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How Sunglasses Work

by John M. White |

Today sunglasses manufacturers use basically two different mediums to make sunglasses: glass or polycarbonate lens pucks. Glass lenses is used in high quality sunglasses while polycarbonate lenses are used in less expensive sunglasses. The first step in understanding how sunglasses work is to recognize the importance of sunglasses in protecting your most important sensory asset: your eyes!

Lens Construction

[caption id="attachment_1650" align="alignright" width="325"]An example of coatings placed on sunglasses lenses An example of coatings placed on sunglasses lenses[/caption] Once the lens puck has been manufactured it is then placed into a curve generator to grind out the lens according to the manufacturer's specifications. The lenses are then coated with a variety of wafer like sheets that have a number of different properties. For example the lens will normally have the following layers placed on it:
  • An anti-reflective back: this is a layer placed on the lens's back to protect your eye from the glare of light behind you;
  • A tinting layer: various lens tint choices are available; however the very best sunglasses tint is gray because is is best for viewing true colors;
  • A UV coating: this is perhaps one of the most important layers as it will filter our UVA and UVB ultraviolet radiation preventing them from reaching your eyes;
  • Another anti-reflective coating: this coating is placed on the front of the sunglasses lens to reduce glare and in some cases to even repel water;
  • A scratch-resistant coating: this coating is usually made from ultrathin Teflon polymer which is a durable type of plastic that prevents scratches on the surface of the lens;
  • A polarizing filter: if you spend a great deal of time on the water, snow fields or the desert than polarized sunglasses are a necessity for you.

Glare Reduction

How sunglasses work to reduce glare from entering your eyes and causing you to be distracted is by placing anti-reflective coatings on both the front and back of the sunglasses lens. This coating is different and separate from other coatings like lens tint etc. Glare comes from many different places and is usually temporary in nature as you move. High end sunglasses will have both of these coatings on them; however, there are no industry standard requirements for manufacturers regarding these anti-reflective coatings, and inexpensive sunglasses will likely not have them because of the additional manufacturing costs associated.

Sunglasses Lens Tints

Sunglasses manufacturers can tint sunglasses lens with any color imaginable; however when it comes to understanding how sunglasses work you need to consider what your goal is in purchasing a pair of sunglasses. Generally speaking sunglasses with sunglasses tints like reds, blues, etc. may provide you with a great fashion statement; however those tints may not provide much in the way of visual acuity for seeing things clearly. Gray lenses are always the best choice in lens tint because they allow the truest colors to pass through the lens and reach your eyes. But sometimes you need more than one pair of sunglasses because tan or yellow lens tints work best for overcast lighting conditions. Lens tint or darkness has nothing to do with how well your sunglasses protect your eyes from ultraviolet radiation, another thing to think about when considering how sunglasses work.

Ultraviolet Radiation

As stated above the darkness or tint of your sunglasses lens has nothing to do with protecting your eyes from ultraviolet radiation. Ultraviolet radiation rays, or UV rays, are very dangerous for your eyes. If these UV rays reach your eyes they can cause damage to your eyes and even cause disease in your eyes. The UV coating is the most important coating to be put on your sunglasses lenses and the most important consideration when thinking about how sunglasses work. Without the UV coating your eyes may be at serious risk.

Scratch Resistant Coatings

Because sunglasses lenses are transparent all of the features of sunglasses are coatings placed onto the sunglasses lenses. These coatings are very thin and subject to scratching if touched by your hand or a polishing cloth of some kind. To prevent this scratching a film of diamond-like carbon film is applied to the lens and through the process of ionization a thin, durable film is created on the surface of the lens to resist scratching.

Polarization

[caption id="attachment_1654" align="alignleft" width="300"]How polarized lenses work How polarized lenses work[/caption] Light waves from the sun vibrate and radiate outwards in all directions. Whether the light waves are reflected, scattered or refracted whenever the vibrations are aligned into one or more planes of direction the light is said to be polarized. An example of natural polarization is when you see the reflected glare off the surface of a lake. Most of the glare that causes problems comes from horizontal surfaces, and is therefore horizontally polarized. A polarization layer on your sunglasses lens will only allow vertically polarized light to pass through the lens and reach your eyes. However, if you use devices like smart phones with LCD panels polarized lenses will make the screen difficult to impossible to see.

How Sunglasses Work

Now that you understand how sunglasses are made we can discuss how sunglasses work. Basically sunglasses work through the use of various coatings on the sunglasses lenses which perform different tasks from filtering out light waves and protecting your eyes from dangerous ultraviolet light rays. In addition to the proper coatings being applied to the sunglasses lenses the way glass lenses are ground and the material they are made of are important in terms of how well the visual acuity is for you the wearer. Mineral glass lenses are the best for glass lenses but they are slightly heavier than polycarbonate lenses. In addition, glass lenses will reflect heat while polycarbonate lenses absorb heat making glass lenses cooler to wear for long periods of time.

An Excellent Choice

[caption id="attachment_210" align="alignright" width="280"]Randolph Engineering Aviators Randolph Engineering 23K Gold Frame Bayonet Temple AGX Glass Lens Aviator Sunglasses[/caption] When it comes to high quality sunglasses that meet all of the requirements above about how sunglasses work I recommend Randolph Sunglasses. They use mineral glass lenses, have the proper coatings, and have great style, comfort and performance. Take a few moments to look through our website at the various choices of Randolph Engineering sunglasses we offer, and in particular the Randolph Aviator Sunglasses. Keep your eyes cool and protected today my friend!

About John White a/k/a JetAviator7 p.s. Please share "How Sunglasses Work" with your friends. Thanks!

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