Sharp DV-500D Technical Manual

21DVD-Series4. Spindle Servol Rotate the disc under Constant Linear Velocity (CLV).l Control is necessary to make quick invariable line speed when making a pick-up move whenin the seek mode.Invariable rotation on MO/HD a For making faster accessCLV a For changing the disc rotation speed depending on thepick-up position (faster on the interior side (1400rpm)and slower on the exterior side (580rpm))5. Automatic Power Control (APC)l On laser, the amount of light being emitted changes greatly, even when the running electriccurrent only varies slightly. Therefore, the amount of omitted light is detected on the PhotoDetector in order to monitor and control the stability of the laser current.4-2 How to Make the Error Signal1. Optical System of Hologram Pick-UpLD PD(monitor)PaiI/VConversion SignalMonitor PD ··· Adjusting theamount of lightemitted by laserLaserHologram··· Leading the reflection lightfrom the disc to the targeted PDDiscSignal LayerCL (Collimator Lens) ··· Making parallel lightOLRaised MirrorPD