JP3042136B2 - Reproduction method of optical recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reproducing an optical recording medium, and more particularly to a method for reproducing an optical recording medium on which multi-value digital data is recorded.

[0002]

2. Description of the Related Art A conventional optical disk is binary recording in which binary data is associated with the presence or absence of a pit. However, in such binary recording, there is a limit in improving the recording density. Therefore, as shown in, for example, Japanese Patent Application Laid-Open No. 58-215735, there has been proposed an optical disk in which the depth of a pit is set at a plurality of levels to record multi-value data.

That is, as shown in FIG. 8A, portions A1, B1, C1, D1, and E1 having different depths are provided on a disk, and portions A1, B1, C1, and D1 having different depths are provided.
1, E1 correspond to quinary data. The depth of the portion A1 is, for example, 0, and the depth of the portion B1 is, for example, λ / 1.
6 (λ is the wavelength of the beam), the depth of the portion C1 is, for example, 3λ / 16, and the depth of the portion D1 is, for example, λ /
8, and the depth of the portion E1 is, for example, λ / 4.

[0004] As shown in FIG. 8B, the reproduced RF signal level of this disk is such that the portions A1, B1, and C having different depths are provided.
It changes according to 1, D1, and E1. That is, as shown in FIG. 8B, the reproduced RF signal level of the portion A1 becomes “0”, the reproduced RF signal level of the portion B1 becomes “1”, and the reproduced RF signal level of the portion C1 becomes “3”. ,
The reproduction RF signal level of the portion D1 becomes “2”, and E1
Is "4".

[0005] Therefore, multilevel data can be reproduced by detecting the level of the reproduced RF signal. That is, the reproduction RF
If the signal level is "0", it is data of a value recorded corresponding to the portion of A1, and if the reproduced RF signal level is "1", the data is B
1 is the data of the value recorded corresponding to the portion 1
If the F signal level is "3", it is data of a value recorded corresponding to C1, and if the reproduced RF signal level is "2", it is data of a value recorded corresponding to D1, and the reproduced RF signal level is "4". "Is data of a value recorded corresponding to E1.

[0006]

However, when multi-level recording is performed by setting the pit depth in a plurality of steps as described above,
As the number of multi-values increases, the level difference of the reproduced RF signal level for each value decreases. For this reason, if the reproduction is performed using only the reproduction RF signal level by increasing the multi-valued number of the recording data,
Due to the influence of noise, there is a problem that many errors occur in reproduced data.

Accordingly, an object of the present invention is to provide a method of reproducing an optical recording medium which can improve the recording density, is less affected by noise even if the number of multi-values is increased, and can reproduce multi-value data correctly. Is to do.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a method of reproducing an optical recording medium on which data of three or more values having different pit depths are recorded, wherein the level of the RF signal from the optical recording medium and the level of the push-pull signal are determined. This is a reproducing method of an optical recording medium, which detects and reproduces recorded data of an optical recording medium from an RF signal level and a push-pull signal level.

[0009]

Since the reproduction data of the optical disk on which the multi-value data is recorded is reproduced using the reproduction RF signal level and the reproduction push-pull signal level, even if the multi-value number of the data is increased, the reproduction data is surely obtained. Can play data.

[0010]

An embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 2, the optical disc in the optical disc reproducing apparatus to which the present invention is applied includes portions A2, B2, C2, D2, E2, F2, G having different depths.
Eight-value data is recorded corresponding to 2, H2. A1
Is, for example, 0, the depth of B2 is, for example, λ / 8, the depth of C2 is, for example, λ / 4, the depth of D2 is, for example, 3λ / 8, and the depth of the portion of E2. For example, 5λ
/ 16, and the depth of the portion of E2 is 3λ / 16,
The depth of the portion of F2 is 3λ / 16, the depth of the portion of G2 is λ / 16, and the depth of the portion of H2 is 7λ / 16.

