JP2010102062A - Light irradiation device and light irradiation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To require only one light source in a hologram recording and reproducing system, for example, when irradiation with position control light having a different wavelength from that of recording and reproducing light is necessary for controlling a recording and reproducing position of a hologram. <P>SOLUTION: Two kinds of beams at different wavelengths are obtained by partially converting wavelengths in the light emitting from a single light source. Thereby, only one light source is enough to be provided when beams in different wavelengths are required for irradiation, for example, as recording and reproducing light and position control light. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a light irradiation apparatus for performing light irradiation on a hologram recording medium and a method thereof.

JP 2007-79438 A

For example, as disclosed in Patent Document 1, a hologram recording / reproducing system that performs data recording by forming a hologram is known. In this hologram recording / reproducing system, at the time of recording, a signal light that has been subjected to spatial light intensity modulation (light intensity modulation) according to the recording data and a reference light that has been given a predetermined light intensity pattern are generated, By irradiating the hologram recording medium with these, a hologram is formed on the recording medium to perform data recording.
At the time of reproduction, the reference light is irradiated to the recording medium. In this way, the hologram formed in response to the irradiation of the signal light and the reference light at the time of recording is recorded by being irradiated with the same reference light (having the same intensity pattern as at the time of recording) as at the time of recording. Diffracted light corresponding to the received signal light component is obtained. That is, a reproduced image (reproduced signal light) corresponding to the recorded data is thereby obtained. The reproduced image obtained in this manner is detected by an image sensor such as a CCD (Charge Coupled Device) sensor or a CMOS (Complementary Metal Oxide Semiconductor) sensor, and the recorded data is reproduced.

FIGS. 8 and 9 are diagrams for explaining the hologram recording / reproducing method. FIG. 8 schematically shows the recording method, and FIG. 9 schematically shows the reproducing method.
8 and 9 show a recording / reproducing method in the case where a so-called coaxial method in which recording is performed by arranging the signal light and the reference light on the same optical axis. Moreover, in these figures, the case where the reflection type hologram recording medium 100 provided with a reflecting film is used is illustrated.

  First, as shown in FIGS. 8 and 9, in the hologram recording / reproducing system, an SLM (spatial light modulator) 101 is used to generate signal light and reference light during recording and reference light during reproduction. Provided. The SLM 101 includes an intensity modulator that performs light intensity modulation on incident light in units of pixels. The intensity modulator can be constituted by a liquid crystal panel, for example.

  First, at the time of recording shown in FIG. 8, signal light given an intensity pattern according to recording data and reference light given a predetermined intensity pattern are generated by intensity modulation of the SLM 101. In the coaxial method, spatial light modulation is performed on incident light so that signal light and reference light are arranged on the same optical axis as shown in the figure. At this time, as shown in the figure, the signal light is generally arranged on the inner side and the reference light is arranged on the outer side.

  The signal light / reference light generated by the SLM 101 is applied to the hologram recording medium 100 via the objective lens 102. In this way, in response to the signal light / reference light being applied to the hologram recording medium 100 via the objective lens 102, the condensing surface of the objective lens 102 (Fourier transform action) is caused by the condensing action (Fourier transform action) of the lens. On the Fourier transform plane: frequency plane, an intensity pattern is generated by Fourier transforming the intensity distribution on the real image plane of the SLM 100 (in this case, the intensity distribution of the signal light and the intensity distribution of the reference light). Thus, the intensity pattern (intensity distribution) obtained on the light condensing surface is recorded on the hologram recording medium 100 as a refractive index distribution. That is, by this, the hologram recording medium 100 is formed with a hologram corresponding to the intensity distribution of the signal light generated by receiving the intensity modulation according to the recording data. Data recording for 100 is performed.

On the other hand, during reproduction, the SLM 101 generates reference light as shown in FIG. The intensity pattern of the reference light generated at the time of reproduction is the same as that at the time of recording (at least the pixel having the light intensity “1” at the time of recording is regarded as the light intensity “1”).
Then, the hologram recording medium 100 is irradiated with the reference light generated in this way via the objective lens 102.

As shown in FIG. 9B, the reference light having the same intensity pattern as that at the time of recording is irradiated onto the hologram recording medium 100 as shown in FIG. A reproduced image is output by diffraction.
In this case, the reproduced image is guided to the image sensor 103 as reflected light from the hologram recording medium 100 through the objective lens 100 as shown.

Strictly speaking, depending on the irradiation of the reference light during reproduction, not only the reproduced image of the recorded signal light but also the reproduced image of the recorded reference light can be obtained. For confirmation, the reproduced image for the recorded signal light is obtained in the light beam region of the signal light irradiated during recording (in this case, the inner circular region), and the reproduced image for the recorded reference light is reproduced. The image is obtained in the light beam region of the reference light (in this case, the outer ring-shaped region).
However, the reproduced image of the reference light does not reflect the recording data, and its detection is not particularly necessary. In addition, since the reproduction image of the reference light is obtained in the light beam region of the reference light as described above, it cannot be distinguished from the irradiated reference light. From these points, in the coaxial system, there is no problem in treating the recorded reference light as being absent.

  The image sensor 103 receives the reproduced image derived as described above in units of pixels, and obtains an electric signal corresponding to the amount of received light for each pixel, thereby obtaining a detection image for the reproduced image. Thus, the image signal detected by the image sensor 103 becomes a read signal for the recorded data.

  For confirmation, as can be understood from the description of FIGS. 8 and 9, in the hologram recording / reproducing method, recording data is recorded / reproduced in units of signal light. That is, in the hologram recording / reproducing system, one hologram (called a hologram page) formed by one irradiation of signal light and reference light is the minimum unit of recording / reproducing.

Here, consider that data is sequentially recorded on the hologram recording medium 100 in units of the hologram page.
In an optical disc system such as a conventional CD (Compact Disc) or DVD (Digital Versatile Disc), a recording medium is formed in a disc shape (disk shape), and data is recorded by forming marks while rotating the recording medium. Have been to do. At this time, a spiral or concentric guide groove (track) is formed on the recording medium, and marks are formed while controlling the beam spot position so as to trace on the track. Data is recorded at a predetermined position.

  In accordance with this, also in the hologram recording / reproducing system, a spiral or concentric track is formed on the disc-shaped hologram recording medium 100, and the hologram recording medium 100 to be rotated is sequentially irradiated with signal light and reference light. It is considered to adopt a method of forming a hologram page along a track by forming a hologram.

  In this way, when a method of forming a hologram page at a position along the track is adopted, a recording servo / recording position such as a tracking servo for tracing the beam spot on the track and access control to a predetermined address is used. Control needs to be done.

