Method for monitoring laser welding process, monitoring device and laser welding device

The invention relates to a method for monitoring a laser welding process for welding two workpieces (102, 104) by means of a welding laser beam (108) which interacts with the workpieces (102, 104) in an interaction region (114) in order to form a weld seam, a measuring beam (128) of an optical coherence tomography scanner (126) is directed to the interaction region (114) in order to acquire a measured value, the measuring beam (128) at least partially penetrating the workpiece (102, 104) in the interaction region (114) and the measuring beam (128) penetrating the workpiece (102, 104) hitting the workpiece (102, 104) in contact with the workpiece (102, 104) when the workpiece (102, 104) is subjected to through welding, and the measuring beam (128) of the optical coherence tomography scanner (126) at least partially penetrates the workpiece (102, 104) in the interaction region (114). A reference element (134) spaced apart from the plurality of reference elements (104, 104); defining a first measured value range