Polarizing glass lenses have been known for more than 70 years - since, as the founder of the company «Polaroid» Edwin Land invented and produced the first samples in 1929. Early polarizing spectacle lenses were exclusively planned and in demand only the adherents of winter and water sports. Today, the benefits of these spectacle lenses appreciated not only by athletes - professionals and amateurs, but also ordinary buyers. In addition, due to the radical improvement of manufacturing technology and optical properties becoming more common prescription polarized glass lenses.
Some particles or surface property are completely or partially polarize light source depending on the angle of incidence and nature of the reflecting surface. Bright horizontal surfaces such as water, wet asphalt, sand, snow, ice, car body - the main sources of polarization of light in our environment. When light falls at a certain angle to a similar surface, it is reflected and becomes polarized. Polarized light creates a so-called optical interference or shine. These disturbances lead to poor visibility, cause blurred vision, forcing the person to squint and interfere with driving, skating, fishing and many other activities. The best eye protection from unwanted shine are polarizing spectacle lenses, which do not pass the most harmful horizontal component of the polarized light.
Manufacturing polarized lenses
Basis polarizing spectacle lens is a polarizing film filter. Prescription or qualitative targets polarizing spectacle lenses are manufactured by laminating the film-filter between the two halves of the spectacle lens. As a material for the production of spectacle lenses used CR-39 polycarbonate, cellulose acetate butyrate, high refracting organic materials, and colorless photochromic mineral glass.
A variety of materials and manufacturing methods have their own characteristics and advantages. Mineral polarizing spectacle lenses have the highest abrasion resistance and antireflection coatings deposited on their surface - maximum adhesion and durability. However, these spectacle lenses smallest impact resistance.
Organic glass lenses of CR-39 have huge impact and weigh half as much mineral. To improve their abrasion recommended hardening coating.
Polycarbonate polarizing spectacle lenses have the greatest resistance to shock loads and are considered the best means of protection against damage to eyes. However, they are inferior to the usual organic glass lenses by abrasion, so applying strengthening coatings is required.
The advantages high refracting organic materials include the fact that they make a thin and light spectacle lenses.
Considering the level of eye protection from UV radiation, we note that the quality polarizing spectacle lenses, regardless of the production of the material are a reliable means of protection, although this is achieved in different ways. Average permeability colorless mineral glass in the UV range, so to protect the eyes from ultraviolet radiation must enter UV absorbers in the film filter. Organic glass lenses and the polycarbonate have a UV absorber in the composition and a UV cut to 380 nm.
According to the degree of comfort superior to conventional polarized glasses sunglasses that protect the eyes while the bright sunlight, but do not remove the interfering shine.
Color polarized lenses
All spectacle polarizing spectacle lenses have a certain color. The earliest of these were green, are now produced ophthalmic lenses over a variety of colors: brown, gray, yellow, green and others. Color influences on vision and comfort of the user in different situations and under a variety of lighting conditions. Each of the above-mentioned color has its own characteristics and advantages.
Grey - reduces the total amount of visible light, without breaking the color. Lenses of this color provide user comfort during extended wearing period and recommended for driving and fishing.
Brown - provides a high contrast. Brown eyeglass lenses are recommended for practicing sports such as golf, skiing, rowing.
Yellow - improves contrast, it filters out the blue component of the visible spectrum. Yellow spectacle lenses can be recommended for practicing shooting and driving in low light conditions.
Rainbow - a gray top and pink at the bottom. Such spectacle lenses reduce the brightness of the top and simultaneously improve the contrast in the lower part, which can be useful, for example, when working on the computer.
The color polarizing spectacle lens is determined by the properties of the filter film and additional painting or coating applied to the surface of the entire spectacle lens. Spectral characteristics of eyeglass lenses are constant at different illumination conditions.
The latest generation of polarizing spectacle lenses, these lenses united properties with the advantages of organic photochromic - is polarized photochromic ophthalmic lenses. They change the light transmittance depending on the ultraviolet component of solar radiation and ambient temperature, darkening and brightening changing lighting conditions. Currently, polarizing photochromic spectacle lenses manufactured with mineral and organic photochromic photochromic materials manufactured by «Transitions» technology. Polarizing glass lenses - the most high-tech type of product, allowing the customer to provide maximum protection against excessive sunlight and the reflected brilliance.