Patent ID: 6961133

Claim:
An apparatus for use in measuring a thickness of a layer, comprising: a light source configured to generate a light beam; a light beam detector configured to detect at least a portion of the light beam reflected; an eddy current field generator configured to induce an eddy current; an eddy current detector configured to detect the induced eddy current; a processor coupled with the light source, the light detector, the eddy current field generator and the eddy current detector, wherein the processor is configured to control the light detector, the eddy current field generator and the eddy current detector; the light source is further configured to sweep the light beam across a first surface; the light beam detector detects the portion of the light beam reflected from the first surface as the beam is swept across the first surface; and the processor is configured to determine a radial characteristic of the portion of a first surface over which the light beam is swept, determine a scaling factor based on the radial characteristic that is applied to a first distance relative to the detected eddy current to determine a scaled first distance, and to determine a thickness based on a second distance relative to the first surface and the scaled first distance.