JP4475432B2 - Information recording method and information reproducing method - Google Patents

Description

  The present invention relates to a laminated waveguide type three-dimensional recording medium, an information recording method, and an information reproducing method that enable additional recording and rewriting recording of optically large-capacity information.

Conventionally, as disclosed in Patent Document 1, a technique for recording a hologram on a recording medium having a laminated waveguide structure has been proposed. In the technique described in Patent Document 1, bacteriorhodopsin, which is a photochromic material, is applied as a recording material, and additional recording and rewriting recording of information are realized by utilizing the characteristics of change in the refractive index of bacteriorhodopsin due to light absorption. ing.
JP-A-9-101735

  However, there are the following problems in performing hologram recording on the recording medium as described above.

  First of all, recording by hologram can write a large amount of information in principle, but the entire recording layer undergoes a structural change when recording information, so the interface of the recording layer is easily deformed due to shrinkage accompanying the structural change, There is a problem that a good waveguide structure is difficult to maintain and the number of stacked layers cannot be increased.

  In order to record the hologram, it is necessary to guide the reference light to the optical waveguide. However, if the cladding layer separating the recording layers is thin, the reference light incident on the optical waveguide is transmitted through the cladding layer and is not intended. Since information is written in the recording layer, the thickness of the cladding layer needs to be about 10 μm or more in order to avoid erroneous recording, and there is a problem that the lamination density of the waveguide structure is limited.

  In addition, since the incident reference light needs to be sufficiently absorbed by the recording layer, if the recording medium becomes large and the waveguide distance becomes long, the guided reference light attenuates and the amount of light necessary for recording reaches. As a result, there is a problem that the size of the medium cannot be increased.

  Further, since the hologram information is subjected to optical Fourier transform at the time of recording, it is necessary to record the hologram information at one time on the surface of any one of the selected recording layers. Therefore, in order to additionally record a part of information recorded on a certain recording layer, or to rewrite and record a part of the information, the entire surface of the recording layer must be re-recorded. is there.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to use a recording method that does not limit an increase in recording density in a laminated waveguide type recording medium, and to perform one recording. A layered waveguide type three-dimensional recording medium, an information recording method, and an information recording method capable of performing additional recording or rewriting recording of a part of information without re-recording the entire layer in which the recording is performed. It is to provide an information reproduction method.

In order to solve the above problems, the present invention includes an optical waveguide layer for guiding light, is provided are laminated in multi-cladding layer, the optical waveguide layer is configured partially or wholly in optical recording materials An information recording method for a laminated waveguide type three-dimensional recording medium for recording information by a change in the optical recording material , wherein information is recorded in each optical waveguide layer by entering light from the surface of the cladding layer The light in each region of the optical waveguide layer is condensed by a plurality of portions of the optical recording material in a predetermined region through a phase plate that shifts the phase of a part of the incident light every time. In the information recording method , information is recorded for each information unit by changing a plurality of locations of the recording material .

According to the present invention, in the invention described above, the optical recording material is composed of a two-photon absorbing material represented by the following chemical formula (1) or chemical formula (2), and the two-photon absorbing material is formed by the condensed light. changing the previous SL optical recording material causing two-photon absorption and performs recording of information for each of the information units.

According to the present invention, in the invention described above, information is recorded for each information unit by changing a refractive index by two-photon absorption of the two-photon absorbing material, and the film thickness of the recording layer and the two-photon absorption are recorded. The product of the refractive index change rate due to the two-photon absorption of the material is ¼ or less of the wavelength of light incident from the end face of the optical waveguide layer during reproduction.

The present invention, in the invention described above, and the information unit is characterized by a unit of multi-value bits.

In the invention described above, when condensing light at a plurality of locations in the region, the light is collected at the plurality of locations in a positional relationship in which a change in the amount of light generated during reproduction is increased by the plurality of locations. It is characterized by doing .

According to the present invention, in the invention described above, the phase plate is disposed in parallel with the surface of the optical waveguide layer, and the angle is associated with a predetermined condition in the disposed plane. The phase plate is rotated to collect light at a plurality of locations in the area of each recording layer .

In the present invention, an optical waveguide layer for guiding light and a clad layer are stacked in multiple layers, and the optical waveguide layer is partially or entirely made of an optical recording material, and the optical recording material changes An information reproducing method for a laminated waveguide type three-dimensional recording medium in which information is recorded by the method, wherein planar light guided from the end face of the optical waveguide layer into the plane of the optical waveguide layer is incident on each optical waveguide layer Then, the change in the amount of light generated in the optical recording material of the optical waveguide layer is read in two dimensions by the plane light incident on each optical waveguide layer, and the change in the read amount of light is determined for each region predetermined for each information unit. When information is detected and there is a change in the amount of light at a plurality of locations in the area, information is reproduced for each information unit based on the positional relationship between the locations where the change in the amount of light exists. Is the method .

