High-Precision Angular Displacement Measurement Based on Rotating Optical Field

To tackle the problems in traditional high-precision angular displacement measurement, such as complicated manufacturing process, complex multi-probe structure and difficult installation, this paper proposes a new relevant full-circle method based on the construction of a rotating optical field, inspired by the generation principle of a rotating magnetic field. A sinusoidal uniform grating surface on the full circle is divided by an equal interval into four groups of 0 degrees, 90 degrees, 180 degrees, and 270 degrees. Alternating light intensity signals are provided for the full-circle grating surface by a one-way alternating optical field, which are transformed into electric traveling wave signals via photoelectric conversion and micro-controlled phase shift. The angular displacement measurement is realized by the interpolation of the phase difference between reference signals and electric traveling wave signals with a high-frequency clock pulse. An experimental platform is established for the comparative experiment on different principle prototypes. The influence of manufacturing precision and number of pole pairs on the measurement error is verified by experiments. The measurement error can reach +/- 5.0" when the grating surface with a central angle of 2 degrees is used in the full-circle measurement range. Since the measurement error is mainly composed of periodic error components, the measurement precision will be greatly improved after the correction of harmonic error and the quality improvement of optical field distribution. This paper verifies the suppressing effect of the proposed method on manufacturing and installation errors and provides an effective solution to the high-precision measurement for low-precision manufacturing processes.