Dynamic information storage or retrieval – Control of storage or retrieval operation by a control... – Control of information signal processing channel
Reexamination Certificate
2000-10-03
2002-04-30
Edun, Muhammad (Department: 2651)
Dynamic information storage or retrieval
Control of storage or retrieval operation by a control...
Control of information signal processing channel
C369S053100, C369S053180
Reexamination Certificate
active
06381203
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an optical disk reproducing method and apparatus which are suitable for use with an optical pickup having a first reproduction channel for reproducing recorded information from a first-type optical disk and a second reproduction channel for reproducing recorded information from a second-type optical disk and which provides for high-quality reproduction of recorded information from a third-type optical disk that is reproducible via each of the first and second reproduction channels.
Generally, in DVD (Digital Versatile Disk) players, the optical pickup is equipped with a DVD reproduction channel and CD (Compact Disk) reproduction channel so that DVDs are reproduced via the DVD reproduction channel and CDs are reproduced via the CD reproduction channel.
As optical disks for communication karaoke with background pictures recorded thereon or optical disks for game software, there have been used high-density CDs that are characterized by a higher recording density than that of normal CDs so as to provide a total program-recording time length of 100 min. or over. Information recorded on such high-density CDs can be played back or reproduced by a DVD reproduction channel as well as a CD reproduction channel. Discussion is made below as to which of the DVD and CD reproduction channels can be used more advantageously for reproduction of the high-density CDs. The CD reproduction channel is designed as follows to match physical characteristics of the CD (i.e., normal CD) such as a substrate thickness of 1.2 mm, track pitch of 1.6 &mgr;m and linear velocity of 1.2 -1.4 m/sec.
Laser Wavelength (nm)
NA of Objective Lens
Example 1
780
0.45
Example 2
635 or 650
0.37
The DVD reproduction channel, on the other hand, is designed as follows to match physical characteristics of the DVD such as a substrate thickness of 0.6 mm, track pitch of 0.74 &mgr;m and linear velocity of 3.49 m/sec. in the case of the single-layered DVD.
Laser Wavelength (nm)
NA of Objective Lens
635 or 650
0.6
The high-density CD has physical characteristics somewhat different from those of the normal CD; for example, the high-density CD has a substrate thickness of 1.2 mm, track pitch of 1.3 &mgr;m and linear velocity of 0.9 m/sec. If such a high-density CD is reproduced by the CD reproduction channel, high-frequency components (particularly, 3T signals) of reproduced RF signals would be decreased in amplitude, thus deteriorating jitter characteristics. Because such reproduced RF signals can not be put to practical use as they are, it is necessary to amplify each 3T signal by equalizing the signal waveform by use of a transversal filter or the like, in which case, however, noise components would also be amplified to no small degree. But, the CD reproduction channel is advantageous in that it can be more tolerant of (or less susceptible to) a disk's warp by virtue of its small NA (Numerical Aperture) and is also less susceptible to defects on the disk surface by virtue of its large beam spot diameter. If, on the other hand, the high-density CD is reproduced by the DVD reproduction channel, then there would occur no decrease in the amplitude of the 3T signals; however, the DVD reproduction channel presents the disadvantage that it is susceptible to a disk's warp due to its large NA and is also susceptible to defects on the disk surface due to its small beam spot diameter.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an optical disk reproducing method and apparatus which are suitable for use in reproduction of recorded information via an optical pickup that includes first and second reproduction channels for reproducing recorded information from first-type and second-type optical disks and is also capable of reproducing recorded information from a third-type optical disk via each of the first and second reproduction channels, just like the one including DVD and CD reproduction channels and capable of reproducing a high-density CD, and which provides for high-quality reproduction of the recorded information from the third-type optical disk.
Warp, surface defects etc. of an optical disk would appear as undesired jitters in RF signals reproduced from the optical disk. Thus, the present invention is characterized by, when reproducing recorded information from a third-type optical disk (other than first-type and second-type optical disks), first test-reproducing the third-type optical disk both via a first reproduction channel and via a second reproduction channel to thereby respectively detect jitter values of the information reproduced via the first and second reproduction channels and then reproducing the recorded information from the third-type optical disk using one of the first and second reproduction channels which attains the jitter value closer to a predetermined target jitter value.
More specifically, the present invention provides an improved optical disk reproducing method which comprises: a step of providing an optical pickup including a first reproduction channel for reproducing recorded information from a first-type optical disk and a second reproduction channel for reproducing recorded information from a second-type optical disk; and a step of, when recorded information is to be reproduced from a third-type optical disk that is different from the first-type optical disk and the second-type optical disk but reproducible via each of the first and second reproduction channels, test-reproducing the recorded information from the third-type optical disk both via the first reproduction channel and via the second reproduction channel to thereby detect a jitter value of the information reproduced via the first reproduction channel and a jitter value of the information reproduced via the second reproduction channel, and then reproducing the recorded information from the third-type optical disk using one of the first and second reproduction channels that attains the jitter value closer to a predetermined target jitter value. Because the above arrangement allows the third-type optical disk to be reproduced via the reproduction channel capable of attaining better jitter characteristics (i.e., jitter value closer to the target jitter value), the present invention always provides for high-quality reproduction of the third-type optical disk irrespective of the condition of the disk.
For example, the first-type optical disk is a DVD and the second-type optical disk is a normal CD, and the first reproduction channel is a DVD reproduction channel and the. second reproduction channel is a CD reproduction channel . Where the third-type optical disk is a high-density CD of the CD recording format which has a higher recording density than that of the normal CD so as to provide a total program-recording time length of 100 min. or over, the third-type optical disk is reproduced via the first or DVD reproduction channel if the better jitter characteristics are attained by the DVD reproduction channel. Similarly, if the better jitter characteristics are attained by the second or CD reproduction channel, then the third-type optical disk is reproduced via the CD reproduction channel. With this arrangement, the present invention always provides for high-quality reproduction of the third-type optical disk irrespective of the condition of the disk.
The present invention also provides an improved optical disk reproducing apparatus which comprises: an optical pickup including a first reproduction channel for reproducing recorded information from a first-type optical disk and a second reproduction channel for reproducing recorded information from a second-type optical disk; a jitter detection section that detects a jitter value of a reproduced RF signal outputted by the first reproduction channel and a jitter value of a reproduced RF signal outputted by the second reproduction channel; and a control section that switches between the first reproduction channel and the second reproduction channel, depending on a type of the optical disk to b
Edun Muhammad
Morrison & Foerster
Yamaha Corporation
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