Research on precision linear displacement measurement method based on closed loop phase-shift control of single alternating light field

A high-precision linear displacement measurement method based on the digital phase shift of a single light source is proposed. In this method, the light intensity of a four-channel sinusoidal transmission surface with a 90° difference in the spatial phase is modulated by a single channel alternating light, and four-channel alternating light intensity signal with the same time phase can be obtained. Two channels of standing wave signals with a time difference of 90° are obtained through micro-control digital phase shift processing. After differential amplification, an electric travelling wave signal containing position information of measurement object is synthesized by these two standing wave signals. By measuring the phase difference between the travelling wave and the reference signal, the high precision linear displacement can be measured. The principle of displacement measurement based on the modulation of a single-alternating light field and the principle of digital phase-shift of micro-control are introduced in detail. The feasibility of the method is verified through experiments. Finally, the sensor is optimized by analyzing the causes of error, and the measurement accuracy of ±0.2 μm is achieved within the 100 mm range with a 0.6 mm grating period.