JP2013020659A - Recording device and recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recording device capable of increasing the information recording density in a recording plane direction like mark edge recording and achieving a large recording capacity by increasing the number of recording planes in a depth direction.SOLUTION: The recording device includes a recording section that performs blank mark recording by selectively focusing a laser beam to points located at each different depth in the recording layer on a bulk type optical recording medium on which marks are recorded at plural points in a depth direction in a bulk-like recording layer. Also, the recording device includes a control section that controls the recording section to record blank marks at a first depth position and a second depth position in the recording layer so that the spaces among the marks in the depth direction and the plane direction allow reproduction with a multiplexed laser beam.

Description

  The present technology relates to a recording apparatus and a recording method for an optical recording medium in which a void (empty envelope) is formed as a recording mark.

JP 2008-135144 A JP 2008-176902 A

  As optical recording media on which signals are recorded / reproduced by light irradiation, so-called optical disks such as CD (Compact Disc), DVD (Digital Versatile Disc), and BD (Blu-ray Disc: registered trademark) are widely used. .

  Regarding the optical recording media that should be the next generation of optical recording media that are currently popular such as CDs, DVDs, and BDs, the present applicant has previously referred to the so-called Patent Document 1 and Patent Document 2 as described above. An optical recording medium of a bulk recording type (also simply called a bulk type) has been proposed.

  Here, the bulk recording is, for example, as shown in FIG. 16 in which laser light irradiation is performed by sequentially changing the focal position with respect to an optical recording medium having at least a bulk layer (recording layer) 100 (hereinafter referred to as a bulk type recording medium). This is a technique for increasing the recording capacity by performing multilayer recording in the bulk layer 100.

  Regarding such bulk recording, the above-mentioned Patent Document 1 discloses a recording technique called a so-called micro-hologram method. In the micro-hologram method, a so-called hologram recording material is used as a recording material for the bulk layer 100. As a hologram recording material, for example, a photopolymerization type photopolymer or the like is widely known.

The micro hologram method is roughly classified into a positive micro hologram method and a negative micro hologram method.
The positive micro-hologram method is a method in which two opposed light beams (light beam A and light beam B) are collected at the same position to form fine interference fringes (holograms), which are used as recording marks.
The negative type micro-hologram method is a method opposite to the positive type micro-hologram method, in which interference fringes formed in advance are erased by laser light irradiation, and the erased portion is used as a recording mark. In this negative microhologram method, a process of forming interference fringes in the bulk layer in advance is required as an initialization process.

The present applicant has also proposed a recording method for forming a void (void: void) as a recording mark as disclosed in Patent Document 2, for example, as a bulk recording method different from the micro-hologram method. ing.
In the void recording method, for example, the bulk layer 100 composed of a photopolymerization type photopolymer or a recording material mainly composed of a resin is irradiated with laser light at a relatively high power, and the bulk layer 100 is empty. It is a technique to record a package. As described in Patent Document 2, the vacant portion formed in this way becomes a portion having a refractive index different from that of the other portion in the bulk layer 100, and the light reflectance is increased at the boundary portion. become. Therefore, the empty packet portion functions as a recording mark, thereby realizing information recording by forming an empty packet mark.

Since such a void recording method does not form a hologram, it is only necessary to perform light irradiation from one side for recording. That is, there is no need to form the recording mark by condensing the two light beams at the same position as in the case of the positive microhologram method described above.
Further, in comparison with the negative type micro hologram method, there is an advantage that the initialization process can be made unnecessary.
Note that Patent Document 2 shows an example in which pre-curing light irradiation before recording is performed in performing void recording, but voids can be formed even if such pre-curing light irradiation is omitted.

By the way, among the bulk recording methods described above, the void recording method, in particular, is a so-called hole recording method in which an empty envelope is formed as a recording mark, and therefore, for example, a relatively high power of about 100 W peak power = 100 W. A recording beam is irradiated.
In such a void recording system, when a mark having a desired length is to be recorded, it is very difficult to control the edge position. That is, from this point, it is very difficult to adopt mark edge recording in the void recording method.

In the void recording method, the surface of the empty mark functions as a reflecting surface as described above. Therefore, if mark edge recording is performed, the amount of light reaching the back layer position tends to be greatly reduced. As a result, it is very difficult to increase the recording capacity by increasing the number of layer positions for recording.
Also in this respect, it is difficult to realize mark edge recording with the void recording method.

  Since it is difficult to employ mark edge recording in this way, the current void recording method employs mark position recording.

  However, mark position recording is disadvantageous in improving the information recording density (recording density in the recording surface direction) as compared with mark edge recording, and as a result, it is very difficult to increase the recording capacity. Become.

  The present technology has been made in view of such problems, and improves the information recording density (increases the recording capacity) in the in-recording surface direction such as mark edge recording, and records the recording surface (recording in the depth direction). It is an object to increase the recording capacity by increasing the number of layer positions).

In order to solve the above problems, the present technology is configured as a recording apparatus as follows.
That is, the recording apparatus according to the present technology selectively applies laser beams to different depth positions of the recording layer in a bulk type optical recording medium in which mark recording is performed at a plurality of positions in the depth direction of the bulk recording layer. A recording unit for collecting and recording marks by empty packaging is provided.
In addition, an empty mark is formed with respect to the first depth position and the second depth position in the recording layer so that the mark intervals in the depth direction and the in-plane direction can be combined and reproduced. Is provided with a control unit for controlling the recording unit.

According to the present technology, it is possible to record an empty mark at the first depth position and the second depth position so that the combined reproduction is possible.
By enabling the combined reproduction, a reproduction signal equivalent to the mark edge recording can be obtained even if the mark at the first depth position and the mark at the second depth position are recorded at the mark position. it can. As a result, the information recording density in the in-plane direction can be improved, and the in-plane recording capacity can be increased.
In addition, the combined reproduction is the amplitude of the valley of the combined reproduction signal of the set of the mark at the first depth position and the mark at the second depth position (the set of marks that form one mark portion). Since it is realized if the level is equal to or higher than a certain level, the distance in the in-plane direction between the mark at the first depth position and the mark at the second depth position can be kept to some extent.
Since the marks can be spaced in the in-plane direction in this way, the reflection loss when the laser beam travels in the depth direction is suppressed as compared with mark edge recording in which continuous marks are formed. The amount of light reaching the back side of the recording layer can be increased accordingly.
As a result, the number of recording surfaces can be increased to improve the recording density in the depth direction, and a large recording capacity can be achieved due to this point.

  As described above, according to the present technology, in the void recording method for recording the empty mark, the information recording density in the in-recording direction direction (mark edge recording) is improved (the recording capacity is increased) and the depth is increased. The recording capacity can be increased by increasing the number of recording surfaces (recording layer positions) in the direction.

1 is a cross-sectional structure diagram of an optical recording medium to be recorded and reproduced in an embodiment. It is a figure for demonstrating the position control method at the time of recording. It is a figure for demonstrating the position control method at the time of reproduction | regeneration. FIG. 2 is a diagram mainly illustrating a configuration of an optical system included in the recording apparatus according to the first embodiment. It is explanatory drawing about the structure of normal MOPA. 1 is a diagram illustrating an overall internal configuration of a recording apparatus according to a first embodiment. It is explanatory drawing about the method which can be considered appropriately as a combined reproduction | regeneration. It is the figure which contrasted and showed the method (FIG. 8A) shown in FIG. 7, and the method (FIG. 8B) of this Embodiment. It is a figure for demonstrating a specific mark recording method. It is the figure which showed the example of the combination of the mark which should be recorded in order to implement | achieve each mark length. It is the figure which showed the structural example of the conversion table. It is the flowchart which showed the procedure of the specific process which should be performed in order to implement | achieve the recording method of 1st Embodiment. It is the flowchart which showed the procedure of the specific process which should be performed in order to implement | achieve the reproduction | regeneration technique as embodiment. It is the figure mainly shown about the structure of the optical system with which the recording apparatus of 2nd Embodiment is provided. It is the figure which showed the whole internal structure of the recording device of 2nd Embodiment. It is a figure for demonstrating a bulk recording system.

Hereinafter, embodiments according to the present technology will be described.
The description will be given in the following order.

