WO2017060984A1

WO2017060984A1 - Hologram reproduction device and hologram reproduction method

Info

Publication number: WO2017060984A1
Application number: PCT/JP2015/078436
Authority: WO
Inventors: 弘充森; 誠保坂; 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: 2015-10-07
Filing date: 2015-10-07
Publication date: 2017-04-13

Abstract

Provided are a hologram reproduction device and reproduction system capable of improving the reliability and improving the speed of hologram reproduction. Provided is a hologram reproduction device that changes irradiates, with a reference light, a recording medium in which the incident angle of the reference light is changed to a first direction and a hologram has been angle-multiplexing recorded, and reproduces the recorded hologram by receiving, with an imaging element, generated diffracted light as reproduction light, the hologram reproduction device being characterized by being provided with: a reference light angle adjustment unit that adjusts a medium incident angle at which the reference light enters the recording medium; an aperture filter having an aperture which the reproduction light from the recording medium enters and through which the reproduction light is transmitted; a light detection unit that detects light emitted from the aperture filter and outputs a signal on the basis of the detected light; and a positional deviation detection unit that, on the basis of the signal outputted by the light detection unit, detects an amount of relative positional deviation of the recording position of a hologram to be reproduced and the irradiation position on the recording medium of the reference light for reproducing the hologram to be reproduced. The reference light angle adjustment unit adjusts a medium incident angle of the reference light in a second direction which is perpendicular to the first direction on the basis of the positional deviation amount detected by the positional deviation detection unit.

Description

Hologram reproducing apparatus and hologram reproducing method

The present invention relates to an apparatus and method for reproducing information from a recording medium using holography.

An example of holographic memory technology is, for example, Japanese Patent Application Laid-Open No. 2013-097837 (Patent Document 1). In this publication, as a problem, “a contraction or expansion of a hologram recording medium on which page data information is recorded in a multiplexed manner, or a hologram misalignment that occurs when a replaceable recording medium is installed, etc. A hologram reproducing apparatus capable of reducing the time required and a method for searching for an optimum value of the reference light incident angle at the time of reproduction are provided. As a solving means, “a hologram recording medium 11 on which page data information is angle-multiplexed recorded” is described. A hologram reproducing device that has an information reproducing unit that reproduces page data information by irradiating a reference light during reproduction, and adjusts the information reproducing unit so that a light wave carrying the page data information is obtained. When reproducing the page data information, the signal light incident angle Θs, the recording reference light incident angle Θr, the light wavelength λ, the refractive index n of the recording medium, and the recording medium Based the rate α to the arithmetic expression for an element provided with a computing means 40 for obtaining the desired reproduction reference beam incident angle .phi.read. Has been described as ".

Another patent document is, for example, Japanese Patent Application Laid-Open No. 2006-268933 (Patent Document 2). This publication describes, as a problem, “to provide a holographic device and a method for reproducing a holographic medium that can be reproduced under conditions of a desired angle and wavelength with respect to a wavelength shift due to an angle shift or a change in ambient temperature”. As a solution, “The holography device of the present invention is designed to multiplex-record each predetermined storage area by changing the angle of the reference light applied to the holographic medium. Reference light irradiation means for irradiating, reproduction light emitted from each information data page by the reference light is incident on the detection surface, and data detection means for reproducing information data from the reproduction light, and emitted from the holographic medium by the reference light The reproduced light is used to detect the light intensity of the reproduced light in each of a plurality of predetermined areas on the detection surface and enter the reference light holographic medium. And a reference light control means for controlling the incident angle and wavelength of the reference light according to the detection result of the angle and wavelength deviation of the reproduction light. Has been.

JP 2013-097837 A JP 2006-268933 A

In a hologram recorded in an angle multiplexed manner in the same area of the medium, a hologram corresponding to each reference beam angle is called a page, and a set of pages angle multiplexed in the same area is called a book.

Suppose that a holographic memory device that records and reproduces a disk-shaped medium reproduces a book recorded along the circumferential direction of the medium. In this case, every time the book to be reproduced changes, the spindle motor feed rotation angle is controlled, and the book positioning operation with respect to the reference light is repeated. At this time, since the influence of variations in the characteristics of the rotational drive system and the sensor system is inevitable, even if the same feed rotation angle command value is given, the same feed rotation angle cannot be reproduced.

As a result, every time the book positioning operation is repeated, a tilt error and a position error occur as a relative error of the book with respect to the reference light in the circumferential direction of the medium. This error reduces the amount of light reproduced during book reproduction. Therefore, the reproduction quality also deteriorates. Therefore, in the holographic memory device, it is necessary to tighten the allowable value of the relative error in order to perform high-quality and stable reproduction. Therefore, there arises a problem that it is difficult to increase the reliability of the hologram medium and the reproduction speed by increasing the allowable value of the relative error.

On the other hand,

Patent Documents

1 and 2 do not disclose from the viewpoint of expanding the allowable value of the relative error, and cannot cope with the problem of improving the reliability and speed of the hologram reproduction.

Therefore, an object of the present invention is to provide a hologram reproducing apparatus and a reproducing method capable of improving the reliability and speed of hologram reproduction.

The above problem is solved by the following configuration, for example.

The recording was performed by irradiating the recording medium on which the hologram was angle-multiplexed recorded by changing the incident angle of the reference light in the first direction, and receiving the generated diffracted light as reproduction light by the imaging device. In a hologram reproducing apparatus for reproducing a hologram, a reference light angle adjusting unit that adjusts a medium incident angle at which the reference light is incident on the recording medium, and the reproducing light from the recording medium is incident and the reproducing light is transmitted An aperture filter having an aperture, a light detection unit that detects light emitted from the aperture filter and outputs a signal based on the detected light, and a hologram to be reproduced based on the signal output from the light detection unit A positional deviation detection unit for detecting a relative positional deviation amount between the recording position of the reproduction target hologram and the irradiation position on the recording medium of the reference light for reproducing the reproduction target hologram, and The illumination angle adjustment unit adjusts a medium incident angle in a second direction perpendicular to the first direction of the reference light based on a positional shift amount detected by the positional shift detection unit. apparatus.

