Optical lenses that darken on exposure to certain wavelengths of light
A photochromic eyeglass lens, part of the lens darkened after exposure to sunlight while the other part remained covered
A photochromic lens is an optical lens that darkens on exposure to light of sufficiently high frequency, most commonly ultraviolet (UV) radiation. In the absence of activating light, the lenses return to their clear state. Photochromic lenses may be made of polycarbonate, or another plastic. Glass lenses use visible light to darken. They are principally used in glasses that are dark in bright sunlight, but clear, or more rarely, lightly tinted in low ambient light conditions. They darken significantly within about a minute of exposure to bright light and take somewhat longer to clear. A range of clear and dark transmittances is available.
In one sort of technology, molecules of silver chloride or another silver halide are embedded in photochromic lenses. They are transparent to visible light without significant ultraviolet component, which is normal for artificial lighting. In another sort of technology, organic photochromic molecules, when exposed to ultraviolet (UV) rays as in direct sunlight, undergo a chemical process that causes them to change shape and absorb a significant percentage of the visible light, i.e., they darken. These processes are reversible; once the lens is removed from strong sources of UV rays the photochromic compounds return to their transparent state.
A photochromiclens is an optical lens that darkens on exposure to light of sufficiently high frequency, most commonly ultraviolet (UV) radiation. In the...
famous reversible photochromic applications is color changing lenses for sunglasses. The largest limitation in using photochromic technology is that...
flip-up glasses which feature a dark lens that can be flipped up when not in use (see below). Photochromiclenses gradually darken when exposed to ultraviolet...
must be for a minimum of one year. Contact lens Dioptre Eyeglass prescription Lorgnette Monocle Photochromiclens Pince-nez Visual acuity Keay L, Friedman...
high-quality flashlights use borosilicate glass for the lens. This increases light transmittance through the lens compared to plastics and lower-quality glass....
high refractive index is useful for lens making, since a given focal length can be achieved with a thinner lens. However, the dispersion must be corrected...
several of the individual uncoated lens elements of special-purpose lenses including the Zeiss 105 mm f/4.3 UV Sonnar, a lens formerly made for the Hasselblad...
700 BC, as do Assyrian lenses such as the Nimrud lens. The ancient Romans and Greeks filled glass spheres with water to make lenses. These practical developments...
Optical lens design is the process of designing a lens to meet a set of performance requirements and constraints, including cost and manufacturing limitations...
the glass. A concave lens of flint glass is commonly combined with a convex lens of crown glass to produce an achromatic doublet lens because of their compensating...
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