<1. Optical Recording Medium to be Recorded and Reproduced in Embodiment>
[1-1. Structure of optical recording medium]
[1-2. Position control method]
<2. Configuration of recording apparatus>
[2-1. Configuration of optical system]
[2-2. Overall internal configuration of recording apparatus]
<3. Recording method to enable combined playback>
[3-1. About combined playback]
[3-2. Specific examples of recording methods]
[3-3. About playback method]
[3-4. Processing procedure]
<4. Second Embodiment>
<5. Modification>

<1. Optical Recording Medium to be Recorded and Reproduced in Embodiment>
[1-1. Structure of optical recording medium]

FIG. 1 is a cross-sectional structure diagram of an optical recording medium (bulk type recording medium 1) to be recorded and reproduced in the embodiment.
The bulk type recording medium 1 is an optical recording medium (bulk type optical recording medium) on which so-called bulk recording is performed. Bulk recording does not take a multi-layer structure with a plurality of recording films formed like a normal multi-layer optical disc, but performs multi-layer recording by irradiating laser light by sequentially changing the focal position of the bulk recording layer. Refers to the technology to be performed.

In FIG. 1, a bulk type recording medium 1 is a disc-shaped optical recording medium, and laser recording is performed on the bulk type recording medium 1 that is rotationally driven to perform mark recording (information recording) on the bulk layer 3. . In addition, the reproduction of the recorded information is also performed by irradiating the bulk type recording medium 1 that is rotationally driven with laser light.
The optical recording medium is a general term for recording media on which information is recorded / reproduced by light irradiation.

As shown in the figure, on the bulk type recording medium 1, a cover layer 2, a bulk layer 3, an adhesive layer 4, a reflective film 5, and a substrate 6 are formed in order from the upper layer side.
Here, the “upper layer side” in this specification refers to the upper layer side when a surface on which a laser beam from a recording device (recording / reproducing device 10 or the like) described later is incident is an upper surface.

  In this specification, the term “depth direction” is used, and this “depth direction” is a direction that coincides with the vertical direction according to the definition of “upper layer side” (that is, from the recording apparatus side). The direction parallel to the incident direction of the laser beam: the focus direction).

  In the bulk type recording medium 1, the cover layer 2 is made of, for example, a resin and functions as a protective layer for the bulk layer 3 as a recording layer.

A bulk layer 3 is formed on the lower layer side of the cover layer 2.
Here, in the present embodiment, a void recording method is employed in which a void (void: void, hole) is formed as a recording mark. Therefore, as the material for forming the bulk layer 3 (recording material), a material corresponding to the void recording method is employed. In addition, as a specific recording material of the bulk layer 3, a material mainly composed of a resin can be exemplified.

A reflective film 5 is formed on the lower layer side of the bulk layer 3 via an adhesive layer (intermediate layer) 4 made of a required adhesive material.
A position guide for guiding the recording / reproducing position is formed on the reflective film 5. Here, the formation of the position guide on the reflection film means that the reflection film is formed on the interface where the position guide is formed.
Specifically, in this case, a groove or a pit row is formed on one surface side of the substrate 6 in the figure, thereby giving the uneven cross-sectional shape as shown in the figure, and the uneven cross-sectional shape of the substrate 6 The reflective film 5 is formed on the surface to which the position is given, so that the position guide by the groove or the pit row is formed on the reflective film 5.
Depending on the groove or the pit row, information (absolute position information: radial position information and rotation angle information) indicating an absolute position in a direction parallel to the recording surface direction of the bulk type recording medium 1 is recorded. This absolute position information is recorded by modulation of the meandering (wobble) period of the groove when the position guide is formed of a groove, and when the position guide is formed of a pit row, the pit length and formation interval are recorded. Recording is performed by modulation.

  The substrate 6 is made of a resin such as polycarbonate. The substrate 6 is generated by, for example, injection molding using a stamper provided with a concavo-convex cross-sectional shape as the position guide.

Here, the position guide or the reflection film on which the position guide is formed is not provided in the bulk layer 3, and the recording position on the bulk layer 3 is the reflection film 5 on which the position guide is formed as described later. It is controlled based on the reflected light from.
In this sense, the reflective film 5 (reflective surface) on which the position guide is formed is expressed as a reference surface Ref.

[1-2. Position control method]

By the way, when performing multi-layer recording on the bulk layer 3 on which no position guide or reflecting film is formed, the depth position where mark recording should be performed in the bulk layer 3, that is, the position of the recording surface, The position is determined in advance.
Hereinafter, the depth position is also referred to as a layer position.

  In the bulk layer 3 in this case, for example, as shown in FIG. 2, the first information recording layer position L1 to the fifth information recording layer position L5 are calculated as the layer positions where the mark recording is to be performed (also referred to as information recording layer positions). Assume that five information recording layer positions L are set.

Here, as will be described later, in the present embodiment, the first depth position and the second depth position that are close enough to cause crosstalk are set as one set, and a mark row for multiplexed reproduction is set as one set. Are recorded so that the recorded signals at the first depth position and the second depth position can be read as a unit during reproduction. That is, in the present embodiment, two depth positions (two layer positions) as the first and second depth positions are one set, and one recording layer as in a conventional multilayer optical disc is formed. It can be said that it constitutes.
Each information layer position L shown in FIG. 2 is a first depth position set and a second depth position set corresponding to one recording layer of a conventional multilayer optical disc. Only the depth position is shown, and the second depth position is not shown.

At this time, each information recording layer position L can be defined by an offset value of from the reference plane Ref, for example. Specifically, the first information recording layer position L1 can be defined as a position offset upward from the reference plane Ref by an amount corresponding to the first offset value of-L1. Similarly, the second information recording layer position L2, the third information recording layer position L3, the fourth information recording layer position L4, and the fifth information recording layer position L5 are respectively set to the second offset value of-L2 from the reference plane Ref. It is defined as a position separated by an amount corresponding to the 3 offset value of-L3, the fourth offset value of-L4, and the fifth offset value of-L5.
In this case, each offset value of-L is set in a controller 43 (controller 53) in the recording / reproducing apparatus 10 described later.

  In FIG. 2, for the sake of illustration, the information recording layer position L is assumed to be five, but in practice, for example, the information recording layer position L of about several tens (for example, 20) with an interval of about 10 μm is provided. Will be set.

Here, the bulk type recording medium 1 is irradiated with a laser beam (recording laser beam) for recording an empty mark corresponding to the time of recording on the recording layer 3 and is positioned on the reference surface Ref. Laser light (reference surface servo laser light) having a wavelength different from that of the recording laser light for performing position control based on the guide is also irradiated.
As shown in the figure, the recording laser light and the reference surface servo laser light are applied to the bulk type recording medium 1 through a common objective lens.

At the time of recording the mark, the reference surface servo laser light is irradiated so as to be focused on the reflection film 5 (reference surface Ref) as shown in the figure, and the reflected light of the reference surface servo laser light from the reflection film 5 is irradiated. Based on this, focus servo / tracking servo control of the objective lens is performed. In this state, the focus position of the recording laser beam is adjusted to coincide with a desired layer position in the bulk layer 3 and a mark is recorded at the desired layer position. At this time, the objective lens is driven so as to follow the position guide formed on the reference surface Ref by the tracking servo using the reference surface servo laser beam, so that the recording irradiated through the objective lens is performed. The position of the laser beam in the tracking direction is also controlled to be a position along the position guide.
As will be described later, the adjustment of the focus position of the recording laser beam is performed by the recording light focus mechanism (a set of the fixed lens 14, the movable lens 15, and the lens driving unit 16 in FIG. 4).

  In this example, it is assumed that the wavelength of the recording laser light is about 400 nm and the wavelength of the reference surface servo laser light is about 650 nm.

  Here, in the void recording method for recording an empty mark, it is necessary to irradiate a relatively high power recording laser beam. For this reason, a pulsed laser light source such as a MOPA (Master Oscillator Power Amplifier) 110 described later is used as a light source for recording.

  Such a pulse laser light source is very difficult to use as a light source for reproducing a recording signal and performing various servo controls. Therefore, in the recording apparatus of the present embodiment, a CW (Continuous Wave) laser light source for performing reproduction of recorded information and servo control at the time of reproduction is provided separately from the recording laser light source (see FIG. Servo / reproducing laser 22 in 4).

At the time of reproduction, as shown in FIG. 3, the bulk / layer 3 is irradiated with servo / reproduction laser light emitted from the CW laser light source through the objective lens.
Specifically, at the time of reproduction, the servo / reproducing laser beam with respect to the information recording layer position L to be reproduced is obtained by using the reflected light of the servo / reproducing laser beam from the already recorded mark row in the bulk layer 3. Perform focus servo and tracking servo. That is, the objective lens is controlled based on the reflected light of the servo / reproducing laser beam so that the focus servo and tracking servo are realized.
Further, the recording signal is also reproduced by the servo / reproducing laser beam.

