Contactless hybrid sensor for simultaneous detection of light reflectance and eddy currents

We demonstrate a contactless hybrid sensor for the simultaneous detection of light reflectance and eddy currents. The sensor is based on combining an optical system with an RLC self-resonator, wherein the reflected light intensity and resonance frequency are measured. We demonstrate that the hybrid sensor can be used for monitoring metals coated with non-metallic films. Whereas the self-resonator can efficiently distinguish between metals and non-metals, the optical subsystem is sensitive to changes in the reflectance of light. A systematic investigation of the detector response as a function of distance to the material under test is undertaken to characterize its behavior.

► A hybrid sensor for monitoring coated metals is proposed.
► The sensor combines eddy current and optical reflectance measurements.
► Resonance frequency measurements show submillimeter position sensitivity.
► Optical reflectance measurements show a weak position sensitivity.