Patent ID: 8633419

Claim:
A laser welding quality evaluation method which irradiates a laser light toward a welding portion and receives a reflected laser light from the welding portion through a protective glass that protects an optical system of a laser, images the welding portion using the received reflected laser light, and evaluates a welding quality using the welding image that is obtained by the imaging, the laser welding quality evaluation method comprising the steps of: obtaining a power monitoring image by imaging an irradiation board separately provided in place of the welding portion during power monitoring, which is a time when welding is not performed, using a reflected laser light from the irradiation board, the power monitoring image being obtained through the protective glass that protects the optical system of the laser; differentiating the power monitoring image from the welding image so as to obtain a difference processing reflected light image for evaluating the welding quality; and utilizing heat strain produced on the protective glass due to the same output of laser irradiation occurred both at the power monitoring and the welding to maintain and update reflected light images during the power monitoring as time series information, and obtaining the reflected light images through a difference processing based on the welding not influenced by the heat strain on the protective glass.