| 摘要 |
PURPOSE:To attain a high resolving power by a method wherein a first or second signal from each set of detectors for absolute signals totaling (n) sets each comprising two detectors is selected in accordance with the state of a binary signal delivered from a detector for an incremental signal. CONSTITUTION:A code plate 11 is provided with a track 13 having an absolute pattern and with a track 15 having an incremental pattern, the two tracks being parallel to each other. A detecting element 20 has photodiodes (PD) 21a, 21b to 24a, 24b are detectors for absolute signals and PD 25 as a detector for an incremental signal. A light being applied from above the code plate 11, the absolute pattern of the track 13 is detected on the side of the lower surface of the code plate 11 by the PDs 21a, 21b to 24a, 24b, while the incremental pattern of the track 15 is detected by the PD 25. A signal processing element 30 outputs a pulse train formed by a buffer circuit to output terminals 61 to 64 when a binary signal from a comparator is at a low level, and outputs a pulse train formed by the PDs 21b to 24b to the terminals 61 to 64 when the binary signal is at a high level. |
