Disc Identification - Sony DVP-NS300 Training Manual

In fifth generation DVD players, an ingenious Dynamic Tilt Correction (DTC) system replaces the tilt servo.
Warped disc readability is achieved by tilting the lens during focus correction. The greater the focus correction,
the more the tilt.
The DTC concept and mechanics are as follows:
The DVD disc information layer is at a height determined by the spindle motor hub. This is considered as the
mechanical focus center of the lens. As the optical block moves towards the outside of the disc, disc warp
increases. At the points where the disc is angled up by warp, the focus point also moves up to compensate.
Raising the focal point causes the lens to change its angle and remain perpendicular to the disc. Conversely,
when the disc angles down (Figure 1-2 B), the lens focus goes below center and the lens tilts in the opposite
direction.
Mechanically, DTC is achieved by modifying the lens supports. The front lens supports are stronger than the
rear. See Figure 1-4. As the lens moves up, it is tilted toward the weaker support. As it moves down, the lens is
tilted toward the stronger support. The tilt is always in the direction of the warpage so the lens remains perpendicular
to the disc.
Figure 1-4 - Lens
Retaining DTC System

Disc Identification

The DVD player first determines what type of disc is in the tray before playing it. The player powers up one of the
lasers and begins looking for the disc's information layer(s). The time it takes to find a layer determines how
deep the layer is inside the disc (T=0.6cm, 2T =1.2cm). Because the tracking servo is disabled at this time, the
lens will continue past the focus point of the DVC and look for a second information layer (DL disc). The disc ID
method is shown in Figure 1-5. This procedure is repeated with the second laser to insure identification of the
lower output –R and +RW discs.
Weak
Rear
Support
FIGURE 1-4 - DTC SYSTEM
Lens
5
Stronger
Front
Support
1. What's New?