Sharp DV-500D Technical Manual page 21

4. Spindle Servo
Rotate the disc under Constant Linear Velocity (CLV).
Control is necessary to make quick invariable line speed when making a pick-up move when
in the seek mode.
Invariable rotation on MO/HD a For making faster access
CLV
5. Automatic Power Control (APC)
On laser, the amount of light being emitted changes greatly, even when the running electric
current only varies slightly. Therefore, the amount of omitted light is detected on the Photo
Detector in order to monitor and control the stability of the laser current.
4-2 How to Make the Error Signal
1. Optical System of Hologram Pick-Up
OL
Raised Mirror
a For changing the disc rotation speed depending on the
pick-up position (faster on the interior side (1400rpm)
and slower on the exterior side (580rpm))
Pa
LD PD
(monitor)
Disc
Signal Layer
CL (Collimator Lens) ··· Making parallel light
21
i
PD
Laser
Hologram··· Leading the reflection light
from the disc to the targeted PD
DVD-Series
I/V
Signal
Conversion
Monitor PD ··· Adjusting the
amount of light
emitted by laser