JP2627643B2 - Optical disc recording / reproducing method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk recording / reproducing method using a multi-beam optical head for performing parallel simultaneous recording / reproducing.

[Conventional technology]

In a so-called write-once optical disc on which information can be recorded on the user side, a guide groove for designating a recording location of information is usually formed, and information such as an address signal is formed as pre-pits. Done. There are spiral grooves and concentric grooves in the form of the guide groove. In recent years, in order to improve the information transfer rate, a method of simultaneously recording and reproducing using a large number of light beams has been proposed. And a multi-beam optical head have been developed.

Hereinafter, a recording / reproducing method using a conventional multi-beam optical head will be described. FIG. 4 is a diagram showing a configuration of the conventional multi-beam optical head. In the figure, 1 is a semiconductor laser array, 2 is a collimating lens, 3 is a deflecting beam splitter, 4 is a quarter-wave plate, 5 is a focusing lens, 6 is an optical disk, 7 is a beam splitter, 8 is a condensing lens, 9
Is a signal detector, 10 is a prism, 11 is a focus / track error detector, and FIG. 4 shows an example of a 4-beam optical head.

The light beam emitted from the semiconductor laser 1 is focused on four spots on the optical disc 6. The light beam reflected from the optical disk 6 is again focused on the signal detector 9 as four spots, and the signals of the respective channels are simultaneously detected. On the other hand, after a part of the reflected light beam enters the prism 10, only one of the four light beams is guided to the focus / track error detector 11 due to a difference in the incident angle, and focus control and track control are performed. Control is performed.

That is, in the conventional multi-beam optical head and tracking method, the distance between four light beams is
Set in advance to match the guide groove spacing above,
By performing tracking control on only one of the four guide grooves, recording / reproduction on the four guide grooves is performed.

[Problems to be solved by the invention]

Therefore, in the conventional tracking method of the multi-beam optical head, although tracking is accurately performed in one guide groove, the light beam interval is fixed, so that it is impossible to follow variations in the guide groove interval. However, grooves other than the guide groove for tracking cannot be accurately recorded or reproduced on the groove.

In the conventional tracking method of a multi-beam optical head, each light beam is condensed on one guide groove, and recording and reproduction are performed. Therefore, the same number of parallel spiral guide grooves as the number of light beams are used. Has to be formed.

The present invention has been made in view of the above points, and an object of the present invention is to record an optical disc capable of performing recording and reproduction by accurately condensing a light beam on parallel guide grooves and information pit rows. The purpose is to provide a reproduction method.

[Means for solving the problem]

For this purpose, the present invention relates to a method for recording and reproducing data on an optical disk using a multi-beam optical head having a plurality of light beams, the method comprising the steps of: By tracking the guide groove by changing the angle formed by the spiral guide groove, the two light beams are focused on the guide groove, and the remaining light beams are focused between the guide grooves. Recording and playback.

〔Example〕

(First Embodiment) Hereinafter, an embodiment of the present invention will be described. FIG. 1 is a diagram showing a configuration of an optical system of a multi-beam optical head used in the first embodiment. In the figure, 21 is a semiconductor laser array, 22 is a collimating lens, 23 is a deflecting beam splitter, 24 is a quarter-wave plate, 25 is a focusing lens, 26 is an optical disk, 27 is a beam splitter, 28 is a condensing lens, 29 Is a signal detector, 30 and 31 are prisms, 32 is a focus / tracking error detector, and 33 is a track error detector. This embodiment shows an example of a four-beam optical head.

The actuator of the multi-beam optical head used in this embodiment includes an up-down movement mechanism for focus control, and connects the light beams at both ends to perform tracking control with each of the two light beams at both ends. Includes a mechanism for varying the angle of the straight optical disc 26 with respect to the guide groove.

Next, a tracking method using a multi-beam optical head used in this embodiment will be described. FIG. 2 shows an optical disk 26.
FIG. 6 is a diagram showing a positional relationship between a guide groove 26a and a light spot A by a light beam. Four light spots A on the optical disk 26
Is 20 μm, and the interval (pitch) between guide grooves 26a is 4.8 μm
It is. Therefore, the optical head is set so that the angle between the straight line connecting the light spots A at both ends and the guide groove 26a is about 4.6 °, and is variable by tracking.

