DIN ISO/TR 21477 DIN SPEC 13477:2018-08

ISO 10110-7 provides a notation for the indication of the level of acceptability of surface imperfections of optical elements and optical assemblies. It provides two systems of drawing notations for permissible imperfections: one based on area and size of imperfections and the other based on the visibility or appearance of imperfections. ISO 14997 provides test methods for these two systems of drawing notation. These two systems of specification and verification are totally different, with different accumulation and acceptance rules. As a result, a user who is only familiar with one of the systems can become confused when needing to interpret specifications in the other system. There is no way to translate a specification in one system into a specification in the other system because their criteria for acceptability are not interchangeable. The size or area of an imperfection is not correlated with its visibility or brightness. This document intends to guide the user to understand the origins, meanings and differences between the two systems of specifying and evaluating surface imperfections in ISO 10110-7 and ISO 14997, specifically the dimensional method and the visibility method, and to provide information on how to use them. Tables are provided to show specifications of roughly equivalent yield loss for imperfections in the two systems.