Miniature magneto-optic angular position sensor

This Letter describes a miniature Fabry-Perot, contactless, magneto-optic sensor for angular position measurement. The sensor utilizes a magneto-optic fluid comprising bar-ium hexaferrite nanoplatelets that become birefringent in the presence of an external magnetic field and a compact fiber-optic sensor system for tracking the liquid's optical axis direction. An efficient temperature compensation sys-tem is provided which allows the use of otherwise highly temperature-sensitive magneto-optic liquids. An unambigu-ous measurement range of 90 degrees and a resolution of better than 0.05 degrees are demonstrated experimentally.