Inspection systems, circuits, and methods are provided to enhance defect
detection by reducing thermal damage to large particles by dynamically
altering the incident laser beam power level supplied to the specimen
during a surface inspection scan. In one embodiment, an inspection system
includes an illumination subsystem for directing light to a specimen at a
first power level, a detection subsystem for detecting light scattered
from the specimen, and a power attenuator subsystem for dynamically
altering the power level directed to the specimen based on the scattered
light detected from the specimen. The power attenuator subsystem may
reduce the directed light to a second power level, which is lower than
the first, if the detected scattered light exceeds a predetermined
threshold level. The systems and methods described herein may also be
used to extend the measurement detection range of an inspection system by
providing a variable-power inspection system.