For confirmation, the servo / reproducing laser beam is focused on the information recording layer position L to be reproduced in the bulk layer 3, that is, the reflective film 5 is focused. The servo / reproducing laser beam after irradiation is irradiated. Therefore, the reflected light from the reflection film 5 of the servo / reproducing laser beam has little influence on the reflected light (reproducing light) from the recording mark of the servo / reproducing laser beam.
When the influence of the reflected light from the reflection film 5 of the servo / reproducing laser light on the reproduction performance is taken into consideration, the reflective film 5 is the same as the reference surface servo laser light (for example, wavelength 650 nm). A wavelength selection film that selectively reflects only light in the wavelength band may be provided.

<2. Configuration of recording apparatus>
[2-1. Configuration of optical system]

FIG. 4 is a diagram for mainly explaining the configuration of the optical system provided in the recording apparatus as the embodiment.
The recording apparatus according to the embodiment has a reproducing function as well as a recording function for the bulk type recording medium 1. From this point, the recording apparatus according to the embodiment is hereinafter referred to as a recording / reproducing apparatus 10.
FIG. 4 mainly shows the internal configuration of the optical pickup OP1 provided in the recording / reproducing apparatus 10.

In FIG. 4, the bulk type recording medium 1 loaded in the recording / reproducing apparatus 10 is set so that the center hole is clamped at a predetermined position in the recording / reproducing apparatus 10, and is rotated by a spindle motor (not shown). Is kept in a possible state.
The optical pickup OP1 is provided to irradiate the bulk type recording medium 1 rotated by the spindle motor with a recording laser beam, a reference surface servo laser beam, and a servo / reproducing laser beam.

  Of the MOPA that is the light source of the recording laser light, only the SOA unit 9 (SOA: Semiconductor Optical Amp) is mounted in the optical pickup OP1.

Here, the configuration of the normal MOPA 110 will be described with reference to FIG.
As shown in the figure, a normal MOPA 110 includes a mode-locked laser unit (also referred to as an MLLD unit) 7, an isolator 8, and an SOA unit 9.

The MLLD unit 7 includes a laser unit 7A that is a semiconductor laser, and condenses a condensing lens 7B that condenses the laser light generated by the diverging light emitted from the laser unit 7A, and a laser beam incident through the condensing lens 7B A band-pass filter 7C, a resonance mirror 7D on which the laser light is incident via the band-pass filter 7C, and a collimator lens 7E that collimates the laser light partially transmitted through the resonance mirror 7D (diversified light) It has.
As shown, the condensing point by the condensing lens 7B coincides with the reflecting surface of the resonance mirror 7D.
The band pass filter 7C is configured to selectively transmit light in a predetermined wavelength range.

  In such an MLLD unit 7, an external resonator (spatial resonator) is formed between a mirror (not shown) on the rear end face of the laser unit 7A and a resonance mirror 7D. The repetition frequency (oscillation frequency) of the laser light emitted from the MLLD unit 7 is determined by the optical path length of the external resonator. Thereby, it can be locked to a specific frequency forcibly, and the mode of a laser beam can be locked.

  Laser light (pulse laser light) emitted from the MLLD unit 7 enters the isolator 8. In the isolator 8, the light reflected by the optical component or the like subsequent to the optical isolator 8 enters the MLLD unit 7, and the light emitted from the incident end of the SOA unit 9 is reflected by the optical component or the like preceding the optical isolator 9 And has a function of preventing the light from entering the SOA unit 9.

Laser light that passes through the isolator 8 enters the SOA unit 9.
As illustrated, the SOA unit 9 includes a condenser lens 9A and an SOA 9B. In the SOA unit 9, the laser light through the isolator 8 is condensed at the incident end of the SOA 9B by the condenser lens 9A. The SOA 9B is a semiconductor optical amplifier that amplifies and modulates incident laser light (pulse laser light emitted from the MLLD unit 7).

For such MOPA 110, a drive signal D-ml for driving the laser unit 7A of the MLLD unit 7 to emit light and a drive signal D-soa for controlling the modulation operation by the SOA 9B according to the recording signal are provided. Will be supplied.
The repetition frequency of the pulse laser beam output from the MLLD unit 7A is set sufficiently higher than the data frequency (for example, about 1 GHz).
For example, the SOA 9B turns on (amplifies and outputs) the output of the pulse laser beam when the drive signal D-soa is High, and turns off the output of the pulse laser beam when the drive signal D-soa is Low. Thereby, the laser emission according to the recording signal is realized.

Here, in the MOPA 110 as described above, the repetition frequency of the pulsed laser light is determined by the optical path length of the external resonator of the MLLD unit 7, and for example, when the repetition frequency of about 1 GHz as described above is required. The size of the MLLD unit 7 is relatively large.
For this reason, in this embodiment, in order to prevent the optical pickup OP1 from becoming large, the entire MOPA 110 is not mounted on the optical pickup OP1, but only the SOA unit 9 is mounted.

As will be described later with reference to FIG. 6, the MLLD unit 7 and the isolator 8 are arranged outside the optical pickup OP1.
In this case, the output light from the isolator 8 is transmitted to the SOA unit 9 in the optical pickup OP1 through the optical fiber 11.

In FIG. 4, the recording laser light emitted from the SOA unit 9 is made parallel light through the collimation lens 12 and then enters the beam splitter 13. A part of the recording laser light incident on the beam splitter 13 passes through the beam splitter and enters an expander including the fixed lens 14, the movable lens 15, and the lens driving unit 16. This expander corresponds to the recording light focus mechanism described above.
In the recording light focus mechanism, as shown in the figure, a fixed lens 14 is disposed on the side close to the SOA unit 9 as a light source, and a movable lens 15 is disposed on the side far from the SOA unit 9. 15 is configured to be driven in a direction parallel to the optical axis of the recording laser beam. The recording light focus mechanism enables independent focus control for the recording laser light.
As will be described later, the lens driving unit 16 is driven by the controller 43 shown in FIG. 6 according to the offset value of-L set corresponding to the target information recording layer position L.

The recording laser light that passes through the fixed lens 14 and the movable lens 15 forming the recording light focus mechanism is reflected by the mirror 17 as shown in the figure, and then the dichroic prism 19 via the quarter wavelength plate 18. Is incident on.
The dichroic prism 19 is configured such that its selective reflection surface reflects light in the same wavelength band as that of the recording laser light and transmits light having other wavelengths. Accordingly, the recording laser light incident as described above is reflected by the dichroic prism 19.

The recording laser beam reflected by the dichroic prism 19 is applied to the bulk type recording medium 1 through the objective lens 20 as shown in the figure.
With respect to the objective lens 20, the objective lens 20 is focused in the focus direction (the direction in which the objective lens 20 is moved toward and away from the bulk type recording medium 1) and the tracking direction (the direction perpendicular to the focus direction: the radial direction of the bulk type recording medium 1). ) Is provided with a biaxial actuator 21 that is held displaceably.
The biaxial actuator 21 is provided with a focus coil and a tracking coil, and is supplied with drive signals (drive signals FD and TD, which will be described later), thereby displacing the objective lens 20 in the focus direction and the tracking direction, respectively.

Further, a servo / reproducing laser 22 which is a light source of servo / reproducing laser light is provided in the optical pickup OP1.
The servo / reproducing laser 22 is configured to emit laser light having the same wavelength as the recording laser light as servo / reproducing laser light.

  The servo / reproducing laser beam emitted from the servo / reproducing laser 22 is converted into parallel light through the collimation lens 23 and then enters the polarization beam splitter 24. The polarization beam splitter 24 is configured to reflect the servo / reproducing laser beam incident from the servo / reproducing laser 22 side in this way.

The servo / playback laser beam reflected by the polarization beam splitter 24 is incident on the beam splitter 13, a part of which is reflected and guided to the recording light focusing mechanism described above.
The servo / playback laser light via the recording light focus mechanism (fixed lens 14 → movable lens 15) is reflected by the mirror 17 as shown in the figure, and then dichroic prism 19 via the quarter-wave plate 18. Is incident on.
As described above, since the servo / reproducing laser beam has the same wavelength as the recording laser beam, the servo / reproducing laser beam is reflected by the dichroic prism 19 and passes through the objective lens 20 to the bulk type recording medium 1. It is irradiated to.

