JP2002312937A - Optical recording method and optical recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical recording method capable of realizing multilevel recording of >=5 levels in addition to reducing the error rate. SOLUTION: This optical recording method for irradiating a recording layer 12 in an optical recording medium 10 with laser beams and recording information, is to continuously define a plurality of virtual recording cells 40 to be an optional unit length H and an optional unit width B in orthogonally crossing direction in a relative displacement direction with respect to the laser beams in the recording layer 12, to irradiate the recording layer with laser beams by controlling at least either emitting time or emitting power to be >=5 levels while applying angle control to at least a light emission optical system so as to suppress incident angle fluctuation to the recording layer 12, to form >=5 types of recording marks 48A to 48G different in size on the virtual recording cells 40, and to record information on a multilevel while making it possible to modulate the entire optical reflectance of the virtual recording cells 40 in >=5 levels on the basis of the occupancy ratio of the recording marks 48A to 48G to the virtual recording cells 40.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording method and an optical recording apparatus for forming a plurality of types of recording marks on a recording layer of an optical recording medium in accordance with data to be recorded, thereby performing multi-level recording of information.

[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 depth of the reproduction signal) is reduced. Many 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, and therefore, the linear recording density can be improved. At present, as a recording medium, a recording medium utilizing holography and a recording medium having a multilayer recording layer have been proposed.

[0004] Here, recording of a plurality of types of recording data having different degrees of modulation of the reflection signal is called multi-level recording.

[0005]

On the other hand, the optical recording method relating to these multi-level recordings, as the power of the laser beam at the time of recording increases, that is, as the depth of the reflection signal to be formed becomes deeper, the reproduction at the time of reproduction is performed. There was a problem that signal quality deteriorated. The reason for this has not been disclosed at this time.

For example, when a recording mark is shortened to increase the recording information amount of a recording medium by using the conventional method, and the power of the laser beam is switched in multiple stages, multi-level recording is performed. The signal quality deteriorated remarkably. In other words, if multi-level recording is to be adopted, it is difficult to increase the density of the recording marks, resulting in an incompatible situation.

In the conventional concept of an optical recording method for performing multi-level recording by switching the power of a laser beam stepwise, the recording mark length is larger than the diameter of a focused beam (beam waist) at the time of recording. It is a premise. In other words, the light reflectance of the recording mark itself is modulated in multiple stages,
Attempts are made to realize multi-level recording by directly reading the reflectance.

In general, the diameter of the focused beam is Kλ / NA
(K: constant, λ: laser wavelength, NA: numerical aperture of lens). In a pickup used in a CD, λ = 780 nm and NA = 0.45 are generally used, and the diameter of a condensed beam is about 1.6 μm. In this case, when the recording mark length is near 1.6 μm, the above-described problem of signal deterioration becomes apparent, and multi-level recording of five or more steps is difficult.

The above problem is considered to be the result of complicated intertwining of all factors such as the power setting of the laser beam and the characteristics of the recording medium. However, as far as the inventor knows, the cause has not been clarified at present. In fact, high-density multi-level recording has not been achieved, including its recording method.

The present invention has been made in view of the above problems, and has as its object to propose a new multilevel recording method and achieve high density multilevel recording.

[0011]

As a result of intensive studies on the optical recording technique, the present inventors have found a recording method and a recording apparatus capable of performing multi-step recording, and by this, have provided a high-density recording medium having five or more steps on an optical recording medium. It was confirmed that multi-level recording could be performed.

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

(1) Optical recording in which a recording layer of an optical recording medium is irradiated with a laser beam condensed by an irradiation optical system and a recording mark is formed on the recording layer by the laser beam to record information. In the method, a plurality of virtual recording cells having an arbitrary unit length in the moving direction and an arbitrary unit width in a direction orthogonal to the moving direction are continuously formed in the direction of relative movement with the laser beam in the recording layer. And controlling at least one of the irradiation time or the irradiation power to five or more stages while controlling the angle of the irradiation optical system so as to suppress the fluctuation of the incident angle of the laser beam with respect to the recording layer. To form five or more types of recording marks having different sizes in the virtual recording cell, and based on the occupation ratio of the recording mark in the virtual recording cell, Optical recording method characterized by information as possible modulate the light reflectance of the entire recording cell than 5 out multi-level recording.

