Patent ID: 7684032

Claim:
A method to detect a defect on or within a surface of a thin layer of material on an object, comprising: contemporaneously directing, onto the surface of the object, a radiation beam from a single source having at least a first component at a first wavelength and a second component at a second wavelength, different from the first wavelength; generating a first signal set from radiation at the first wavelength reflected from the surface by receiving a portion of the radiation at the first wavelength reflected in a first quadrant detector; generating a second signal set from radiation at the second wavelength reflected from the surface by receiving a portion of the radiation at the second wavelength reflected in a second quadrant detector; where the first quadrant detector and the second quadrant detector are separate detectors, and the first signal set and the second signal set are contemporaneously generated, and identifying the defect on or within the surface of the thin layer of material on said object from the first signal set and the second signal set.