| 摘要 |
PURPOSE:To detect a revolving speed of an information recording disk and to control exactly the revolving speed by providing slit parts by equal intervals extending over the whole circumference, on a part of the information recording disk, and detecting this slit by a noncontact system. CONSTITUTION:A slit part 52 provided on an information recording disk 50 is constituted by providing a part for making a light transmit and a nontransmitting part (reflecting part) to each other at equal intervals, and the number of slits constituted in one rotation of the disk 50 is supplied to a revolving speed controlling circuit part 30 from a photodetector 22, amplified by an amplifier 31, and also inputted as a pulse signal to a comparing circuit 34 through a differentiating circuit 32 and a monostable multivibrator 33. Said signal is compared with a reference signal from a reference signal generator 35 in said circuit, and a rotating motor 3 is driven so that its difference becomes zero. In this way, the revolving speed of the information recording disk 50 is controlled exactly. |
