Sunglasses are for protective eye wear that keeps the eye safe from the damaging glare of the sun and harmful UV rays. There are many types of sunglasses that are available today with the lenses offering varying degrees of protection from the sun. This is not only when you go to the beach, in some specific cases sunglasses have a crucial role to play. After eye surgery doctors recommend that sunglasses should be worn during waking hours not only to ward off the glare of the sun but also to prevent dust and dirt from entering the eyes. Further, sunglasses are on top of the heap as a fashion accessory and are frequently seen at fashion shows on models walking the ramp.
The history of sunglasses can be traced back to the 1920s, especially among movie stars, not merely to mask their identity from drooling fans but also to protect their eyes from the glare of arc lamps. Cheap and mass produced sunglasses made from celluloid was first made by Sam Foster in 1929. It caught on like a house on fire and within 5 years, about 20 million sunglasses were sold in the USA alone in 1937. Polaroid sunglasses that adjusts the depth of shade as per lighting conditions was invented by Edwin H. Land in 1936 with lenses made from patented Polaroid filter.
In modern times, sunglasses have become a vital cog in the fashion world. High-end sunglasses are crafted by the leading fashion designers of the world and their unveiling is as much an anticipated event as their regular clothes collections.
Apart from being a fashion statement, sunglasses are also manufactured for special purposes. Sunglasses for fighter pilots and sunglasses for mountaineers are some of them. These glasses reduce the impact and glare of the sunlight without in any way lowering the extent of visibility and clarity of the surrounding landscapes.
However, a word here will be relevant about Polaroid sunglasses as they have a special manufacturing process unlike regular sunglasses. Visible light from the sun gets scattered when it meets a horizontal service. This produces a white glare which affects the human eye and reduces visibility. By using a sheet of vertical polarizing material the properties of the horizontally polarized component can be considerably reduced. This improves contrast and perception of the surroundings.
Polarized eye wear uses press-polishing for manufacturing polarized lenses. Press-polishing produces lenses that are thicker at the centre and tapered at the edges.
Sunglasses have to conform to international standard for sunglasses which is ISO 12312. Part 1 specifies the physical and optical characteristics of glasses and Part 2 lays down the tests to validate Part 1.
Incidentally, Australia has been the first country in the world to set down national standards for eye glasses in 1971.