The multi-value recorded data is reproduced using the RF signal and the push-pull signal. Conventional multi-level recording optical discs perform reproduction using only the reproduction RF signal level. However, in one embodiment of the present invention, multi-value recording is performed using the reproduction RF signal and the reproduction push-pull signal. Playing data. For this reason,
Even if the number of multivalues is increased, data can be reproduced without error.

FIG. 3 shows the pit depth and the reproduction RF.
It shows the relationship between the signal levels and the relationship between the pit depth and the reproduced push-pull signal level. As shown by RF in FIG. 3A, the reproduced RF signal level becomes substantially 0 when the pit depth is 0 and λ / 2, and the pit depth is λ / 4.
It becomes the maximum at the time. Then, the polarity of the reproduction RF signal level is constant.

On the other hand, when the pit depth is λ / 4 or less, the polarity of the reproduced push-pull signal becomes positive,
The pit depth becomes a positive maximum at λ / 8. The polarity becomes negative when the pit depth is from λ / 4 to λ / 2, and becomes minimum when the pit depth is 3λ / 8.

For example, when the pit depth is λ / 8,
At the time of λ / 8, the reproduced RF signal level is the same.
Therefore, a signal having a pit depth of λ / 8 and a signal having a depth of 3λ / 8 cannot be distinguished only by the reproduction RF signal level. However, when the pit depth is λ / 8, the reproduced push-pull signal level is positive and the pit depth is 3
At the time of λ / 8, the reproduction push-pull signal level becomes negative. Therefore, if the sign of the reproduction push-pull signal level is detected together with the reproduction RF signal level, whether the pit depth is λ / 8 or not is determined. It can be determined whether the signal is a signal when the depth is 3λ / 8.

As shown in FIG. 2A, portions A having different depths
2, B2, C2, D2, E2, F2, G2, and H2, the reproduction RF signal levels are "0", "2", "4", and "4", respectively, as shown in FIG. 2B. 2 ",
The levels are "3", "3", "1", and "1". Also, the parts A2, B2, C2, D2, E2, F2, G2,
As shown in FIG. 2C, the reproduction push-pull signal level of H2 is “0”, “+2”, “0”, “−2”, “−”.
1 "," +1 "," +1 "," +1 ", and" -1 ".

In this case, by detecting the level of the reproduced RF signal and detecting whether the level of the reproduced push-pull signal is "0", negative, or positive, the depth of the pit to be reproduced is determined. It can be determined whether it is a signal.

That is, if the reproduction RF signal level is "0" and the reproduction push-pull signal level is "0", it can be determined that the portion A2 having a depth of 0 is being reproduced.

If the reproduction RF signal level is "1", the depth λ
A portion G2 of / 16 or a portion H2 having a depth of 7λ / 16 is reproduced. At this time, if the reproduction push-pull signal level is positive, it can be determined that the portion G2 of λ / 16 is reproduced. 7λ / 1 if the pull signal level is negative
It can be determined that the portion H2 of No. 6 is being reproduced.

If the reproduced RF signal level is "2", a portion B2 having a depth of λ / 8 is being reproduced, or a portion having a depth of 3λ
It can be determined that the / 8 portion F2 is being reproduced. At this time, if the reproduction push-pull signal level is positive, the depth is λ /
It can be determined that the portion 8 is B2 reproduced, and if the level of the push-pull signal is negative, it can be determined that the portion D2 having a depth of 3λ / 8 is reproduced.

If the reproduction RF signal level is "3", it can be determined that the portion E2 having a depth of 5λ / 16 is being reproduced or the portion F2 having a depth of 3λ / 16 is being reproduced.
At this time, if the reproduction push-pull signal level is negative, 5λ
If the reproduction push-pull signal level is positive, it can be determined that the 3λ / 16 part F2 is being reproduced.

If the reproduction RF signal level is "4" and the reproduction push-pull signal level is "0", it can be determined that the portion C2 having a depth of λ / 4 is being reproduced.