(2) An optical recording apparatus, wherein at least the irradiation optical system is angle-controlled so that an incident angle of the laser beam with respect to the recording layer falls within a predetermined range.

(3) When irradiating the laser beam to a part of the recording layer in which the plurality of virtual recording cells are set, at least the irradiation optical system is angle-controlled. Optical recording method.

(4) A laser for outputting a laser beam, an irradiation control device capable of controlling the laser, an irradiation optical system for condensing the laser beam, and positioning at least the laser and the irradiation optical system for positioning the laser beam. A servo mechanism that can irradiate a predetermined position of the recording layer with the laser beam; and an optical recording apparatus capable of recording information by forming a recording mark on the recording layer by irradiating the laser beam. The apparatus continuously arranges a plurality of virtual recording cells having an arbitrary unit length in the moving direction and an arbitrary unit width in a direction orthogonal to the relative moving direction in the direction of relative movement with the laser beam in the recording layer. While stipulating, at least one of the irradiation time and the irradiation power is changed in five or more steps so that the laser beam can be irradiated to the virtual recording cell. A servo mechanism, a tilt sensor capable of measuring the amount of inclination of the virtual recording cell in the recording layer, and at least controlling the inclination of the irradiation optical system so as to follow the amount of inclination, so that the laser beam is transmitted to the recording layer. And a tilt mechanism for suppressing a change in the incident angle of the virtual recording cell. The laser beam forms five or more types of recording marks having different sizes in the virtual recording cell, and the recording mark for the virtual recording cell is formed. An optical recording apparatus capable of modulating the light reflectance of the entire virtual recording cell in five or more steps based on the occupancy of the virtual recording cell to enable multi-level recording of information.

(5) The optical recording characterized in that the tilt mechanism of the servo mechanism controls the inclination of the irradiation optical system so that the incident angle of the laser beam on the recording layer falls within a predetermined range. apparatus.

(6) When the tilt mechanism section of the servo mechanism irradiates a laser beam to a partial area of the recording layer in which the virtual recording cell is defined, the tilt optical system controls the tilt of the irradiation optical system. An optical recording device, comprising:

The present inventor has discovered that multilevel recording can be performed by a new modulation method called the occupation ratio of recording marks to virtual recording cells. As a result, the recording density can be dramatically increased.

However, simply forming a recording mark by modulating the irradiation time or the irradiation power,
It has been found that the recorded mark cannot be read reliably.

One of the reasons is that the present recording method requires that the light reflectance of the entire virtual recording cell be controlled with high accuracy. According to the inventor's detailed study,
Compared with the conventional binary recording, the multi-level recording is more susceptible to the warpage of the optical recording medium, which is presumed to be one of the causes for increasing the error occurrence rate.

In particular, when the numerical aperture of the objective lens in the irradiation optical system is NA, the wavelength of the laser beam is λ, and the unit length of the virtual recording cell is set smaller than 0.65 × (λ / NA). It is assumed that a recording mark smaller than the beam spot is included, in which case the center of the beam spot passes as accurately as possible on the center line of a plurality of virtual recording cells defined continuously. Is required. The reason is that, in the case of a beam spot having a Gaussian distribution of irradiation intensity, recording marks are gradually formed from the center.

In this case, wavefront aberrations (mainly coma and astigmatism) occur unless the optical axis of the irradiation optical system (for example, an objective lens) is always maintained in a constant relationship with the perpendicular to the recording surface. In addition, the focusing of the laser beam becomes insufficient, and the center of the beam spot deviates from the center of the virtual recording cell. Therefore, an error occurs in the position and size of the recording mark, and it becomes difficult to set the occupation ratio of the recording mark to the virtual recording cell as scheduled, which greatly affects the light reflectance of the entire virtual recording cell.

