Compact optical roll-angle sensor with large measurement range and high sensitivity

A simple and effective optical roll-angle sensor based on a magnetic garnet single crystal is demonstrated. The measurement is based on the principle that, when linearly polarized light whose polarization varies alternately in two orthogonal directions passes through a polarization analyzer, the transmitted optical intensity varies. The output voltage from an optical detector located after the analyzer can be used to determine the roll angle. The chief advantages of the sensor are that it is compact, flexible, low cost, and power effective and provides a fast response. Most importantly, the sensor is insensitive to various fluctuations such as optical intensity, photodiode responsivity, and temperature and to vibrations. This performance is most advantageous in long-distance or long-term measurements. Experimental results have shown that the angular resolution is 0.01 degree in a +/-30 degree range.