FIG. 1 shows an embodiment of the present invention. In one embodiment of the present invention, multi-value data is reproduced using a reproduced RF signal level and a reproduced push-pull signal level. By the way, in a normal optical disc reproducing apparatus, since the push-pull signal level is minimum in the just track, it is difficult to reproduce the multi-valued data using the reproduced RF signal level and the reproduced push-pull signal level. Therefore, in one embodiment of the present invention, the disk is irradiated with two read spots, a spot for obtaining an RF signal and a spot for obtaining a push-pull signal, and the spot for obtaining a push-pull signal is shifted from the track center. In this way, an RF signal and a push-pull signal are obtained.

In FIG. 1, a laser beam from a laser diode 1 for detecting an RF signal level is applied to an optical disk 6 via a beam splitter 2, a quarter-wave plate 3, a beam splitter 4, and a lens 5. The laser beam from the laser diode 1 is located at the track center as shown by a spot SP1 in FIG.

This laser beam is reflected by the optical disk 6, and the reflected light is transmitted through the lens 5, the beam splitters 4, 1
The light is reflected by the beam splitter 2 via the 波長 wavelength plate 3 and received by the photodiode 7. The output of the photodiode 7 is supplied to the level detection circuit 8. The reproduction RF signal level is detected by the level detection circuit 8. The output of the level detection circuit 8 is supplied to the reproduction data judgment circuit 9.

The laser beam from the laser diode 11 for detecting the push-pull signal is supplied to the beam splitter 1.
2, is reflected by the beam splitter 4,
Irradiates the optical disk 6 via the. The laser beam from the laser diode 11 is located at a position deviated from the track center as shown by a spot SP2 in FIG.

The laser beam is reflected by the optical disk 6, and the reflected light is reflected by the beam splitter 4 via the lens 5, further reflected by the beam splitter 12, and received by the photodetector 13. The output of the photo detector 13 is supplied to the level detection circuit 14.
The level detection circuit 14 detects the level of the reproduced push-pull signal. The output of the level detection circuit 14 is supplied to the reproduction data judgment circuit 9.

The reproduction data judgment circuit 9 judges the reproduction data from the detection output of the reproduction RF signal level from the level detection circuit 8 and the detection output of the reproduction push-pull signal level from the level detection circuit 14. The reproduced data is output from the output terminal 15.

In the above-mentioned embodiment, two spots are irradiated on the optical disk. However, as shown in FIG.
The push-pull signal may be detected with a delay of about 0.1 μm on the disk surface.

As shown in FIG. 6, one spot may always be located at a position deviated from the track center. Then, a reproduced RF signal and a reproduced push-pull signal are always obtained. However, this method has a problem that the tracking control is not stable.

Further, as shown in FIG. 7, the track on which the multilevel data is recorded may be wobbled.

[0031]

According to the present invention, the reproduced data of the optical disk on which the multi-valued data is recorded is reproduced by using the reproduced RF signal level and the reproduced push-pull signal level. Even if the number is increased, data can be reliably reproduced.

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of the present invention.

FIG. 2 is a schematic diagram used for describing one embodiment of the present invention.

FIG. 3 is a graph used for explaining one embodiment of the present invention.

FIG. 4 is a schematic diagram used for describing one embodiment of the present invention.

FIG. 5 is a schematic diagram used for describing another embodiment of the present invention.

FIG. 6 is a schematic diagram used for explaining still another embodiment of the present invention.

FIG. 7 is a schematic diagram used for explaining still another embodiment of the present invention.

FIG. 8 is a schematic diagram used for explaining a conventional multi-value recording optical disk.

[Explanation of symbols]

 1, 11 Laser diode 6 Optical disk 8, 14 Level detection circuit 9 Reproduction data judgment circuit

Claims (1)

(57) [Claims] 1. A reproducing method for an optical recording medium on which data of three or more values having different pit depths are recorded, wherein an RF signal level and a push-pull signal level from the optical recording medium are detected, and the RF signal level is detected. And reproducing the recording data of the optical recording medium from the data of the push-pull signal and the push-pull signal level.