Research Review on Absolute Photoelectric Angular Displacement Sensors

This paper provides an overview of research on absolute photoelectric sensors for angular measurement, specifically addressing the encoding methodologies and sensing structures of single-track, multi-track, image-based encoders, circular grating, and light-field time-grating systems. The fundamental characteristics of absolute position encoding, namely monotonicity and uniqueness, are discussed. A comparison of the performance of absolute encoders based on different encoding methods is presented. The paper also analyzes image-based encoders that utilize image sensors combined with encoding technology to achieve absolute measurement. Furthermore, it explores the construction of a uniform motion light field through time-grating technology and alternating optical fields, By implementing differential pole vernier encoding on a single-track, this approach enables hybrid absolute and incremental measurements, significantly enhances the precision and resolution of absolute photoelectric angular displacement sensors and achieves miniaturization. The future development directions of absolute photoelectric angular displacement sensors are also forecasted.