In the conventional hologram recording / reproducing system, when controlling such a recording / reproducing position, a dedicated laser beam is separately irradiated. That is, laser light for recording / reproducing a hologram (laser light for irradiating signal light / reference light: laser light for recording / reproducing) and laser light for controlling the recording / reproducing position of the hologram ( And a method of separately irradiating position control laser light).
In order to correspond to the method of separately irradiating the position control laser light in this way, the hologram recording medium 100 is actually provided with a structure as shown in FIG.

As shown in FIG. 10, the hologram recording medium 100 includes a recording layer 107 on which hologram recording is performed, and position control information in which address information and the like for position control are recorded by an uneven sectional structure on the substrate 111. The recording layer is formed separately.
Specifically, on the hologram recording medium 100, an antireflection film 105, a cover layer 106, a recording layer 107, a reflection film 108, an intermediate layer 109, a reflection film 110, and a substrate 111 are formed in order from the upper layer.
The antireflection film 105 is formed by applying an AR (Anti Refrection) coating.

The cover layer 106 is made of, for example, a plastic substrate or a glass plate, and is provided for protecting the recording layer 107.
For the recording layer 107, a material such as a photopolymer, which can record information by changing the refractive index according to the intensity distribution of the irradiation light, is selected. Is recorded / reproduced.

  The reflection film 108 is irradiated with reference light from the recording / reproducing laser beam during reproduction, and when a reproduced image corresponding to the hologram recorded in the recording layer 107 is obtained, this is reflected as reflected light on the apparatus side. It is provided to return to

The substrate 111 and the reflective film 110 are provided for controlling the recording / reproducing position.
On the substrate 111, tracks for guiding the recording / reproducing position of the hologram in the recording layer 107 are formed in a spiral shape or a concentric shape. For example, a track is formed by recording information such as address information by a pit row.
A reflective film 110 is formed on the surface (front surface) of the substrate 111 on which the track is formed, for example, by sputtering or vapor deposition. The intermediate layer 109 formed between the reflective film 110 and the above-described reflective film 108 is an adhesive material such as a resin.

Here, with respect to the hologram recording medium 100 having the above-described cross-sectional structure, in order to appropriately perform position control based on the reflected light of the position control laser light, the position control laser light is The reflection film 110 having the uneven cross-sectional shape must be reached. In other words, from this point, the laser light for position control must pass through the reflective film 108 formed above the reflective film 110.
On the other hand, the reflective film 108 needs to reflect a laser beam for recording / reproduction so that a reproduced image corresponding to the hologram recorded on the recording layer 107 is returned to the apparatus side as reflected light.

Considering this point, in the conventional hologram recording / reproducing system, a laser beam having a wavelength different from that of the hologram recording / reproducing laser beam is used as the position controlling laser beam. For example, a blue-violet laser beam having a wavelength λ = 405 nm is used as a hologram recording / reproducing laser beam, and a red laser beam having a wavelength λ = 650 nm is used as a position control laser beam. Yes.
In addition, as a reflection film 108 formed between the recording layer 107 and the reflection film 110 on which the position control information is recorded, the recording / reproducing blue-violet laser light is reflected, and the position control red color is reflected. A reflective film having wavelength selectivity that transmits laser light is used.
With such a configuration, at the time of recording / reproducing, the laser light for position control reaches the reflection film 110 and the reflected light information for position control is properly detected on the apparatus side, and the recording layer The reproduction image of the hologram recorded in 107 can be properly detected on the apparatus side.

FIG. 11 is a diagram schematically showing the configuration of a conventional recording / reproducing apparatus that performs recording / reproduction corresponding to the hologram recording medium 100 having the structure described above (mainly only for the optical system).
First, the recording / reproducing apparatus includes a first laser 115, a collimator lens 116, an SLM 101, a polarization beam splitter 117, a quarter wavelength plate as an optical system for irradiating signal light and reference light for hologram recording and reproduction. 119, an objective lens 102, and an image sensor 103 are provided.
The first laser 115 outputs, for example, the above-described blue-violet laser light having a wavelength λ = 405 nm as laser light for hologram recording / reproduction. The laser beam emitted from the first laser 115 enters the SLM 101 via the collimator lens 116.
As described above, the SLM 101 performs spatial light modulation on the incident light, thereby generating signal light and reference light during recording and generating reference light during reproduction.

The recording / reproducing laser beam subjected to spatial light modulation by the SLM 101 is transmitted through the polarization beam splitter 117 and then transmitted through a dichroic mirror 118 described later. Then, the recording / reproducing laser beam transmitted through the dichroic mirror 118 passes through the quarter-wave plate 119 and is then focused on the hologram recording medium 100 (recording layer 107) by the objective lens 102. .
Thereby, at the time of recording, a hologram reflecting the signal light is formed on the recording layer 107 and data recording is performed.

At the time of reproduction, a reproduction image corresponding to the signal light recorded on the recording layer 107 is obtained as reflected light from the reflective film 108 by irradiation of the reference light, and the reproduced image as the reflected light is the objective lens 102 → 1. / 4 wavelength plate 119 → enters the polarization beam splitter 117 via the dichroic mirror 118. The polarization beam splitter 117 reflects the reproduced image obtained as the reflected light from the hologram recording medium 100 in this way and guides it to the image sensor 103 side.
In this way, during reproduction, the reproduced image from the hologram recording medium 100 is detected by the image sensor 103.

  In this case, the recording / reproducing apparatus is also provided with an optical system for irradiating position control laser light and detecting reflected light of the position control laser light. Specifically, the second laser 120, the collimator lens 121, the polarization beam splitter 122, the dichroic mirror 118, and the photodetector 123 are included.

The second laser 120 outputs, for example, the above-described red laser light having the wavelength λ = 650 nm as the position control laser light. The emitted light from the second laser 120 enters the dichroic mirror 118 via the collimator lens 121 → the polarization beam splitter 122.
The dichroic mirror 118 is configured to have wavelength selectivity such that the recording / reproducing laser beam from the first laser 115 is transmitted and the position controlling laser beam from the second laser 120 is reflected. Accordingly, the position control laser light transmitted through the polarization beam splitter 122 is reflected by the dichroic mirror 118 and guided to the quarter wavelength plate 119 side.
The laser light for position control via the quarter wavelength plate 119 is irradiated so as to be condensed on the reflection film 110 formed on the hologram recording medium 100 by the objective lens 102.

For confirmation, by providing the dichroic mirror 118 as described above, the laser beam for position control and the laser beam for recording / reproducing are synthesized on the same optical axis, and this synthesis is performed. The hologram recording medium 100 is irradiated with light through a common objective lens 102.
In other words, the beam spot of the laser beam for position control and the beam spot for recording / reproducing are formed at the same position in the in-plane direction as a result. By performing the position control operation based on the position control laser beam, the hologram recording / reproducing position is controlled to be positioned on the track.

