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Science Popularization

National Technology Day - 2015 Celebration at UCOST VIGYAN DHAM

Dr. S.S Negi, Outstanding Scientist (Director),IRDE, Dehradun delivered lecture on "Military application of Electro Thermal Imaging optics". He detailed the how the technology can improve the military appliances. Dr. Negi, discussed the Research and development of IRDE and their role in the military. He further elaborates the difficulties of military during war due to lack of technologies. He further emphasized on role of thermal imaging in various military appliances. He detailed the various technologies developed by IRDE, of thermal imaging and their role during combating the force. He elaborate a night vision device, lesser technology etc. He detailed the night vision camera. Dr. Negi also highlighted the advantage of Night Vision Cameras during Military operations. The human eye is a very sensitive and versatile image detector but has a number of physical limitations. An electronic image intensifier can provide a fundamental improvement and perception gain over the unaided eye by capturing more photons from the scene and using these more efficiently. More photons are collected by employing an objective lens of larger diameter than that of the pupil of the dark-adapted eye. The only limitations in this respect are the practical considerations of size and weight of the instrument depending upon the application. The co11ected photons can be used more efficiently by detecting them with higher quantum efficiency than that of the retina. The most suitable type of detector for this purpose appears to be a photoemissive cathode consisting of a compound of the alkali metals: sodium, potassium and caesium with antimony. Surfaces of this kind have quantum efficiencies of upto about 20% for white light and can make much more efficient use of the night-sky radiation than the retina. On the other hand, an increased integration time beyond the 0.2 second of the fully dark adapted eye is only of limited use in practical applications because it reduces the ability to detect moving objects which appear to become more as and more blurred. It is thus possible in principle to obtain considerable improvement in perception over the dark adapted eye by employing an instrument with a large diameter of its objective lens and an efficient photocathode. However, this potential perception gain can be achieved in practice only if the detected photons in the form of emitted photoelectrons produce scintillations on a final viewing screen that are bright enough to be registered on the observer's retina. This condition leads to the requirement of a minimum amount of light amplification or lumen gain in the instrument. Such a lumen gain can be achieved with the aid of image-intensifier tube. Much research has been done, especially in the fields of electronic image intensifier tubes, as well as optical technology relating to the optical components of a night vision system (i.e. the objective lens and the magnifying eyepiece) with a view to making the performance these night vision devices better and better.

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Glimpse of the Session
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