In this way, when the bulk type recording medium 1 is irradiated with the servo / reproducing laser beam, the reflected light (return light) from the bulk type recording medium 1 (recorded mark row in the bulk layer 3). ) Is obtained. The reflected light of the servo / reproducing laser beam thus obtained is guided to the dichroic prism 19 through the objective lens 20 and reflected by the dichroic prism 19.
The reflected light of the servo / reproducing laser beam reflected by the dichroic prism 19 passes through the quarter-wave plate 18 → mirror 17 → recording light focusing mechanism (movable lens 15 → fixed lens 14), and then the beam splitter 13. A part of the light is reflected and enters the polarization beam splitter 24.

  Here, the reflected light (return light) of the servo / reproducing laser light incident on the polarization beam splitter 24 in this way is due to the action by the quarter wavelength plate 18 and the action at the time of reflection on the bulk type recording medium 1. The direction of polarization of the forward light incident on the polarization beam splitter 24 from the servo / reproducing laser 22 side is made 90 degrees different. As a result, the reflected light of the servo / reproducing laser beam incident as described above is transmitted through the polarization beam splitter 24.

  The reflected light of the servo / reproducing laser beam that has passed through the polarization beam splitter 24 is condensed on the light receiving surface of the servo / reproducing light receiving unit 26 via the condenser lens 25. The received light signal obtained by the servo / reproducing light receiving unit 26 receiving the reflected light of the servo / reproducing laser beam is expressed as a received light signal DT-sp as shown in the figure.

  An optical system for the reference surface servo laser light is also provided in the optical pickup OP. Specifically, a reference surface servo laser 27, a collimation lens 28, a polarization beam splitter 29, a ¼ wavelength plate 30, a condensing lens 31, and a reference surface light receiving unit 32.

  The reference surface servo laser light emitted from the reference surface servo laser 27 is converted into parallel light via the collimation lens 28 and then enters the polarization beam splitter 29. The polarization beam splitter 29 is configured to transmit the reference surface servo laser light (forward light) incident from the reference surface servo laser 27 side in this way.

The reference surface servo laser light transmitted through the polarization beam splitter 29 is incident on the dichroic prism 19 via the quarter-wave plate 30.
As described above, the dichroic prism 19 is configured to reflect light in the same wavelength band as that of the recording laser beam and transmit light of other wavelengths, so that the reference surface servo laser beam is dichroic. The light passes through the prism 19 and is irradiated onto the bulk type recording medium 1 through the objective lens 20.

The reflected light (reflected light from the reference surface Ref) of the reference surface servo laser light obtained when the bulk type recording medium 1 is irradiated with the servo laser light as described above is transmitted to the objective lens 20. Then, the light passes through the dichroic prism 19 and enters the polarization beam splitter 29 via the quarter-wave plate 30.
As in the case of the previous servo / reproducing laser beam, the reflected light (return light) of the reference surface servo laser beam incident from the bulk type recording medium 1 side in this way is the function of the quarter wavelength plate 30. Due to the action at the time of reflection on the bulk type recording medium 1, the polarization direction of the forward path light is 90 degrees different from that of the forward path light. Therefore, the reflected light of the reference surface servo laser light as the backward path light is reflected by the polarization beam splitter 29. Reflected.

  The reflected light of the reference surface servo laser light reflected by the polarization beam splitter 29 is condensed on the light receiving surface of the reference surface light receiving unit 32 via the condenser lens 31. The light reception signal obtained by the reference surface light receiving unit 32 receiving the reflected light of the reference surface servo laser light is expressed as a light reception signal DT-ref as shown in the figure.

Although not shown in the drawings, the recording / reproducing apparatus 10 is actually provided with a slide drive unit that slides the entire optical pickup OP1 described above in the tracking direction, and the optical pickup OP1 is driven by the slide drive unit. By driving, the irradiation position of the laser beam can be displaced over a wide range.
The slide drive unit is controlled by a servo circuit 39 (during reproduction) and a reference surface servo circuit 42 (during recording) which will be described later.

[2-2. Overall internal configuration of recording apparatus]

FIG. 6 shows the overall internal configuration of the recording / reproducing apparatus 10.
In FIG. 6, with respect to the internal configuration of the optical pickup OP1, only the SOA unit 9, the lens driving unit 16, the biaxial actuator 21, and the servo / reproducing laser 22 are extracted from the configuration shown in FIG. Show.

  First, in the recording / reproducing apparatus 10, outside of the optical pickup OP1, focus / tracking control (that is, reflection of servo / reproducing laser light) of the objective lens 20 during recording of the bulk layer 3 or reproduction of a recording mark is performed. As a configuration for performing position control based on light), an MLLD unit 7, an isolator 8, a recording processing unit 35, a conversion table 35A, a laser driving unit 36, a servo / reproducing matrix circuit 37, a reproduction processing unit 38, And a servo circuit 39 is provided.

The laser drive unit 36 gives a drive signal D-ml to the MLLD unit 7 based on an instruction from the controller 43 described later, and causes the MLLD unit 7 (laser unit 7A) to emit light.
In this case, the pulsed laser light emitted from the MLLD unit 7 enters the SOA unit 9 via the isolator 8 → the optical fiber 11.
Further, the laser drive unit 36 drives the servo / reproducing laser 22 to emit light in response to an instruction from the controller 43 by a drive signal D-sp.

  Data to be recorded on the bulk type recording medium 1 (recording data) is input to the recording processing unit 35. The recording processing unit 35 adds an error correction code to the input recording data or performs predetermined recording modulation encoding, for example, “0” “1” actually recorded on the bulk type recording medium 1. A recording modulation data string which is a binary data string is obtained. Here, the recording modulation data string is a “code length signal” that represents information by a code length.

  Note that the recording processing unit 35 of the present embodiment, based on the content of the conversion table 35A, from the recording modulation data sequence (code length signal), the first signal and the first signal to be recorded for realizing the combined reproduction. A recording signal as two signals is generated. This point will be described later.

  The recording processing unit 35 controls the amplification modulation operation of the SOA 9B in the SOA unit 9 by the drive signal D-soa based on the recording signal generated from the recording modulation data string.

The servo / reproducing matrix circuit 37 corresponds to the light reception signals DT-sp (output current) from the plurality of light receiving elements as the servo / reproducing light receiving section 26 shown in FIG. An amplifier circuit is provided, and necessary signals are generated by matrix calculation processing.
Specifically, a high frequency signal (hereinafter referred to as a reproduction signal RF) corresponding to a reproduction signal of the signal recorded in the bulk layer 3, a focus error signal FE-sp for focus servo control, and a tracking servo control. A tracking error signal TE-sp is generated.

The reproduction signal RF generated by the servo / reproduction matrix circuit 37 is supplied to the reproduction processing unit 38.
The focus error signal FE-sp and the tracking error signal TE-sp are supplied to the servo circuit 39.

  The reproduction processing unit 38 performs reproduction processing for restoring the recording data, such as decoding of the recording modulation code and error correction processing, on the reproduction signal RF, and obtains reproduction data obtained by reproducing the recording data.

The servo circuit 39 generates a focus servo signal and a tracking servo signal from the focus error signal FE-sp and the tracking error signal TE-sp supplied from the servo / playback matrix circuit 37, respectively. Based on the servo signal, a focus drive signal FD-sp and a tracking drive signal TD-sp for driving the focus coil and tracking coil of the biaxial actuator 21 are generated.
As shown in the figure, the focus drive signal FD-sp is supplied to the switch SW1, and the tracking drive signal TD-sp is supplied to the switch SW2.
When the switch SW1 and the switch SW2 select the focus drive signal FD-sp and the tracking drive signal TD-sp, respectively, the focus coil and the tracking coil of the biaxial actuator 21 are set to the focus drive signal FD-sp and the tracking drive signal TD-. Driven based on sp. Thereby, focus servo control and tracking servo control for the servo / reproducing laser beam are realized.
As can be understood from the above description, the servo control of the biaxial actuator 21 (objective lens 20) based on the reflected light of the servo / playback laser beam is performed corresponding to the playback. is there.

  The servo circuit 39 realizes a track jump operation by turning off the tracking servo loop and giving a jump pulse to the tracking coil in response to an instruction given from the controller 43 in response to reproduction, Pull-in control is also performed. In addition, focus servo pull-in control during reproduction and addition of a focus bias according to an instruction from the controller 43 are also performed.

  In the recording / reproducing apparatus 10, a reference surface matrix circuit 40, a position information detection unit 41, and a reference surface servo circuit 42 are provided as a signal processing system for the reflected light of the reference surface servo laser light.

