Night vision devices for armored vehicles..

Night vision devices for armored vehicles..

NIGHT VISION DEVICES FOR ARMORED VEHICLES

(End. Beginning No. 5, 2004)

The most widely used night sights (gunner's NVG) are based on the image intensifier tube. Their main parameters are given in Table 1, and the design scheme and appearance of typical samples are shown in Fig. 11, photo 1, respectively. The gunner's NVG can be made as a single-channel device, but can also contain a daytime optical channel, most often containing a laser rangefinder. It can be made on the basis of a solid-state laser based on YAG:Nd3+ with a wavelength of 1.06 μm. In recent years, laser rangefinders based on a solid-state laser based on erbium with a wavelength of 1.54 μm have become widespread. Radiation at this wavelength is safe for vision and cannot be detected using traditional NVGs based on the image intensifier tube (with the exception of the generation III+ image intensifier tube [1]). Typical parameters of laser rangefinders: range of measured distances 0.1 – 10 km, range measurement accuracy ± 5 m, range resolution 50 m, strobe limits 0.15 – 3 km, daytime sighting field angle 7 – 80, magnification 7 – 8x.

Table 1. Main parameters of the gunner's night sights (according to company brochures)

Fig. 1. Typical diagram of the gunner's night vision device
(NV 31 sight by Optic Electronic Corp., USA)

a – 1PN22M2M (GUP PO Refinery, Russian Federation);	b – 1k13-2 “BUG” (Belomo, Belarus);
в – М35Э1 (Optic Electronic Corp., USA);	g – NVL53 (United Scientific, UK);
d – NV32 (AVIMO, UK)

Photo 1. External appearance of typical gunner's night vision devices.

The gunner's night vision devices can change the position of their sighting axis vertically within the range from (-10) – (-20)0 to (+20) – (+70)0. The resolution of the night vision devices is 0.2 – 0.4 mrad. The day channel can have changeable magnifications of 1x, 8x with a field of view angle of 300 and 80, respectively. The night channel usually has a magnification of 6 – 8x with a field of view angle of 7 – 80. The focusing range is (25 – 50) m – µ. The detection range of a vehicle at a natural night illumination level (ENL) E = 10-3 lux is 2.5 – 3 km, recognition – 1.0 – 1.5 km. The exit pupil distance is 22 – 25 mm with its diameter of 5 mm. The diopter adjustment limits can be (-2) – (+6) or ±5 diopters.

Usually, the gunner's NVGs have either independent gyrostabilization of the head mirror in two planes, or dependent stabilization due to the kinematic connection of the head mirror of the night sight with the gyrostabilized mirror of the day sight. The accuracy of gyrostabilization is 0.3 — 0.5 mrad, the accuracy of adjustment of the position of the line of sight is (± 7) mrad.

If the ENO level drops sharply, then artificial additional illumination is required to maintain the previous range. Therefore, all types of night vision devices for armored vehicles must be additionally equipped with infrared (IR) illuminators. These can be IR spotlights based on arc or xenon lamps (Table 2). Typical IR spotlight circuits are shown in Fig. 2, and the appearance of typical samples is shown in Photo 2 [2]. In the OU-5 and L-4 spotlights, the ignition units for xenon short-arc discharge lamps of the DKsSh-180 and DKsEl-250 types with a power of 180 W and 250 W, respectively, are located in the rear cover 6 (Fig. 2). The OU-3 and L-2G floodlights use a PZh-27-110 floodlight incandescent lamp and a KG-27-200 halogen incandescent lamp with a power of 110 W and 200 W, respectively [2]. The floodlights use IKS-970 absorption IR filters [2]. The disadvantages of IR floodlights are their significant weight, dimensions, and energy consumption, as well as the strong dependence of the spectral characteristics of the IR filter (and therefore the energy intensity of the floodlight's light) on temperature (Fig. 3). The service life of IR floodlights without replacing the lamp does not exceed hundreds of hours.

a)

б)
Fig. 2. Schematic diagram of the OU-3G (a) and L4 (b) floodlights:
1 – housing,
2 – IR filter unit,
3 – reflector,
4 – light source,
5 – socket,
6 – rear cover,
7 – lamp anode unit,
8 – current-carrying bus [2]

a)

b)
Photo 2. Appearance of typical IR illuminators:
a – OU-3G [1];
b – L4 [1];

