Patent ID: 8378257

Claim:
A laser processing apparatus comprising: holding means for holding a workpiece; processing laser beam applying means for applying a processing laser beam to said workpiece held by said holding means; a first focusing lens for focusing said processing laser beam to be applied to said workpiece; lens moving means for moving said first focusing lens in a direction perpendicular to a holding surface of said holding means; detecting means including a white light source for emitting white light, a second focusing lens for focusing said white light to said workpiece held by said holding means, a first optical fiber for guiding said white light emitted from said white light source to said second focusing lens, a detector for detecting the intensity of reflected light due to said white light focused by said second focusing lens and reflected on said workpiece, and a second optical fiber for guiding said reflected light to said detector; and control means for obtaining information on the surface of said workpiece according to the result of detection by said detector and controlling the operation of said laser processing apparatus by using said information, wherein: said detector includes a beam splitter for splitting said reflected light guided by said second optical fiber into a first light beam traveling in a first optical path and a second light beam traveling in a second optical path, a light intensity sensor for detecting the light intensity of said first light beam, a detecting diffraction grating for converting said second light beam into detecting diffracted light, and a wavelength-specific light intensity sensor for detecting the light intensity, according to the wavelengths, of said detecting diffracted light guided to said second optical path and converted by said detecting diffraction grating; and said control means obtains edge position information on said workpiece according to the result of detection by said light intensity sensor and obtains height information on said workpiece according to the result of detection by said wavelength-specific light intensity sensor by referring to a control map preliminarily stored in a memory for setting the relation between the focal length of each wavelength component and the surface height of said workpiece.