The present invention is the above-described invention, wherein the optical recording material is a two-photon absorption material represented by the following chemical formula (3) or chemical formula (4), and the two-photon is obtained by two-photon absorption of the two-photon absorption material. Information is recorded by a change in the absorbing material, and the change in the read light amount is detected for each predetermined region for each information unit, and the information is reproduced for each information unit .

The present invention is characterized in that, in the invention described above, the information unit is a unit of multi-value bits .

The present invention is the invention described above, wherein the planar light is incident from end faces in different directions, and the change in the amount of light generated in the optical recording material by the planar light incident for each direction of the end faces is read in two dimensions, A change in the read light amount is detected for each of the regions, and is reproduced as information on a specific condition that is associated in advance for each direction of the end face .

The present invention is characterized in that, in the invention described above, the planar light to be guided is guided in a single mode or a multimode .

According to this invention, the laminated waveguide type three-dimensional recording medium is provided with the optical waveguide layer for guiding light and the clad layer laminated in multiple layers, and the optical waveguide layer is partially or entirely optical. The recording material is configured to record information for each information unit by changing the state of the optical recording material in a predetermined region for each information unit to be recorded.
Thereby, since it is possible to change the state of the optical recording material by specifying a part of a predetermined region for each information unit in the optical waveguide layer, without rewriting the entire optical waveguide layer like a hologram, It becomes possible to perform additional recording or rewriting recording in which a part of information is rewritten in a partial region of the optical waveguide layer.
In addition, since information is recorded by collecting incident light in a predetermined region of the optical waveguide layer, the structural change of the optical recording material is limited to the recording region, and the entire optical waveguide layer does not change. A good waveguide structure is easily maintained.
Further, since reference light is not required for information recording unlike a hologram, the thickness of the cladding layer can be made thinner than that for recording information by the hologram, and the stacking density can be increased.
In addition, since information is recorded by focusing incident light on an optical recording material in a predetermined area when information is recorded, information recording by a hologram is possible without depending on the waveguide distance as in a hologram. In comparison, the size of the recording medium can be increased.
In addition, by having such a structure, information can be reproduced in a two-dimensional manner at a high speed by allowing planar light to enter the end face of any one of the optical waveguide layers during information reproduction. It is possible to realize reading of a large amount of information.

According to the present invention, an information recording method for recording information on a laminated waveguide type three-dimensional recording medium is predetermined for each information unit to be recorded on each optical waveguide layer by entering light from the surface of the cladding layer. The optical recording material is condensed on the optical recording material in a certain region, and the information is recorded for each information unit by changing the optical recording material in the region of each optical waveguide layer by the condensed light.
As a result, it is possible to specify a predetermined region that is a part of the optical waveguide layer for each information unit by incident light without re-recording the entire optical waveguide layer on the laminated waveguide type three-dimensional recording medium. Since the state of the optical recording material can be changed, additional recording or rewriting recording that rewrites a part of information is performed on a part of the optical waveguide layer without rewriting the entire optical waveguide layer like a hologram. It becomes possible.
In addition, since information is recorded by collecting incident light in a predetermined region of the optical waveguide layer, the structural change of the optical recording material is limited to the recording region, and the entire optical waveguide layer does not change. A good waveguide structure is easily maintained.
Further, since reference light is not required for information recording unlike a hologram, the thickness of the cladding layer can be made thinner than that for recording information by the hologram, and the stacking density can be increased.
In addition, since information is recorded by focusing incident light on an optical recording material in a predetermined area when information is recorded, information recording by a hologram is possible without depending on the waveguide distance as in a hologram. In comparison, the size of the recording medium can be increased.

Further, according to the present invention, an information reproducing method for reproducing information from a laminated waveguide type three-dimensional recording medium is a planar light that is guided in the plane of the optical waveguide layer from the end face of the optical waveguide layer for each optical waveguide layer. The change in the amount of light generated in the optical recording material of the optical waveguide layer is read in two dimensions by the planar light incident on each optical waveguide layer, and the change in the read light amount is detected for each predetermined region for each information unit. Thus, the information is reproduced for each information unit.
As a result, it is possible to reproduce information in a two-dimensional manner by making plane light incident on the end face of any one optical waveguide layer of the laminated waveguide type three-dimensional recording medium. Can be read out.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing the structure of a laminated waveguide type three-dimensional recording medium 1 according to the present embodiment.
The laminated waveguide type three-dimensional recording medium 1 has a structure in which a clad layer 2 and an optical waveguide layer 5 including a core layer 3 and a recording layer 4 are laminated in the order of the clad layer 2 and the optical waveguide layer 5. The one set of structures is formed by laminating multiple layers on a substrate 6 made of, for example, glass or resin. As the material of the recording layer 4, for example, an organic boron polymer that is an optical recording material of a two-photon absorption material is used. The organoboron polymer is a compound represented by the following chemical formula ( 5 ) or chemical formula ( 6 ).

