Research and development is being undertaken globally to enhance the reach, improve the resolution and reduce the weight of night vision devices in order to provide a better edge to own side

The term night vision device (NVD) usually refers to a complete unit, including an image intensifier tube, a protective and generally waterresistant housing, and some type of mounting system. Many NVDs also include sacrificial lenses, IR illuminators and telescopic lenses.

A vital ingredient of battlefield transparency is the ability to see by night. The side that can see better by night will have greater advantage. Research and Development (R&D) is being undertaken globally to enhance the reach, improve the resolution and reduce the weight of night vision devices in order to provide a better edge to own side.

The Indian Army too has night vision devices (NVDs) on its inventory in various categories and quantities albeit ideal equipping both in terms of quantity and quality are still a far cry. Say, for example, the hand held thermal imagers (HHTIs) that are in high concentration in insurgency afflicted areas like Jammu & Kashmir and which are yet to reach infantry battalions of strike corps in sufficient numbers. The philosophy for night vision accessories too needs refining if we are to learn from the mistakes of the past. For example, when the HHTIs were first imported from Israel and France only one charger per four HHTIs were procured. This created major problems with widely dispersed deployments in Jammu & Kashmir and forced the infantry to improvise chargers, which may have caused inadvertent damage to the equipment. Another example was of artillery which went in for numerous laser target designators but only one charger that was kept centrally at the School of Artillery and every time charging was needed, individual designators had to be flown in and out. Additionally, our Defence Research and Development Organisation (DRDO) and public sector undertakings (PSUs) are way behind in the field of NVDs compared to their foreign counterparts, whose night vision products are bulkier and of lesser resolution.

Inside the NVD

NVDs are of two types—image intensifiers and thermal imagers. 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 of a phosphorous screen which converts the electrons back into photons, letting you see an impressive night time view even when it’s really dark.

To understand thermal imaging it is important to understand that infrared (IR) can be split into three categories; first, near IR with wavelengths from 0.7 to 1.3 microns, or 700 billionths to 1,300 billionth of a meter; second, mid-IR with wavelengths ranging from 1.3 to 3 microns; third, thermal IR with wavelengths ranging from three microns to over 30 microns. Near IR is closest to visible light. Both near-IR and mid-IR are used by a variety of electronic devices, including remote controls. Thermal IR occupies the largest part of the infrared spectrum. The key difference between thermal IR and the other two is that thermal IR is emitted by an object instead of being reflected off it. IR light is emitted by an object because of what is happening at the atomic level. Most thermal imaging devices scan at a rate of 30 times per second. They can sense temperatures ranging from 20 degrees Celsius to 2,000 degrees Celsius and can normally detect changes in a temperature of about 0.2 degrees Celsius.

Thermal imaging devices are generally ‘uncooled’ or ‘cryogenically cooled’. The uncooled 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 inbuilt batteries. Cryogenically cooled devices have the 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 thesult from cooling the elements. Though more expensive and more susceptible to damage from rugged use, these systems enable a soldier to see whether a person is holding a gun more than 300 metres away. Unlike the traditional ones, most night-vision equipment which uses image enhancement technology, thermal imaging is great for detecting people or working in near-absolute darkness with little or no ambient light.