Inspection systems, circuits and methods are provided to enhance defect
detection by addressing anode saturation as a limiting factor of the
measurement detection range of a photomultiplier tube (PMT) detector. In
accordance with one embodiment of the invention, a method for inspecting
a specimen includes directing light to the specimen and detecting light
scattered from the specimen. The step of detecting may include monitoring
an anode current of the PMT detector, and detecting features, defects or
light scattering properties of the specimen using the anode current until
the anode current reaches a predetermined threshold. Thereafter, the
method may use a dynode current of the PMT for detecting the features,
defects or light scattering properties of the specimen.