An optical inspection system rapidly evaluates a substrate by illumination
of an area of a substrate larger than a diffraction-limited spot using a
coherent laser beam by breaking temporal or spatial coherence. Picosecond
or femtosecond pulses from a modelocked laser source are split into a
plurality of spatially separated beamlets that are temporally and/or
frequency dispersed, and then focused onto a plurality of spots on the
substrate. Adjacent spots, which can overlap by up to about 60-70
percent, are illuminated at different times, or at different frequencies,
and do not produce mutually interfering coherence effects. Bright-field
and dark-field detection schemes are used in various combinations in
different embodiments of the system.