JP2002334437A - Optical recording medium and optical recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To execute multilevel recording of 5 stages or more on a recording layer by changing time to irradiate a disk optical recording medium rotated at a fixed angular velocity in a laser beam irradiation position. SOLUTION: In the recording layer 12 of a disk optical recording medium 10, a plurality of virtual recording cells 40 are continuously assumed spirally or concentric-circularly in a group 16, for each virtual recording cell 40, corresponding to information to be recorded, the irradiation time of a laser beam is modulated by 5 stagers or more to form recording marks 48A to 48Q of different sizes, and an optical reflectivity at the virtual recording cells 40 is modulated in multiple stages to change the reflection level of a reading laser beam by 5 stages or more during reproducing. The lengths of the virtual recording cells 40 in a disk rotational direction are set so as to be circular arc lengths of circular curves equal to a disk center.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-level recording of data by irradiating an optical recording medium by switching at least one of an irradiation time and an irradiation power of a laser beam in multiple stages in accordance with data to be recorded. The present invention relates to an optical recording medium and an optical recording method.

[0002]

2. Description of the Related Art In contrast to a conventional optical recording medium, in which data is recorded by changing the length of a reproduction signal (the length of a reflection signal modulation section) in multiple steps, the depth of the reproduction signal (the Numerous studies have been made on a method of recording a plurality of data in each signal of the same length by switching the modulation degree of the reflection signal) in multiple stages.

According to this optical recording method, a plurality of data can be recorded in a depth direction as compared with a case where binary data is simply recorded based on the presence or absence of a pit. The amount can be increased. Therefore,
Since the linear recording density can be improved, a method using holography and an optical recording method using a multilayer recording layer have been proposed.

[0004] Here, the case where data is recorded in multiple stages by using the depth variation of the reflectance is called multi-level recording.

[0005]

In such multi-level recording, it is necessary to shorten the recording mark in order to improve the recording density.

However, if the recording mark is to be made smaller than the beam diameter when the laser used for recording / reading is focused, multilevel recording becomes difficult.

For example, Japanese Patent Laid-Open Publication No. Hei 10-134353 discloses that the amount of laser light is adjusted to perform multi-level recording. Here, when the recording medium is a dye film or a phase change film, a reproduction signal is formed by a difference in reflection between a recorded portion and an unrecorded portion. Therefore, Japanese Patent Application Laid-Open No. 10-1
In the method disclosed in Japanese Patent No. 34353, the unrecorded stage and the recorded stage are related to the presence or absence of recording, and are not suitable for multi-stage recording.
More specifically, there is no recorded or unrecorded intermediate state in the phase change film or the dye film.

Hitherto, multi-level multi-level recording has been performed by adjusting the amount of laser light using a dye film or a phase-change film as a recording medium. Because it was.

Although the condensed beam generally has a Gaussian distribution, when the recording film is a dye film or a phase change film, recording is performed in a portion exceeding a certain threshold. By changing the laser power, the spot size of the recordable condensed beam was changed, and the width of the recording mark was changed.

However, when the recording mark length becomes shorter than the converging beam diameter in order to increase the recording density, the laser power is modulated to change the mark width. Becomes difficult.
That is, changing the recording power makes it difficult to change the reflection level during reproduction in five or more steps.

Generally, the diameter of the focused beam is Kλ / NA
(K: constant, λ: laser wavelength, NA: numerical aperture of lens). For example, in the case where the optical recording medium is a CD (compact disk), a pickup used for the CD has a diameter of about 1.6 μm when λ = 780 nm, NA = 0.45. In this case, the recording mark length is 1.6
If the diameter is less than μm, multi-level recording of five or more steps by the conventional method of changing laser power becomes difficult.

Further, as disclosed in, for example, JP-A-1-182846, when the amount of light incident on the recording layer is given as a digital amount, the optical recording in which the absorbance of a reactant in the recording layer changes as a digital amount. There is a medium.

However, it is presumed that this optical recording medium has a very small absolute value of a change in absorbance with respect to the laser irradiation amount (number of times), and has not yet been put to practical use.

