| 摘要 |
Apparatus for positioning a projected image in response to input signals corresponding to the components of the commanded position of the image along a pair of orthogonal axes. The apparatus employs a pair of servo loops that position a projector mechanism along the respective axes. In each loop position feedback is provided by a capacitive transducer. A dielectric member is disposed between a pair of planar electrodes and moves back and forth in correspondence with movement of the projector mechanism. Consequently the area of the plates covered by the dielectric member, and thus the capacitance of the transducer, corresponds to the position of the mechanism. The capacitance of the transducer is converted to a dc signal by incorporating the capacitance in a conversion circuit that emits a series of pulses whose duty cycle is proportional to the capacitance.
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