| 摘要 |
PROBLEM TO BE SOLVED: To improve measurement accuracy by reducing an measurement error caused by variation of intensity of a measuring light beam or the like, in a measurement device used for detecting a position of a dark line by comparing light detection signals detected by a plurality of light receiving elements by using outputs of every two adjacent light receiving elements. SOLUTION: A light beam 13 totally reflected from an interface 10b is detected by a photodiode array 17, and the output of each photodiode is inputted to a differential amplifier array 18. When it is assumed that two light detection signals inputted to each differential amplifier are A and B, respectively, a signal of B-A/B is outputted from the differential amplifier in a region satisfying B-A<0, and a signal of B-A/A is outputted from the differential amplifier in a region satisfying B-A>0, and thus the dependency on the intensity or the like of the measuring light beam is eliminated. COPYRIGHT: (C)2004,JPO
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