JP2011204323A - Optical recording medium, method for manufacturing optical recording medium and servo control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform focus servo operation to a prescribed layer position in a bulk type optical recording medium where mark recording is performed to the prescribed layer position in which a reflection film is not formed.SOLUTION: A diffraction layer outputting diffraction light capable of forming an image on a light receiving surface as the image on the light receiving surface obtained when the reflection film is formed in the prescribed layer position when radiated light is made incident in the prescribed layer position so as to be focused is provided in the bulk type optical recording medium. Thereby, focus servo operation targeting the prescribed layer position can be performed based on a focus error signal obtained by receiving diffraction light from the diffraction layer on the receiving surface.

Description

  The present invention relates to a bulk type optical recording medium in which mark recording is performed at a predetermined layer position where a reflective film is not formed, and a method for manufacturing the same. The present invention also relates to a servo control method for such a bulk type optical recording medium.

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 refers to an optical recording medium (bulk type recording medium 100) having at least a cover layer 101 and a bulk layer (recording layer) 102 as shown in FIG. This is a technique for increasing the recording capacity by performing multi-layer recording in the bulk layer 102 by irradiating laser light.

  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 102. 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 voids (vacancy, holes) as recording marks as disclosed in Patent Document 2, for example, as a bulk recording method different from the micro-hologram method. .
The void recording method is a technique in which, for example, a laser beam is irradiated at a relatively high power to the bulk layer 102 made of a recording material such as a photopolymerization type photopolymer, and an empty package is recorded in the bulk layer 102. is there. As described in Patent Document 2, the vacant portion formed in this way is a portion having a refractive index different from that of the other portion in the bulk layer 102, 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-cure light irradiation is performed before performing void recording, but void recording is possible even if such pre-cure light irradiation is omitted.

  Here, a bulk type optical recording medium in which various recording methods as described above are proposed. The bulk layer (recording layer) of such a bulk type optical recording medium has, for example, a plurality of reflective films. It does not have an explicit multilayer structure in the sense that it is formed. That is, the bulk layer is not provided with a reflective film for each recording layer as provided in a normal multilayer optical recording medium.

  By using such a bulk-shaped recording layer, it is possible to effectively reduce the manufacturing cost of the optical recording medium in realizing multilayer recording. In other words, when multi-layer recording is performed, if a reflective film is formed for each layer position to be recorded as in a conventional optical disk, the manufacturing cost of the optical recording medium increases in proportion to the increase in recording capacity due to the multi-layer recording. However, according to the structure of the bulk type recording medium 100 as shown in FIG. 16, such an increase in cost is prevented.

However, since the bulk layer 102 does not have a reflective film, a focus servo cannot be applied to a desired layer position by a method similar to the method for a normal optical disc, particularly during recording where a mark is not formed. .
As can be understood from this, in the case of performing bulk recording, some device is necessary so that a mark row can be properly recorded at a desired layer position in the bulk layer 102.

In the present invention, in view of the above problems, the optical recording medium is configured as follows.
That is, the optical recording medium of the present invention is a bulk type optical recording medium in which mark recording is performed on a predetermined layer position where no reflective film is formed,
An image similar to the image obtained on the light receiving surface when a reflection film is formed at the predetermined layer position when light irradiated so that the focal point coincides with the predetermined layer position. Is provided with a diffraction layer configured to output diffracted light that can be formed on the light receiving surface.

In the present invention, the following method is proposed as a method for manufacturing an optical recording medium.
That is, the method for manufacturing an optical recording medium of the present invention is a method for manufacturing a bulk-type optical recording medium in which mark recording is performed on a predetermined layer position where a reflective film is not formed.
An image similar to the image obtained on the light receiving surface when a reflection film is formed at the predetermined layer position when light irradiated so that the focal point coincides with the predetermined layer position. At least a diffraction layer generating step for generating a diffraction layer that outputs diffracted light that can be formed on the light receiving surface.

In the present invention, the servo control method is as follows.
In other words, it is a bulk type optical recording medium in which mark recording is performed at a predetermined layer position where no reflective film is formed, and the light irradiated so that the focal point coincides with the predetermined layer position. To output diffracted light that can form on the light receiving surface an image similar to the image obtained on the light receiving surface when a reflection film is formed at the predetermined layer position when incident. It is obtained by irradiating light through an objective lens to an optical recording medium having a configured diffraction layer and receiving diffracted light from the diffraction layer obtained in response to the light irradiation on the light receiving surface. Based on the focus error signal, focus servo control of the objective lens targeting the predetermined layer position is performed.

As described above, the optical recording medium of the present invention forms a reflective film at the predetermined layer position when light irradiation is performed so that the focal point coincides with the predetermined layer position where mark recording is to be performed. A diffractive layer configured to output diffracted light capable of forming an image similar to the image obtained on the light receiving surface when the light is received.
According to the optical recording medium of the present invention as described above, in response to the fact that light that focuses on the predetermined layer position is irradiated even though no reflective film is actually formed at the predetermined layer position, On the light receiving surface, it is possible to obtain an image as if the light is focused on the reflective film formed at the predetermined layer position. Thus, focus servo control for the predetermined layer position can be performed based on the focus error signal obtained by receiving the diffracted light from the diffraction layer on the light receiving surface. That is, as a result, focus servo can be applied to the predetermined layer position where the reflective film is not formed.

As described above, according to the present invention, for a bulk-type optical recording medium in which mark recording is performed on a predetermined layer position where no reflective film is formed, a focus servo targeting the predetermined layer position is performed. Can be applied.
Since the focus servo can be applied to the predetermined layer position where the reflective film is not formed in this way, mark recording can be appropriately performed on the predetermined layer position in the bulk-shaped recording layer. .

1 is a cross-sectional structure diagram of a bulk type recording medium as a first embodiment. It is a figure for demonstrating the effect | action by a hologram guide layer. It is the figure which showed the example of the production | generation process of a master hologram guide layer. It is a figure for demonstrating the specific example of the manufacturing method of the bulk type recording medium of 1st Embodiment. It is a figure for demonstrating transcription | transfer of the interference fringe from a master hologram guide layer. It is a figure for demonstrating the postcure performed after the transfer of an interference fringe. It is the figure which showed the internal structure of the optical drive device as 1st Embodiment. It is the figure which illustrated the waveform of a Pull In signal and a focus error signal obtained at the time of a focus search operation. It is a figure for demonstrating an example of the specific method of focus servo pull-in. It is the figure which showed the internal structure of the optical drive device as 2nd Embodiment. It is the figure which showed the internal structure of the optical drive device as 3rd Embodiment. It is a cross-section figure of the bulk type recording medium as a 4th embodiment. It is a figure for demonstrating the specific example of the manufacturing method of the bulk type recording medium of 4th Embodiment. It is a figure for demonstrating the other production | generation methods of a master hologram guide layer. It is a figure for demonstrating the bulk type recording medium as a modification. It is a figure for demonstrating bulk recording.

Hereinafter, the best mode for carrying out the invention (hereinafter referred to as an embodiment) will be described.
The description will be made in the following order.

<1. First Embodiment>
[1-1. Structure of optical recording medium]
[1-2. Action by hologram guide layer]
[1-3. Example of manufacturing method of optical recording medium]
[1-4. Configuration of optical drive device and servo control method]
<2. Second Embodiment>
<3. Third Embodiment>
<4. Fourth Embodiment>
<5. Modification>

<1. First Embodiment>
[1-1. Structure of optical recording medium]

FIG. 1 shows a cross-sectional structure of a bulk type recording medium 1 as an embodiment of the optical recording medium of the present invention.
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). 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 FIG. 1, a cover type 2, a hologram guide layer 3, a bulk layer 4, and a substrate 5 are formed on a bulk type recording medium 1 in order from the upper layer side.
Here, the “upper layer side” in this specification refers to an upper layer side when a surface on which a laser beam from an optical drive device (recording / reproducing device 10 or the like) side as an embodiment 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 optical drive device side). The direction parallel to the incident direction of the laser beam (focus direction).

  In the bulk type recording medium 1, the cover layer 2 is made of, for example, a resin such as polycarbonate or acrylic, and functions as a protective layer for a layer (in this case, the hologram guide layer 3) formed on the lower layer side.

The hologram guide layer 3 functions as a layer for guiding the mark recording position in the bulk layer 4 as described later.
The hologram guide layer 3 will be described later.

The bulk layer 4 is a recording layer that does not have a reflective film and that performs mark recording at a predetermined layer position.
As a forming material (recording material) of the bulk layer 4, for example, an appropriate one according to a bulk recording method to be employed, such as the positive micro hologram method, the negative micro hologram method, or the void recording method described above, may be used. It may be adopted.
The mark recording method for the optical recording medium of the present invention is not particularly limited, and any method may be adopted within the category of the bulk recording method. In the following description, as an example, a case where a void recording method is adopted is illustrated.

  The substrate 5 formed on the lower layer side of the bulk layer 4 is made of a resin such as polycarbonate or acrylic.

Here, in the bulk type recording medium 1 having the above configuration, in order to perform multilayer recording in the bulk layer, each layer position (information recording layer position L) where mark recording is to be performed is set in advance. In the bulk type recording medium 1 of the present embodiment, as the information recording layer position L, for example, as shown in the figure, the first information recording layer position L1, the second information recording layer position L2, and the third information recording layer are sequentially arranged from the upper layer side. Assume that a total of five positions L3, fourth information recording layer position L4, and fifth information recording layer position L5 are set.

