GB/T 20968-2007 in English

《GB/T 20968-2007无损检测 目视检测辅助工具 低倍放大镜的选用》由TC56（全国无损检测标准化技术委员会）归口，主管部门为国家标准化管理委员会。
本标准规定了单片镜放大镜、多片镜放大镜、双系统件放大镜等类型低倍放大镜的特性，并推荐选择用于表面检测。

Scope

1.1 This standard specifies the characteristics of the following types of low power magnifiers and recommends their selection for surface inspection. - Monocle mirror magnifying glass, typical magnification up to 4 times (Type A). —Multi-lens magnifying glass with a typical magnification of 10 times (type B). - dual-system magnifiers, typically with a magnification of 15 times (type C), of the following two types: a) binoculars, usually with a long working distance (type C.1); b) binoculars, equipped with narrow Adjustment or other accessories for stereo viewing (Type C.2). - Concave lens magnifying glass with front surface mirror, typical magnification up to 6 times (type D). 1.2 This standard does not deal with: - small magnifying glasses and spectacles that the watchmaker puts on the eye sockets; - monocle magnifying glasses, spherical or cylindrical lens magnifying glasses (including magnifying glasses with useful magnifying glass for various graduated scales used for measurement); - liquid-filled, plastic lens capsule; - magnifying glass for internal surface inspection.