Protecting your eyes from Mid-Coast Optical
What do you know about polarized lenses? Did you know we should all be protecting our eyes from the sun's harmful rays. The following is very helpful info on polarization...
Polarized lenses are used in sunglasses to reduce glare from reflective surfaces, water, snow, anything shiny. This is done through a process called polarization, much like a venetian blind controls sunlight through a window.
Sunlight itself is not polarized - light from the sun will either be absorbed or reflected horizontally, diagonally or vertically. The problem this causes for fishermen and drivers lies in the horizontal reflectivity. Sunlight bouncing off a horizontal surface will strike the viewer's eyes at a similar angle. This means the glare from the surface of the water or the road or the car hood will be strong. Polarized lenses have a laminated surface containing vertical stripes. These stripes only allow vertically-polarized light to enter the wearer's eyes. Glare is eliminated because the horizontally-polarized light waves cannot bypass the polarized filter.
Polarized lenses do not provide universal protection from glare, however. If the wearer tilts his head past 45 degrees or so, some of the horizontal light can enter and cause some bright spots. Some wearers who use polarized lenses in snowy areas may find that they lose some contrast between snow and shadows. Fishermen and drivers seem to derive the most benefit from polarized lenses because they deal with mostly horizontal surfaces. A fishermen wearing polarized lenses can see below the surface of the water to search for schools of fish or hidden obstacles. Drivers are no longer affected by a constant reflection of light from their hoods or the road ahead.
There are some limitations to the use of polarized lenses, however. Because the polarizing stripes reduce the amount of light entering the eye, polarized lenses cannot be used for regular eye wear with clear lenses. Some drivers discover that polarized lenses can cause distortions in liquid crystal displays (LCDs). On board clocks and other instrument displays may be temporarily unreadable.
Pollick, Michal “What are Polarized Lenses?” wiseGEEK, April 16, 2010, May 21,2010