Sunglasses: Originally Invented to Reduce Distracting Glare

Only available on StudyMode
  • Download(s) : 161
  • Published : January 10, 2013
Open Document
Text Preview
Sunglasses are eyewear designed to help protect the eyes from excessive sunlight. Eyes are extremely light sensitive and can be easily damaged by overexposure to radiation in the visible and nonvisible spectra. Bright sunlight can be merely a distracting annoyance, but extended exposure can cause soreness, headaches, or even permanent damage to the lens, retina, and cornea. Short term effects of sun overexposure include a temporary reduction in vision, known as snow blindness or welders' flash. Long-term effects include cataracts and loss of night vision. In both cases, the damage is caused by ultraviolet (UV) light, which literally burns the surface of the cornea. Sunglasses were originally invented to reduce distracting glare and allow more comfortable viewing in bright light. Early sunglasses were simply tinted glass or plastic lenses that were primarily meant to reduce brightness. Darker lenses were considered to be better because they screened out more light. As our understanding of the damaging nature of sunlight evolved, the need for better eye protection was recognized, and technology was developed to help sunglasses better screen out the harmful rays of the sun, especially UV rays. From inexpensive models with plastic lens and frames to costly designer brands with ground glass lenses and custom-made frames, sunglasses are available in a staggering array of styles and prices. Unfortunately there is no way to tell from the color or darkness of the lens how well it will screen out UV light. Similarly, there is little relationship between price of glasses and their ability to block UV light. Raw Materials

Sunglasses consist of a pair of light-filtering lenses and a frame to hold them in place. The vast majority of lenses are made of colorized plastic, such as polycarbonate. However, glass is still employed for high quality brands. The highest quality lenses are optically accurate and do not distort shapes and lines. These lenses, like camera lenses, are made from distortion-free ground and polished optical glass. The borosilicate glass used in these lenses is scratch resistant and is made impact resistant by tempering it with various chemical treatments. Soluble organic dyes and metallic oxide pigments are added to the lens material to absorb or reflect light of certain frequencies. These additives must not distort colors excessively, however; for example, badly colored lenses may make it difficult to discern the correct color of traffic lights. Gray lenses produce the least distortion for most people, although amber and brown are good too. Blue and purple tend to distort too much color. The additives also should block at least part of the blue light which is part of the lower frequency UV rays. Brown or amber screen out blue light the best, but at the cost of some color distortion. Various chemical coatings which are added to the lens can enhance viewing by reducing reflection or screening out polarized light. Sunglass frames are made from metal or plastic. Metal frames, particularly expensive ones, are often made of mixtures of nickel and other metals such as silver. These frames have precisely engineered features, such as sculpted and gimbaled nose-pads, durable hinges with self-locking screws, and flexible temples. Upscale manufacturers

use combinations of nickel, silver, stainless steel, graphite, and nylon in their leading-edge designs. Design
There are two key elements to consider regarding sunglasses design, fashion and function. In the last few decades sunglasses have become a high fashion item, and the current design process reflects this status. Upscale clothing designers, fragrance marketers, and sporting goods vendors custom-design sunglasses to promote their own specific image. By and large these design changes are not functional; they are intended to increase the fashion appeal of the glasses. Stylized frames, uniquely shaped lenses, and embossed logos are all part of this designer mystique....
tracking img