  Here, two-photon absorption generated in a two-photon absorption material such as an organic boron polymer means that one molecule or polymer chain absorbs two photons (photons) at the same time, so that the molecule is in the ground state. It is a phenomenon of transition from the excited state to the excited state. If the recording layer 4 is formed using a two-photon absorption material that generates two-photon absorption, information can be recorded for each predetermined area of the recording layer 4, for example, in units of bits. In other words, the region of the recording layer 4 is irradiated with laser light having a wavelength corresponding to half of the energy gap between the ground state and the excited state, and a refractive index derived from structural change or the like in the storage medium by a two-photon absorption process. Cause change. The predetermined area including the area where the refractive index change occurs (hereinafter referred to as the recording area) is indicated by “1”, and the area where the refractive index change occurs is not included, that is, the recording area is not included. By indicating “0” in the predetermined area, information can be recorded and additionally recorded in units of bits for each predetermined area.

  In recording using the two-photon absorption process, it occurs in proportion to the square of the light intensity of the incident light, so compared to the one-photon absorption process, the spot size due to the refractive index change formed at a predetermined position of the storage medium, In particular, the size in the optical axis direction can be reduced. The fact that the spread of the beam of incident light in the direction of the optical axis can be kept small means that higher-density three-dimensional optical recording can be performed. That is, in each recording layer 4 on which information is optically written, the above-described predetermined area of each recording layer 4 can be made smaller than that of the one-photon type. As a result, recording in each recording layer is possible. Not only can the density be improved, but also the intervals between the recording layers can be reduced, and high-density information recording can be achieved.

  The core layer 3 guides light incident from the end face, and changes the amount of light in the recording area by scattering of guided light based on the change in the refractive index of the recording area of the recording layer 4. The cladding layer 2 is made of a material having a refractive index smaller than that of the core layer 3 in order to guide light in the core layer 3.

  Here, the relationship between the refractive indexes applied to the recording layer 4, the core layer 3, and the cladding layer 2 will be described. For example, when an organic boron polymer is applied to the recording layer 4, the refractive index of the organic boron polymer is about 1.6, and the organic boron polymer has a higher light absorption rate than the core layer 3. Therefore, in order to function as a waveguide, the refractive index of the core layer 3 is not less than the refractive index of the recording layer 4, for example, at least 1.6 or more when the refractive index of the recording layer 4 is 1.6. To do. Thereby, the guided light can be guided without being concentrated on the organic boron polymer of the recording layer 4. At this time, the cladding layer 2 sets a refractive index smaller than the refractive index of the core layer 3, for example, a value of 1.54 or less, for guiding light in the core layer 3. These values are only examples, and when the required waveguide distance is short or when a wavelength having a low absorption rate of the organic boron polymer is used, the refractive index of the core layer 3 and the recording layer 4 is the cladding layer 2. As long as the condition that the refractive index is larger than the above is satisfied, it can be appropriately changed. The refractive indexes of the cladding layer 2 and the core layer 3 are values that can be realized with resin.

Next, the relationship among the thicknesses of the recording layer 4, the core layer 3, and the cladding layer 2 will be described. The limit value of the thickness of the recording layer 4 depends on the film thickness of the recording layer 4, the refractive index change Δn in the recording layer 4 and the wavelength of reproduction light during reproduction, and the lower limit is about 0.1 μm. About 1 μm is required.
For example, assume that the thickness of the recording layer 4 is about 0.2 μm. At this time, in order to avoid the upper and lower recording layers 4 from being exposed during recording on a certain recording layer 4, the distance between the adjacent recording layers 4 depends on the focal depth and needs to be at least 2 μm or more. is there. Under such conditions, the following description will be made assuming that the recording layer 4 has a thickness of about 0.2 μm.

  Note that a gap layer may be provided at the interface between the core layer 3 and the recording layer 4 in order to suppress energy loss of the guided light.

  In the example of the above embodiment, the organic boron polymer that is a two-photon absorption material is described as an example. However, as the optical recording material, a one-photon absorption material may be used, and the optical recording material In addition to the refractive index, information recording may be performed by changing the state of fluorescence characteristics, absorption spectrum, dipole moment, and the like.

  Further, in the structure of the laminated waveguide type three-dimensional recording medium 1, the core layer 3 and the recording layer 4 are not formed separately as the optical waveguide layer 5, but the core without the recording layer 4 as shown in FIG. The optical waveguide layer 5 containing the optical recording material in the layer 3 may be formed.

  In the example of the above embodiment, an example is described in which information is reproduced by a change in the amount of light generated in the recording area due to scattering by the guided light. However, the present invention is not limited to scattering, but reflection, light emission, fluorescence, etc. in the recording area Information may be recorded by changing the state of the storage area so that information is reproduced by causing a change in the amount of light due to the optical phenomenon.

(Recording method of information on laminated waveguide type 3D recording medium)
Next, a method for recording information on the laminated waveguide type three-dimensional recording medium 1 will be described.

(Embodiment of First Information Recording Device)
FIG. 3 is a diagram showing an information recording apparatus 10 including a confocal optical system for recording information on the laminated waveguide type three-dimensional recording medium 1.