Further, as disclosed in JP-A-61-211835, the intensity of irradiation light or the number of times of irradiation of the photochromic material is changed to record at different arbitrary color density states. There is an optical recording method.

However, this optical recording method has a problem that the color density state cannot be read in five or more steps when reading by irradiating a laser beam.

The inventor of the present invention has proposed a method in which at least five steps of multi-level recording can be performed by changing at least one of the laser irradiation time and the irradiation power even under conditions where the recording mark length is shorter than the focused beam diameter. Was found. This method has the advantage that the same recording density can be maintained at the inner and outer circumferences because the disk (recording medium) is rotated at a constant linear velocity, but the rotation speed always changes with the difference in the radial position. Therefore, the recording / reproducing device requires advanced rotation control. This poses a problem in terms of improving the data transfer rate and the access speed.

In view of the above, the present invention provides a CD-R (recordable CD), a CD-R,
It is an object of the present invention to provide an optical recording medium and an optical recording method which have a disk shape such as W (rewritable CD), perform multi-level multi-level recording, and can obtain good signal quality. . Furthermore, not only for video image recording,
An object of the present invention is to provide a multilevel optical recording medium and an optical recording method that can be used for an external storage device of a computer.

[0018]

Means for Solving the Problems The present inventor has conducted intensive studies on an optical recording medium and found a recording method for performing multi-step recording on the optical recording medium. It was confirmed that high-level multi-level recording of five or more stages could be performed while rotating at a constant angular velocity.

That is, the above object can be achieved by the present invention described below.

(1) While rotating around the center of the disc,
A disc-shaped optical recording medium capable of recording information by irradiating a laser beam to form a recording mark on a recording layer, and reading the recorded information by irradiating the recording mark with a reading laser beam. The recording layer has a plurality of virtual recording cells defined by a unit length in a disk rotation direction and a unit width in a direction perpendicular to the disk rotation direction, and are set concentrically or spirally around the center of the disk. The unit length of at least a part of the virtual recording cell is set to be an arc length having the same central angle with respect to the center of the disk regardless of the position in the disk radial direction,
The recording layer in the virtual recording cell is capable of forming recording marks of different sizes corresponding to at least one of the five or more steps of modulation of the irradiation time and irradiation power of the laser beam. An optical recording medium characterized by modulating light reflectance based on at least the area ratio of the area ratio and the light transmittance with respect to a recording cell to enable multi-level recording of information in five or more steps.

(2) The unit length of the virtual recording cell is made longer toward the outer periphery of the disk, and the number of modulation steps of at least one of the irradiation time and the irradiation power of the laser beam on the virtual recording cell is increased toward the outer periphery of the disk. (1) The optical recording medium according to (1).

(3) Two divided virtual recording cells are set in the range of the arc length within a range where the arc length is at least twice the arc length at the innermost side in the radial direction of the disk. The optical recording medium of 1).

(4) A groove for laser beam guide is provided along the recording layer in a concentric shape or a spiral shape with a constant pitch in the disk radial direction, sandwiched between lands provided in parallel with the groove. In the virtual recording cell, the unit width is set in the groove so as to substantially match the width of the groove, and at least one of the information on the number of modulation stages and the information on the divided virtual recording cell includes a groove wobble and a land pre-pit. The optical recording medium according to (2) or (3), which is recorded in advance in at least a part of a pre-signal recording unit including a sample servo.

(5) In at least a part of the pre-signal recording section including the groove wobble, land pre-pit, and sample servo, rotation at the time of recording causes the angular velocity in each virtual recording cell to be constant or the number of rotations to change. (1), (2), (3) or (4), wherein information for keeping the angular velocity in some virtual recording cells constant is recorded in advance.

(6) The unit length of the virtual recording cell at the innermost position in the disk radial direction is set to be equal to or less than the diameter of the beam waist of the read laser beam (1) to (5). An optical recording medium according to any of the above.