In order to solve these problems, it is also necessary to increase the mechanical accuracy of the optical recording medium itself, that is, to make the optical recording medium such that the amount of warpage, the amount of deflection, and the angle of deflection fall within predetermined ranges. Conceivable. According to the experiment of the present inventor, for example, an optical recording medium of a CD type was fixed to a warpage measuring device, and the plane of the optical recording medium (having a diameter of 45 mm to 118 mm) was used.
The maximum displacement value (plus side) or the minimum displacement value (minus side) in the direction perpendicular to the surface (in the range of (1)) is the reference surface (axial direction (upward) from the chatting reference surface to the recording surface side).
It was confirmed that good recording could be performed within a range of ± 0.3 mm with respect to an ideal plane at a position of 2 mm (see CD-DA standard 6.1).

Further, the run-out width measured by the above method (the maximum run-out width in the direction perpendicular to the plane of the medium when the optical recording medium makes one rotation) is 4 mm or less, that is, the position at the middle of this run-out ± one-way deflection with respect to the virtual average plane
It was confirmed that good recording could be performed if the thickness was 0.2 mm or less (see CD-DA standard 6.2).

Further, the optical recording medium is fixed to the warpage measuring device, and the angle between the optical recording medium plane and the reference plane (ideal plane located 1.2 mm above the chucking reference plane) is 45 mm to 118 mm in diameter. Within 0.4degrees
It was confirmed that good recording could be performed if the following conditions were satisfied (refer to CD-DA standard specification 6.3).

However, the production of all optical recording media in this manner has a large load on the process, and may increase the manufacturing cost.

Therefore, the present inventors have attempted to perform good recording / reproducing from the direction of devising a recording / reproducing method.

In the present invention, when forming a recording mark,
Since the laser beam follows the inclination of the recording layer, it is possible to suppress the variation of the incident angle of the laser beam, and it is possible to form a recording mark accurately on the center line in the virtual recording cell. As a result, an error in the light reflectance of the virtual recording cell based on the inclination of the recording layer is suppressed, and multi-level recording with a small error ratio is achieved. The invention is not limited to the case where the optical axis of the laser beam is perpendicular to the recording layer, and the present invention also includes a case where the laser beam is optimized in a state where it always makes a certain angle difference with the perpendicular. I have.

The above can be confirmed to be particularly remarkable and useful when information is recorded by modulating the light reflectance in five or more steps (compared to the case where the number of steps is less than that). ing. Note that the present invention includes not only the case where the incident angle control is performed over the entire area of the optical recording medium but also the case where the incident angle control is performed only on a specific area (for example, an area where warpage easily occurs) in the optical recording medium. (Invention (3),
(6) etc.).

[0031]

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

The optical recording medium (disk) 10 used in the embodiment of the present invention is a CD-R using a dye material for the recording layer 12 or a CD-RW using a phase change material.
In the case of a CD-R, for example, a substrate 14 made of a transparent base material
And the recording layer 12 made of a dye applied to cover a laser beam guide groove 16 formed on one surface (the upper surface in FIG. 1) of the substrate 14, and sputtering or the like on the upper side of the recording layer 12. And a protection layer 20 covering the outside of the reflection film 18. CD-RW
In the case of, for example, a lower protective layer (dielectric layer) formed at least by film formation, a recording layer made of a phase change material, an upper protective layer (dielectric layer), and a light reflecting layer are formed so as to cover the groove 16, Further, it is formed to include a protective layer 20 covering this.

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.

The optical recording device 30 is a CD-R / RW recorder, and the optical recording medium (disk) 10 is rotated by a spindle motor 32 via a spindle servo 31 at a constant linear velocity. Information is recorded on the optical recording medium (disk) 10 by a laser beam.

The laser driver (irradiation control device) 38
In accordance with the information to be recorded, the irradiation time of a laser beam per one virtual recording cell (details will be described later) 40 shown in FIG. 1, for example, the number of laser pulses input to the laser 36 is controlled. .

