A High Resolution Displacement Measurement System Based on Time-to-Digital Converter

A microwave interferometry displacement measurement system based on time-to-digital converter (TDC) is proposed. As the TDC has advantages of high time resolution and linearity, it is introduced to replace common phase detector of microwave interferometer. The system is operating at 2.4 GHz in two-stage heterodyne, and its theoretically estimated displacement resolution is about 3 μm. Under the experimental condition of 50 μm moving step, measured maximum error is 30 μm with the standard deviation of 10.9 μm and the linearity is 0.9997.