Patent ID: 8657644
Filing Date: 2014-02-25
Classification: B24B

Abstract:
1. An eddy current sensor comprising: a sensor coil to be disposed near a metal film or a conductive film formed on a substrate; a signal source configured to supply an AC signal to said sensor coil to produce an eddy current in the metal film or the conductive film; and a detection circuit operable to detect the eddy current produced in the metal film or the conductive film on the basis of an output of said sensor coil; wherein said sensor coil comprises an oscillation coil connected to said signal source, a detection coil operable to detect the eddy current produced in the metal film or the conductive film, and a balancing coil connected in series to said detection coil; and said detection coil comprises a coil formed by a wire or a conductive material wound as a single row and plural layers, a row being defined as a direction perpendicular to the substrate and a layer being defined as a direction parallel to the substrate.