| 摘要 |
<p>An optical encoder has an optically-encoded plate 1 having parallel tracks 11, 12, 13, each comprising alternate opaque, reflective regions 111, 112, 124, 131, 133, 135, 137 and transparent, non-reflective regions 112, 121, 123, 132, 134, 136, 138 which differ in length between the tracks. LED's 21, 22, 23 direct radiation onto one side of each track 11, 12, 13. Detectors 24, 25, 26 located on one side of the plate 1 provide an output in response to radiation reflected from the reflective regions of each track; detectors 34, 35, 36 located on the opposite side of the plate 1 provide an output in response to radiation transmitted through the transparent regions. The outputs from the detectors are normally complementary. A processor 4 detects any loss of complementarity and determines the position of the plate close to the boundary between adjacent regions by comparing the detector outputs as one falls and the other rises.</p> |