According to the present invention, it is possible to provide a hologram reproducing apparatus that improves the reproduction reliability and speed.

The figure which shows a hologram reproducing apparatus in an Example. The figure explaining an aperture filter and a photodetector in an Example. The figure explaining the light quantity detection on the photodetector light-receiving surface in an Example. The figure explaining the reproduction | regeneration object book in which the position shift occurred in the Example. In an Example, derivation explanatory drawing of the medium radial direction correction angle of reference light. The graph explaining the correction effect in an Example. The graph explaining the correction effect in an Example. The graph explaining the correction effect in an Example. 6 is a flowchart for explaining a book reproduction operation in the first embodiment of the present invention. The figure which showed the eccentric state of the track | truck at the time of recording in an Example. The figure which shows a hologram reproducing apparatus in an Example. The figure which shows the light-receiving surface of a photodetector in an Example. FIG. 6 is a derivation explanatory diagram of a reference light correction angle in a state where there is recording track eccentricity in the embodiment. In the embodiment, a flow for explaining the book reproduction operation The figure explaining an optical pick-up in an Example.

Hereinafter, examples will be described with reference to the drawings.

Embodiment FIG. 1 shows a configuration example of a hologram reproducing apparatus of the present embodiment.

The hologram reproducing device 10 is connected to an external control device 91 via an input / output control circuit 90. When reproducing, the image information output from the image sensor 120 of the optical pickup 11 is converted into an electric signal by the signal processing circuit 85, and this electric signal is transmitted to the external control device 91 by the input / output control circuit 90.

In recording and reproduction using holographic angle multiplexing, the tolerance for the deviation of the reference beam angle tends to be small. Therefore, a mechanism for detecting the deviation amount of the reference beam angle is provided in the optical pickup 11 to provide a servo signal generation circuit. A servo control signal is generated at 83 and the deviation amount is corrected via the servo control circuit 84.

Hereinafter, the optical pickup 11 and the optical system 101 of the optical pickup 11 which are features of the present embodiment will be described. Reference numeral 107 denotes a disc-shaped medium, 108 denotes a book which is a set of page data already recorded on the

medium

107, 123 denotes a circumferential direction of the

medium

107, and 124 denotes a radial direction of the medium 107. The book is reproduced along the circumferential direction 123. In the figure, one book 108 is shown as a book, but actually, a plurality of books 108 are arranged at predetermined intervals along the circumferential direction 123.

The medium 107 is mounted on a spindle motor (not shown) and rotates in the circumferential direction 123. The spindle motor is driven in the radial direction 124 by a feed driving mechanism (not shown). This feed drive mechanism is provided with a position sensor 122 and detects the position in the radial direction 124 when the book 108 is played back.

The reference light 102 reflects the angle variable mirror 103 held by the actuator 104, passes through the scanner lens 106, and is irradiated onto the book 108 at a predetermined incident angle. For example, an electromagnetic actuator that can tilt the variable angle mirror 103 in the circumferential direction 123 and the radial direction 124 of the medium 107 can be used as the actuator 104, and the incident angle of the reference light 102 with respect to the medium 107 can be changed.

The angle sensor 105 that detects the tilt angle of the actuator 104 and the variable angle mirror 103 is connected to the angle control circuit 125, and controls the variable angle mirror 103 to a desired tilt angle by feedback control.

The reference light 102 that has passed through the book 108 is reflected by the mirror 109 to become the reproduction reference light 126, enters the medium 107 again, and is diffracted to generate the reproduction light 110. The reproduction light 110 passes through the objective lens 111, the relay lens 112, the aperture filter 113, the PBS 116, and the PBS 119 and is irradiated to the image sensor 120 such as a CCD sensor or a CMOS sensor, thereby reproducing the book. Note that the position of the aperture filter 113 is adjusted to a reference position in the optical system assembly adjustment. Details of the aperture filter 113 will be separately described later with reference to FIGS.

By the way, in the book reproduction, the spindle motor feed rotation angle is controlled and the book positioning operation is performed with respect to the reference light. However, the influence of variations in the characteristics of the drive system and the sensor system is inevitable, so the same feed rotation angle is set every time. I can't control it. Therefore, the positional deviation of the book 108 always occurs with respect to the reference beam 102, and this positional deviation amount changes every time the book positioning operation is performed. Therefore, a means for detecting the amount of displacement is required. However, for example, if the medium 107 is moved by moving it in the circumferential direction 123, the detection speed cannot be increased because the medium 107 is heavy. Although it is conceivable to use an image sensor as the positional deviation amount detection means, it takes time and is not suitable for speeding up since it is calculated from image data with a large amount of information.

Therefore, in this embodiment, the positional deviation amount is detected at high speed by providing the optical means described below. The contents will be described below.

When the position deviation of the book 108 occurs with respect to the reference light 102, a relative position error of the reproduction light 110 occurs with respect to the aperture filter 113. At this time, a part of the reproduction light 110 is incident on the divided wavelength plate region shown in FIG. 2, is emitted with the polarization direction rotated by approximately 90 degrees, is reflected by the reflection surface of the PBS 116, and is separated as the position detection light 128 of the book 108. Is done. Thereafter, the light is condensed by the detection lens 117 and irradiated to the photodetector 118.

