At polarized lenses they are pieces of transparent material, although they can be colored, that allow the passage of certain types of light and prevent the passage of others.
They are used in many types of optical devices, for example in sunglasses video and photo cameras, microscopes and telescopes, etc.
Polarized lenses allow reduce glare and Increase the contrast of the image, obtaining a sharper image, mainly in conditions of intense brightness and reflections.
How polarized lenses work
At electromagnetic waves that make up the sunlight oscillate in all directions. When reflected off a surface, many begin to oscillate in a specific direction and at close angles. These light waves are said to be “polarized” in that specific direction .
THE light of the sun reflected in a flat surface such as water, asphalt or the body of a car, is skewed usually for the horizontal and produces intense shine and shine.
Grid interposition polarization
There are different types of polarized lenses, depending on the polarization method used. The most common are grid interposition polarized lenses .
These types of polarized lenses are laminated . They contain small strips of an opaque material that form a grid allowed The passing only vertical waves.
Horizontal light waves do not pass through and therefore the flashes produced by reflected sunlight are eliminated.
O degree of polarization can vary from one lens to another and can reach up to 50%. High quality polarized lenses usually have the polarized sheet protected between two layers of normal lenses, others adhere the polarized sheet to the surface of one of the faces.
In general, the greater the polarized sheet density, the greater the degree of polarization produced by the lens.
Polarization by absorption and reflection
In addition to the polarization of grid , there are polarizers that use other methods. Some of them are absorption polarizers and reflection polarizers.
THE polarization absorption can be found naturally in tourmaline crystals. You polaroid polarizers (manufactured by Polaroid Corporation) use this polarization.
Previously, they were manufactured with the inclusion of herapatite (iodoquinine sulfate) microparticles in the lens glass, which also provided greater strength and durability.
These microparticles would act similarly to the grid, but at the microscopic level. They are currently manufactured with a PVA sheet (polyvinyl acetate) doped with iodine and are widely used in sunglasses and photographic polarizers.
You sunglasses with polarized lenses in most cases, are not distinguishable to the naked eye without polarized glasses, as the polarizing film is so thin that you cannot see.
The degree of polarization, as mentioned above, depends on the characteristics of the polarized sheet, not the color of the sunglasses.
Polarized sunglasses have become very popular with drivers, fishermen and water sports. They are currently very widespread, as they offer greater protection against ultraviolet rays and greater visual comfort.
Glasses with polarized lenses have several limitations. The first is that they are not effective in reducing light reflections in vertical surfaces . For example, in the windows of a building.
To view LCD screens ( screen of liquid crystal ) with polarized lenses can cause image distortion .
In addition, when polarized lenses are used, the laminated glass and glass texture tempered which are used as safety glass on windshields, may become more obvious and make viewing difficult .
For these reasons, the airline pilots cannot wear polarized glasses, as they can make it difficult to read the flight instruments and make it difficult to see other objects in the sky.
In general, polarized lenses don’t work well in snow, because snow reflects light in many directions, not just horizontally. In many snow sports, they can pose a danger.
For example, alpine skiers can intuit the presence of ice sheets by the reflection of light, which in ice is mostly horizontal, and polarized lenses, by reducing this reflection, would make them difficult to recognize.
When a person wears glasses with polarized lenses, they can see the flashes by tilting their head approximately 45 degrees from vertical to either side. Some people may experience a headache when wearing this type of glasses for a long time.
Polarized lenses in 3D cinema
O 3D glasses film is based on the same principle. The image projected on the screen is composed of two beams of light one polarized horizontally and the other vertically.
Each 3D glasses lens is polarized in a different direction. In this way, in one eye the image of one of the light beams is seen and in the other eye the image of the other beam is received.
The combination of both and their interpretation in the brain gives the sensation of depth when in reality the image is flat.