A novel night vision enhancement technology based on IR to visible light translation was demonstrated with a specifically designed liquid crystal cell sandwiched with pyroelectric and glass plates, which can be viewed by naked eyes.
Night vision involves the techniques which enable us to see objects in the dark. Night vision is not possible for human eyes because the rods and cones in the human eyes are not sensitive to infrared spectrum of the light. This draw back of the human eye can be overcome by the use of special instruments and techniques commonly called as the “Night Vision Techniques”. Such night vision techniques find a great deal of applications in the military field. Night vision techniques are used in the military field to identify enemy soldiers in the dark. The methods used to view an object in the dark are
The optical sensors within the human eye require a minimum intensity of light to get activated. This inability to view in the dim light can be overcome by the method of Image Enhancement. In this method, the tiny amounts of light present are collected including the lower portion of the infrared light spectrum that is imperceptible for the human eyes. These light collected are then amplified into suitable levels that are visible for the human eyes. This method requires a small amount of light to be reflected from the object so that they could be visible.
The thermal imaging techniques are the most advanced and complicated system used for night vision. These techniques operate by capturing the upper portion of the infrared light spectrum, which is emitted as heat by objects instead of simply reflected as light. It involves the use of a thermal camera that could capture thermal radiation from hot bodies and identification of these bodies is based on the fact that hot bodies emit more thermal radiations than cold bodies.Paper Presented By Zhang, J.W.; Guo, X.; Fan, L.; Zou, Y.K.; Craley, J.; Boston Appl. Technol., Inc., Woburn, MA, USA
Warm bodies like stars or human body emits LWIR and MWIR beams which can be focused by an IR lens onto an IR viewer. An OPTO CERAMIC (OC) plate has strong absorption in these wavebands; the IR energy is converted into heat within a thin layer of the OC plate, raising the temperature of the OC plate and, consequently, the pyro electric field. When another collimated polarized visible beam falls on the plate, the transmitted light of the incident beam can be modulated by the pyro electric effect. . Pyro electricity, the release of charge due to a material’s change of temperature, occurs in all materials which belong to the polar crystal symmetry class. Consequently, the variation of the thermal radiation is transferred into the variation of the visible signal emerging on the exit surface. Because the OC plate has only a slight absorption in the visible waveband, so the influence of the visible reading beam temperature change is negligible.
Polar dielectrics have long been of interest for electronic applications Liquid crystal (LC) materials have application in low voltage operation and low power consumption. The technologies of LC displays have been long matured and are in many aspects of our daily living. With a bias voltage applied, an operation range of < 0.5 to 1 V is easy to reach in a twist LC cell. It is important to mention that a super twisted cell can lower the operation voltage even further, to 0.06 V. Combining pyro electric effect and super twisted LC display technique, a novel night vision enhancement technology based on IR to visible light translation can be made.
This paper appears in: Lasers and Electro-Optics, 2009 and 2009 Conference on Quantum electronics and Laser Science Conference. CLEO/QELS 2009.