The photodetector 118 is connected to a signal generation circuit 121, which generates a servo signal corresponding to the output signal of the photodetector 118. The aperture actuator 114 is driven so that the servo signal approaches 0, and the aperture filter 113 is positioned. If the driving amount of the aperture filter 113 at this time is detected by a position detection sensor 115 (for example, PSD: Position Sensitive Detector), the relative position error of the reproduction light 110 with respect to the aperture filter 113, that is, the positional deviation amount of the book 108 with respect to the reference light 102 is obtained. Recognize. This optical means drives the light aperture filter 113, and the photodetector that detects only the light quantity has a high response speed, so that it is possible to detect the amount of displacement at high speed.

Details of the aperture filter 113 and the photodetector 118 will be described with reference to FIGS. FIG. 2 is a diagram illustrating a configuration example of the aperture filter 113 and the photodetector 118, and FIG. 3 is a diagram illustrating an example of light amount detection on the light receiving surface of the photodetector 118.

FIG. 2A shows an example of the aperture filter 113, and the X direction in the figure corresponds to the circumferential direction 123 of the medium. A transmission region 201 through which the reproduction light 110 passes is provided at the center, four divided

wavelength plate regions

202a, 202b, 202c, and 202d are provided around the transmission region 201, and a light blocking region 203 is provided outside the transmission region 201. The light blocking region 203 blocks unnecessary light other than the 0th-order light diffracted from the reproduction target book 108 in the reproduction light 110 or unnecessary light diffracted from an adjacent book other than the reproduction target book 108 and irradiates the image sensor 120. Do not be. FIG. 2B shows an example of the light receiving surface pattern of the photodetector 118. The light receiving surface 206 is divided into light receiving regions A, B, C, and D by dividing

lines

204 and 205, and the amount of light received is determined in each region. A corresponding signal is output.

3 shows the relative positional relationship of the reproduction light 110 with respect to the aperture filter 113 in the upper stage, and the light receiving state on the light receiving surface 206 of the photodetector 118 corresponding to the relative positional relationship shown in the upper stage. The X direction in the figure corresponds to the circumferential direction 123 of the medium as in FIG.

FIG. 3A shows a state in which the reproduction light 110 passes through the transmission region 201 of the aperture filter 113. In this case, since the relative position error of the reproduction light 110 with respect to the aperture filter 113 is within a predetermined range, and the position detection light of the book 108 is not irradiated to the photodetector 118, from any of the light receiving areas A, B, C, and D However, no signal is output. (B) shows a state where the relative position of the reproduction light 110 with respect to the aperture filter 113 is shifted in the + X direction. The relative position error in the + X direction exceeds the predetermined range, and the position detection signal light 1103 of the book 108 is applied to the light receiving region A of the photodetector 118. (C) shows a state where the relative position of the reproduction light 110 with respect to the aperture filter 113 is shifted in the −X direction. The relative position error in the −X direction exceeds a predetermined range, and the position detection signal light 1105 of the book 108 is applied to the light receiving region B of the photodetector 118.

Here, if the signals obtained from the light receiving areas A and B are expressed as SigA and SigB, the position error signal SX in the X direction is obtained by (Equation 1), and the relationship between the relative position error in the X direction and the position error signal SX. Is a linear relationship.
(Formula 1) SX = SigA-SigB
The aperture actuator 114 is driven so that SX approaches 0, and the aperture filter 113 is positioned. When the driving amount of the aperture filter 113 at this time is detected by a position detection sensor (for example, PSD), the relative position error of the reproduction light 110 with respect to the aperture filter 113, that is, the positional deviation amount of the book 108 with respect to the reference light 102 is known.

Here, the relationship between the detection drive amount E of the aperture filter 113 and the positional deviation amount D of the book 108 is expressed by the following (formula 2) depending on the magnification (ratio of the focal length f1 of the relay lens 112 and the focal length f2 of the objective lens 111). Therefore, the positional deviation amount D of the book 108 can be obtained from the detection drive amount E of the aperture filter 113.
(Formula 2) E = D · (f1 / f2)
In FIG. 2, four wavelength plate regions are provided around the transmission region 201 of the aperture filter 113 and four light receiving regions are provided on the light receiving surface 206 of the photodetector 118. However, the present invention is not limited to this. For example, if the amount of positional deviation between the reference beam 102 and the reproduction target book 108 in the circumferential direction of the medium that is the X direction in FIG. There may be two light receiving regions on the two wavelength plate regions and the light receiving surface 206 of the photodetector 118. That is, the aperture filter 113 shown in the figure has the

wave plate regions

202a and 202b, and the light receiving surface 206 has the light receiving regions A and B.

The positional deviation amount D of the book 108 can be detected by the optical means described above, and the subsequent operation will be described below.

The book position deviation detection unit 127 is connected to the position detection sensor 115 and the signal generation circuit 121, stores the position deviation detection result of the book 108 with respect to the reference light 102, and transmits the result to the reference light correction angle calculation unit 129. Further, the position information of the medium 107 in the radial direction 124 is transmitted from the reproduction radius position detection unit 135 to the reference light correction angle calculation unit 129. Further, irradiation angle information of the reference light 102 in the medium circumferential direction 123 is transmitted from the angle control circuit 125 of the angle variable mirror 103 to the reference light correction angle calculation unit 129.

The reference light correction angle calculation unit 129 calculates the correction angle of the reference light in the medium radial direction 124 from the transmitted information, stores the result, and transmits the result to the reference light angle change command unit 130. The reference light angle change command unit 130 transmits the command value of the correction angle to the angle control circuit 125 of the angle variable mirror 103 and controls the angle control circuit 125. The angle control circuit 125 performs feedback control by driving the actuator 104 and the output from the angle sensor 105, and changes the angle of the angle variable mirror 103 so as to change the incident angle of the reference light in the medium radial direction 124.

In this way, the irradiation angle of the reference beam 102 to the reproduction target book 108 in the medium radial direction 124 is changed. When the book to be reproduced on the medium moves from the current position to another position, the correction angle of the reference beam 102 in the medium radial direction 124 is calculated again as described above, and the book to be reproduced is reproduced. It is comprised so that the reference light irradiation angle with respect to may be changed.