Reference numeral 42 in FIG. 2 denotes an objective lens 42A, a half mirror 42B, a light receiving objective lens 42D,
D is an irradiation optical system. The objective lens 42A is controlled by a focus tracking servo 44 so that the laser beam is focused on the recording layer 12 of the disk 10.

The reflected light from the optical recording medium 10 is refracted at a substantially right angle by the half mirror 42B, enters the light receiver FD via the light receiving objective lens 42D, and is read as a multilevel signal. The entire irradiation optical system 42 is positioned by the servo mechanism 42.

The servo mechanism 42 includes a feed servo mechanism 4
6. Tilt servo mechanism 47A and tilt sensor 42B
It has. The feed servo mechanism 46 includes the irradiation optical system 4.
2 is controlled to move in the radial direction from the inner peripheral side to the outer peripheral side while synchronizing with the rotation of the optical recording medium 10. The tilt sensor 42B measures the amount of tilt of the optical recording medium 10 and inputs it to the tilt servo mechanism 47A. Tilt servo mechanism 4
7A controls the inclination of the irradiation optical system 42 based on the signal, and adjusts the optical axis of the irradiation optical system 42 to the perpendicular of the optical recording medium 10 (meaning the perpendicular of the virtual recording cell 40). The servo mechanism 42 itself is controlled by a control device (not shown).

FIG. 3 shows the servo mechanism 42 in this embodiment.
It is shown enlarged.

The tilt servo mechanism 47A is provided with a slider 70 provided swingably about a fulcrum P provided at one end, and a rack 70 provided at the other end of the slider 70 and capable of moving the other end up and down. A pinion 72, and the inclination of the slider 70 causes the irradiation optical system 42 to follow the inclination of the optical recording medium 10. The longitudinal direction of the slider 70 matches the radial direction of the optical recording medium 10.

The feed servo mechanism 46 has a table 74 movable on the slider 70, and its movement is controlled by a drive device (not shown). This table 74
An irradiation optical system 42 is mounted on the upper side. The table 74 further includes a tilt angle detection laser 76 for irradiating a laser beam toward the optical recording medium 10, at least two tilt sensors 47B for detecting reflected light of the laser beam from the optical recording medium 10, Is installed. The difference between the perpendicular line in the recording layer 12 of the optical recording medium 10 and the optical axis of the irradiation optical system 42 can be detected from the difference in the amount of reflected light from both tilt sensors 47B.

Although the amount of deviation between the perpendicular to the recording layer 12 and the optical axis is measured here, the recording layer 1 is directly measured.
The angle of inclination 2 may be made measurable. Although the case where the perpendicular and the optical axis coincide with each other is shown here, the present invention includes a case where the angle is always constant.

As specifically shown in FIG. 4, the laser driver 38 includes a cell time setting section 60, a recording irradiation time setting section 62, and a distribution processing section 64.

The cell time setting section 60 has a predetermined cell time T
(T1, T2, T3, T4, T5,
T6, ...). As a result, for example, assuming that the moving speed (linear velocity) of the optical recording medium 10 with respect to the laser 36 is v, virtual recording cells 40 having a length H of “v × T” are continuously formed on the optical recording medium 10. Stipulated.

The recording irradiation time setting section 62 specifies irradiation times tA,..., TG of five or more steps (here, seven steps from tA to tG) within the cell time T. in this case,
The irradiation times tA,..., TG are recorded in a memory in advance,
It may be specified by reading it out.
It may be defined by reading the recording irradiation time information written in 0.

The distribution processing unit 64 modulates the original information stored in the control device 50, sets a bit sequence for multi-level recording, and allocates it to each cell time T. Here, the bit sequence for multi-levels has seven stages (A,
Since there are recording marks B, C, D, E, F, G), for example, {B, E, D, C, G, G,. Each numerical value means the level of a recording mark formed in each recording cell 40. Therefore, the irradiation times tA to tA are set so as to correspond to the respective levels of the bit sequence.
G are assigned to each cell time T1, T2,.