The reference surface matrix circuit 40 corresponds to a light reception signal DT-sv (output current) from a plurality of light receiving elements in the reference surface servo light receiving unit 32 shown in FIG. A circuit or the like is provided, and necessary signals are generated by matrix calculation processing.
Specifically, the reference surface matrix circuit 40 generates a focus error signal FE-sv for focus servo control and a tracking error signal TE-sv for tracking servo control.
Further, a position information detection signal Dps for detecting the absolute position information recorded on the reference surface Ref is generated. For example, when absolute position information is recorded by a pit string, a sum signal is generated as the position information detection signal Dps. Alternatively, when the absolute position information is recorded by the wobbling groove, a push-pull signal is generated as the position information detection signal Dps.

  The position information detection signal Dps is supplied to the position information detection unit 41. The position information detection unit 41 detects the absolute position information recorded on the reference surface Ref based on the position information detection signal Dps. The detected absolute position information is supplied to the controller 43.

The focus surface servo circuit 42 is supplied with the focus error signal FE-sv and the tracking error signal TE-sv generated by the reference surface matrix circuit 40.
The reference surface servo circuit 42 generates a focus servo signal and a tracking servo signal from the focus error signal FE-sv and the tracking error signal TE-sv, respectively, and the biaxial actuator 21 is based on the focus servo signal and the tracking servo signal. The focus drive signal TD-sp and the tracking drive signal TD-sv for driving the focus coil and the tracking coil are generated.
The focus drive signal FD-sv is supplied to the switch SW1, and the tracking drive signal TD-sv is supplied to the switch SW2. When the switch SW1 and the switch SW2 select the focus drive signal FD-sv and the tracking drive signal TD-sv, respectively, the focus coil and the tracking coil of the biaxial actuator 21 cause the focus drive signal FD-sv and the tracking drive signal TD- Driven based on sv, thereby realizing a reference surface servo.
As can be understood from the above description, such a reference surface servo is performed at the time of recording.

  The reference surface servo circuit 42 turns off the tracking servo loop in response to an instruction given from the controller 43 in response to recording (including seek for recording), and the tracking coil of the biaxial actuator 21. A track jump operation is realized by applying a jump pulse to the head, focus servo pull-in control with respect to the reference surface Ref, and the like are also performed.

The controller 43 is configured by a microcomputer including a memory (storage device) such as a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory), for example, a program stored in the ROM or the like, for example. The overall control of the recording / reproducing apparatus 10 is performed by executing the processing according to the above.
For example, the controller 43 controls (sets) the focus position of the recording laser beam based on the offset value of-L set in advance corresponding to each information recording layer position L as described above. Specifically, by driving the lens driving unit 16 in the optical pickup OP1 based on the offset value of-L set corresponding to the information recording layer position L to be recorded, in the depth direction Select the recording position.

The controller 43 also performs control for realizing the servo control switching of the objective lens 20 at the time of recording / reproducing as described above. Specifically, at the time of recording, the controller 43 instructs the reference surface servo circuit 42 to output the focus drive signal FD-sv and the tracking drive signal TD-sv, and the focus drive signal FD to the switch SW1 and the switch SW2, respectively. -sp, instructing the selection of the tracking drive signal TD-sp.
Further, at the time of recording, the controller 43 gives an instruction to the laser driving unit 36 to cause the MLLD unit 7 to emit light, and also instructs the recording processing unit 35 to execute mark recording based on the recording data.

On the other hand, during reproduction, the servo circuit 39 is instructed to output the focus drive signal FD-sp and tracking drive signal TD-sp, and the focus drive signal FD-sp and tracking drive signal TD- are supplied to the switches SW1 and SW2, respectively. Instructs selection of sp.
At the time of reproduction, an instruction is given to the laser drive unit 36 to drive the servo / reproduction laser 22 to emit light.

The controller 43 also performs seek operation control on the reference surface servo circuit 42. That is, the reference surface servo circuit 42 is instructed to move the spot position of the reference surface servo laser light to a predetermined target address on the reference surface Ref.

<3. Recording method to enable combined playback>
[3-1. About combined playback]

Here, as described above, in the void recording method for recording the empty mark, it is very difficult to control the edge position when attempting to form a mark having a predetermined length, and it is difficult to employ mark edge recording. Is done.
In addition, in the void recording method, since the surface of the empty mark functions as a reflecting surface, if mark edge recording is performed, the amount of light reaching the back layer position tends to be greatly reduced, resulting in a result. Therefore, it becomes difficult to increase the recording capacity by increasing the number of layer positions for recording.
Also in this respect, it is difficult to realize mark edge recording with the void recording method.

  Because of these difficulties, mark position recording is adopted in the current void recording method.

  However, mark position recording is disadvantageous in improving the information recording density (recording density in the recording surface direction) as compared with mark edge recording, and as a result, it is very difficult to increase the recording capacity. Become.

  Therefore, in the present embodiment, the information recording density in the recording surface direction such as mark edge recording is improved (increased recording capacity), and the recording capacity is increased by increasing the number of recording layer positions in the depth direction. The challenge is to make it possible to make it easier.

Here, in order to solve the problem, it is conceivable to employ a method of multiplexing reproduction.
FIG. 7 is an explanatory diagram of a method that can be properly considered as the combined reproduction.
FIG. 7A illustrates a mark train recorded for combined reproduction, and FIG. 7B illustrates a reproduction signal for the mark train of FIG. 7A.

  When performing the combined reproduction, as shown in FIG. 7A, the edge interval of each mark is within the distance that can be combined and reproduced (hereinafter referred to as the combined reproduction possible distance Dar) with respect to the same layer position Ln. As described above, it is considered that the mark recording is properly performed.

FIG. 7B shows a reproduction signal waveform (a thin solid line and a thin broken line) of each recording mark shown in FIG. 7A and a combined component (thick solid line) thereof. For confirmation, when the reproduction is performed with respect to the layer position Ln, the reproduction signal actually obtained is the combined component.
Thus, by forming the recording marks at the edge interval within the combined reproduction possible distance Dar, it is possible to obtain a reproduction signal representing a mark length longer than each recording mark alone as the reproduction signal. That is, even if each mark is recorded at the mark position, a signal as if the mark edge recording is performed can be obtained as the reproduction signal.

  In order to say combined reproduction, it is necessary that the level of the valley portion (X in the figure) of the reproduction signal component of each mark in the adjacent relationship does not drop to at least the GND level (for example, 0 level).

  However, in practice, when the method of forming each mark at the same layer position Ln as shown in FIG. 7 is used, when the mark is recorded within the combined reproduction possible distance Dar, the adjacent marks are not connected to each other. It has been found that it is difficult to achieve stable recording because there is a case of fusion (sticking).

Therefore, in the present embodiment, a method is proposed in which marks to be combined and reproduced are recorded separately at a first depth position and a second depth position.
FIG. 8 shows a comparison of the method (FIG. 8A) that can be considered as described in FIG. 7 and the method of this embodiment (FIG. 8B).
The first depth position is a position that coincides with any one of the first information recording layer position L1 to the fifth information recording layer position L5. For this reason, in the following description, the first depth position is also referred to as “first depth position Ln”.

  As shown in FIG. 8B, in the present embodiment, the marks to be multiplexed and reproduced are divided into the first layer position Ln and the second layer position Ln ′ located on the lower layer side than the first layer position Ln. To record.

  As can be seen by comparing FIG. 8B and FIG. 8A, according to the method of the present embodiment, the combined reproduction possible distance Dar in the recording in-plane direction is maintained and the marks to be combined and reproduced. The distance (thick line in the figure) can be longer than the method described in FIG. That is, the occurrence of fusion between adjacent marks can be suppressed accordingly, and stable recording can be realized.

FIG. 9 is a diagram for explaining a specific mark recording method.
In FIG. 9, first, as described above, the first depth position Ln coincides with the information recording layer position Ln to be recorded. Accordingly, the first depth position Ln is a depth position offset from the reference plane Ref by an amount corresponding to the nth offset value of-Ln (in this example, n is 1 to 5) as shown in the figure. Can be defined.
Further, the second depth position Ln ′ is a position offset from the first depth position Ln to the lower layer side (back side) by the distance Dd. This can be defined as a depth position that is offset from the reference plane Ref by an amount corresponding to the value of “nth offset value of_Ln−Dd” with reference plane Ref as a reference.

Here, when realizing the combined reproduction, not only the combined reproduction possible distance Dar in the recording in-plane direction but also the distance Dd in the depth direction between the marks (the distance between the mark center positions) should be considered. . In other words, the distance Dd should be set to a distance that allows combined reproduction.
Specifically, the distance Dd may be, for example, not more than three times the focal depth of the objective lens 20. As an example, in this example, the distance Dd is about 200 nm under the condition that the numerical aperture NA of the objective lens 20 is about 0.85 and the wavelength of the servo / playback laser beam (and the recording laser beam) is about 400 nm. Is supposed to be set.

