Proof of principle of an optical Stokes absolute roll-angle sensor with ultra-large measuring range

Abstract

We present a novel optical roll-angle sensor called Stokes roll-angle sensor. The measurement principle relies on modulating the roll angular displacement into the change of state of polarization (SoP) of polarized probe light by a quarter-wave plate (QWP). The SoP of the emerging elliptically polarized light from QWP is then detected by a Stokes polarimeter. Based on the detected Stokes vector, the roll angle can be extracted. Experimental results have shown that the proposed Stokes roll-angle sensor can realize absolute angle measurement in an unprecedented range of 180° with 0.02° resolution. Further expanding the measuring range to 360° is realizable by making a marker on the QWP to distinguish its two half parts divided by the fast-axis in the rotation. Other benefits of the proposed Stokes roll-angle sensor include simplicity, compactness, high speed, and low cost.