BEL: to the core of Electro Optics
Night Vision Devices ( NVDs) function by collecting tiny amounts of light, imperceptible to the human eye and amplifying it to a point we can easily see an image. NVDs gather ambient reflected light which emanates when starlight or moonlight falls on an object. The front lens receives the reflected light made of photons and sends it into an Image Intensifier Tube (II Tube). The light first falls on the photocathode tube that changes the photons into electrons. The electrons are then passed through a Micro Channel Plate (MCP), wherein their numbers are amplified through an electrical and chemical process. The electrons are then impinged against a phosphorus screen that changes the amplified electrons back into visible light (image), which is seen through the eyepiece. The image will be seen as a clear, green-hued, amplified, re-creation of the scene being observed.
The Night Vision and Electronic Sensors Directorate of the US Army has classified image intensifiers as Gen I, Gen II, Gen III, etc, based on the changes happening in manufacturing technologies. Generation I had a low gain and no MCP. Image intensifiers with MCP were subsequently developed and called Generation II. Both these had the Photo Cathode made of multi alkali material. Next came the image intensifiers which used GaAs as cathode material and a filmy layer coating on MCP, termed as Generation III. The definition of Generation IV would be an unfilmed MCP in the image intensifier. These are all technical issues, they tell how image intensifiers are produced, but not how they perform.
Innovations in photocathode technology have significantly reduced the tube’s noise and increased the signal to noise ratio which is the undisputed characteristic to describe the low light level performance of an Image Intensifier Tube. The US government has recognised the fact that technology employed by different manufacturers varies, and itself makes little difference as long as an operator can see clearly at night.
The generation number identifies only y how an image intensifier is manufactured. It does not say anything about the performance of a tube. By 2001, the United States federal government concluded that a tube’s ‘generation’ was not a determining factor of a tube’s global performance, and therefore the term was eliminated as a basis of export regulations. Consequently, the United States has based its export regulations not on the generation, but on a calculated factor called figure of merit (FOM). FOM is an abstract measure of image intensifier performance, derived from the number of line pairs per millimetre (resolution) multiplied by the tube’s signal-to-noise ratio.
In India, there still is fascination about the generation of an Image Intensifier Tube. But one should realise that a reference to generation is nothing more than a marketing tool. Generation is not an assurance of performance or quality, according to M V Raja Sekhar, CTO (Electro Optics & Lasers), BEL.
Photonis, a world leader in night vision technologies, classifies its image intensifiers as Super Gen, Hyper Gen, XD- 4, XR-5, etc, based on FOM. Night vision products of Photonis are in use at various NATO affiliates and are largely deployed worldwide.
The Indian Army has well understood the importance of FOM and all its recentlycently released Request for Information tion (RFI)/ Request for Proposals (RFP) for Night Vision Devices specifically mentionention the required FOM.
BEL Optronic Devices Ltd (BELOP), formerly BEL DELFT,T, a fully owned subsidiary of BEL startedarted manufacturing of 2nd Generation ation Image Intensifiers in collaborationon with and as a Joint Venture with BV V DELFT Netherlands in 1994, as directed ed by the Ministry of Defence. This was aimed at having indigenous capability pability in In India for such critical technologies. s. Subsequently,Sub the technology was upgradedd to Super Generation and Hyper Generation grade with in-house developments.
In 2012, the plant was upgraded to produce XD- 4 II Tubes with technical know- how from Photonis, France, and about 40,000 tubes were supplied. The plant is presently being upgraded to XR-5 grade with capacity to produce more than 30,000 Image Intensifier Tubes per year. BEL also has plans to produce MCP indigenously with ToT from Photonis once the XR-5 is fully established.
The plant set up by BELOP is a stateof-the-art facility with a huge investment exceeding Rs 500 crores built on a total area of 13,608 sq mt and the built- up area of 8,650 sq mt. It has a workforce of about 130 permanent employees besides contract staff. There are more than 200 processes involved in the manufacture of XR- 5 Image Intensifier Tubes and are controlled and monitored by highly qualified and competent engineers. BELOP has also established advanced test facilities to ensure quality and reliability of the II Tubes. BELOP is ISO 9001:2008 certified. India today is one of the few countries in the world possessing this highly guarded technology.gy