Striae quality grades for optical glass

The striae quality grades defined by the U.S. military standard MIL-G-174B, the ANSI/OEOSC OP3.001-2001 standard, and the ISO 10110-4 standard are evaluated to determine if they can be used to specify optical glass for high-quality optical elements. The evaluation is done by using each standard to determine the striae quality grades of 26 samples. The samples are representative of the striae quality grades, called shadowgraph grades here, defined by Schott Glass Technologies and used daily to control production of optical glass and to select glass for high-quality optical elements. The results show that all three standards need to define additional striae quality grades in order to specify glass for high-quality optical elements. The additional grades should be equivalent to the best shadowgraph grades: the Precision, A, and B grades.