Spatial content analysis for precision surfaces with the area structure function

Structure function (SF) is the average height difference squared as a function of separation, which can represent the spatial content of precision surfaces. Linear SF has been applied in astronomy to area data and it captures data of all spatial content. However, it loses the information on anisotropy. The recently introduced two-quadrant area SF characterizes surfaces of arbitrary aperture over any chosen dynamic range while retaining anisotropic information. This paper discusses some computational issues of the SF, analyses the SF for surfaces described by a combination of Zernike polynomial terms and presents an example of its application to a diamond turned surface. (paper)