As shown in FIG. 1, in the optical recording medium 10, virtual recording cells 40 are continuously defined in the groove 16 in the circumferential direction S of the disk 34 (that is, in the longitudinal direction of the groove 16). . The unit length of each virtual recording cell 40 in the circumferential direction S is H (= v × T), and is set to a length shorter than the beam diameter (diameter of beam waist) D (see FIG. 5).

The unit width B of the virtual recording cell 40, which is a direction orthogonal to the unit length H (= v × T), substantially matches the width W of the groove 16.

When the wavelength of the laser beam in the laser 36 is λ and the numerical aperture of the objective lens 42 A in the irradiation optical system 42 is NA, the width W of the groove 16 is
Is 0.20 × (λ / NA) <W <0.50 × (λ / N
A) is set. For example, in this embodiment, since λ = 785 (nm) and NA = 0.5, the groove width W is set in the range of 0.31 <W <0.79 (μm).

The unit length H of the virtual recording cell 40 is
H <0.65 × (λ / NA) is set, and under the above conditions, H <1.02 (μm). In this embodiment, the interval (track pitch) P between the adjacent grooves 16 is 0.5 × (λ / NA) <P <1.2 × (λ
/ NA).

Each of the virtual recording cells 40 is irradiated with a laser beam, and the recording marks 48A to 48G schematically illustrated.
Is formed according to the information to be recorded.

Specifically, the recording marks 48A to 48G are formed by including the following steps.

When real information is recorded on the optical recording medium 10, the virtual recording cell 40 is continuously defined by setting the cell time T as described above, and the virtual recording cell 40
Are set for the laser beam irradiation times tA to tG.

As a result, as shown in the time chart of FIG. 6, the bit sequence {B,
Each cell time T corresponding to E, D, C, G, G,.
The irradiation time ΔtB, tE, tD,
tC, tG, tG,... Here, the case where the irradiation time t is set from the beginning of each cell time T (that is, the leading end reference) is shown, but the case where the irradiation time t is set at the center of each cell time T (intermediate reference), or each cell time T There may be a case where the irradiation time is set on the basis of the rear side of T (the rear end reference).

According to this time chart, the irradiation time t
Irradiates a laser beam on the recording mark 4
By forming 8A to 48G, the entire virtual recording cell 40 can be set to the desired light reflectance.

The recording marks 48A to 48G are formed not at the entire beam spot of the laser beam but at the center thereof (the laser beam is circular,
Since the laser beam is irradiated while rotating the recording mark, the recording mark becomes oval according to the length of the irradiation time.)

The reason for this is that the focused laser beam generally has a Gaussian distribution. However, in the recording layer 12, recording is performed only at a portion where the irradiation energy of the laser beam exceeds a certain threshold value. This is because the recording marks 48A to 48G are formed so as to spread out. As a result, for example, as shown in FIG. 5, seven levels of recording marks 48A to 48G having different occupation rates can be formed in the virtual recording cell 40.

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 readout laser beam is applied to the virtual recording cell 40 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,
It is considered that the light reflectance is determined by the occupancy of the virtual recording cell 40, including the light transmittance of each of the recording marks 48A to 48G.

The light transmittance of the recording marks 48A to 48G itself is determined by the case where the material constituting the recording layer 12 is decomposed and deteriorated by the irradiation of the laser beam to change its refractive index, or the thickness direction of the recording layer 12. Depends on the amount of change. If the light transmittance of the formed recording mark portion is zero, this need not be considered, and only the occupation ratio is used.

According to the optical recording method of the above embodiment, multi-level recording of five or more stages can be achieved by controlling the irradiation time while tilting the irradiation optical system 42.

The reason why the tilt control becomes an important factor in the multi-level recording is as follows.

FIG. 7 shows a state of formation of the recording marks 48A to 48G when the tilt control is not performed. This multi-level recording method of modulating the light reflectance by the occupancy of the recording marks 48A to 48G with respect to the virtual recording cell 40 uses the recording mark 4 for the laser beam spot D
8A to 48G may be small. Therefore, there is a high possibility that the recording marks 48A to 48G are formed beyond the virtual recording cell 40 only by slightly shifting the laser beam spot position due to the coma aberration caused by the warpage or the like of the optical recording medium 10. As a result, the occupancy of the recording marks 48A to 48G with respect to the virtual recording cell 40 is not set as planned, and an error occurs in the entire light reflectance.

