JPH1125461A - Optical disk and its recording and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately record and reproduce high densified information data by disposing a land area and a groove area alternately both in the radial direction and in the track direction and disposing a data area composed of the land areas and the groove areas in each round of the track and a servo area alternately. SOLUTION: The land area and the groove area are alternately disposed in both the radial direction and the track direction on the track(s) formed in a spiral or concentric circular pattern on an optical disk to be recordable of information. The data area D composed of the land areas and the groove areas in each round of the track 1 and the servo area S are disposed alternately by 200-4000 without limiting to a ratio in length. Information of track addresses, etc., can be recorded by wobbling walls of the groove L in the radial direction of the disk. By this method, a beam spot is moved to follow the track center accurately without generating any track offset so as to obtain an exact clock signal, and hence high density recording and reproducing is feasible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk and a recording / reproducing apparatus for the optical disk.

[0002]

2. Description of the Related Art At present, as a method of recording information in an optical disk apparatus, a guide track is formed on a disk as approximately 1 /.
A concave linear groove (referred to as a groove track) having a depth of 8 wavelengths is usually formed spirally at a track pitch of 1.6 μm, and data to be recorded is recorded on the concave groove or on the convex groove. Was recorded on one of the tracks. In recording, information is recorded on a track while condensing a laser beam on a small spot, optically detecting the center of the track, and causing the light spot to follow the track by an actuator. As a recording material, a write-once medium such as As-Te-Se, a magnetic recording medium such as Tb-Fe-Co, and a phase change recording medium such as Ge-Sb-Te are used. To reproduce the signal on the track recorded in this way,
The laser beam is focused on a small spot with a low output, and the data is reproduced while optically tracking the track.

[0003] More recently, in order to increase the recording capacity of an optical disk, a convex land portion L as shown in FIG.
A so-called land / groove recording method which doubles the track density by recording on both tracks of the concave groove portions G6 and G7 and L7 is under study. Regarding this land / groove recording, for example, reference Miya
gawa, Y .; Gotoh, K .; Nishiuchi,
E. FIG. Ohno and N.M. Akahira: "Lan
d and groove recording fo
r high track density on p
phase change optical disk
s ", Jpn. J. Appl. Phys. 32, 5
324/5328 (1993). The push-pull method is used for data recording optical disks to track tracks optically, but at higher densities, higher accuracy is required for tracking. An offset occurs, causing a problem that the light spot deviates from the center of the track when recording or reproducing data.

The prior art will be described below with reference to FIGS. 6, 7 and 8. In FIG. 6, a land L1 formed on an optical disc is irradiated with a beam spot, and a part of the beam spot is irradiated on adjacent grooves G1 and G2.
2 reflects the laser light. The zero-order diffracted light LS10 is obtained from the land L1, and the first-order diffracted lights LS12 and LS21 are obtained from the grooves G1 and G2. The zero-order diffracted light LS10 and the first-order diffracted lights LS21 and LS12 described above are guided to a photodetector 8 provided in an optical pickup (not shown), and are irradiated on the photodetector 8 as shown in FIG.

[0007] As shown in FIG. 7, in the photodetector 8 divided into two parts, a range AR10 irradiated with the 0th-order diffracted light LS10 is indicated by a solid line as a circular portion, and is hatched. The ranges AR21 and AR12 are ranges irradiated with the zero-order diffracted light LS10 and the first-order diffracted lights LS21 and LS12. In the photodetector 8, the first-order diffracted light LS2
1. The LS 12 is photoelectrically converted to an electric signal. Therefore, the level difference of the light intensity is converted into the level difference of the electric signal. Then, the level difference of the electric signal [ELA-EL
B] is used as a push-pull tracking error signal, but if the disk 5 is inclined in the radial direction,
Since the diffracted light distribution in the detector 8 in FIG. 7 moves,
The first-order diffracted lights LS21 and LS12 are photoelectrically converted, and an offset occurs in the level difference [ELA-ELB] signal of the electric signal, so that an accurate push-pull tracking error signal cannot be obtained.