  As described above, the laser light for position control is irradiated onto the reflection film 110, so that reflected light corresponding to the recording information on the reflection film 110 is obtained. The light is guided to the polarization beam splitter 122 via the plate 119 → the dichroic mirror 118. The polarization beam splitter 122 reflects the reflected light of the position control laser light obtained through the dichroic mirror 118 in this way, and guides it to the photodetector 123.

  The photodetector 123 receives the reflected light of the position control laser light guided as described above, converts it into an electrical signal, and supplies it to the matrix circuit 124.

  The matrix circuit 124 includes a matrix calculation / amplification circuit for output signals from a plurality of light receiving elements as the photodetector 123, and generates necessary signals by matrix calculation processing. Specifically, a signal (reproduction signal RF) corresponding to a reproduction signal for the pit row formed on the reflective film 110, a focus error signal FE for servo control, a tracking error signal TE, and the like are generated.

Although not shown, the recording / reproducing apparatus is provided with an address detection circuit and a clock generation circuit for detecting address information and generating a clock based on the reproduction signal RF.
Further, a servo circuit is provided that controls the position of the laser spot for position control by controlling the position of the objective lens 102 and the like based on the address information and the tracking error signal TE. By controlling the beam spot position of the laser beam for position control by this servo circuit, the beam spot position of the laser beam for hologram recording / reproducing is moved to a required address, followed by a track, etc. You can do that. That is, this controls the recording / reproducing position of the hologram.

As described above, in the conventional hologram recording / reproducing system, position control is performed by irradiating a laser beam for hologram recording / reproducing and a separate laser beam having a wavelength different from that.
As described above, if the separate laser beams having different wavelengths are irradiated, if the return light of the recording / reproducing light is commonly used for position control as in the conventional optical disc system, the position control information is applied to the reproduced image of the hologram. This is because noise may be superimposed as noise and the reproduction performance of the hologram may be significantly deteriorated. That is, in order to avoid such a situation, it is necessary to separately irradiate the light used for recording / reproduction and the light for position control, but at this time, there is nothing about the wavelengths of the position control light and the recording / reproduction light. If this is not taken into account, the hologram recording material (recording layer 107) is also exposed to position control light, which may result in data destruction.

  However, the conventional configuration shown in FIG. 11 has a problem in that the first laser 110 and the second laser 120 are provided separately. That is, according to such a conventional technique, the number of light sources to be provided in the recording / reproducing apparatus becomes two.

Therefore, in the present invention, in view of the above problems, the light irradiation device is configured as follows.
That is, a single light source for irradiating light to a hologram recording medium on which information recording is performed by causing a change in refractive index according to the intensity distribution of irradiation light is provided.
In addition, a wavelength conversion unit that performs wavelength conversion by inputting part of the light from the light source is provided.
And a light irradiation unit that irradiates the hologram recording medium with light emitted from the light source and passed through the wavelength conversion unit and light emitted from the light source and not passed through the wavelength conversion unit. .

  As described above, in the present invention, a part of the light emitted from a single light source is wavelength-converted to obtain two types of light having different wavelengths.

  As described above, according to the present invention, two types of light having different wavelengths can be obtained by performing wavelength conversion on light from a single light source. Thereby, when it is necessary to irradiate light having different wavelengths for the recording / reproducing light and the position control light, it is possible to provide only one light source.

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

<First Embodiment>
[Configuration of optical system]
[Specific example of configuration for position control (example of overall configuration of recording / reproducing apparatus)]
<Second Embodiment>
<Modification>

<First Embodiment>
[Configuration of optical system]

FIG. 1 is a diagram mainly illustrating the configuration of the optical system as a diagram for explaining the internal configuration of the light irradiation apparatus according to the first embodiment of the present invention.
Here, in the present embodiment, a case where the light irradiation apparatus of the present invention is applied to a recording / reproducing apparatus that performs recording / reproduction on a hologram recording medium is illustrated. The recording / reproducing apparatus of this embodiment (referred to as recording / reproducing apparatus 30) employs a so-called coaxial system as a hologram recording / reproducing system. That is, the signal light and the reference light are arranged on the same axis, and the hologram recording medium set at a predetermined position is irradiated with the signal light to record data by forming a hologram. By irradiating the recording medium HM, a reproduced image (reproduced signal light) of a hologram is obtained, and the recorded data is reproduced.
The overall configuration of the recording / reproducing apparatus 30 will be described later.

Here, the hologram recording medium HM to be recorded and reproduced by the recording / reproducing apparatus 30 of the present embodiment is a reflection type hologram recording medium, similar to the hologram recording medium 100 described in FIG. The cross-sectional structure is the same as that of the hologram recording medium 100.
For confirmation, the hologram recording medium HM is also formed with an antireflection film 105, a cover layer 106, a recording layer 107, a reflection film 108, an intermediate layer 109, a reflection film 110, and a substrate 111 in order from the upper layer. (See FIG. 10).
The “upper layer” and “lower layer” as used herein refer to the surface on which light for recording / reproduction is incident as the upper surface, the surface opposite to the upper surface as the lower surface, the upper surface side as the upper layer, and the lower surface side as the lower surface. The lower layer.

The antireflection film 105 is formed by applying an AR (Anti Refrection) coating.
The cover layer 106 is made of, for example, a plastic substrate or a glass plate, and is provided for protecting the recording layer 107.
For the recording layer 107, a material capable of recording information by changing the refractive index according to the intensity distribution of irradiation light, such as a photopolymer, is selected as the material, and a hologram using a recording / reproducing laser beam described later. Is recorded / reproduced.

The reflection film 108 is irradiated with reference light from the recording / reproducing laser beam during reproduction, and when a reproduced image corresponding to the hologram recorded in the recording layer 107 is obtained, this is reflected as reflected light on the apparatus side. It is provided to return to
Here, also in this embodiment, in order to prevent the recording layer 107 from being exposed to data destruction due to the position control light irradiation, the reflective film 108 has wavelength selectivity. Configure.
As will be described later, also in this embodiment, a blue-violet laser beam having a wavelength of λ = 405 nm is irradiated as a laser beam for hologram recording / reproduction, and a wavelength λ = 650 nm is used as a laser beam for position control, for example. The red laser beam is irradiated. Correspondingly, a reflective film having wavelength selectivity is used for the reflective film 108 such that the recording / reproducing blue-violet laser light is reflected and the red laser light for position control is transmitted.

The substrate 111 and the reflective film 110 are provided for controlling the hologram recording / reproducing position.
A track for guiding the hologram recording / reproducing position in the recording layer 107 is formed on the substrate 111 spirally or concentrically. For example, a track is formed by recording information such as address information by a pit row.
A reflective film 110 is formed on the surface (front surface) of the substrate 111 on which the track is formed, for example, by sputtering or vapor deposition. For confirmation, it is sufficient that the reflective film 110 is configured to reflect position control light, and there is no need to have wavelength selectivity.
The intermediate layer 109 formed between the reflective film 110 and the reflective film 108 described above is made of an adhesive material such as a resin.

