GET 183-2019: State Primary Special Standard of the Unit of Length in the Field of Measurements of the Parameters of Deviations of Optical Surfaces from Flatness

GET 183–2019, the State Primary Special Standard of the unit of length in the area of measurements of the parameters of deviations from flatness of optical surfaces, is presented. The standard supports the reproduction, storage, and transmission of the unit of length in the range 0.002–2.000 μm for optical surfaces measuring 50–280 mm in dimension. An interference apparatus incorporated into GET 183–2019 in which a new method of treatment and interpretation of interference patterns is described, the method of phase steps, is implemented. Studies conducted as part of an effort at improving the standard, including theoretical and experimental investigations of the interference apparatus, are described. The selection of the new method is evaluated and a comparative analysis of the calibration and measurement capabilities of foreign metrological devices is performed. The metrological characteristics of GET 183–2019 are presented.