Polarized lenses are transparent pieces of material, usually glass or plastic, that block certain types of light waves. Sunglasses and camera lenses are often polarized to reduce glare from surfaces, such as light reflecting off a lake or the hood of a car. Somewhat like the way Venetian blinds control the amount of sunlight passing through a window, polarization blocks as much as 50% of the light passing through a lens. The person looking through the lens can still see clearly in most cases, but it reduces the brightness and glare of light.
How They Work
When light bounces off of a surface, its waves tend to be strongest in a particular direction — usually horizontally, vertically, or diagonally. This is called polarization. Sunlight bouncing off a surface like water, a road, or metal will usually reflect horizontally, striking the viewer’s eyes intensely and creating glare. Most polarized lenses in glasses are laminated with tiny vertical stripes that only allow vertically angled light to enter the wearer’s eyes. Glare is eliminated because the horizontal light waves cannot bypass the vertical filter.
Lenses can be polarized to different degrees and in different ways. Most inexpensive polarized sunglasses have a thin film applied on one side of the lens. Many higher quality lenses have film laminated between two layers of lens material, preventing it from being scratched or rubbed off. In addition, the more dense the film is, the more polarization it provides.