Eyeglass rating with respect to protection against uv hazard

Abstract

An index value is calculated for rating an eyeglass with respect to protection against UV hazard. The index value is based on an integrated UV transmission value through the eyeglass and an integrated UV reflection value related to a back face of the eyeglass. Thus, the index value takes into account actual wearing conditions where UV eye exposure is due either to transmission through the eyeglass or reflection on the eyeglass back face. Respective index values obtained for a set of eyeglasses allow easy sorting of the eyeglasses with respect to UV protection efficiency.

1 .- 16 . (canceled) 
     
     
         17 . An eyeglass rated for quantifying an amount of UV light exposure on eyes of a wearer, the eyeglass comprising:
 a back face that reflects light; and   an indication of a visual rating associated with the eyeglass whereby the wearer is informed, the rating including an index value that quantifies a UV light exposure amount to the eyes of the wearer, the index value being based on an amount of UV light reflected from the back face of the eyeglass.   
     
     
         18 . The eyeglass according to  claim 17 , further comprising:
 a front face that transmits light,   wherein the index value is based on the amount of UV light reflected from the back face of the eyeglass and an amount of UV light transmitted through the front face of the eyeglass.   
     
     
         19 . The eyeglass according to  claim 18 , wherein the index value is calculated by:
 combining both amounts of UV light transmitted from the front face of the eyeglass and UV light reflected from the back face of the eyeglass using an addition formula with non-zero positive factors, respectively for the transmitted UV light and the reflected UV light, and calculating the index value from a non-zero base number divided by a result obtained in said combining step.   
     
     
         20 . The eyeglass according to  claim 19 , wherein a ratio of the non-zero positive factor for UV transmitted light used in the combining step to the non-zero base number is in the range of from 0.01 to 1. 
     
     
         21 . The eyeglass according to  claim 20 , wherein a ratio of the non-zero positive factor for UV transmitted light used in the combining step to the base number is 1. 
     
     
         22 . The eyeglass according to  claim 19 , wherein a ratio of the non-zero positive factor for UV reflected light used in the combining step to the base number is in the range of from 0.01 to 1. 
     
     
         23 . The eyeglass lens according to  claim 22 , wherein a ratio of the factor for UV reflected light transmitted light used in the combining step to the base number is 1.