Although the microscope image comparator was designed for quantifying the severity of surface imperfections, its ability to measure luminosity values of any image and compare values with images of similar objects suggests there may be other uses for this instrument. This generic technology has for convenience been termed far-field nanoscopy (FFN). Previous use of the term ânanoscopyâ appears to have been restricted to optical near-field probe measurements and could therefore be termed near-field nanoscopy (NFN).
This chapter illustrates the potential of FFN for replacing subjective assessments of surface quality by objective assessments of surface quality. It is aimed at filling the gap between visual assessment and that using expensive, slow profilometers. It indicates the potential of the technique for enabling the measurement of texture, surface height variations, imperfections, and contamination. Structures of nanometer dimensions, even when buried within a system already assembled, can be measured.
Since FFN often employs a microscope, albeit of low aperture, a wide range of complex, adaptive, and intelligent spatial frequency filtering techniques, such as dark-ground, partially coherent, and phase contrast, can be employed to compare surfaces with similar topographical structures for the purpose, for example, of quality control of surface finish. A wide range of specular surfaces can be measured.
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