Apparatus for measuring height position of workpiece held on chuck table and laser processing machine

摘要

PROBLEM TO BE SOLVED: To provide a height position measuring device for measuring a top surface position of a workpiece, and a laser processing machine.SOLUTION: A height position measuring device for a workpiece comprises: a light branching means which guides light from a light emission source to a first path and guides reflected light to a second path; an objective lens which guides parallel light formed by a collimation lens that converts light guided into the first path to parallel light, to the workpiece; a cylindrical reference optical length setting member which is disposed between the collimation lens and the objective lens, and is composed of a transparent body having a reflection mirror formed on the end surface of the objective lens side to expand an optical length; a diffraction grating which diffracts interference between reflected light that has been reflected by the reflection mirror and guided from the first light branching means to the second path and reflected light that has been reflected on the workpiece and guided from the first light branching means to the second path; and a control means which determines a distance from a surface of a chuck table to the top surface of the workpiece based on a detection signal from an image sensor for detecting an optical intensity of diffracted and reflected light in a predetermined wavelength region.