| 摘要 |
<P>PROBLEM TO BE SOLVED: To find an angle error when the scale center of a scale plate is eccentric to a rotary shaft, using a single angle detector, and to correct a measured angle, using the angle error. Ž<P>SOLUTION: A rotary encoder includes the scale plate 12 fixed onto the rotary shaft, a CCD linear image sensor 22 for capturing an image of a slit 18 group on the scale plate 12, and a computer 34 for computing the measured angle, based on an output from the CCD linear image sensor 22, for finding an angle error amount E based on the measured angle, and for accurately computing an angle, by correcting further the angle error amount E with respect to the measured angle. The rotary encoder finds coordinates P<SB>F</SB>of a foot F of a perpendicular 26 from an image of the scale center O<SB>1</SB>of the scale plate 12 to the CCD linear image sensor 22, based on the output from the CCD linear image sensor 22, every rotation of equal angle of the scale plate 12, and an angle Ar in the coordinates P<SB>F</SB>, also finds a plurality of sets of distances D from the image of the scale center O<SB>1</SB>to the CCD linear image sensor 22, and computes the angle error amount E, based on data of the plurality of sets, in the calculation of the angle error amount E. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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