(7) An optical recording method for recording information by irradiating a laser beam onto a recording layer having a recording layer and rotating a disk-shaped optical recording medium to form recording marks on the recording layer. In the recording layer, assuming a plurality of virtual recording cells concentrically or spirally around the center of the disk, and the unit length of at least some of the virtual recording cells in the disk radial direction Regardless of the position, the arc length is set to be the same central angle with respect to the center of the disk, and the rotation at the time of recording of at least some of the virtual recording cells is set to a constant angular velocity, and the laser beam is provided for each of the virtual recording cells. At least one of the irradiation time and the irradiation power is modulated in five or more steps, the size of the recording mark formed in the virtual recording cell is changed, and the area ratio to the virtual recording cell and the recording mark are changed. According to at least the area ratio of the light transmittance, the virtual light reflectance of the entire recording cell is modulated, the optical recording method characterized by information to the five stages or more multi-level recording.

(8) The optical recording method according to (7), wherein the number of modulation steps of at least one of the irradiation time and the irradiation power of the laser beam to the virtual recording cell is set longer toward the outer periphery of the disk.

(9) The optical recording method according to (7) or (8), wherein the irradiation power of the laser beam is changed corresponding to the irradiation position in the disk radial direction.

(10) The optical recording method according to (9), wherein the irradiation power is successively increased from the irradiation position on the inner side in the radial direction of the disk to the irradiation position on the outer side.

(11) The recording start position in the virtual recording cell is appropriately allocated to one of front coincidence, center coincidence, and rear coincidence according to the position in the disk radial direction. (7) to (10) Any of the optical recording methods.

(12) The virtual recording cells are assumed to be continuous in the same circular shape around the center of the disk, and the start positions in the disk rotation direction of the virtual recording cells adjacent in the radial direction of the disk are set to be shifted. The optical recording method according to any one of (7) to (10), wherein

In the present invention, the reflectance can be controlled in multiple steps by adjusting at least one of the laser irradiation time and the irradiation power in multiple steps. In other words, by modulating the laser irradiation time and the irradiation power, the size of the recording mark is modulated, and the level of the light reflectance according to the area ratio of the recording mark in a certain area (virtual recording cell) is changed in multiple steps. By doing so, multi-level recording became possible. Also, at this time, the unit length of the virtual recording cell in the disk rotation direction is set to be the same arc length with the same central angle with respect to the disk center regardless of the position in the disk radial direction. High-speed multi-level recording is possible, which enables high-speed data recording / reproduction compared to rotating at a constant linear velocity, and achieves a high access time by simplifying the rotation control method. You can now.

[0033]

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

A disk-shaped optical recording medium 10 according to an embodiment of the present invention has a recording layer
-R or CD-RW using a phase change material, and a substrate 14 made of a transparent base material and one surface of the substrate 14 (FIG. 1).
The recording layer 12 is formed so as to cover a laser beam guide groove 16 formed on the upper surface of the recording layer 12, a reflective film 18 of gold or silver is formed on the recording layer 12 by sputtering or the like. The protective layer 20 covers the outside of the reflective film 18. CD
In the case of -RW, for example, a lower protective layer (dielectric layer) formed at least by film formation so as to cover the groove 16;
A recording layer made of a phase change material, an upper protective layer (dielectric layer),
It includes a light reflecting layer, and further includes a protective layer 20 so as to cover the light reflecting layer.

The grooves 16 are continuously formed spirally or concentrically around the center of the disk shape and at equal pitches in the radial direction of the disk, and between the radially adjacent grooves 16. In parallel, spiral or concentric continuous lands 17 are formed.

The dyes used in the recording layer 12 are organic dyes such as cyanine, merocyanine, methine dyes and derivatives thereof, benzenethiol metal complexes, phthalocyanine dyes, naphthalocyanine dyes, and azo dyes. Are generally GeSbTe-based, AgInSbTe-based, and the like.

The multi-level recording on the optical recording medium 10 is executed by the optical recording device 30 shown in FIG.

This optical recording device 30 is a CD-R / RW recorder, and drives the optical recording medium (disk) 10 to rotate at a constant angular velocity by a spindle motor 32 via a spindle servo 31. The information is recorded on the optical recording medium (disk) 10 by the beam on the recording layer 12 formed as described above.

