WO2014083944A1 - Hologram recording and/or playing device - Google Patents

Abstract

An objective of the present invention is to provide a hologram recording and/or playing device whereby it is possible to accurately detect an angle of inclination of a holographic medium, and to carry out a correction. The hologram recording/playing device comprises a medium attitude detection unit which is configured, in at least a pair of sites, of a combination of a light source which emits a light beam upon the holographic medium and a light location detection unit which receives the light beam which is reflected by the holographic medium. The medium attitude detection means are positioned in different locations in the radius direction and/or a tangent line direction which is orthogonal to the radius direction.

Description

Hologram recording and / or reproducing apparatus

The present invention relates to a hologram recording and / or reproducing apparatus that irradiates signal light and reference light to a hologram recording medium to record and / or reproduce information.

At present, the Blu-ray Disc (TM) standard using a blue-violet semiconductor laser has made it possible to commercialize an optical disc having a recording capacity of about 50 GB even for consumer use. In the future, it is desirable to increase the capacity of optical disks to the same extent as the capacity of an HDD (Hard Disk Drive) of 100 GB to 1 TB.

However, in order to realize such a large-capacity optical disc, it is necessary to use a new high-density technology different from the high-density technology by shortening the wavelength and increasing the objective lens NA.

While research on next-generation storage technology is being conducted, hologram recording technology that records digital information using holography is drawing attention.

In the hologram recording technology, signal light having information of page data two-dimensionally modulated by the spatial light modulator is superimposed on the reference light inside the recording medium, and the interference fringe pattern generated at that time is superimposed in the recording medium. This is a technology for recording information on a recording medium by causing refractive index modulation.

When reproducing information, when the recording medium is irradiated with the reference light used for recording, the hologram recorded in the recording medium acts like a diffraction grating to generate diffracted light. The diffracted light is reproduced as the same light including the recorded signal light and phase information.

The reproduced signal light is two-dimensionally detected at high speed using a photodetector such as a CMOS or a CCD. Thus, the hologram recording technology enables two-dimensional information to be recorded on the optical recording medium at once by one hologram and to further reproduce this information, and the incident angle of the reference light to the hologram medium By performing so-called angle multiplex recording in which a large number of holograms are formed, it is possible to achieve large-capacity and high-speed recording and reproduction of information.

In the case of the detachable hologram medium, the hologram medium is inclined due to the mechanical configuration of the place where the hologram medium is installed, etc., and the angle of the reference light incident on the hologram medium at the time of reproduction is different from that at recording. There was a possibility that the recorded information could not be reproduced. Therefore, in Japanese Patent Application Laid-Open No. 2006-179080 (Patent Document 1), “it is incoherent with respect to the reproduction reference beam and whether the hologram medium is inclined with respect to the reference position or not A tilt detection beam for detection is made incident on the hologram medium, and after the tilt detection beam is made incident on the hologram medium, the tilt detection beam obtained through the hologram medium is received and received. A signal for correcting the tilt of the hologram medium is output based on the difference between the position and the light receiving position when the hologram medium is at the reference position, and the position of the hologram medium is corrected based on the signal. It is described as "driving".

JP, 2006-179080, A

By the way, in the method of irradiating the light beam to the hologram medium and detecting the inclination of the hologram medium by the light receiving position of the reflected light, for example, the case where the hologram medium 2 has the inclination in the radial direction will be described using FIG. . FIG. 2 shows the case where the disc-shaped hologram medium 2 is mounted at an inclination angle α. FIG. 2A shows the case where the inclination is detected on the inner periphery of the hologram medium 2, and the laser light source LDa mounted on the pickup 10 irradiates the hologram medium 2 with a light beam for inclination angle detection. The light is reflected at the position R ₀ and is received at the position r ₀ of the light receiving surface of the PSD (Position Sensitive Detector) a. On the other hand, FIG. 2 (b) is a case where the inclination is detected at the outer periphery of the hologram medium 2, and the light beam emitted from the laser light source LDa is reflected at the radial position R ₀ 'of the hologram medium 2 and the light receiving PSDa is received. The light is received at the position of r ₀ 'on the surface. The difference Δz of the distance in the focusing direction from the laser light source LDa to the reflection from the hologram medium 2 at the positions of R ₀ and R ₀ ′ which are separated by ΔR in the radial direction is
(Equation 1) Δz ≒ ΔR · tan α
Is represented by As a result, although the inclination of the hologram medium 2 is the same angle α at the inner and outer peripheries, the position of the light beam incident on the PSDa shifts from the position of r ₀ to the position of r ₀ ′. Therefore, the tilt angle of the hologram medium detected from the light receiving position in PSDa is different at the inner and outer circumferences.

