Sunglasses offer eye protection and style. Glare from reflective surfaces hinders vision and causes discomfort. Polarized sunglasses provide a specialized solution, enhancing visual clarity in bright conditions.
Understanding Light and Glare
Light travels as electromagnetic waves, vibrating in all directions in its natural, unpolarized state. Imagine light waves moving like ripples on a pond.
When light encounters a flat, reflective surface like water, snow, or a road, these waves become polarized, aligning horizontally. This horizontally oriented light is perceived as glare, which can be intense and reduce visibility, making it difficult to discern details and causing discomfort or temporary blindness.
The Principle of Polarization
Polarized lenses address glare through a filtering mechanism. They incorporate a special chemical film with a microscopic, grid-like structure. This structure is composed of aligned molecules that act as a selective barrier.
The filter allows only vertically oriented light waves to pass through. It blocks the horizontally oriented light waves that cause glare. This process is similar to how a picket fence allows only vertical slats to pass while blocking horizontal ones, eliminating reflections.
Crafting Polarized Lenses
The creation of polarized lenses involves embedding a specialized film within the lens material. This film is typically made of polyvinyl acetate (PVA), a synthetic resin, which is heated and stretched during manufacturing. This stretching aligns the long-chain molecules within the film, making them polarized.
The aligned film is then often treated with a conductive solution, such as iodine, which creates a microscopic grid of parallel lines. This treated film is precisely cut and then laminated or sandwiched between layers of the chosen lens material, such as plastic or polycarbonate.
Manufacturers carefully orient the film vertically within the lens during this process to ensure it blocks horizontal glare effectively. This precise alignment allows the lenses to maintain their glare-reducing properties. The completed lens often receives additional coatings for scratch resistance or anti-reflection.
Polarization Versus UV Protection
Polarization and UV protection serve distinct functions in eyewear, although they are often found together in sunglasses. Polarization specifically reduces glare by filtering horizontally oriented light waves. This contributes to visual comfort and clarity by improving contrast.
UV protection, in contrast, shields the eyes from harmful ultraviolet (UV) radiation emitted by the sun. UV rays can lead to various eye conditions over time, including cataracts and macular degeneration. A lens can offer one, both, or neither of these features. For comprehensive eye health, sunglasses that provide both polarization for glare reduction and 100% UV protection are recommended.