High sensitivity and full-circle optical rotary sensor for non-cooperatively tracing wrist tremor with nanoradian resolution

TL;DR

This paper introduces a highly sensitive optical rotary sensor capable of non-contact, full-circle rotation measurement with nanoradian resolution, suitable for tracing wrist tremors and nano-motion monitoring, with advantages over traditional sensors.

Contribution

The paper presents a novel laser self-mixing interferometry-based rotary sensor achieving nanoradian resolution, non-cooperative target measurement, and high sensitivity, with demonstrated stability and repeatability.

Findings

Resolution of 0.1 μrad achieved

Successfully traced wrist tremor with a bionic hand

Theoretical resolution up to 16 nrad

Abstract

An optical rotary sensor based on laser self-mixing interferometry is proposed, which enables noncontact and full-circle rotation measurement of non-cooperative targets with high resolution and sensitivity. The prototype demonstrates that the resolution is 0.1${\mu}$rad and the linearity is 2.33$*$10$^{-4}$. Stability of the prototype is 2${\mu}$rad over 3600s and the repeatability error is below 0.84${\deg}$ under 9-gruop full-circle tests. The theoretical resolution reaches up to 16nrad. Random rotation has been successfully traced with a bionic hand to simulate the tremor process. Error analysis and limitation discussion have been also carried out in the paper. Although the accuracy needs further improvement compared with the best rotary sensor, this method has its unique advantages of non-cooperative target sensing, high sensitivity and electromagnetic immunity. Hence, the optical rotary sensor provides a promising alternative in precise rotation measurement, tremor tracing and nano-motion monitoring.