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Description of Operation > Description of Newly Adapted Technology
3-2 Description of Newly Adapted Technology
3-2-1 Blu-ray
(*1)
Disc (BD)
(1) Overview of BD and Specifi cations
A Blu-ray disc (BD) is an optical disc whose format has been established by the Blue-ray Disc As-
sociation (BDA): Data is written and read using blue-purple laser.
A BD achieves a shorter track pitch by using a blue-purple laser with shorter wavelength and en-
hancing the NA value
(*2)
, as shown in the table below, enabling the storage capacity more than
fi
ve
times that of same-size DVD (single-sided, one layer).
*1: The logo “Blu-ray Disc” has no “e” following “Blu”.
*2: NA stands for numerical aperture, which is a value that shows how a lens focuses light.
The higher the NA value, the shorter the focal distance will be, so the thickness of light transmission
protective layer can be as small as 0.1 mm.
*3: The storage capacity on BD varies depending on the format and version. See Table 3-3-2 for details.
(2) Physical formats of discs
*4: BD-FS stands for Blu-ray disc
fi
le system: This recording format will improve the playback response.
The BD-FS format divides the disc recording area between "real-time data area" - where the stream of
video/audio, etc. is recorded - and the "gathered
fi
le area" - where the stream control database is
recorded, which improves the response.
Table 3-2-1 Comparison of Specifi cations between BD and DVD
Item
BD (single-sided, 1 layer)
DVD (single-sided, 1 layer)
Disc diameter
12cm
8cm
12cm
8cm
Storage capacity (GB)
25
(*3)
7.5
4.7
1.46
Laser wavelength (nm)
405
650
Lens NA value
(*2)
0.85
0.6
Track pitch (
μ
m)
0.32
0.74
Thickness of disc (mm)
1.2
1.2
Thickness of light transmission
protective layer (mm)
0.1
0.6
Table 3-2-2 List of Physical Formats of Discs
Format
Overview
Major version and characteristics
BD-RE
Rewritable up to 10,000
times
Ver. 1.0
Disc in cartridge
File format: BD-FS
(*4)
Storage capacity: 23.3 GB (12 cm, single-sided, 1 layer)
Ver. 2.1
Bare disc
File format: UDF2.5
Storage capacity: 25 GB (12 cm, single-sided, 1 layer)
BD-R
Recordable only once
Ver. 1.1
Bare disc
File format: UDF2.6
Storage capacity: 25 GB (12 cm, single-sided, 1 layer)
BD-ROM
Playback (read) only
Ver. 1.0
Bare disc
File format: UDF2.5
Storage capacity: 25 GB (12 cm, single-sided, 1 layer)