  The light source 21 emits incident light (hereinafter referred to as recording light) for forming a recording area in each recording layer 4 of the laminated waveguide type three-dimensional recording medium 1. For example, when an organic boron polymer is used as the optical recording material of the recording layer 4 of the laminated waveguide type three-dimensional recording medium 1, the organic boron polymer efficiently generates two-photon absorption with respect to a wavelength of about 800 nm and is refracted. It is known to cause rate changes. Therefore, for example, a titanium sapphire laser having a wavelength of 796 nm, a pulse width of 150 fs (femtosecond), and a repetition frequency of 80 MHz is used as the light source 21. The photodetector 15 determines whether or not the recording light is focused on each recording layer 4 of the laminated waveguide type three-dimensional recording medium 1 and reflects light from the interface of each layer of the laminated waveguide type three-dimensional recording medium 1. It is an apparatus which detects and determines.

  The shutter 11 controls the exposure time of the light source 21. For example, when the average output of the light source 21 is 0.1 mW and the spot diameter of the recording area on the recording layer 4 is about 1 μm, the refractive index of the organoboron polymer is set. In order to change by 0.001, an exposure time of about 40 ms is required. The beam splitter 12 transmits the recording light from the light source 21 incident through the shutter 11 in the direction of the laminated waveguide type three-dimensional recording medium 1 and is polarized by 45 degrees by the quarter wavelength plate 16. The reflected light from the interface between the recording layer 4 and the clad layer 2 to be recorded on the type 3D recording medium 1 is reflected in the direction of the photodetector 15.

  The Z-axis stage 19 and the XY-axis stage 20 are configured as shown in FIG. The laminated waveguide type three-dimensional recording medium 1 is fixed to the Z-axis stage 19, and when focusing on the recording layer 4 having a thickness of 0.2 μm described above, for example, the Z-axis stage 19 has a resolution of about 0.1 μm. A piezoelectric motor capable of performing axial position control is applied. A Z-axis stage 19 is fixed to the XY-axis stage 20. For example, when the spot size on the recording layer 4 by the recording light of the light source 21 is about 1 μm, the X-axis and Y-axis directions can be resolved with a resolution of 1 μm or less. A stepping motor capable of performing position control is applied.

  Next, the operation of the information recording apparatus 10 will be described. First, when recording light is emitted from the light source 21 in a state where the shutter 11 is opened, the recording light passes through the beam splitter 12 and the quarter wavelength plate 16 and is laminated by the laminated waveguide type tertiary. The light is condensed on the original recording medium 1 so as to have a spot diameter of about 1 μm. Reflection light is generated from the interface of each layer of the laminated waveguide type three-dimensional recording medium 1 by the incidence of the recording light. The reflected light is converted into parallel light by the lens 18 and is transmitted through the quarter-wave plate 16 to be polarized by 45 degrees. Is done. The polarized reflected light is reflected by the beam splitter 12 in the direction of the lens 13, collected by the lens 13, and the collected reflected light is detected by the photodetector 15 through the pinhole 14. The photodetector 15 can detect the position of the interface of each layer by detecting the amount of reflected light. Then, the position of the focal point of the recording light in the laminated waveguide type three-dimensional recording medium 1 is detected, and the Z-axis stage 19 is driven so as to be focused on the depth of the recording layer 4 on which information is recorded based on the detection result. To control positioning.

  FIG. 5 is a diagram showing a surface of a certain recording layer 4, and each cell in FIG. 5 indicates an area predetermined for each bit unit which is a unit of information recording. The circles shown in some squares indicate the spot diameters to be collected, and the squares in which the circles are drawn indicate areas where information is recorded by changing the state by the recording light, that is, the recording areas described above. Yes. The XY axis stage 20 controls the positioning by driving the XY axis stage 20 so that the recording light is focused on the grid for recording information. FIG. 6A is a diagram showing an example of a spot generated by the recording light collected in the area of the mesh in FIG. 5, and FIG. 6B shows the distribution of the light amount in the spot. It is the figure shown, and the refractive index of the optical recording material of the recording layer 4 changes according to the said distribution.