The laser 36 is driven by a laser driver 38 according to the information (data) to be recorded, as shown in FIG.
The laser beam irradiation time per one virtual recording cell (detailed later) 40 shown in FIG. 3, for example, the number of laser pulses, or the laser beam irradiation power, for example, the laser pulse height or density is controlled. .

Reference numeral 42 in FIG. 2 denotes a recording optical system including an objective lens 42A and a half mirror 42B. Focus tracking of the objective lens 42A is controlled by the focus tracking servo 44 so that the laser beam is focused on the recording layer 12. The movement of the objective lens 42A and the half mirror 42B is controlled by the feed servo 46 from the inner peripheral side to the outer peripheral side at a predetermined speed in synchronization with the rotation of the disk 10.

The spindle servo 31, laser driver 38, focus tracking servo 44, and feed servo 46 are controlled by a controller 50. Recording layer 12
Is input to the control device 50.

Next, the virtual recording cell 40 and the recording marks recorded in the virtual recording cell 40 will be described.

The virtual recording cell 40 is defined to have a radial unit width and a rotational unit length of the recording medium. The unit width is equal to or less than the beam waist diameter of the laser beam at the innermost circumference, and is a width that can be arbitrarily selected, such as the track pitch of the disk 10 or the group width.

More specifically, as shown in FIG. 1, the virtual recording cell 40 of this embodiment is
On the recording layer 12 in 6, the unit length is defined in the rotation direction of the disk 10, that is, in the circumferential direction, and the width is defined to be equal to the groove 16, and a plurality of them are assumed to be continuous spirally or concentrically. It was done.

By irradiating such a virtual recording cell 40 with a laser beam, the recording marks 48A to 48G schematically illustrated in FIG. 3 can be formed in accordance with the information to be recorded.

The unit length is set such that the center angle θ with respect to the center of the disk becomes the same arc length regardless of the position of the virtual recording cell 40 in the disk radial direction.
The absolute length is set to be a length (circumferential length) shorter than the beam diameter (diameter of beam waist) D at the innermost side in the disk radial direction. Accordingly, the unit length of the virtual recording cell 40 becomes longer toward the outside in the disk radial direction, and when the optical recording medium 10 is rotated at a constant angular velocity in each virtual recording cell 40, each virtual recording cell by the laser beam is emitted. Forty scan times are equal.

Here, the beam diameter D of the laser beam emitted from the laser 36 at the position of the recording layer 12 is as follows:
Although it is larger than the width of the virtual recording cell 40,
By selecting the material of the recording layer 12, recording marks 48A to 48G having different diameters can be formed at the center of the laser beam according to the laser irradiation time or the irradiation power (the laser beam is circular. Since the laser beam is irradiated while rotating the optical recording medium 10, the recording mark becomes an oval according to the irradiation time.)

The reason is that the focused laser beam generally has a Gaussian distribution, but the recording layer 12
In, since recording is performed only in a portion where the irradiation energy of the laser beam exceeds a certain threshold, the spot size of the laser beam that can be recorded on the recording layer 12 is changed by changing the irradiation time or irradiation power of the laser beam. This makes it possible to form seven levels of recording marks 48A to 48G as shown in FIG. 3, for example.

In this case, the size of each of the recording marks 48A to 48G is set so that the light reflectance of the reflected light when the virtual recording cell 40 is irradiated with the read laser beam becomes seven levels. The light reflectance increases as the size of the recording mark decreases, and reaches a maximum reflectance in a virtual recording cell where no recording mark is formed, and a minimum reflectance in a virtual recording cell where the maximum recording mark 48G is formed.

More specifically, the light reflectance is set in consideration of the area ratio of each recording mark 48A to 48G to the virtual recording cell 40 and the light transmittance of the recording mark itself.

The light transmittance of the recording marks 48A to 48G themselves is determined by the fact that the material constituting the recording layer 12 is decomposed and deteriorated by the irradiation of the laser beam, or the crystal state is changed.
It depends on the case where the refractive index changes and the amount of change in the thickness direction of the recording layer 12. If the light transmittance of the formed recording mark portion is zero, this need not be considered.

