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Photochromism was discovered in the late 1880s, including work by Markwald, who studied the reversible change of color of 2,3,4,4-tetrachloronaphthalen-1(4H)-one in the solid state. He labeled this phenomenon "phototropy", and this name was used until the 1950s when Yehuda Hirshberg , of the Weizmann Institute of Science in Israel proposed the ...
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.
A gradient-index lens with a parabolic variation of refractive index (n) with radial distance (x).The lens focuses light in the same way as a conventional lens. Gradient-index (GRIN) optics is the branch of optics covering optical effects produced by a gradient of the refractive index of a material.
Progressive lenses are corrective lenses used in eyeglasses to correct presbyopia and other disorders of accommodation. They are characterised by a gradient of increasing lens power , added to the wearer's correction for the other refractive errors .
Uncoated glasses lens (top) versus lens with anti-reflective coating. The reflection from the coated lens is tinted because the coating works better at some wavelengths than others. An antireflective , antiglare or anti-reflection ( AR ) coating is a type of optical coating applied to the surface of lenses , other optical elements, and ...
The lens front can then reform its shape between the suspensory ligaments in a similar way to a slack chain hanging between two poles might change its curve when the poles are moved closer together. This model requires precise fluid movement of the lens front only rather than trying to change the shape of the lens as a whole.
Cranberry glass bowl Photochromic eyeglass lens. The coloring is caused by silver nanoparticles. Selenium, like manganese, can be used in small concentrations to decolorize glass, or in higher concentrations to impart a reddish color, caused by selenium nanoparticles dispersed in glass. It is a very important agent to make pink and red glass.
Some colored contact lenses completely cover the iris, thus dramatically changing eye color. Other colored contact lenses merely tint the iris, highlighting its natural color. A new trend in Japan, South Korea and China is the circle contact lens, which extend the appearance of the iris onto the sclera by having a dark tinted area all around ...