DVD Physical Specifications
Dimensional Characteristics
Track geometry
In the Information Zone tracks are constituted by a 360 degree
turn of a spiral. The
track pitch shall be 0.74 µm ± 0.03 µm. The track pitch averaged over the Data
Zone shall be 0.74 µm ± 0,01 µm.
Track modes
Tracks can be recorded in two different modes called Parallel
Track Path (PTP) and Opposite Track Path (OTP).
In practice, the lengths of the Data
Zones of both layers are
independent from each other. Types
A and B shall be recorded in PTP mode only. Types
C and D may be recorded in either modes. In
PTP mode, tracks are read from the inside diameter of the Information Zone to
its outside diameter, this applies
to both Layer 0 and Layer 1 for Types C and D. On both layers,
the track spiral is turning from
the inside to the outside. In
OTP mode, tracks are read starting on Layer 0 at the inner diameter of the
Information Zone, continuing on Layer
1 from the outer diameter to the inner diameter. Thus, there is a Middle Zone at
the outer diameter on both layers. The track spiral is turning from the inside to the outside on
Layer 0 and in the reverse direction
on Layer 1. The radial
misalignment of the outer edge of the Information Zones between Layer 0 and
Layer 1 shall be 0.5 mm max.
In OTP mode, the radial misalignment
between the outer edge of the Data Zones of Layer 0 and Layer 1 shall be 0.5
mm max.
Channel bit length
The Information Zone shall be recorded in CLV mode. The Channel
bit length averaged over the Data Zone shall
be
 |
133.3 nm ± 1.4
nm for Type A and Type B, |
|
146.7 nm ± 1.5
nm for Type C and Type D |
Mechanical Parameters
Mass
The mass of the disk shall be in the range 13 g to 20 g.
Moment of inertia
The moment of inertia of the disk, relative to its rotation
axis, shall not exceed 0.040 gm2.
Dynamic imbalance
The dynamic imbalance of the disk, relative to its rotation
axis, shall not exceed 0.010 gm.
Sense of rotation
The sense of rotation of the disk shall be counterclockwise as
seen by the optical system.
Optical Parameters
Index of refraction
The index of refraction IR of the transparent substrate shall be
1.55 ± 0.10.
The index of refraction of the spacer shall be (IR ± 0.10).
Thickness of the transparent substrate
The thickness of the transparent substrate is specified as a
function of its index of refraction.
Thickness of the spacer of Types C and D
For Types C and D, the thickness of the spacer shall be 55
µm ± 15 µm.
On a disk, this thickness shall not vary by more
than 20 µm.
Within one revolution, it shall not vary by more than 8 µm.
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