Multibeam optical disk readout method and apparatus

Details Multibeam optical disk readout method and apparatus Multibeam optical disk readout method and apparatus

2000-04-13

2002-04-16

Dinh, Tan (Department: 2651)

Dynamic information storage or retrieval

Information location or remote operator actuated control

Selective addressing of storage medium

C369S044370

Reexamination Certificate

active

06373793

ABSTRACT:

TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical disk readout method and optical disk readout system, and in particular, to an optical disk readout method and optical disk readout system configured such that separate light beams simultaneously illuminate each of the multiple adjacent tracks of an optical disk in which tracks are formed in a spiral (e.g. CD-ROM, CD-WO, DVD, DVD-ROM, or DVD-RAM disk), and wherein data recorded in the tracks being illuminated by the beams is read from the detected output of each returned beam by a record data readout system.
RELATED ART
One technique available as a method for reading recorded data from CD-ROM at high speed is the multi-beam technique. This multi-beam technique is disclosed in U.S. Pat. No. 5,457,670 and PCT Gazette WO94/19797 (PCT/US94/01790). In this technique, separate light beams simultaneously illuminate each of the multiple adjacent tracks of an optical disk on which the tracks are formed in a spiral. Data recorded in the tracks illuminated by the beams is simultaneously read-back from the detected output of each returned beam by a record data readout system in a manner such that there will be no duplications or gaps in the data being read back, and such that the data will be output in the sequence in which it was recorded.
Such a multi-beam optical disk (CD-ROM) readout method will be described with reference to FIG.
20
. Item
1
is a CD-ROM as seen from the signal side (optical pickup side), on which tracks in which data has been recorded are formed in a spiral with the outside diameter (outer circumference) of the tracks shown at the top of
FIG. 20
, and the inside diameter (inner circumference) at the bottom. Item
2
is an optical pickup capable of emitting five light beams. When reading, the optical pickup
2
is in a state of relative rotation with respect to the CD-ROM
1
, gradually moving from the inside of the disk toward the circumference as it advances, reading the recorded data as proceeds. Now, when the optical pickup
2
arrives at position I and starts reading data, the tracks × through (x+4) are separately illuminated simultaneously by the light beams
3
1
-
3
5
, respectively. The data recorded in each of the tracks illuminated by the beams
3
1
-
3
5
is simultaneously read from the detected output of each of the returned beams by the prescribed record data readout system, and the data recorded on the CD-ROM
1
is output serially in the sequence in which it was recorded, with no duplications or gaps.
The recorded data of CD-ROM
1
is structured in accordance with a CD signal format in sub-code Q-channel A-time (absolute time) frame units, where one frame={fraction (1/75)} second. Hereinafter, A-times are expressed in the form aa:bb:cc, where aa=seconds, bb=minutes, and cc=frames. If the optical pickup
2
were to start reading data from position I of
FIG. 20
, then
the light beam
3
1
channel would start reading recorded data correctly from the A-time=23:40:60 portion;
the light beam
3
2
channel would start reading recorded data correctly from the A-time=23:41:00 portion;
the light beam
3
3
channel would start reading recorded data correctly from the A-time=23:41:15 portion;
the light beam
3
4
channel would start reading recorded data correctly from the A-time=23:41:30 portion; and
the light beam
3
5
channel would start reading recorded data correctly from the A-time=23:41:45 portion.
By the time the CD-ROM
1
completes approximately (slightly more than) one revolution, advancing the optical pickup
2
to position II of
FIG. 20
(where tracks (x+1)-(x+5) are illuminated by light beams
3
1
-
3
5
respectively,
the light beam
3
1
channel will have read the recorded data correctly up to A-time=23:40:74;
the light beam
3
2
channel will have read the recorded data correctly up to A-time=23:41:14;
the light beam
3
3
channel will have read the recorded data correctly up to A-time=23:41:29; and
the light beam
3
4
channel will have read the recorded data correctly up to A-time=23:41:44;
with the gaps between the data read separately by the light beams
3
1
-
3
5
now filled. (By this time, light beam
3
5
will have read the recorded data correctly up to A-time =23:41:59.) The data read by light beams
3
1
-
3
5
is then output from the system in the sequence in which it was recorded, such that no duplications occur.(No frame is output more than once.)
When the optical pickup
2
has read data as far as position II in
FIG. 20
, the light pickup
2
is “track-jumped” forward (outward from the center of the CD-ROM
1
) by three tracks. This puts the light pickup
2
in position III of
FIG. 20
(where light beams
3
1
through
3
5
now illuminate tracks (x+4) through (x+8), respectively). At that point, the read operation then begins again, with
the light beam
3
1
channel reading recorded data correctly from the A-time=23:41:48 portion;
the light beam
3
2
channel reading recorded data correctly from the A-time=23:41:63 portion;
the light beam
3
3
channel reading recorded data correctly from the A-time=23:42:03 portion;
the light beam
3
4
channel reading recorded data correctly from the A-time=23:42:18 portion; and
the light beam
3
5
channel reading recorded data correctly from the A-time=23:42:33 portion.
By the time the CD-ROM
1
turns approximately (slightly more than) one revolution, advancing the optical pickup
2
to position IV of
FIG. 20
(where tracks (x+5)-(x+9) are illuminated by light beams
3
1
-
3
5
respectively)
the light beam
3
1
channel will have read the recorded data correctly up to A-time=23:41:62;
the light beam
3
2
channel will have read the recorded data correctly up to A-time=23:42:02;
the light beam
3
3
channel will have read the recorded data correctly up to A-time=23:42:17; and
the light beam
3
4
channel will have read the recorded data correctly up to A-time=23:42:32: and
with all gaps between the data read by light beams
3
1
-
3
5
now closed. (By this time, light beam
3
5
will have read the recorded data correctly up to A-time=23:42:47.) The data read by light beams
3
1
-
3
5
is then output from the system in the sequence in which it was recorded, and such that no duplications occur.
As the optical pickup
2
advances from position I to position II (one revolution of the CD-ROM
1
), the optical beam
3
5
channel reads recorded data from A-time 23:41:45 through 23:41:59. As the optical pickup
2
advances from position III to position IV (one revolution of the CD-ROM
1
), the optical beam
3
1
channel reads recorded data from A-time 23:41:48 through 23:41:62. In other words, there is an overlap between A-times 23:41:48 and 23:41:59, which was read by both channels. To avoid outputting these 12 frames twice, the system outputs only the copy of this data that was read by the
3
5
channel (which read it first) and discards the duplicate data read by channel
3
1
.
Moreover, when the track jump from position II of
FIG. 20
is executed, instead of a four-track jump, a three-track jump is executed. Thus the data in track (x+4), which was being read by the light beam
3
1
channel before the jump, is now illuminated by light beam
3
1
. The reason for doing this is that a four-track jump would have put the optical pickup
2
in position III of FIG.
20
. The light beam
3
1
channel would then have resumed reading recorded data from A-time 23:41:63. This would have left a gap in the data between 23:41:60 and 23:41:62, which had not yet been read by the light beam
3
5
channel prior to the track jump.
Stated in general terms, for a system with n light beams, where n is an integer of 3 or greater, each light beam channel reads data for approximately one revolution. At that point, a forward track jump of (n−2) tracks is executed, after recorded data is again read for approximately one revolutio

Affiliated with

Also associated with

Rating

Multibeam optical disk readout method and apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Multibeam optical disk readout method and apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Multibeam optical disk readout method and apparatus will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2879537