Eyeglass rating with respect to protection against UV hazard

摘要

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.

主权项

1. A method of providing to a customer of an eyeglass a rating of the eyeglass with respect to protection provided by the eyeglass against UV hazard, the rating based on an index value, which quantifies a reduction in a total UV amount impinging onto an eye for a wearer of the eyeglass with respect to UV exposure without the eyeglass, the method comprising the steps of:
measuring UV intensity with a photometer for light reflecting from a back face of the eyeglass; providing a value of UV transmission for the eyeglass; providing a value of UV reflection on a back face of the eyeglass; combining both values of the UV transmission and the UV reflection of the eyeglass using an addition formula with non-zero positive factors respectively for the UV transmission and UV reflection; and calculating the index value from a non-zero base number divided by a result obtained in the combining step, the index value being based in part on measurements obtained in the measuring step and accounting for incident light that reaches an eye of the wearer from the back face of the eyeglass; and providing to a customer the rating for the eyeglass.