Philips CDR880 - Mechanical Part and Control Systems; CD-Recording Drive Mechanics; CDM Mechanism Functions; 3-Spots Push Pull Tracking System

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BASICS CDR/RW
Note: the ATIP information on pregroove remains. Only by
diffracting the dye-layer new information is stored on “pit”
spots. As long as disc is not finalized the recorder is able to
read ATIP information.
To stop the recording the stop key has to be activated.
The writing continues to the next subcode sync and another
26 (EFM-)frames more. (See paragraph 2.5.5.6. General
linking rules.) First after recording those 26 frames the CD-R
drive stops recording in the data area of the disc.
Immediately, all stored information in the microprocessor, like
disc number and the number of registered tracks, will be
written down in the PMA of the disc. (See paragraph 3.2.2.2)
After that procedure the tray is allowed to bring the disc
outside the recorder.
To continue the recording on the same disc the close key has
to be activated. Now still there is no information on the lead-in
area but in the PMA the key identification information of the disc
has been found. For each new record a new OPC is made.
In this area itis possible to record only a maximum of 99
testrecordings.
However with the temporary table of contents in the PMA of
the disc, the microprocessor knows the last track and drives
the spot (Light Device Unit) to the end of that recorded track.
To link to that position the recorder looks for the last recorded
subcode sync framenumber. When the recording should start
the recorder starts reading at first the last 26 EFM-frames to
assure the timing of the registered signal with the timing of the
new recording signal. After those 26 EFM-frames the writing
starts. In this way there exists a continuous EFM pattern on
the disc which is adapted to the conventional standard.
For CD-R discs the Power Calibration Area (PCA) can only
record a maximum of 99 OPC testrecordings. To prevent that
to often loaded discs are full without any recording the last
(99th) OPC recording is used for all further recordings. So
user should prevent loading discs to often without making a
recording, to prevent misadjustments of OPC value.
The CD-RW disc does not have this limitation. After 99 OPC
records have been stored in the PCA at the next OPC at first
PCA will be erased and again 99 OPC values can be stored.
At the end ofthe recording the recorder operates in the same
way as already described. Before opening the tray it is
possible to decide that this recorded disc has been comple-
ted. Now the fixing up procedure (finalizing) may be activated.
Then all the content of the temporary table of contents (PMA)
is transferred to the lead-in area. Behind the last track the
lead-out information will be written. After the fixing up there is
not any possibility to make another recording on this
CD-Recordable Audio disc. But from now on the finalized
CD-R disc can be played back on every CD-Audio player.
Finalizing (fixing up) of a CD-ReWritable disc is done via the
same procedure, however with this restriction that only
CD-RW prepared CD-Audio players are able to play back this
finalized disc.
In the next section the mechanical actions to get the
information on and from the recording disc are described.
3.2 The Mechanical part with its control systems
In the mechanical part of the recorder the track following,
focusing and reading and writing of a disc are carried out.
All these actions are adapted to the new write and rewrite
situation and should be compatible with the conventional
CD-sysiem.
These conditions are fulfilled by the CD-Recording drive.
A very important item of this drive is the Light Device Unit.
This consists of the laserdiode with an optical 3-spots
lightpath. This Light Device Unit is driven and/or controlled by
the following electrical circuits:
- laser control,
- normailizer,
- focus control,
- 3-spot radial tracking system,
- motorcontrol.
All these functions are carried out in close co-operation with
the servo microcontroller.
3.2.1. The CD-Recording drive
In the mechanical part of the recorder the following conditions
are implemented.
- The spot follows the tracks very closely. Here has been
chosen for an adapted 3-spot system with a 2-stage radial
tracking slide mechanism.
- The mechanism is derived from the conventional
CD-system.
- Writing of the PMA and PCA is done on the inner track
before the lead-in. The spot has to be moved at 22 mm
radiation from the middle. This requires an adequate
functioning of objective, actuator and turntable motor.
The mechanical part of the CD-Recorder has to be
adapted to reach the new, most inside position.
- To getas much laserlight as possible on the disc, polari-
zing optics have been used. Also a couple of objectives
has been added and a high power laserdiode has been
applied.
- Tolerances of the tilting of the disc ask for adaption of the
real time optical power. This is controlled by the real time
Optical Power Control. (O.P.C.) See paragraph 3.2.2.2.
All these functions are implemented in the CD-Recording drive
which consists of the CDM mechanism and the electrical
circuitry which is concentrated on the CDM Board and on the
Main Board.
The CD-Recording drive with the Light Device Unit constitutes
an interface between the lightpath on the one hand and the
encoder and decoder on the other hand. See figure 16: CDR
drive blockdiagram.
PHILIPS
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