Fig. 3. Curves of spectral sensitivity S? of multi-alkali (1) and oxygen-silver-cesium (2) photocathodes of image intensifier tubes, radiant power I of xenon arc lamp of DKsEl-250 type (3) and influence of heating temperature on transmittance T of lamp radiation with IKS-970 filter (4) at temperatures: 20? C (I), 50? C (II), 100? C (III), 150? C (IV), 200? C (V), 250? C (VI), 300? C (VII) [2]

Table 2. Illuminators for armored vehicles

In this regard, the creation of IR illuminators based on ILPI is of interest [3, 4]. The diagram of a typical laser illuminator and its appearance are shown in Fig. 4 and photo 3, respectively. OJSC SKS Peleng (Belarus) has developed laser IR illuminators for armored vehicles [3, 4]. The IL-1 model based on the ILPI-114 laser emitter has a luminous intensity of 470 W/sr, an average radiation power of 0.15 W, an illumination angle of 1.5×0.750, a radiation pulse duration of 130 ns, an operating frequency of up to 5.2 kHz, a wavelength of 0.85 μm, a weight of 7.3 kg, dimensions of 246x174x177 mm, power consumption (with heating of the protective glass) no more than 50 W, without heating 20 W when powered from the on-board network = 27+2-5 V in the operating temperature range of (-50) — (+50)0 C [4]. Other models OU-6 and OU-6-01 have the same output parameters except for weight and power consumption. They are 15 kg and 100 W, respectively. This is due to the presence of an additional mechanism for pumping the optical axis of the illuminator vertically: in the OU-6 illuminator within the range from (+6)0 to +(30)0, in the OU-6-01 illuminator — from (+8)0 to (+32)0. The illuminator also provides for the movement of its optical axis horizontally within ±50 [4]. The continuous operating time of all these illuminators is 6 hours with a total resource (without replacing the ILPI) of 200 hours. The advantage of laser illuminators is that they create a uniform in terms of the distribution of energy brightness of a rectangular illumination spot with sharply defined edges, while IR spotlights create an illumination spot with a Gaussian distribution of energy brightness, so that the brightness in the illumination spot will fall from the center of the spot to its edges in the absence of its clear boundaries. The operating wavelength of the ILPI changes depending on the temperature change at a rate of 2.5 A/0 C. To ensure sufficient effective energy intensity of the illuminator light taking into account such wavelength drift, either automatic change of the ILPI pump current depending on the temperature or thermoelectric stabilization of the ILPI wavelength is used. Pulsed laser illuminators can be used practically without changes in the composition of the AI ​​NVD complex, if synchronization of the AI ​​NVD strobe unit with the illuminator pumping unit is provided.

Fig. 4. Design of the laser illuminator:
1 – beam forming lens,
2 – ILPI,
3 – pumping unit

Photo 3. External appearance of the PL-1 laser illuminator [3, 4]