Further, it can be inferred from the phenomenon peculiar to the formation of the recording marks 48A to 48G that good recording can be performed if there is no warp as shown in FIG. 8A, whereas FIG. In the case where the warp is large as shown in (1), the recording marks 48A to 48G are inclined. This is schematically written, but there is no problem as long as it is based on the presence or absence of a signal as in the conventional binary recording. However, in the case of multi-level recording, the occupation ratio of the recording marks 48A to 48G is set in multiple stages with high accuracy, so that a jitter component at a shallow position of a recording signal or a jitter component at a deep position (signal shift) causes Overall, the jitter increases (the error of the occupation ratio increases), and it becomes difficult to perform good recording.

Further, if a phenomenon peculiar to reproduction is inferred, as shown in FIG. 9A, a good reproduction signal can be obtained if there is no warp, as shown in FIG. 9B. When the warp is large as shown in FIG.
A to 48 G are read, and the influence of crosstalk increases. This phenomenon leads to deterioration of the reproduced signal.

On the other hand, in the present embodiment, the shift amount (shift angle) between the optical axis of the laser beam at the time of recording or reading and the perpendicular of the recording layer 12 (virtual recording cell 40) of the optical recording medium 10.
Is detected by the tilt sensor 47B, and the irradiation optical system 42 is tilt-controlled so that the deviation is always minimized. Therefore, the recording mark can be accurately recorded along the center line C (see FIG. 1) of each virtual recording cell 40. 48A to 48G can be formed.

As a result, the light reflectance of the entire virtual recording cell 40 can be set with high accuracy, and in addition to this, the size of the virtual recording cell 40 (particularly in the width direction)
Can be made more compact, and the recording density of the optical recording medium 10 can be dramatically improved.

For example, when the numerical aperture of the objective lens in the irradiation optical system 42 is NA and the wavelength of the laser beam is λ, the unit width B of the virtual recording cell is set smaller than 0.5 × (λ / NA). And the track pitch can be set smaller than 0.7 × (λ / NA).

When the error (deviation) of the light reflectance of the entire virtual recording cell 40 is suppressed as described above, the level step width is reduced to reduce the total number of levels (here, 7 to 7 of A to G).
) Can be increased, and the recording density of the optical recording medium can be further increased.

In this embodiment, the case where the recording layer 12 of the optical recording medium 10 is mainly made of an organic dye material and functions as a CD-R has been described, but a phase change recording layer is adopted as the recording layer. A CD-RW type optical recording medium may be used, or an optical recording medium other than a CD-R / RW may be used.

In the embodiment of the present invention, as shown in FIG. 4, the recording marks having a length or width equal to or less than the diameter D of the condensed beam of the reading laser (in this case, all the recording marks 4).
8A to 48G), it is possible to read data sufficiently, so that the recording density per unit area is drastically increased as compared with the related art.

In the example of the present embodiment, the case where all the recording marks are set to have the diameter D or less of the converging beam is shown.
The present invention is not limited to this, and includes a case where only a part of the recording marks has a diameter of D or less, and a case where all the recording marks have a diameter of a condensed beam or more.

In the optical recording apparatus 30, the case where the laser beam irradiation time is set using the laser driver 38 has been described. However, recording marks of different sizes may be formed depending on the irradiation power. In the present invention, it is sufficient that the irradiation of the laser beam can be controlled as a result. For example, the irradiation time or the irradiation power of the laser beam may be controlled using a shutter capable of modulating the degree of transmission of the light beam.

In the above embodiment, the recording layer 12
Although an organic dye such as cyanine is used, the present invention is not limited thereto, and an organic dye or an inorganic material other than the above may be used, or other materials may be appropriately used. . However, when the organic dye as described above is used, it is possible to reliably change the size of the recording mark in accordance with the irradiation time of five or more steps of the laser beam, and to perform recording with extremely high accuracy. The recording mark could be read.

