WO2010029608A1

WO2010029608A1 - Holographic device and recording method

Info

Publication number: WO2010029608A1
Application number: PCT/JP2008/066234
Authority: WO
Inventors: 昌和小笠原
Original assignee: パイオニア株式会社
Priority date: 2008-09-09
Filing date: 2008-09-09
Publication date: 2010-03-18

Abstract

A recording method in a holographic device which includes a holding device for movably holding a recording medium and an optical deflector for varying the crossing angle of reference light at predetermined angle intervals so as to cross both optical paths of the coherent reference light and signal light modulated by two-dimensional data according to information which should be recorded each other in the recording medium and multiplex-records the optical interference pattern of the reference light and signal light on the unit recording area of the recording medium as a hologram in a page unit for each of the angle intervals. The recording method includes a step of recording a user page containing arbitrary information which should be recorded on the unit recording area at a first angle interval and a step of spacing an address page containing address information required to access the unit recording area from the adjacent user page at a second angle interval larger than the first angle interval and recording it. The second angle interval exceeds the wobbling angle width of the surface of the recording medium.

Description

Hologram apparatus and recording method

The present invention relates to a hologram apparatus, a recording method, and a reproducing method for hologram angle multiplex recording of a hologram recording medium (hereinafter simply referred to as a recording medium) capable of recording or reproducing information by irradiating a light beam such as an optical disk or an optical card. The present invention relates to a method for recording data defining address information of an angle multiplexed hologram group (book).

A recording medium capable of recording two-dimensional data obtained by converting data to be recorded such as images and text, address information, and the like into a two-dimensional pixel pattern (page) with high density and its hologram device have attracted attention. The feature of this hologram is that the wavefront of signal light carrying two-dimensional data is recorded on a recording medium using an optical interference pattern with coherent reference light as a diffraction grating (hologram). That is, the optical paths of the reference light and the signal light are spatially separated from each other, and the two are crossed in the recording medium by the interference means to record two-dimensional data as a hologram.

In holographic recording, the angle at which the reference light intersects the signal light within the recording medium (the crossing angle, and the incidence angle when the recording medium surface is used as a reference when the signal light is irradiated perpendicularly to the surface of the recording medium) In other words, the holograms (pages) that are different for each crossing angle can be recorded in the same unit recording area by angle multiplex recording.

As shown in FIG. 1, for example, while changing the crossing angles θ1 to θm (incident angles) of the reference beams RB1 to RBm with respect to the signal beams SB1 to SBm perpendicularly incident on the surface of the recording medium 2, the recording medium 2 When performing angle multiplex recording in which a plurality of holograms are recorded in the same unit recording area, the image is stopped at the intersection angle θ1 for the time required for recording, then changed to the intersection angle θ2 and stopped, and moved to the intersection angle θ3 and stopped. Then, means for repeating the operation of sequentially writing the holograms HG1 to HGm, that is, an optical deflecting device is required. Each page includes information (page address information) for specifying the page corresponding to the incident angle of the reference light. In general, the interval of crossing angles, that is, the angle interval α is kept constant.

In general, in reproduction in hologram angle multiplex recording, since the reproduction light is received while finely adjusting the movement of the recording medium and the incident angle of the reference light, the reference light search must be repeated until address information is obtained. Random access is difficult, and it is desired to increase the data reproduction speed.

For example, in a conventional hologram device, when the crossing angle of the reference light is continuously changed in the vicinity of the searching angle with respect to the angular interval α when the crossing angle of the reference light is variably controlled during recording, the angle range Δθ is changed. There is a method of setting a value narrower than the angle interval α, that is, Δθ <α (see Patent Document 1).
JP 2007-240581 A

In the prior art of Patent Document 1, the same key page (page corresponding to the reference angle) is continuously recorded in the vicinity of the reference angle of the reference light, and fixed by degrading the angle selectivity of the key page. It has been proposed to read out the key page at the reference light incident angle.

However, when a key page search is attempted with the reference beam fixed at a certain angle, the recording medium is warped, the surface is shaken, the recording medium is reattached to the recording apparatus, the recording medium is attached to another recording apparatus, etc. If there is an angular displacement, etc., the SN ratio of the reconstructed image deteriorates due to deviation from the reference light incident angle suitable for the modulation pattern in which the address information is recorded. In some cases, crosstalk with the user page occurs. However, it is difficult to read the address information.

For example, as shown in FIG. 2, if the recording medium is constant in an ideal state, the signal light ReSB reproduced by irradiation of the reference light RB at a predetermined angle onto the recording medium can be obtained as shown in FIG. The modulation pattern MP is imaged to obtain address information. However, according to the prior art of Patent Document 1, a two-dimensional data modulation pattern of the same address information is recorded within an angle at which a predetermined angle selectivity is guaranteed. Or, when recording is continuously performed, if the modulation pattern is reproduced, a phenomenon that a plurality of holograms are overlapped in the direction of moving the reference beam of angle multiplexing due to the surface shake of the recording medium (arrow in FIG. 4) occurs. As shown in FIG. 5, the optical ReSB is shaken, and it becomes difficult to reproduce the pattern DMP with the same modulation pattern overlapped.

Therefore, the problem to be solved by the present invention is, for example, to provide a hologram apparatus and a recording / reproducing method capable of increasing the access speed and the data reproducing speed.