As described above, the unit length of the virtual recording cell 40 becomes longer toward the outside in the disk radial direction, and when the optical recording medium 10 is rotated at a constant angular velocity in each virtual recording cell 40, The scanning times of the virtual recording cells 40 are made equal.

Accordingly, the relative speed of each virtual recording cell 40 with respect to the laser beam, that is, the recording linear velocity becomes faster toward the outer side in the disk radial direction, and when the laser irradiation time is modulated in a plurality of stages, the recording mark at the longest irradiation time The space on the rear side becomes larger toward the outer side in the radial direction of the disk. If the space is large, there is room for increasing the number of modulation stages.

However, the recording laser power itself must be increased correspondingly. In other words, the fact that the light amount irradiated per unit area becomes smaller as the moving distance per unit time becomes longer is compensated for by increasing the laser power.

For example, as schematically shown in FIG. 4, when the laser irradiation time can be modulated in seven stages in the radially inner region of the optical recording medium 10 in the disk radial direction, eight or nine levels can be modulated in the radially outer region of the disk. It can be modulated in stages.

Further, when the cell length, which becomes longer toward the outer periphery of the disk, is more than twice the shortest cell length with respect to the shortest cell length set at the innermost position of the disk. 4, the virtual recording cell can be divided into two divided virtual recording cells 40A, 40B. This makes it possible to improve the recording density.

Further, when the virtual recording cell is set under the condition of the constant angular velocity as described above, the starting position of the virtual recording cell becomes the same as the next groove adjacent to the land in the radial direction with the land interposed therebetween. It is suggested that phenomena such as crosstalk may occur when reading and writing data. In such a case, the position of the virtual recording cell is kept as it is, and the signal start position in the virtual recording cell is forward-coincident as shown by a solid line in FIG. As shown by, it is possible to solve the problem by sorting such as backward matching.

In the above-described embodiment, the length (unit length) of the virtual recording cell 40 in the circumferential direction of the disk is used.
Is the shortest in the innermost region in the disk radial direction, and when the shortest length is an arbitrary length equal to or less than the beam waist diameter of the laser beam, it is approximately equal to the beam waist diameter at an intermediate position in the disk radial direction. Is good.

In the case of the longest irradiation time of the laser beam, the virtual recording cell 40 may be set to have a length substantially equal to a recording mark formed when the irradiation energy exceeds a threshold value that changes the recording layer 12. .

Further, as described below, if the length of the laser beam in the lengthwise direction of the virtual recording cell 40 can be reduced, the virtual recording cell at the outermost position in the disk radial direction on the recording medium 10 can be obtained. The unit length of 40 can be equal to or less than the beam waist diameter of the laser beam.

The laser beam has a circular shape at the position of the recording layer 12, and this is, for example, as shown in FIG.
By adding C or an aperture (not shown) or the like, the beam shape may be an oval shape or a linear shape that is short in the feed direction of the recording medium 10 and long in a direction perpendicular to the feed direction. In this case, since the recording mark 49 is shortened, the virtual recording cell can be further shortened. That is, the recording density can be improved.

In the above-described embodiment, the optical recording medium 10 is
Although the present invention is applied to a disk as R, the present invention is not limited to this, but is generally applied to other optical recording media.

In the above embodiment, the recording layer 12 uses an organic dye such as cyanine or a phase change material. However, the present invention is not limited to this. A recording layer other than those described above may be used as long as recording marks having different sizes can be formed in five or more steps corresponding to the irradiation time of the laser beam.

However, when the above-mentioned organic dye was used, it was possible to reliably change the size of the recording mark and record in accordance with the irradiation time of five or more steps of the laser beam.

Furthermore, the example of the above embodiment is for the optical recording medium 10 on which information such as data is not recorded. However, the present invention is not limited to this, and the information Is also applied to a read-only optical recording medium on which multi-level recording is performed.

