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Long-wavelength laser diode interferometer for surface flatness measurement

Modem phase-shifting interferometers grew out of a traditional need for high-precision evaluation of polished optical components. The technology is very mature now, enough so that it is reasonable to look for other applications of these instruments. Some important industrial applications have been found, particularly in the data storage industry. However, there are still many applications where the speed and high accuracy of phase-shifting interferometry would be very desirable, but the surface-finish requirements to generate visible-wavelength interference fringes are impractical.