High Sensitivity and Full-Circle Optical Rotary Sensor for Non-Cooperatively Tracing Wrist Tremor With Nanoradian Resolution

Abstract

An optical rotary sensor based on laser self-mixing interferometry is proposed, which enables noncontact and fullcircle rotation measurement of non-cooperative targets with high resolution and sensitivity. The prototype demonstrates that the resolution is 0.1μrad and the linearity is 2.33×10 -4 . Stability of the prototype is 2μrad over 3600s and the repeatability error is below 0.84°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.

An Ultrasensitive and Universal Surface Plasmonic Biosensor for Detection of Micropollutants in Aquatic Environments

“…The feedback beams returned to the laser cavity along the original path, hence inducing the intensity modulation of the laser. The modulated laser power output caused by the two feedback beams can be described as , .25ex2ex normalΔ I p ( Ω p ) I = κ p G ( Ω p ) .1em normalcos ( 2 π Ω p t − ϕ f p + ϕ e p ) normalΔ I s ( Ω s ) I = κ s G ( Ω s ) .1em normalcos ( 2 π Ω s t − ϕ f s + ϕ e s ) where Δ I p and Δ I s are the feedback light-induced intensity modulation of p -polarized beam and s -polarized beam, respectively; Ω p and Ω s are the shift frequencies of the two beams; I denotes the stationary laser intensity; κ p and κ s are the coefficients of the feedback strength of the two beams; ϕ fp and ϕ fs are the fixed phases of the two beams; ϕ ep and ϕ es are the external phases of the two beams; G (Ω p ) and G (Ω s ) are the frequency-dependent gain factors. To compensate ...…”

“…The feedback beams returned to the laser cavity along the original path, hence inducing the intensity modulation of the laser. The modulated laser power output caused by the two feedback beams can be described as , where Δ I p and Δ I s are the feedback light-induced intensity modulation of p -polarized beam and s -polarized beam, respectively; Ω p and Ω s are the shift frequencies of the two beams; I denotes the stationary laser intensity; κ p and κ s are the coefficients of the feedback strength of the two beams; ϕ fp and ϕ fs are the fixed phases of the two beams; ϕ ep and ϕ es are the external phases of the two beams; G (Ω p ) and G (Ω s ) are the frequency-dependent gain factors. To compensate the intensity drift induced by air disturbance, laser, and other inherent mechanical and thermal noise, we defined Δ I = Δ I p – Δ I s as the corrected intensity change corresponding to the RI variations.…”

“…The feedback beams returned to the laser cavity along the original path, hence inducing the intensity modulation of the laser. The modulated laser power output caused by the two feedback beams can be described as 17,18 To obtain a larger gain factor G(Ω i ) and demodulate the pand s-polarized beams separately, three acousto-optic modulators (AOMs) were employed, in which AOM 2 and AOM 3 were set with different working frequencies (Figure 1b). The frequency-dependent gain factor G(Ω i ) can be expressed as 18,19 = +…”

Ultrasensitive Screening of Endocrine-Disrupting Chemicals Using a Surface Plasmon Resonance Biosensor with Polarization-Compensated Laser Heterodyne Feedback

“…The feedback beams returned to the laser cavity along the original path, hence inducing the intensity modulation of the laser. The modulated laser power output caused by the two feedback beams can be described as , normalΔ I normalp ( Ω p ) I = κ normalp G false( normalΩ normalp false) cos ( 2 π Ω p t − ϕ f p + ϕ e p ) normalΔ I normals ( Ω s ) I = κ normals G false( normalΩ normals false) cos nobreak0em.25em⁡ false( 2 π normalΩ normals t − ϕ normalf normals + ϕ normale normals false) where Δ I p and Δ I s are the feedback light-induced intensity modulations of the p-polarized beam and s-polarized beam, respectively, Ω p and Ω s are the shift frequencies of the two beams, I denotes the stationary laser intensity, κ p and κ s are the coefficients of the feedback strength of the two beams, ϕ fp and ϕ fs are the fixed phases of the two beams, ϕ ep and ϕ es are the external phases of the...…”

“…The feedback beams returned to the laser cavity along the original path, hence inducing the intensity modulation of the laser. The modulated laser power output caused by the two feedback beams can be described as , where Δ I p and Δ I s are the feedback light-induced intensity modulations of the p-polarized beam and s-polarized beam, respectively, Ω p and Ω s are the shift frequencies of the two beams, I denotes the stationary laser intensity, κ p and κ s are the coefficients of the feedback strength of the two beams, ϕ fp and ϕ fs are the fixed phases of the two beams, ϕ ep and ϕ es are the external phases of the two beams, and G (Ω p ) and G (Ω s ) are the frequency-dependent gain factors. To compensate for the intensity drift induced by air disturbance, laser, and other inherent mechanical and thermal noise, we defined Δ I = Δ I p – Δ I s as the corrected intensity change corresponding to the RI variations.…”