The "GB/T 40293-2021 Infrared Sulfur Optical inspection film refractive index test method" standard details the principle, conditions, equipment, Sample Handling, test steps, data processing and refractive index calculation method of testing infrared sulphur Optical inspection film refractive index. This standard is applicable to the refractive index test of infrared sulphur Optical inspection film and can be used as a reference for Miscellaneous Optical inspection film test. The standard also covers the requirements of calculation accuracy and test report to ensure the accuracy and conformity of test results. Relevant Film thickness measurement and nanotechnology standards are cited to support accuracy and standardization during testing.