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Surface roughness affects the function of a wide variety of engineering components, including airport runways, highways, ship hulls and mechanical parts. Perhaps the most demanding applications are in the optics and semiconductor industries. Surface roughness causes scattering and stray light in optical systems and degrades the contrast and sharpness of optical images, so in general, the smoother the surface, the better the component will function. In the optics industry, the terms surface roughness and surface finish are synonymous. The rms roughness is perhaps the most widely used parameter for specification of the roughness of optical surfaces. For high-performance optics, such as those in lithographic steppers, space optics, and laser gyro systems the rms roughness is specified in the subnanometer range. If the measured surface topography is represented as a surface profile z(x), the rms roughness (Rq) is defined as the root mean square of the deviations of the surface profile z(x) from the mean line.
Citation
Optical Engineering Magazine
Volume
2
Issue
No. 3
Pub Type
Journals
Keywords
atomic force microscopy, interferometry, nomarski, power spectral density, profiling, rms, roughness, stylus, surface