| 摘要 |
PURPOSE:To obtain only an electrical signal of a reflected light component from a body to be detected by correcting the detection output of scattered or regular reflected light from the body to be detected based on the quantity of light of an emitter or the detection output of its variation. CONSTITUTION:Outgoing light from a laser and the reflected light (the scattered light or regular reflected light) from a silicon wafer are detected by silicon photodetectors 3, 7 respectively and both the detection outputs are amplified by amplifiers 13, 14 and inputted to an arithmetic circuit 15. Then, the output of the amplifier 13 is subtracted from the output of the amplifier 14 and inputted to a binarization circuit 17. Then, in the circuit 17, a pattern signal from the circuit 15 is binary coded by the output of a reference voltage generating circuit 16 and the position of the pattern is measured with high accuracy by a counting circuit 18. |