In the tracking state, by rotating the semiconductor laser array 21 mounted in the actuator, the angle between the straight line connecting the light spots A at both ends and the guide groove 26a is changed to guide the two light spots A at both ends. Groove 26
Let a track. At this time, the two guiding grooves 26a for tracking are one continuous guiding groove. The two inner light spots A are focused on a flat portion between the guide grooves 26a.

Next, results of a recording / reproducing experiment using a multi-beam optical head to which the recording / reproducing method of this embodiment is applied will be described. The optical disc used was one in which CS ₂ Te was formed as a recording film on a polycarbonate substrate having a diameter of 130 mm. The guide groove 26a was formed in a spiral shape, the pitch was 4.8 μm, and an ID signal was recorded as a pre-pit 26b by interrupting a part of the guide groove 26a.

This optical disk was mounted on a recording / reproducing apparatus including a multi-beam optical head to which the recording / reproducing method of the present invention was applied, and a tracking experiment was performed. As a result, a stable tracking operation was confirmed, and a good reproduced signal was output from the pre-pit 26b. Obtained. Next, pit recording was attempted by adding modulation signals having different frequencies to the three light beams except for the light beam at one end. As a result, by microscopic observation, it was confirmed that one predetermined recording pit row was formed on the guide groove 26a and two predetermined recording pit rows were formed between the guide grooves 26a, and 3ch simultaneous signal reproduction was performed. Also, the C / N was 50 dB or more and the crosstalk was -30 dB or less.

Second Embodiment Next, a second embodiment will be described. In the master of the optical disk used in the second embodiment, two spiral guide grooves 26a and 26a 'are formed by using a two-beam mastering device, and the distance between the two grooves is 1.6 μm and the pitch is 1.6 μm. The ID signal was recorded as a pre-pit 26b by setting the length to 6.4 μm and interrupting a part of one of the guide grooves.

The optical disk produced from such an original plate had a CS ₂ Te film formed on a polycarbonate substrate having a diameter of 130 mm, and the same multi-beam optical head as that of the first embodiment was used.

FIG. 3 is an explanatory diagram showing a positional relationship between a light spot and a guide groove by the multi-beam optical head according to the second embodiment. First, when a track experiment was performed, a good tracking operation was confirmed, and a good reproduced signal was obtained from the pre-pit 26b. Next, recording was attempted by adding modulated signals having different frequencies to the four light beams. As a result, by microscopic observation, the two guide grooves 26a, 26a '
In addition to confirming that two predetermined pit trains are formed between the guide grooves 26a and 26a 'having an interval of, the simultaneous signal reproduction of 4ch was performed, and the C / N was also obtained from any of the signals. 50dB
As described above, the crosstalk was -30 dB or less.

(Third Embodiment) An original optical disk used in a third embodiment of the present invention is formed with one spiral guide groove, and an ID signal is formed by interrupting a part of the guide groove. Was recorded as a pre-pit. The distance between the guide grooves is 4.8μ at the innermost circumference by continuously changing the relative movement speed between the substrate and the optical system.
m and 3.6 μm at the outermost circumference. A recording / reproducing experiment was performed using an optical disk prepared from the master.

The optical disk used was one in which a CS ₂ Te film was formed on a polycarbonate substrate having a diameter of 130 mm, and the multi-beam optical head was the same as in the first embodiment. The positional relationship between the light spot and the guide groove is the same as in FIG.

First, a tracking experiment was performed. As a result, a good tracking operation was confirmed in both the inner peripheral portion and the outer peripheral portion, and a good reproduced signal was obtained from the prepit. Next, modulation signals having different frequencies were applied to each of the three light beams except for the light beam at one end, and pit recording was attempted. As a result, one record hit row was formed on the guide groove and two record hit rows were formed between the guide grooves by microscopic observation, and the interval between them was 1.6 μm at the innermost circumference and 1.2 μm at the outermost circumference, and was continuous between them. Was confirmed to have changed. Simultaneous signal reproduction of 3 channels was performed, and the C / N was 50 dB or more and the crosstalk was -30 dB or less from any of the signals.

