A phase encoding method for improving the resolution and reliability of laser interferometers (displacement measurement)

An electronic method is proposed for improving the resolution and reliability of a laser interferometer commonly used for measuring displacement. By assigning code numbers to the divided segments of the interference fringe interval, the displacement of the moving device is measured with 1/170 of the lightwave length resolution (about 4 nm with He-Ne laser). Since the error caused by environmental noise is not integrated in the counting process, the measured values become more reliable than those of conventional pulse-counting methods.<
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