That is, in the method in which the hologram medium is irradiated with the light beam and the inclination of the hologram medium is detected based on the light receiving position of the reflected light, there is a problem that the inclination angle can not be detected correctly due to the distance shift in the focusing direction.

Therefore, an object of the present invention is to provide a hologram recording and / or reproducing apparatus capable of correctly detecting the inclination angle of the hologram medium and performing correction.

The above-mentioned subject is solved by using two or more sensors, for example.

According to the present invention, it is possible to provide a hologram recording and / or reproducing apparatus capable of correctly detecting and correcting the tilt angle of the hologram medium.

It is a block diagram showing the Example of the hologram recording and reproducing apparatus of this invention. It is a figure explaining the operation | movement which detects inclination in the inner peripheral position of a hologram medium. It is a figure explaining operation which detects inclination in the perimeter position of a hologram medium. It is a figure showing the example of composition of the pick-up in a hologram recording and reproducing device. It is a figure showing the example of composition of the pick-up in a hologram recording and reproducing device. FIG. 6 is a schematic view illustrating an example of the configuration of a medium attitude detection unit. It is a figure explaining the method to detect the position of an inclination angle and a focus direction. It is a figure explaining the method to detect the position of an inclination angle and a focus direction. It is a figure explaining the method to detect the position of an inclination angle and a focus direction. It is an example of the figure showing the relation between (Δr ₁ + Δr ₂ ) and the amount z of positional deviation in the focusing direction. It is an example of the figure showing the relation between (Δr ₁ -Δr ₂ ) and the inclination angle αr. It is an example of the flowchart explaining the process from the hologram medium being inserted until it is discharged. It is an example of the flowchart explaining a recording process. It is an example of the flowchart explaining a reproduction | regeneration process. It is an example of the flowchart explaining a seek process. It is an example of the flowchart explaining a reference | standard PSD position acquisition process. It is an example of the flowchart explaining a medium inclination-angle * focus position correction process. FIG. 7 is a diagram showing an example of the arrangement of a medium attitude detection unit. FIG. 7 is a diagram showing an example of the arrangement of a medium attitude detection unit. FIG. 7 is a diagram showing an example of the arrangement of a medium attitude detection unit. FIG. 7 is a diagram showing an example of the arrangement of a medium attitude detection unit. It is a block diagram showing the 2nd Example of the hologram recording and reproducing apparatus of this invention. It is an example of the flowchart explaining the reference | standard PSD position acquisition process corresponding to the 2nd Example of a hologram recording and reproducing apparatus. It is an example of the flowchart explaining the medium inclination-angle * focus position correction process corresponding to the 2nd Example of a hologram recording reproducing apparatus. It is a block diagram showing the 3rd Example of the hologram recording and reproducing apparatus of this invention. It is an example of the flowchart explaining the reference | standard PSD position acquisition process corresponding to the 3rd Example of a hologram recording and reproducing apparatus. It is an example of the flowchart explaining the medium inclination-angle * focus position correction process corresponding to the 3rd Example of a hologram recording and reproducing apparatus. It is a block diagram showing the 4th Example of the hologram recording and reproducing apparatus of this invention.

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

An embodiment of the present invention will be described according to the attached drawings. FIG. 1 is a block diagram showing an example of the configuration of a hologram recording and reproducing apparatus that records and / or reproduces digital information using holography.

The hologram recording / reproduction device 1 is connected to an external control device 40 via an input / output control unit 11. In the case of recording, the hologram recording / reproducing apparatus 1 receives an information signal to be recorded from the external control device 40 by the input / output control unit 11. In the case of reproduction, the hologram recording / reproduction apparatus 1 transmits the reproduced information signal to the input / output control unit 11 to 40.

