Night Vision Technologies
Night vision devices (NVDs) comprise an image intensifier tube, a protective housing and a mounting system. Many NVDs also include sacrificial lenses, infrared illuminators and telescopic lenses. Night vision goggles, night-scopes, night-monocular, night
Night vision devices comprise an image intensifier tube, a protective housing and a mounting system.
THE URGE FOR THE ability to see by night went up in wartime but today conflict situations are an everyday affair. Night vision devices ( NVDs) comprise an image intensifier tube (IIT), a protective housing and a mounting system. Many NVDs also include sacrificial lenses, infrared (IR) illuminators and telescopic lenses. NVDs are being used by the security sector as well as civilians. Night vision goggles (NVGs), night-scopes, night-monocular, night weapon sights are vital to any army. Longer reach and improved resolution promotes the chances of winning.
Types of NVD
NVDs are of two types: image intensifiers (II) and thermal imagers (TI). Image intensifiers are more common as their light amplification technology uses the small amount of ambient light like moon, stars-light and converts this light energy (photons) into electrical energy (electrons). These electrons pass through a thin disk that’s about the size of a small coin and contains more than 10 million channels. As the electrons go through the channels, they strike the channel walls, releasing thousands of more electrons. These multiplied electrons then bounce off of a phosphorous screen which converts the electrons back into photons, letting you see even when it’s pitch dark. To understand thermal imaging, it is important to understand that IR can be split into three categories; near IR (0.7 to 1.3 microns wavelength), mid IR (1.3-3 microns wavelength) and thermal IR (three microns to over 30 microns wavelength). The key difference between thermal IR and the other two is that thermal IR is emitted by an object instead of reflected off it. Most thermal imaging devices scan at a rate of 30 times per second, sense temperatures from -20 degree Celsius to 3,600 degree Celsius and can detect changes in temperature of about 0.2 degree Celsius. Thermal imaging devices are generally ‘un-cooled’ or ‘cryogenically cooled’. The un-cooled ones are more common wherein the IR detector elements are contained in a unit that operates at room temperature. These devices are noiseless, activate immediately and have in-built batteries. Cryogenically cooled devices have elements sealed inside a container that cools them to below zero degree Celsius. The advantage of such a system is the incredible resolution and sensitivity that result from cooling the elements. These systems enable identifying whether a person is holding a weapon more than 300 metres away. Thermal imaging can detect persons in near-absolute darkness with little or no ambient light.
Categories
NVDs are generally classified into four categories albeit with differing classifications— some classify them as generation zero, one, two, three and four (yet to be defined) while others classify them as generation one, two, three and four. Advanced version of generation three is also being referred to as generation three ultra. Classification of NVDs depends on what type of image intensifier tube (IIT) is used in the particular device:
Zero-generation: These were sniper scopes used in World War II, not really IITs but image converters requiring a source of invisible IR light mounted on or near the device to illuminate the target.
First-generation: These were Starlight Scopes developed in early 1960s. They produced an image that was clear in the centre of the field of view but suffered from large optical distortion around the periphery.
Second-generation: Development of the micro channel plate (MCP) in the late 1960s ushered the second generation NVDs which are high quality with exceptional brightness and resolution. The MCP accelerated and multiplied electrons substituting coupling of three IIs of the first generation.
Third-generation: Fielded in the early 1980s, these devices saw two major technological improvements; gallium arsenide (GaAs) photocathode and ion barrier coating to the MCP, providing combined increase in resolution, signal to noise ratio and photosensitivity over tubes with a multi-alkali photocathode—increasing sensitivity to light from the near-IR range of the spectrum, greater detection distances, improved system performance under low-light conditions and operational life in excess of 10,000 hours compared to 2,0004,000 hours of second generation tubes.
Fourth-generation: In 1998, gated filmless technology was created by removing the ion barrier film and gating power supply enabling substantial increases in target detection range and resolution. The filmless micro channel plate provides a higher signal-to-noise ratio than standard third-generation IITs resulting in better image quality under low-light conditions. Autogated power supply improves image resolution under high light conditions and a reduced halo effect that minimises interference from bright light sources. The reduced Halo maximises the effectiveness of the NVD in dynamic lighting conditions. However, it was found that the same performance results could also be achieved using a third-generation tube with a thinner ion barrier film and an auto-gated power supply.
Subcontinental Scene
Indian Army has on its inventory in various categories and quantities of NVDs but ideal equipping both in terms of quantity and quality is yet to be achieved. In 2008, media had reported the lack of NVDs in Indian Army particularly in the 3,000-strong tank fleet (only 10 per cent of tanks had night-fighting capability) and soldiers faced glaring shortages of NVDs, with NVDs in service a generation behind what Pakistan already had; Indian Army was holding second-generation NVDs while Pakistan had a range of third-generation NVDs from the US under the War on Terror Pact. Finally in April 2013, The Ministry of Defence (MoD) approved a ` 2,820 crore proposal to provide NVDs to the Indian Army; 5,000 thermal imagers (TIs) will be procured from the Bharat Electronics Limited (BEL). Though Pakistan continues to receive modern NVDs from the United States to fight terrorism, its Institute of Optronics (IOP) also manufactures NVDs for Pakistan armed forces; crew served night vision weapon sight (TVS-5A), individual served night vision weapon sight (PVS-4A), driver’s night vision periscope (DNVP-1A) and aviator’s night vision goggle. IOP’s future plans include NVDs for armoured vehicles and helicopters. India’s BEL is understood to have partnered with Photonis after considering extending a relationship with ITT Exelis. ITT Exelis has set up offices to pursue the Indian market post memorandum of understanding (MoU) signed with Tata at 2012 Defexpo for manufacturing systems using imported US tubes. Reportedly, Qioptiq’s Kite sight has been trialed with India since 2009 with a potential acquisition later this year with demonstrations of the company’s TI and II solutions having begun. Qioptiq also established a joint venture with Rolta in 2009 to pursue opportunities in India. America Technology Network (ATN) says it sold to India MARS 4 and 6 TI weapon sights and the monocular NVM-14 in 2011 for the Army. Similarly, Optix says they have several projects in India, three of which are with the Navy including sales of the twin-tube Diana variant NVG.