Interferometers for calibration of length standards

Automated interferometers designed for calibration of gauge blocks and line scales are described. The gauge-block calibrator is a scanning interferometer with a white-light source and 633-nm He-Ne laser. The line-scale interferometer also uses a dynamic measurement method with a microscope and a CCD camera as the graduation line detector. The interferometers mainly use the same electronic units and meters for the environmental parameters. The combined standard uncertainty (1σ) is 52 nm for the gauge-block interferometer and 72 nm for the line-scale interferometer for 1-m steel standards.