Here, as a means for changing the reference light irradiation angle with respect to the reproduction target book, for example, the medium 107 may be tilted without changing the reference light irradiation angle. However, since the medium 107 is heavy, the angle cannot be changed at high speed. . On the other hand, in this embodiment, since the lightweight variable angle mirror 103 is driven, the angle can be changed at high speed.

Here, the parameters for determining the correction angle φ2 of the reference light 102 in the medium radial direction 124 and the derivation of φ2 will be described with reference to FIGS. First, the relative shift state between the reference beam 102 and the reproduction target book 108 will be described with reference to FIG. FIG. 4A shows a relative shift state between the reference beam 102 and the reproduction target book 108 that occurs when the medium 107 is rotated in the direction 402 around the rotation center 401 and the book 108 is reproduced.

(State 1) is an ideal state with no relative deviation, and can be reproduced without any particular problem. (State 2) shows a state in which a relative shift occurs. When the shift is in the direction of the arrow 403, a translational shift + D and a clockwise rotation angle + θ occur simultaneously with respect to the reference beam 102. On the other hand, when the direction is shifted in the direction of the arrow 404, a translational shift −D and a counterclockwise rotation angle −θ occur simultaneously with respect to the reference beam 102.

FIG. 5 shows the book 108 to be reproduced assuming (state 2) in FIG. 4. By tilting the variable angle mirror 103, the reference light 102 is incident at a predetermined angle φb in the circumferential direction 123 of the medium, and page reproduction is performed. Assumes to do. In this state, the reproduction target book 108 is inclined by θ with respect to the reference light 102, so that when viewed from the book 108, the reproduction target book 108 is in a direction of a line 502 connecting the rotation center 401 of the medium and the center 501 of the book 108. The reference light 102 is tilted by φ1 and irradiated with the reference light. Therefore, if the correction angle φ2 is set so that the reference beam 102 is moved in the direction of the line 502, φp becomes zero.
(Formula 3) φ1 = φb · Sinθ
(Formula 4) φ2 = −φb · Sinθ
(Formula 5) φp = φ1 + φ2 = 0
FIG. 4B described above is a diagram specifically showing the circumferential position displacement amount D of the reproduction target book 108, and the following relational expression is geometrically established.
(Expression 6) D = R · Sinθ
Further, more simply, since the book rotation amount θ assumed in the actual apparatus operation is sufficiently small, the following relational expression may be considered by approximating Sinθ≈θ.
(Formula 6 ′) D = R · θ
The correction angle φ2 is calculated from (Equation 4) and (Equation 6 ′) by the following (Equation 7), and the medium circumferential incident angle φb of the reference light and the deviation of the reference light and the book to be reproduced in the medium circumferential direction are calculated. It can be seen that it is determined by D and the parameter of the reference light position R measured from the rotation center of the medium. The parameter information is transmitted to the reference light correction angle calculation unit 129 in FIG. 1, and the reference light correction angle calculation unit 129 calculates the reference light correction angle φ2 using the calculation formula of (Formula 7). it can.
(Expression 7) φ2 = −φb · Sin (D / R)
This embodiment has the following characteristics regarding the calculation of the correction angle φ2 of the reference light 102 in the medium radial direction 124.

The first feature is an angle correction operation for changing the reference light correction angle φ2 in accordance with the medium radial position R of the reference light. FIG. 6 is a diagram showing the relationship between the deviation amount of the reproduction target book and the correction angle. In FIG. 6B, the horizontal axis indicates the medium circumferential direction deviation D of the book to be reproduced, the left vertical axis indicates φp, the right vertical axis indicates φ2, and the reference light medium incident angle φb in the medium circumferential direction is shown. 48 degrees was set. FIG. 6A shows a case where the reference light position R measured from the rotation center of the medium is set to the innermost radius of the medium 24 mm in FIG. 6A and to the outermost radius of the medium 64 mm in FIG.

6A, a dotted characteristic line 601 indicates φ1 in (Expression 3). For example, when D is ± 100 μm, it reaches ± 0.2 degrees and cannot be reproduced. On the other hand, the characteristic line 602 of the one-dot chain line indicates φ2 in (Expression 4), and the angle deviation φp can be set to 0 (straight line 603), so that stable reproduction is possible. In FIG. 6B, a dotted characteristic line 604 indicates φ1 in (Equation 3). For example, when D is ± 100 μm, it reaches ± 0.1 ° and cannot be reproduced. On the other hand, a dashed-dotted characteristic line 605 indicates φ2 in (Equation 4), and the angle deviation φp can be set to 0 (straight line 606), thereby enabling stable reproduction.

Particularly, φ1 varies depending on the medium radial position R of the reference light. For example, from the characteristic line 601 in FIG. 6A and the characteristic line 604 in FIG. 6B, the innermost radius 24 mm is approximately twice as large as the outermost radius 64 mm. Therefore, in this embodiment, an angle correction operation for changing the reference light correction angle φ2 according to the medium radius position R of the reference light 102 is performed. By this angle correction operation, the angle deviation φp can be set to 0 regardless of the medium radial position R, and stable reproduction is possible.

