Dynamic information storage or retrieval – Information location or remote operator actuated control – Selective addressing of storage medium
Reexamination Certificate
1999-10-25
2001-12-25
Dinh, Tan (Department: 2651)
Dynamic information storage or retrieval
Information location or remote operator actuated control
Selective addressing of storage medium
C369S032010
Reexamination Certificate
active
06333901
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a disc reproducing apparatus for reproducing information recorded on a CD (Compact Disc), a DVD (Digital Video Disc or Digital Versatile Disc).
Usually, in order to ensure a conformability between a recording medium such as CD or DVD (hereinafter simply referred to as disc) and a disc reproducing apparatus, data is recorded on a disc in accordance with a predetermined data format, while recorded data is reproduced by performing an encoding treatment in accordance with the above data format.
For example, as shown in
FIG. 5
, with regard to a CD, information data is recorded along one spiral-like information track arranged in a program area between a lead-in position and a lead-out position. Further, as shown in
FIG. 6A
, other data than musical information is recorded in 98 frames forming one block unit. In fact, each frame includes synchronizing signal, indication signal, parity signal and information data.
Further, as shown in
FIG. 6A
, the indication signal includes P, Q, R, S, T, U, V and W signals each consisting of one bit, and these signals are divided into 8 sub-coding channels. In this way, as shown in
FIG. 6B
, by virtue of the Q signals included in 98 frames, it is allowed to obtain sub-code Q signals indicating address information (time information) recorded in each block, and synchronizing signals (sub-coding synchronism) S
0
, S
1
.
In order to correctly read data recorded on a disc, it is necessary to perform a tracking control of an optical pickup, and to determine whether the address information (time information) is being continuously obtained in accordance with the sub-code Q signals.
When the address information (time information) is being continuously obtained, it is determined that the optical pickup is properly tracing an information track and that data recorded on the disc is being exactly read out, thereby permitting the information reading process to be continued.
On the other hand, if the address information (time information) being continuously obtained has suddenly jumped, it is determined that the optical pickup has deviated to an adjacent information track because of an external vibration or due to some other reasons. At this moment, a block of the track where the optical pickup had arrived immediately before the pickup deviation occurred will be searched, so that the information reading process will be continued from the searched position, thereby effecting a necessary compensation treatment to ensure that the recorded data may be read out completely.
FIG. 7
is a flowchart indicating an example of a compensation treatment according to a prior art. As shown in
FIG. 7
, when an optical pickup is operated to start its scanning operation, sub-code Q signals will be reproduced from the indication signals of one block (98 frames) at a step S
100
. Then, at a step S
101
, a sub-code signal Q reproduced during the last operation is read out from a memory. At a step S
102
, address information (time information) t
1
contained in the last time sub-code signal Q is compared with address information contained in the latest sub-code signal Q so as to obtain a time difference |t
2
−t
1
|. At a step S
103
, it is determined whether the time difference |t
2
−t
2
| has continued for over a predetermined time T HD.
If |t
2
−t
1
|<T HD, it is determined that the optical pickup is tracing an information track in a correct manner, so that the obtained latest sub-code signal Q is written and stored in the above memory (step S
104
), thus allowing the normal reproducing operation to be continued at a step S
105
, thereby repeating the same process beginning from the step S
100
.
On the other hand, if it is determined at the step S
103
that |t
2
−t
1
|≧T HD, it may be determined that the optical pickup has jumped (deviated) from one information track to an adjacent track. Then, at a step
106
, in accordance with address information t
1
of the sub-code signal Q formerly read out from the memory, a block of the track at which the pickup had arrived immediately before the pickup deviation occurred will be searched, so that the information reading process will be continued from the searched position, thereby effecting a compensation treatment to ensure that the recorded data may be read out completely.
However, with the compensation treatment carried out in the above conventional disc reproducing apparatus, there is a problem that although the optical pickup has in fact not jumped (deviated) to an adjacent information track, a mistaken determination will sometimes happen indicating that such a jump (deviation) of the optical pickup has occurred.
Here, a mistaken determination associated with the prior art will be explained in the following with reference to FIG.
5
.
Referring to
FIG. 5
, a virtual line Y has been drawn extending from the center of a CD in the radial direction thereof. As may be understood in
FIG. 5
, there are fewer blocks toward the inner lead side and there are more blocks toward the outer lead side. For example, the inmost track contains blocks arranging from a first block d
1
to a No. m block dm, while an outer track contains blocks arranging from a block D
1
to a No. n block Dn, with m being smaller than n, i.e., n>m.
Conventionally, to detect an occurrence of a jump (or deviation) of an optical pickup (hereinafter may be referred to as track jump), the above predetermined time T HD is set to be shorter than a time necessary for scanning (at a predetermined linear speed) blocks d
1
-dm on the inmost track. In other words, a time necessary for scanning (at a predetermined linear speed) blocks fewer than blocks d
1
-dm on the inmost track is set to be the predetermined time T HD.
In this way, when an optical pickup jumps from the inmost track to an adjacent track, almost m blocks fail to be scanned. Thus, at the step
103
of
FIG. 7
, it is allowed to detect whether there is a jump (or deviation) of the optical pickup by comparing a time difference (between a sub-code signal Q of a block immediately before the jump and a sub-code signal Q of a block immediately after the jump) with the above predetermined time T HD.
If a track jump happens when the optical pickup is scanning a track on an outer lead side, the blocks failing to be scanned will be more than those on an inner track. Therefore, it is possible to determine whether there is a track jump at the step S
103
shown in FIG.
7
.
However, if a lot of defect blocks are continuously existing on a track on the outer lead side, and if the defect blocks are more than the blocks corresponding to the predetermined fixed time T HD, a mistaken determination indicating a track jump will happen regardless of a fact that there is no track jump at all.
For example, when there are blocks D
1
-Dn existing on the track adjacent to the outer lead side, and blocks X
1
-Xp among the blocks D
1
-Dn are defect blocks, it is impossible to correctly read sub-code signal Q from the blocks X
1
-Xp.
A time difference between a sub-code signal Q of block Xf (which is immediately before a block X
1
) and another sub-code signal Q of Xe (which is immediately after a block Xp), will become clearly larger than the above predetermined fixed time T HD. As a result, at the step S
103
(
FIG. 7
) there will be a mistaken determination indicating that a track jump has occurred, causing re-start of information reading from a block Xf, regardless of the fact that there is no track jump at all.
Further, even if the information reading is re-started from the block Xf, since the blocks X
1
-Xp are defect blocks, there will again be a mistaken determination indicating that there has occurred a track jump. In this manner, a scanning treatment for information reading will be repeated again and again from block Xf to block Xe, resulting in a problem that it will become impossible to perform a desired normal reading of information from the block Xe onward.
Further, as to why there
Abe Takuya
Furukawa Kiyoshi
Goto Hiroki
Kobayashi Hiroyuki
Kubota Hidetsugu
Arent Fox Kintner & Plotkin & Kahn, PLLC
Dinh Tan
Pioneer Corporation
LandOfFree
Disc reproducing apparatus for determining a track jump does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Disc reproducing apparatus for determining a track jump, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Disc reproducing apparatus for determining a track jump will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2580350