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Describes a distance measuring instrument based on a frequency-modulation continuous wave interferometer. Use of a visible laser diode with a triangular wave form; Details on the accuracy and measuring range of the device; Modulation of real-time measurement capacity.

Presents a double heterodyne interferometric instrument using a tunable synthetic wavelength for the absolute measurements of distance and position. Generation of optical synthetic wavelength by a pair of Nd:YAG lasers; Development of the electronic circuit; Demodulation of the superheterodyne signals.

An optical interferometric instrument for the measurement of distance and position is presented. The system is based on a high-frequency sinusoidal phase-modulation interferometer. Phase modulation of the laser beam in one of the two interferometer arms is obtained by means of an electro-optic modulator operating at frequencies up to 10 MHz. The electronic unit performs synchronous demodulation of the signal coming from the photodetector. The resulting signals are fed to an up-down counting logic that is interfaced to a personal computer. The performance of the instrument has been evaluated by means of a system calibration against a reference high-precision commercial interferometer. The overall accuracy of the system resulted to be within 80 nm, at target speeds up to 1 m/s. In this article, the optical setup, the electronic equipment, and the calibration results are presented. [ABSTRACT FROM AUTHOR]