Dontech’s night vision filters are primarily used by manufacturers of military electronic display and vehicle lighting applications. Night vision goggles (NVG) or night vision imaging systems (NVIS) must be used in an environment that will not have interference from near infrared (NIR) noise, resulting in sensitivity problems for the NVGs. Furthermore, night vision compatibility (NVC) is only achieved when the design of the lighting system or display allows for proper use with and without the NVIS, at night and in daylight.
Dontech provides filters compliant with MIL-STD-3009 for use in Classes A, B, and C NVIS requirements. These products can be used in Type I Direct View Image NVIS and Type II Projected Image NVIS (e.g., Cat’s Eyes) environments. For manufacturers of aircraft lighting and display equipment, Dontech’s filters for night vision compatibility include:
Night vision filters can be incorporated in front of any display, membrane switch, or light source, or into the backlight assembly, light guides, or sources of an LCD. Full color NIR reflecting filters can only be used in the backlighting system due to photopic and off-angle reflections and color shift. Specific NVIS MIL-STD-3009 compliant and custom-colored filters can be selected based on light source (e.g., LED or incandescent), transmission, and NIR rejection requirements. Dontech can apply antireflection and optical EMI/RFI shielding (conductive coatings & conductive optical grids), and heaters for additional night vision system display enhancement.
NVIS are systems, typically helmet mounted binocular image intensification devices, that have a very high sensitivity to radiation in the approximate region of 600nm to 930nm (orange to near infrared). The NVIS works by converting photons from ambient nighttime light into a micro-displayed visible image. The NVIS will amplify the nighttime image approximately 2,000 times. To protect the image intensifier assembly, the systems are equipped with an automatic gain control which will aperture down the NVIS when exposed to bright lights in the region of approximately 600nm to 930nm. If displays or light sources in the proximity of the goggles are not properly filtered, the automatic gain control (AGC) will activate and the NVIS will “bloom” and become proportionally less sensitive to nighttime objects outside of the cockpit. The NVIS are not used to read the cockpit displays (except the original AN/PVS-5), therefore the filtered displays must be visible to the unaided eye.
Avionic NVIS filtering requirements are more demanding than ground-based systems. NVC in a cockpit requires little to no overlap between the emissions spectrum of the display or light source and the spectral response of the NVIS. The filtering of commercial light sources and displays is accomplished using near infrared absorbing glass, thermoplastic substrates which absorb NIR radiation, or thin film coatings that simultaneously reflect NIR radiation and transmit visible light. These filters are designed to absorb or reflect in the deep red and NIR. Often the chromaticity of the lighting system display must be adjusted, which can be accomplished along with the NIR filtering. By significantly reducing NIR radiation, night vision goggles can be used along with electronic display and lighting systems without affecting the nighttime sensitivity of the NVIS. Secondary filtering operations such as EMI/RFI shielding, antiglare/antireflective coatings, or contrast enhancement can be added to the night vision filters.
MIL-STD-3009 specifies the interface and performance requirements for avionic lighting and display equipment that is intended to be used along with NVIS. This specification defines aircraft interior lighting standards for sources including cockpit displays and caution / warning lights in both day and nighttime operating conditions. Avionic NVIS filters must incorporate NIR attenuation properties, chromaticity, contrast for daylight readability, and often EMI/RFI shielding. This standard also includes provisions for white light sources and for “leaky green” requirements.
Dontech has extensive engineering and technical support resources that can assist with your night vision compatible filter design needs. Our technical staff have diverse backgrounds relevant to high-performance display and precision optics markets. For many of our top customers, we function as an extension of their engineering departments, supporting projects from concept to final system delivery. We will integrate our optical filters and other enhancing components into touchscreens, displays, and systems to the level that is needed by our customers.