Further, the size of the virtual recording cell 40 set on the recording layer 12 when the recording mark is formed by the optical recording device 30 is not limited to the embodiment. Here, the case where the single side width B of the virtual recording cell 40 is made substantially equal to the groove width W is shown.
As long as the beam waist diameter of the laser beam can be further reduced, the width may be smaller than the width W of the groove 16. The same applies to the unit length H. On the other hand, when recording marks are recorded in further multiple steps such as eight steps, the size of the virtual recording cell 40 may be set to be equal to or larger than the laser beam waist. In that case, some of the recording marks can be made larger than the beam waist.

The laser beam has a circular shape at the position of the recording layer 12. This is achieved by adding a beam shaping prism 42C or an aperture to the objective lens 42A, as shown in FIG. Thus, the beam shape may be an oval or 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.

Further, as shown by reference numeral 52 in FIG. 1, the optical recording medium 10 may have a plurality of pits having different reflectivities in advance corresponding to the number of signal modulation stages. Multi-level recording may be performed in advance on a part of the optical recording medium by the optical recording method of the present invention. The plurality of pits 52 and / or the recording mark 54 of the multi-level recorded portion include 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. Specific information such as information for determining the irradiation time of the laser beam for recording and reproduction, and information on the groove width W may be recorded. By reading the specific information at the time of reproduction and / or recording of the optical recording medium, it is possible to reliably identify that the optical recording medium is a multi-level recording optical recording medium, and to further individually identify them. More reliable multi-level recording / reproduction can be performed.

Normally, a CD-R / RW or a 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 head can be moved to the lead-in portion to read out signals.

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 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. 12, each of the grooves 104 is changed without changing the wobble amplitude Wb.
A, 104B, 104C wobble periods T _A , T _B , T _C
change. For example, the user area 1 shown in FIG.
The wobble period T _O of the groove 16 at 06 is a 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. Record it. 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. 13, the above-mentioned various information is put on land pre-pits 17A formed on the land 17 between the grooves 16. For example, when the period between the land pre-pits is short, binary recording is performed as "1", and when the period is long, "0" is recorded.

As still another example, as shown by reference numeral 56 (groove interruption portion) in FIG. 14 or FIG. If it is long, it indicates "0".

The information by the information recording means shown in FIGS. 11, 13 and 14 can be read by a conventional binary recording type reproducing apparatus.
Even if this multi-level optical recording medium is erroneously loaded into a binary recording type reproducing and / or recording apparatus, 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.

[0090]

According to the optical recording method and the optical recording apparatus of the present invention, multi-level recording can be achieved according to the data to be recorded, and the characteristics of the signal read from the recording mark can be improved. can do.

[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 block diagram showing a configuration of a servo mechanism included in the optical recording apparatus.

FIG. 4 is a block diagram showing a configuration of a laser driver included in the optical recording apparatus.

FIG. 5 is a schematic view 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. 6 is a diagram showing a generation process of a timing chart of laser beam irradiation when forming a recording mark on a recording layer by the optical recording apparatus.

FIG. 7 is a perspective view showing a state in which multi-level recording is performed on an optical recording medium without performing tilt control.

FIG. 8 is a cross-sectional view schematically showing a recording state when a recording mark is formed in a virtual recording cell without performing tilt control.

FIG. 9 is a cross-sectional view schematically showing a state in which a recording mark is read when tilt control is not performed.

FIG. 10 is a schematic perspective view showing a case where a laser beam for irradiating a virtual recording cell has another shape.

FIG. 11 is an enlarged schematic view showing a wobble in which various information is recorded in advance on the optical recording medium of the present invention.

FIG. 12 is a diagram showing a relationship between a wobble cycle of the wobble and a binary signal;

FIG. 13 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. 14 is a schematic diagram showing the relationship between the length of a groove interrupted by recording various information on the optical recording medium of the present invention and a binary signal.

