Focus detection unit and optical measuring instrument having the same

摘要

A focus detection unit being applicable to various workpiece and capable of reducing production cost and an optical measuring instrument having the focus detection unit are provided. The focus detection unit is for forming image of first focusing pattern and second focusing pattern onto an image surface of an optical system, projecting the image onto the workpiece, and adjusting relative position of the first focusing pattern and the second focusing pattern for focusing, the focus detection unit including: a slide plate having a plurality of pair of the first focusing pattern and the second focusing pattern; a switching member for switching the slide plate to project the image of either one of the first focusing patterns and the second pattern corresponding thereto onto the workpiece; and a projector for projecting the image of the focusing patterns switched by the switching member onto the workpiece.