Understanding Sunglass and Its Technology
Understanding Sunglass and Its Technology:
Sunglasses are one of the widely use fashion accessories and are preferred by people of all ages. If any one asks us what sunglasses do then we promptly answer that it helps us protect our eyeglasses from Sun’s UV light and offers a cool vision on a bright sunny day. But are we aware of all the technology of sunglasses that are currently in use? In this article we will discuss about the different technologies of sunglasses.
Tinting
Polarized
Photo-chromatic Lenses
Mirror Coating
Anti-Scratch Coating
Anti-Reflective Coating
UV Coating
Tinting:
The lenses are basically immersed in a special liquid containing the tinting material. The tinting color is slowly absorbed in the lenses giving lenses the desired color. To make the lenses darker the lenses are simply immersed in the solution for longer period. This is how a conventional Plastic CR 39 lenses are tinted. Different material lenses required different method of tinting. Different manufacturers use different colors to produce tinted lenses thus the tint of the lens may vary.
Under tinting there are two types of variants: Solid and Gradient. Solid tinted lenses has a uniform color on the lens where as gradient tinted lenses has a darker tint on the upper portion of the lenses and gradually lightens as it comes down.
The most preferred tinting colors for sunglasses are grey, brown, yellow, amber, green and rose.
Polarized:
Polarized sunglasses offers complete sun protection as it comes with 100% UV protection and above all it helps reduce glares from long, flat surface such as water, snow, road’s surface and hood of the car.
It is important that we get a better understanding of how polarized lenses work before we decide to buy polarized sunglasses. Sunlight itself is not in a polarized state and hence it can vibrate up and down, sideways and obliquely. When the light is reflected off a horizontal surface like water, road or snow it will strike the viewers eye at a similar angle. This means that the glare from the surface of water, road or snow will be strong; as a result the visibility will decrease.
Polarized lenses are processed with thin laminated vertical line film. This vertical line film only allows vertically vibrating light waves to pass through the lenses and the remaining light waves are blocked as a result the glare is eliminated as the horizontally vibrating light waves are blocked by polarized filter.
Photo-chromatic lenses are the ones that changes it color when the lenses comes in contact with UV light. Theses lenses have molecules of silver chloride and silver halide, embedded in them and thus when the lenses comes in contact us UV light the molecules undergo chemical process and causes the lenses to change color. The darkening of the lenses depends on the intensity of the UV light. Photo-chromatic lenses are widely used for prescription eyeglasses.
Since the darkening of the lenses depends on the intensity of UV light there will be times when the lenses will not change its color. For example the lenses will not change its color if you are sitting behind the wind shield of a car as the wind shield filters the UV light thus the lenses will not change color.
Mirror Coating:
Many sunglasses often have a mirrored look. Theses lenses have a reflective coating applied on the lenses. Often mirrored coating is applied gradient to offer additional protection from the light coming from above but allowing light to pass light from below and straight.
The main disadvantage of mirror coating is that the lenses get easily scratched.
Anti-Scratch Coating:
Plastic lenses gets scratched very easily as compared to mineral glasses lenses thus the prescription lens manufacturer has developed ways to make the lenses more scratch resistant by applying optically hard film on the lenses. Anti-scratch coating helps protect your lenses from getting scratches but it is still doesn’t make the lenses scratch proof.
Anti-Reflective Coating:
Anti reflective coating is similar to Anti-scratch coating and are applied on sun lenses to eliminate black glare that is when the light hits back of the lenses and then reflects back in the eye.
UV Coating
UV coating helps protect your eyes from harmful UV light from the sun. Most of the sunglasses come with UV protection and usually it is mentioned on the label of the sunglasses. Always make sure you purchase glasses with 100% UV protection.
Date: Apr 12th 2011
