The average transmittance of sunglasses

(Ultraviolet region)
The average transmittance is the average transmittance of ultraviolet rays in the ultraviolet spectrum of the lens, and the standard stipulates:
a) In the UVA band of 315nm ~ 380nm, the average transmittance τSUVA should be ≤τV;
b) In the UVB band of 290nm ~ 315nm, its average transmittance τSUVB should be less than 0.5τV.
In addition, in the UVB band, the average transmission ratio of light-colored sunglasses should be ≤30%, and the average transmission ratio of sunshade glasses should be ≤5%.
When the sunglasses meet this requirement, it meets the most basic requirements of protection, that is, blocking the strong light while also blocking the corresponding amount of ultraviolet light, wearing the sunglasses will not increase the amount of ultraviolet light accepted (wearing sunglasses, will reduce the luminous flux into the human eye, resulting in the wearer's pupil enlargement, under the same external conditions, if the sunglasses can not block the corresponding amount of ultraviolet light, The human eye will receive more UV light than it would without sunglasses). In November 2006, the GB10810.3 "Glasses lenses and related products Part 3: Transmittance specifications and measurement methods", which was formally implemented, clearly stipulated that the maximum ultraviolet transmittance of sunglasses lenses should not exceed 5%.