Returning to FIG.
In the recording / reproducing apparatus 30, the hologram recording medium HM is held so as to be rotationally driven by a spindle motor (SPM) 37 not shown in the figure.
The optical unit UN in the drawing is configured to irradiate the hologram recording medium HM thus held with laser light for recording / reproduction and laser light for position control.

In the optical unit UN shown in FIG. 1, a laser diode (LD) 1 is a laser diode with an external resonator, for example, and outputs so-called blue-violet laser light having a wavelength of about λ = 405 nm.
The laser light emitted from the laser diode 1 is converted into parallel light via a collimator lens 2 and then part of the laser light via a beam splitter (non-polarized beam splitter) 3 to be described later is subjected to SLM (spatial light modulation). ).

The SLM 4 performs spatial light intensity modulation on the incident light in units of pixels. In this case, the SLM 4 is a transmissive type, and specifically, a transmissive liquid crystal panel is employed.
As shown in the figure, the SLM 4 controls on / off of each pixel on the basis of a drive signal D-slm supplied from a modulation control unit 31 provided outside the optical unit UN. Intensity modulation is performed on a pixel basis.

Here, in this embodiment, a coaxial method is adopted as a hologram recording / reproducing method. When the coaxial method is adopted, in the SLM 4, in order to arrange the signal light and the reference light on the same optical axis, each area as shown in FIG. 2 is set.
As shown in FIG. 2, in the SLM 4, a circular area having a predetermined range including the center (coincident with the optical axis center) is set as the signal light area A2. An annular reference light area A1 is set outside the signal light area A2 with a gap area A3 therebetween.
By setting the signal light area A2 and the reference light area A1, the signal light and the reference light can be irradiated so as to be arranged on the same optical axis.
The gap area A3 is defined as a region for preventing the reference light generated in the reference light area A1 from leaking into the signal light area A2 and becoming noise with respect to the signal light.
For confirmation, since the pixel shape of the SLM 4 is rectangular, the signal light area A2 is not strictly circular. Similarly, the reference light area A1 and the gap area A3 are not strictly ring-shaped. In that sense, the signal light area A2 is a substantially circular area, and the reference light area A1 and the gap area A3 are also substantially ring-shaped areas.

In FIG. 1, a modulation control unit 31 performs drive control on the SLM 4 to generate signal light and reference light during recording and only reference light during reproduction.
Specifically, at the time of recording, the modulation control unit 31 sets the pixels of the signal light area A2 in the SLM 4 to an on / off pattern corresponding to the supplied recording data, and the pixels of the reference light area A1 are predetermined predetermined. A drive signal D-slm for turning on / off the pattern and turning off all other pixels is generated and supplied to the SLM 4. By intensity modulation by the SLM 4 based on the drive signal D-slm, signal light and reference light arranged so as to have the same center (optical axis) are obtained as light emitted from the SLM 4.
Further, at the time of reproduction, the modulation control unit 31 drives and controls the SLM 4 with a drive signal D-slm that turns the pixels in the reference light area A1 into the predetermined on / off pattern and turns off all other pixels. Thus, only the reference light is generated.

  At the time of recording, the modulation control unit 31 generates an on / off pattern in the signal light area for each predetermined unit of the input recording data string, and thereby generates data for each predetermined unit of the recording data string. It operates so that the stored signal light is sequentially generated. As a result, data is sequentially recorded on the hologram recording medium HM in units of hologram pages (data units that can be recorded by one-time interference between the signal light and the reference light).

  The light subjected to the spatial light modulation by the SLM 4 enters the polarization beam splitter 7 via the relay lens system by the relay lens 5 → the relay lens 6. For example, the polarization beam splitter 7 in this case is configured to transmit p-polarized light and reflect s-polarized light. Accordingly, only the p-polarized component of the laser light incident on the polarization beam splitter 7 is transmitted as described above.

  The laser light transmitted through the polarization beam splitter 7 is incident on the dichroic mirror 8. The dichroic mirror 8 transmits blue-violet laser light having a wavelength of about 405 nm guided by the optical path described above, and reflects red laser light having a wavelength of about 650 nm guided by wavelength conversion by a wavelength conversion unit 17 described later. Is configured to do. For this reason, the laser beam incident from the side of the polarization beam splitter 7 is transmitted through the dichroic mirror 8 and is held by the biaxial mechanism 11 after passing through the quarter-wave plate 9 as shown in the figure. The hologram recording medium HM is irradiated through the objective lens 10.

The biaxial mechanism 11 is configured so that the objective lens 10 is in contact with and separated from the hologram recording medium HM (focus direction) and in the radial direction of the hologram recording medium HM (direction orthogonal to the focus direction: tracking direction). Hold it displaceable. Further, a focus coil for driving the objective lens 10 in the focus direction and a tracking coil for driving in the tracking direction are provided.
These focus coil and tracking coil are driven by a focus drive signal FD and a tracking drive signal TD, which will be described later, thereby performing focus servo control, tracking servo control, and the like.

  Here, according to the optical path described above, the laser light that has undergone spatial light modulation by the SLM 4 is irradiated onto the hologram recording medium HM via the objective lens 10, but the recording by the SLM 4 described above is performed. Depending on the temporal spatial light modulation, signal light and reference light are generated. That is, at the time of recording, the signal light and the reference light are irradiated onto the hologram recording medium HM.

  In this way, when the hologram recording medium HM is irradiated with the signal light / reference light through the objective lens 10, the condensing surface of the objective lens 10 (Fourier transform action) is caused by the condensing action (Fourier transform action) of the lens. On the Fourier transform plane: frequency plane, an intensity pattern is generated by Fourier transforming the intensity distribution (the intensity distribution of the signal light and the intensity distribution of the reference light) on the real image plane of the SLM 4. The intensity pattern (intensity distribution) obtained on the condensing surface in this way is recorded as a refractive index distribution on the recording layer 107 of the hologram recording medium HM. That is, as a result, a hologram corresponding to the signal light to which the intensity pattern corresponding to the recording data is given is formed on the hologram recording medium HM, whereby data recording on the hologram recording medium HM is performed. Is called.

  Further, only the reference light is generated in the SLM 4 during reproduction. The reference light generated in this way is also applied to the hologram recording medium HM via the objective lens 10 through an optical path similar to the optical path during recording described above.

Here, as can be understood from the description of the drive control of the SLM 4 during reproduction described above, the reference light generated during reproduction has the same intensity pattern as during recording. In this way, in response to the reference light having the same intensity pattern as that at the time of recording being applied to the hologram recording medium HM via the objective lens 10, a reproduced image (reproduced image) of the signal light recorded on the hologram recording medium HM. Signal light) is output by diffraction.
In this case, the reproduced image is returned to the apparatus side as reflected light from the reflective film 108 in the hologram recording medium HM.