[1-2. Action by hologram guide layer]

FIG. 2 is a diagram for explaining the operation of the hologram guide layer 3.
FIG. 2A shows a case where light is irradiated by driving the position of the objective lens to a position where the light passing through the objective lens is focused on the information recording layer position L1 set in the bulk layer 4. FIG. 2B is a diagram for explaining the action of the hologram guide layer 3. FIG. 2B shows the position of the objective lens at the information recording layer position L5 where the light passing through the objective lens is set in the bulk layer 4. It is a figure for demonstrating the effect | action by the hologram guide layer 3 at the time of driving to the position which connects a focus, and performing light irradiation.

As a premise here, as shown in FIG. 2, in this embodiment, two types of light, ie, a recording / playback laser beam and a servo laser beam, are applied to the bulk type recording medium 1 with a common objective lens. It is supposed to irradiate through.
The upper recording / reuse laser beam is used to perform mark recording on the bulk layer 4 and reproduction of the recording mark. The servo laser light is irradiated to guide the mark recording position by the upper recording / reuse laser light in the bulk layer 4 based on the action of the hologram guide layer 3 described below.

  As these recording / reproducing laser beam and servo laser beam, laser beams having different wavelengths are used. Specifically, in this example, laser light having a wavelength λ = 405 nm (blue-violet laser light) is used as the upper recording / reuse laser light, and laser light (red laser having a wavelength λ = 640 nm is used as the servo laser light. Light).

  At this time, as the objective lens (the objective lens 17 corresponds to FIG. 7), when both the recording / reproducing laser beam and the servo laser beam are incident as parallel lights, the recording / reproducing laser beam and the servo laser beam are used. Are designed so that their focal positions coincide. Thus, even when the objective lens is driven in the focus direction, the focal positions of the recording / reproducing laser beam and the servo laser beam are always matched.

Based on the above assumptions, the hologram guide layer 3 will be described.
First, in the present embodiment, as the hologram guide layer 3, interference fringes accompanying the irradiation of the reference light and the object light are formed on the hologram recording material, and function as a reflection type diffraction element.
The hologram guide layer 3 is configured such that the following action is obtained by the interference fringe formation pattern. That is, when light irradiated so that the focal point coincides with a predetermined layer position in the bulk layer 4 is obtained on the light receiving surface when a reflective film is formed at the predetermined layer position. This is the action of outputting diffracted light capable of forming an image similar to the obtained image on the light receiving surface.
For the sake of confirmation, the “light-receiving surface” described above is an optical drive device that performs recording (or reproduction) on the bulk-type recording medium 1, and reflects reflected light from the bulk-type recording medium 1 through an objective lens. It refers to the light receiving surface of a light receiving element provided for receiving light.

At this time, in the bulk type recording medium 1, as described above, a plurality of layer positions based on the information recording layer position L1 to the information recording layer position L5 are set as layer positions for performing mark recording in the bulk layer 4. Corresponding to this, the hologram guide layer 3 is specifically configured as follows.
That is, when each of the plurality of layer positions L set in the bulk layer 4 is irradiated with light irradiated so that the focal point coincides with the one layer position L, the reflection film is formed on the one layer position L. In this case, diffracted light that can form on the light receiving surface an image similar to the image obtained on the light receiving surface is output.

  In addition, the hologram guide layer 3 in this case is formed by irradiating the interference light with the reference light and the object light having the same wavelength as the servo laser light. It can be obtained only in response to irradiation of servo laser light. That is, the hologram guide layer 3 in this case has wavelength selectivity with respect to its diffraction action. Such wavelength selectivity is a trivial matter derived from what is called Bragg's law.

The action of the hologram guide layer 3 configured as described above will be described in detail. First, as shown in FIG. 2A, the position of the objective lens is changed to the recording / reproducing laser beam and the servo via the objective lens. When the laser beam is driven and irradiated to a position focused on the information recording layer position L 1 set in the bulk layer 4, recording / reproduction is performed by the wavelength selectivity of the hologram guide layer 3. The laser beam passes through the hologram guide layer 3 and is focused on the information recording layer position L1 in the bulk layer 4.
On the other hand, the servo laser light is diffracted by the hologram guide layer 3, and the diffracted light is returned to the apparatus side through the objective lens. In this case, a reflection film is formed at the information recording layer position L1, and an image similar to that when the servo laser beam is focused on the reflection film is formed. That is, when viewed in the image obtained on the light receiving surface, an action equivalent to that a reflection film is formed at the information recording layer position L1 and the servo laser beam is focused on the reflection film. Is obtained.

  Similarly, as shown in FIG. 2B, the position of the objective lens is moved to the information recording layer position L5 where the recording / reproducing laser beam and the servo laser beam via the objective lens are set in the bulk layer 4. When light irradiation is performed by driving to a focal position, the recording / reproducing laser beam is focused on the information recording layer position L5 by the above wavelength selectivity, while the servo laser beam is emitted from the hologram guide layer. 3 is diffracted at 3, a reflection film is formed on the light receiving surface at the information recording layer position L5, and an image similar to that when the servo laser beam is focused on the reflection film is formed. Will do.

Here, if the distance between the objective lens and the bulk type recording medium 1 is changed, the focal position of the laser light applied to the bulk type recording medium 1 through the objective lens is shown in FIG. When the position is changed from the position shown in 2 (b), the servo laser light image formed on the light receiving surface also changes from the image equivalent to the in-focus state. That is, as a result, the focus error signal obtained by receiving the diffracted light (reflected light) of the servo laser light on the light receiving surface also changes from the signal in the equivalent state to the in-focus state. Become.
As can be understood from this, since the hologram guide layer 3 is provided, the apparatus side records from the focus error signal obtained by receiving the reflected light of the servo laser beam on the light receiving surface. It is possible to know whether or not the focal position of the reuse laser beam is coincident with the desired information recording layer position L as a target. That is, based on the focus error signal for the servo laser beam, focus servo control of the objective lens is performed so that the focal position of the recording / playback laser beam matches the desired information recording layer position L. be able to. In other words, the focus servo can be applied to the desired information recording layer position L with respect to the recording / reproducing laser beam.

Here, in the above description, for the sake of simplicity, the hologram guide layer 3 of the present embodiment is configured to obtain only the image generation function for the focus servo as described above. As the hologram guide layer 3, the following structure is used to enable tracking servo.
That is, the hologram guide layer 3 according to the present embodiment is irradiated with light irradiated so that the focal point coincides with a predetermined layer position in the bulk layer 4 and the focal point is located at a predetermined position in the recording surface direction. When incident, a reflection film having a track is formed at the predetermined layer position, and an image similar to an image obtained on the light receiving surface when the focal point traces on the track is formed on the light receiving surface. It is configured to output diffracted light that can be formed.

The operation when the hologram guide layer 3 having such a configuration is used will be described.
For example, as shown in FIG. 2A, in the state where the objective lens is driven so that the focal position of the recording / reproducing laser beam coincides with the information recording layer position L1, the tracking direction of the objective lens (the bulk type recording medium 1). When the position in the direction parallel to the radial direction of the recording medium (the direction parallel to the in-recording surface direction) is at a position where the focal point of the recording / reproducing laser beam is positioned at a predetermined position in the in-recording surface direction, As the hologram guide layer 3 is used, a reflection film having a track at the information recording layer position L1 is formed as the diffracted light image of the servo laser light obtained on the light receiving surface, and the focus of the servo laser light is obtained. Thus, an image similar to that obtained when tracing on the track is obtained. That is, when viewed from the image on the light receiving surface, a virtual track Vtr_l1 as shown in FIG. 2A is formed at the information recording layer position L1, and the servo laser beam is applied to the virtual track Vtr_l1. An image equivalent to the focus being traced can be obtained.

  Similarly, in the case shown in FIG. 2 (b), when the position of the objective lens in the tracking direction is at a position where the focal point of the recording / reproducing laser beam is located at a predetermined position in the in-recording surface direction, on the light receiving surface. As an image of the diffracted light of the servo laser light obtained, the virtual track Vtr_l5 is formed at the information recording layer position L5, and the focus of the servo laser light is traced to the virtual track Vtr_l5. An image equivalent to is obtained.

  Then, if the relative positional relationship between the objective lens and the bulk type recording medium 1 in the tracking direction is changed, the focal position of the laser light irradiated through the objective lens is changed from the predetermined position in the recording surface in-direction. In the case of deviation, the diffracted light image of the servo laser light obtained on the light receiving surface also changes from the image obtained in a state equivalent to the above trace state. That is, the tracking error signal obtained by receiving the diffracted light of the servo laser light on the light receiving surface also changes from the signal obtained in a state equivalent to the trace state.

By providing the hologram guide layer 3 having the above-described configuration in this way, the apparatus side can record / reproduce the laser light from the tracking error signal obtained by receiving the reflected light of the servo laser light on the light receiving surface. It is possible to know whether or not the focal point is tracing a predetermined position (that is, the formation position of the virtual track Vtr) in the recording surface direction on the information recording layer position L. Accordingly, by controlling the position of the objective lens in the tracking direction based on the tracking error signal, the tracking servo for the recording / reproducing laser beam, specifically, the focus of the recording / reproducing laser beam follows the virtual track Vtr. A tracking servo can be realized.

[1-3. Example of manufacturing method of optical recording medium]

With reference to FIGS. 3-6, the example of the manufacturing method of the bulk type recording medium 1 demonstrated by the above is demonstrated.
First, FIG. 3 shows an example of a process for generating the master hologram guide layer Hm necessary for generating the hologram guide layer 3 described above.
Here, as will be apparent from the following description, in the present embodiment, in order to improve the manufacturing efficiency of the bulk type recording medium 1, the hologram guide layer 3 is first divided into a master hologram guide layer Hm (a hologram guide as a master). The layer 3) is generated, and the interference fringes formed on the master hologram guide layer Hm are transferred to the hologram recording material. In FIG. 3, first, a process of generating such a master hologram guide layer Hm will be described.