Further, in the optical recording medium 10, information for individually identifying the recording medium, information for identifying the optical recording medium for multi-level recording, and information for identifying the recording medium are stored in a pre-signal recording section (to be described in detail later). Information for determining the power of the laser beam for recording / reproducing, information on the laser irradiation time or the number of modulation steps of the irradiation power, all or a part (CA
V or ZCAV), which has specific information such as information in which the rotational angular velocity of the virtual recording cell 40 is constant, and reads the specific information at the time of reproduction and / or recording of the optical recording medium, thereby enabling optical recording for multi-level recording. Since it is possible to reliably identify that the medium is a medium, to further identify them individually, and to determine the number of laser beam power levels according to the number of previously recorded pit steps, a more reliable Multi-level recording and reproduction can be performed.

Normally, CD-R / RW and DVD-R / RW
The medium for recording contains signals by making the recording groove meander (wobble). This signal is called an address signal, and the recording apparatus can move the recording head to a predetermined position by reading this signal.

For example, in the case of a CD-R / RW, a time code of minutes and seconds in which the position is replaced by time is recorded in this address signal. The recording device reads the time code, moves the head to the lead-in portion, and can read various data.

The multi-level optical recording medium of the present invention
When used (recording / reproducing) in a recording apparatus applied to DR / RW, an address signal based on wobble can be employed. However, a signal system such as an address code which is different from a normal CD-R / RW time code is adopted. In a normal recording device, an address signal different from that of a CD-R / RW cannot be read, and the head cannot be moved to a predetermined position (in this case, the multi-level recording optical medium is ejected from the recording device).

On the other hand, in a recording apparatus compatible with multi-level recording, if this special address is set to be recognizable, the signal can be read by moving the head to the lead-in portion.

That is, the multi-level optical recording medium can be distinguished from other optical recording media by adopting an address different from usual.

The recording using the wobble is performed by modulating the wobbles (see reference numeral 56A in FIG. 1) of the grooves 104A to 104C in the lead-in area 102 of the optical recording medium 10, as shown in FIG. .

More specifically, as shown in FIG. 7, each groove 104 is not changed without changing the wobble amplitude Wb.
A, 104B, 104C wobble periods T _A , T _B , T _C
change. For example, the user area 10 shown in FIG.
6, the wobble period T _O of the groove 16 is set as the basic period, the longer wobble period T _B is “1”, and the shorter wobble periods T _A and T _C are “0” on a binary signal.
The above various information is recorded. Therefore, for example, when the wobble period is “0”, “1”, or “0” from the inner peripheral side of the optical recording medium as described above,
Is for multi-level recording.

Further, the predetermined information as described above is
As the recording start position information, the recording is started from a predetermined position in the user area 106 based on the information. This is also information on the start position of the virtual recording cell 40.

As an example of another recording method of the above-mentioned various information, as shown in FIG. 8, the above-mentioned various information is transferred to land pre-pits 17A (FIG. 1) formed on lands 17 between the grooves 16. 56B), for example,
When the period between land pre-pits is short, the value is recorded as "1", and when the period is long, it is recorded as "0".

As still another example, as shown by reference numeral 56 in FIG. 9 or FIG. 0 ".

The information recorded by the information recording means shown in FIGS. 6, 8 and 9 can be read by a conventional binary recording type reproducing apparatus. Even if it is loaded in a binary recording type reproducing and / or recording device by mistake, it is easily found that this is a multi-level type.

Further, the various information described above is, for example, as shown in FIG.
As shown in (1), multi-level recording can be performed in the lead-in area 102 in advance. In this case, FIG.
, The recording marks of the first five virtual recording cells 401 to 405 indicate that the medium is a multi-level recording medium, the number of stages of multi-level recording, the next five virtual recording cells 4
It is possible to record the recommended laser power for recording or reproduction by using the recording marks 06 to 410, for example.

As the pre-signal recording section, the wobble, land pre-pit, etc., or sample servo is used alone or in combination.

The sample servo has a plurality of pits having different reflectivities in advance corresponding to the number of signal modulation stages, or a multi-level recording in which a multi-level recording has been previously performed on a part of the optical recording medium as described above. Means the recorded mark 54 (see FIG. 1) of the completed portion.

