Large range and high resolution on-line displacement measurement system by combining double interferometres

A stabilized interferometric displacement measurement system, which is suitable for on-line measurement and is endowed with large measurement range and high resolution, is proposed. The system is stabilized by a feedback loop which compensates the influences induced by the environmental disturbances and makes the system stabile enough for on-line measurement. Two different wavelengths are working simultaneously in the system. The measurement range which is determined by the synthetic-wavelength interferometric signal is expanded to the order of millimeter, while the measurement resolution which is determined by one of the single-wavelength interferometric signal is the order of sub-nanometer.