DIN 50990 "Coating thickness measurement. Light spectrum Measuring method measurement of area-dependent mass of metal layers" standard specifies the technical requirements for the measurement of area-dependent mass of metallic coatings by the Light spectrum Measuring method. This method determines the thickness and mass of coatings by analyzing the Light spectrum characteristics of coatings, which is suitable for the detection of various metallic coatings. The standard details the working principle, operation steps and Measurement accuracy requirements of the Light spectrum measuring instrument to ensure the accuracy and Reliability of measurement results. Light spectrum method is a non-destructive Measuring method, which can provide high-precision coating mass data and is widely used in coating mass control and performance evaluation. This standard provides strong support for scientific measurement and mass assurance of coating thickness in industrial production, especially in the application of metallic coatings.