A workpiece is irradiated by a laser beam scanned in an oscillating track as
the
workpiece is advanced along a feed path in a hardening process. Sinusoidal variations
in scan velocity are offset by decreasing the laser beam power level at phases
in the scanning cycles corresponding to high and low scan displacement peaks, where
the scan velocity is least. The beam power is increased near the scanning center
line where the scan velocity is highest. The beam energy applied per unit of area
is thus equalized over the scanning cycle. The workpiece temperature can be sampled
at regular phases by a non-contact temperature sensor in the optical path, and
used to control beam power versus phase in a subsequent scanning cycle. Alternatively
or in addition, a sinusoidal beam power pattern can be stored and used to offset
scan velocity variations as a function of phase.
