Sony dvp-s530d User Manual

Focus

Mechanical focus of the laser beam on the information layer of the disc is
accomplished by moving the laser’s objective (final) lens closer to or away
from the disc. Applying a current to a coil that is attached to the lens
controls the lens position. When the lens moves up and down, so does its
corresponding focus point at the disc area. Focus is found when the
laser’s focus point rests on the information layer of the disc.

Search

There is a large and a small lens movement associated with focus. The
large up and down lens movement is used to locate a disc by moving the
focus point until it finds the disc layer. This large lens movement is called
focus search and can be seen by observing the lens after the tray moves
in.

Focus search employs five ICs and the focus coil. System Control IC202
initiates focus search by sending data to IC701 which makes voltage to
move the lens. The results of the search are sent as data from IC701
back to IC202 on the parallel bus so a stop search command from IC202
can follow. Details of the IC202 and IC701 bi-directional communications
are explained later.

Focus Search Devices

Device

Purpose

System Control IC202

Retrieves and acts on the focus search
program stored in memory

EEProm Memory IC201

Stores focus search sequence

HGA IC601

Expansion port for IC202

Servo IC701

•

Translates digital commands to

analog focus coil voltages

•

Identifies disc’s layer using IC001

Driver IC801

Voltage to current coil driver

Focus coil

Moves objective lens

RF Amp IC001

Feedback to electrically identify focus

Focus Search End – Disc Identification

Focus search concludes when focus is found or when the search cycle is
over and no disc was found. Using A to D laser diode signals from the
optical base unit electrically identifies the mechanical focus on the disc
layer. RF Amp IC001 combines them to output PI (pin 29) and FE (pin
40) signals. Both are needed to find the focus position and stop focus
search. PI identifies a disc when the signal goes high. FE identifies the
focus position as this line rises and crosses 1.8V on the way down during
search.

Once the focus position has been found, the lens search operation ends
and the servo operation begins. IC701 makes the crossover by informing
System Control IC202 the disc layer has been found when FCSON from
IC701/pin 39 goes high. It remains high as long as focus is maintained by
servo IC701.

Servo

Once the disc layer is found during focus search, smaller lens move-
ments maintain focus as the disc is spun during playback. The focus
servo uses three ICs to provide small correction voltages to the focus coil:

Focus Servo Devices