In generating the master hologram guide layer Hm, a master hologram guide layer material Hm ′ as an original material of the master hologram guide layer Hm and a master creating multilayer structure 4i as shown in the drawing are prepared.
A hologram recording material may be prepared as the master hologram guide layer material Hm ′. At this time, the thickness of the master hologram guide layer material Hm ′ is set to be the same as that of the hologram guide layer 3.

The master creating multilayer structure 4i is used to form interference fringes for realizing the function as the master hologram guide layer 3 as described in FIG. 2 with respect to the master hologram guide layer material Hm ′. .
In the master creating multilayer structure 4i, a reflective film having a track tr is formed at each layer position corresponding to each information recording layer position L (in this case, L1 to L5) set in the bulk layer 4. .

In this case, the master creating multilayer structure 4i has the same thickness as that of the bulk layer 4, and the track tr is located at a position corresponding to each information recording layer position L in the bulk layer 4. Is formed.
At this time, as the track tr, pit rows or grooves are formed in a spiral shape or a concentric shape.

The master producing multilayer structure 4i can be produced by a method similar to a general method for producing a multilayer disc.
For example, when generating the master creating multilayer structure 4i, a stamper for transferring the track tr is created in advance.
Here, in the case of this example, position information (absolute position information: rotation angle information as information representing the rotation angle position on the disk, radius position information, etc.) is recorded on the track tr. For example, when the track tr is formed by a pit row, the position information is recorded by a combination of pit and land lengths. Alternatively, when the track tr is formed by a groove, the groove is wobbled (wobbled), and position information is recorded based on the meandering period information.

Using the stamper generated as described above, first, a resin substrate to which the unevenness as the lowermost track tr_l5 is transferred is generated by injection molding using the stamper. Then, after a reflective film (a semi-reflective film) is formed on the substrate onto which the track tr_l5 is transferred in this way, for example, an ultraviolet curable resin is applied by a spin coating method or the like, and then the stamper is pressed. Then, the ultraviolet curable resin is cured by irradiating with UV to form a resin layer on which the unevenness as the track tr_l4 is transferred on the substrate. Further, a semi-reflective film is formed on the resin layer thus formed.
In the same way, the formation of the remaining tracks tr_l3 to tr_l1 can be laminated by repeating the application of the UV curable resin, the curing treatment by UV irradiation with the stamper pressed, and the formation of the semi-reflective film. By performing, for example, application of an ultraviolet curable resin and curing treatment by ultraviolet irradiation on the upper semi-reflective film of tr_l1, it is possible to generate a multilayer structure for master creation 4i shown in the drawing.

The generation of the master hologram guide layer Hm is performed with reference light and object light from opposite directions as shown in the figure, with the master hologram guide layer material Hm ′ placed and fixed on the master creating multilayer structure 4i. Irradiation is performed by forming interference fringes on the master hologram guide layer material Hm ′.
Specifically, the formation of the interference fringes in this case is performed by sequentially focusing the object light and the reference light on the respective reflective films formed on the master creating multilayer structure 4i.

  It should be noted at this time that the master creating multilayer structure and the master hologram guide layer material Hm ′ have the same positional relationship as the positional relationship between the bulk layer 4 and the hologram guide layer 3 in the bulk type recording medium 1. It is a point to arrange.

In order to irradiate the master hologram guide layer material Hm ′ with object light, laser light is irradiated through the objective lens OL-b arranged on the lower layer side of the master creating multilayer structure 4i. Thereby, the object light reflecting the image from the reflective film having the track tr can be irradiated from the lower layer side of the master hologram guide layer material Hm ′.
Further, the reference light is irradiated through the objective lens OL-r from the side facing the object light, that is, the upper layer side of the master hologram guide layer material Hm ′.

What is important here is that the wavelengths of the reference light and the object light are the same as those of the servo laser light. In addition, coherent light is used as the reference light and the object light. Further, the numerical apertures of the objective lens OL-r and the objective lens OL-b are set to the numerical apertures of the objective lens (object lens 17 described later) provided in the optical drive device that performs recording (or reproduction) on the bulk type recording medium 1. It is the same as (numerical aperture of servo laser light functioning as reference light).
The reason why the wavelengths of the reference beam and the object beam are the same as those of the servo laser beam is to make the master hologram guide layer Hm (that is, the hologram guide layer 3) have the aforementioned wavelength selectivity.
Further, the numerical apertures of the objective lens OL-r and the objective lens OL-b are the same as the numerical apertures of the objective lens provided in the optical drive device because a plurality of information recording layer positions set in the bulk layer 4 are used. For each of L, when light irradiated so that the focal point coincides with one information recording layer position L is incident on the light receiving surface when a reflective film is formed at the one information recording layer position L This is because an image similar to the image obtained in this way can be formed on the light receiving surface.

FIG. 3A shows a state in which interference fringes corresponding to the information recording layer position L1 are formed on the master hologram guide layer material Hm ′, and FIG. 3B shows the master hologram guide layer material Hm ′. On the other hand, a state in the case of forming interference fringes corresponding to the information recording layer position L5 is shown.
As can be seen with reference to FIGS. 3A and 3B, when an interference fringe corresponding to one information recording layer position L is formed on the master hologram guide layer material Hm ′, the reference light and the object light are used. The semi-reflective film formed at a position corresponding to the one information recording layer position L in the master creating multilayer structure 4i is focused. Such an in-focus state is achieved by performing focus servo control of the objective lens OL-r and the objective lens OL-b for the semi-reflective film formed at a position corresponding to the one information recording layer position L. realizable.
Then, in such a focused state, for example, the position of the master creating multilayer structure 4i to which the master hologram guide layer Hm ′ is fixed is moved horizontally, for example, to reference the master hologram guide layer material Hm ′. The irradiation position of the mixed light of the light and the object light is moved so that the mixed light is irradiated on the entire surface of the master hologram guide layer material Hm ′ (or the entire surface in the necessary region where diffracted light needs to be obtained). . Thereby, interference fringes corresponding to the one information recording layer position L can be formed on the master hologram guide layer material Hm ′.

  Such interference fringes corresponding to one information recording layer position L are sequentially formed with respect to the semi-reflective film formed at the position corresponding to each information recording layer position L, thereby referring to FIG. Thus, it is possible to generate the master hologram guide layer Hm that can obtain the action described above.

In the above description, the master creating multilayer structure 4i has the same thickness as the bulk layer 4, but it is not necessarily required to have the same thickness.
Here, as a diffraction action by the hologram guide layer 3, the light irradiated so that the focal point coincides with one information recording layer position L for each of the plurality of information recording layer positions L set in the bulk layer 4. When a reflection film is formed at the one information recording layer position L when incident, the same image as that obtained on the light receiving surface can be formed on the light receiving surface. In order to obtain the selective diffraction action in the depth direction, the following conditions may be satisfied.
That is, the distance (in the depth direction) from the lower side surface (back surface) of the master hologram guide layer material Hm ′ at the time of generation of the master hologram guide layer Hm as described above to the reflection film having the track tr_l1. Distance) is D1, the distance to the reflective film having the track tr_l2 is D2, the distance to the reflective film having the track tr_l3 is D3, the distance to the reflective film having the track tr_l4 is D4, and the distance to the reflective film having the track tr_l5 Is D5, the distance from the lower side surface of the hologram guide layer 3 in the bulk type recording medium 1 to the information recording layer position L1 is Dv1, the distance to the information recording layer position L2 is Dv2, and the information recording layer The distance to the position L3 is Dv3, the distance to the information recording layer position L4 is Dv4, and the distance to the information recording layer position L5 is Dv5. D1 = Dv1, D2 = Dv2, D3 = Dv3, D4 = Dv4, D5 = Dv5.
Therefore, the thickness of the master creating multilayer structure 4 i is not necessarily the same as the thickness of the bulk layer 4.

FIG. 4 is a diagram for explaining a specific example of a method for manufacturing the bulk type recording medium 1 using the master hologram guide layer Hm generated as described above.
In the manufacturing method in this case, first, as shown in FIG. 4A, the bulk layer 4 is laminated on the substrate 5. As described above, the substrate 5 is made of a resin such as polycarbonate or acrylic. As for the bulk layer 4, in addition to the photopolymer exemplified in Patent Document 2 described above, a resin can be used in accordance with the case of performing mark recording by the void recording method as in the case of this example.

  After the bulk layer 4 is laminated on the substrate 5, as shown in FIG. 4B, a layer composed of a hologram recording material as the hologram guide layer material 3 'is laminated. In this example, for example, a photopolymer is used as the hologram recording material.

  Then, for the hologram guide layer material 3 ′ laminated in this way, the interference fringe transfer using the master hologram guide layer Hm and the post cure after the interference fringe transfer are performed (FIG. 4C). ).

Here, as shown in FIG. 5, the transfer of the interference fringes to the hologram guide layer material 3 ′ is performed with the master hologram guide layer Hm placed and fixed on the upper side of the hologram guide layer material Hm. This is performed by irradiating parallel light from the upper layer side of the layer Hm.
At this time, the parallel light irradiation is performed over the entire surface of the master hologram guide layer Hm. The wavelength of the parallel light is the same as that of the servo laser light.
By such parallel light irradiation, the light diffracted by the master hologram guide layer Hm becomes object light (signal light), and the light transmitted through the master hologram guide layer Hm becomes reference light to the hologram guide layer material 3 ′. Thus, an interference fringe similar to the interference fringe formed on the master hologram guide layer Hm can be formed (that is, transferred) on the hologram guide layer material 3 ′.

