Traceable spectral interferometry for length measurement

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Spectral interferometry is becoming a popular method of performing dimensional measurements, e.g. of surfaces, but such devices require pre-calibration of their spectrometers to achieve traceability. The use of a spectral lamp and imaging spectrometer to perform inherently traceable distance measurements using spectral interferometry, without the need for external calibration, is proposed and its experimental feasibility demonstrated. Initial experiments show measurements over a working range of 200 µm. The estimated standard uncertainty of the distance measurements is 0.6 nm, corresponding to an expanded uncertainty of 1.2 nm at k = 2.