| 摘要 |
An encoder which can detect absolute angle precisely even if the irradiating position of detected light on a scale is shifted from a reference. In the encoder (1), a bright part (19) irradiated with the detected light is formed in a region including the semi-circle portions of arrangement lines (L1, L2) out of a scale plate (11) by passing the detected light through a rotary plate (8) with a gear in which a semicircular opening (17) is formed, and a dark part (20) not irradiated with the detected light is formed in the region excepting the bright part (19). Consequently, the encoder (1) can detect the absolute angle of a measurement object precisely even if the irradiating position of detected light on the scale plate (11) is shifted from the reference by controlling a correction amount based on the difference alpha° between an angular range corresponding to the half value width W of light intensity waveform P and a reference angular range when the angle is detected.
|