The second feature is an angle correction operation in which the reference light correction angle φ2 is changed according to the incident angle φb of the reference light in the circumferential direction of the medium. FIG. 7 is a diagram showing the relationship between the incident angle of the reference light and the correction angle. A plurality of pages are recorded in the book 108 by angle multiplex recording in which the medium circumferential incident angle φb of the reference light is set within a predetermined range, for example, 33 degrees to 63 degrees, and is changed at predetermined angular intervals. When reproducing these pages, the angle of incidence φb of the reference beam 102 is changed at a predetermined angular interval from 33 degrees to 63 degrees by changing the variable angle mirror 103 in the circumferential direction 123 of the medium at a predetermined angular interval. Let FIG. 7 shows an example in which R is set to 24 mm, D is set to 100 μm, the horizontal axis incident angle φb of the reference light in the horizontal axis, the left vertical axis to the angular deviation φp, and the right vertical axis to the correction angle φ2. It is the graph shown. A dotted characteristic line 701 indicates φ1 in (Equation 3). For example, when φb is 33 degrees, it reaches about 0.15 degrees, and when φb is 63 degrees, it reaches 0.25 degrees and reproduction becomes impossible. . On the other hand, the characteristic line 702 of the alternate long and short dash line indicates φ2 in (Equation 4), and the angle deviation φp can be set to 0 (straight line 703), thereby enabling stable page data reproduction.

Particularly, φ1 varies depending on the incident angle φb of the reference light. For example, from the characteristic line 701, when φb is 63 degrees, the value is about twice as large as when φb is 33 degrees. Therefore, it is necessary to change φ2 correspondingly. Therefore, in the present embodiment, when each page data is reproduced, an angle correction operation for changing the correction angle φ2 according to the incident angle φb of the reference light 102 is performed.

This angle correction operation makes it possible to set the angle deviation φp to 0 regardless of φb, and stable page data reproduction is possible. As described above, since the allowable range of D can be expanded from the conventional ± 10 μm, there is an effect of improving the reproduction reliability of the apparatus.

The trigger of the reference light angle correction operation described above and the reproduction operation flow will be described with reference to FIG. FIG. 8 shows a playback operation flow.

The trigger for the reference beam angle correction operation is the timing of moving the book to be played. When the reproduction of page data in a predetermined book is completed and moved to another reproduction target book, the feed rotation angle of the spindle motor is controlled, and the book positioning operation is performed with respect to the reference light. At this time, the positional deviation amount D of the book 108 with respect to the reference beam 102 does not become the same as the previous book reproduction and changes. That is, the correction angle φ2 of the reference beam 102 has changed from the previous book reproduction. Therefore, it is necessary to change φ2 corresponding to the book movement.

Therefore, in this embodiment, an angle correction operation for changing the correction angle φ2 in accordance with the movement of the book to be reproduced is performed. Further, when each page is reproduced, as described in the second feature, an angle correction operation for changing the reference light correction angle φ2 according to the incident angle φb of the reference light 102 is performed.

FIG. 8 shows a playback operation flow. First, in step S <b> 801, the book is moved by controlling the feed rotation angle of the spindle motor, and the target book on the medium 107 is positioned with respect to the reference beam 102. At this time, the medium radial position of the reference beam 102 is detected. In step S802, the irradiation angle in the medium circumferential direction 123 of the reference beam 102 with respect to the target book 108 in the medium 107 is set to an angle necessary for desired page reproduction. In step S803, the irradiation angle of the reference light 102 in the medium circumferential direction 123 is detected, and the target book 108 is irradiated with the reference light 102. In step S804, the amount and direction of the positional deviation between the target book and the reference light in the circumferential direction of the medium 107 are detected. In step S805, based on the information acquired up to step S804 (the medium radial position of the reference light 102, the irradiation angle in the medium circumferential direction 123, and the amount of positional deviation from the target book in the circumferential direction of the medium 107), the reference light 102 The correction angle of the irradiation angle in the medium radial direction 124 is calculated, and the irradiation angle of the reference light 102 in the medium radial direction 124 is corrected and changed. Thereafter, page reproduction is executed in step S806.

If the page reproduction is executed in S806, it is determined whether or not another page is reproduced in S807. When reproducing another page, the process returns to step S802, and the operations from step S802 to step S805 are performed again. Each time the playback page changes, the irradiation angle of the reference beam 102 in the medium circumferential direction 123 changes. Accordingly, the correction angle of the irradiation angle of the reference beam 102 in the medium radial direction 124 is changed to the previous page playback. Change to a value different from the time. Thereafter, another page reproduction is executed in step S806.

When the page reproduction is completed, it is determined whether or not another book is reproduced in S808. When reproducing another book, the process returns to step S 801, the book is moved, and the target book 108 on the medium 107 is positioned with respect to the reference beam 102. The operations from step S802 to step S806 are performed again.

Since the amount of positional deviation between the target book and the reference light in the circumferential direction of the medium 107 changes every time the book to be reproduced moves, the correction angle of the irradiation angle of the reference light 102 in the medium radial direction 124 is set accordingly. Change to a value different from the previous book playback.

As mentioned above, although the Example of a present Example was described, it is as follows when the effect acquired is put together.
(1) Regarding the disturbance during book reproduction, that is, the relative deviation between the book to be reproduced and the reference beam in the circumferential direction of the medium, the allowable value can be increased, so that the reliability of hologram reproduction can be improved.
(2) As a means for detecting deviation information between the book to be reproduced and the reference light, an aperture filter which is a light optical element rather than a heavy medium is driven, and a light detector dedicated to light amount detection is used instead of an image pickup element for detecting image information. As a result, deviation information can be detected at high speed. Furthermore, as a means for changing the relative angle between the book to be reproduced and the reference light, the reflection mirror, which is a light optical element rather than a heavy medium, is feedback-controlled based on deviation information from the deviation information detection means, so that the angle Changes can be made at high speed. Therefore, the reproduction speed can be increased.

In addition, a present Example is not limited to the said Example, Various modifications are included.

For example, in the above-described embodiment, as described with reference to FIG. 1, the detection optical system including the aperture filter 113, the PBS 116, the detection lens 117, and the photodetector 118 is provided as an optical detection unit for the book 108 positional deviation. . For example, a detection optical system including a detection lens, for example, a photodetector having a two-divided light receiving surface may be used so as to face the objective lens 111 with the medium 107 interposed therebetween. Note that the photodetector may be an image sensor such as a CCD or CMOS. In the above embodiment, one angle variable mirror is inclined in two axial directions, ie, the circumferential direction and the radial direction of the medium. However, the first variable angle mirror is arranged in the circumferential direction of the medium. The variable angle mirror may be inclined in the radial direction of the medium.