As a method for canceling the offset of the push-pull tracking signal, a "differential push-pull method" has been proposed in 1986 on page 127 of the proceedings of the Optical Memory Symposium '86 Society. In this method, as shown in FIG. 8, three spots are formed on a disk by an optical head using a diffraction grating component, and reflected lights of the three spots from the disk are received by two-divided detectors. Then, an accurate push-pull tracking signal is formed by arithmetic processing. However, this method has many problems in data recording such as a decrease in light efficiency because a diffraction grating for forming three spots in the optical system must be provided in the light beam. Further, there is a problem that the position adjustment of the three light receiving detectors is complicated.

[0007]

The problem to be solved by the present invention is described with reference to FIG. 5 in which information is recorded in a form in which data can be optically read in both grooves and lands.
This will be described with reference to FIGS.

FIG. 5 shows an enlarged schematic sectional view and an enlarged schematic plan view of a part of a land / groove recording disk for recording on the lands L6, L7 and the grooves G6, G7 in order to increase the recording capacity of the optical disk. . In the illustrated example, the width of the groove portion and the width of the land portion are 0.6 microns. In order to optically track and track the land portion L6 or the groove portion G7, the push-pull method shown in FIGS. 6 and 7 is generally used. However, when the land width and the groove width are reduced to approximately 0.6 μm. However, higher accuracy is required for tracking, and the above-described push-pull tracking method uses an optical disc tilted or
If the optical disc is eccentric, the level difference [ELA-EL
B] occurs, resulting in a DC offset, which erroneously determines that a track shift has occurred. As a result, a problem occurs in recording and reproducing data on lands and grooves having a narrow track width, which is a major obstacle to practical use.

Further, in FIG. 5, the side surface of the groove is wobbled to obtain a clock signal at the time of data recording. Although the wobbling width is small (for example, 30 nanometers), it is susceptible to interference with the data signal recorded thereon, which is a major cause of signal reading error, and the track and land are narrowed (for example, 0.6 nm). Micron size or less), which is a major obstacle to practical application. Further, a groove of one wobble has many problems such as the necessity of a two-beam laser cutting device when forming a disk.

[0010]

The object of the present invention is to provide an optical disk according to the first invention of the present invention, which has a recording film for recording information in an optically readable form, and stores information formed in a spiral or concentric shape. The land area and the groove area are alternately arranged on the recordable track both in the radial direction and the track direction, and the data area and the servo area each composed of the land area and the groove area are increased from 200 per circumference of the track. The problem is solved by arranging 4000 alternations.

In the recording / reproducing apparatus according to the second aspect of the present invention, a means for irradiating the rotating optical disk of the first aspect with a light beam, and the light beam causes push-pull tracking in a land portion and a groove portion in a track direction. Means for detecting a signal, means for detecting an accurate differential push-pull tracking signal from a difference signal of the push-pull signal, and a tangential push-pull signal at a boundary between a land area and a groove area of a track by a light beam. And means for detecting a clock signal.

In the recording / reproducing apparatus according to the third invention of the present invention, means for irradiating the rotating optical disk of the first invention with a light beam, and the light beam causes push-pull tracking at a land portion and a groove portion in a track direction. It has means for detecting a signal and means for detecting the tilt of the disc from the sum signal of the push-pull signals.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 illustrates an optical disk recording / reproducing apparatus according to the present invention. In FIG. 1A,
A phase change film or a magneto-optical thin film is formed on the disk substrate 5. Laser light output from the laser diode 4 used in the optical pickup 3 is collimated by the collimator lens 20. The parallel light reaches an objective lens 22 via a beam splitter 21. The above-mentioned parallel light is condensed by the objective lens 22, and the surface 5a of the optical disc 5
To form a beam spot BS0. The laser light reflected from the surface 5a of the optical disk 5
2. The light is guided to the photodetector 7 via the beam splitter 21 and irradiated on the photodetector 7. The photodetector 7 is a quadrant photodetector composed of photodetectors 7a, 7b, 7c and 7d. The light applied to the photodetector 7 is
a, 7b, 7c, and 7d, the outputs of which are output from the differential amplifiers 23, 24 as shown in FIGS.
Supplied to