Here, the influence of the wavefront disturbance due to the presence / absence of the recording region formed in the recording layer 4 of the laminated waveguide type three-dimensional recording medium 1 due to the change in the refractive index will be described. When the film thickness of the recording layer 4 is d, the refractive index change is Δn, and the wavelength of the reproduction light is λ, the wavefront disturbance due to the presence or absence of the recording area per recording layer 4 is dΔn << λ (dΔn is λ A value sufficiently smaller than that). When Δn is 10 ⁻² , d is 200 nm, and λ is 660 nm, dΔn is 2 nm, and this value corresponds to the wavefront disturbance per layer of the recording layer 4. If the bit position in the laminated waveguide type three-dimensional recording medium 1 is random, the stacking effect on the wavefront disturbance due to lamination is proportional to (the number of laminations) ^0.5. dΔn (dΔn = 2 nm) = 20 nm. This value is equal to or less than λ / 30, and satisfies less than λ / 4, which is an optical flat reference that is a limit that makes it impossible to detect scattered light with a microscope 37 used during reproduction, which will be described later. Therefore, the wavefront disturbance due to the presence / absence of the recording area does not have an influence that is detected by the microscope 37 even if the recording areas are stacked, and the change in the refractive index is made lower than 10 ⁻² . The laminated waveguide type three-dimensional recording medium 1 can be configured with a film thickness of 200 nm. Further, in the case of about 1 μm shown as the upper limit value of the thickness of the recording layer 4 described above as an example, the wavelength λ of the reproduction light is the shortest when the practical light level of 500 nm / 2 250 nm is used. If it is assumed that Δn = 10 ⁻² and 100 layers are laminated, then 10 × dΔn (dΔn = 10 nm) = 100 nm, and this value is also the optical flat standard of the reproduction light wavelength of 400 nm. That is, less than 1/4. The lower limit of the refractive index change Δn is required to be 10 ⁻⁴ in consideration of detection of scattered light during reproduction.

(Embodiment of Second Information Recording Device)
FIG. 7 is a diagram showing a configuration of the information recording apparatus 10 a in which the phase plate 17 is provided between the quarter wavelength plate 16 and the lens 18 in the information recording apparatus 10 of FIG. 3. Except for the point provided with the phase plate 17, there is no difference in configuration from the information recording apparatus 10 of FIG. 3, and the difference based on the provision of the phase plate 17 will be described below.

  The phase plate 17 has the structure shown in FIG. 8. When the section of the recording light that is parallel light that is transmitted through the quarter-wave plate 16 and is incident on the phase plate 17 is circular, the phase plate 17 has a semicircular shape. The phase of the light is transmitted with a half-wave shift from the remaining half-circle light. The recording light after transmission is condensed by the lens 18 and, as shown in FIG. 8A, a double peak spot having an interval of about 1 μm is generated at the focal point in one region of the recording layer 4. FIG. 9B is a diagram showing the distribution of the light quantity of the spot of the double peak, and the refractive index of the optical recording material of the recording layer 4 changes according to the distribution.

  FIG. 10 is a diagram showing incident light and a refractive index change distribution of a recording area generated in the recording layer 3 by the incident light. FIG. 10A shows a recording in which the refractive index changes according to the intensity distribution of incident light by the information recording apparatus 10 without the phase plate 17 and the light quantity distribution of the spot shown in FIG. 6B generated by the incident light. FIG. 4 is a diagram schematically showing a refractive index change distribution of an optical recording material of a layer 4. FIG. 10B shows the refractive index according to the intensity distribution of incident light by the information recording apparatus 10a including the phase plate 17 and the light quantity distribution of the spot shown in FIG. 9B generated by the incident light. FIG. 6 is a diagram schematically showing a refractive index change distribution of an optical recording material of a recording layer 4 that changes. 10A and 10B, when reproduction light is incident from the end face of the core layer 3, scattered light having a light amount according to the steepness of the refractive index change distribution is emitted. For example, in FIG. 10A, since the change in the refractive index is large in the portion where the intensity of the incident light changes from the high portion to the low portion, the intensity of the incident light is higher than the portion where the intensity of the incident light is highest. Scattered light having a large amount of light can be obtained from the portion that changes from the portion to the low portion. Here, comparing FIG. 10 (a) and FIG. 10 (b), from the portion where the intensity of the incident light of the refractive index change distribution in the valley portion of the two peaks of the incident light intensity distribution of FIG. 10 (b) is high. The amount of change in the portion that changes to the lower portion is steeper than the amount of change in the portion that changes from the high intensity portion to the low portion of the incident light in the refractive index change distribution in FIG. For this reason, since the recording layer 4 on which recording is performed using the phase plate 17 of FIG. 10B emits scattered light having a larger light amount during reproduction, an S / N ratio is obtained when information is reproduced and extracted. (Signal to Noise Ratio) can be increased and extracted.

(Reproduction method of information from laminated waveguide type 3D recording medium)
FIG. 11 is a diagram illustrating a configuration of an information reproducing apparatus 30 including a reproducing optical system. In the information reproducing apparatus 30, a laminated waveguide type 3D recording medium 1 on which information is recorded is fixed to a Z axis stage 33, and the positioning of the laminated waveguide type 3D recording medium 1 in the Z axis direction is controlled. To do.

The light source 31 emits incident light (hereinafter referred to as reproduction light) incident on the end face of the core layer 3 of the laminated waveguide type three-dimensional recording medium 1. As the light source 31, for example, a laser diode having a wavelength of 650 nm that has no optical absorption in the recording layer 4 and an average output of about 15 mW / cm ² is used. The cylindrical lens (or cylindrical lens) 32 is disposed at a position where the beam diameter of the reproduction light emitted from the light source 31 is expanded to about 1 cm, and the reproduction light is condensed into a linear shape and reproduced in a planar light state. The light enters the end surface of the core layer 3 that is in contact with the target recording layer 4 at the lower surface.