The hologram guide layer material 3 ′ after the transfer of the interference fringes is subjected to a post cure process as shown in FIG. The post-cure process is performed by irradiating the hologram guide layer material 3 ′ with incoherent light such as light using an LED (Light Emitting Diode) as a light source.
As is well known, in hologram recording materials such as photopolymers, interference fringes are formed by polymerizing monomers in response to light irradiation. As described above, when the hologram guide layer material 3 ′ after the transfer of interference fringes is irradiated with incoherent light, all of the residual polymer in the hologram guide layer material 3 ′ can be reacted, and subsequent polymerization is performed, that is, unnecessary. Formation of interference fringes can be prevented. As a result, the transferred interference fringes can be fixed in the transferred form.
The hologram guide layer 3 is completed by post-curing in this way and fixing the interference fringes transferred from the master hologram guide layer Hm.

After the transfer of the interference fringes and the post cure as described above, the cover layer 2 is laminated on the upper layer side of the hologram guide layer 3 as shown in FIG. Thereby, the bulk type recording medium 1 as this Embodiment is produced | generated.

[1-4. Configuration of optical drive device and servo control method]

FIG. 7 shows an internal configuration of an optical drive device (hereinafter referred to as a recording / reproducing apparatus 10) as a first embodiment that performs recording / reproduction corresponding to the bulk type recording medium 1.
In FIG. 7, the bulk type recording medium 1 is set so that its center hole is clamped at a predetermined position in the recording / reproducing apparatus 10, and is held in a state where it can be rotationally driven by a spindle motor (not shown).
An optical pickup OP1 in the drawing is provided to irradiate recording / reproducing laser light and servo laser light onto the bulk type recording medium 1 that is rotationally driven by the spindle motor.

In the optical pickup OP1, a recording / reproducing laser 11 which is a light source of a recording / reproducing laser beam for recording information by the mark and reproducing information recorded by the mark, and diffracted light from the hologram guide layer 3 ( A servo laser 21 which is a light source of servo laser light which is light for performing position control using reflected light) is provided.
Here, as described above, in this example, the wavelength of the recording / reproducing laser beam is about 405 nm, and the wavelength of the servo laser beam is about 640 nm.

In addition, an objective lens 17 serving as an output end of the recording / reproducing laser beam and the servo laser beam to the bulk type recording medium 1 is provided in the optical pickup OP1.
In this case, the numerical aperture of the objective lens 17 is about 0.85 for the recording / reproducing laser beam, and about 0.65 for the servo laser beam.
Further, what is important in the present embodiment is that the optical system is designed so that the recording / reproducing laser beam and the servo laser beam are incident on the objective lens 17 as parallel light as shown in the figure, and Thus, the objective lens 17 is designed so that the recording / reproducing laser beam and the servo laser beam incident on the objective lens 17 in parallel light are focused at the same position.

  In the optical pickup OP 1, the recording / reproducing laser beam emitted from the recording / reproducing laser 11 is guided to the objective lens 17, and the recording / reproducing laser beam incident on the objective lens 17 from the bulk type recording medium 1 is used. An optical system for guiding the reflected light to the recording / reproducing light receiving unit 20 in the figure is formed.

Specifically, the recording / reproducing laser beam emitted from the upper recording / reproducing laser 11 is made parallel light through the collimator lens 12 and then enters the polarization beam splitter 13.
The polarization beam splitter 13 is configured to transmit the recording / reproducing laser light incident from the recording / reproducing laser 11 side in this way.

  The recording / reproducing laser light transmitted through the polarizing beam splitter 13 is reflected by the mirror 14 in the figure so that its optical axis is bent by 90 °, and then is reflected on the dichroic prism 16 via the quarter-wave plate 15. Incident. The dichroic prism 16 is configured such that its selective reflection surface transmits light in the same wavelength band as that of the recording / reproducing laser beam and reflects light of other wavelengths. Therefore, the recording / reproducing laser beam incident as described above is transmitted through the dichroic prism 16.

The recording / reproducing laser light transmitted through the dichroic prism 16 is irradiated onto the bulk type recording medium 1 through the objective lens 17 as shown in the figure.
The objective lens 17 is provided with a biaxial actuator 18 that holds the objective lens 17 so as to be displaceable in the focus direction and the tracking direction.
The biaxial actuator 18 is provided with a focus coil and a tracking coil, and is supplied with drive signals (drive signals FD and TD to be described later), thereby displacing the objective lens 17 in the focus direction and the tracking direction, respectively.

Here, at the time of reproduction, the bulk type recording medium 1 (information to be reproduced in the bulk layer 4) according to the irradiation of the recording / reproducing laser beam to the bulk type recording medium 1 as described above. The reflected light of the upper recording reuse laser beam is obtained from the mark row recorded at the recording layer position L). The reflected light of the recording / reproducing laser beam thus obtained is guided to the dichroic prism 16 through the objective lens 17 and is transmitted through the dichroic prism 16.
The reflected light of the recording / reproducing laser light transmitted through the dichroic prism 16 enters the polarization beam splitter 13 after passing through the quarter-wave plate 15 → the mirror 14.

  Here, the reflected light (return light) of the recording / reproducing laser light incident on the polarization beam splitter 13 in this way is due to the action by the quarter wavelength plate 15 and the action at the time of reflection by the bulk type recording medium 1. The polarization direction of the recording / reproducing laser beam (outgoing light) incident on the polarization beam splitter 13 from the recording / reproducing laser beam 11 side is different by 90 degrees. As a result, the reflected light of the recording / reproducing laser beam incident as described above is reflected by the polarization beam splitter 13.

  Thus, the reflected light of the recording / reproducing laser beam reflected by the polarization beam splitter 13 is condensed on the light receiving surface of the recording / reproducing light receiving unit 20 via the condenser lens 19.

Further, in the optical pickup OP1, in addition to the configuration of the optical system for the recording / reproducing laser beam described above, the servo laser beam emitted from the servo laser 21 is guided to the objective lens 17, and the objective lens An optical system for guiding the reflected light of the servo laser light from the bulk type recording medium 1 incident on 17 (diffracted light from the hologram guide layer 3) to the servo light receiving portion 27 in the figure is formed.
As shown in the figure, the servo laser light emitted from the servo laser 21 is converted into parallel light through the collimator lens 22 and then enters the polarization beam splitter 23. The polarization beam splitter 23 is configured to transmit the servo laser light (outgoing light) incident from the servo laser 21 side in this way.

The servo laser light transmitted through the polarization beam splitter 23 is incident on the dichroic prism 16 via the quarter wavelength plate 24.
As described above, the dichroic prism 16 is configured to transmit light in the same wavelength band as that of the recording / reproducing laser beam and reflect light of other wavelengths, so that the servo laser beam is dichroic prism. 16, and the bulk type recording medium 1 is irradiated through the objective lens 17 as shown in the figure.

In addition, the reflected light of the servo laser light obtained in response to the irradiation of the servo laser light to the bulk type recording medium 1 is reflected by the dichroic prism 16 after passing through the objective lens 17, The light enters the polarization beam splitter 23 through the quarter-wave plate 24.
In the same manner as in the case of the previous recording / reproducing laser beam, the reflected light (return light) of the servo laser beam incident from the bulk type recording medium 1 side is the action of the quarter wavelength plate 24 and the bulk type. Due to the action at the time of reflection on the recording medium 1, the polarization direction differs from that of the forward light by 90 degrees. Therefore, the reflected light of the servo laser light as the backward light is reflected by the polarization beam splitter 23.

  The reflected light of the servo laser light reflected by the polarization beam splitter 23 is given astigmatism by the cylindrical lens 26 after passing through the condenser lens 25, and then the light receiving surface of the light receiving unit 29 for servo light. Concentrate on top.

  Here, although description by illustration is omitted, 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 by the slide drive unit is provided. By driving this, the irradiation position of the laser beam can be displaced over a wide range.

  In addition to the optical pickup OP1, the recording / reproducing apparatus 10 includes a signal processing system for performing recording / reproduction for the bulk layer 4 and focus / tracking control of the objective lens 17 during mark recording / reproduction. As shown in the figure, a recording processing unit 28, a recording / reproducing light signal generation circuit 29, a reproduction processing unit 30, a servo light signal generation circuit 31, a position information detection unit 32, and a servo circuit 33 are provided.

Data to be recorded on the bulk type recording medium 1 (recording data) is input to the recording processing unit 28. The recording processing unit 28 adds, for example, 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.
The recording processing unit 28 drives the recording / reproducing laser 11 in the optical pickup OP1 to emit light by the recording pulse Rcp based on the recording modulation data string generated in this way.

The recording / reproducing light signal generation circuit 29 corresponds to a light reception signal DT-rp (output current) from a plurality of light receiving elements as the recording / reproducing light receiving unit 20 in the optical pickup OP1. Etc., and necessary signals are generated. Specifically, in this case, a high-frequency signal (hereinafter referred to as a reproduction signal RF) corresponding to a reproduction signal obtained by reproducing the above-described recording modulation data string is generated.
The reproduction signal RF generated by the recording / reproducing light signal generation circuit 29 is supplied to the reproduction processing unit 30.

  The reproduction processing unit 30 performs reproduction processing for restoring the recording data, such as binarization processing, recording modulation code decoding / error correction processing, and the like to reproduce the recording data. Get the data.

