A Dual-Beam Differential Method Based on Feedback Interferometry for Noncontact Measurement of Linear and Angular Displacement

A dual-beam differential method for noncontact measurement of linear and angular displacement is reported in this article. Compared to other optical sensors, the system based on the frequency-modulated feedback interferometry has higher sensitivity for noncooperative targets and a wider range with respect to the angle measurement. Performance of the proposed method is evaluated via testing a prototype system. The experimental results show that the prototype has a stability of 35 nm and 0.15" over 1 h with a resolution of 1 nm and 0.02", respectively. The linearity is 5.58×10 ⁻⁶ in the range of 100 mm and 1.34×10 ⁻⁴ in the range of 360°. The experiments for PZT deformation measurement and rotary motor monitor indicate that the proposed method possesses considerable potential for high-precision metrological applications, such as lathe calibration and motor control.