Surface position detector and laser beam processing machine

摘要

A surface position detector (9) for detecting the position of an exposed portion of a workpiece held on a chuck table, wherein a detection laser beam (LBI) is applied to the exposed portion of the workpiece, its reflected light is received by a first light receiving device (96) and a second light receiving device (97), and the ratio of the quantity of light received by the first light receiving device (96) to the quantity of light received by the second light receiving device (97) is calculated to obtain the height position of the exposed portion of the workpiece.