Abstract: 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.

Abstract: In hardening with laser beam by irradiating laser beam. 29 on a workpiece 27, oscillating the laser beam so as to heat a workpiece with a hardening width W1, laser beam output in both end portions (times (1), (5), (6), (10) of FIG. 4, for instance) of amplitude of the laser beam is made lower than one of a center portion (times (3), (4), (7), (8) of FIG. 4, for instance) of the amplitude. Relative moving velocity of the laser beam with respect to workpiece is decreased, and the quantity of giving energy of the laser beam in both end portions of the amplitude where the density of giving energy of laser beam is high is decreased so as to equalize quantity of aiming energy in the whole hardening cycle. By doing so, a proper hardening action is possible.