In the first embodiment, the case where the recording position on the medium of the book (hereinafter referred to as a track) is ideal has been described, but an error in recording the medium includes the eccentricity of the track. Therefore, in this embodiment, reference beam angle correction when the track is decentered will be described.

FIG. 9 shows the eccentricity of the track generated at the time of recording. 901 indicates a medium, 903 indicates an ideal track at a predetermined radius R, and 902 indicates the center of the ideal track 903. Reference numeral 905 denotes a recording track, and the center 904 of the track 905 is decentered from the center 902 by Δ.

When recording, it is conceivable to correct the eccentricity by driving the medium 901 so that the eccentricity Δ becomes 0. However, if this eccentricity correction is performed, vibration occurs in the medium 901. Since hologram recording requires that the vibration of the medium be sufficiently attenuated, if eccentricity correction is performed, a waiting time is required until the vibration is settled. As a result, improvement in the recording speed of the apparatus is hindered. Therefore, there is a need for a reproduction method suitable for improving the recording speed of the apparatus, that is, capable of compensating for the influence of track eccentricity that has occurred during recording, and the details thereof will be described below.

FIG. 10 shows a hologram reproducing apparatus according to the present embodiment, where 1006 is a hologram reproducing apparatus, 1001 is an optical pickup, and 1005 is an optical system of the optical pickup 1001. In addition, the same part as FIG. 1 of Example 1 is shown using the same code | symbol as FIG. The hologram reproducing device 1006 is connected to the external control device 91 via the input / output control circuit 90. When reproducing, the image information output from the image sensor 120 of the optical pickup 1001 is converted into an electric signal by the signal processing circuit 85, and this electric signal is transmitted to the external control device 91 by the input / output control circuit 90.

The optical pickup 1001 of this embodiment is different from the optical pickup 11 shown in FIG. 1 in that an eccentricity detecting optical means for detecting the eccentricity Δ of the track 905 is added. The decentering detection optical means includes a detection lens 1002 and a light detector 1003 provided so as to face the objective lens 111 with the medium 107 interposed therebetween. The reference light 102 irradiated to the book 108 is divided into transmitted light directed to the mirror 109 and diffracted light 1004 directed to the detection lens 1002, and among these, the diffracted light 1004 is used as the eccentricity detection light. The diffracted light 1004 is collected by the detection lens 1002 and irradiated to the photodetector 1003.

FIG. 11 shows the light receiving surface of the photodetector 1003. The light receiving surface 1101 of the photodetector 1003 is divided into four

light receiving areas

1105a, 1105b, 1105c, and 1105d by a dividing line 1103 and a dividing line 1104, and a light spot 1102 is irradiated to these light receiving areas. The X direction in the figure corresponds to the circumferential direction 123 of the medium 107, and the Y direction corresponds to the radial direction 124 of the medium 107.

When the position of the medium moves, the center of the light spot 1102 moves according to the amount and direction of the medium, and the eccentric amount Δ of the track 905 can be detected by rotating the medium 107 in the circumferential direction 123. . The eccentricity detection unit 1006 stores the detection result of the eccentricity amount Δ and transmits it to the reference light correction angle calculation unit 129. Note that the relationship between the amount of eccentricity Δ and the amount of movement of the light spot 1102 is calibrated during assembly adjustment of the optical pickup. Since other parts are the same as those in the first embodiment, description thereof is omitted here.

Hereinafter, the reference beam correction angle necessary for the radial direction 124 of the medium is derived when the book is reproduced with the recording track being decentered with reference to FIG.

FIG. 12A shows a state where the recording track 905 is decentered by Δ from the ideal track 903, as shown in FIG. The book 108 is inclined at an angle α when viewed from the center 1204 of the recording track 905, and the angle α is expressed by the following (formula 8).
(Formula 8) α = Δ / R
FIG. 12B shows a state in which the book 108 is on the ideal track 903 and the shift amount D is generated in the book positioning operation as shown in the first embodiment. The book 108 is inclined by an angle θ as viewed from the center 902 of the ideal track 903, and this angle θ is expressed in the same manner as in (Equation 6) or (Equation 6 ′) of the first embodiment.
FIG. 12C shows a state in which the book positioning operation is performed in a state where the recording track 905 is decentered by Δ from the ideal track 903, and corresponds to a state in which the above (a) and (b) are combined. Therefore, the book 108 is inclined by an angle (α + θ) when viewed from the rotation center 1201 of the medium, and this angle (α + θ) is expressed by the following equation from (Equation 6 ′) and (Equation 8).
(Formula 9) α + θ = (Δ + D) / R
In the present embodiment, the reference light correction angle φ2 necessary for the radial direction 124 of the medium can be calculated by the following formula in which θ in (Formula 4) of the first embodiment is replaced by (α + θ).
(Formula 10) φ2 = −φb · Sin (α + θ) = − φb · Sin [(Δ + D) / R]
Finally, a reproduction operation flow by the reference light angle correction operation of the present embodiment will be described with reference to FIG. Steps similar to those in FIG. 8 are denoted by the same reference numerals, and description thereof is omitted. First, in step S1301, the target track is moved, and in step S1302, the spindle motor is rotated to detect the eccentricity of the recording track. In step S <b> 801, the feed rotation angle of the spindle motor is controlled to move the book, and the target book on the medium 107 is positioned with respect to the reference beam 102. At this time, the medium radial position of the reference beam 102 is detected. In step S802, the irradiation angle in the medium circumferential direction 123 of the reference beam 102 with respect to the target book 108 in the medium 107 is set to an angle necessary for desired page reproduction. In step S803, the irradiation angle of the reference light 102 in the medium circumferential direction 123 is detected, and the target book 108 is irradiated with the reference light 102. In step S804, the amount and direction of the positional deviation between the target book and the reference light in the circumferential direction of the medium 107 are detected. Information acquired up to step S1204 in step S1303 (the medium radial position of the reference beam 102, the amount of eccentricity of the recording track, the irradiation angle in the medium circumferential direction 123, and the amount of positional deviation from the target book in the circumferential direction of the medium 107) The correction angle of the irradiation angle of the reference light 102 in the medium radial direction 124 is calculated, and the irradiation angle of the reference light 102 in the medium radial direction 124 is corrected and changed. Thereafter, page reproduction is executed in step S806.

