Patent ID: 7671982

Claim:
A circuit for dynamically controlling a power level of light supplied to a specimen during a surface inspection scan of the specimen, the circuit comprising: means for dynamically altering the power level of the light supplied to the specimen; and means for controlling the dynamic alteration of the power level based on a calculated amount of scattered light detected from the specimen, wherein the means for controlling the dynamic alteration comprise: a photodetector for detecting the light scattered from the specimen and for converting the detected scattered light into an electrical output signal; a comparator for comparing the electrical output signal to a predetermined threshold level and for generating a control signal in response thereto; and a divider coupled between the photodetector and the comparator, wherein the divider is configured for generating a normalized version of the electrical output signal, the normalized version equivalent to the calculated amount of scattered light detected from the specimen, and wherein the comparator is configured for comparing the normalized version of the electrical output signal to the predetermined threshold level and for generating the control signal in response thereto.