A Time-Grating Sensor for Displacement Measurement With Long Range and Nanometer Accuracy

It is difficult to achieve long measurement range with high precision in displacement measurement, a new nanometer displacement sensor, named time grating, is proposed to tackle this problem. The proposed displacement sensor uses orthogonally alternating electric fields as the carrier to build the relationship between the object movement in space domain and the signal phase shift in time domain, and the moving displacement of the object is proportional to the phase shift of the composited traveling wave signal that can be measured by time difference. The electric-field distribution of the sensor is simulated to analyze the influences of various factors, such as electrode intervals and electrode width. The results are further validated with experiments. The error characteristics are extracted using error identification technology and traced back to the sensor model, thus the relationships between the error characteristics and the model parameters are obtained. The experiment results prove that the measuring precision reaches +/- 200 nm and the resolution reaches 1 nm within 200 mm. Submillimeter period sensing unit realizing nanometer precision and resolution has shown significant promise in fabricating large range nanometer displacement sensors with low cost.