[0081]

EXAMPLES Examples of the present invention will be described below together with comparative examples to explain the present invention.

Here, the recording layer 12 is used as the recording medium 10.
Using a CD-R with a dye, the radius of the disc 25
The recording time was modulated at the positions of mm and 50 mm, and an experiment of multi-level recording of 6 steps (6 steps and 8 steps in Example 5) was performed.

The conditions and results of Examples 1 to 7 and Comparative Example are as shown in Table 1 below, and it was confirmed that the transfer rate was high and the access time was shortened. Note that the recording linear velocities of Examples 1 to 7 were 10.5 at a position of a radius of 25 mm and 21.0 m / sec at a position of a radius of 50 mm, and were equal angular velocities.

[0084]

[Table 1]

[0085]

According to the present invention, a laser beam is irradiated onto a disk-shaped optical recording medium having a recording layer at an irradiation time or irradiation power of at least five steps while rotating the laser beam so that the angular velocity at the laser beam irradiation position is constant. By using a recording method of performing multi-level recording of data to be recorded by irradiating the recording layer, it becomes possible to perform multi-level recording in five or more steps in the depth direction of the reflectance change of the recording layer. This makes it easier to control the rotation of the drive and achieves a high transfer rate and a shortened access time, as compared with the case where the disk is rotated at a constant linear velocity.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional perspective view showing a main part of an optical recording medium according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an optical recording apparatus for recording information on the optical recording medium using a laser beam.

FIG. 3 is a schematic diagram showing a relationship between the recording mark, a virtual recording cell, and its light reflectance when a recording mark is formed on a recording layer by the optical recording apparatus.

FIG. 4 is a schematic diagram showing another setting mode of a virtual recording cell in an optical recording medium.

FIG. 5 is a schematic perspective view showing a case where a laser beam for irradiating a virtual recording cell has another shape.

FIG. 6 is an enlarged schematic diagram showing a wobble in which various information is recorded in advance on the optical recording medium of the present invention.

FIG. 7 is a diagram showing a relationship between a wobble cycle of the wobble and a binary signal;

FIG. 8 is a schematic diagram showing a relationship between a land prepit on which various information is recorded and a binary signal in the optical recording medium of the present invention.

FIG. 9 is a schematic diagram showing the relationship between the length of a groove interrupted by recording various information in the optical recording medium of the present invention and a binary signal.

FIG. 10 is a schematic diagram showing virtual recording cells and recording marks on which various information is recorded in the optical recording medium of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Optical recording medium 12 ... Recording layer 14 ... Substrate 16, 104A-104C ... Groove 18 ... Reflective film 20 ... Protective layer 30 ... Optical recording device 31 ... Spindle servo 32 ... Spindle 36 ... Laser 38 ... Laser driver 40, 401-401 410 virtual recording cell 42 recording optical system 42A objective lens 42B half mirror 42C beam shaping prism 44 focus servo circuit 46 feed servo circuit 48A to 48I, 49, 54 recording mark 50 control device 52 pit 56A: Wobble 56B: Land pre-pit D: Beam diameter θ: Central angle

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) G11B 7/24 563 G11B 7/24 563A 563M (72) Inventor Takashi Doi 1-13 Nihonbashi, Chuo-ku, Tokyo No. 1 Inside TDK Corporation (72) Inventor Shiro Otsuki 1-13-1, Nihonbashi, Chuo-ku, Tokyo F-term within TDK Corporation 5D029 WA02 WA20 WA21 WA29 5D090 AA01 BB03 BB05 CC01 DD03 FF13 GG03 GG32 KK01 KK03 KK05 5D119 AA22 BA01 BB02 BB04 DA01 EB04 HA20 HA45 HA59 JA07

Claims (12)

