Rays has always been a part of the environment of mankind. One of our most important rays resources is the sun. Without the light and the warmth from the sun there would be no life on the earth.
The sunrays can be subdivided into three main sectors:
Ultraviolet ray (UV), between 280 and 380nm
Visible ray, between 380nm and 780nm
Infrared ray (IR), between 780 and ∞nm
Ultraviolet (UV) rays
Although it is the sun’s spectrum component that is present in the smallest quantity, it is the most dangerous component since it has sufficient energy to break chemical bonds, thus causing irreversible damage. As Ultraviolet rays is dangerous but not necessary component for vision, the objective of sun filter is its total elimination. The damage caused by ultraviolet rays mainly affect the cornea and crystalline, since the retina is screened almost totally by crystalline. Cataract is among the commonest pathologies affecting the crystalline.
There are three types of Ultraviolet rays:
UVA (315 to 380nm) are the principal cause of aging of the eye
UVB (280 to 315nm) also harmful, cause skin cancer, snow-blind (it burns parts of the retina) that you can be subjected to if you spend much time outside on the snow in sunny days.
UVC (100 to 280nm), potentially the most dangerous for the eyes, are filtered by Ozone in the upper layers of the Earth’s atmosphere.
And the intensity of sunrays at different wavelengths depends on altitude, latitude and weather conditions. The UV rays are strongest at high altitudes, low altitudes and in open or reflecting environments (sand, snow or water). There is about 4% increase in UV with every 1000 feet of altitude.
For this reason and in order to increase protection, in spite of the fact that the Ultraviolet rays is stopped at 380nm, but the UV rays absorption has been extended up to 400nm.
And for the protection viewpoint, wearing sunglasses is a sure way to avoid the damage of UV rays.
Infrared rays (IR)
There are three types of Infrared rays:
Near Infrared/Mid Infrared/Far Infrared
In practice, it can carry heat. Therefore it is less dangerous. Since it is not considered dangerous, there is no specific demand for filters in sunlens. But for filters designed for some industrial use, it is always asked to against the infrared rays. And it is extremely difficult to obtain the total elimination of the infrared component, i.e. only partial infrared rays attenuation is possible.
In addition, it’s known to use in photoelectric product, medical treatment product
The Blue light
the radiation between 380 and 500nm,it’s belong to Visible radiation
it has a very great energy being sufficient to cause cumulative damage to the retina. because it the closest compent to ultraviolet rays.
So far,no evidence has been found of direct damage to the eye at the normal amounts present in sun’s light,however there is substantial scientific evidence of cumulative damage to retina,commensurate to the exposure time and intensity of radiation.
From the protection viewpoint,we should reduce the amount of the Blue light to reach our eyes.But since it is a fundamental component for correct vision of colors and images,it should not be completely eliminated,instead,the right balance between effective protection and correct color vision should be sought.
Blue Blocker filters means to eliminate all Blue light ,the lens contains a yellow-orange filter that increases contrast and another filter that decreases blue light,and provide the perfect vision in hard sight conditions. For this reason,the Blue Blocker lenses are most for sporting activities.
But because the color’s characteristic that it has a very strong color distortion makes it difficult for the people to wear sunglasses for a long time,thus annihilating the advantages of protection.The damage caused by blue light is cumulatvie,therefore the limited use annihilates the effectiveness of protection.
Our recommendation:
The viewpoint that the limited use annihilates the effectiveness of protection is only a comment on the lens color. However, Hongtai Multi-coating (Same as Revo -Coating) has a specific function that can filter the Blue light.