In the signal processing system for the reflected light of the servo laser light, the servo light signal generation circuit 31 is based on the light reception signals DT-sv from the plurality of light receiving elements in the servo light receiving unit 27 in the optical pickup OP1. Generate the necessary signals.
Specifically, the servo light signal generation circuit 31 generates a focus error signal FE and a tracking error signal TE for each focus / tracking servo control. Here, in the present embodiment, a focus error signal by the astigmatism method is generated as the focus error signal FE.
The servo light signal generation circuit 31 generates a position information detection signal Dps for detecting absolute position information recorded on the virtual track Vtr (equivalent to the track tr in FIG. 3). 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 32. The position information detector 32 detects the absolute position information recorded in the virtual track Vtr based on the position information detection signal Dps. The detected absolute position information is supplied to the controller 36.
Here, the detection result of the absolute position information recorded on the virtual track Vtr in this way is expressed as absolute position information PS.

The focus error signal FE and tracking error signal TE generated by the servo light signal generation circuit 31 are supplied to the servo circuit 33.
The servo circuit 33 generates a focus servo signal FS and a tracking servo signal TS based on the focus error signal FE and the tracking error signal TE, respectively. The focus servo signal FS is output to the focus driver 34 and the tracking servo signal TS is output to the tracking driver 35.
The focus driver 34 drives the focus coil of the biaxial actuator 18 described above by the focus drive signal FD generated based on the focus servo signal FS. The tracking driver 35 drives the tracking coil of the biaxial actuator 18 with a tracking drive signal TD generated based on the tracking servo signal TS.
Thereby, focus servo control and tracking servo control of the objective lens are realized.

  The servo circuit 33 realizes a track jump operation by turning off the tracking servo loop and giving a jump pulse to the tracking driver 35 in accordance with an instruction given from the controller 36, and also performs tracking servo pull-in control, etc. Do.

The servo circuit 33 also performs focus servo pull-in control with respect to the target information recording layer position L in the bulk layer 4 in accordance with an instruction from the controller 36.
The focus servo pull-in method for such a desired information recording layer position L will be described below again.

The controller 36 includes a microcomputer having a memory (storage device) such as a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory), for example, and 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 control and processing according to the above.
Specifically, the controller 36 performs seek operation control on the servo circuit 33. That is, based on the absolute position information PS supplied from the position information detection unit 32, the servo circuit 33 is instructed to move the focal position of the recording / reproducing laser beam to a predetermined position on the virtual track Vtr.

  Further, the controller 36 instructs the servo circuit 33 to specify the information recording layer position L to be recorded or reproduced, and causes the focus servo pull-in to the information recording layer position L to be the target.

Here, with reference to FIGS. 8 and 9, the focus servo pull-in method to the desired information recording layer position L when the bulk type recording medium 1 having the hologram guide layer 3 is used will be described. deep.
FIG. 8 shows a Pull In signal (sum signal) waveform (FIG. 8A) obtained when the objective lens 17 is driven in a direction approaching the bulk type recording medium 1, for example, as a focus search operation, and a focus error signal FE. The waveform (FIG.8 (b)) is shown. In addition, for comparison, the waveform of the Pull In signal when the same focus search operation is performed on an optical disc having a normal multilayer structure (that is, a multilayer structure with a reflective film) (FIG. 8C) is shown. ing.
Note that this figure shows an example in which a focus search is performed on the bulk type recording medium 1 when the set number of information recording layer positions L is 8 or more.

As can be seen with reference to FIG. 8A, when a focus search is performed on the bulk type recording medium 1 on which the hologram guide layer 3 is formed, a Pull In signal is recorded as a recording light irradiated through the objective lens 17. Each time the focal point of the reuse laser beam coincides with the information recording layer position L, the peak level is reached, and the level decreases as the focal point of the recording / reproduction laser beam gradually moves away from the information recording layer position L. It will be a thing.
This is because, as described above, the focal point of the recording / reproducing laser beam coincides with the information recording layer position L (that is, the servo laser beam with respect to the hologram guide layer 3 has its focal point coincident with the information recording layer position L). In this state, a reflection film is formed at the information recording layer position L on the light receiving surface of the servo light receiving unit 27, and the same image as when the servo laser beam is focused on the reflection film is formed. This is because the hologram guide layer 3 is formed so as to be obtained.

  Due to the action of the hologram guide layer 3 as described above, the focus error signal FE is S-shaped each time the focal point of the recording / reproducing laser beam coincides with the information recording layer position L as shown in FIG. The zero cross point of the waveform can be obtained.

  In the case of a multi-layer, it is considered that the Pull In signal is maintained at a substantially constant level after passing through the reflective film (recording film) formed on the top as shown in FIG. 8C. This is because, in a normal multi-layer disc with a reflective film, the Pull In signal level does not drop due to the occurrence of interlayer crosstalk, although it depends on the formation interval of each reflective film.

As can be seen with reference to FIG. 8, even when the bulk type recording medium 1 is the target, the same waveform as that of the current optical disc can be obtained as the focus error signal FE obtained during the focus search operation.
Also, with respect to the Pull In signal, when the above-described interlayer crosstalk is not generated (that is, when the number of layers is small and there is room in the formation interval of the reflective film), the same as in the case of the current optical disc. Waveform is obtained.
From these points, even when recording / reproducing is performed on the bulk type recording medium 1, the focus servo pull-in is performed using the focus error signal FE or the Pull In signal, as in the case of the current optical disk system. A similar technique can be used.

FIG. 9 is a diagram for explaining an example of a specific method of focus servo pull-in when the bulk type recording medium 1 is a target.
In FIG. 9, as an example, the waveform of the focus error signal FE (FIG. 9 (a)) and the waveform of the Pull In signal (FIG. 9 (b)) when focus servo pull-in is performed for the information recording layer position L2 are shown. Show.

When the bulk type recording medium 1 is used as described above, the number of Pull In signal peaks and the number of zero cross points of the focus error signal FE during the focus search operation are counted as in the case of the current optical disc system. By doing so, it is possible to grasp at which layer position the focus of the light irradiated through the objective lens 17 is. Therefore, as in the case of the current optical disk system, the current focus position can be grasped from the Pull In signal and / or the focus error signal FE during the focus search, and the information recording layer position L targeted by the focus position can be pulled in. At the timing assumed to be within the range, the focus servo loop is turned on to perform servo pull-in.
Thereby, focus servo can be applied to an arbitrary information recording layer position L as a target.

Here, in the recording / reproducing apparatus 10 according to the first embodiment described above, when applying the focus (and tracking) servo to the bulk type recording medium 1, the servo recording is performed separately from the recording / reproducing laser beam. It is assumed that laser light is irradiated. That is, corresponding to this, as the bulk type recording medium 1, the hologram guide layer 3 is configured so that diffracted light can be obtained only with respect to the servo laser light.
With such a configuration, the recording / reproducing laser beam is not diffracted by the hologram guide layer 3, and as a result, it is not necessary to increase the laser power (recording power and reproducing power) more than necessary. .

In the recording / reproducing apparatus 10, a dichroic prism 16 is provided so that the reflected light of the recording / reproducing laser beam and the reflected light of the servo laser beam are separately guided to the respective detection systems. In other words, this prevents the reflected light from the recorded mark row of the recording / playback laser beam from being leaked into the detection system of the reflected light of the servo laser beam at the time of playback. Servo control and absolute position information The PS is properly detected.
However, at present, it is very difficult to provide a dichroic prism 16 having complete wavelength selectivity due to problems such as manufacturing cost. That is, in this way, the reflected light of the recording / reproducing laser beam may actually leak into the servo laser beam detection system. At this time, the diffraction efficiency in the hologram guide layer 3 is 1% or less at best, and the reflectance of the mark (void) is about several percent exceeding this. Therefore, there is a possibility that the leakage of the recording / reproducing laser beam as described above cannot be ignored.
Therefore, in actuality, the optical system is designed so that the focal position of the recording / reproducing laser beam and the focal position of the servo laser beam (which is precisely the “position to be focused”) are slightly shifted. May be. The shifting direction may be any of a focus direction, a tracking direction, and a tangential direction. When shifting in the focus direction, it is necessary to separate the focus servo pull-in range by several μm. Further, the tracking direction and the tangential direction may be separated by one track or more (for example, 0.6 μm or more).
Of these, shifting in the tangential direction is most desirable for realizing proper focus servo and tracking servo.

<2. Second Embodiment>

Next, a second embodiment will be described.
In the second embodiment, recording and reproduction with respect to the bulk type recording medium 1 is performed by a recording / reproducing apparatus 40 different from the recording / reproducing apparatus 10 of the first embodiment.

FIG. 10 shows an internal configuration of a recording / reproducing apparatus 40 as the second embodiment.
In FIG. 10, parts that have already been described in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  Here, in the recording / reproducing apparatus 10 of the first embodiment, the focus servo, tracking servo, and position information using the diffracted light from the hologram guide layer 3 of the servo laser light both during recording and during reproduction. In the recording / reproducing apparatus 40 of the second embodiment, the servo control and the position are performed based on the diffracted light from the hologram guide layer 3 during recording as in the case of the first embodiment. Information is detected. During reproduction, servo control and position information detection are performed based on the reflected light from the recorded mark row of the recording / reproducing laser beam.

First, the optical pickup OP2 in the figure will be described.
The optical pickup OP2 provided in the recording / reproducing apparatus 40 is a cylindrical lens 41 for enabling the generation of a focus error signal by the astigmatism method in the optical system of the recording / reproducing laser beam as compared with the previous optical pickup OP1. The point that was added is different.
The cylindrical lens 41 is inserted between the condenser lens 19 and the recording / reproducing light receiving unit 20.