  The microscope 37 can be driven in the X-axis direction and the Y-axis direction with respect to the surface of the laminated waveguide type three-dimensional recording medium 1, and exists on the entire surface of the recording layer 4 by the reproduction light incident on the core layer 3. Of the scattered light generated from the recording region, the scattered light existing in a certain range of the recording layer 4 that can be imaged on the imaging surface of a CCD (Charge-Coupled Devices) camera 38 by an objective lens is laminated waveguide type three-dimensional recording medium Condensed from the surface of 1. The objective lens applied to the microscope 37 requires a resolution for forming an image of a recording area of 1 μm from the upper surface of the laminated waveguide type three-dimensional recording medium 1 on the CCD camera 38, and the laminated waveguide type three-dimensional recording medium. Since it is necessary to collect the scattered light generated from the recording layer 4 existing at the lowest position of 1, for example, a numerical aperture of 0.4 or more and 20 times or more is used. The CCD camera 38 is a device that picks up a plurality of scattered lights collected by the microscope 37 and imaged on the image pickup surface as a two-dimensional image, and uses a highly sensitive device such as ISO 350, for example.

  Next, the operation of the information reproducing apparatus 30 will be described. First, the Z-axis stage 33 is driven so that the planar reproduction light emitted from the light source 31 and condensed by the cylindrical lens 32 is incident on the end surface of the core layer 3 that is in contact with the recording layer 4 to be reproduced at the lower surface. Perform positioning. Next, the microscope 37 is focused on the recording layer 4 to be reproduced. For example, when a recording area as shown in FIG. 5 is formed in the recording layer 4, the recording area 4 is moved from a recording area existing in a certain range corresponding to a partial area of the recording layer 4 by the objective lens of the microscope 37. The scattered light is condensed and imaged on the imaging surface of the CCD camera 38, and the CCD camera 38 images the imaged scattered light. Then, image processing is performed on the two-dimensional image after imaging to cut out a predetermined area indicated by the cells shown in FIG. 5 in the recording layer 4, and based on the presence or absence of scattered light for each cut out area. Information is reproduced in bit units. When imaging of the region in the certain range is completed, the microscope 37 is then driven in the X-axis and Y-axis directions, and imaging is performed on the next region in the certain range. When imaging of all the areas of one recording layer 4 is completed, the Z-axis stage 33 is driven, and the plane reproduction light emitted from the light source 31 and collected by the cylindrical lens 32 is the next reproduction target recording layer. Positioning is performed so as to be incident on the end face of No. 4, and then the above-described imaging process for each region in a certain range is repeated, and the operation is completed when imaging for all the recording layers 4 is completed.

  The light from one recording area has a signal gain value of 14 when the exposure time is about 1/15 seconds. At this time, the noise of the CCD image sensor is 1.7 LSB (Least Significant Bit). It is possible to read information by imaging without being affected by noise.

  In the CCD camera 38, when the real field of viewable 2D image is a 1 mm square area and 1 bit is recorded in the recording area, the total number of bits recorded in the area is 1 Mbit. Become. At this time, when the information reproducing apparatus 30 can capture 10 frames per second, a reproducing speed of about 10 Mbps can be obtained.

Further, as the light source 31 that emits the reproduction light, for example, a laser diode having a wavelength of 660 nm and an average output of 100 W / cm ² is applied. The change in light intensity is within 3%. For this reason, the reproduction light from the light source 31 having a wavelength of about 650 nm and an average output of about 15 mW / cm ² is applied to the recording layer 4 for about 1/15 seconds, which is a time required for reading out the recording layer 4 per layer. Even if irradiated, the recording layer 4 is not destroyed.

  Further, the reproduction light incident on the core layer 3 is not limited to the single mode, and may be a multimode.

  Next, FIGS. 12 and 13 show a reproducing method for the laminated waveguide type three-dimensional recording medium 1 in which a double peak is formed in the recording region of the recording layer 4 using the phase plate 17 shown in FIG. FIG.

  FIG. 12 is a diagram showing a process of forming a multi-value bit recording area in which multi-values are associated in one area of the recording layer 4 and reading out the multi-value bits from the recorded information. FIG. 12A shows the correspondence between the shape of the recording area formed in the recording layer 4 and the multivalued bits 0 to 4 associated in advance. The shape of such a recording area is as follows. When recording information, the phase plate 17 can be rotated to form the information. FIG. 12B shows a two-dimensional image picked up by the CCD camera 38, and FIG. 12C shows the picked-up two-dimensional image in advance in the recording layer 4 as shown by a grid in FIG. It is the figure which showed the processing result in which the image process cut out in the defined area | region was performed. FIG. 12D shows the result of decoding using the shape of the scattered light in each cut out region and the correspondence between the shape of the scattered light and the multi-valued bits in FIG. It is possible to reproduce a one-dimensional data stream by reading this information in the vertical direction.