Strictly speaking, depending on the irradiation of the reference light during reproduction, not only the reproduced image of the recorded signal light but also the reproduced image of the recorded reference light can be obtained. A reproduced image of the recorded signal light is obtained in the light beam region of the signal light irradiated at the time of recording (that is, the light beam region of the signal light area A2), and the reproduced image of the recorded reference light is obtained from the reference light. It is obtained in the light ray region (light ray region of the reference light area A1).
However, the reproduced image of the reference light does not reflect the recorded data, and its detection is not particularly necessary. Also, since it is obtained in the light beam region of the reference light as described above, it can be distinguished from the irradiated reference light. It will not be connected. From these points, in the coaxial system, there is no problem in treating the recorded reference light as being absent.

The reproduced image obtained as the reflected light from the hologram recording medium HM as described above passes through the objective lens 10 → the quarter-wave plate 9 and then passes through the dichroic mirror 8 and is then guided to the polarization beam splitter 7. It is burned.
The reproduced image thus guided to the polarization beam splitter 7 is incident on the polarization beam splitter 7 as s-polarized light by the functions of the quarter-wave plate 9 and the reflection film 108 in the hologram recording medium HM. Specifically, if the quarter-wave plate 9 → the reflective film 108 is the forward path and the reflective film 108 → the quarter-wave plate 9 is the backward path, the forward path is p-polarized light → right-handed polarized light, and the backward path is counterclockwise circularly-polarized light → s. Conversion to polarized light is performed.

  The reconstructed image incident as s-polarized light is reflected by the polarization beam splitter 7 as described above, and is applied to the image sensor 15 via the relay lens system of the relay lens 12 → the mirror 13 → the relay lens 14 as shown in the figure. Be guided.

  The image sensor 15 is, for example, a CCD (Charge Coupled Device) sensor, a CMOS (Complementary Metal Oxide Semiconductor) sensor, or the like. To obtain an image signal. The image signal thus obtained reflects an on / off pattern (that is, a data pattern of “0” and “1”) given to the signal light at the time of recording. That is, the image signal detected by the image sensor 15 in this way corresponds to a read signal for data recorded on the hologram recording medium HM.

The image signal (detection result D-img) as the readout signal obtained by the image sensor 15 is supplied to the data reproducing unit 32 provided outside the optical unit UN as shown in the figure.
The data reproduction unit 32 performs data identification of “0” and “1” for each pixel value of the SLM 4 included in the image signal as the detection result D-img, and demodulation processing of the recording modulation code as necessary Etc. to reproduce the recorded data.

  With the configuration described so far, it is possible to realize a hologram recording / reproducing operation by irradiation of recording / reproducing light using the laser diode 1 as a light source.

  In addition to the configuration of the optical system for recording / reproducing holograms described above, the optical unit UN shown in FIG. 1 includes an optical system (position control optics) for controlling the recording / reproducing position of the hologram. As a system), a beam splitter 3, a mirror 16, a wavelength conversion unit 17, a mirror 18, a polarization beam splitter 19, a condensing lens 20, and a photodetector (PD) 21 in the figure are provided.

  In this position control optical system, the beam splitter 3 reflects a part of the laser light emitted from the laser diode 1 and passing through the collimator lens 2 and guides it to the mirror 16 as shown. The laser light reflected by the mirror 16 is guided to the wavelength conversion unit 17.

  The wavelength converter 17 converts the wavelength of the incident laser light and outputs laser light with different wavelengths. Specifically, in this case, laser light having a wavelength of about 405 nm as incident blue-violet laser light is converted into laser light having a wavelength of about 650 nm as red laser light and output.

FIG. 3 is a diagram illustrating an internal configuration example of the wavelength conversion unit 17.
First, the wavelength conversion part 17C is provided with the wavelength conversion material 17C. Depending on the material of the wavelength conversion material 17C, the wavelength of incident light can be converted to a required wavelength.
In this case, as the wavelength conversion material 17C, a material that converts blue-violet light incident on the wavelength conversion unit 17 into red light is selected. For example, in the field of organic EL (Erectro-Luminescence) displays and the like, phosphor materials that convert blue light into red light (long wavelength) are widely known. In this case, such a phosphor material is also used as the wavelength conversion unit 17C. Specifically, a phosphor thin film (close to a crystalline state) is used as the wavelength conversion material 17C.

Here, when only the wavelength conversion material 17C is used, the light emission is scattered in the crystal and the phases are not uniform. In order to obtain laser light (coherent light having a single wavelength and a uniform phase) as emitted light, it is most effective to use a phenomenon called oscillation.
In view of this point, a so-called Fabry-Perot resonator in which a total reflection mirror 17A and a partial reflection mirror 17B are arranged so as to face each other is used as the wavelength conversion unit 17 of the present embodiment. Specifically, a configuration in which the wavelength conversion material 17 is provided in the Fabry-Perot resonator is adopted. As is well known, in the Fabry-Perot resonator, the total reflection mirror 17A is provided on the incident side and the partial reflection mirror 17B is provided on the emission side.

  With the configuration including the Fabry-Perot resonator as shown in FIG. 3, a light feedback loop is formed for light emission (fluorescence) by the wavelength conversion material 17C, and the phase adjustment effect (coherent light generation effect) , And a light amplification effect. The light that has reached a predetermined energy due to the light amplification effect is transmitted through the partial reflection mirror 17B provided on the emission side, so that a laser beam converted to a required wavelength (in this case, about 650 nm) is output.

Here, in the present embodiment, a phosphor thin film is used as the wavelength conversion material 17C as described above. However, in consideration of the light amplification effect, the phosphor thin film has a thickness of about several microns. Use one.
Examples of the method for forming such a phosphor thin film include sputtering, sol-gel method, chemical vapor deposition method, and PLD (Pulse Laser Deposition) method. Among these, the PLD method has a relatively high deposition rate, the property that the composition of the thin film deposited on the substrate is close to the target composition, and the surface morphology and roughness of the film that affects the light emission luminance can be easily controlled. Have the merits. For confirmation, the PLD method is a film formation technique in which high-energy laser pulses are applied to the sintering target in the chamber, and particles such as emitted ions, clusters, and atoms are deposited on the opposing substrate. is there.

For example, by providing the wavelength conversion unit 17 having the structure as described above, blue-violet laser light having the laser diode 1 as a light source can be converted into red laser light as position control laser light.
In this case, the wavelength difference between the recording / reproducing laser beam and the position controlling laser beam is about 250 nm. By providing a sufficient wavelength difference in this way, the laser beam for position control is equivalent to almost no sensitivity to the recording layer 107 of the hologram recording medium HM.

Returning to FIG.
The laser light for position control generated by the wavelength converter 17 is reflected by the mirror 18 and enters the polarization beam splitter 19.
The polarizing beam splitter 19 is also configured to transmit p-polarized light and reflect s-polarized light. Therefore, only the p-polarized component of the position control laser light is transmitted through the polarizing beam splitter 19.