FIG. 15 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 17 ... Land 17A ... Land pre-pit 18 ... Reflective film 20 ... Protective layer 30 ... Optical recording device 32 ... Spindle 36 ... Laser 38 ... Laser driver 40, 401 to 410 ... virtual recording cell 42 ... irradiation optical system 42A ... objective lens 42B ... half mirror 42C ... beam shaping prism 44 ... focus servo circuit 45 ... servo mechanism 46 ... feed servo mechanism 47A ... tilt servo mechanism 47B ... tilt Sensors 48A to 48G, 49, 54 Recording mark 52 Pit 56 Groove interruption part 60 Cell time setting part 62 Irradiation time setting part 64 Distribution processing part D Beam

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Takashi Doi 1-13-1, Nihonbashi, Chuo-ku, Tokyo TDK Corporation (72) Inventor Shiro Otsuki 1-1-13, Nihonbashi, Chuo-ku, Tokyo TDK F term in reference (reference) 5D090 AA01 BB05 CC01 CC16 EE02 FF12 GG03 HH01 KK04 KK05 LL08 5D119 AA22 AA23 BB02 BB04 DA01 EC09 EC25 HA48 HA61

Claims (6)

[Claims] An optical recording method for irradiating a recording layer of an optical recording medium with a laser beam focused by an irradiation optical system and forming a recording mark on the recording layer with the laser beam to record information. In the relative movement direction with respect to the laser beam in the recording layer,
A plurality of virtual recording cells having an arbitrary unit length in the moving direction and an arbitrary unit width in a direction orthogonal to the moving direction are continuously defined, and a change in an incident angle of the laser beam with respect to the recording layer is suppressed. At least one of the irradiation time or the irradiation power is controlled in five or more stages while irradiating a laser beam while controlling the angle of the irradiation optical system so that at least five types of the virtual recording cells differ in size. Optical recording, wherein a recording mark is formed, and information is multi-level recorded so that the light reflectance of the entire virtual recording cell can be modulated in five or more steps based on the occupancy of the recording mark with respect to the virtual recording cell. Method. 2. The optical recording method according to claim 1, wherein at least the irradiation optical system is angle-controlled so that an incident angle of the laser beam with respect to the recording layer falls within a predetermined range. 3. The angle control of at least the irradiation optical system when irradiating the laser beam to a partial area of the recording layer in which the plurality of virtual recording cells are set, according to claim 1 or 2. An optical recording method, comprising: 4. A laser for outputting a laser beam, an irradiation control device capable of controlling the laser, an irradiation optical system for condensing the laser beam, and at least positioning of the laser and the irradiation optical system for the recording. A servo mechanism for irradiating a predetermined position of the layer with the laser beam; and an optical recording apparatus capable of recording information by forming a recording mark on the recording layer by irradiating the laser beam. Is in the direction of relative movement with the laser beam in the recording layer,
A plurality of virtual recording cells having an arbitrary unit length in the movement direction and an arbitrary unit width in a direction orthogonal to the relative movement direction are continuously defined, and at least one of the irradiation time or the irradiation power is set to five or more steps. And the laser mechanism can irradiate the virtual recording cell with the laser beam, and the servo mechanism follows a tilt sensor capable of measuring a tilt amount of the virtual recording cell in the recording layer, and follows the tilt amount. A tilt mechanism for controlling at least the irradiation optical system to suppress a change in the incident angle of the laser beam to the recording layer, the size of the virtual recording cell being increased by the laser beam. And the light reflectance of the entire virtual recording cell is determined based on the occupation ratio of the recording mark to the virtual recording cell in five or more steps. The optical recording apparatus characterized by a multi-level can be recorded information as possible modulated. 5. The tilt mechanism according to claim 4, wherein the tilt mechanism of the servo mechanism tilts the irradiation optical system so that an incident angle of the laser beam on the recording layer falls within a predetermined range. Optical recording device. 6. The method according to claim 4, wherein the tilt mechanism in the servo mechanism irradiates a laser beam to a partial area of the recording layer in which the virtual recording cell is defined. An optical recording apparatus characterized in that an irradiation optical system is tilt-controlled.