The recording method of the present invention includes a holding device for movably holding a recording medium, and both optical paths of coherent reference light and signal light modulated with two-dimensional data according to information to be recorded in the recording medium. And an optical deflecting device that changes the crossing angle of the reference light at a predetermined angular interval so that the optical interference pattern of the reference light and the signal light is a hologram. A recording method in a hologram apparatus for performing multiple recording in a unit recording area of a recording medium,
Recording user pages including arbitrary information to be recorded in the unit recording area at first angular intervals;
Recording an address page including address information necessary for access to the unit recording area at a second angular interval greater than the first angular interval from the adjacent user page,
The second angular interval is greater than or equal to a surface deflection angle width of the surface of the recording medium.

The reproducing method of the present invention includes a holding device that movably holds the recording medium recorded by the above-described recording method, and irradiating the reference light for each unit recording area of the recording medium to set the crossing angle of the reference light to a predetermined value. A reproducing method in a hologram apparatus that includes an optical deflecting device that changes at an angular interval and optically reproduces two-dimensional data from the recording medium,
Obtaining address information necessary for accessing the unit recording area from the address page;
Obtaining address information necessary for accessing the target page from the user page in the unit recording area at a first angle interval.

The recording apparatus of the present invention includes a holding device that holds the recording medium movably, and both optical paths of the coherent reference light and the signal light modulated with two-dimensional data according to the information to be recorded in the recording medium. An optical deflecting device that changes the crossing angle of the reference light at a predetermined angular interval so as to cross each other, wherein the optical interference pattern of the reference light and the signal light is a hologram, and the unit of the page for each angular interval. A hologram recording apparatus for performing multiplex recording in a unit recording area of a recording medium,
A user page including arbitrary information to be recorded in the unit recording area is recorded at a first angular interval, and an address page including address information necessary for accessing the unit recording area is transferred from the adjacent user page to the first page. Recording is performed with a second angular interval greater than one angular interval, and the crossing angle of the reference light is intermittently set so that the second angular interval is equal to or greater than the surface deflection angle width of the surface of the recording medium. It is characterized by comprising crossing angle control means for changing to

According to the configuration of the present invention, since the angle interval between the key page and the user page is not widened in the prior art, the hologram recording medium is warped, shaken, or remounted on the recording apparatus, mounted on another recording apparatus, etc. When the angular displacement that occurs in the above occurs, crosstalk between the address page and the user page may occur. However, since the angular interval between the address page and the user page is wide, the user page does not crosstalk.

It is a schematic fragmentary sectional view of the recording medium explaining hologram angle multiplexing recording. It is a schematic fragmentary sectional view of the recording medium explaining hologram angle multiplexing recording. It is a front view which shows the modulation pattern imaged with the signal light reproduced | regenerated from the recording medium by which the hologram angle multiplexing recording was carried out. It is a schematic fragmentary sectional view of the recording medium explaining hologram angle multiplexing recording. It is a front view which shows the modulation pattern imaged with the signal light reproduced | regenerated from the recording medium by which the hologram angle multiplexing recording was carried out. It is a block diagram which shows the outline of the hologram apparatus of embodiment by this invention. It is a top view of the recording medium of the embodiment by the present invention. It is a block diagram which shows the outline of the optical pick-up of the hologram apparatus of embodiment by this invention. It is a flowchart which shows the shift movement step in the method of embodiment by this invention. It is a flowchart which shows the angle multiplexing recording step in the method of embodiment by this invention. FIG. 3 is a schematic partial cross-sectional view of a recording medium for explaining an angle multiplex recording step in the method according to the embodiment of the present invention. FIG. 3 is a schematic partial cross-sectional view of a recording medium for explaining an angle multiplex recording step in the method according to the embodiment of the present invention. FIG. 3 is a schematic partial cross-sectional view of a recording medium for explaining an angle multiplex recording step in the method according to the embodiment of the present invention. It is a schematic fragmentary sectional view of the recording medium explaining the angle multiplexing recording step in the method of another embodiment by the present invention. It is a schematic fragmentary sectional view of the recording medium explaining the angle multiplexing recording step in the method of another embodiment by the present invention. It is a schematic fragmentary sectional view of the recording medium explaining the angle multiplexing recording step in the method of another embodiment by the present invention. 6 is a flowchart illustrating a method of reproducing from a recording medium on which angle multiplexing recording is performed in the method according to the embodiment of the present invention. It is a graph which shows the relationship between the intensity | strength of the reproduction | regeneration signal obtained at the reproduction | regeneration step of embodiment by this invention, and the reference beam incident angle for reproduction | regeneration. It is a graph which shows the relationship between the intensity | strength of the reproduction | regeneration signal obtained at the reproduction | regeneration step of other embodiment by this invention, and the reference beam incident angle for reproduction | regeneration. It is a graph which shows the relationship between the intensity | strength of the reproduction | regeneration signal obtained at the reproduction | regeneration step of other embodiment by this invention, and the reference beam incident angle for reproduction | regeneration. It is a graph which shows the relationship between the intensity | strength of the reproduction | regeneration signal obtained at the reproduction | regeneration step of other embodiment by this invention, and the reference beam incident angle for reproduction | regeneration. It is a graph which shows the relationship between the intensity | strength of the reproduction | regeneration signal obtained at the reproduction | regeneration step of other embodiment by this invention, and a recording medium rotation angle movement amount.

Explanation of symbols

2 Recording medium 22 Spindle motor 23 Pickup 24 Pickup drive unit 25 Light source drive circuit 26 Spatial light modulator drive circuit 27 Reproduction light signal detection circuit 31 Pickup position detection circuit 32 Slider servo circuit 33 Medium rotation angle detection sensor 34 Rotation position detection circuit 35 Spindle servo circuit 37 Control circuit MD Reference light deflection drive circuit 4f 4f Optical system GM Galvano mirror CL Collimator lens IS Image sensor LD Laser light source OBA First objective lens OBB Second objective lens PBS Polarization beam splitter RB Reference light SB Signal light SLM Space Light modulator

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an example of a hologram apparatus will be described as an embodiment of the present invention with reference to the drawings.

<Hologram device>
As an embodiment, a hologram apparatus for recording and reproducing information on a disk-shaped recording medium will be described. However, the present embodiment can be used in any hologram recording form without being restricted by this hologram apparatus configuration.

FIG. 6 is a block diagram of an example of a hologram device.

The hologram apparatus includes a reference light deflection drive circuit MD, a spindle motor 22 that is rotated by a turntable that detachably supports a disk of the recording medium 2, a pickup 23 that reads a signal from the recording medium 2 by a light beam, and the pickup. A pickup drive unit 24 that holds and moves in the radial direction R of the recording medium, a light source drive circuit 25, a spatial light modulator drive circuit 26, a reproduction light signal detection circuit 27, and a pickup drive unit 24 connected to the pickup drive unit 24. Pickup position detection circuit 31 that detects a signal, slider servo circuit 32 that is connected to the pickup drive unit 24 and supplies a predetermined signal thereto, and medium rotation angle detection that detects the rotation angle of a recording medium having a known optical pickup configuration The rotation of the recording medium 2 connected to the sensor 33 and the medium rotation angle detection sensor A rotational position detecting circuit 34 for generating a preamble signal, is connected to the spindle motor 22 and a spindle servo circuit 35 supplies a predetermined signal thereto.

The hologram apparatus includes a control circuit 37. The control circuit 37 includes a reference light deflection drive circuit MD, a light source drive circuit 25, a spatial light modulator drive circuit 26, a reproduction light signal detection circuit 27, a pickup position detection circuit 31, and a slider. The servo circuit 32, the medium rotation angle detection sensor 33, the rotation position detection circuit 34, and the spindle servo circuit 35 are connected. Based on the signals from these circuits, the control circuit 37 controls the radius and tangential position of the pickup via these drive circuits. The control circuit 37 is composed of a microcomputer equipped with various memories 38 and controls the entire apparatus. Various control signals are output according to the operation input by the user from the operation unit 39 and the current operation state of the apparatus. The display unit 40 is connected to the display unit 40 for generating and displaying the operation status and the like to the user. The control circuit 37 controls the hologram recording / reproducing sequence.

At the time of recording, the control circuit 37 executes processing such as encoding of data to be recorded on the hologram input from the outside, and supplies a predetermined signal to the spatial light modulator driving circuit 26. The light source drive circuit 25 connected to the hologram recording / reproducing laser light source LD adjusts the output of the laser light source LD so that the intensity of both emitted light beams is strong during hologram recording and weak during reproduction.

The control circuit 37 controls to form hologram unit recording areas at predetermined intervals so that holograms to be recorded can be recorded at predetermined intervals (multiple intervals), and so as to record at predetermined angular intervals in the unit recording areas. Control various elements.

At the time of reproduction, the control circuit 37 performs demodulation and error correction processing based on the signal from the reproduction optical signal detection circuit 27 connected to the image sensor mounted on the pickup 23, and is recorded on the recording medium 2 Control various elements to restore dimensional data. Further, the control circuit 37 performs a decoding process on the restored data and outputs reproduced data.

The control circuit 37 generates a slider drive signal based on the position signal from the operation unit or the pickup position detection circuit 31, and supplies this to the slider servo circuit 32. The slider servo circuit 32 moves the pickup 23 in the radial direction of the disk via the pickup drive unit 24 in accordance with the drive current generated by the slider drive signal.

In common with recording and reproduction, the medium rotation angle detection sensor 33 detects a detection mark DM (see FIG. 7) attached to the inner peripheral side of the recording medium 2 and supplies the output to the rotation position detection circuit 34. . The rotational position detection circuit 34 generates a rotational position signal and supplies it to the control circuit 37. The control circuit 37 determines the position of the unit recording area in the track direction from the rotation position signal. The control circuit 37 generates a spindle drive signal, supplies it to the spindle servo circuit 35, controls the spindle motor 22, and rotates the recording medium 2.

The reference light deflection drive circuit MD controls a later-described light deflecting device mounted on the pickup 23 so that the reference light is recorded on the signal light modulated by two-dimensional data according to the information to be recorded. The crossing angle of the reference light is changed at a predetermined angular interval so as to cross each other.

Thus, the hologram formation time can be secured with the relative position of the light spot relative to the moving recording medium at the time of recording, and the position and angle of the reference light at the time of reproduction can be determined.

The recording medium 2 to which the rotation angle detection mark DM is attached is, for example, a translucent material that can store an optical interference pattern such as a photopolymer, a photo-anisotropic material, a photorefractive material, a hole burning material, or a photochromic material. A light-sensitive material is used, and both sides are covered with a protective layer. The mark DM for detecting the rotation angle is formed on the surface or interface of the protective layer by, for example, printing or transferring pits or the like like an optical disk such as a CD.

<Optical pickup>
FIG. 8 shows a schematic configuration of the pickup 23. However, this embodiment can be used in any hologram recording form without being restricted by these pickup configurations. The pickup 23 includes a recording optical system and a reproducing optical system, and these are arranged in a housing.

The pickup includes a laser light source LD connected to the light source driving circuit 25, a collimator lens CL, a half mirror prism HP, a polarization beam splitter PBS, a reflective spatial light modulator SLM connected to the spatial light modulator driving circuit 26, a first one. 1 objective lens OBA, signal light aperture SAP, second objective lens OBB, image sensor IS connected to reproduction light signal detection circuit 27, reference light aperture RAP, and light deflection apparatus 10 connected to reference light deflection drive circuit MD ( The galvanometer mirror GM is composed of a 4f optical system 4f) composed of a pair of coaxial irradiation lenses.

The signal optical system of the recording optical system includes a laser light source LD, a collimator lens CL, a half mirror prism HP, a polarizing beam splitter PBS, a reflective spatial light modulator SLM, and a first objective lens OBA.

The reference optical system of the recording optical system includes a laser light source LD, a collimator lens CL, a half mirror prism HP, a reference light aperture RAP, and a light deflecting device 10.

The reproduction optical system includes a reference optical system common to the recording optical system (laser light source LD, collimator lens CL, half mirror prism HP, reference light aperture RAP, and light deflector 10), a second objective lens OBB, an image sensor IS, Includes a signal light aperture SAP.

The wavelength of the laser light source LD is a wavelength at which a translucent photosensitive material capable of preserving the optical interference pattern of the recording medium 2 reacts. The collimator lens CL has a collimating function for converting coherent light diverging from the laser light source LD into parallel light. The half mirror prism HP generates a light beam for reference light and signal light by separating the light from the parallel light in the direction.

The pair of first objective lens OBA and second objective lens OBB are arranged on a straight line so that their focal points coincide with each other. The common focus of the pair of objective lenses OBA and OBB is removed, and the recording medium 2 is disposed on the first objective lens OBA side in the vicinity thereof. With a pinhole at the common focus, the signal light aperture SAP functions as an aperture.

The reflective spatial light modulator SLM has a function of electrically transmitting incident light for each pixel in a reflective liquid crystal panel having a plurality of pixel electrodes divided in a matrix. The spatial light modulator SLM modulates the light beam so as to have a distribution based on page data to be recorded from the spatial light modulator driving circuit 26 (information pattern of two-dimensional data such as a bright and dark dot pattern on a plane). Signal light is generated. Also, it has a shutter function that does not reflect all the signal light at the time of reproduction according to the signal from the spatial light modulator driving circuit 26. As an example of a reflective spatial light modulator, a DMD (Digital Micromirror Device) (registered trademark) having a matrix of a plurality of pixel mirrors can be used. The DMD parallels a part of incident light for each pixel mirror. It has a spatial modulation function of deflecting, and only the necessary spatially modulated signal light can be supplied to the first objective lens OBA by electrical control. In the case where a spatial light modulator of a transmissive liquid crystal panel is used, a transmissive spatial light modulator may be disposed between the mirror and the first objective lens OB by disposing a mirror at the position of the polarization beam splitter PBS. it can.

The image sensor IS is composed of an array such as a charge coupled device (CCD) and a complementary metal oxide semiconductor device (CMOS).

<Optical deflection device>
As an optical system for reference light, as shown in FIG. 8, the reference light aperture RAP has an axial opening, and the axial opening restricts the input light beam to be converted into an appropriate diameter to generate the reference light RB.

The galvanometer mirror GM is driven by a reference light deflection drive circuit MD that controls an actuator that drives the rotating shaft. For example, a galvano mirror GM driven by a stepping motor is rotated at a constant angular interval by the reference light deflection drive circuit MD. In this embodiment, the reference light deflection drive circuit MD can perform fine adjustment by changing the reference light incident angle by a minute angle interval with the galvanometer mirror GM.

The 4f optical system 4f is a telecentric optical system having a confocal lens configuration, and the focal planes at both ends are in an image-forming relationship between an object and an image. The recording medium 2 is arranged at the lens focal point (conjugate point) at the other end. Therefore, in the 4f optical system, light reflected in any direction from the galvanometer mirror GM is guided to a specific point on the recording medium (a conjugate point on the optical axis). As described above, the optical deflecting device is a mechanism that deflects the reference light irradiated to the recording medium for changing the irradiation angle of the reference light around the recording position of the hologram when performing angle multiplexing recording of the hologram. is there. Although the figure shows the 4f optical system in the case where the focal lengths are equal as an example, the present invention is not limited to this, and other optical deflecting devices can be used as long as the mechanism changes the angle of the reference light irradiated onto the recording medium.

<Hologram device operation>
The schematic operation of the hologram apparatus will be described with reference to FIG.

In the recording process, as shown in FIG. 8A, the coherent light beam emitted from the laser light source LD becomes parallel light by the collimator lens CL, and is separated into reference light and signal light by the half mirror prism HP.

The signal light beam is reflected by the half mirror prism HP, passes through the polarization beam splitter PBS, and enters the spatial light modulator SLM displaying a modulation pattern by a signal from the spatial light modulator drive circuit 26. In the spatial light modulator SLM, the incident light is spatially modulated to generate and reflect the signal light SB. The signal light SB returns to the polarization beam splitter PBS, and the signal light SB is reflected to the first objective lens OBA. The signal light SB is collected by the first objective lens OBA and enters the recording medium 2.

The light beam for reference light passes through the half mirror prism HP, is then aperture-limited by the reference light aperture RAP, becomes reference light RB, and enters the galvanometer mirror GM. The reference light RB deflected by the galvanometer mirror GM crosses the signal light SB collected by the first objective lens OBA at a certain point (unit recording area) in the recording medium 2 through the 4f optical system 4f. By this operation, an optical interference pattern is generated in the recording medium 2 and a hologram is recorded.

In the reproduction process, as shown in FIG. 8B, all the spatial light modulators SLM are set in a transmission state so that the signal light is not reflected on the first objective lens OBA and is not incident on the recording medium 2. The reference light RB is incident on the galvanometer mirror GM and the 4f optical system 4f in the same manner as in recording, and only the reference light RB is selected with a deflection angle and incident on the recording medium 2. Only the hologram corresponding to the intersection angle selected by the reference beam RB irradiation is reproduced. The reproduced signal light ReSB from the reproduced hologram is imaged on the image sensor IS by the second objective lens OBB. The reproduced image is read by the reproduction optical signal detection circuit 27, and the recorded signal is reproduced.

The hologram apparatus controls the rotation of the recording medium so that a plurality of unit recording areas to be recorded can be sequentially recorded and reproduced at a predetermined interval (shift multiplex interval in the track direction T) in each of the recording and reproducing steps. Control is performed so that angle multiplex recording can be performed at predetermined angle intervals in units of pages in each recording area.

<Shift movement>
Since the shift movement operation is performed before and after the angle multiplex recording for each unit recording area in the hologram apparatus of the embodiment, this will be briefly described first.

For example, the shift movement step is performed according to the flowchart shown in FIG.

First, as shown in FIGS. 8 and 9, the recording medium 2 is inserted and fixed to the spindle of the hologram apparatus. Thereafter, the target incident angle of the reference light is fixed (the optical deflecting device is stopped) according to the target address instruction by the data recording (or reproduction) command from the control circuit 37 (step S1), and the medium rotation angle detection sensor 33 is set. Is started (step S2), the recording medium 2 is rotated to the target angular position of the target address information in the recording medium 2, and stopped there (step S3). Next, the pickup position detection circuit 31 and the slider servo circuit 32 are activated, and the pickup 23 is moved in the radial direction R to the target radial position on the recording medium 2 of the target address information (step S4), and stops there (step S4). Shift movement). Here, if the target address information is already recorded on the page, after the shift movement, only the reference light is irradiated with reduced intensity, and if the address information can be read from the current page, the address information is verified. If it cannot be read, fine adjustment is performed for each of the rotation of the recording medium and the movement of the pickup, and the process of re-reading by reference light irradiation and re-checking of the address information is repeated repeatedly to complete the address information verification. Inspection can also be performed (inspection process).

After the shift movement, an angle multiplexing recording or reproducing process is executed in the unit recording area at the target position (step S5). Then, the continuation or end of the angle multiplexing recording or reproduction process is determined (step S6). If it is continued, the process returns to step S2, another target address instruction is given, and if the recording is finished, the process is ended.

These shift movement and angle multiplexing steps are sequentially performed, and the unit recording areas to be recorded are repeated so as to overlap at a predetermined interval, thereby forming a plurality of unit recording areas (shift multiplex recording) in the track direction T.

For example, as shown in FIG. 7, a plurality of unit recording areas, so-called books (portions indicated by ◯) are aligned at predetermined intervals on a track (broken line) of the recording medium 2. Further, a plurality of books adjacent to each other, for example, BS1 is grouped as a group (shelf) and further divided into BS2, BS3, BS4 and shelves, and as address information, for example, in each recording medium of shelves BS1 to BS4 It can be recorded on a representative address page in a book at a specific rotation angle and radial position (shelf address information). This specific address page is also recorded at a specific angular position in the book. The address page can record a specific rotation angle and a radial position in each recording medium of the book (unit recording area) (book address information). Of course, information specifying the page corresponding to the incident angle of the reference beam RB in the unit recording area can be recorded on the address page (page address information). As described above, the address information includes the position information of the rotation angle position and the radial position (track position) on the recording medium disc, and the page address information for specifying the page corresponding to the incident angle of the reference light RB in the unit recording area. Is included.

In addition to the address page, in the recording medium, arbitrary information such as an image and text to be recorded in the unit recording area is recorded as a user page at a predetermined angular position in the book. The user page also includes at least page address information. In addition, index information (index page) such as what data is recorded on which book and which page is recorded on the recording medium.

Thus, the address page includes a modulation pattern including address information necessary for accessing the unit recording area. Note that arbitrary information such as images and text can also be included in the modulation pattern as a user area in the address page.

<Angle multiplexing process: recording>
First, as an example of angle multiplexing recording in the angle multiplexing step (step S5) of the hologram device, an amount of recording that sufficiently exceeds the capacity of the unit recording area by continuing one address page in the blank unit recording area of the recording medium. The case of recording a series of user pages will be described with reference to the flowchart shown in FIG.

In the initial shift movement, the reference beam deflection drive circuit MD controls the deflection angle of the galvanometer mirror GM, and the incident angle of the reference beam RB is set to the specified angle θn (for example, the initial value of the first page of the book). The reference light RB and the recording light SB are not irradiated to the designated recording area C.

After the light irradiation position of the pickup is determined in the unit recording area at the target position, the spatial light modulator driving circuit controls the spatial light modulator SLM, the address page modulation pattern is displayed on it, and the light source is turned on. As shown in FIG. 11, both optical paths of the reference light RB and the recording light SB intersect the designated recording area C in the recording medium 2 (step S11), and are in a relatively stationary state. As a result, an address page hologram corresponding to the designated angle θn is formed in the designated recording area C, and this address information is recorded. Here, after data recording, the signal light is blocked and the intensity of only the reference light is reduced and irradiated to reproduce the data from the current address page, and check whether there is an error in the reproduced data. (Inspection process)

Next, as shown in FIG. 12, the reference beam deflection drive circuit MD changes the deflection angle of the galvanometer mirror GM to set the incident angle of the reference beam RB to a predetermined angle θn + 1, that is, from the angular position of the address page. The light RB is rotated by a predetermined address page angle interval ts (step S12), and the display of the spatial light modulator is controlled to be switched to the modulation pattern of the user page, so as to be relatively stationary. As a result, a hologram of a user page corresponding to the designated angle θn + 1 is formed in the designated recording area C.

Next, as shown in FIG. 13, the reference beam deflection drive circuit MD changes the deflection angle of the galvanometer mirror GM, and rotates the reference beam RB from the angular position of the first user page by the next user page angle interval td. (Step S13), and control for switching the display of the spatial light modulator to the modulation pattern of the next user page is performed to make the state relatively stationary. As a result, the hologram of the next user page is formed in the designated recording area C.

Thereafter, the user page recording process is repeated until the total angle interval ts of the reference light RB reaches the maximum angle θM (capacity), whereby a plurality of user pages are sequentially recorded in one book. That is, it is determined whether or not the incident angle of the reference light RB is the maximum angle (step S14). If it is not the maximum angle θM, the process returns to step S13, and if it is the maximum angle, the process ends.

In this embodiment, in a recording method in a hologram apparatus that multiplex-records in a unit recording area of a recording medium in units of pages for each angular interval, a plurality of user pages including arbitrary information to be recorded in the unit recording area are set as user page angular intervals td. While recording at (first angular interval), an address page (θn) including address information necessary for accessing the unit recording area is an address page larger than the user page angular interval td from the adjacent user page (θn + 1). Recording is performed at an angular interval ts (second angular interval). Here, it should be noted that, as shown in FIG. 13, the address page angle interval ts is preferably set to be equal to or greater than the surface deflection angle width Wv of the surface of the recording medium. This is to avoid the influence of the surface shake of the recording medium due to the overlap between the address page and the user page at the time of reading. As a result, it is possible to prevent the SN ratio of the reproduced image from being deteriorated and to prevent crosstalk between the two, and the address information can be reliably read out. Here, the surface deflection angle width of the surface of the recording medium is a width obtained by converting the moving distance before and after the surface deflection of the reproduced image formed on the light receiving surface of the image sensor into the accuracy of the incident angle of the reference light by the optical deflector.

Also, the user page angle interval td need not be a constant angle (the address page and the adjacent data page only need to be separated).

Further, it is preferable that the address page is recorded within the address page allowable angle range VR around a predetermined angle θn which is equal to or smaller than the surface deflection angle width Wv of the surface of the recording medium. This is to avoid the influence of the surface shake of the recording medium of the address page itself at the time of reading.

In this embodiment, the address page is recorded at the top of the group of user pages. However, in another modification, the user page is recorded at the top and then the address page is recorded. It can also be recorded between user pages. The address page can also be recorded after the last page of the group of user pages.

As yet another modification, for example, as shown in FIG. 7, in a group (shelf) of unit recording areas, address information necessary for accessing each unit recording area is recorded on a representative address page, The crossing angle of the reference light for recording the address page may be different from the crossing angle of the reference light for recording the user page, and the crossing angle of the reference light for recording the representative address pages may be the same. Thereby, the search for each group (shelf) of the unit recording area can be speeded up.

In this embodiment, only one address page is recorded in one unit recording area (book). However, the present invention is not limited to this, and a plurality of address pages are recorded in one unit recording area (book). You can also For example, as shown in FIG. 14, the second address page can be recorded in the same book at the position of the separate address page incident designated angle θx in addition to the address page incident designated angle θn of the reference light RB. As a result, the page address information in the book can be further finely divided, so that the target page in the book can be searched.

Furthermore, the address page can be recorded so that the crossing angle of the reference beam is different for each unit recording area. Thereby, the search for each unit recording area can be speeded up. For example, as shown in FIG. 15, in the same recording medium 2, in addition to the address page incidence designation angle θn of the reference light RB in one unit recording area C, the address page incidence designation angle θy in a separate unit recording area Cy. The address page can be recorded at the position. Of course, it is also possible to record in a separate unit recording area Cy at the address page incident designated angle θn.

As still another modification, for example, as shown in FIG. 16, three address pages can be recorded as a group of adjacent address pages. In this case, the address information of a plurality of address pages in the address page group is the same data, and the third angular interval in which the interval between adjacent address pages is smaller than the user page angular interval td within the address page allowable angle range VR. Recorded in ta. Since the address page allowable angle range VR is equal to or smaller than the surface deflection angle width Wv of the surface of the recording medium, the third angle interval ta is also equal to or smaller than the surface deflection angle width Wv and is arranged around the predetermined angle θn of the address page. It is preferable.

That is, the reference light deflection drive circuit MD shown in FIG. 6 changes the deflection angle of the galvanometer mirror GM shown in FIG. 8 and intermittently in the angle range of 2 · ta including the specified angle θn with respect to the incident angle of the reference light RB. To change. While the incident angle of the reference light RB is changed by the third angle range ta and is stationary, the reference light RB and the recording light SB are continuously applied to the designated recording area C. At this time, the recording light SB is modulated into light having a modulation pattern including the same address information by the spatial light modulator SLM. According to this, a plurality of the same address pages are recorded closer to the user page interval. When reproducing the address page group, reproduced signal light can be obtained even if there is a deviation from the incident angle θn of the reference light to some extent. Therefore, for example, when searching for an address page with an incident angle θn, it can be read at high speed.

<Angle multiplexing process: regeneration>
Next, as an example of the angle multiplexing reproduction in the angle multiplexing step (step S5) of the hologram device, a specific user page reproduction is performed in which a user page is recorded in the unit recording area of the recording medium, followed by one address page. The case will be described with reference to the flowchart shown in FIG.

In response to a target address instruction (for example, book address and page address) by a data reproduction command from the control circuit 37, the address page of the target book (unit recording area) is reached by the initial shift movement as described in FIG. At this point, the reference light deflection drive circuit MD controls the deflection angle of the galvanometer mirror GM according to the target address information, thereby changing the incident angle of the reference light RB by a constant angle (ts, td) (step S21). Here, based on the read page address information, the control circuit 37 calculates the incident angle from the currently accessed address page to the read start user page, and the reference light deflection drive circuit MD sets the deflection angle of the galvanometer mirror GM. Control is performed so as to change by a predetermined interval. Thus, in the book, if the incident angle of the reference beam RB is within a certain range with respect to the designated angle at the time of recording, the reproduction signal beam ReSB having sufficient luminance corresponding to the address page is generated. Thereby, the image sensor IS receives the reproduction signal light ReSB corresponding to the page by the image sensor IS, and transmits data to the control circuit 37 via the reproduction light signal detection circuit 27 based on the light reception signal from now on (step). S22). Here, the control circuit 37 performs address information collation between the target address information and the acquired page address (already recorded) (step S23), and if it cannot be read, the reference light deflection drive circuit MD causes the galvanomirror GM. If the fine adjustment is performed to change the reference light incident angle by a minute angle interval (step S24), the process of re-reading by reference light irradiation and the re-checking of the address information is repeated to complete the address information verification. Page reading is started (step S25).

Thereafter, the control circuit 37 determines whether or not the currently accessed user page is the last user page to be reproduced based on the acquired page address information. In the case of the last user page, the control circuit 37 A series of playback processing is completed.

FIG. 18 shows the relationship between the intensity of the reproduction signal obtained in the reproduction step and the incident angle of the reference light for reproduction. As shown in the figure, the address page angle interval ts between the address page (θn) and its adjacent user page (θn + 1) is set wider than a predetermined user page angle interval td for recording the user page (ts> td). Further, since the address page angle interval ts is larger than the surface shake value Wv, the reproduction light signal detection circuit 27 addresses the address data recorded on the user page based on the light reception signal from the image sensor IS. It can be reliably played from the page.

FIG. 19 shows the reproduction signal intensity and reproduction reference light incident angle obtained in the reproduction step of the modification shown in FIG. 16 (when address pages are recorded as a group of three adjacent address pages instead of one). Shows the relationship. According to this, since the address page is recorded with the same three address pages as a group at the third angular interval ta smaller than the surface wobbling angle width Wv, as shown in the figure, it is more than the reproduction signal intensity of the user page. It can be seen that the reproduction signal strength of a large address page can be obtained. As a result, as an effect of the present embodiment, one-dimensional address data can be read even if crosstalk, and the address data can be reproduced with substantially the same signal intensity in the surface shake range.

FIG. 20 is a combination of the modification example shown in FIG. 16 and the modification example shown in FIG. 14, and the second address at the position of the separate address page incidence designation angle θx in addition to the address page incidence designation angle θn of the reference light RB. The relationship between the intensity | strength of the reproduction | regeneration signal obtained at the said reproduction | regeneration step at the time of recording a page in the same one book, and the reproduction reference light incident angle is shown. As a result, the page address information in the book can be further finely divided, so that the target page in the book can be searched.

FIG. 21 shows a combination of the modification shown in FIG. 16 and the modification shown in FIG. 15, and separately assigns the address page incident designation angle θn of the reference light RB to the unit recording area C of the book A within the same recording medium. The relationship between the intensity of the reproduction signal obtained in the above reproduction step and the reproduction reference light incident angle when the address page is recorded at the position of the address page incidence designated angle θy in the unit recording area Cy of the book B of FIG. As a result, since the address page is recorded at a different reference light incident angle position for each book, for example, only the first book A in a data unit in which a plurality of books are clustered (book shelf) has different reference light incident angles at different reference light incident angles. Since the address reproduction signal is not reproduced at the reference light incident angle of book B, it can be seen that high-speed search of the target page only in book A is possible.

<Search method>
An example is shown as a search method. For example, if the reference light incident angles (at the time of recording) on the address pages of all books (at least the same track) are set to be the same in the recording medium 2 on which the shelves BS1 to BS4 are recorded on the track shown in FIG. When searching the book address information of both shelves in the shelves BS1 and BS3 on the same track, the target book address information can be acquired at high speed by rotating the recording medium. For example, FIG. 22 shows such a case (when the reference light incident angles of the address page A of the first book A of the shelf BS1 and the address page B of the first book B of the BS3 are the same and different from the reference light incident angles of other pages). FIG. 18 shows the relationship between the reproduction signal intensity obtained in the reproduction step described with reference to FIGS. 9 and 17 and the amount of movement of the recording medium rotation angle. In FIG. 22, ss represents the distance between the first book A on the shelf BS1 and the first book B on the BS3, and bs represents the shift multiplex distance between adjacent books. Since the address page reference light incident angle in which the address information is recorded is different from the user page reference light incident angle, the user page signal is not reproduced even when the address page recording angle is used during the search. The ratio is improved. As can be seen from FIG. 22, since the user page data is not reproduced at the address page reference light incident angles of the books A and B, the high-speed search of the target page only in the books A and B is possible.

Claims

A holding device for movably holding the recording medium, and the optical path of the coherent reference light and the signal light modulated by the two-dimensional data according to the information to be recorded intersecting in the recording medium, Including a light deflecting device that changes a crossing angle of the reference light at a predetermined angular interval, and using the optical interference pattern of the reference light and the signal light as a hologram in a unit recording area of the recording medium in units of pages at each angular interval A recording method in a hologram apparatus for multiplex recording,
Recording user pages including arbitrary information to be recorded in the unit recording area at first angular intervals;
Recording an address page including address information necessary for access to the unit recording area at a second angular interval greater than the first angular interval from the adjacent user page,
The recording method according to claim 1, wherein the second angular interval is equal to or greater than a surface deflection angle width of the surface of the recording medium.
2. The recording method according to claim 1, wherein the address page is recorded within an angle range equal to or smaller than a surface deflection angle width of the surface of the recording medium.
3. The recording method according to claim 1, wherein the address page is recorded by being sandwiched between groups of the user pages.
3. The recording method according to claim 1, wherein the address page is recorded at a head of the group of user pages.
In each of the plurality of unit recording areas, each of the address pages is a representative address page including address information necessary for accessing any one of the unit recording areas in the group consisting of the plurality of unit recording areas, and the representative page The crossing angle of the reference light that records the address page is different from the crossing angle of the reference light that records the user page, and the crossing angle of the reference light that records the representative address pages is the same. The recording method according to any one of claims 1 to 4, characterized in that:
6. The recording method according to claim 1, wherein a plurality of the address pages are recorded in one of the unit recording areas.
7. The recording method according to claim 1, wherein the address page is recorded so that an intersection angle of the reference light is different for each unit recording area.
The address page is recorded as a group of address pages adjacent to each other at a third angle interval in which a plurality of address pages having the same address information within the angle range are smaller than the first angle interval. The recording method according to any one of claims 1 to 7.
A holding device that movably holds a recording medium recorded by the recording method according to any one of claims 1 to 8, and a crossing angle of the reference light by irradiating reference light to each unit recording area of the recording medium Including a light deflecting device that changes at predetermined angular intervals, and a reproducing method in a hologram device that optically reproduces two-dimensional data from the recording medium,
Obtaining address information necessary for accessing the unit recording area from the address page;
Obtaining from the user page of the unit recording area address information necessary for accessing the target page at a first angular interval.
A holding device for movably holding the recording medium, and the optical path of the coherent reference light and the signal light modulated by the two-dimensional data according to the information to be recorded intersecting in the recording medium, Including a light deflecting device that changes a crossing angle of the reference light at a predetermined angular interval, and using the optical interference pattern of the reference light and the signal light as a hologram in a unit recording area of the recording medium in units of pages at each angular interval A hologram recording apparatus for performing multiple recording,
A user page including arbitrary information to be recorded in the unit recording area is recorded at a first angular interval, and an address page including address information necessary for accessing the unit recording area is transferred from the adjacent user page to the first page. Recording is performed with a second angular interval greater than one angular interval, and the crossing angle of the reference light is intermittently set so that the second angular interval is equal to or greater than the surface deflection angle width of the surface of the recording medium. A recording apparatus comprising crossing angle control means for changing the angle.
The recording apparatus according to claim 10, wherein the address page is recorded within an angle range equal to or smaller than a surface deflection angle width of a surface of the recording medium.
The recording apparatus according to any one of claims 10 to 11, wherein the address page is recorded by being sandwiched between groups of the user pages.
12. The recording apparatus according to claim 10, wherein the address page is recorded at the head of the group of user pages.
In each of the plurality of unit recording areas, each of the address pages is a representative address page including address information necessary for accessing any one of the unit recording areas in the group consisting of the plurality of unit recording areas, and the representative page The crossing angle of the reference light that records the address page is different from the crossing angle of the reference light that records the user page, and the crossing angle of the reference light that records the representative address pages is the same. The recording apparatus according to any one of claims 10 to 13, characterized in that:
15. The recording apparatus according to claim 10, wherein a plurality of the address pages are recorded in one of the unit recording areas.
16. The recording apparatus according to claim 10, wherein the address page is recorded so that an intersection angle of the reference light is different for each unit recording area.
The address page is recorded as a group of address pages adjacent to each other at a third angle interval in which a plurality of address pages having the same address information within the angle range are smaller than the first angle interval. The recording apparatus according to any one of claims 10 to 16.