The laser light that has passed through the polarization beam splitter 19 enters the dichroic mirror 8.
As described above, the dichroic mirror 8 is configured to transmit the blue-violet laser beam and reflect the red laser beam. Therefore, as described above, the position-control laser beam incident from the polarization beam splitter 19 side. Is reflected by the dichroic mirror 8 and guided to the quarter-wave plate 9 as shown in the figure.
As described above, the position control laser beam guided to the ¼ wavelength plate 9 side is also irradiated to the hologram recording medium HM through the same path as that of the previous recording / reproducing laser beam.

As can be understood from the above description, the dichroic mirror 8 includes a recording / reproducing laser beam that does not pass through the wavelength converter 17 and a position control laser beam that is generated through the wavelength converter 17. And irradiating the hologram recording medium HM through the same objective lens 10. In addition, due to the wavelength selectivity, the hologram reproduction image also has a function of returning to the image sensor 15 side and the reflected light of the position control light reflecting the uneven shape on the substrate 111 to branch back to the photodetector 21 side. It has become.
In this case, depending on the dichroic mirror 8, the optical system is adjusted so that the laser light for position control and the laser light for recording / reproducing are superimposed on the same optical axis and guided to the quarter wavelength plate 9 side. Keep it. For example, in order to make the optical axes coincide with each other, the incident positions of the recording / reproducing laser beam and the position controlling laser beam with respect to the dichroic mirror 8 may be adjusted.

  Here, when the hologram recording medium HM is irradiated with the red laser light as the position control light as described above, the concavo-convex cross-sectional shape (pits) on the substrate 111 (on the reflection film 110) in the hologram recording medium HM. Reflected light reflecting the track TR) is obtained (position control information reflected light). Such position control information reflected light is also incident on the dichroic mirror 8 through the objective lens 10 → the quarter-wave plate 9 as in the case of the recording / reproducing laser light.

In the dichroic mirror 8, the incident position control information reflected light is reflected, and the reflected light is guided to the polarization beam splitter 19.
As described above, the position control information reflected light guided to the polarization beam splitter 19 also enters the polarization beam splitter 19 as s-polarized light by the action of the quarter-wave plate 9 and the reflection film 110. Therefore, the position control information reflected light is reflected by the polarization beam splitter 19 and irradiated so as to be condensed on the detection surface of the photodetector 21 via the condenser lens 20 as shown in the figure.

The photodetector 21 includes a plurality of light receiving elements, receives the position control information reflected light from the hologram recording medium HM irradiated through the condenser lens 20 as described above, and obtains an electric signal corresponding to the light reception result. That is, the reflected light information (reflected light signal) Dt reflecting the uneven cross-sectional shape formed on the substrate 111 is thereby detected.
Based on such reflected light information Dt, various position control relating to the hologram recording / reproducing position, such as focus servo control, tracking servo control, and access control to a predetermined address, can be performed.

Here, as can be understood from the above description, in the recording / reproducing apparatus 30 of the first embodiment, wavelength conversion is performed on the laser light obtained by spectrally dividing a part of the laser light emitted from the laser diode 1. By providing the wavelength conversion unit 17 that performs the above, position control laser light having a wavelength different from that of the hologram recording / reproducing laser light is generated separately.
With such a configuration, in the case where it is necessary to irradiate laser beams having different wavelengths when performing hologram recording / reproduction and position control thereof, the number of light sources can be only one.

[Specific example of configuration for position control (example of overall configuration of recording / reproducing apparatus)]

For confirmation, a specific configuration example for controlling the recording / reproducing position of the hologram based on the reflected light information Dt obtained by the photodetector 21 as described above will be described with reference to FIG. Keep it.

FIG. 4 is a diagram illustrating an example of the overall configuration of the recording / reproducing apparatus 30.
First, also in FIG. 4, the optical unit UN, the hologram recording medium HM, the modulation control unit 31, and the data reproduction unit 32 shown in FIG. 1 are shown. Since these have already been described, further description will be omitted.

Reflected light information (reflected light signal) Dt detected by the photodetector 21 provided in the optical unit UN is supplied to the matrix circuit 33 as shown.
The matrix circuit 33 includes a matrix calculation / amplification circuit for the output signals from the plurality of light receiving elements as the reflected light signal Dt from the photodetector 21, and generates necessary signals by matrix calculation processing.
For example, a signal (reproduction signal RF) corresponding to a reproduction signal for a pit row formed on the substrate 111 of the hologram recording medium HM, a focus error signal FE for servo control, a tracking error signal TE, and the like are generated.

  The reproduction signal RF output from the matrix circuit 33 is supplied to the address detection / clock generation circuit 34. The focus error signal FE and the tracking error signal TE are supplied to the servo circuit 35.

The address detection / clock generation circuit 34 detects address information based on the reproduction signal RF and performs a clock generation operation.
For example, as the clock generation operation, an operation for generating a reproduction clock by performing PLL processing based on the reproduction signal RF is performed.
The address information detected (reproduced) by the address detection / clock generation circuit 34 is supplied to the control unit 40. Although not shown, the clock information is supplied as an operation clock for each necessary unit.

  The spindle control circuit 36 performs rotation control of a spindle motor 37 that holds the hologram recording medium HM so as to be rotationally driven. As a rotation control method of the spindle motor 37 (rotation control of the hologram recording medium HM), for example, a CAV (Constant Angular Verlocity) method or a CLV (Constant Linear Verlocity) method can be employed.

  For confirmation, when the CLV method is adopted, the spindle control circuit 36 inputs information on the reproduction clock output from the address detection / clock generation circuit 34 described above as rotation control information, and the reproduction clock The rotation control of the spindle motor 37 is performed so that the period becomes a predetermined constant period.

The slide mechanism 38 holds the spindle motor 37 so as to be slidable in the tracking direction (radial direction of the hologram recording medium HM). That is, the slide movement (sled movement) in this case is realized by moving the hologram recording medium HM side.
The slide operation by the slide mechanism 38 is controlled by the slide drive unit 39. The slide drive unit 39 includes a motor for driving the slide mechanism 38, and the slide mechanism 38 is configured to slide the spindle motor 37 based on the driving force of the motor.

  Note that the slide movement can also be realized by moving the optical unit UN side by the slide mechanism 38.

The servo circuit 35 generates various servo signals for focus, tracking, and sled based on the focus error signal FE and tracking error signal TE from the matrix circuit 33 described above, and performs a servo operation.
That is, a focus servo signal and a tracking servo signal are generated according to the focus error signal FE and the tracking error signal TE, and these are generated as drive signals (focus drive signal FD and tracking drive signal TD) of the biaxial mechanism 11 shown in FIG. By supplying, the focus coil and tracking coil of the biaxial mechanism 11 are driven and controlled by drive signals corresponding to the servo signals. As a result, a tracking servo loop and a focus servo loop by the photodetector 21, the matrix circuit 33, the servo circuit 35, and the biaxial mechanism 11 are formed.
The servo circuit 35 turns off the tracking servo loop in response to an instruction from the control unit 40 and outputs a jump pulse as the tracking drive signal TD, thereby executing a track jump operation.