Reproduction of another page (S807) and reproduction of another book (S808) are the same as in FIG.

Book reproduction ends, and it is determined in step S2104 whether another track is to be reproduced. When reproducing another track, the process returns to step S2101 to move to the target track. The operations from step S2101 to step S2104 are performed again.

The present embodiment is characterized by an angle correction operation in which the reference light correction angle φ2 is changed in accordance with the amount of eccentricity of the recording track of the medium. Since the influence of the track eccentricity generated during recording can be compensated, the recording of the reproducing method apparatus Speed can be improved.

FIG. 14 shows the configuration of the optical pickup in this embodiment. The difference between the present embodiment and the first embodiment is that the optical pickup 1401 includes a wedge prism 1403.

Hereinafter, description will be made with reference to FIG. Reference numeral 1401 denotes an optical pickup in the present embodiment, and the optical pickup 1401 is connected to the signal generation circuit 86, servo control circuit 84, servo signal generation circuit 83, and signal processing circuit 85 shown in FIG. Thus, a hologram reproducing apparatus is configured. In addition, the same part as Example 1 is shown using the same code | symbol as FIG.

The reference light 102 passes through the wedge prism 1403 having a predetermined apex angle, is reflected by the mirror 1407, passes through the scanner lens 106, and is irradiated onto the medium 107 at a predetermined incident angle. The wedge prism 1603 is held by an actuator 1604 that is rotationally driven in one axis direction, and the incident angle of the medium 107 in the radial direction 124 can be changed by rotationally driving the wedge prism 1403. An actuator 1404 and an angle sensor 1405 for detecting the rotation angle of the wedge prism 1403 are connected to the pitch angle control circuit 1619 and control the wedge prism 1403 to a desired rotation angle by feedback control. The mirror 1407 is held by an actuator 1406 that is rotationally driven in one axis direction, and the incident angle in the circumferential direction 123 of the medium 107 can be changed by rotationally driving the mirror 1407. An actuator 1406 and an angle sensor 1409 for detecting the rotation angle of the mirror 1407 are connected to a Bragg angle control circuit 1418 and control the mirror 1407 to a desired rotation angle by feedback control.

The reference light 102 irradiated on the book 108 is divided into transmitted light directed to the mirror 109 and diffracted light 1410 directed to the detection lens 1611. This diffracted light 1410 is separated into two polarized light beams having different polarization directions by the polarization separation element 1602. Has been. The light in one polarization direction passes through the PBS 1413 and is collected on the photodetector 1415 by the detection lens 1414. The light in the other polarization direction is reflected by the PBS 1413 and collected by the detection lens 1416 on the photodetector 1417. Signals obtained by the

photodetectors

1415 and 1417 are used by the Bragg angle control circuit 1418 to generate the control angle signal of φb.

The irradiation angle information regarding the medium circumferential direction 123 of the reference light 102 is transmitted from the Bragg angle control circuit 1418 to the reference light correction angle calculation unit 129. The reference light correction angle calculation unit 129 calculates a correction angle of the reference light in the medium radial direction 124 from the transmitted information, stores the result, and transmits the result to the reference light angle change command unit 130. The reference light angle change command unit 130 transmits the command value of the correction angle to the pitch angle control circuit 1419 and controls the pitch angle control circuit 1419. The pitch angle control circuit 1619 performs feedback control by driving the actuator 1404 and the output from the angle sensor 1605 to change the angle of the wedge prism 1403 in the medium radial direction 124. In this way, the irradiation angle of the reference beam 102 to the reproduction target book 108 in the medium radial direction 124 is changed.

With the configuration of this embodiment, the incident angle of the reference beam 102 in the circumferential direction 123 can be controlled at high speed during page reproduction. Since the scanning speed of the incident angle φb in the medium circumferential direction of the reference light is increased, it is possible to provide a hologram reproducing apparatus having an improved reproducing speed as compared with the hologram reproducing apparatus of the first embodiment.

The first, second, and third embodiments described above have been described in detail for easy understanding of the present embodiment, and are not necessarily limited to those having all the configurations described. Absent. Further, the present invention is not limited to the above-described embodiments, and various modifications are included, and specific examples include the following examples.

As a modified example 1, in the hologram reproducing apparatus for reproducing the page data by irradiating the hologram medium on which the page data is angle-multiplexed recorded with reference light, and receiving the generated diffracted light as reproduction light by the imaging device, A correction optical unit that optically detects the shift state of the reproduction target area of the hologram medium, and correction that changes the irradiation angle of the reference light based on the shift information of the reproduction target area acquired from the detection optical unit. A hologram reproducing apparatus characterized in that:

As a second modification, the hologram reproduction apparatus according to the first modification, wherein the correction is performed when the reproduction target area is moved.

As a third modification, the hologram reproduction apparatus according to the first modification, wherein the correction is performed when the reproduction target page is changed.

As Modification Example 4, in Modification Example 1, the detection optical unit is provided in an optical path between the medium and the image sensor, and the aperture filter optical element that causes the image sensor to receive only the 0th-order light of the diffracted light; and A detection lens, a photodetector, and an actuator for driving the aperture filter optical element are provided to detect a shift state of a reproduction target area of the hologram medium as a change in state of zero-order light passing through the aperture filter optical element. Hologram playback device.

