Between the 1940s and 1970s, a number of camera manufacturers designed lenses employing thoriated glass in one or more elements. Incorporating as much as 40% thorium dioxide (ThO2) in the glass mixture increases the index of refraction of the glass while maintaining low dispersion.
Thoriated glass elements allowed lenses to deliver low levels of aberration […]. petapixel.com
2018-6-8 22:20