Further, as the combined reproduction possible distance Dar in the in-plane direction, specifically, when the numerical aperture of the objective lens 20 is NA and the wavelength of the servo / reproducing laser beam is λ as described above,

λ / (2NA) ≦ Dar ≦ λ / NA

What is necessary is just to set so that it may satisfy | fill.

  The mark size formed on the second depth position Ln ′ side is larger than the mark size on the first depth position Ln side. This is because focus servo is applied to the first depth position Ln side during reproduction.

Here, as a matter common to the first depth position Ln and the second depth position Ln ′, it is assumed that the size of each mark formed is equal to or less than the spot size of the servo / reproducing laser beam. And

[3-2. Specific examples of recording methods]

FIG. 10 is a diagram showing an example of a combination of marks to be recorded in order to realize each mark length.
This figure shows an example of mark combinations for each mark of 2T to 8T. Specifically, 2T = 0.15 μm, 3T = 0.23 μm, 4T = 0.30 μm, 5T = 0.38 μm, It is assumed that 6T = 0.45 μm, 7T = 0.53 μm, and 8T = 0.60 μm.

First, in this example, 2T to 4T marks are expressed by the difference in size of one mark formed on the first depth position Ln side.
Specifically, a mark having a size of 2T is assigned to 2T, a mark having a size of 3T is assigned to 3T, and a mark having a size of 4T is assigned to 4T.

Here, the size of the mark is adjusted by the irradiation time and power of the recording laser beam. In FIG. 10, the recording pulse output position (output start time and output period length with reference to the code change point in the code length signal as the original signal (for example, the change point from “0” to “1”). Sa) is represented by a thick solid line.
With regard to 2T to 4T, the information on the recording pulse output position and the recording power may be set so that the reproduction signal waveforms of 2T, 3T, and 4T can be obtained when the reproduction is actually performed.

At this time, as the mark size increases (that is, the recording power increases), the front edge position of the mark protrudes further to the front side. That is, when the recording power is increased, the distance from the recording pulse output start time to the mark front edge position is increased.
Therefore, with respect to 2T to 4T, the recording pulse output start point is gradually shifted to the rear side every time the mark size increases from 2T to 4T.
Thereby, each mark can appropriately represent the mark length with reference to the sign change point.

On the other hand, in this example, the combined reproduction of the mark at the first depth position Ln and the mark at the second depth position Ln ′ is applied to a mark of 5T or more.
Specifically, for the 5T mark, as shown in the figure, one mark having a size of about 2T mark is provided at the first depth position Ln, and a mark having a size of about 3T mark is provided at the second depth position Ln ′. One is assigned.
As for the 6T mark, as shown in the figure, one mark having a size of about 2T mark is provided at the first depth position Ln, and one mark having a size of about 4T mark is provided at the second depth position Ln ′. It is supposed to be assigned.
As for the 7T mark, two marks having a size of about 2T mark are provided at the first depth position Ln, and a mark having a size of about 3T mark is provided at the second depth position Ln ′ in the recording surface direction. One is assigned so as to be arranged between the marks at the first depth position Ln.
As for the 8T mark, two marks having a size of about 2T mark are provided at the first depth position Ln, and a mark having a size of about 4T mark is provided at the second depth position Ln ′ in the recording surface direction. One is assigned so as to be arranged between the marks at the first depth position Ln.

Here, when an arbitrary mark length is expressed by a plurality of marks in this way, the mark located at the head in the recording in-plane direction determines the front edge position in the combined reproduction signal, and conversely at the rearmost. The mark located at 1 determines the rear edge position in the combined reproduction signal.
At this time, when a mark is arranged at an intermediate position such as 7T and 8T, the mark at the intermediate position has little contribution to both edges and functions mainly for level adjustment.

As described above, in order to realize the combined reproduction, the edge interval between the marks adjacent to each other in the recording surface direction should be set within the combined reproduction possible distance Dar.
Accordingly, for the 5T to 8T marks, a waveform expressing the corresponding mark length can be obtained as a waveform when combined reproduction is performed while satisfying such a condition that the combined reproduction possible distance Dar is within. The size of the mark at the first depth position Ln and its position, and the size of the mark at the second depth position Ln ′ and its position are determined.
Here, as understood from the above description, the size of the mark formed at each depth position and its position are determined by the recording pulse output position (output start time and output period) and the recording power. is there.

  In the present embodiment, the first signal to be recorded at the first depth position Ln and the second signal to be recorded at the second depth position Ln ′ from the original signal as the code length signal (mark edge recording signal). Two signals are generated. That is, the original mark edge recording signal is converted into a first signal and a second signal for combined reproduction.

FIG. 11 shows an example of the structure of a conversion table 35A used when converting a code length signal as a mark edge recording signal into a first signal and a second signal for enabling combined reproduction.
In FIG. 11, “front edge position”, “rear edge position”, and “power” represent the front edge position, rear edge position, and pulse height of the recording pulse, respectively. As can be understood from the description of FIG. 10, the front edge position and the rear edge position of the recording pulse represent positions based on the code change point in the code length signal.
The first pulse represents the first pulse, and the second pulse represents the second pulse.

As shown in FIG. 11, the conversion table 35A associates the generation parameters of the first signal and the generation parameters of the second signal for each mark length (2T to 8T) in the code length signal as the conversion source. Information.
Specifically, the first signal generation parameters are the front edge position, rear edge position, and power for the first pulse, and the front edge position, rear edge position, and power for the second pulse.
The generation parameters of the second signal are the front edge position, rear edge position, and power for the first pulse.
As shown in FIG. 10, since 2T to 4T in the present example are composed of only the first pulse of the first signal, the generation parameters for the second pulse of the first signal and the second signal of 2T to 4T The generation parameter is “none”.
Since 5T and 6T are composed of only the first pulse of the first signal and the first pulse of the second signal, the second pulse of the first signal for these 5T and 6T as shown in the figure. The generation parameter is “none”.

  Here, the recording processing unit 35 shown in FIG. 6 converts the code length signal generated from the recording data into the first signal and the second signal based on the conversion table 35A having the data structure as described above. To do.

  In the first embodiment, the first signal and the second signal obtained in the recording processing unit 35 in this way are recorded at respective depth positions by so-called double writing. That is, either one of the recording of the first signal for the first depth position Ln and the recording of the second signal for the second depth position Ln ′ is performed in advance, and then the other recording is performed. It is something to execute.

  The first depth position Ln so that a reproduction signal equivalent to the original code length signal (mark edge recording signal) is combined and reproduced by the recording method as the first embodiment as described above. And the second depth position Ln ′ can be recorded. Specifically, although the recording at each depth position is the mark position recording, the reproduction signal equivalent to the mark edge recording can be obtained by the combined reproduction.

  Since it is possible to obtain a reproduction signal equivalent to that obtained when mark edge recording is performed, it is possible to improve the information recording density in the recording in-plane direction, and to increase the in-plane recording capacity.

As can be understood from the description of FIG. 7 and the like, the combined reproduction is performed by combining a mark at the first depth position Ln and a mark at the second depth position Ln ′ (that is, one mark portion). The mark at the first depth position Ln and the second depth position Ln are realized as long as the amplitude level of the valley portion X of the combined reproduction signal of the combined reproduction signal of the set of marks that form the The distance in the in-plane direction from the 'mark can be set to some extent. Since the marks can be spaced in the in-plane direction in this way, the reflection loss when the laser beam travels in the depth direction is suppressed as compared with mark edge recording in which continuous marks are formed. The amount of light reaching the back side of the recording layer can be increased accordingly.
As a result, the number of recording surfaces can be increased to improve the recording density in the depth direction, and a large recording capacity can be achieved due to this point.

As described above, according to the recording method of the present embodiment, in the void recording method for recording the empty mark, the information recording density in the in-recording direction direction (mark recording capacity increase) such as mark edge recording is achieved. In addition, the recording capacity can be increased by increasing the number of recording surfaces (recording layer positions) in the depth direction.

[3-3. About playback method]

Here, in the case of the present embodiment, the combined reproduction of the first signal recorded at the first depth position Ln and the second signal recorded at the second depth position Ln ′ is the first reproduction. It is assumed that the focus servo is applied to the depth position Ln side.
Specifically, when combined reproduction is performed, a focus search is performed using servo / reproducing laser light, and the focus servo is pulled into the first depth position Ln as the information recording layer position Ln to be reproduced. Do.