Next, the structure of the optical disk according to the present invention used in the present invention will be described. In FIG. 2, a land area and a groove area are alternately arranged in both the radial direction and the track direction. It is arranged from 4000 alternation. The ratio of the lengths of the alternating data area D and the servo area S in the data direction is not limited, and may be 50:50 or 7
The ratio may be 5:25, 100: 1. In FIG. 2, even if the disk radial wall of the groove L is straight or one of the grooves radial wall is wobbled,
Alternatively, both the radial walls of the groove may be wobbled. By wobbling the wall of the groove in this manner, information such as a track address can be recorded on the groove wall.

Next, a method of forming a differential push-pull tracking signal using a one-spot optical system according to the present invention will be described with reference to FIGS. FIG. 1A shows a one-spot optical system which forms one spot BS0 on a disk. The reflected light of the spot BS0 is reflected by the photodetector 7 in FIG.
The output from the photodetectors 7a and 7c is supplied to the (−) side terminal of the differential amplifier 24, and the output from the photodetectors 7b and 7d is supplied to the (+) ) Side terminal. When the light spot BS0 sequentially scans the area D, the area S, and the areas D,... On the track center Lch, the polarity of the push-pull signal is inverted between the land L and the groove G in the areas D and S. As a result, the push-pull output Lo in the area D and the push-pull output Go in the area S are held by the sample-and-hold circuit 25, and the difference signal 1, (Lo−Go), is a differential push-pull tracking signal not including an offset. 1 can be formed. The differential push-pull tracking signal 1 is a tracking signal that is not affected by a shift in light distribution that occurs when the disk 5 is tilted or the optical pickup 3 is shifted in the disk radial direction. This tracking signal 1 is supplied to the tracking servo circuit 27.

1 (A) and 1 (C), when the sum signal 2 of the push-pull signals Lo and Go detected in the areas D and S is formed, and (Lo + Go), this signal is generated when the disk 5 is tilted or tilted. This largely indicates the offset amount due to the lens shift. This sum signal 2,
By separating the offset component due to the eccentricity of the disk 5 from (Lo + Go), it is possible to detect only the signal of the disk tilt. The tilt of the disk 5 can be controlled using the signal. Alternatively, after driving the disk, the head is scanned in the radial direction of the disk to obtain the sum signal 2 of the push-pull signals Lo and Go,
It is also possible to detect feed-forward control by detecting only the tilt of the disc from (Lo + Go).

Next, the formation of a clock signal according to the present invention will be described with reference to FIG. 1 and 2, the linear optical pickup 3 moves along a track center Lch indicated by a straight line. Therefore, the edge t1 of the boundary between the land portion L and the groove portion G of the region D and the region S,
The light distribution at which the reflected light of the beam spot BS0 at t2 irradiates the photodetector 7 is such that at the edge t1, the photodetector 7
a, 7b, 7c, 7d are biased toward 7a, 7b, edge t2
Then, it is biased to 7c and 7d. However, when the beam spot BS0 is between t1 and t2 and is located at the track center Lch, the light distribution irradiated on the photodetector 7 is uniform. That is, the outputs from the photodetectors 7a and 7b are supplied to the (−) side terminal of the differential amplifier 23, and the photodetectors 7c and 7d are supplied.
Is supplied to the (+) side terminal of the differential amplifier 23, when the beam spot BSO is located at the edge t1, the output of the differential amplifier 23 (this signal is called a tangential push-pull signal) A positive output signal appears,
When located at the edge t2, a negative output signal appears.

