| 摘要 |
PURPOSE:To improve the measurement accuracy by deriving the light quantity distribution of a bright/dark level electrical signal from an output signal of a photoelectric detector, and setting the average detection output of the brightest part and the darkest part in a bright/dark intermediate area, as the end part of an object to be measured. CONSTITUTION:An image pickup means constituted of an optical lens and a photoelectric detector is placed in a position which faces a part to be measured of an object to be measured. In this state, by a bright/dark level electrical signal from the photoelectric detector, the light quantity distribution of a detection output corresponding to a detected position of the object to be measured is derived. Subsequently, from the light quantity distribution, a bright/dark intermediate area a3 is detected, and detection output values in the brightest part (a11) and the darkest part a22 in the area 13 are derived, respectively. Next, an average value P of two detection output values is calculated, and the detected position corresponding to a detector output of the average value is set as the end part, by which the accuracy for an optical position measurement can be improved.
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