| 摘要 |
PURPOSE:To control highly stably and precisely the movement of a head without bad influences of contraction and skew of a recording material by controlling the head position by digital signal processing. CONSTITUTION:A detecting mechanism part 10 provided with a light emitting part 21 constituting a photo encoder together with an optical scale 9, half mirror 23, light receiving parts 27 and 28, etc. is moved in the radial direction of a disc in one body with the head. Interrupted pulses are generated from light receiving parts 27 and 28 in accordance with two optical spots passing the scale 9, and a clock pulse generating circuit 11 generates clocks different by 90 deg. in phase where lead and lag are inverted in accordance with the head moving direction. One or the other clock is counted up or down by a counter in accordance with the head moving direction until the counted value reaches a set value corresponding to a target position, and thus, a position error detecting potentiometer is not used to control the moving position of the head in the disc radial direction stably with high precision without bad influences of contraction and skew of the disc by digital processing. |