Next, FIG. 13 shows that the recording area of the recording layer 4 has anisotropy with respect to the reproduction light and changes the direction of the reproduction light incident on the end face of the core layer 3 during reproduction. It is the figure which showed the process of the condition reading which reproduces | regenerates only information collectively.
FIG. 13A shows the correspondence between the shape of the recording area formed in the recording layer 4 and the multi-value information of 0 to 4 associated in advance. The shape of such a recording area is as follows. When recording information, the phase plate 17 can be rotated to form the information. FIG. 13B is a view showing the recording layer 4 in which the recording area is formed by rotating the phase plate 17. FIG. 13C shows the case where the reproduction light is incident from the end face on the right side of the core layer 3 that is in contact with the lower surface of the recording layer 4 in FIG. 13B. By making the reproduction light incident from the end face, The highest amount of scattered light is emitted from the shape of the value of “sign 1” having the steep refractive index change distribution in the direction. By performing image processing of the scattered light on the two-dimensional image captured by the CCD camera 38 with the highest light intensity threshold value, it is possible to detect only the region corresponding to the condition of “reference 1”. FIG. 13D shows a case where the reproduction light is incident from the end face on the upper side of the core layer 3. In this case, this corresponds to the condition “reference numeral 2” having the most steep refractive index change distribution in the direction. Only the area to be detected can be detected.

  In the above description, it is possible to record multi-value bits and read out the conditions by changing the angle of the phase plate 17. However, by shifting the center position of the phase plate 17, the recording area of the recording layer 4 can be configured. Since one of the two peak values increases and the other decreases, information recording of multi-value bits and condition reading may be configured using this property.

  With the configuration of the laminated waveguide type 3D recording medium 1 of the above embodiment, the entire recording layer 4 is not re-recorded on one recording layer 4 of the laminated waveguide type 3D recording medium 1. In addition, it is possible to record and additionally record a part of information in bits as an information unit or in a multi-value bit unit.

  In the above-described embodiment, an example in which an organic boron polymer is applied as the two-photon absorption material has been described. However, by using a photochromic compound having a reversible reaction instead of the organic boron polymer, rewriting recording is performed in bit units. It is also possible. Examples of the photochromic compound include a diarylethene photochromic compound disclosed in JP-A-2003-308634.

In addition, with the configuration of the information recording apparatus 10 according to the above-described embodiment, two layers of the recording layer 4 are provided for each predetermined region with respect to the multilayer waveguide type three-dimensional recording medium 1 having the two-photon absorption material in the recording layer 4. It is possible to record information in bit units by causing a change in the photon absorbing material.
In addition, with the configuration of the information recording apparatus 10 of the above-described embodiment, it is possible to record multi-level bit information for each predetermined region of the recording layer 4 by using the phase plate 17.

  In addition, with the configuration of the information reproducing apparatus 30 of the above embodiment, planar reproduction light is incident on the end surface of the core layer 3 so as to be collectively for each region in a certain range of the recording layer 4 of the laminated waveguide type three-dimensional recording medium 1. Thus, information can be reproduced in two dimensions. As a result, the time delay due to the data seek due to the mechanical operation can be eliminated, and the data reading speed can be improved.

  In addition, due to the configuration of the information reproducing apparatus 30 of the above embodiment, the state is changed at a plurality of locations with respect to one region of the predetermined region of the recording layer 4 of the laminated waveguide type three-dimensional recording medium 1 so that the recording region Is recorded, it is possible to read the condition by making the reproduction light incident from the end face of the core layer 3 in a specific direction. Further, by associating the positional relationship of the plurality of locations with the value of the multi-valued bit in advance, it is possible to reproduce the information of the multi-valued bit. If these conditions can be read out and multi-valued bits can be reproduced, the data sorting by hardware control and the access speed to the array can be improved, and the laminated waveguide type three-dimensional recording medium 1 can be used for the purpose of a library or the like. Can be used.

In the above-described embodiment, the two-photon absorption material has been described using the compound represented by the chemical formula ( 5 ) or the chemical formula ( 6 ) as an object. However, the present invention is not limited to this embodiment, and the chemical formula ( 5 ) Or a two-photon absorption material other than the compound represented by the chemical formula ( 6 ), the sensitivity wavelength also changes. Therefore, the light source used during recording and reproduction, and the power of light emitted from the light source are as described above. It is not limited to the embodiment. As a practical level, it is preferable to use a light source that emits light with a wavelength of 250 nm to 900 nm.

