| 摘要 |
To provide control signals allowing compensation of stylus tracking in eccentric grooves of a video disc 10, a stylus 11 carries an electrode 13 disposed between first and second electrodes 14, 15 fixedly mounted on a motor driven carriage 8 to which stylus 11 is compliantly mounted. The capacitances of the variable capacitors thus formed vary with the displacement of electrode 13, and hence of stylus 11, relative to carriage 8. In Figure 1, complementary a.c. signals V1, V2 are applied to electrodes 14, 15 so that the algebraic sum of these signals capacitively coupled to electrode 13 is indicative of the position of the stylus. The output signal V3 from electrode 13, via processing circuit 29, controls a motor 31 to move carriage 8 so as to restore electrode 13, and thus the stylus 11, to a null position. In Figure 8 (not shown), an a.c. signal which has been amplitude modulated by voltage variable impedances is applied to the first and second electrodes whereby the time average of the signal summed at the stylus related electrode is indicative of the stylus position. <IMAGE> |
