| 摘要 |
PROBLEM TO BE SOLVED: To securely detect a sensor position without causing any read error even if an error due to dust, a flaw, etc., occurs to part of an absolute type rotary encoder and then to measure an angle with high reliability. SOLUTION: A control part normally obtains the output of code information in a 'center readout area'β1 on the center side of a 'readout object area'αwhich can be read by a CCD and calculates the current position of a sensor about the rotary encoder. If there is an error in the 'center readout area'β1, the part of a 'rear half readout area'β2 or 'front half readout area'β3 except the part of the error is used to detect the sensor position and the output signal from the part is used to calculate the current position of the sensor.
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