Average transmittance of sunglasses

(UV spectral region)
The average transmittance is the average transmittance of a lens to ultraviolet rays in the ultraviolet spectral range, as specified by the standard:
a) The average transmittance in the UVA wavelength range of 315nm to 380nm τ SUVA should be ≤ τ V;
b) The average transmittance in the UVB wavelength range of 290nm to 315nm τ SUVB should be ≤ 0.5 τ V.
In addition, in the UVB band, the average transmittance of light colored sunglasses should be ≤ 30%, and the average transmittance of sunshades should be ≤ 5%.
When sunglasses meet this requirement, they meet the basic requirement of protection, which is to block both strong light and a corresponding amount of ultraviolet light, Wearing these sunglasses will not increase the acceptance of ultraviolet light at least (wearing sunglasses will reduce the flux of entering the human eye, causing the wearer's pupils to increase. Under the same external conditions, if sunglasses cannot block the corresponding amount of ultraviolet light, the human eye will receive more ultraviolet light than when not wearing sunglasses). In November 2006, GB10810.3 "Glasses, Lenses and Related Products - Part 3: Transmittance Specifications and Measurement Methods" was officially implemented, which clearly stipulated that the maximum ultraviolet transmittance of sunglasses lenses should not exceed 5%.