Sony RDR-GX7 - Manual (Page 31)

Newly developed Dual Drive
The RDR-GX7 is equipped with Sony's newly developed Dual
Drive. It represents the heart of dual RW recording capability,
assuring precise control for the write strategy (including laser
power) of many different kinds of media. The result is highly
stable recording with a low error rate. This performance
contributes to a large improvement in compatibility, which is the
most important fundamental factor in DVD recording. In
addition, the drive also assures highly stable reading of the large
variety of discs which are compatible with the RDR-GX7,
including DVD+R, DVD-Video software, music CDs, and CD-
R/RW discs.
■ DVD beam shape adjustment
for more stable recording
The light beam emitted from the laser diode, when viewed in
cross-section, is actually oval in shape. If light in this oval shape
is sent through the lens and projected onto the disc surface, its
ability to read and record is reduced. In reality, a light beam that
is round in shape provides ideal performance. Therefore, in order
to change the shape of the beam from oval to round, it is
refracted through an anamorphic prism. This prism has the
unique characteristic of enlarging or reducing the beam in only
one direction, but does not make any change in other directions.
By carefully adjusting the angle of the prism to the input beam,
the shape of the beam can be changed. This anamorphic prism
system has been adopted in the RDR-GX7 to achieve highly
stable recording characteristics.
■ Discrete optical pickup systems for DVD and CD
In order to handle two different types of disc media, DVD and
CD, two different approaches can be taken. Different objective
lenses can be used in the optical pickup, or an optical pickup for
both applications can be used. In the RDR-GX7, a special
objective lens which changes the aperture ratio between DVD
and CD operation is employed. Behind the lens, however,
discrete optical pathways for DVD and CD are constructed in an
optimum, yet extravagant, design execution. As a result, highly
stable pickup to suit the characteristics of each type of disc is
assured.
■ High mount insulators
When DVD and CD optical discs are manufactured, they emerge
with extremely minute irregularities, which are unavoidable.
Even irregularities which are within the DVD specifications of
0.010 g/m can result in the generation of resonance when the disc
is rotated at high speeds. This resonance can disturb both
tracking and focus operations, causing a deterioration in
performance. To minimize this resonance, Base Unit Insulators
are normally employed. In the RDR-GX7, base unit insulators
are mounted as close as possible to the disc in a high mount
insulator design. Special holes have been made in the disc tray to
enable the mounting screws for the mechanism to be as thin as
possible to assure low resonance. Thus, resonance is minimized
as close to the source as possible.
Chapter 4-6
Drive and
Deck mechanism
New technology adopted
in the optical pickup,
drive and deck mechanism
RDR-GX7 Technical Notes
31
The Dual Drive
Mechanism
in the RDR-GX7
Output beam shape
anamorphic prism
Input beam shape
Beam shape changed by the anamorphic prism
This prism can enlarge or reduce the beam in only one direction, but does
not change beam dimensions in any other direction. By changing the angle
of the prism in relation to the beam, the shape of the beam can be changed.
This enables the shape of the beam to be easily changed from oval to
round.
Objective lens
CD PDIC
Disc
Beam splitter
Beam splitter
DVD PDIC
CD laser
anamorphic prism
DVD laser
Discrete optical pickup systems for DVD and CD