GB/T 18777-2009 Phase Correction Filter for Surface Structure Profile Method in Geometry Specification for Focused Products. This standard explains in detail the Measurement characteristics of such filters, clarifies their key parameters in surface structure measurement, such as cutoff wavelength, transmission characteristics, etc., and specifies the Measuring method and accuracy requirements for related characteristics. Through unified standards, it provides support for accurate acquisition of surface profile information, and helps to accurately evaluate the surface structure of products with the help of phase correction filters in machinery manufacturing and other industries to ensure that product mass meets relevant standards.