Abstract: The accurate measurement of surface finish requires standard specimens to calibrate and check the operation of the measuring instruments. This is true both for profiling techniques such as the stylus and area averaging techniques such as light scattering. For profiling stylus instruments, the international standard ISO 5436 has enumerated four types of standard specimens which may be classified as step height specimens, periodic roughness specimens, random roughness specimens, and specimens for checking probe tip resolution. A draft of a related U.S. standard uses the same taxonomy. For light scattering instruments, the use of standard specimens are discussed in the ASTM standard for total integrated scatter. In addition, several ad hoc standard specimens have been used in an interlaboratory comparison of instruments that measure the bidirectional reflectance distribution function (BRDF). Our group has developed a series of specimens, known as standard reference materials (SRMs), for calibrating stylus profiling instruments. We are also in the process of developing a series of profile specimens for calibrating the linearity of BRDF instruments. Both types of specimens have sinusoidal profiles and are discussed in turn. !8
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