It is the figure which showed the structure of the laminated waveguide type three-dimensional recording medium by this embodiment. FIG. 2 is a diagram showing a configuration of a laminated waveguide type three-dimensional recording medium in which a recording layer and a core layer are integrated as an optical waveguide layer in the same embodiment. It is the figure which showed the structure of the information recording device in the embodiment. It is the figure which showed the structure of the Z-axis stage and XY-axis stage of the information recording device in the embodiment. It is the figure which showed the state where the predetermined area | region where information was recorded on the recording layer in the embodiment, and the information were recorded, and the recording area was formed. It is the figure which showed the spot of the recording light when the change by two-photon absorption has arisen in the recording layer in the embodiment, and its light quantity distribution. It is the figure which showed the structure of the information recording device by the embodiment. It is a figure for showing the characteristic of the phase plate in the embodiment. When the phase plate in the same embodiment is used, a diagram showing a spot of recording light when a change due to two-photon absorption occurs in the recording layer, and a diagram showing a light amount distribution thereof. It is the figure which showed typically the change distribution of the refractive index produced | generated in a recording layer in the case of one spot and two spots in the embodiment. It is the figure which showed the structure of the information reproducing | regenerating apparatus in the embodiment. FIG. 4 is a diagram showing a process of reproducing information from a multi-level bit-recorded laminated waveguide type three-dimensional recording medium in the same embodiment. It is the figure which showed the process of the reproduction | regeneration in the case of reading the conditions of information from the laminated waveguide type three-dimensional recording medium in the same embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laminated waveguide type three-dimensional recording medium 2 Clad layer 3 Core layer 4 Recording layer 5 Optical waveguide layer 6 Substrate 10 Information recording device 11 Shutter 12 Beam splitter 13 Lens 14 Pinhole 15 Photo detector 16 1/4 wavelength plate 17 Phase plate 18 Lens 19 Z-axis stage 20 XY-axis stage 21 Light source 30 Information reproducing device 31 Light source 32 Cylindrical lens 33 Z-axis stage 37 Microscope 38 CCD camera

Claims (11)

An optical waveguide layer for guiding light and a clad layer are provided in multiple layers. The optical waveguide layer is partially or entirely made of an optical recording material, and records information by changing the optical recording material. An information recording method for a laminated waveguide type three-dimensional recording medium comprising:
A plurality of portions of the optical recording material in a predetermined region through a phase plate that shifts the phase of a part of the light incident on each information unit recorded on each optical waveguide layer by entering light from the surface of the cladding layer Focused on
The information recording method, wherein information is recorded for each information unit by changing a plurality of locations of the optical recording material in the region of each optical waveguide layer by the condensed light. The optical recording material is composed of a two-photon absorption material represented by the following chemical formula (1) or chemical formula (2),
Information according to claim 1, characterized in that the condensed and by changing the previous SL optical recording material causing two-photon absorption in the two-photon absorbing material with light to record information for each of the information unit Recording method.

Recording information for each information unit by changing the refractive index by two-photon absorption of the two-photon absorption material,
The product of the film thickness of the recording layer and the refractive index change rate due to two-photon absorption of the two-photon absorbing material is ¼ or less of the wavelength of light incident from the end face of the optical waveguide layer during reproduction. The information recording method according to claim 1 or 2 . Wherein the information units, the information recording method according to one any of claims 1 3, characterized in that a unit of multi-value bits. When collecting light at a plurality of positions in the area, according to claim 1, characterized in that the condensed light to the plurality of positions of the positional relationship change in the amount of light that occurs at the time of reproduction becomes larger by the plurality of locations Information recording method. The phase plate is disposed in parallel with the surface of the optical waveguide layer,
The phase plate is rotated at an angle corresponding to a predetermined specific condition in the arranged plane, and light is condensed at a plurality of locations in the area of each recording layer. Item 4. The information recording method according to Item 1 . An optical waveguide layer for guiding light and a clad layer are provided in multiple layers. The optical waveguide layer is partially or entirely made of an optical recording material, and information is recorded by changes in the optical recording material. An information reproducing method for a laminated waveguide type three-dimensional recording medium,
For each of the optical waveguide layers, the planar light guided from the end face of the optical waveguide layer into the plane of the optical waveguide layer is incident,
The change in the amount of light generated in the optical recording material of the optical waveguide layer is read in two dimensions by the planar light incident on each optical waveguide layer, and the change in the read light amount is detected for each predetermined region for each information unit. Then, when there is a change in the amount of light at a plurality of locations in the region , information is reproduced for each information unit based on the positional relationship between the locations where the change in the amount of light exists . The optical recording material is a two-photon absorption material represented by the following chemical formula (3) or chemical formula (4) :
Information is recorded by the change of the two-photon absorption material due to the two-photon absorption of the two-photon absorption material,
Information reproducing method according to claim 7, characterized in that reproducing information for each of the information units is detected for each region defined in advance a change in the pre-SL read light amount for each information unit.

Wherein the information units, the information reproducing method according to any one of claims 7 8, characterized in that a unit of multi-value bits. The plane light is incident from end faces in different directions,
A change in the amount of light generated in the optical recording material is read in two dimensions by plane light incident in each direction of the end face, and the change in the read light quantity is detected for each region and correlated in advance for each direction of the end face. The information reproducing method according to any one of claims 7 to 9 , wherein the information is reproduced as information on a specific condition. The plane light waveguide to the information reproducing method according to claim 7 in any one of 10, characterized in that guided in a single mode or multimode.

Images