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How Important Are Mineral Glass Lenses for Sunglasses?

by John M. White |

The refractive index is an indication of how well light can travel through the lens material, and the dispersion factor refers to how light is dispersed through a medium. The value of these indices provides a way to gauge the quality of the sunglasses lenses used in a pair of sunglasses you may be looking to purchase. Relying solely on price will not guarantee you that you have the best quality sunglasses lenses available.

The Importance Of The Refractive Index

The refractive index of a substance is a measurement of the speed of light through that medium. For example, the refractive index value of water is 1.33 - in other words, light travels 1.33 times faster in a vacuum than through water. For visible light most transparent media have refractive indices between 1 and 2.

The Importance Of The Dispersion Index

A good example of dispersion is a rainbow where the colors are split into bands of light creating a rainbow where you can see the various colors separated from one another. In sunglasses lenses you want to have as little dispersion as possible. Dispersion is described by a number called an Abbe number.

Why Crown Mineral Glass Sunglasses Lenses?

Crown mineral glass sunglasses lenses are used in high quality sunglasses because they have a typical refractive index value of ~1.52 and a low dispersion Abbe value of ~60 making them ideal in terms of visible light transmittance through the lenses. Randolph Engineering sunglasses have an Abbe value of ~50, and allow 15 to 18% of visible light to pass through the lens with no distortion and allowing true color reception of visible light rays. Crown glass refers to a type of soda-lime glass commonly used in windows, and is one of the most common forms of glass manufactured in the world. The process of manufacturing crown mineral glass lenses involves blowing liquid fluid glass into a spherical vessel and then attaching a rod to the molten glass and spinning it into the form of a disc. The disc is then cut into several planes and placed into a mold on a press turntable and then pressed into the concave (or crown) shape. Borosilicate crown glass is made with boric oxide, zinc oxide, barium oxide, fluorite and phosphorus pentoxide and has excellent Abbe values of 50 to 85 - the lower the number the better the quality of the sunglasses lenses. You can learn more about crown mineral glass at the Lens Compendium.

What To Consider When Choosing Sunglasses Lenses

When choosing a pair of high quality sunglasses it is important to make sure they have crown mineral glass sunglasses lenses in them to provide the very best visual acuity for the wearer. If you need prescription sunglasses you can purchase a pair of Randolph Aviator frames, provide your prescription and we will make you a pair of prescription sunglasses. You can learn more about prescription lens frames here on our website.

Where To Find Crown Mineral Glass Sunglasses Lenses

Be sure to check out the great selection of high quality sunglasses with mineral glass lenses in sunglasses on our website at Randolph Engineering Sunglasses. Have a prosperous day!

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