Nanostructured High Performance, High Angle of Incidence Anti-Reflection (AR) Treatment

Telescope optical sights on warfighter rifles need to be small in size, light in weight, have high optical transmission over a wide spectral range for day and night vision, and perhaps most importantly, exhibit a low visible and near infrared signature. The highly observable flash of light, or glint, reflected from common telescope sights readily betrays the position of even the most skillfully camouflaged soldier. Glint can be particularly severe at night where infrared light reflections are large relative to the environmental backdrop. The wide spectral range and large angle of incidence that gives rise to glint are an ongoing problem for the conventional anti-reflection (AR) technology based on coating multiple thin-film material layers on telescope lenses. Thin-film AR coatings function through the interference of light reflected from each material layer, an effect that varies with the light incident angle, wavelength, and polarization state. An innovative, rugged, single material solution to the glint problem without the practical limitations of thin-film AR coatings is based on surface relief microstructures fabricated directly in the telescope optic material. Such stealthy textures, first evolved in nature in the eyes of night moths and known as"Motheye"by the optics industry, provide a smooth gradation of the lens-air interface, allowing light to propagate without reflection over a wide wavelength and incident angle range. Theoretical models for arrays of AR microstructures (ARMs) predict that such textures can be significantly more effective than thin-film coatings at suppressing reflections out to angles of incidence of 60 degrees and beyond. Recent reflection measurements of ARMs textures fabricated in quartz, fused silica, and glass show that reflected light can be reduced to a level below 0.1% over a huge spectral range spanning the near ultraviolet, visible, and near infrared. With strong interest from ARMY contractors such as Trijicon, Raytheon and Boeing, TelAztec will demonstrate its custom design, broad-band high-angle ARMs textures in several glasses that meet the requirements of military optical sights. ARMs textures on the scale and curvature of telescope lenses will be demonstrated in a Phase I Option effort, and the manufacturing process for producing low cost ARMs textures in existing and future rifle scope optics will be optimized during the Phase II effort and into the Phase III commercialization period.