Color compensating retinal safety filter

Abstract From the Canadian patent

A filter and method for filtering an optical beam are disclosed. One embodiment of the filter is an optical filter for filtering an incident light beam, comprising an optically effective material characterized by: a light transmittance of less than 1% for wavelengths below 420 nm; and a light transmittance for wavelengths complimentary to wavelengths below 420 nm that combined with the transmittance for wavelengths below 420 nm will yield a , filtered light beam having a luminosity of about 90% and an excitation purity of 5% or less. The complimentary wavelengths can be wavelengths above about 640 nm, wavelengths above about 660 nm and/or wavelengths from about 540 nm , to about 560 …