[Claims] An information recorded by forming a recording mark on a recording layer by irradiating a laser beam while rotating about a center of the disk, and irradiating a reading laser beam to the recording mark to record the information. A disk-shaped optical recording medium capable of reading a disk, wherein the recording layer has a unit length in a disk rotation direction and a unit width in a direction perpendicular to the disk rotation direction, and is concentrically or spirally continuous around the disk center. A plurality of virtual recording cells set as described above, and at least a unit length of the virtual recording cell is an arc length having the same central angle with respect to the center of the disk regardless of the position in the disk radial direction. The recording layer in the virtual recording cell is set to be large in accordance with at least one of five or more modulations of the irradiation time and the irradiation power of the laser beam. It is possible to form recording marks of different lengths, thereby modulating the light reflectance based on at least the area ratio of the recording marks to the virtual recording cell and the light transmittance, and multi-level recording of information in five or more steps. An optical recording medium characterized by being able to perform. 2. The method according to claim 1, wherein the unit length of the virtual recording cell is made longer toward the outer periphery of the disk, and at least one of the number of modulation steps of the irradiation time and the irradiation power of the laser beam with respect to the virtual recording cell is changed to the disk. An optical recording medium characterized in that the number can be increased toward the outer peripheral side. 3. The method according to claim 1, wherein two divided virtual recording cells are set in the range of the arc length within a range where the arc length is at least twice the arc length at the innermost side in the disk radial direction. An optical recording medium characterized by the following. 4. A disk according to claim 2, wherein a groove for laser beam guide is sandwiched between lands provided in parallel with the recording layer along the recording layer so as to be concentric or at a constant pitch in the disk radial direction. Helically provided, the virtual recording cell, the unit width is set in the groove substantially coincident with the width of the groove, at least one of the information of the number of modulation stages, information of the divided virtual recording cell, An optical recording medium recorded in advance in at least a part of a pre-signal recording section including a groove wobble, a land pre-pit, and a sample servo. 5. A recording device according to claim 1, wherein at least a part of a pre-signal recording unit including a groove wobble, a land pre-pit, and a sample servo is rotated during recording.
An optical recording medium, characterized in that information is recorded in advance in which the angular velocity in each virtual recording cell is constant or partially changed in rotational speed, and the angular velocity in some virtual recording cells is constant. 6. The apparatus according to claim 1, wherein the unit length in the innermost position of the virtual recording cell in the radial direction of the disk is equal to or less than the diameter of the beam waist of the reading laser beam. Optical recording medium. 7. An optical recording method which has a recording layer and irradiates a laser beam onto the recording layer while rotating a disk-shaped optical recording medium to form a recording mark on the recording layer to record information. In the recording layer, a plurality of virtual recording cells are assumed to be concentrically or spirally continuous around the center of the disk, and a unit length of at least a part of the virtual recording cells is set to a position in a disk radial direction. Irrespective of the center of the disc, the arc length is set to be the same central angle, and the rotation at the time of recording of at least some of the virtual recording cells is set to a constant angular velocity. At least one of the irradiation time and the irradiation power is modulated in five or more steps, the size of the recording mark formed in the virtual recording cell is changed, and the area ratio to the virtual recording cell and the light transmission of the recording mark are changed. At least by the area ratio, by modulating light reflectance across the virtual recording cell, the optical recording method characterized by information to the five stages or more multi-level recording of rates. 8. The optical recording method according to claim 7, wherein the number of modulation steps of at least one of the irradiation time and the irradiation power of the laser beam to the virtual recording cell is set to be larger toward the outer periphery of the disk. 9. The optical recording method according to claim 7, wherein the irradiation power of the laser beam is changed in accordance with the irradiation position in the disk radial direction. 10. The method according to claim 9, wherein the irradiation power is
An optical recording method characterized by sequentially increasing the size from the inner irradiation position to the outer irradiation position in the disk radial direction. 11. The method according to claim 7, wherein
An optical recording method, wherein a recording start position in the virtual recording cell is appropriately allocated to one of front coincidence, center coincidence, and rear coincidence according to a position in a disk radial direction. 12. The method according to claim 7, wherein
The virtual recording cells are assumed to be continuous in the same circular shape around the center of the disk, and the start positions in the disk rotation direction of the virtual recording cells adjacent in the radial direction of the disk are set to be shifted. Recording method.