  The servo circuit 35 slides the slide mechanism 38 by the slide drive unit 39 based on a thread error signal obtained as a low frequency component of the tracking error signal TE, a seek operation control from the control unit 40, and the like in the tracking direction. The relative positional relationship between the optical unit UN and the hologram recording medium HM is changed.

  In addition, the servo circuit 35 also controls the start and stop of the spindle motor 37 based on instructions from the control unit 40.

Various operations of the servo system as described above are controlled by a control unit 40 configured by a microcomputer including, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like.
The control unit 40 performs overall control of the recording / reproducing apparatus 30 by executing each arithmetic processing / control processing based on a program stored in a required memory such as the ROM.

For example, the control unit 40 controls the recording / reproducing position of the hologram by controlling the operation of the servo system described above.
Specifically, when a certain data recorded on the hologram recording medium HM is to be reproduced, first, seek operation control to the target address is performed. That is, an instruction is given to the servo circuit 35 to execute an access operation targeting the target address. Here, according to the above description, it is necessary to irradiate the reference light when reproducing the data (hologram) recorded on the hologram recording medium HM. For this reason, at the time of reproduction, along with the above-described seek operation control, the modulation control unit 31 executes the drive control operation of the SLM 4 corresponding to the reproduction described above to cause the SLM 4 to generate reference light.

For example, when data is recorded at a certain position on the hologram recording medium HM, an instruction is given to the servo circuit 35 to execute an access operation to the target address, and the modulation control unit 31 is made to record data. By instructing to start the drive control of the corresponding SLM 4, the signal light is generated together with the reference light.

<Second Embodiment>

Next, a second embodiment will be described.
In the second embodiment, wavelength conversion is performed only for light in a partial region of light emitted from a single light source, so that two types of light having different wavelengths are obtained.

FIG. 5 is a diagram for explaining the configuration of the recording / reproducing device (light irradiation device) as the second embodiment, and mainly shows only the configuration of the optical system as in FIG. FIG.
In the second embodiment, the overall configuration of the recording / reproducing apparatus is the same as that described above with reference to FIG.
Further, in FIG. 5, portions already described in FIG. 1 are denoted by the same reference numerals and description thereof is omitted.

As shown in the figure, in the optical unit UN in this case, the beam splitter 3, the mirror 16, the wavelength converter 17, the mirror 18, and the polarization beam splitter 19 included in the optical unit UN shown in FIG. 1 are omitted. Above, a partial wavelength converter 40 and a mirror 41 are provided.
As shown in the figure, the partial wavelength converter 40 is inserted between the dichroic mirror 8 and the quarter-wave plate 9. As will be described later, since the partial wavelength conversion unit 40 performs wavelength conversion only for light in a predetermined region of incident light, the insertion position is formed by a relay lens system including the relay lens 5 and the relay lens 6. It is preferable that the position becomes the real image plane of the SLM 4 to be set or a position close to it.
The mirror 41 is installed so as to guide the reflected light (position control information reflected light) from the dichroic mirror 8 to the condenser lens 20.

FIG. 6 is a plan view of the partial wavelength conversion unit 40 (a plane parallel to the incident surface).
As shown in FIG. 6, the partial wavelength conversion unit 40 is set with a light transmission region An and a wavelength conversion region Ac. In this case, the light transmission region An is an inner circular region including the center of the partial wavelength conversion unit 40, and the wavelength conversion region Ac is an annular region outside the light transmission region An.
The light transmission region An is, for example, a hollow region or a region made of a material that has transparency such as transparent glass or transparent resin and does not change the wavelength of incident light. Further, the wavelength conversion area Ac is an area configured to convert the wavelength of incident light by the same structure as that shown in FIG. 3, for example. That is, by adopting such a configuration, the partial wavelength conversion unit 40 in this case is configured to partially perform wavelength conversion only in the outer region of the incident light.

Corresponding to such a partial wavelength converter 40, the recording / reproducing apparatus in this case generates light to be position control light outside the reference light.
Specifically, each area set in the SLM 4 in this case is as shown in FIG.
As shown in FIG. 7, the SLM 4 in this case includes the signal light area A2, the gap area A3, and the reference light area A1 described above, and a boundary area A4 outside the reference light area A1. Thus, the position control light generation area A5 is set. Both the boundary area A4 and the position control light generation area A5 are annular regions.

Each pixel in the boundary area A4 is turned off (not lit) during recording / reproduction. On the other hand, each pixel in the position control light generation area A5 is turned on (lit) during recording / reproduction.
For confirmation, the modulation control unit 31 performs drive control of the entire SLM 4 including drive control of the boundary area A4 and the position control light generation area A5.

In the partial wavelength conversion unit 40 shown in FIG. 6, the size of the light transmission region An is set so that the entire light through the reference light area A1 in the SLM 4 is incident.
The size of the wavelength conversion area Ac is set so that light through the position control light generation area A5 in the SLM 4 is incident.
As a result, among the light emitted from the laser diode 1, the signal light at the time of recording, the reference light, and the reference light at the time of reproduction are not subjected to wavelength conversion (in this case, for example, about 405 nm) and more than the reference light area A1. It is possible to partially convert the wavelength only for the light in the outer partial region, and generate position control light (for example, 650 nm in this case) in the region.

Even in the second embodiment in which the wavelength conversion is performed only in a part of the region in this way, it is necessary to irradiate laser beams with different wavelengths when performing hologram recording / reproduction and position control thereof. The number of light sources to be provided can be only one.

<Modification>

As mentioned above, although each embodiment of this invention was described, as this invention, it should not be limited to the specific example demonstrated so far.
For example, the wavelength of the recording / reproducing light and the wavelength of the position control light exemplified in the above description are merely examples, and of course should not be limited to these.
Here, in order to prevent the recording layer 107 from being exposed to light by the position control light, at least the wavelengths of the recording / reproducing light and the position control light may be different. Therefore, as a combination of wavelengths, contrary to the above description, the wavelength of recording / reproducing light> the wavelength of position control light may be used.
At this time, in the wavelength conversion region Ac of the wavelength conversion unit 17 or the partial wavelength conversion unit 40, the wavelength conversion for shortening the incident light is performed. In this case, as the wavelength conversion material 17C, a so-called wavelength conversion material 17C is used. Nonlinear optical materials having harmonic generation effects (nonlinear optical effects) such as SHG (Second Harmonic Generation) and THG (Third Harmonic Generation) can also be used. Examples of such nonlinear optical materials include ferroelectric crystal KTP (KTiOPO ₄ : emits second harmonic) and borate crystal BBO (β-BaB ₂ O ₄ : fourth harmonic). For example).
A semiconductor material can also be selected as the wavelength conversion material 17C. The wavelength conversion material 17C is not particularly limited as long as it has a wavelength conversion function.