In the third embodiment, when the multi-beam optical head moves from the inner circumference to the outer circumference of the optical disk, the guide groove interval gradually narrows. Therefore, if the light spots at both ends of the multi-beam optical head are located in the respective guide grooves, the angle becomes smaller without a straight line connecting the light spot arrays of the multi-beam optical head and the guide grooves. Therefore, the interval between tracks recorded by each light spot of the multi-beam optical head becomes narrower on the outer circumference than on the inner circumference of the optical disc, and the track density can be improved.

That is, when the rotation speed is constant, the surface recording density of the conventional optical disk decreases from the inner circumference to the outer circumference, but according to this embodiment, the track density increases at the outer circumference than the inner circumference of the optical disk. However, it is possible to suppress a decrease in the surface recording density on the outer periphery and improve the surface recording density on the inner periphery.

Thus, according to the present embodiment, recording can be performed at a high areal recording density from the inner circumference to the outer circumference of the optical disc.

(Fourth Embodiment) In an original plate of an optical disk used in a fourth embodiment of the present invention, two guide grooves are formed using a two-beam masking device, and one of the guide grooves is formed. The ID signal was recorded as a pre-pit by interrupting a part of the groove.
Also, by recording while continuously changing the relative moving speed and the beam interval between the substrate and the optical system, the interval and pitch of the two grooves are 1.6 μm and 6.4 μm at the innermost circumference, respectively.
m, and 1.2 μm and 4.8 μm at the outermost periphery. A recording / reproducing experiment was performed using an optical disk prepared from the master.

The optical disk used was one in which a CS ₂ Te film was formed on a polycarbonate substrate having a diameter of 130 mm, and the multi-beam optical head was the same as in the first embodiment. The positional relationship between the light spot and the guide groove is the same as in FIG.

First, when a tracking experiment was performed, a good tracking operation was confirmed, and a good reproduced signal was obtained from the pre-pit. Next, recording was attempted by adding modulated signals having different frequencies to the four light beams. As a result, two predetermined pit rows were formed on the two guide grooves and 4.8 μm on the innermost circumference and 3.6 μm on the outermost circumference between the guide grooves by microscopic observation. , 1.
6 μm and 1.2 μm at the outermost periphery. Simultaneous signal reproduction of 4 channels was performed, and the C / N was 50 dB or more and the crosstalk was -30 dB or less from any of the signals.

In the above embodiment, an optical head having four light beams has been described. However, it is needless to say that an optical head having five or more light beams can be similarly applied.

〔The invention's effect〕

As described above, according to the optical disk recording / reproducing method of the present invention, the tracking is performed by changing the angle between the guide groove and the straight line connecting the two light beams at both ends of the multi-beam optical head. Will be higher.

According to the present invention, the number of guide grooves to be formed in advance on the optical disc is one or two for tracking.
A book is sufficient, and it is not necessary to form the same number of parallel spiral grooves as the number of light beams as in the related art.

Furthermore, just forming one or two guide grooves, 3c
Simultaneous recording and reproduction of multiple channels of h or more can be performed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram of an optical system of a multi-beam optical head used in a first embodiment of the present invention, and FIG. 2 is a diagram illustrating a guide groove and an optical head in the first embodiment. FIG. 3 is a diagram showing a positional relationship between a guide groove and a light spot in a second embodiment of the present invention, and FIG. 4 is a diagram showing a configuration of an optical system of a conventional multi-beam optical head. 21 …… Semiconductor laser array, 22 …… Collimate lens,
23 …… deflecting beam splitter, 24 1/4 wavelength plate, 25 ……
Focusing lens, 26 ... Disc, 27 ... Beam splitter, 28 ... Condensing lens, 29 ... Signal detector, 30, 31 ...
Prism, 32: Focus / tracking error detector, 33: Track error detector.

Claims (2)

(57) [Claims] 1. A method for recording / reproducing data on / from an optical disk using a multi-beam optical head having a plurality of light beams, comprising: a straight line connecting two light beams at both ends of the optical head; By tracking the guide groove by changing the angle between the guide groove and the guide groove, the two light beams are focused on the guide groove, and the remaining light beams are focused between the guide grooves for recording. A recording / reproducing method for an optical disk, which comprises performing reproduction. 2. The optical disk according to claim 1, wherein an interval between one or a plurality of parallel spiral guide grooves decreases continuously from the inner circumference to the outer circumference. 2. The method for recording / reproducing an optical disc according to claim 1.