Absolute-value encoder device

摘要

An absolute-value encoder device for detecting a plurality of rotation quantities is disclosed. An A/B phase forming portion 610 forms an A-phase pulse signal and a B-phase pulse signal, based on light passing through a slit rotating together with a rotary shaft. One period of each of those pulse signals corresponds to one revolution of a rotary shaft. The A- and B-phase pulse signals are displaced in phase by 90° from each other. When an A/B-phase state detecting portion 640 detects a state change of each of those pulse signals, a clock forming portion 66 changes a frequency of a clock pulse signal to another frequency.