In present context Electro-optics instruments are used for range of applications - surveillance, reconnaissance, target acquisition, engagement, and missile guidance. The author deliberates on Indian Army Rifle mounted Sights requirement.
In this contemporary era, it is crucial to equip our soldiers with advance technology. Challenges persist in the area of sights for personal weapons, rifle optics, with troops usually having to rely on difficult to use and inaccurate methods of observation and engagement. Today, optics is highly capable to provide our soldiers with significant accuracy and engagement time for shooting. These sights are used for range of applications surveillance, reconnaissance, target acquisition, engagement, and missile guidance. Weapon mounted scopes are now a must feature in any soldier's gun. Significantly, it translates into safety and cost saving when it comes to ammunition. It increases the probability of accurate hit, while also reduce time to accurately engage a target and to effective firing. The developments in the Rifle optics continue to move swiftly, with advantage in target identification, magnification and programmability. However, challenge endures in making a light weight and reducing the space availability, for these accessories on weapons.
Recent advancements in optics, detector technology and signal processing have enabled advancement in the night vision technology through:-
- Image Intensifier System
- Thermal Imaging (TI) System
IMAGE INTENSIFIER SYSTEM
NVD gathers ambient light (starlight, moonlight or infra-red light) through the front lens. This light, which is made up of photons goes into a photocathode tube that changes the photons to electrons. The electrons are then amplified to a much greater number through an electrical and chemical process. The electrons are then hurled against a phosphorus screen that changes the amplified electrons back into visible light that you see through the eyepiece. The image seen is a clear green-hued amplified re-creation of the scene being observed.
- Excellent low-light level sensitivity.
- Enhanced visible imaging.
- Recognition and identification performance.
- High resolution.
- Low power and cost.
- Ability to identify objects.
- Some ambient light is required. Not useful when there is essentially no light.
- Inferior daytime performance when compared to day light only methods.
- Possibility of blooming and damage while observing bright sources under low-light conditions.
THERMAL IMAGING (TI) SYSTEM
Based on the principal that all objects emit infrared energy as a function of their temperature. In general, the hotter an object is, the more radiation it emits. A thermal imager is a product that collects the infrared radiation from objects in the field and creates an electronic image. Thermal images are normally black and white in nature, where black objects are cold and white objects are hot. Some thermal cameras show images in color. This false color is an excellent way of better. Recent advancements in optics, detector technology and signal processing have enabled revolutionary advancement in the night vision technology leading to the realisation of third generation thermal imagers (TIs) having capabilities twice that of second generation and four times that of first generation systems.
The various technologies required for the development of TI systems are:
- System design and modelling
- IR optics with AR coating (dual and triple FOV, zoom)
- IR detector
- Signal and image processing
- Rugged displays
Detector converts IR radiation into electrical signal. IR detectors are categorised as photon and thermal detectors based on the principle they work.
- Cooler TI- is required to cool the photon detectors up to 7790 K to increase its sensitivity by reducing dark current. Most of the current TIs are based on the cooled detectors having Integrated Detector Dewar Cooler Assembly (IDDCA), which also includes proximity electronics. Cooled infrared detectors are typically housed in a vacuum-sealed case and cryogenically cooled. Without cooling, the detectors would be flooded by their own self-radiation.
- Uncooled TI - Third generation detectors operating at room temperature are also available. Though they do not require cooling but require temperature regulation of the focal plane within + 10 mk at room temperature. Unlike the cryogenically cooled detectors of cooled TI System, un-cooled infrared detectors operate at or near room temperature rather than being cooled to extremely low temperatures by bulky and expensive cryogenic coolers. When infrared radiation from night-time scenes are focused onto uncooled detectors, the heat absorbed causes changes to the electrical properties of the detector material. These changes are then compared to baseline values and a thermal image is created.
Challenges/Limitations with second presently held Gen- II & TI cooled devices
- Bulky, heavy & noisy.
- High power consumption.
- Single sensor.
- Not fully integrated.
- Weapon platform.
- Uncooled technology not mature enough.
The Indian Army has recently floated Request for Information (RFI) for Night Sight Image Intensifier and Thermal Imaging for Rifle AK-47. Additionally the RFI has been issued for Night Sight for 84MM Rocket Launcher (TI) and Night Sight for 7.62MM MAG 58 2A1 Medium Machine Gun (TI).
Commanders and detachment numbers at various levels in Indian Army need to be effectively night enabled. Due importance is therefore given to equip the weapons with mix of image intensifier and thermal imaging based night sights. Earlier also the RFI with similar requirement has been floated. At the same time the existing inventory of Small Arms including AK-47 rifles in service with the Indian Army do not have a Picatinny rail, which provides a standard mounting platforms, so vendors will have to modify the rifles to fit sights compatible with the rail. The quantity requirement for Thermal Imaging is 13000 numbers and Image Intensifier, 14000 numbers.
In the present electronic warfare scenario, where highly sophisticated, high resolution, broadband and multi-spectral imaging systems in visible, infrared and microwave have enhanced the lethality of all weapons systems, it has become necessary to provide better training tools for firing accuracy and testing of the weapons systems. By utilising especially designed thermal targets, as reference targets in place of cost prohibitive real targets, the firing accuracy and efficiency of any weapon system or equipment fitted with thermal imaging system can be verified especially in the long ranges. The systems/equipment can then be fine tuned for optimal performance in the sets of specified battlefield environmental conditions. In addition, the most vital issues pertaining to the training of the weapon operators for target identification in night-time using thermal sight can also be addressed/tested.