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A 1951 USAF resolution test chart is a microscopic optical resolution test device originally defined by the U.S. Air Force MIL-STD-150A standard of 1951. The design provides numerous small target shapes exhibiting a stepped assortment of precise spatial frequency specimens.
The template for rimless eyeglasses date back to the 1820s, when an Austrian inventor named Johann Friedrich Voigtländer [] marketed a rimless monocle. [2] The design as it is known today arose in the 1880s [3] as a means to alleviate the combined weight of metal frames with heavy glass lenses.
Glass thicknesses typically range from 1.8 to 2.5 millimetres (0.071 to 0.098 in). Clear glass has light transmission of approximately 90%, absorption of approximately 2%, and reflection of approximately 8%. Whereas absorption can be reduced by using low-iron glass, reflection can only be reduced by an anti-reflective surface treatment.
Silhouette manufactures and distributes rimless eyewear, full rim eyewear and sunglasses as well as lenses. [21] For many years, Silhouette was a licensed manufacturer of sports eyewear for Adidas and Swarowski. [22] Silhouette currently produces eyewear under three brands: Silhouette, NEUBAU EYEWEAR and evil eye. [18]
Man with glasses. A woman with glasses. Glasses, also known as eyeglasses or spectacles, are vision eyewear with clear or tinted lenses mounted in a frame that holds them in front of a person's eyes, typically utilizing a bridge over the nose and hinged arms, known as temples or temple pieces, that rest over the ears for support.
At the same time, sunglasses started to be used as aids for pilots and even produced for the gaining aviation sector, eventually adding to sunglasses as cultural icons and to their popularity. Polarized sunglasses first became available in 1936 when Edwin H. Land began experimenting with making lenses with his patented Polaroid filter. In 1947 ...