The present invention relates generally to devices and methods for measuring haze and transmissivity in transparencies, and more particularly to a device and method for measuring haze and transmissivity of aircraft transparencies as viewed through night vision goggles.
Night vision goggles (NVGs) are being used by aircrew members with increasing frequency during nighttime flight and ground operations. Concurrently, aircraft transparencies are constantly undergoing improvements in materials such as acrylic to polycarbonate and their surfaces are being treated with gold, indium-tin-oxide or other coatings. Ground vehicles are being equipped with bullet-resistant glass which may be fabricated using a combination of specially treated plastic and glass materials. These material changes may attenuate the infrared (IR) energy utilized by NVGs thereby degrading the visual acuity of the aircrew member. Aircrew members have informally reported lowered visual performance while using NVGs in some aircraft equipped with coated canopy systems. Traditional transmissivity and haze measurements made in the visible spectral region (400-700 nm) cannot characterize the entire problem. Preliminary laboratory measurements of sample coated canopies found that IR transmissivities of windscreen coatings varied considerably among manufacturers thereby affecting observer performance (see, Pinkus et al, "The Effects of Aircraft Transparencies on Night Vision Goggle-Mediated Visual Acuity," SAFE Symposium Proceedings (1997) pp 93-104). However, NVG-mediated visual performance through canopies is not solely affected by IR attenuation, but also by haze resulting from scatter of incident light.
The invention solves or substantially reduces in critical importance problems in the prior art by providing a portable device and method for measuring transmissivity and haze of aircraft transparencies as viewed through NVGs. The invention includes a pair of light sources for projecting a transmitted beam and a haze producing beam onto a transparency and sensor portion including a light intensifier tube of an NVG and photometer for measuring the luminance output thereof in order to quantify the NVG weighted attenuation (transmissivity) and haze (light scatter) characteristics of the transparency.
The invention finds utility for measuring the IR transmissivity and IR haze characteristics of transparencies important in selection of coating materials (gold, indium-tin-oxide) for use with NVGs, quality control of the coatings within and among transparency manufacturers, quick-response field evaluations of transparency and NVG integration issues, life-cycle costs of coatings, monitoring deleterious environmental effects (acid rain, sand abrasion, bio-chemical) on coating integrity, maintenance procedures, and visual performance of an NVG-equipped aircrew member.
It is therefore a principal object of the invention to provide system and method for measuring transmissivity and haze in a transparency.
It is a further object of the invention to provide system and method for measuring infrared transmissivity and haze in a transparency as viewed using night vision goggles.
It is another object of the invention to provide system and method for measuring the effect of using night vision goggles on the observed infrared transmissivity and haze in a transparency.
It is another object of the invention to provide a device and method for field evaluation of transparencies.
It is yet another object of the invention to provide an improved system and method for measuring transmissivity and haze in aircraft transparencies.
It is yet another object of the invention to provide a reliable portable transmissivity and haze measurement device.
These and other objects of the invention will become apparent as a detailed description of representative embodiments proceeds.