Ads
related to: polycarbonate corrective lens
Search results
Results from the WOW.Com Content Network
Modern glasses with a rectangular lens shape. Corrective lenses can be produced in many different shapes from a circular lens called a lens blank. Lens blanks are cut to fit the shape of the frame that will hold them. Frame styles vary and fashion trends change over time, resulting in a multitude of lens shapes.
Plastic lenses are lighter and shatter-resistant, but are more prone to scratching. Polycarbonate plastic lenses are the lightest, and are also almost shatterproof, making them good for impact protection. CR-39 is the most common plastic lens, due to low weight, high scratch resistance, and low transparency for ultraviolet and infrared radiation.
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.
A small amount of time is needed to adapt to the new lenses, usually 1–2 weeks. Corrective lenses can also be added to work masks or eyeglasses used in sports. Eyeglass lenses are commonly made from plastic, including CR-39 and polycarbonate. These materials reduce the danger of breakage and weigh less than glass lenses.
Focal length of lens varies with the color of light Photographic example showing a high quality lens (top) compared to a lower quality one exhibiting transverse chromatic aberration (seen as a blur and a rainbow edge in areas of contrast)
After many years as rivals, Essel and Silor merged on 1 January 1972 to form Essilor, then the world's third-largest ophthalmic optical firm. [1] Its first year of existence was marked by the creation of Valoptec, a non-trading company composed of stockholder managers who held half the company's capital stock, and the purchase of Benoist-Bethiot, a French lens manufacturer specializing in ...
Ads
related to: polycarbonate corrective lens