The recording / reproducing apparatus 40 includes a recording processing unit 42 instead of the recording processing unit 28 shown in FIG. 7 and a recording / reproducing light signal generation circuit 29 as compared with the recording / reproducing apparatus 10. A recording / reproducing light signal generation circuit 43, a servo light servo circuit 46 in place of the servo circuit 46, and a controller 47 in place of the controller 36 are provided.
Further, an address detector 44 and a recording / reproducing servo circuit 45 are newly added to the recording / reproducing apparatus 40.

  First, the recording processing unit 42 is the same as the previous recording processing unit 28 in that it performs recording modulation encoding processing on input recording data and light emission driving of the recording / reproducing laser 11 by the recording pulse Rpc. The unit 42 further performs a process of embedding address information in the recording data.

  Here, as described above, in the second embodiment, the servo control using the diffracted light of the servo laser light from the hologram guide layer 3 and the detection of the position information are not performed at the time of reproduction. Servo control and position information detection are performed using reflected light from a recorded mark row. Therefore, the address information is embedded in the recording data by the recording processing unit 42 as described above, that is, the address information is embedded in the mark string, so that the position information can be detected during reproduction.

The recording / reproducing light signal generation circuit 43 generates the reproduction signal RF based on the light receiving signals D-rp from the plurality of light receiving elements as the recording / reproducing light receiving unit 20, and in this case, the focus error signal FE, And a tracking error signal TE is also generated.
Here, with respect to the focus error signal FE and tracking error signal TE generated by the recording / reproducing light signal generation circuit 43 in this way, the focus error signal FE and tracking error generated by the servo light signal generation circuit 31 are described. In order to distinguish from the signal TE, the codes are FE-rp and TE-rp, respectively.
At the same time, the signs of the focus error signal FE and the tracking error signal TE generated by the servo light signal generation circuit 31 are FE-sv and TE-sv, respectively.

The reproduction signal RF generated by the recording / reproducing light signal generation circuit 43 is also supplied to the reproduction processing unit 30 in this case, thereby obtaining reproduction data.
The reproduction data in this case is input to the address detection unit 44.
The address detector 44 detects address information embedded in the reproduction data. The address information obtained as a result of detection by the address detection unit 44 is referred to as address information Ad.
As shown in the figure, the address information Ad is supplied to the controller 47.

Further, the focus error signal FE-rp and the tracking error signal TE-rp generated by the recording / reproducing light signal generating circuit 43 are supplied to the recording / reproducing light servo circuit 45.
The recording / reproducing light servo circuit 45 generates a focus servo signal FS-rp and a tracking servo signal TS-rp based on the focus error signal FE-rp and the tracking error signal TE-rp, respectively. Then, the focus servo signal FS-rp is output to the focus driver 34, and the tracking servo signal TS-rp is output to the tracking driver 35.
As a result, a focus servo loop and a tracking servo loop (based on the reflected light of the recording / reproducing laser beam) during reproduction are formed.

The recording / reproducing light servo circuit 45 implements a track jump operation by turning off the tracking servo loop and giving a jump pulse to the tracking driver 35 in response to an instruction given in response to playback from the controller 47. In addition, tracking servo pull-in control (vs. recorded mark row) is also performed.
The recording / reproducing light servo circuit 45 pulls in the focus servo with respect to the mark row formed at the target information recording layer position L in the bulk layer 4 in accordance with an instruction given from the controller 47 in response to reproduction. Also controls.

In this case, the focus error signal FE-sv and the tracking error signal TE-sv generated by the servo light signal generation circuit 31 are supplied to the servo light servo circuit 46.
The servo circuit for servo light 46 generates a focus servo signal FS-sv and a tracking servo signal TS-sv based on the focus error signal FE-sv and the tracking error signal TE-sv, respectively, and uses the focus servo signal FS-sv as a focus driver. The tracking servo signal TS-sv is output to the tracking driver 35.
This forms a focus servo loop and a tracking servo loop (based on the diffracted light of the servo laser light from the hologram guide layer 3) during recording.

Also, the servo light servo circuit 46 realizes a track jump operation by applying a jump pulse to the tracking driver 35 by turning off the tracking servo loop in accordance with an instruction given in response to recording from the controller 47, Also, tracking servo pull-in control (vs. virtual track Vtr) is performed.
The servo light servo circuit 46 also performs focus servo pull-in control with respect to the target information recording layer position L in the bulk layer 4 in accordance with an instruction given from the controller 47 in response to recording.
Needless to say, the focus servo pull-in method may be the same as that described in the first embodiment.

Compared with the previous controller 36, the controller 47 further performs servo switching control during recording and during reproduction as described below.
That is, as the servo switching control, the controller 47 instructs the servo light servo circuit 46 to generate and output the focus servo signal FS-sv and the tracking servo signal TS-sv at the time of recording. The circuit 45 is instructed not to generate and output the focus servo signal FS-rp and the tracking servo signal TS-rp.
On the other hand, at the time of reproduction, the recording / playback light servo circuit 45 is instructed to generate and output the focus servo signal FS-rp and the tracking servo signal TS-rp, and the servo light servo circuit 46 is directed to the focus servo signal. An instruction is given not to generate and output FS-sv and tracking servo signal TS-sv.

  Further, the controller 47 performs a seek operation control on the servo light servo circuit 46 based on the absolute position information PS supplied from the position information detection unit 32 at the time of recording, and the address information Ad supplied from the address detection unit 44 at the time of reproduction. Based on this, seek operation control for the recording / reproducing light servo circuit 45 is performed.

According to the recording / reproducing apparatus 40 described above, at the time of reproduction, the servo can be directly applied to the recorded mark row based on the reflected light from the recorded mark row of the recording / reproducing laser beam. Therefore, the servo control accuracy at the time of reproduction can be improved accordingly.
Further, servo control and position information detection during reproduction can be performed using the recording / reproducing laser beam in this way, so that the servo laser 21 can be turned off during reproduction. This can be advantageous in terms of power consumption, for example.

<3. Third Embodiment>

FIG. 11 shows an internal configuration of a recording / reproducing apparatus 50 as an optical drive apparatus according to the third embodiment.
In FIG. 11 as well, parts that are the same as the parts that have been described so far are assigned the same reference numerals, and descriptions thereof are omitted.

  The third embodiment does not irradiate the servo laser beam separately, but performs mark recording / reproduction and servo control / position information detection only by irradiating the recording / reproducing laser beam.

Here, in the third embodiment in which only the recording / reproducing laser beam is irradiated as described above, the bulk type recording medium 1, that is, the hologram guide layer 3 used in the first and second embodiments is used. When the bulk type recording medium 1 configured to selectively diffract only the servo laser beam is used, the diffracted light of the recording / reproducing laser beam from the hologram guide layer 3 cannot be obtained, and therefore, at the time of recording. Servo control and position information cannot be detected.
Therefore, in the third embodiment, a bulk type recording medium (hereinafter referred to as a bulk type recording medium 1 ′) having a hologram guide layer 3 configured to diffract the recording / reproducing laser beam is used.
As the hologram guide layer 3 that diffracts the recording / reproducing laser beam in this way, the object light and signal light irradiated when the master hologram guide layer Hm shown in FIG. 3 is generated, and the irradiation shown in FIG. As the parallel light to be generated, laser light having the same wavelength as the recording / reproducing laser light can be used.

  For confirmation, even if the hologram guide layer 3 that diffracts the recording / reproducing laser beam is used, the zero-order light component of the recording / reproducing laser beam that passes through the hologram guide layer 3 is bulky. Layer 4 will be reached. That is, recording / reproduction with respect to the bulk layer 4 can be performed thereby.

Based on the above assumptions, the recording / reproducing apparatus 50 shown in FIG. 11 will be described.
First, in this case, an optical pickup OP3 in which the servo laser light optical system and the dichroic prism 16 are omitted from the optical pickup OP2 provided in the recording / reproducing apparatus 40 of the second embodiment is provided. The servo laser light optical system refers to [servo laser 21, collimator lens 22, polarization beam splitter 23, quarter wavelength plate 24, condensing lens 25, cylindrical lens 26, servo light receiving unit 27]. .

  In the recording / reproducing apparatus 50, the servo light signal generating circuit 31 and the servo light servo circuit 46 provided in the previous recording / reproducing apparatus 40 are omitted, and the recording / reproducing light signal generating circuit 43 is replaced. A signal generation circuit 51, a servo circuit 52 in place of the recording / reproducing light servo circuit 45, and a controller 53 in place of the controller 47 are provided.

  The signal generation circuit 51 is based on the received light signal DT-rp from the recording / reproducing light receiving unit 20 in the optical pickup OP3, and detects a position information detection signal Dps, a reproduction signal RF, a focus error signal FE-rp, and a tracking error signal. Generate TE-rp.

Here, at the time of recording, since no mark has been recorded in the bulk layer 4, the focus error signal FE-rp and the tracking error TE-rp are generated based on the diffracted light from the hologram guide layer 3, respectively. Will be.
On the other hand, at the time of reproduction, the recording / reproducing light receiving unit 20 receives the reflected light component from the recorded mark row. At this time, if the diffraction efficiency in the hologram guide layer 3 is 1% or less and the reflectance of the mark is about several percent as described above, the reflected light component received by the recording / reproducing light receiving unit 20 during reproduction is as follows. The reflected light component from the mark row is dominant. Therefore, at the time of reproduction, a focus error FE-rp and a tracking error signal TE-rp are generated based on the reflected light from the recorded mark row.