  In addition, although a Fabry-Perot resonator has been exemplified as a configuration for obtaining coherent light as wavelength-converted output light, other optical resonator structures such as a diffraction grating type resonator are also employed. You can also.

In the above description, the case where the hologram recording medium HM is rotationally driven to perform recording / reproduction is exemplified. However, the optical unit UN side is moved to record / reproduce the target position on the hologram recording medium. It is also possible to adopt a method of performing
In that case, the hologram recording medium may have a rectangular shape instead of a disk shape. Also, the track TR is not spiral or concentric, but a plurality of straight tracks TR can be arranged.

  In the description so far, the case where the coaxial method is adopted is exemplified as the case where the signal light area A2 is set to be circular, and the reference light area A1 is set to be ring-shaped accordingly. However, the shapes of the reference light area A1 and the signal light area A2 are not limited to these, and can be set to have other shapes such as a rectangular shape. It can be suitably applied.

Further, the arrangement relationship between the reference light area A1 and the signal light area A2 can be reversed, and the reference light area A1 can be set on the inner side and the signal light area A2 can be set on the outer side.
At this time, when the method of performing wavelength conversion only in a partial region as in the second embodiment is adopted, in the partial wavelength conversion unit 40, the inner side is the wavelength conversion region Ac, and the outer side is the light transmission region. It will be An.
When the method of the second embodiment is adopted, the setting position, shape, and size of the wavelength conversion region Ac need to be varied according to the arrangement relationship, shape, and size setting of the signal light area A2 and the reference light area A1. . The setting position, shape, and size of the wavelength conversion area Ac depend on the actual positional relationship, shape, and size of the reference light / signal light. ) Is not performed, and may be set as appropriate.

  In the above description, the case where the present invention is applied when a coaxial hologram recording / reproducing system is employed has been exemplified. However, the present invention includes other hologram recording / reproducing systems such as a two-beam method. It can be suitably applied also when employed.

In the above description, the case where the light obtained by wavelength conversion is used as the position control light is exemplified, but conversely, the light on the side not subjected to wavelength conversion can also be used as the position control light. It is.
Of course, the light obtained by wavelength conversion can also be used for other purposes than hologram recording / reproduction and position control.

It is the figure which extracted and showed mainly the structure of the optical system as a figure for demonstrating the structure of the light irradiation apparatus as 1st Embodiment. It is a figure for demonstrating each area set to the spatial light modulator of the light irradiation apparatus of 1st Embodiment. It is the figure which showed the internal structural example of the wavelength conversion part. It is the block diagram which showed the whole structure of the light irradiation apparatus as 1st Embodiment. It is the figure which extracted and showed mainly the structure of the optical system as a figure for demonstrating the structure of the light irradiation apparatus as 2nd Embodiment. It is a top view (surface parallel to an entrance plane) of the wavelength conversion part used with the light irradiation apparatus of 2nd Embodiment. It is a figure for demonstrating each area set to the spatial light modulator of the light irradiation apparatus of 2nd Embodiment. It is a figure for demonstrating the recording method of the data with respect to a hologram recording medium. It is a figure for demonstrating the reproduction | regeneration method of the data recorded on the hologram recording medium. It is the figure which showed the cross-section of the hologram recording medium. It is the figure which showed the internal structure of the recording / reproducing apparatus as a prior art example.

Explanation of symbols

  1 laser diode (LD), 2 collimator lens, 3 beam splitter, 4 SLM (spatial light modulator), 5, 6, 12, 14 relay lens, 7, 19 polarization beam splitter, 8 dichroic mirror, 9 1/4 wavelength Plate, 10 Objective lens, 11 Biaxial mechanism, 13, 16, 18, 41 Mirror, 15 Image sensor, 17 Wavelength conversion unit, 17A Total reflection mirror, 17B Partial reflection mirror, 17C Wavelength conversion material, 20 Condensing lens, 21 Photodetector (PD), 30 recording / reproducing apparatus, 31 modulation control unit, 32 data reproducing unit, 33 matrix circuit, 34 address detection / clock generation circuit, 35 servo circuit, 36 spindle control circuit, 37 spindle motor (SPM), 38 slide Mechanism, 39 slide drive unit, 40 control unit, HM hologram Recording medium, 105 antireflection film, 106 cover layer, 107 recording layer, 108, 110 reflection film, 109 intermediate layer, 111 substrate

Claims (8)

A single light source for irradiating light to a hologram recording medium on which information recording is performed by causing a change in refractive index according to the intensity distribution of irradiation light;
A wavelength conversion unit that performs wavelength conversion by inputting a part of the light from the light source;
A light irradiation unit that irradiates the hologram recording medium with light emitted from the light source and passed through the wavelength conversion unit, and light emitted from the light source and not passed through the wavelength conversion unit;
A light irradiation apparatus comprising: The wavelength conversion unit is configured by including a wavelength conversion material in a Fabry-Perot resonator.
The light irradiation apparatus according to claim 1. The wavelength conversion unit converts the wavelength of light obtained by separating a part of the light from the light source,
The light irradiation apparatus according to claim 2. The wavelength conversion unit converts the wavelength of light in a partial region of light from the light source,
The light irradiation apparatus according to claim 2. The hologram recording medium includes a recording layer on which information recording is performed due to a change in refractive index according to the intensity distribution of irradiation light, a wavelength selective reflection film formed in a lower layer of the recording layer and having wavelength selectivity, A position control layer formed under the wavelength selective reflection film and provided with a position control structure for controlling the recording / reproducing position;
The light irradiation part is
The hologram recording medium is configured to irradiate light emitted from the light source via the wavelength conversion unit and light emitted from the light source and not via the wavelength conversion unit via a common objective lens. And
In addition, a position control light detection unit that detects position control information reflected light that is obtained through the position control layer light through the wavelength conversion unit irradiated by the light irradiation unit,
The light irradiation apparatus according to claim 1.   The light irradiation apparatus according to claim 2, wherein the wavelength conversion material is a phosphor.   The light irradiation apparatus according to claim 2, wherein the wavelength conversion material is a semiconductor. Wavelength conversion is performed by inputting a part of light from a single light source for irradiating light to a hologram recording medium on which information recording is performed due to a change in refractive index according to the intensity distribution of irradiation light. A wavelength conversion step;
A light irradiation step of irradiating the hologram recording medium with light emitted from the light source and subjected to the wavelength conversion step; and light emitted from the light source and not subjected to the wavelength conversion step;
A light irradiation method comprising:

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