At this time, the amplitude of the combined reproduction signal (reproduction signal RF) may be adjusted by adjusting the focus bias.
As a specific amplitude adjustment method, for example, a method of keeping the amplitude level of the valley portion X within an appropriate range can be used.

[3-4. Processing procedure]

FIG. 12 is a flowchart showing a specific processing procedure to be executed in order to realize the recording method according to the first embodiment.
The process shown in FIG. 12 is executed based on a program stored in a ROM or the like provided in the controller 43 shown in FIG.

  First, in step S101, the process waits until the recording of the nth information recording layer position Ln is started. That is, in the case of this example, the process waits until the recording to the information recording layer position L among the first information recording layer position L1 to the fifth information recording layer position L5 is to be started.

In response to the fact that the recording to the nth information recording layer position Ln is to be started, a process for seeking to the recording start address is performed in step S102. That is, the recording start address is instructed to the reference surface servo circuit 42, and the seek operation to the address is executed.
By this seek operation, the focus servo control / tracking servo control of the objective lens 20 for the reference surface Ref is performed.

  After the seek process in step S102, a process for setting the offset value of_Ln is executed in step S103. That is, the lens driving unit 16 is driven based on the nth offset value of_Ln set corresponding to the nth information recording layer position Ln to be recorded, and the focus position of the recording laser beam is determined as the nth information. The recording layer position Ln is matched with the first depth position Ln.

  After the setting process in step S103, a first signal recording start instruction is issued in step S104. That is, the laser drive unit 36 shown in FIG. 6 is instructed to emit light from the MLLD unit 7, and the recording processing unit 35 is instructed to generate the first signal and output the drive signal D-soa based on the first signal. Thus, the recording of the first signal at the first depth position Ln is started.

In the subsequent step S105, the process waits until the recording of the first signal is completed.
When the recording of the first signal is completed, a process for seeking to the recording start address is executed in step S106.

  After the seek process in step S106, a process for setting the offset of_Ln-Dd is performed in step S107. That is, by driving the lens driving unit 16 based on the value by the “offset of_Ln−Dd”, the focusing position of the recording laser beam is made to coincide with the second depth position Ln ′.

  After the setting process in step S107, a second signal recording start instruction is issued in step S108. That is, by instructing the laser drive unit 36 to emit light from the MLLD unit 7 and instructing the recording processing unit 35 to generate the second signal and output the drive signal D-soa based on the second signal, The recording of the second signal at the position Ln is started.

  In the subsequent step S109, the process waits until the recording of the second signal is completed. Then, when the recording of the second signal is finished, the processing shown in this figure is finished.

FIG. 13 is a flowchart showing a specific processing procedure to be executed for realizing the reproduction method according to the embodiment.
The processing shown in FIG. 13 is also executed based on a program stored in a ROM or the like provided in the controller 43 shown in FIG.

In FIG. 13, in step S201, the process waits until the reproduction of the nth information recording layer position Ln is to be started.
When the reproduction of the nth information recording layer position Ln is to be started, a process for turning on the focus at the nth information recording layer position Ln is executed in step S202. That is, the laser drive unit 36 is instructed to cause the servo / reproducing laser 22 to emit light, and the servo circuit 39 is instructed to perform a focus search for the nth information recording layer position Ln. Thus, the servo / reproducing laser beam is focused on the nth information recording layer position Ln.

After executing the focus ON process in step S202, the FB adjustment process is executed in step S203.
In this example, the FB adjustment process is a process of adjusting the focus bias so that the amplitude level of the valley X of the reproduction signal RF is within a predetermined range. The focus bias is set for the servo circuit 39.

After the execution of the FB adjustment process in step S203, a process for starting reproduction is executed in step S204. That is, the servo circuit 38 is instructed to start playback from a predetermined playback start address.
Note that when recording on the bulk layer 3, address information is embedded in a recording signal.
During reproduction, a predetermined position can be accessed based on the address information inserted in the recording signal.

<4. Second Embodiment>

Next, a second embodiment will be described.
In the second embodiment, the recording laser beam can be irradiated independently, so that the recording of the first signal with respect to the first depth position Ln and the second recording with respect to the second depth position Ln ′ are performed. Two signals are recorded at the same time.

FIG. 14 is a diagram for mainly explaining the configuration of the optical system provided in the recording apparatus (recording / reproducing apparatus 50) as the second embodiment. Specifically, the internal configuration of the optical pickup OP2 provided in the recording / reproducing apparatus 50 is mainly shown.
In the following description, parts that are the same as those already described in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

As can be seen from comparison with FIG. 4, the optical pickup OP2 of the second embodiment is provided with two SOA parts 9-1 and 9-2 as the SOA part 9. This is different from the case of the first embodiment.
In this configuration, the modulation of the laser beam according to the first signal and the modulation of the laser beam according to the second signal can be performed simultaneously.

Hereafter, the recording laser beam emitted from the SOA unit 9-1 is the first recording laser beam, and the recording laser beam emitted from the SOA unit 9-2 is the second recording laser beam. Is written.
The first recording laser beam and the second recording laser beam are applied to the bulk type recording medium 1 through a common optical system (collimation lens 12 to objective lens 20).
At this time, the first recording laser beam is focused on the first depth position Ln, and the second recording laser beam is focused on the second depth position Ln ′. The optical system is configured such that the distance in the depth direction between the focused position of the laser beam and the focused position of the second recording laser beam is the distance Dd. For example, in this example, it is assumed that the SOA part 9-1 and the SOA part 9-2 are shifted by a distance Dd in a direction parallel to the laser optical axis.
With such a configuration, when the lens driving unit 16 is driven and the first recording laser beam is focused on the first depth position Ln, the second recording laser beam is the second depth position Ln. You can focus on '.

Also, it is difficult to form the spot position of the first recording laser beam and the spot position of the second recording laser beam at the same position in the in-plane direction. Accordingly, in the case of this example, the spot position of the first recording laser beam and the spot position of the second recording laser beam are arranged at positions shifted in the linear direction.
The amount of deviation of these spot positions in the line direction is hereinafter referred to as “DL”.

FIG. 15 shows the overall internal configuration of the recording / reproducing apparatus 50 according to the second embodiment.
In FIG. 15, only the SOA unit 9-1, the SOA unit 9-2, the lens driving unit 16, the biaxial actuator 21, and the servo / reproducing laser 22 shown in FIG. 14 are included in the internal configuration of the optical pickup OP2. Extracted and shown.

The recording / reproducing apparatus 50 of the second embodiment includes a recording processing unit 52 instead of the recording processing unit 35 and a controller 53 in comparison with the recording / reproducing apparatus 10 (FIG. 6) of the first embodiment. Instead, a controller 53 is provided.
Further, in this case, a spectroscopic unit 51 that splits the light emitted from the isolator 8 is added, and the laser beam split by the spectroscopic unit 51 is transmitted to the SOA unit 9-1 and the SOA unit 9-2, respectively. The optical fiber 11-1 and the optical fiber 11-2 are provided.

  In this case, the recording processing unit 52 uses the SOA signal 9 of the drive signal D-soa (referred to as drive signal D-soa1) based on the first signal for the first signal and the second signal generated using the conversion table 35A. -1 and a supply of a drive signal D-soa (referred to as drive signal D-soa2) based on the second signal to the SOA unit 9-2 can be performed simultaneously.

The controller 53 instructs the recording processing unit 52 so that the recording of the first signal at the first depth position Ln and the recording of the second signal at the second depth position Ln ′ are performed simultaneously. To do.
The controller 53 is also the same as the controller 43 in the first embodiment in that it performs servo switching control corresponding to recording and reproduction, laser light emission control by an instruction to the laser drive unit 36, and the like. Become.

  Here, as described above, in this example, the spot position of the first recording laser beam and the spot position of the second recording laser beam are separated by a distance DL in the line direction. For this reason, the recording processing unit 52 outputs the first signal (drive signal D-soa1) with a delay corresponding to the distance DL. Thus, the first signal and the second signal can be recorded in synchronization.

  In addition, as a specific processing procedure to be executed by the controller 53 in order to realize the simultaneous recording of the first signal and the second signal, the processing of steps S101 to S103 shown in FIG. 12 is executed. Thereafter, in step S104, an instruction for starting the simultaneous recording of the first signal and the second signal may be performed. Specifically, as processing of step S104 in this case, the laser driving unit 16 is instructed to emit light from the MLLD unit 7, and the recording signal processing unit 52 generates the first signal and the second signal, and the driving signal D based on them. An instruction to start output of -soa1 and drive signal D-soa2 is given.