Also, as the position information detection signal Dps, the position information detection signal Dps generated at the time of reproduction is based on the recorded mark string because of the relationship of “diffraction efficiency of the hologram guide layer 3 << mark reflectance” as described above. Therefore, it is very difficult to accurately detect position information using this.
Therefore, also in the third embodiment, with respect to the position information at the time of reproduction, the address information embedded in the recorded data at the time of recording is detected, and the detection result is used. For this reason, the recording / reproducing apparatus 50 is also provided with the recording processing unit 42 and the address detecting unit 44 as in the case of the second embodiment. In this case, the address information Ad obtained at the time of reproduction by the address detection unit 44 is supplied to the controller 53.

  The position information detection signal Dps generated by the signal generation circuit 51 is supplied to the position information detection unit 32. The absolute position information PS detected by the position information detector 32 is supplied to the controller 53 and used for seek operation control during recording.

The servo circuit 52 receives the focus error signal FE-rp and the tracking error signal TE-rp generated by the signal generation circuit 51.
The servo circuit 52 generates a focus servo signal FS-rp and a tracking servo signal TS-rp based on the focus error signal FE-rp and tracking error signal TE-rp, and outputs them to the focus driver 34 and tracking driver 35, respectively.
The servo circuit 52 also performs focus servo / tracking servo pull-in control and output of a track jump pulse based on an instruction from the controller 53.

The controller 53 is the same as the controller 47 except that the servo switching control between recording and reproduction described in the second embodiment is not performed.
In this case, the controller 53 performs seek operation control on the servo circuit 52 based on the absolute position information PS supplied from the position information detector 32 during recording. At the time of reproduction, seek operation control for the servo circuit 52 is performed based on the address information Ad supplied from the address detection unit 44.

According to the recording / reproducing apparatus 50 as the third embodiment as described above, a recording / reproducing operation including servo control and position information detection is performed using only a single light source as the recording / reproducing laser 11. Therefore, the optical system can be configured simply, and the number of parts and the product cost can be reduced.

<4. Fourth Embodiment>

In the fourth embodiment, the hologram guide layer is not formed by forming interference fringes on the hologram recording material, but is formed by a so-called embossed hologram.

FIG. 12 shows a cross-sectional structure of a bulk type recording medium 60 as the fourth embodiment.
Here, the interference fringes formed in the previous hologram guide layer 3 can also be realized by an uneven pattern. That is, it can be realized by a so-called embossed hologram.
As shown in the drawing, the bulk type recording medium 60 is provided with a surface having an uneven cross-sectional shape, and a reflective film 62 is formed thereon. Thus, the reflective film 62 formed so as to have an uneven cross-sectional shape performs the same function as the hologram guide layer 3. In this sense, hereinafter, the reflective film 62 is also referred to as a hologram guide layer 62.

Here, when the servo laser light is irradiated separately from the recording / reproducing laser light and servo control is performed based on the diffracted light of the servo laser light as in the first and second embodiments, the recording is performed. In order to allow the reuse laser beam to reach the bulk layer 4, the reflection film 62 has a wavelength selectivity that reflects light in the same wavelength band as the servo laser beam and transmits light in other wavelengths. A reflective film is used.
Further, a semi-reflective film is used as the reflective film 62 in correspondence with the case where only the recording / reproducing laser beam is irradiated as in the third embodiment. In this case, the reflective film 62 does not need to have wavelength selectivity in particular.

  In the bulk type recording medium 60, the cover layer 61 is formed on the upper layer side of the hologram guide layer 62, and the bulk layer 4 is formed on the lower layer side of the hologram guide layer 62. Further, a substrate 5 is formed on the lower layer side of the bulk layer 4.

FIG. 13 is a diagram for explaining an example of a manufacturing method of the bulk type recording medium 60 shown in FIG.
First, in manufacturing the bulk type recording medium 60, a master 63 as shown in FIG. The master 63 is necessary for transferring the concavo-convex cross-sectional shape for generating the hologram guide layer 62 that can obtain the same diffraction action as the hologram guide layer 3 described above.

  At this time, the concavo-convex shape for obtaining the same diffractive action as that of the hologram guide layer 3 can be obtained by a computer calculation as a so-called computer generated hologram (CGH). The master 63 is formed by forming the concavo-convex shape thus obtained by calculation by photolithography.

Then, using this master 63, the cover layer 61 to which the uneven shape is transferred is generated. As shown in FIG. 13B, the cover layer 61 is generated by using a cover layer material 61 ′ as a material for generating the cover layer 61 and transferring the uneven shape by, for example, injection molding. At this time, as the cover layer generating material 61 ′, for example, a resin such as polycarbonate or acrylic is used.
By such a generation process, a cover layer 61 as shown in FIG. 13C is obtained.

  For the generated cover layer 61, as shown in FIG. 13D, a reflection film 62 is formed on the uneven transfer surface side by, for example, sputtering or vapor deposition. Thereby, the hologram guide layer 62 is formed.

Bulk layer material 4 ′ is applied to hologram guide layer 62 formed in this manner as shown in FIG. 13E to form bulk layer 4.
In this case, as the bulk layer material 4 ′, for example, an ultraviolet curable resin is used, and after applying the bulk layer material 4 ′ as described above, a curing treatment by ultraviolet irradiation is performed, so that the lower layer side of the hologram guide layer 62 The bulk layer 4 is formed.
Although not shown, the substrate 5 is formed on the lower layer side of the bulk layer 4 formed in this manner by bonding or the like, and the bulk type recording medium 60 shown in FIG. 12 is generated.

In the above description, the cover layer 61 is generated directly from the master 63. However, in order to improve manufacturing efficiency, a plurality of stampers having the same shape as the master 63 shown in FIG. Of course, it is also possible to produce the cover layer 61 using these stampers. At this time, as the master for generating the stamper, one shown in FIG. 13A and one in which the concave-convex cross-sectional pattern is inverted are generated.

<5. Modification>

Although the embodiments of the present invention have been described above, the present invention should not be limited to the specific examples described above.
For example, in the above description, a hologram guide formed by forming interference fringes on a hologram recording material such as the hologram guide layer 3 provided in the bulk type recording medium (1 or 1 ′) of the first to third embodiments. The master hologram guide layer Hm to be the master of the layer is illustrated as being generated using the master creating multilayer structure 4i as shown in FIG. 3, but the method for generating the master hologram guide layer Hm is shown in FIG. It should not be limited to what has been described in, and for example, the following method may be used.

FIG. 14 is a diagram for explaining another generation method of the master hologram guide layer Hm.
In this method, the object light described in FIG. 3 is reproduced by modulating the laser light by the spatial light modulator SLM in the drawing. In this case, as the spatial light modulator SLM, a transmissive type including a transmissive liquid crystal element is used. For example, a reflective type including a reflective liquid crystal element or DMD (Digital Micromirror Device: registered trademark) is used. Can also be used.

In this case, when forming interference fringes for each information recording layer position L on the master hologram guide layer material Hm ′, object light is transmitted through the objective lens OL-r that irradiates reference light and the spatial light modulator SLM. As with the case of FIG. 3 above, the objective lens OL-b that irradiates is controlled so that the reference light and the object light are successively focused at individual positions corresponding to the respective information recording layer positions L.
At the same time, by sequentially changing the modulation pattern (spatial light modulation pattern) in the spatial light modulator SLM to a pattern corresponding to each information recording layer position L, each information is stored in the master hologram guide layer material Hm ′. Interference fringes are formed for each recording layer position L.

  Here, the modulation pattern for each information recording layer position L to be sequentially set by the spatial light modulator SLM can be obtained in advance as the above-mentioned CGH by calculation. Specifically, it can be obtained by inversely calculating the luminous flux of the reflected light from the virtual reflecting surface corresponding to each information recording layer position L.

  For confirmation, when forming the interference fringes corresponding to one information recording layer position L, the master hologram guide layer material Hm ′ is translated in the same manner as the method described in FIG. Interference fringes are formed on the entire surface of the master hologram guide layer material Hm ′ (or the entire surface of a necessary region).

  Here, in order to generate the hologram guide layer 3 in which interference fringes are formed on the hologram recording material, including the method of generating object light by the spatial light modulator SLM as described in FIG. It is not always necessary to create the layer Hm. That is, interference fringes for each information recording layer position L can be formed directly on the hologram guide layer material 3 ′ by the method shown in FIGS. 3 and 14.

In the description so far, the case where the bulk layer (recording layer) 4 and the hologram guide layer 3 are formed separately is exemplified. However, as shown in FIG. It is also possible to make a bulk type recording medium 70 in which the recording layer and the recording layer are integrated.
As shown in the figure, in this bulk type recording medium 70, a hologram guide layer / recording layer 71 is formed on the lower layer side of the cover layer 2, and the substrate 5 is further formed on the lower layer side thereof. The hologram guide layer / recording layer 71 is made of a hologram recording material.

The hologram guide layer / recording layer 71 may be considered to have the thickness of the hologram guide layer 3 equal to the thickness of the hologram guide layer 3 + the bulk layer 4.
Here, in this case, each information recording layer position L is set in the hologram guide layer / recording layer 71. That is, in this case, an in-focus image is obtained on the light receiving surface when the focal point of the recording / reproducing laser beam coincides with each information recording layer position L set in the hologram guide layer / recording layer 71 in this way. Thus, interference fringes may be formed on the hologram guide layer / recording layer 71 (or its master).
As a result, as shown in FIG. 15B, when light irradiation is performed through the objective lens so that a certain information recording layer position L is in focus, a focused image is formed on the light receiving surface and An image as if the virtual track Vtr_l is formed can be obtained.

  Here, it has been confirmed that a void (empty envelope) is also formed on the hologram recording material by condensing recording / reproducing laser light with a certain power or more. Therefore, as described above, the hologram guide layer can also serve as the recording layer.

