| 摘要 |
Apparatus recording information about angular motion of a rotatable disk (16). The disk (16) has regions with differing properties with aspect to electromagnetic energy. The apparatus includes first means (12) emitting a first sequence of electromagnetic energy pulses in a first direction toward the disk. The first emitting means are adjacent a first side of the disk. The apparatus also includes second means (12) emitting a second sequence of electromagnetic energy pulses is a second direction toward the disk, the second emitting means also being adjacent the first side of the disk. The first and second sequences of electromagnetic energy pulses reflect from the first side of the disk in different areas, the areas being separated in the direction of rotation of the disk. Photosensitive means (14) receive the electromagnetic energy pulses from both the first and second emitting means at a single point and generate a signal in response to the received electromagnetic energy pulses. A controller (U3) processes the signal to determine the number of rotations of the disk, and the direction of rotation of the disk.
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