA) [21] (photo 14). The sight weighs 1.6 kg, has a range of 1000 m for a full-length human figure, and a field of view of 8×40. Power consumption is 4 W with a startup time of less than 10 s. However, a serious obstacle to the widespread use of such sights is their high cost. The real price of individual IR matrices alone in 2001 was $7-20 thousand, and the price of sights based on them reaches several tens of thousands of dollars [22]. A decrease in average prices for such devices is not expected until 2006 [22].

Photo 14. Thermal imaging sight SRTS
by Texas Instruments, USA

In this regard, it is necessary to search for cheaper devices. A television (TV) sight can be used as one. It consists of a television camera mounted on the weapon and sighted in with it, and a head-mounted TV display mounted on the shooter's helmet. Modern TV cameras on CCD matrices have a sensitivity ranging from 3×10-3 to 2×10-5 lux, which corresponds to the capabilities of the image intensifier tube [23]. Such cameras can operate around the clock due to their sensitivity, which is automatically adjusted over a wide range. The signal from the TV camera is transmitted to the TV display using a miniature radio relay communication line. The appearance of a shooter equipped with such a system is shown in photo 15. A sighting scale and a sighting mark are formed in the electronic channel of the TV camera. They are observed together with the image of the target and the terrain on the TV display. The shooter only needs to position the weapon in such a position that the sighting mark coincides with the target — and he can open fire. This provides the same advantages as the use of a laser designator + night vision goggles, but when operating in passive mode. In addition, the range is now limited not by the capabilities of the goggles, but by the TV system and reaches 400 — 600 m. Effective suppression of light interference is possible in the TV channel. Remote transmission of images is possible. But the main thing is that shooting from cover is possible — only the shooter's hands holding the weapon remain unprotected. The cost of such a complex does not exceed $ 1000 — 1500, i.e. it is close to the cost of night vision goggles. An example of such a TV sight is the F2000IW model from Pilkington (United Kingdom) [24], as well as the Argus-21 device [25] with a detection range of a full-length human figure on a starry night of 350 m with a field of view of 8 — 100, supply voltage = 12 V, dimensions and weight of the TV camera Ж40×160 mm and 1.5 kg, and the TV display — respectively 210x195x110 mm and 0.5 kg. In the future, instead of a TV camera, a thermal imaging camera, which was already mentioned above, can be used when its cost is at an acceptable level. In this case, we will get an all-weather “day-night” sighting complex.

Photo 15. Appearance of a shooter equipped with a TV sight

Thus, there are a sufficient number of types of “day-night” sights with different capabilities, but it seems that the most promising sights are those that allow safe shooting from cover.

Literature.

1. Nite Tracker SU-200. Divecon Company Prospectus, RF, M., April 2001
2. Janeґs Infantry Weapons1999–2000, USA, pp. 720, 749, 765, 796.
3. Catalog of sights for small arms. Belarusian Optical-Mechanical Association. Belarus, Minsk, 2000.
4. Salikov V.L. Iceberg of high technologies of the domestic military-industrial complex. Review of the markets of night vision devices of Russian production//Special equipment, 2000, No. 3, p. 2 12.
5. Pengelley R., Hewish M. Fighting the 24-hour battle. 1987, No. 8, pp. 1101–1105.
6. Salikov V.L. Night vision devices: history of generations//Special equipment, 2000, No. 2, pp. 40 – 47.
7. Volkov V.G., Dobrovolsky Yu.A., Koshchavtsev N.F., Kuskova M.A., Leonova G.A. Small-sized day-night observation devices//Applied physics, 2000, No. 5, pp. 50 – 53.
8. Hunting sights PNP-1, PNP-3, PDN. Prospect of OAO ZOMZ, RF, Moscow region, Sergiev Posad, 2000.
9. Day/night sight POND-4. Prospect of the Central Design Bureau Tochpribor, Russian Federation, Novosibirsk, 2000.
10. LOMO round-the-clock sight. Prospect of LOMO, Russian Federation, Saint Petersburg, 1995.
11. AN/PVS-10. Day and Night Sniper Sight. Brochure by Litton, USA, 1997
12. Simrad KN 200/KN250. Brochure by Simrad Optronics, Norway, 1999
13. Day/Night Vision Riffle Scope Dedal-DN510 2.5-7.3×50. Brochure by Dedal-NV, RF, Moscow, 2000
14. ITT F7201 modular day/night weapon sight. Brochure by ITT, USA, 2000
15. Reflex sight. Janeґs International Defense Review, 2001, No. 1, p. 61.
16. AN/PVS-14. Monocular Night Vision Devise (MNVD). Brochure by ITT, USA, 1997
17. Multi-Adaptive Night Tactical Imaging System (MANTIS). Brochure by Litton, USA, 1997
18. Night Vision Goggles. Brochure by Litton, USA, 1997
19. New goggles provide better night vision. Laser Focus World, 1990, Vol. 26. No. 5, p. 82.
20. HNV-1 Goggles. Brochure by OIP Optics, Belgium, 1992
21. SRTS-Sniper Sight. Brochure by Texas Instruments, USA, 1990
22. Ushakova M.B. Thermal imagers based on uncooled microbolometric matrices: current state of the foreign market and development prospects. State Unitary Enterprise “NPO Orion”, Russian Federation, Moscow, 2001.
23. Kulikov A.N. Television surveillance in difficult conditions//Special equipment, 2000, No. 5, pp. 13 – 19.
24. Cutshaw C.O., Pengelley R. Infantry weapons aimed at integration age. Janeґs International Defense Review, 2000, Vol. 33, No. 10, pp. 46 – 53.
25. Night television viewer Argus-21. Prospectus of the firm KTI PM SB RAS, Russian Federation, Novosibirsk, 1995.