As a fifth modified example, there is a reproducing method of a hologram apparatus for reproducing the page data by irradiating a hologram medium on which page data is angle-multiplexed recorded with reference light and receiving the generated diffracted light as reproducing light by an imaging device. A first step of detecting a relative positional shift amount of the reference light and the reproduction target area in the medium circumferential direction by an optical detection means other than the image pickup device; a medium radial position of the reproduction target area and the detection; The second step of calculating the amount of inclination of the reproduction target area in the medium circumferential direction from the relative positional deviation amount, and the reference from the calculated inclination amount and the irradiation angle of the reproduction target area with respect to the medium circumferential direction A third step of calculating a correction angle of light in the medium radial direction, and changing an irradiation angle of the reference light in the medium radial direction based on the calculated correction angle Reproducing method of a hologram reproducing apparatus, characterized in that it comprises a fourth step.

Further, the control lines indicate what is considered necessary for the explanation, and not all control lines are necessarily shown on the product.

DESCRIPTION OF SYMBOLS 10 Hologram reproducing | regenerating apparatus, 11 Optical pick-up 101 Optical system of optical pick-up 11, 102 Reference light, 103 Reference light angle variable mirror, 104 Actuator, 105 Angle sensor, 107 Hologram medium, 108 Book 113 Aperture filter, 117 Detection lens, 118 Light Detector, 115 position detection sensor 123 medium circumferential direction, 127 book position deviation detection unit, 129 reference light correction angle calculation unit, 130 reference light angle change command unit, 135 reproduction radius position detection unit

Claims

The recording was performed by irradiating the recording medium on which the hologram was angle-multiplexed recorded by changing the incident angle of the reference light in the first direction, and receiving the generated diffracted light as reproduction light by the imaging device. In a hologram reproducing apparatus for reproducing a hologram,
A reference light angle adjusting unit for adjusting a medium incident angle at which the reference light is incident on the recording medium;
An aperture filter having an opening through which the reproduction light from the recording medium is incident and through which the reproduction light is transmitted;
A light detection unit that detects light emitted from the aperture filter and outputs a signal based on the detected light;
A position for detecting a relative displacement amount between the recording position of the reproduction target hologram and the irradiation position on the recording medium of the reference light for reproducing the reproduction target hologram, based on the signal output from the light detection unit A deviation detection unit;
With
The reference light angle adjusting unit adjusts a medium incident angle in a second direction perpendicular to the first direction of the reference light based on a positional shift amount detected by a positional shift detection unit. Hologram playback device.
The hologram reproducing apparatus according to claim 1,
A reproduction position detecting unit for detecting a radial position of the hologram to be reproduced on the recording medium;
The reference light angle adjustment unit adjusts the medium incident angle of the reference light in the second direction based on the radial position of the reproduction target hologram and the shift amount in the first direction on the recording medium. A hologram reproducing apparatus characterized by that.
The hologram reproducing apparatus according to claim 1,
The reference light angle adjustment unit adjusts the medium incident angle in the second direction of the reference light based on the medium incident angle in the first direction of the reference light irradiated when reproducing the hologram to be reproduced. A hologram reproducing apparatus characterized in that:
The hologram reproducing apparatus according to claim 2,
The reference light angle adjustment unit further determines the medium incident angle of the reference light in the second direction based on the medium incident angle of the reference light irradiated when reproducing the reproduction target hologram. A hologram reproducing apparatus characterized by adjusting.
The hologram reproducing apparatus according to claim 1,
The positional deviation detection unit generates a position error signal of the aperture filter unit based on the signal output from the light detection unit,
The aperture filter is driven based on the position error signal,
The positional deviation detection unit detects the positional deviation amount based on the driving amount of the aperture filter.
A hologram reproducing apparatus characterized by that.
The hologram reproducing apparatus according to claim 1,
The hologram reproducing apparatus, wherein the reference light angle adjusting unit adjusts the medium incident angle in the second direction when the reference light irradiation position is moved.
The recording was performed by irradiating the recording medium on which the hologram was angle-multiplexed recorded by changing the incident angle of the reference light in the first direction, and receiving the generated diffracted light as reproduction light by the imaging device. In a hologram reproduction method for reproducing a hologram,
A reference light angle adjusting step for adjusting a medium incident angle at which the reference light is incident on the recording medium;
A light detection step of detecting light that is incident on the reproduction light from the recording medium and that is emitted from an aperture filter having an opening through which the reproduction light is transmitted, and that outputs a signal based on the detected light;
A position for detecting a relative displacement amount between the recording position of the reproduction target hologram and the irradiation position on the recording medium of the reference light for reproducing the reproduction target hologram, based on the signal output in the light detection step. A slip detection step;
With
In the reference light angle adjusting step, a medium incident angle in a second direction perpendicular to the first direction of the reference light is adjusted based on a positional shift amount detected in the positional shift detection step. Playback method.
The recording is performed by irradiating the reference light onto the recording medium on which the hologram is angle-multiplexed recorded by changing the incident angle of the reference light on the recording medium in the first direction and receiving the generated diffracted light as reproduction light. In a hologram reproducing method in a hologram reproducing apparatus for reproducing a hologram,
The hologram reproducing apparatus includes:
A reference light angle adjusting unit for adjusting a medium incident angle at which the reference light is incident on the recording medium;
An aperture filter having an opening through which the reproduction light from the recording medium is incident and through which the reproduction light is transmitted;
With
Adjusting the medium incident angle of the reference light in the first direction by the reference light angle adjustment unit;
Adjusting the position of the aperture filter;
Adjusting the medium incident angle of the reference light in a second direction perpendicular to the first direction by the reference light angle adjusting unit.