IR illuminators for armored vehicles can also be made on the basis of powerful IR light-emitting diodes [5, 6]. The diagrams of their possible design are shown in Fig. 5, and the appearance of typical samples is shown in Photo 4. The diagram with a remote lens (Fig. 5a) provides for the possibility of separate installation in the illuminator of IR LED 2 and lens 1 for forming its radiation. IR LEDs U-193 have a radiation power of 0.17-0.23 W at a current of 0.5 A and 0.35-0.44 W at a current of 1.0 A and a voltage of =3 V. The radiation divergence angle at a level of 0.5 is 300. IR LED U-193A contains one emitting crystal measuring 1×1 mm. IR LED U-280A contains 6 crystals measuring 1×1 mm, connected in series. This LED has a radiation power of 1.1 — 1.3 W at a current of 0.5 A and 1.5 — 1.8 W at a current of 1.0 A and a voltage of = 12 — 14 V. The radiation divergence angle at a level of 0.5 is 500 [5]. The disadvantage of the circuit in Fig. 5a is the significant longitudinal size of the illuminator. To reduce it, it is advisable to move on to an illuminator that is made according to the group emitter circuit (Fig. 5b). Such an illuminator U-200IK contains 12 IR LEDs of the AOI 12T type. All these LEDs are mounted on a radiator. Their optical axes are mutually parallel and aligned with the optical axes of the corresponding Fresnel lenses, made in the form of a single plastic block. The radiation of all the LEDs is summed up in a single illumination angle, determined by the illumination angle of one module (LED + its lens — Fresnel lens). The U-200IK-A model has a radiation power of 0.7–1.0 W at a current of 0.6 A and an illumination angle of 50, and the U-200IK-B model has a power of 0.9–1.2 W at the same current and an illumination angle of 300. The supply voltage is =12 ± 0.5 V. The weight of the UK-200IK illuminators does not exceed 1.5 kg, the dimensions are Ж170х120 mm. All LEDs can have a wavelength of 0.85 ± 0.01 μm or 0.86 ± 0.02 μm. The operating temperature range is (-40) – (+55)0 C, the service life is at least 5×105 hours. The IR LED can have a built-in radiation shaping lens (Fig. 5c) [6]. Its model AL 148A has a radiation power of 0.2 (1.0) W at a current of 1 A (6 A) and a voltage of =12 V, an illumination angle of 6 — 80, and a radiation wavelength of 0.81 ± 0.01 μm [6]. Such an IR LED can be used for AI NVD, since it can operate in a pulsed mode with a radiation pulse duration of 100 ns, an operating frequency of 5 kHz, and a pulse current of 30 — 40 A [6]. The radiation power of the LED is 5 — 9 W/C, while the radiation power of the U-193 and U-288 LEDs is 0.35 — 0.7 W/C and 0.6 — 0.7 W/C, respectively, and the U-200IK-A and U-200-IK-B illuminators are 60 W/C and 2 W/C, respectively. The advantage of the AL 148A LED is its small transverse dimensions, but this creates the risk of contamination. It is possible to create a group emitter from the required number of these LEDs.

a – with a remote lens:
1 – radiation forming lens,
2 – IR LED;

b – group emitter of 12 modules:
1 – Fresnel lens board,
2 – LED board,
3 – heat sink;

в – with built-in lens:
1 – built-in lens,
2 – IR LED glow body,
3 – electrical output,
4 – threaded rod for mounting the LED

Fig. 5. Scheme of LED illuminators:

а – with built-in lens;

b – group emitter
Photo 4. External appearance of the LED illuminator.

The half-width of the spectrum of laser illuminators based on the ILPI is 3-5 nm, and that of LED illuminators is 50-60 nm. In this regard, laser illuminators provide better quality of spectral target selection when a narrow-band filter is installed in the NVG, and LED illuminators create better matching of their radiation spectrum with the photocathode of the image intensifier tube. The choice of a specific type of illuminator is determined by the features of the NVG and various generations of image intensifier tubes [8].

Thus, there are various options for NVG and their illuminators, which allows you to choose the best option for almost any armored vehicle.

Literature.

1. Zakharov A. MILEX 2003. ARMS Defense Technologies Review, 2003, No. 3 (16), p. 54.
2. Basov Yu.G., Rakviashvili A.G., Sysun V.V. Infrared searchlights of constant radiation./Optical journal, 2003, v. 70, no. 3, pp. 59–64.
3. Volkov V.G. Laser illuminators and target designators for night vision devices./Special equipment, 2002, no. 2, pp. 2–10.
4. Arkhutik S.T., Zaitseva E.I., Kozlov K.V. Results of modernization of night vision systems. XVII International scientific and technical conference on photoelectronics and night vision devices. Abstracts of reports. RF, M., 2002, p. 167 – 168.
5. Infrared LEDs and Illuminators Based on Them. Prospectus of NPI OEP “OPTEL”, RF, M., 2004.
6. Villisov A.A., Zakharov G.N., Kukhta A.M., Nefedtsev I.V. Powerful Emitting Diode AL 148 A. Electronic Industry, 1990, issue 10, pp. 130 – 134.
7. PH 14 Xenon ARC Searchlight for Visible and Infrared Light. Prospectus of Sopelem, France, 1990.
8. V.G. Volkov. Night vision devices of new generations./Special equipment, 2001, No. 5, pp. 2 – 8.