For example, by narrowing the area S, the edges t1 and t2
When the distance between them is close to the diameter of the light spot,
An S-shaped output waveform as shown in FIG. Therefore, a clock signal can be formed by detecting the zero point of the tangential push-pull signal output of the differential amplifier 23. This clock signal is multiplied by the clock forming circuit 26 and used to generate a data channel clock. Region S, that is, edge t1
The distance between t2 and t2 is preferably slightly larger than H / NA, where H is the size of the light spot, that is, the wavelength of the laser diode 4 is NA, and the numerical aperture of the lens 22 is NA. H = 0.6
Assuming that 5 microns and NA = 0.60, t1-t2 = 1.
08 microns.

However, in order to stably detect the differential push-pull tracking signal in the region S, it is preferable that the length is 1.2 times longer, that is, about 1.3 microns. In order to further enhance the stability of the differential push-pull tracking signal in the region S, the interval between t1 and t2 in the region S is made larger than the difference amplifier when the beam spot BSO passes through the edges t1 and t2. Edge t in 23 isolated output signal waveforms
It is also possible to form a clock by detecting 1 or edge t2.

Next, the disk structure of the present invention will be described with reference to FIG. In FIG. 3, the data area D and the servo area S
Are alternately arranged in both the radial direction and the track direction, and are alternately arranged between 200 and 4000 in one round of the track. In the data area D, land areas L and groove areas G having substantially the same width are alternately arranged in the radial direction. The data area D is an area where data is recorded. The ratio of the length of the data area D to the length of the servo area S is not limited, and is, for example, 100: 1 or 30.
0: 1.

The servo area S has a clock detection mark CLK.
And a push-pull tracking detection mark Tr, each of which is a simple one having a substantially rectangular shape and a length of the push-pull tracking detection mark T.
r is longer than the clock detection mark CLK.
When the data area D is the land L, the clock detection mark CLK and the push-pull detection mark are grooves G. On the other hand, when the data area D is the groove G, the clock detection mark CLK and the push-pull tracking detection mark Tr are lands L.

Next, the formation of a differential push-pull tracking signal and a tracking signal from the disk shown in FIG. 3 according to the present invention will be described with reference to FIGS. 3 and 4C.
This will be described with reference to FIG. In FIG. 4C, the output from the photodetectors 7a and 7c is supplied to the (−) side terminal of the differential amplifier 24 with the signal photoelectrically converted by the photodetector 7, and the photodetectors 7b and 7d. Is supplied to the (+) side terminal of the differential amplifier 24.

The push-pull tracking signal Lo at the land portion L of the data recording area D and the push-pull tracking signal Go at the tracking detection mark at the groove portion of the servo area S in FIG.
, And the difference signal 1, (Lo−Go), is formed as a differential push-pull tracking signal 1. The differential push-pull tracking signal 1 is a tracking signal that is not affected by the shift of the light distribution that occurs when the disk 5 is tilted or the optical pickup 3 is shifted in the disk radial direction. This tracking signal 1 is supplied to the tracking servo circuit 27.

On the other hand, the sum signal 2, (Lo + Go) indicates that the disc 5 largely indicates an offset amount due to tilt or lens shift. This sum signal 2, (Lo
By separating the offset component due to the eccentricity of the disk 5 from + Go), it is possible to detect only the signal of the disk tilt. The tilt of the disk 5 can be controlled using the signal.

The formation of a clock using the disk shown in FIG. 3 according to the present invention will be described with reference to FIGS. 3 and 4B. The clock signal is generated using the clock detection mark CLK in the servo area S shown in FIG. That is, an S-shaped curve is drawn by a tangential push-pull signal when the light spot crosses both ends of the clock pit. The zero point of the S-shaped curve can be detected and supplied to the clock forming circuit 26 to form a clock signal. The clock signal formed by the clock forming circuit 26 is multiplied and used to generate a data channel clock. It is preferable that the clock detection mark CLK length is as short as possible and the push-pull tracking detection mark Tr is longer. Further, in FIG. 3, a plurality of clock detection marks in the region S may be provided, modulated with information, and used as address marks.

