SCD-1, SCD-777ES - Sony Audio Service Manual (repair manual). Page 12

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V

TE

FD

The laser for SACDs is emitted and the existence of the HD layer (layer near the center of the disc) detected from the reflected light. At the

time of detection, the sled motor is rotated and detection is completed from the disc’s innermost to the middle part. The spindle motor is not
rotated at this time. When detection has terminated, the sled motor is rotated in reverse and returned to a position where the disc’s innermost
part can be played.

The focus drive (FD) signal that drives the focus coil and the PI signal that the disc’s reflected light generates are used in detection. The

PI signal is created from the RF signal and is output in proportion to the disc’s quantity of reflected light. Based on these signal inputs, disc
type is judged using the microprocessor (IC701).

The distance from the side of the disc that reads the signals to the HD layer is approximately 0.6mm, and the distance to the CD layer is

approximately 1.2mm. When the objective lens is raised in accordance with the focus search operation, it will first focus on the surface of the
disc, and reflected light will be detected. If the lens is move, it will focus on the HD layer in the center of the disc, and reflected light will be
detected. Lastly, it will focus on the CD layer directly on back of the labeled side, and reflected light will be detected.

In keeping, the HD layer can be detected using “T,” which is the time the disc’s surface reflection has been detected to the time the next

reflected surface is detected. If “T” is shorter than the fixed time, the judgment will be “HD layer exists.” If “T” is longer, the judgment will
be “No HD layer exists.”

All SACDs (SLs, DLs and hybrids) have an HD layer. Dual-layer discs have two HD layers near the center of the disc; as the interval

between them is extremely narrow, they will be detected similarly to a single layer.

As DVDs, DVD-ROMs and the like also have an HD layer in the center of the disc, it will be detected as “HD layer exists.”

The laser for CDs is emitted and the existence of the HD layer (layer on the back of the disc’s labeled side) detected from the reflected

light. During the detection process, the sled motor is rotated, and detection is completed while it moves from the disc’s innermost to the
middle part. At this time, the sled motor rotates at a constant speed.

The focus drive (FD) signal that drives the focus coil and the tracking error (TE) signal for tracking control are used in detection. The TE

signal is proportional to the disc’s quantity of reflected light. From these signal inputs, disc type is judged using the microprocessor (IC701).

When the laser for CDs is used, TE output from the HD layer cannot be sufficiently read. If the disc has a CD layer, sufficient TE output

can be read. In keeping, if TE output level “V” exceeds a fixed level, the judgment will be “CD layer exists.” If it does not, the judgment will
be “No CD layer exists.”

T

T

T: Short  -> HD

T: Long  -> CD

PI

FD

PI