Optical Glass – Standards: Present state and outlook

Three parts of the standard ISO10110 specifying indications in drawings of optical elements cover material properties: part 2 (stress birefringence), 3 (bubbles and inclusions) and 4 (inhomogeneity and striae). Buying optical raw glass using element drawings leads to uncertainty, over-specification and delivery problems. A new part 18 of ISO 10110 is under preparation and is meant to be in harmony with the raw glass standard ISO12123 and to replace parts 2 to 4. The draft ISO/WD10110 part 18 extends indication possibilities to allow relating to ISO12123 while ensuring backward compatibility. Default optical glass quality and direct specification of raw glass simplify tolerancing considerably. Annexes support selection of appropriate quality classes referring to optical elements size categories.ISO12123 itself will be amended by introducing definitions for relative partial dispersions and reference normal lines and grade denominations for tolerance ranges. Test and inspection standards on chemical resistances, hardness, stress birefringence and optical homogeneity will be maintained. Standards for water resistance, refractive index and striae inspection are being prepared.