Abstract: The present invention provides a method and apparatus for use in measuring a thickness of a layer and/or variations in layer thickness for layers that are flat, curved or have curves. The apparatus comprises a light source to generate a light beam, a light beam detector to detect at least a portion of the light beam reflected, an eddy current field generator that induces an eddy current, an eddy current detector to detect the induced eddy current and a processor coupled with the light source, light detector, eddy current field generator and eddy current detector, wherein the processor controls the light detector, eddy current field generator and eddy current detector. A radial characteristic of a region of the surface can be determined, a scaling factor can be determined based on the radial characteristic and a measured distance can be scaled based on the scaling factor in determining a thickness.