Sunglasses or sun glasses are a form of protective eyewear designed primarily to prevent bright sunlight and high-energy visible light from damaging or discomforting the eyes. They can sometimes also function as a visual aid, as variously termed spectacles or glasses exist, featuring lenses that are colored, polarized or darkened. In the early 20th century, they were also known as sun cheaters ( cheaters being an American slang term for glasses) .[1]
The American Optometric Association recommends sunglasses whenever a person is in the sun.[2] to protect the eyes from ultraviolet radiation ( UV) and blue light, which can cause several serious eye problems. Its usage is mandatory immediately after some surgical procedures, such as LASIK, and recommended for a certain time period in dusty areas, when leaving the house and in front of a TV screen or computer monitor after LASEK. Sunglasses have long been associated with celebrities and film actors primarily from a desire to mask their identity. Since the 1940s, sunglasses have been popular as a fashion accessory, especially on the beach.Glasses, also known as eyeglasses or spectacles, are devices consisting of lenses mounted in a frame that holds them in front of a person’s eyes. Glasses are typically used for vision correction. Safety glasses provide eye protection against flying debris or against visible and near-visible light or radiation. Sunglasses allow better vision in bright daylight, and may protect one’s eyes against damage from high levels of ultraviolet light. Specialized glasses may be used for viewing specific visual information ( such as stereoscopy) . Sometimes glasses are worn simply for aesthetic or fashion purposes. The number of Americans who are nearsighted has doubled since the 1970s and almost 3/4 of the US population wears glasses. People are more likely to need glasses the older they get with 93% of people between the age of 65-75 wearing corrective lenses.[1][2]
But now that many others who spend time outdoors have discovered the benefits of polarized lenses, interest in these types of sunglasses has soared.
Besides boaters, outdoor enthusiasts who benefit the most from polarized sunglasses include skiers, bikers, golfers and joggers, all who may enjoy a clearer view along with elimination of glare.
These sunglasses can be used for driving and, in fact, can reduce glare from a long, flat surface such as the hood of the car or the road’s surface.
Polarized sunglasses also can be worn indoors by light-sensitive people, including post-cataract surgery patients and those continually exposed to bright light through window
Light reflected from surfaces such as a flat road or smooth water generally is horizontally polarized. This means that, instead of light being scattered in all directions in more usual ways, reflected light generally travels in a more horizontally oriented direction. This creates an annoying and sometimes dangerous intensity of light that we experience as glare.addition, polarized lenses may reduce the visibility of images produced by liquid crystal displays ( LCDs) or light-emitting diode displays ( LEDs) found on the dashboards of some cars or in other places such as the digital screens on automatic teller machines and self-service gas pumps.
With polarized lenses, you also may be unable to see your cell phone or GPS device.
Boaters and pilots also have reported similar problems when viewing LCD displays on instrument panels, which can be a crucial issue when it comes to making split-second decisions based strictly on information displayed on a panel. ( Some manufacturers of these devices have changed their products to solve the problem, but many have not yet done so.)
However, for most other sports and activities, polarized sunglasses offer great advantages. And today, many polarized lenses are available in combination with other features that can enhance outdoor experiences.
Mirrored sunglasses are sunglasses with a reflective optical coating ( called a mirror coating or flash coating) on the outside of the lenses to make them appear like small mirrors. The lenses typically give the wearer’s vision a brown or grey tint. The mirror coating decreases the amount of light passing through the tinted lens by a further 10–60% , making it especially useful for conditions of sand, water, snow, and higher altitudes. Mirrored sunglasses are one-way mirrors.[citation needed]
The color of the mirror coating is independent of the tint of the lenses. It is determined by the thickness and structure of the layer.
Their popularity with police officers in the United States has earned them the nickname cop shades. The two most popular styles for these are dual lenses set in metal frames ( which are often confused with Aviators) , and Wraparound ( a single, smooth, semi-circular lens that covers both eyes and much of the same area of the face covered by protective goggles, combined with a minimal plastic frame and single piece of plastic serving as a nosepad) . Wraparound sunglasses are also quite popular in the world of extreme sports.
The simplest version of a mirror coating is a single layer of a deposited thin film of a suitable metal, usually prepared by ion beam deposition, sputter deposition or vapor deposition. However, this kind of coating is very prone to scratching, and degrades, especially in a corrosive environment like salt water.
More modern reflective coatings usually have several alternating layers of specific thickness, made of dielectric materials and sometimes metals. The metal layer can be made from titanium, nickel or chromium, or from an alloy like Nichrome or Inconel, and has thickness ranging from 0.5 to 9 nanometers. The dielectric layer comprises a suitable oxide, e.g. chromium oxide, silicon dioxide, or titanium dioxide; its thickness determines the reflective properties of the resulting dielectric mirror. The manufacturing process is similar to making anti-reflective coating, and mirror and antireflective coatings can be deposited in the same sequence of operations.
The Cyberpop band Information Society released a track titled Mirrorshades on their casually post apocalyptic themed album HACK, released in 1990.
Characters in cyberpunk frequently wear mirrorshades, and they are considered a hallmark of the subculture. Mirrorshades: The Cyberpunk Anthology takes its name from them.
Many characters in the cyber thriller movie series, The Matrix exclusively wear mirrored sunglasses, Morpheus in particular. Another popular icon, especially in the 60s, was the character ’the man with no eyes’ from the movie