Sterling Precision Optics, Inc. is an industry leader for the supply of NVG filters to the Night Vision Industry; Sterling offers a wide range of monolithic glass Night Vision Filters which meet the U.S. Military specification MIL-STD-3009. Sterling also offers NVG Filters for the new and expanding Light Emitting Diode (LED) technology which is being adopted for military and aerospace applications. The new NVG Filter Glass meets MIL-STD-3009 at a reduced weight through decreased thickness of the filter.
Night vision, also known as image intensification, allows humans to see in low to zero light conditions. Night vision is made possible by a combination of two approaches; sufficient spectral range, and sufficient intensity range. A device (NVD) works by collecting photons through a lens (NVIS). Then they pass through a photocathode which converts the photons into electrons. These electrons then pass through a microchannel plate, consisting of millions of closely spaced channels. In here the electrons can hit the walls so they will release thousands of additional electrons. Finally, the multiplied electrons will hit a phosphor screen where they get turned back into light. This light is thousands of times brighter than the original light and is in the visual spectrum of the human eye. The intensified light is in the same orientation as it came in providing a clear view of objects in the dark.
Night vision has many uses. The original use was for military operations. NVDs are now used in security, police work and amateur work. Night vision goggles are especially useful for rescue helicopter pilots because they work even when there are bright light behind them. NVDs work in the near-infrared band at a wavelength of one micrometer. Humans can see between 0.4 and 0.7 micrometers. NVDs work by capturing ambient light usually from the moon and stars. It only takes one star in the sky for an NVD to work.
Night vision can work in one of two ways, active and passive. Passive systems amplify the existing light and active systems rely on an infrared light source. Early NVDs were designed to be used as active systems, as they did not have the sensitivity to operate on ambient light. Active systems are commonly used today in closed-circuit television security and on many home video cameras. The military uses passive NVDs over active because infrared illumination is easily spotted and tracked by others equipped with it. Modern NVDs are equipped with infrared illuminator for when there is no ambient light.
Sterling uses CNC Milling Centers and High Speed Polishers to produce their NVIS Filters. Machined glass filters provide superior performance and durability verses plastic filters. Glass filters have markedly better transmittance, radiance and chromaticity characteristics when compared to plastic filters. Sterling produces a variety of filter styles: Ring Filters, Flat Filters, AR Coated Filters, and Odd Shaped Filters. Surfaces can be highly polished or diffused.