| 摘要 |
An apparatus for determining the rotational position of a shaft comprises opposed first and second disks mounted for relative rotation about a predefined axis, with one of the disks being mounted to the shaft for rotation therewith and the other of the disks being maintained in a reference position. First and second rows of spaced apertures are provided on each disk, which lie in concentric paths of different radial distance from the predefined axis, the first rows being at the same radial distance from the axis and second rows being at the same radial distance from the axis. These apertures are positioned so that apertures of the first rows move into alignment while apertures of the second rows move out of alignment as the disks are rotated relative to each other. A first beam of light of predetermined intensity is oriented so as to intersect the paths of the first rows of apertures, and a second beam of light of predetermined intensity is oriented so as to intersect the paths of the second rows of apertures. First and second photosensors are aligned respectively with the first and second beams of light, and the photosensors are positioned so that the disks are in front of the respective photosensor for each light beam. Each photosensor provides an electric output signal relative to the intensity of light sensed by it and the two output signals are differentially processed to provide an orientation signal representative of the relative rotational position of the disks.
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