| 摘要 |
PURPOSE:To perform tracking at a high speed and with high precision, by counting a pulse signal obtained from a revolving high-density recording disk by a pickup, and converting the pulse signal into an analog value by means of two converters, then performing both rough and fine retrieving servo controls. CONSTITUTION:A laser light 8 is formed into an image on a disk 1 via a lens 7, a half mirror 6 and a lens 5, and this reflected light is fed to a pulse generator 1 through a lens 5 and a half mirror 6 to obtain a servo driving pulse. This pulse is usually fed to an up-down counter 12 to undergo a D/A conversion 14. Then a fine retrieving servo control 17 is driven with an analog signal. When the following distance of the servo 17 increases, a carry signal is delivered from the counter 12. Then a rough retrieving servo control 16 is driven via an up- down counter 13 and a D/A converter 15. This ensures a high-speed shift of a pickup as well as the precise tracking. |
