The ISO 3868 standard Metals and Miscellaneous non-organic coatings. Coating thickness measurement. Fizeau multi-beam of light interferometry specifies a method for the measurement of metal and Miscellaneous non-organic Coating thickness using the Fizeau multi-beam of light interferometry method. This method accurately measures the thickness of coatings through interference phenomena and is suitable for high-precision detection of thin coatings. The standard details the instrument setup, operating procedures and Measurement principles to ensure high-precision and Repeatability of Coating thickness measurement. Fizeau multi-beam of light interferometry is a non-contact, non-destructive measurement technology widely used in high-precision coatings measurement, especially for demanding scientific research and industrial testing, such as aerospace, microelectronics manufacturing and other industries. The standard provides an important basis for coating mass control and coating application performance evaluation.