[0027]

According to the present invention, the beam spot accurately follows the track center without generating a track offset in the land and groove areas, and a more accurate clock signal can be obtained, so that high-density information data of the optical disk can be accurately recorded. Can be played.

[Brief description of the drawings]

FIG. 1 is a block diagram of a recording and reproducing apparatus for recording and reproducing information on lands and grooves of an optical disc according to the present invention.

FIG. 2 is an enlarged schematic view showing a part of the structure of a land and groove disk of the optical disk of the present invention.

FIG. 3 is an enlarged schematic view showing a part of the structure of a land and groove disk of the optical disk of the present invention.

FIG. 4 is a block circuit diagram of a recording / reproducing apparatus for recording / reproducing information on lands and grooves of an optical disc according to the present invention.

FIG. 5 is a schematic enlarged sectional view and a schematic enlarged plan view of a part of a known land / groove recording disk.

FIG. 6 is a schematic diagram illustrating the relationship between a known land / groove recording disk and its reflected diffracted light.

FIG. 7 is a schematic diagram showing a range of irradiation of a known two-divided photodetector with diffracted light of a light beam spot.

FIG. 8 is a schematic diagram showing a known three-spot differential push-pull method.

[Explanation of symbols]

L land part, G groove part, LS disk diffracted light, BS0 light beam spot, Lch track center line, push-pull tracking signal in Lo land part, push-pull tracking signal in Go groove part, 1 differential push-pull tracking signal (Lo-Go), 2 offset signal (Lo + Go), 3 optical pickup, 4 laser diode, 5 disk, 7, 8 photodetector,
20, 22 lens, 21 beam splitter, 2
3, 24 differential amplifier, 25 sample and hold circuit, 26 clock forming circuit, 27 tracking servo circuit, 28 disc tilt servo circuit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Fig11B 27/00 D

Claims (5)

[Claims] 1. A recording medium for recording information in a form which can be read optically, and a land area and a groove area are radially formed on a spiral or concentric track on which information can be recorded. An optical disc characterized by being alternately arranged in the direction, and having a data area composed of a land area and a groove area and a servo area alternately arranged from 200 to 4000 per one track of the track. 2. An optical disk characterized in that both or one of the radial walls of the groove in the disk radial direction is wobbled discontinuously. 3. An optical disk, wherein a mark for detecting a clock signal and a tracking signal is formed in a servo information area. 4. A recording film for recording information in a form which can be read optically, and a land area and a groove area are radially formed on a spiral or concentric track on which information can be recorded. A light beam is applied to a rotating optical disk in which a data area and a servo area composed of a land area and a groove area are alternately arranged in the direction of 200 to 4,000 per track circumference. Means for irradiating, the light beam, means for detecting a push-pull tracking signal in a land portion and a groove portion in the track direction, and means for detecting an accurate differential push-pull tracking signal from a difference signal between the push-pull signals, Due to the light beam, the boundary between the land area and the groove area of the track is formed. Means for detecting a clock signal from a tangential push-pull signal generated by the recording / reproducing apparatus. 5. A recording film for recording information in a form which can be read optically, and a land area and a groove area are also formed in a spiral or concentric manner on a track on which information can be recorded. A light beam is applied to a rotating optical disk in which a data area and a servo area composed of a land area and a groove area are alternately arranged in the direction of 200 to 4,000 per track circumference. Irradiating means, means for detecting a push-pull tracking signal in a land portion and a groove portion in a track direction by the light beam, and means for detecting a tilt of a disc from a sum signal of the push-pull signals. Recording and reproducing device.