| 摘要 |
In the appts measuring the relative angle of rotation of body (17), the axis (4) coincides with the axis of rotation of the body (17). A light source (10) is mounted on axis (4) and its light is reflected by mirror (14), through lens (19), as light beam (18), and on to mirror (15), which is fixed to the body (17) by holder (16). The reflected light beam (20) enters lens (21) and is reflected by a second mirror (22) along axis (4) and falls on detector (23) as a light spot. If the light spot does not fall in the exact centre of detector (23), it is detected by a feedback coupling (24) to the motor (7) that turns holder (3) with the associated components until the light beam (18) is aligned to mirror (15) and thus follows the movement of body (17). the corresponding angle is sensed by the angle detector (8).
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