Patent ID: 6882424

Claim:
An apparatus for evaluating the characteristics of a sample, comprising: an intensity modulated pump beam, said pump beam being directed to a first spot on the surface of the sample for periodically exciting the sample; a probe laser beam being directed to a second spot on the surface of the sample; a tracker module capable of adjusting a lateral displacement of said first and second spots on the surface of the sample; a fixed beam combiner for combining the pump beam and the probe beam; a common objective lens for focusing the pump and probe beams to the respective first and second spots on the sample; a detector for measuring a modulated power of the reflected probe laser beam and generating first output signals in response thereto; and a processor for signaling the tracker module to adjust the lateral displacement of said first and second spots, the processor further evaluating the characteristics of the sample based on the first output signals obtained for at least two different lateral displacements of the first and second spots.