Patent 7754630 was granted and assigned to Schott AG on July, 2010 by the United States Patent and Trademark Office.
An optical glass for the manufacture of large transmission optics, such as lenses having a thickness of 100 millimeters or more, comprises 35 to 70 wt.-% SiO2, 17 to 35 wt.-% Al2O3, 3 to 17 wt.-% P2O5, 0 to 6 wt.-% Li2O, 0.5 to 4 wt.-% MgO, 0.5 to 3 wt.-% ZnO, a maximum of 1 wt.-% CaO, a maximum of 0.5 wt.-% BaO, 0.5 to 6 wt.-% TiO2, 0.5 to 3 wt.-% ZrO2, 0 to 1 wt.-% Na2O, 0 to 1 wt.-% K2O, a maximum of 1 wt.-% of refining agents (As2O3, SP2O3) and a maximum of 500 ppm of other contaminants. The glass composition may be equal to the composition of the glass ceramic Zerodur® and allows to manufacture large transmission optics in a cost-effective way, has a maximum of transmittance which is in the range of a He—Ne lasers and has a CTE of about 3·10−6/K.