Apparatus, systems, and methods for monitoring the processing of a workpiece that includes directing an incident laser beam onto the workpiece and using an optical detector for measuring a signal emitted from the workpiece as a result of the incident laser beam. The detector generates at least two signals based upon the optical signal. The method also involves use of a light source monitor in determining workpiece processing quality based upon the quotient of the two outputs as well as a magnitude of one of the two quotients.