Patent ID: 9031399
Filing Date: 2015-05-12
Classification: F21K,G02B

Abstract:
1. An autofocus mechanism, comprising: an objective lens that collects a laser beam to irradiate a measurement workpiece therewith; a beam splitter that splits light reflected from the measurement workpiece through the objective lens; a first light amount restricting element disposed in front of a focal position of one split beam of the reflected light; a first light-receiving element that receives the reflected beam having passed through the first light amount restricting element; a second light amount restricting element disposed behind a focal position of the other split beam of the reflected light; a second light-receiving element that receives the reflected beam having passed through the second light amount restricting element; and a processing unit that converts signals output from the first and second light-receiving elements into an A_signal voltage and a B_signal voltage, respectively, so as to determine an A+B_signal voltage and an S_signal voltage, which are expressed by Equations (1) and (2) below, wherein the processing unit includes: