WO2016017020A1

WO2016017020A1 - Optical-information recording and reproducing method and optical-information recording and reproducing device

Info

Publication number: WO2016017020A1
Application number: PCT/JP2014/070297
Authority: WO
Inventors: 充永沢; 伸郎中井; 嶋田　堅一; 利樹石井; 和良山崎
Original assignee: 日立コンシューマエレクトロニクス株式会社
Priority date: 2014-08-01
Filing date: 2014-08-01
Publication date: 2016-02-04

Abstract

Provided is a holographic optical-information recording and reproducing device and optical-information recording and reproducing method capable of increasing recording capacity with a simple configuration. An example of the solution is an optical-information recording and reproducing method characterized by including: a first recording step for forming a first hologram at a predetermined position in an optical-information recording medium using the interference between a first signal beam and a first reference beam; and a second recording step for forming a second hologram adjacent to the first hologram using the interference between a second signal beam and a second reference beam. The method is also characterized in that, in the first recording step or the second recording step, the first beam waist of the first signal beam in the first hologram and the second beam waist of the second signal beam in the second hologram are made to overlap each other by a predetermined amount in a beam-waist plane in the optical-information recording medium, and the incident angle of the first reference beam when forming the first hologram and the incident angle of the second reference beam when forming the second hologram are made to deviate from each other by a predetermined amount.

Description

Optical information recording / reproducing method, optical information recording / reproducing apparatus

The present invention relates to an optical information recording / reproducing method and an optical information recording / reproducing apparatus for recording information on an optical information recording medium using an interference pattern of signal light and reference light as page data and reproducing information from the optical information recording medium.

As a technique for increasing the recording capacity of the hologram recording / reproducing apparatus, there is, for example, Japanese Patent Application Laid-Open No. 2007-293309 (Patent Document 1). In this publication, the problem is that "the recording area is partially overlapped to increase the recording density of the optical information, and the adjacent reproduction light reproduced in the area adjacent to the selected recording area is used as the servo control light. The structure of the apparatus is simplified, and the angle out of the limit angle is changed to an angle within the limit angle range, and the reference light is irradiated to increase the storage efficiency of the optical information storage medium. ” As a solution, “the optical information processing apparatus, the optical information servo control method, the optical information recording method, and the optical information reproducing method according to the present invention are configured to output optical information at a multiplexing angle having a different offset angle for each track when optical information is recorded. Multiplex recording and reproduction, and the multiplexing angle outside the limit angle is changed to an angle within the limit angle range, and multiple recording and reproduction are performed, and servo control is performed using reproduction light of different tracks that are reproduced together. . Has been described as ".

Further, JP 2009-87448 A (Patent Document 2) states that “a set of incident angles of a reference beam on a disk when a hologram is recorded by an angle multiplex recording method is represented by {θ} = [θ1, θ2,. .., ΘM] indicates that the incident angle {θ} of the reference light is switched according to the position on the optical information recording medium 1 or the track position.

Further, WO2009 / 054044 (Patent Document 3) states that “the hologram recording device provided by the present invention uses an objective lens> for recording light modulated according to information to be recorded by a spatial light modulator. Recording light irradiating means for irradiating the recording medium through the recording medium, recording reference light irradiating means for irradiating the recording light to interfere with the recording light and forming a hologram recording area on the recording medium, and the recording area Irradiation position displacement means for relatively displacing the irradiation positions of the recording light and the reference light with respect to the recording medium so as to be formed side by side in the direction, and the objective lens is A lens that converges both the on-axis light beam and the off-axis light beam while converging the recording light as a whole. The recording light is converged so as to form a beam waist, and the irradiation position displacing means includes the recording light and the recording light so that portions corresponding to the beam waist in the recording area overlap in adjacent recording areas. The irradiation position of the reference light is displaced. ”

JP 2007-293309 A JP 2009-87448 A WO2009 / 054044

In holographic recording technology, in order to increase the recording capacity with a recording medium of a finite size, it is necessary to achieve high density by recording the holograms close to each other. In the technique described in Patent Document 1, when recording holograms close to each other, the reference light is incident at different offset angles for each track, thereby reducing the amount of reproduction light emitted from adjacent holograms during reproduction. However, since the configuration of Patent Document 1 separates the reproduction light of the selected hologram and the reproduction light of the adjacent hologram with a filter, the holograms are separated from each other on the beam waist surface most narrowed down on the recording medium. Yes. Therefore, there is a problem that it is disadvantageous from the viewpoint of increasing the capacity. Similarly to Patent Document 1, Patent Document 2 is disadvantageous from the viewpoint of increasing the capacity because the holograms are formed separately on the beam waist surface.

In the technique described in Patent Document 3, recording is performed so that adjacent holograms overlap at the beam waist by using an objective lens that converges signal light both on and off the axis. However, the configuration of Patent Document 3 has a problem that the signal performance is likely to be deteriorated because the sensitivity to the relative positional deviation between the medium and the optical system is high.

The present invention has been made in view of the above problems, and in an optical information recording / reproducing apparatus using a hologram, an optical information recording / reproducing method and an optical information recording / reproducing method capable of increasing the recording capacity with a simple configuration. An object is to provide an apparatus.

The above problem is solved by, for example, the invention described in the scope of claims. The present application includes a plurality of means for solving the above-mentioned problems. To give an example, the beam waists of signal lights in adjacent holograms overlap each other on the beam waist surface by a predetermined amount, and the adjacent holograms The incident angles of the reference light are shifted from each other by a predetermined amount.

According to the present invention, an optical information recording / reproducing apparatus and an optical information recording / reproducing apparatus capable of increasing the recording capacity with a simple configuration in an optical information recording / reproducing apparatus using a hologram can be provided. .

Schematic diagram showing an embodiment of an optical information recording / reproducing apparatus Schematic showing an example of the recording principle of a pickup in an optical information recording / reproducing apparatus Schematic showing an example of the reproduction principle of a pickup in an optical information recording / reproducing apparatus Schematic showing the operation flow from the insertion of the optical information recording medium of the optical information recording / reproducing apparatus to the completion of preparation for recording or reproduction Schematic showing the operation flow from the ready state of the optical information recording / reproducing apparatus to recording information on the optical information recording medium Schematic showing the operation flow from the ready state of the optical information recording / reproducing apparatus to the reproduction of information recorded on the optical information recording medium Schematic showing the overlap of signal light and reference light incident on an optical information recording medium Schematic diagram showing the positional relationship of a book recorded by a conventional optical information recording / reproducing apparatus and the progress of reproduction light when reproducing the book Schematic showing the positional relationship of the book recorded with the optical information recording / reproducing apparatus in a present Example. Schematic representing a hologram formed by a pixel of a spatial light modulator entering an optical information recording medium Schematic showing the relationship between the incident angle of signal light and reference light in an optical information recording medium Schematic showing the relationship between reference beam angle deviation during recording and playback and diffraction efficiency of playback light Schematic diagram showing in detail the positional relationship of books recorded by the optical information recording / reproducing apparatus in the present embodiment Schematic showing the hologram recording method in a present Example Schematic showing progress of reproduction light when reproducing a book with the optical information recording / reproducing apparatus of the present embodiment Schematic diagram showing hologram recording when angle multiplex recording is performed by changing the incident angle of the reference beam Schematic showing a recording method for recording one book with a predetermined amount shifted by page so as to suppress consumption of the M number Schematic showing the flow which records information on the optical information recording medium of the optical information recording / reproducing apparatus in a present Example Schematic showing the flow which records information on the optical information recording medium of the optical information recording / reproducing apparatus in a present Example

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a block diagram showing a recording / reproducing apparatus of an optical information recording medium for recording and / or reproducing digital information using holography.

The optical information recording / reproducing device 10 is connected to an external control device 91 via an input / output control circuit 90. In the case of recording, the optical information recording / reproducing apparatus 10 receives the information signal to be recorded from the external control device 91 by the input / output control circuit 90. When reproducing, the optical information recording / reproducing apparatus 10 transmits the reproduced information signal to the external control apparatus 91 by the input / output control circuit 90.

The optical information recording / reproducing apparatus 10 includes a pickup 11, a reproduction reference light optical system 12, a cure optical system 13, a disk rotation angle detection optical system 14, and a rotation motor 50. The optical information recording medium 1 is a rotation motor. 50 can be rotated.

The pickup 11 plays a role of irradiating the optical information recording medium 1 with reference light and signal light and recording digital information on the recording medium using holography. At this time, the information signal to be recorded is sent by the controller 89 to the spatial light modulator in the pickup 11 via the signal generation circuit 86, and the signal light is modulated by the spatial light modulator.

When reproducing the information recorded on the optical information recording medium 1, the reproduction reference light optical system 12 generates a light wave that causes the reference light emitted from the pickup 11 to enter the optical information recording medium in a direction opposite to that during recording. Generate. Reproduction light reproduced by the reproduction reference light is detected by a photodetector (to be described later) in the pickup 11, and a signal is reproduced by the signal processing circuit 85.

The irradiation time of the reference light and the signal light applied to the optical information recording medium 1 can be adjusted by controlling the opening / closing time of the shutter in the pickup 11 via the shutter control circuit 87 by the controller 89.

The cure optical system 13 plays a role of generating a light beam used for pre-cure and post-cure of the optical information recording medium 1. Precure is a pre-process for irradiating a predetermined light beam in advance before irradiating the desired position with reference light and signal light when recording information at a desired position in the optical information recording medium 1. Post-cure is a post-process for irradiating a predetermined light beam after recording information at a desired position in the optical information recording medium 1 so that additional recording cannot be performed at the desired position.

The disk rotation angle detection optical system 14 is used to detect the rotation angle of the optical information recording medium 1. When adjusting the optical information recording medium 1 to a predetermined rotation angle, a signal corresponding to the rotation angle is detected by the disk rotation angle detection optical system 14, and a disk rotation motor control circuit is detected by the controller 89 using the detected signal. The rotation angle of the optical information recording medium 1 can be controlled via 88.

A predetermined light source driving current is supplied from the light source driving circuit 82 to the light sources in the pickup 11, the cure optical system 13, and the disk rotation angle detection optical system 14, and each light source emits a light beam with a predetermined light amount. Can do.

Further, the pickup 11 and the disc cure optical system 13 are provided with a mechanism capable of sliding the position in the radial direction of the optical information recording medium 1, and the position is controlled via the access control circuit 81.

By the way, the recording technology using the principle of angle multiplexing of holography tends to have a very small tolerance for the deviation of the reference beam angle.

Therefore, a mechanism for detecting the deviation amount of the reference beam angle is provided in the pickup 11, a servo control signal is generated by the servo signal generation circuit 83, and the deviation amount is corrected via the servo control circuit 84. It is necessary to provide a servo mechanism for this purpose in the optical information recording / reproducing apparatus 10.

Further, the pickup 11, the cure optical system 13, and the disk rotation angle detection optical system 14 may be simplified by combining several optical system configurations or all optical system configurations into one.

FIG. 2 shows a recording principle in an example of a basic optical system configuration of the pickup 11 in the optical information recording / reproducing apparatus 10. The light beam emitted from the light source 301 passes through the collimator lens 302 and enters the shutter 303. When the shutter 303 is open, after the light beam passes through the shutter 303, the optical ratio of the p-polarized light and the s-polarized light becomes a desired ratio by the optical element 304 composed of, for example, a half-wave plate. After the polarization direction is controlled, the light is incident on a PBS (Polarization Beam Splitter) prism 305.

The light beam that has passed through the PBS prism 305 functions as signal light 306, and after the light beam diameter is expanded by the beam expander 308, the light beam passes through the phase mask 309, the relay lens 310, and the PBS prism 311 and passes through the spatial light modulator 312. Is incident on.

The signal light to which information is added by the spatial light modulator 312 reflects the PBS prism 311 and propagates through the relay lens 313 and the spatial filter 314. Thereafter, the signal light is condensed on the optical information recording medium 1 by the objective lens 315.

On the other hand, the light beam reflected from the PBS prism 305 functions as reference light 307 and is set to a predetermined polarization direction according to recording or reproduction by the polarization direction conversion element 316 and then galvano- lated via the mirror 317 and the mirror 318. Incident on the mirror 319. Since the angle of the galvanometer mirror 319 can be adjusted by the actuator 320, the incident angle of the reference light incident on the optical information recording medium 1 after passing through the lens 321 and the lens 322 can be set to a desired angle. In order to set the incident angle of the reference light, an element that converts the wavefront of the reference light may be used instead of the galvanometer mirror.

In this way, the signal light and the reference light are incident on the optical information recording medium 1 so as to overlap each other, whereby an interference fringe pattern is formed in the recording medium, and information is recorded by writing this pattern on the recording medium. To do. In addition, since the incident angle of the reference light incident on the optical information recording medium 1 can be changed by the galvanometer mirror 319, recording by angle multiplexing is possible.

Hereinafter, in holograms recorded in the same area with different reference beam angles, holograms corresponding to each reference beam angle are called pages, and a set of pages angle-multiplexed in the same area is called a book. .

FIG. 3 shows a reproduction principle in an example of a basic optical system configuration of the pickup 11 in the optical information recording / reproducing apparatus 10. When reproducing the recorded information, the reference light is incident on the optical information recording medium 1 as described above, and the light beam transmitted through the optical information recording medium 1 is reflected by the galvanometer mirror 324 whose angle can be adjusted by the actuator 323. By doing so, the reproduction reference light is generated.

The reproduction light reproduced by the reproduction reference light propagates through the objective lens 315, the relay lens 313, and the spatial filter 314. Thereafter, the reproduction light passes through the PBS prism 311 and enters the photodetector 325, and the recorded signal can be reproduced. As the photodetector 325, for example, an image sensor such as a CMOS image sensor or a CCD image sensor can be used. However, any element may be used as long as page data can be reproduced.

The pickup of the present embodiment has been described with the configuration of FIGS. 2 and 3 as an example, but needless to say, it is not limited to this configuration.

FIG. 4 shows an operation flow of recording and reproduction in the optical information recording / reproducing apparatus 10. Here, a flow relating to recording / reproduction using holography in particular will be described.

FIG. 4A shows an operation flow from the insertion of the optical information recording medium 1 into the optical information recording / reproducing apparatus 10 until the preparation for recording or reproduction is completed. FIG. FIG. 4C shows an operation flow until information is recorded on the information recording medium 1, and FIG. 4C shows an operation flow until the information recorded on the optical information recording medium 1 is reproduced from the ready state.

When a medium is inserted as shown in FIG. 4A (601), the optical information recording / reproducing apparatus 10 discriminates whether the inserted medium is a medium for recording or reproducing digital information using holography, for example. (602).

As a result of disc discrimination, when it is determined that the optical information recording medium records or reproduces digital information using holography, the optical information recording / reproducing apparatus 10 reads control data provided on the optical information recording medium (603). ), For example, information relating to the optical information recording medium and information relating to various setting conditions during recording and reproduction, for example.

After reading out the control data, various adjustments according to the control data and learning processing (604) related to the pickup 11 are performed, and the optical information recording / reproducing apparatus 10 is ready for recording or reproduction (605).

As shown in FIG. 4B, the operation flow from the ready state to recording information is as follows. First, data to be recorded is received (611), and information corresponding to the data is received from the spatial light modulator in the pickup 11. Send to.

Thereafter, various recording learning processes such as optimization of the power of the light source 301 and optimization of exposure time by the shutter 303 are performed in advance so that high-quality information can be recorded on the optical information recording medium (612). ).

Thereafter, in the seek operation (613), the access control circuit 81 is controlled to position the pickup 11 and the cure optical system 13 at predetermined positions on the optical information recording medium. When the optical information recording medium 1 has address information, it reproduces the address information, checks whether it is positioned at the target position, and calculates the amount of deviation from the predetermined position if it is not positioned at the target position. And repeat the positioning operation.

Thereafter, a predetermined region is pre-cured using the light beam emitted from the cure optical system 13 (614), and data is recorded using the reference light and signal light emitted from the pickup 11 (615).

After recording the data, post cure is performed using the light beam emitted from the cure optical system 13 (616). Data may be verified as necessary.

As shown in FIG. 4C, the operation flow from the ready state to the reproduction of recorded information is as follows. First, in the seek operation (621), the access control circuit 81 is controlled, and the pickup 11 and the reproduction reference light are reproduced. The position of the optical system 12 is positioned at a predetermined position on the optical information recording medium. When the optical information recording medium 1 has address information, it reproduces the address information, checks whether it is positioned at the target position, and calculates the amount of deviation from the predetermined position if it is not positioned at the target position. And repeat the positioning operation.

Thereafter, reference light is emitted from the pickup 11, information recorded on the optical information recording medium is read (622), and reproduction data is transmitted (613).

FIG. 5 shows an overlap relationship between the signal light 306 and the reference light 307 incident on the optical information recording medium 1 in the optical information recording / reproducing apparatus 10. The shaded vertical lines indicate the signal light 306, and the shaded dotted lines indicate the reference light 307. The optical information recording medium 1 includes a recording layer and a cover layer covering the recording layer. The recording layer includes an upper surface, a lower surface, and a beam waist surface on which the signal light 306 is most focused in the middle between the upper surface and the lower surface.

The signal light 306 becomes convergent light by the objective lens 315 and enters the optical information recording medium 1, and is most narrowed on the beam waist surface as shown in the figure. This state is generally called a beam waist. On the other hand, the reference light 307 enters the optical information recording medium 1 as parallel light. A hologram is recorded by generating a refractive index modulation in the recording layer by the interference pattern generated by the superposition of the two lights. Note that the signal light and the reference light are preferably incident on the optical information recording medium 1 with a predetermined amount of inclination as shown in the drawing in order to increase the number of multiplexed signals and increase the recording capacity.

FIG. 6 shows the positional relationship of the book recorded on the optical information recording medium 1 by the conventional optical information recording / reproducing apparatus, and the state of the signal light traveling to the spatial filter 314 when the recorded selected book 401 is reproduced. . A model in which the adjacent book 402 and the adjacent book 403 are formed on both sides on the basis of the selected book 401 recorded in multiple recording is assumed. As shown in FIG. 6, conventionally,

adjacent books

402 and 403 overlap the selected book 401 on the upper and lower surfaces of the recording layer, but on the beam waist surface where the signal light 306 is most focused, The adjacent books 402 to 403 are recorded so as not to overlap each other.

At the time of reproduction, the reference light 307 is irradiated to the selected book 401 of the optical information recording medium 1, but since the irradiation area is larger by a predetermined amount than the selected book 401 to be reproduced, the adjacent book 402 and the adjacent book 403 also The diffracted signal light travels to the objective lens 315. The signal light diffracted by the selected book 401 is denoted by 411, the signal light diffracted by the adjacent book 402 is denoted by 412, and the signal light diffracted by the adjacent book 403 is denoted by 413.

Here, the beam waist surface of the optical information recording medium 1 and the spatial filter 314 are arranged so as to form an image with each other by the objective lens 315 and the relay lens 313. That is, the signal lights 411 to 413 are beam waists even on the spatial filter 314. At this time, by setting the size of the spatial filter 314 so that only the diffracted signal light 411 passes through the selected book 401, the signal light 412 diffracted from the adjacent book 402 and the signal diffracted from the adjacent book 403 as shown in FIG. The light 413 can be shielded and physically separated, and a reproduced signal with less noise can be obtained.

As described above, in conventional techniques such as Patent Document 1, holograms are formed on the beam waist surface of the optical information recording medium 1 so as not to overlap each other, and the spatial filter 314 is used for reproduction of the signal light of the adjacent book during reproduction. Separation is taking place. However, such a recording method has a problem in increasing the recording capacity because the book interval cannot be recorded smaller than the beam waist.

FIG. 7 shows the positional relationship between the selected book 401, the adjacent book 402, and the adjacent book 403 recorded on the optical information recording medium 1 by the optical information recording / reproducing apparatus of the present embodiment. Compared with the conventional recording method as shown in FIG. 7, the selected book 401 is recorded so as to actively overlap the adjacent book 402 and the adjacent book 403 even on the beam waist surface where the signal light becomes the beam waist. To do. In this way, the recording capacity can be increased by overlapping the books on the beam waist surface.

Next, the amount of overlap on the beam waist surface will be described. FIG. 8 is a schematic diagram showing a hologram formed by the pixels of the spatial light modulator 312 entering the optical information recording medium 1. For simplicity, the PBS prism 311 shown in FIG. 2 is omitted, and the spatial light modulator 312 is arranged in a straight line with respect to the relay lens 313.

In the optical information recording / reproducing apparatus 10 of this embodiment, information is added to each pixel by the spatial light modulator 312. In general, the signal light emitted from each pixel of the spatial light modulator 312 propagates at a divergence angle passing through the spatial filter 314, and after passing through the objective lens 315, becomes substantially parallel light for each pixel and optical information at a predetermined angle. It can be considered to be incident on the recording medium 1. As shown in FIG. 8, the signal light of the pixel having the smallest angle with the reference light 307 on the optical information recording medium 1 is 306a, and the signal of the pixel with the largest angle with the reference light 307 on the optical information recording medium 1 Let 306b be the light. At this time, the size of the beam waist formed on the beam waist surface is different between the signal light 306a and the signal light 306b. The beam waist size formed by the signal light 306a on the beam waist surface of the optical information recording medium 1 is φa, and the beam waist size formed by the signal light 306b on the beam waist surface of the optical information recording medium 1 is φb. At this time, φb having a shallow incident angle is larger than φa.

Hereinafter, the signal light 306a of the pixel having the smallest angle with the reference light 307 is referred to as the innermost signal light, and the signal light 306b of the pixel having the largest angle with the reference light 307 is referred to as the outermost signal light. To.

The signal light of each pixel emitted from the spatial light modulator 312 travels on the spatial filter 314 with the same beam waist size. However, since the optical information recording medium 1 and the optical axis are inclined by a predetermined amount, a difference occurs in the beam waist size on the beam waist surface of the optical information recording medium 1 depending on each pixel.

Also, the beam diameter of the signal light on the beam waist surface is determined by the beam waist size of the outermost signal light. Further, the beam waist size of the signal light incident at other angles is irradiated onto the beam waist surface with a smaller size.

FIG. 9 is a diagram showing the relationship between the incident angles of the signal light 306 and the reference light 307 in the optical information recording medium 1. FIG. 9A shows simplified signal light 306 and reference light 307 incident on the optical information recording medium 1. From the figure, it can be seen that, among the signal light 306, the innermost signal light 306a and the outermost signal light 306b are greatly different in angle with the reference light 307. This is because the signal light 306 is collected by the objective lens 315, and therefore the incident angle to the optical information recording medium 1 varies greatly depending on the position that has passed through the objective lens 315. FIG. 9B shows an enlarged view of the incident light beam overlap portion 450 in the optical information recording medium 1 of FIG. The chief ray angle of the reference light 307 is θr with respect to the normal line of the optical information recording medium 1 indicated by the broken line. The angle of the innermost signal light 306a of the signal light 306 with respect to the normal of the optical information recording medium 1 is θa, and the angle of the outermost signal light 306b with respect to the normal of the optical information recording medium 1 is θb. The angle of the signal light changes from θa to θb. As described above, since the incident angle of the signal light 306 with respect to the medium varies greatly depending on the position that has passed through the objective lens 315, the angle formed by the signal light 306 and the reference light 307 also varies greatly depending on the position.

FIG. 10 is a diagram showing the relationship between the reference light angle deviation Δθr during recording and reproduction and the diffraction efficiency η of reproduced light in the hologram recorded on the optical information recording medium 1. The diffraction efficiency when the incident angle of the signal light shown in FIG. 9 is θa is 500a, and the diffraction efficiency when the incident angle of the signal light is θb is 500b.
When the angle formed by the signal light and the reference light is θrs and the incident angle of the signal light is θs, the diffraction efficiency η is

It is represented by Here, λ is the wavelength of the light source 301, n is the refractive index of the optical information recording medium 1, and L is the thickness of the recording layer of the optical information recording medium 1.

From Equation 1, the diffraction efficiency η varies with the sinc function depending on the reference beam angle deviation Δθr during recording and reproduction. Further, the rate of change of the diffraction efficiency η with respect to the reference light angle deviation Δθr during reproduction varies greatly depending on the angle θrs formed by the signal light and the reference light and the incident angle θs of the signal light. That is, the angle selectivity is greatly different. As shown in FIG. 10, the diffraction efficiency 500a when the incident angle of the signal light is θa is such that the angle θrs formed by the signal light and the reference light and the incident angle θs of the signal light are small. It can be said that the angle selectivity of the hologram composed of the signal light 306a is wide. On the other hand, the diffraction efficiency 500b when the incident angle of the signal light is θb has a large change in the diffraction efficiency with respect to the reference light angle deviation Δθr because the angle θrs formed by the signal light and the reference light and the incident angle θs of the signal light are large. That is, it can be said that the angle selectivity of the hologram composed of the signal light 306b is narrow. As an example, as shown in FIG. 10, when the reference beam angle deviation during reproduction is Δθ ′, the diffraction efficiency 500a has a wide angle selectivity, so that a predetermined amount of diffraction efficiency is generated, but the diffraction efficiency 500b has an angle selectivity. Is narrow, the diffraction efficiency is Null. In this way, when the signal light is separated for each pixel, the angle formed with the reference light differs depending on the signal light position, so that the diffraction efficiency η detected when the reference light angle shift during reproduction also occurs. to differ greatly. That is, by using the reference light angle shift during reproduction, it is possible to make only the diffraction efficiency of signal light having a large angle θrs a sufficiently small value.

Generally, it is necessary to avoid overlap of adjacent books on the beam waist surface. From this point of view, it is a principle that both the innermost signal light 306a and the outermost signal light 306b shown in FIG. However, the feature of this embodiment is that, as shown in FIG. 10, the angle of the hologram composed of the outermost signal light 306b is compared with the angle selectivity of the hologram composed of the innermost signal light 306a. Since the selectivity is narrow, for example, by recording the hologram of the adjacent book with a shift of Δθ ′ shown in FIG. 10 with respect to the selected book, the crosstalk of the adjacent book of the hologram by the innermost angle signal light 306b exceeds the predetermined amount. Even if it is wrapped, the influence can be sufficiently reduced from the viewpoint of angle selectivity.

FIG. 11 shows the positions of the selected book 401 (indicated by the shaded vertical lines), the adjacent book 402 (indicated by the dashed frame), and the adjacent book 403 (indicated by the dashed line frame) recorded on the optical information recording medium 1. It is the figure which added the signal light component of the innermost angle, and showed the relationship. The innermost signal light of the selected book 401 is 401a, the innermost signal light of the adjacent book 402 is 402a, and the innermost signal light of the selected book 403 is 403a. In addition, a beam waist size formed on the beam waist surface by 401a, 402a, and 403a is φa. As shown in FIG. 8, the signal light beam waist size at the beam waist surface is smaller at the innermost angle than the outermost angle, and as shown in FIG. 10, a hologram composed of the innermost signal light 306a. Compared with the angle selectivity of each of the above, by utilizing the fact that the angle selectivity of the hologram composed of the signal light 306b at the outermost angle is narrow, the books are shifted from each other by at least φa on the beam waist surface, so that each book is optical information. Recording is performed on the recording medium 1.

FIG. 12 shows a hologram recording method in this embodiment. FIG. 12A shows how the selected book is recorded. The selected book 401 is recorded at a predetermined position with the incident angle of the reference light as θr. FIG. 12B shows a recording state of the adjacent book 402. As shown in the figure, the adjacent book 402 is recorded with a shift of φc with respect to the selected book 401 on the beam waist surface. At this time, the shift amount φc is set to be equal to or larger than the beam waist size φa formed by the innermost signal light 306a and smaller than the beam waist size φb formed by the outermost signal light 306b. Further, the incident angle of the reference light is θr + Δθc, which is shifted by Δθc with respect to the reference light angle when the selected book 401 is recorded. For example, the value of Δθc may be selected so that the diffraction efficiency of the outermost signal light is sufficiently small. Hereinafter, other adjacent books are also recorded while being shifted by a predetermined angle relatively.

Needless to say, Δθc is not limited to the above value. Any value may be used as long as the diffraction efficiency η is sufficiently small. Further, Δθc may be either positive or negative rotation direction.

FIG. 13 shows the progress of the signal light to the spatial filter 314 when the selected book 401 is reproduced in the book recorded as shown in FIG. FIG. 13A shows the relationship between the signal light of the selected book 401 and the adjacent book 402. The reference light 307 is emitted at the same θr as that for recording in order to reproduce the selected book 401. The signal light 411 diffracted from the selected book 401 propagates as shown in the figure and passes through the spatial filter 314. At this time, the adjacent book 402 is also irradiated with a part of the reference light 307 and diffracted, so that the signal light 412 travels. However, since the innermost signal light component is physically separated, it cannot be passed through the spatial filter 314 and is shielded. On the other hand, since the signal light component at the outermost angle partially overlaps, a part of the light passes through the spatial filter 314 like 422. However, in the adjacent book, the reference light incident angle during reproduction is shifted by Δθc, so that the diffraction efficiency η can be reduced, and as a result, the crosstalk can be reduced. The amount of diffracted light can be set to a sufficiently small value by adjusting Δθc.

FIG. 13B shows the relationship between the signal light of the selected book 401 and the adjacent book 403. Here too, the same phenomenon as in FIG. Since the adjacent book 403 is diffracted by being partially irradiated with the reference light 307, the signal light 413 travels. However, since the innermost signal light component is physically separated, it cannot be passed through the spatial filter 314 and is shielded. On the other hand, since the signal light component at the outermost angle partially overlaps, a part of the light passes through the spatial filter 314 like 423. However, in the adjacent book, the reference light incident angle during reproduction is shifted by a predetermined amount, so that the diffraction efficiency η can be reduced, and as a result, the crosstalk can be reduced. The amount of diffracted light can be made sufficiently small by adjusting the amount of reference light incident angle deviation.

As described above, in this embodiment, since the optical axis of the signal light is inclined by a predetermined amount with respect to the optical information recording medium 1, the beam formed by each pixel of the spatial light modulator 312 on the optical information recording medium 1. The angle selection is made by skillfully utilizing the fact that the angle selectivity of the hologram is different for each pixel because the waist size is different and the angle between the signal light and the reference light of each pixel of the spatial light modulator 312 is different. For holograms with a wide range of characteristics, avoid overlapping, and for holograms with a narrow angle selectivity, the adjacent book and the reference light incident angle are shifted by a predetermined amount, so that even if they overlap, the crosstalk between adjacent books is sufficiently small can do. This makes it possible to increase the recording capacity with a simple configuration.

In the prior art such as Patent Document 1, there is a description that the incident angle of the reference light is changed depending on the recording book, but there is no description that the book is overlapped on the beam waist surface of the optical information recording medium 1, and the adjacent book diffraction during reproduction It is described that light is separated by a spatial filter. Moreover, it is not considered what range the overlap amount is. In the present embodiment, attention is paid to the fact that the angle selectivity of the hologram changes depending on the angle between the beam waist size formed by each pixel of the spatial light modulator 312 on the optical information recording medium 1 and the reference light. Even when part of the signal light of the adjacent book passes, a configuration that can sufficiently reduce the influence of crosstalk is realized.

Note that the interval between the selected book and the adjacent book is such that the outermost signal light is less than the beam waist size φb formed by the beam waist surface of the optical information recording medium 1, and the outermost signal light is the beam waist surface of the optical information recording medium 1. As long as the beam waist size φa is not smaller than the beam waist size, any interval may be used.

As described above, unlike the conventional case, the adjacent book is recorded with a predetermined amount overlapping the selected book. The interval between adjacent books is set to be equal to or smaller than the beam waist size φb of the incident light at the outermost angle and equal to or larger than the beam waist size φa of the incident light at the innermost angle. The reference beam angle at the time of recording is shifted by a predetermined amount when recording the adjacent book with respect to the selected book. The amount of angular deviation at this time is adjusted so that the diffracted light quantity of the adjacent book that passes through the spatial filter during reproduction does not affect the signal performance. With such a recording method, the amount of diffracted light can be suppressed to 0 or the minimum value even when the outermost signal light passes through a partial spatial filter during reproduction. Therefore, it is possible to realize an optical information recording / reproducing method and an optical information recording / reproducing apparatus using the method, which can increase the recording capacity with a simple configuration.

In Example 2, a method for recording a plurality of pages by angle multiplexing will be described. FIG. 14 is a diagram showing hologram recording when angle multiplex recording is performed by changing the incident angle of the reference beam. As an example, assume that n pages are recorded in one book. FIG. 14A shows how a plurality of pages are recorded in the selected book 401. In the selected book 401, the angle of the reference beam is changed by a predetermined amount such as θr = θ1, θ2, θ3,. Note that n is an integer of 2 or more.

FIG. 14B shows a state where a plurality of pages are recorded in the adjacent book 402. The adjacent book 402 is recorded at a position away from the selected book 401 by a predetermined amount on the beam waist surface. At this time, the selected book 401 and the adjacent book 402 are recorded with Δd overlap on the beam waist surface. The overlap amount Δd ranges from 0 to φb−φa, where φa is the beam waist size of the incident light at the innermost angle and φb is the beam waist size of the incident light at the outermost angle. That is, the adjacent book 402 is shifted from the selected book 401 in the range of φ1 to φ2 and recorded.

Note that the incident angle of the reference light during recording is shifted by Δθc with respect to the selected book 401, and n pages are recorded as θr = θ1 + Δθc, θ2 + Δθc, θ3 + Δθc,... Θn + Δθc. Δθc may be any value as long as the diffraction efficiency η of the adjacent book becomes small when the selected book 401 is reproduced. Further, Δθc may be fixed at all angles, or may be changed according to the angle instead of a fixed value. For example, it may be controlled to half the angular interval of the page. In this case, a value between θ1 and θ2 is Δθc = (θ2−θ1) / 2. Further, a value between Δ2 and θ3 is set to Δθc = (θ3−θ2) / 2. When the inter-page angle is not constant, the value of Δθc also varies between pages. Hereinafter, other adjacent books are also recorded while being shifted by a predetermined angle relatively.

By the recording method as described above, similarly to the first embodiment, even when a plurality of holograms are recorded with a predetermined amount of overlap on the beam waist surface, the crosstalk of adjacent books can be sufficiently reduced.

Example 3 describes a method of recording by shifting a predetermined amount by page in one book. A value called an M number is used as an index of how many holograms can be multiplex-recorded at a predetermined position of the optical information recording medium 1. The M number is an eigenvalue determined by the material and thickness of the optical information recording medium 1. On the other hand, the diffraction efficiency η of the hologram is proportional to the M number and inversely proportional to the number of multiplexing. From the viewpoint of M number consumption, it is important to reduce the number of holograms recorded at a predetermined position as much as possible. Therefore, as shown in FIG. 15, a recording method can be used in which one book is recorded while being shifted by a predetermined amount depending on the page so as to suppress consumption of the M number. Hereinafter, a group of pages is called a stack, and the above recording method is called a short stack. In the present embodiment, the n-page recording is adjacent to the selected book 401 on the beam waist surface of the optical information recording medium 1 when divided into two stacks of page 1 to page i and page i + 1 to page n. The positional relationship of the book 402 is shown. Note that n is an integer of 2 or more, and i is an integer of 0 or more.

FIG. 15A is a diagram showing a conventional short stack. When the selected book 401 is recorded, pages 1 to i are recorded at the same position by angle multiplexing, and then pages i + 1 to n are recorded at a position shifted by a predetermined amount Δt by angle multiplexing. Subsequently, pages 1 to i of the adjacent book 402 are recorded so as not to overlap each other on the beam waist surface at the position where pages 1 to i of the selected book 401 are recorded. Next, pages i + 1 to n of the adjacent book 402 are recorded so as not to overlap each other on the beam waist surface with respect to the positions where pages i + 1 to n of the selected book 401 are recorded. By recording in this way, it is possible to perform recording while suppressing consumption of the M number.

FIG. 15B is a diagram showing the short stack of this example. When the selected book 401 is recorded, pages 1 to i are recorded at the same position by angle multiplexing, and then pages i + 1 to n are recorded at a position shifted by a predetermined amount Δt by angle multiplexing. Subsequently, pages 1 to i of the adjacent book 402 are recorded so as to overlap by Δd on the beam waist surface with respect to the position where pages 1 to i of the selected book 401 are recorded. The overlap amount Δd at this time is in the range of 0 to φb−φa when the beam waist size of the incident light at the innermost angle is φa and the beam waist size of the incident light at the outermost angle is φb. That is, the adjacent book 402 is recorded with a shift from φ1 to φ2 with respect to the selected book 401. The incident angle of the reference light at the time of recording is shifted from the selected book 401 by Δθ. Δθ may be any value as long as the diffraction efficiency η of the adjacent book becomes small when the selected book 401 is reproduced.

Next, when recording page i + 1 to page n of the adjacent book 402, recording is performed by overlapping Δd on the beam waist surface with respect to the position where page i + 1 to page n of the selected book 401 is recorded. The overlap amount Δd at this time is in the range of 0 to φb−φa when the beam waist size of the incident light at the innermost angle is φa and the beam waist size of the incident light at the outermost angle is φb. That is, the adjacent book 402 is recorded with a shift from φ1 to φ2 with respect to the selected book 401. The incident angle of the reference light at the time of recording is shifted from the selected book 401 by Δθ. Δθ may be any value as long as the diffraction efficiency η of the adjacent book becomes small when the selected book 401 is reproduced.

By recording in this way, it is possible to suppress consumption of the M number and increase the recording capacity.

In this embodiment, the recording method for recording one book in two stacks is described, but it goes without saying that the number is not limited to two. Three or more stacks may be used. The amount of Δt may be any number as long as it is equal to or smaller than the beam waist size formed by the beam waist surface.

In the embodiment, the value of Δd is a fixed value regardless of the stack position. However, the signal performance may be changed to the most stable value depending on the stack position.

Example 4 describes a method for recording by changing the overlap amount of the beam waist according to the type of optical information recording medium and / or the area of the optical information recording medium.

As described in the third embodiment, the number of hologram multiplex recordings on the optical information recording medium is determined by the M number. When the M number varies for each optical information recording medium, or when an optical information recording medium having a plurality of M number standards is generated, and when the M number is different within the area of the optical information recording medium, the M number value Accordingly, it is necessary to perform recording and reproduction by changing the number of multiplexed recordings and the overlap amount of the beam waist.

FIG. 16A shows an operation flow from when the optical information recording medium 1 is inserted into the optical information recording / reproducing apparatus 10 until preparation for recording or reproduction corresponding to the type of the medium is completed.

When a medium is inserted as shown in FIG. 16 (a) (631), the optical information recording / reproducing apparatus 10 discriminates whether or not the inserted medium is a holographic recording / reproducing medium (632).

Subsequently, information on the M number of the inserted medium is acquired from a predetermined position of the medium (633). When the M number is found, the number of multiplexing according to the M number and the overlap amount of the beam waist are learned (634). For example, when the M number is small, it is necessary to set the number of multiplexes to be small. However, if the number of multiplexes is small, the angle of the page interval can be set large, so the overlap amount becomes large. On the contrary, when the M number is large, a large number of multiplexing can be set. However, when the number of multiplexing is large, the angle of page interval becomes small, so the overlap amount becomes small. After learning the appropriate multiplexing number and overlap amount for the medium, the optical information recording / reproducing apparatus 10 completes preparation for recording or reproduction (635). Then, recording is performed with an overlap amount corresponding to the type of the optical information recording medium 1.

FIG. 16B shows an operation flow until the preparation for recording or reproduction is completed when the optical information recording medium 1 is inserted into the optical information recording / reproducing apparatus 10 and the M number is different within the area of the medium. Indicates.

Since steps (641) and (642) in FIG. 16 (b) are the same as FIG. 16 (a), description thereof will be omitted. After the medium determination, information of M number different in the area of the inserted medium is acquired from a predetermined position of the medium (633). Next, an appropriate multiplexing number and an overlap amount of the beam waist portion are learned for each region corresponding to the M number (644). Thereby, even when a plurality of M numbers are generated in the area, the recording / reproducing performance can be fully utilized. After learning the appropriate multiplexing number and overlap amount, the optical information recording / reproducing apparatus 10 is ready for recording or reproduction (645). Then, recording is performed with an overlap amount corresponding to the area of the optical information recording medium 1.

As described above, the M number of the medium is recorded on the medium in advance, and an operation flow for learning the information in advance is performed. Recording and reproduction can be performed with an overlap amount.

In this embodiment, not only the overlap amount but also the reference light angle deviation amount Δθc may be changed according to the type and / or area of the optical information recording medium 1. Thereby, the capacity can be increased.

The overlap amount in steps (634) and (644) may not be obtained by learning, but may be a predetermined value (for example, a value determined by a standard).

In addition, this invention is not limited to the above-mentioned Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

DESCRIPTION OF SYMBOLS 1 ... Optical information recording medium, 10 ... Optical information recording / reproducing apparatus, 11 ... Pickup, 12 ... Reference optical system for reproduction | regeneration, 13 ... Disc cure optical system, 14 ... Disc Rotation angle detection optical system, 81 ... access control circuit, 82 ... light source drive circuit, 83 ... servo signal generation circuit, 84 ... servo control circuit, 85 ... signal processing circuit, 86 ..Signal generation circuit, 87... Shutter control circuit, 88... Disk rotation motor control circuit, 89... Controller, 90... Input / output control circuit, 91. ... Collimating lens, 303 ... Shutter, 305 ... PBS prism, 306 ... Signal light, 307 ... Reference light, 308 ... Beam expander, 309 ... Phase mask, 31 ... Relay lens, 311 ... PBS prism, 312 ... Spatial light modulator, 313 ... Relay lens, 314 ... Spatial filter, 315 ... Objective lens, 316 ... Polarization direction conversion Element, 320 ... Actuator, 321 ... Lens, 322 ... Lens, 323 ... Actuator, 324 ... Mirror, 325 ... Photodetector