  Further, in the description so far, the case where the number of information recording layer positions L set in the recording layer is set to 5 is exemplified, but the number of information recording layer positions L set can be increased or decreased. .

In the above description, in the embodiment in which the servo laser beam is irradiated together with the recording / reproducing laser beam, the wavelength of the recording / reproducing laser beam = about 405 nm and the wavelength of the servo laser beam = about 640 nm. Although illustrated, from the viewpoint of selectively diffracting only the servo laser beam in the hologram guide layer, the wavelength difference of the recording / playback laser beam with respect to the servo laser beam is at least the Bragg diffraction condition in the hologram guide layer. It is sufficient that a difference that does not satisfy is given. For example, specifically, a difference of about 10 nm or more may be given.
However, in practice, it is very difficult for the dichroic prism 16 provided on the apparatus side to sort out light having a very close wavelength difference such as about 10 nm, for example. Even if it can be realized, it is very high. Cost. Therefore, in practice, it is desirable that the wavelength difference between the recording / reproducing laser beam and the servo laser beam be sufficiently large (for example, 100 nm or more).

  Further, in the above description, the case where the present invention is applied to a recording / reproducing apparatus that performs both mark recording on the recording layer and reproduction of the recording mark is exemplified. However, the present invention includes only mark recording on the recording layer. The present invention can also be suitably applied to a recording device (recording-only device) that performs recording and a playback device (playback-only device) that only plays back recorded marks.

  1, 1 ', 60, 70 Bulk type recording medium, 2, 61 cover layer, 3 hologram guide layer, L1-L5 information recording layer position, OL-r, OL-b, 17 objective lens, Hm' master hologram guide layer Materials, 4i Multi-layer structure for creating a master, 3 ′ hologram guide layer material, Hm master hologram guide layer, 10, 40, 50 recording / reproducing device, OP1, OP2, OP3 optical pickup, 11 recording / reproducing laser, 12,22 collimator Lens, 13, 23 Polarizing beam splitter, 14 Mirror, 15, 24 1/4 wavelength plate, 16 Dichroic prism, 17 Objective lens, 18 Biaxial actuator, 19, 25 Condensing lens, 20 Light receiving unit for recording / reproducing light, 26 , 41 Cylindrical lens, 27 Light receiving part for servo light, 28, 42 Recording processing part, 29, 43 Signal for recording / reproducing light Generation circuit, 30 reproduction processing unit, 31 servo light signal generation circuit, 32 position information detection unit, 33,52 servo circuit, 34 focus driver, 35 tracking driver, 36,47,53 controller, 44 address detection unit, 45 recording Re-light servo circuit, 46 servo light servo circuit, 51 signal generation circuit, 62 reflective film (hologram guide layer), 63 master, 71 hologram guide layer / recording layer

Claims (19)

A bulk type optical recording medium in which mark recording is performed on a predetermined layer position where a reflective film is not formed,
An image similar to the image obtained on the light receiving surface when a reflection film is formed at the predetermined layer position when light irradiated so that the focal point coincides with the predetermined layer position. An optical recording medium comprising a diffraction layer configured to output diffracted light that can be formed on the light receiving surface. A bulk-shaped recording layer that does not have a reflective film and that performs mark recording at a predetermined layer position is provided separately from the diffraction layer, and the predetermined layer position is set in the bulk layer. The optical recording medium according to claim 1. A plurality of the layer positions are set in the recording layer,
The diffraction layer is
When each of the plurality of layer positions set in the recording layer has a reflection film formed on the one layer position when the irradiated light is incident so that the focal point coincides with the one layer position The optical recording medium according to claim 2, wherein the optical recording medium is configured to respectively output diffracted light capable of forming an image similar to an image obtained on the light receiving surface on the light receiving surface. The diffraction layer is
When the irradiated light is incident so that the focal point coincides with the predetermined layer position in the recording layer and the focal point is positioned at a predetermined position in the recording surface direction, the track is moved to the predetermined layer position. A diffracted light that can form on the light receiving surface an image similar to an image obtained on the light receiving surface when the reflective film having the surface is formed and the focal point traces on the track. The optical recording medium according to claim 2.   The optical recording medium according to claim 2, wherein the diffraction layer is formed by forming interference fringes on a hologram recording material.   The optical recording medium according to claim 2, wherein the diffraction layer is formed of a reflective film having a concavo-convex cross-sectional shape.   The optical recording medium according to claim 2, wherein the recording layer is made of a resin material. The optical recording medium according to claim 1, wherein the predetermined layer position is set in the diffraction layer, and the diffraction layer is also used as a layer for recording the mark. A method of manufacturing a bulk type optical recording medium in which mark recording is performed on a predetermined layer position where a reflective film is not formed,
An image similar to the image obtained on the light receiving surface when a reflection film is formed at the predetermined layer position when light irradiated so that the focal point coincides with the predetermined layer position. A method for producing an optical recording medium comprising at least a diffraction layer generation step for generating a diffraction layer that outputs diffracted light that can be formed on the light receiving surface. In the diffraction layer generation step,
A master diffraction layer is generated by irradiating object light and reference light from opposite directions to the hologram recording material to form interference fringes, and then formed on the other hologram recording material on the master diffraction layer The method for manufacturing an optical recording medium according to claim 9, wherein the diffraction layer is generated by transferring the interference fringes formed by irradiation with parallel light. The optical recording medium is
The diffraction layer generated by the diffraction layer generation step, and a bulk-shaped recording layer that does not have a reflective film and a mark recording is performed on a predetermined layer position,
In the diffraction layer generation step,
While producing a master creating structure in which a reflective film is formed for a layer position that is the same as the predetermined layer position set in the recording layer,
The hologram recording material is disposed on the master producing structure so that the hologram recording material has the same positional relationship as the positional relationship between the recording layer and the diffraction layer in the optical recording medium. The master diffraction layer is generated by irradiating the reflection film with reference light focused from the upper layer side and object light focused from the lower layer side to form interference fringes on the hologram recording material. 10. A method for producing an optical recording medium according to 10. A plurality of layer positions are set in the recording layer,
In the diffraction layer generation step,
As the master creation structure, a structure in which a reflective film is formed for each layer position that is the same as each layer position set in the recording layer is generated, and
In the state where the hologram recording material is arranged so as to have the same positional relationship as the positional relationship between the recording layer and the diffraction layer in the optical recording medium with respect to the generated master preparation structure, the object light and the reference The master diffraction layer is generated by forming an interference fringe on the hologram recording material by irradiating light so as to sequentially focus each of the reflective films formed on the master-producing structure. 11. A method for producing an optical recording medium according to 11. In the diffraction layer generation step,
As the master creation structure, a structure in which a reflective film having a track is formed with respect to a layer position that is the same as a predetermined layer position set in the recording layer is generated.
The hologram recording material is arranged on the generated master creation structure so that the hologram recording material has the same positional relationship as the positional relationship between the recording layer and the diffraction layer in the optical recording medium. The master diffraction is formed by irradiating the reference beam with the respective focal points on the reflection film and following the tracks formed on the reflection film to form interference fringes on the hologram recording material. The method for producing an optical recording medium according to claim 11, wherein a layer is generated. In the diffraction layer generation step,
The method of manufacturing an optical recording medium according to claim 10, wherein post curing is performed on the other hologram recording medium to which the interference fringes are transferred. In the diffraction layer generation step,
11. The master diffraction layer is generated by irradiating a hologram recording material with reference light and object light modulated via a spatial light modulator from opposite directions to form interference fringes. 2. A method for producing an optical recording medium according to 1. In the diffraction layer generation step,
Based on the master having a concavo-convex cross-sectional shape calculated as a computer-generated hologram, while generating a concavo-convex transfer member that transferred the concavo-convex cross-sectional shape,
The method for manufacturing an optical recording medium according to claim 9, wherein the diffraction layer is generated by forming a reflective film on the transfer surface having the uneven cross-sectional shape of the uneven transfer member. A bulk type optical recording medium in which mark recording is performed at a predetermined layer position where no reflective film is formed, and light irradiated so that the focal point coincides with the predetermined layer position is incident When the reflective film is formed at the predetermined layer position, it is configured to output diffracted light that can form an image similar to the image obtained on the light receiving surface on the light receiving surface. For optical recording media equipped with a diffraction layer
Light is irradiated through the objective lens, and the predetermined layer position is targeted based on a focus error signal obtained by receiving diffracted light from the diffraction layer obtained in response to the light irradiation on the light receiving surface. Servo control method for performing focus servo control of the objective lens. In the optical recording medium,
A plurality of layer positions are set as predetermined layer positions where the mark recording is performed,
The diffraction layer is
For each of the plurality of layer positions set on the optical recording medium, a reflection film is formed at the one layer position when the irradiated light is incident so that the focal point coincides with the one layer position. In this case, the diffracted light that can form an image similar to the image obtained on the light receiving surface is formed on the light receiving surface.
The servo control method according to claim 17, wherein focus servo pull-in to a desired layer position is performed based on an S-shaped waveform of the focus error signal obtained when the objective lens is driven in a focus direction. The diffraction layer is
When the light irradiated so that the focal point coincides with the predetermined layer position and the focal point is located at a predetermined position in the recording surface direction, a reflective film having a track at the predetermined layer position is formed. When the focal point is traced on the track, it is configured to output diffracted light that can form an image similar to an image obtained on the light receiving surface on the light receiving surface. And
The servo control method according to claim 17, wherein tracking servo control of the objective lens is performed based on a tracking error signal obtained by receiving diffracted light from the diffraction layer on the light receiving surface.

Images