  For confirmation, the reproduction method is the same as that in the first embodiment, and a description thereof will be omitted.

According to the second embodiment as described above, since the first signal and the second signal can be recorded simultaneously, the recording time can be greatly reduced as compared with the case of the first embodiment. Can be achieved.

<5. Modification>

While the embodiments of the present technology have been described above, the present technology should not be limited to the specific examples described above.
For example, the combination of marks recorded at each mark length and each depth position should not be limited to the one shown in FIG. 10, but can be considered in various ways. These relationships may be selected so that a reproduction signal with a desired mark length can be obtained by the combined reproduction, and should not be limited to those exemplified.

  In the above description, the focus servo is applied to the first depth position Ln on the upper layer side during reproduction. However, the position to apply the focus servo is set to the first depth position Ln. It should not be limited. For example, it may be an intermediate position between the first depth position Ln and the second depth position Ln ′. In that case, a parameter such as a mark size may be determined on the assumption that reproduction is performed with focus servo targeting the position.

  In the above description, recording on the bulk layer 3 is performed while tracking servo based on the reflected light of the reference surface servo laser beam is applied to the reference surface Ref. The tracking servo in can also be performed using ATS (adjacent track servo).

In the above description, the offset of_L is exemplified as the offset from the reference surface Ref. This is because the focus of the objective lens 20 is set so that the reference surface servo laser beam is focused on the reference surface Ref. In a state where the servo lens is controlled and the movable lens 15 driven by the lens driving unit 16 is in the neutral position (hereinafter simply referred to as a neutral state), the focusing position of the recording laser beam is the same position as the reference plane Ref. It is assumed that
The value of the offset of_L may be determined according to which depth position the in-focus position of the recording laser beam in the neutral state is, and is set as an offset from the reference plane Ref. It should not be limited to. For example, when the optical system is designed so that the focal position of the recording laser beam in the neutral state matches the intermediate depth position of the bulk layer 3 (for example, the third information recording layer position L3), The offset of_L may be an offset to each information recording layer position L based on the intermediate depth position.

  In the above description, the bulk type recording medium 1 has been exemplified in the type in which the reference surface Ref is provided on the lower layer side of the bulk layer 3, but in the present technology, the reference surface Ref is provided on the upper layer side of the bulk layer 3. The present invention can also be suitably applied in the case of a certain type. In this case, as the reflective film for forming the reference surface Ref, a selective reflection film for selectively reflecting the laser light for reference surface servo is provided.

  In the description so far, the case where the recording apparatus of the present technology is applied to a recording / reproducing apparatus that performs both recording and reproduction with respect to the optical recording medium has been exemplified. However, the present technology only performs recording with respect to the optical recording medium (recording layer). The present invention can also be suitably applied to a recording-dedicated device (recording device) that is capable of recording data.

Further, the present technology may be configured as follows.
(1)
For a bulk-type optical recording medium in which mark recording is performed at a plurality of positions in the depth direction of the bulk recording layer, mark recording is performed by selectively condensing laser light at different depth positions of the recording layer. A recording unit for performing
An empty mark is recorded with respect to the first depth position and the second depth position in the recording layer so that the respective mark intervals in the depth direction and the in-plane direction are intervals at which combined reproduction is possible. And a control unit that controls the recording unit.
(2)
The recording part
The recording apparatus according to (1), wherein the empty mark whose maximum size is equal to or less than the spot size of the laser beam is recorded.
(3)
The recording apparatus according to (2), wherein an interval between the first depth position and the second depth position is an interval equal to or less than three times a focal depth of the laser beam.
(4)
When the wavelength of the laser beam is λ and the numerical aperture of the objective lens included in the recording unit for condensing the laser beam is NA,
The recording device according to any one of (2) to (3), wherein an interval of λ / (2NA) or more and λ / NA or less is set as the interval in the in-plane direction in which the combined reproduction is possible.
(5)
When a signal to be recorded at the first depth position is a first recording signal and a signal to be recorded at the second depth position is a second recording signal, information is expressed by a code length. A signal generator for generating the first recording signal and the second recording signal capable of reproducing the code length signal by the combined reproduction based on the code length signal;
The control unit
After the recording unit executes either one of the recording of the first recording signal with respect to the first depth position or the recording of the second recording signal with respect to the second depth position, the other The recording apparatus according to any one of (2) to (4).
(6)
When a signal to be recorded at the first depth position is a first recording signal and a signal to be recorded at the second depth position is a second recording signal, information is expressed by a code length. A signal generator for generating the first recording signal and the second recording signal capable of reproducing the code length signal by the combined reproduction based on the code length signal;
The recording part is
The first depth position and the second depth position are configured to be capable of irradiating laser light simultaneously,
The control unit
Causing the recording unit to simultaneously perform recording of the first recording signal at the first depth position and recording of the second recording signal at the second depth position. ) Recording device.

  DESCRIPTION OF SYMBOLS 1 Bulk type recording medium, 2 Cover layer, 3 Bulk layer, 4 Adhesive layer (intermediate layer), 5 Reflective film, Ref reference plane, 6 Substrate, L Information recording layer position (1st depth position), 7 MLLD part , 8 Isolator, 9,9-1, 9-2 SOA section, 10, 50 Recording / reproducing device, 11, 11-1, 11-2 Optical fiber, 12, 23, 28 Collimation lens, 13 Beam splitter, 14 Fixed lens , 15 Movable lens, 16 Lens drive unit, 17 Mirror, 18, 30 1/4 wavelength plate, 19 Dichroic prism, 20 Objective lens, 21 Biaxial actuator, 22 Servo / reproducing laser, 24, 29 Polarizing beam splitter, 25 , 31 Condensing lens, 26 Servo / reproducing light receiving unit, 27 Reference surface servo laser, 32 Reference surface light receiving unit, 35,52 Recording processing unit, 35A Conversion sensor 36, 36 laser drive unit, 37 servo / reproduction matrix circuit, 38 reproduction processing unit, 39 servo circuit, 40 reference surface matrix circuit, 41 position information detection unit, 42 reference surface servo circuit, 43,53 controller, 51 Spectrometer, SW1, SW2 switch, OP1, OP2 Optical pickup

Claims (7)

For a bulk-type optical recording medium in which mark recording is performed at a plurality of positions in the depth direction of the bulk recording layer, mark recording is performed by selectively condensing laser light at different depth positions of the recording layer. A recording unit for performing
An empty mark is recorded with respect to the first depth position and the second depth position in the recording layer so that the respective mark intervals in the depth direction and the in-plane direction are intervals at which combined reproduction is possible. And a control unit that controls the recording unit. The recording part
The recording apparatus according to claim 1, wherein the empty mark whose maximum size is equal to or less than the spot size of the laser beam is recorded. The recording apparatus according to claim 2, wherein an interval between the first depth position and the second depth position is an interval equal to or less than three times a focal depth of the laser beam. When the wavelength of the laser beam is λ and the numerical aperture of the objective lens included in the recording unit for condensing the laser beam is NA,
The recording apparatus according to claim 3, wherein an interval of λ / (2NA) or more and λ / NA or less is set as the interval in the in-plane direction where the combined reproduction is possible. When a signal to be recorded at the first depth position is a first recording signal and a signal to be recorded at the second depth position is a second recording signal, information is expressed by a code length. A signal generator for generating the first recording signal and the second recording signal capable of reproducing the code length signal by the combined reproduction based on the code length signal;
The control unit
After the recording unit executes either one of the recording of the first recording signal with respect to the first depth position or the recording of the second recording signal with respect to the second depth position, the other The recording apparatus according to claim 1, wherein the recording is performed. When a signal to be recorded at the first depth position is a first recording signal and a signal to be recorded at the second depth position is a second recording signal, information is expressed by a code length. A signal generator for generating the first recording signal and the second recording signal capable of reproducing the code length signal by the combined reproduction based on the code length signal;
The recording part is
The first depth position and the second depth position are configured to be capable of irradiating laser light simultaneously,
The control unit
The recording according to claim 1, wherein the recording unit simultaneously performs recording of the first recording signal at the first depth position and recording of the second recording signal at the second depth position. apparatus. A recording method for a bulk type optical recording medium in which mark recording is performed at a plurality of positions in the depth direction in a bulk-shaped recording layer,
An empty mark is recorded with respect to the first depth position and the second depth position in the recording layer so that the mark intervals in the depth direction and the in-plane direction can be combined and reproduced. Yes Recording method.

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