Claims

In the optical information recording / reproducing method,
A generation step of generating signal light and reference light;
A modulation step of modulating the signal light generated in the generation step;
Injecting the signal light modulated in the modulation step at a predetermined angle with respect to the normal of the optical information recording medium, and injecting the reference light generated in the generation step into the optical information recording medium;
A recording step of recording information by causing the signal light and the reference light incident on the optical information recording medium in the incident step to interfere with each other on the optical information recording medium;
The recording step includes
A first recording step of forming a first hologram at a predetermined position of the optical information recording medium by interference between the first signal light and the first reference light;
A second recording step of forming a second hologram at a position of the optical information recording medium adjacent to the first hologram by interference between the second signal light and the second reference light,
In the first recording step or the second recording step, a first beam waist of the first signal light in the first hologram and a second of the second signal light in the second hologram. Of the first reference beam when the first hologram is formed, and the second waist is overlapped by a predetermined amount on the beam waist surface of the optical information recording medium. An optical information recording / reproducing method, wherein the incident angles of the second reference light when forming a hologram are shifted from each other by a predetermined amount.
The optical information recording / reproducing method according to claim 1,
In the first recording step or the second recording step,
Of the pixels constituting the spatial light modulation element used in the modulation step, the beam waist size of the hologram formed by the signal light of the pixel having the smallest angle with the reference light is φ1, and the reference light is When the beam waist size of the hologram formed by the signal light of the pixel having the largest angle is φ2, the second hologram is at least φ1 and not more than φ2 with respect to the first hologram on the beam waist surface. An optical information recording / reproducing method, wherein recording is performed while being shifted.
The optical information recording / reproducing method according to claim 2,
In the first recording step or the second recording step, the amount of incident angle deviation of the second reference light with respect to the first reference light is set to be diffraction of the hologram by the signal light that forms at least the beam waist size φ2. An optical information recording / reproducing method characterized in that the amount of light is initially controlled to an amount that is substantially zero.
The optical information recording / reproducing method according to claim 2,
In the first recording step or the second recording step, a plurality of incident angles of the first reference light are θr = θ1, θ2,..., Θn (n is an integer of 2 or more), When the plurality of incident angles of the reference light 2 are θr = θ1 + Δθ, θ2 + Δθ,. An optical information recording / reproducing method characterized in that the amount of light is controlled to be substantially zero or the minimum amount.
In the optical information recording and reproducing method according to claim 4,
In the first recording step or the second recording step, the reference light incident angle deviation amount Δθ is controlled to be different depending on the incident angle of the reference light.
In the optical information recording and reproducing method according to claim 4,
In the first recording step or the second recording step, holograms from the first to i-th (i is an integer of 0 or more) and i + 1-th to n-th of reference light incident angles forming the hologram Holograms up to (n is an integer of 2 or more) are formed at positions shifted from each other by a predetermined amount.
The optical information recording / reproducing method according to claim 1,
In the first recording step or the second recording step, the first hologram and the second hologram are overlapped on the beam waist surface according to the type and / or region of the optical information recording medium. An optical information recording / reproducing method characterized by changing the amount.
In an optical information recording / reproducing apparatus,
An optical system for generating signal light and reference light;
A spatial light modulator that modulates the signal light generated by the optical system;
An objective lens that focuses the signal light modulated by the spatial light modulation unit at a predetermined angle with respect to the normal of the optical information recording medium; and
An optical element that changes an incident angle of the reference light generated by the optical system to the optical information recording medium;
A moving unit for controlling a relative position between the optical information recording medium and the objective lens;
A control unit for controlling the optical element and the moving unit;
The controller is
Forming a first hologram at a predetermined position of the optical information recording medium by interference between the first signal light and the first reference light;
Forming a second hologram at a position of the optical information recording medium next to the first hologram by interference between the second signal light and the second reference light;
A first beam waist of the first signal light in the first hologram and a second beam waist of the second signal light in the second hologram are on the beam waist surface of the optical information recording medium. And an angle of incidence of the first reference light when forming the first hologram and an angle of incidence of the second reference light when forming the second hologram The optical element and the moving unit are controlled so as to record information on the optical information recording medium with a predetermined amount shifted from each other.
The optical information recording / reproducing apparatus according to claim 8.
The control unit defines the beam waist size of the hologram formed by the signal light of the pixel having the smallest angle formed with the reference light among the pixels constituting the spatial light modulation unit as φ1 and the reference light. When the beam waist size of the hologram formed by the signal light of the pixel having the largest angle is φ2, the second hologram is at least φ1 and not more than φ2 with respect to the first hologram on the beam waist surface. An optical information recording / reproducing apparatus, wherein the moving unit is controlled so as to be recorded with a shift.
The optical information recording / reproducing apparatus according to claim 9.
The control is performed so that an incident angle shift amount of the second reference light with respect to the first reference light is an amount at which the diffracted light quantity of the hologram by the signal light forming the beam waist size φ2 is substantially zero first. The optical information recording / reproducing apparatus is characterized in that the unit controls the optical element.
The optical information recording / reproducing apparatus according to claim 9.
A plurality of incident angles of the first reference light are θr = θ1, θ2,..., Θn (n is an integer of 2 or more), and a plurality of incident angles of the second reference light are θr = θ1 + Δθ, θ2 + Δθ. ,..., .Theta.n + .DELTA..theta., The reference light incident angle deviation amount .DELTA..theta. Is such that at least the diffraction light quantity of the hologram by the signal light forming the beam waist size .phi. The control unit controls the moving unit and the optical element, and is an optical information recording / reproducing apparatus.
The optical information recording / reproducing apparatus according to claim 11,
The optical information recording / reproducing apparatus is characterized in that the reference light incident angle deviation amount Δθ is different from each other depending on the incident angle of the reference light.
The optical information recording / reproducing apparatus according to claim 11,
Among the reference light incident angles forming the hologram, the first to i-th holograms (i is an integer of 0 or more) and the i + 1-th to n-th holograms (n is an integer of 2 or more) are mutually located. The optical information recording / reproducing apparatus, wherein the control unit controls the moving unit and the optical element so as to be formed at a position that is deviated quantitatively.
The optical information recording / reproducing apparatus according to claim 8.
The control unit is configured to change the amount of overlap between the first hologram and the second hologram on the beam waist surface according to the type and / or region of the optical information recording medium. An optical information recording / reproducing apparatus for controlling an optical element.