This International Standard specifies measurement procedures for the precise determination of the high reflectance of optical laser components. Up to now, the ISO standardized testing methods for reflectance of optical laser components have the accuracy limit of approximately 0,01 % (for measurement of absolute reflectance) which are not appropriate for measuring the reflectance higher than 99,99 % or, in some cases, measurement accuracy better than 0,01 % is required. The range of application of this standardized test method is reflectance 99 % and higher (theoretically up to 100 %).

The methods given in this International Standard are intended to be used for the testing and characterization of high reflectance of both concave and plane mirrors used in laser systems and laser-based instruments. The reflectance of convex mirrors can also be tested by taking into consideration the radius of curvature of the mirror surface.