DEVICE FOR DETECTING HEIGHT POSITION OF WORKPIECE HELD ON CHUCK TABLE

摘要

PROBLEM TO BE SOLVED: To surely detect the height position of an upper face of a workpiece held on a chuck table even when the workpiece formed with a material having transparency exists.

SOLUTION: A device for detecting the height position of the workpiece held on the chuck table includes: a laser beam oscillation means; an annular spot forming means for annularly forming a spot shape of a laser beam; a first beam splitter for guiding the laser beam formed annularly to a first route; a condenser for irradiating the workpiece by condensing the laser beam; a pinhole mask disposed in a second route dividing the laser beam reflected on the workpiece with the first beam splitter; a second beam splitter for dividing a reflective beam passing the pinhole mask into a third route and a fourth route; a first light receiving element for receiving the reflective beam divided into the third route; and a means for regulating a light receiving region of the reflective beam divided into the fourth route and a second light receiving element. The device obtains the height position of the upper face of the workpiece based on a ratio of a light amount received by the first light receiving element and a light amount received by the second light receiving element.

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