The pickup 3 includes a light source drive unit 30, a recording / reproducing optical system 31, a reproduction reference light optical system 32, a curing optical system 33, and a medium posture detection unit 34. A predetermined light source drive current is supplied from the light source drive unit 30 to the light sources in the recording / reproducing optical system 31 and the cure optical system 33, and each light source can emit a light beam with a predetermined light amount. The recording and reproducing optical system 31 plays a role of irradiating the reference light and the signal light to the disk-shaped hologram medium 2 and recording digital information using holography. At this time, the information signal to be recorded is sent by the controller 10 to the spatial light modulator in the recording / reproducing optical system 31 via the signal generation unit 9, and the signal light is modulated by the spatial light modulator.

When the information recorded in the hologram medium 2 is to be reproduced, a light beam for causing the reference light emitted from the recording / reproducing optical system 31 to be incident on the hologram medium 2 in the opposite direction to that at the time of recording is Generate The reproduction light reproduced by the reproduction reference light is detected by a photodetector, which will be described later, in the recording and reproduction optical system 31, and the signal processing unit 8 reproduces a signal.

The irradiation time of the reference light and the signal light irradiated to the hologram medium 2 can be adjusted by controlling the opening / closing time of the shutter in the recording / reproducing optical system 31 by the controller 10 via the shutter control unit 7.

The medium attitude detection unit 34 is composed of a pair of 34a and 34b arranged at different positions in the radial direction, and sends to the controller 10 an attitude detection signal for detecting the inclination angle of the hologram medium 2 in the radial direction and the position in the focus direction. Output. The controller 10 detects the tilt angle and focus position of the hologram medium 2 in the radial direction based on the attitude detection signal, and the radial direction tilt control unit 16 controls the radial direction tilt control command signal and the focus control unit 17 performs the focus control command signal. Output. The radial tilt control unit 16 can change the tilt angle of the hologram medium 2 in the radial direction by controlling the radial direction tilt drive unit 13 based on the radial direction tilt control command signal. The focus control unit 17 can change the position of the hologram medium 2 in the focus direction by controlling the focus drive unit 14 based on the focus control command signal. Further, a memory 20 is connected to the controller 10 so that various adjustment and learning results can be stored or read out.

The medium rotation drive unit 4, the rotation angle detection unit 5, the radial direction tilt drive unit 13, and the focus drive unit 14 are mounted on a radial direction transfer drive unit 15 capable of sliding the position in the radial direction of the disc-shaped hologram medium 2. By controlling the radial direction transfer drive unit 15 through the access control unit 12, the hologram medium 2 can be moved in the radial direction by a predetermined amount, and the radial direction position for recording and reproducing the hologram can be changed.

The rotation angle detection unit 5 is used to detect the rotation angle of the hologram medium 2. When positioning the hologram medium 2 at a predetermined rotation angle, the rotation angle detection unit 5 outputs a rotation angle detection signal according to the rotation angle of the hologram medium 2, and the controller 10 uses the rotation angle detection signal to control the medium rotation control unit The medium rotation drive unit 4 is controlled via 6. Thus, the hologram medium 2 can be rotated by a predetermined angle, and the rotational direction position for recording and reproducing the hologram can be changed.

The cure optical system 33 plays a role of generating a light beam used for pre-cure and post-cure of the hologram medium 2. The pre-cure is a process prior to irradiating a predetermined light beam in advance before irradiating the reference light and the signal light to the desired position when recording information at the desired position in the hologram medium 2. The post-cure is a post-process in which after recording information at a desired position in the hologram medium 2, a predetermined light beam is irradiated to make the desired position non-rewritable.

FIG. 3 shows the recording principle in an example of the basic optical system configuration of the pickup 3 in the hologram recording and reproducing apparatus 1. The light beam emitted from the laser light source 301 is transmitted through the collimator lens 302 and is incident on the shutter 303. When the shutter 303 is open, after the light beam passes through the shutter 303, the light amount ratio of p-polarized light to s-polarized light becomes a desired ratio by the optical element 304 formed of, for example, a half wavelength plate. After the polarization direction is controlled, the light enters a PBS (Polarization Beam Splitter) prism 305.

The light beam transmitted through the PBS prism 305 acts as a signal light 306, and after the diameter of the light beam is expanded by the beam expander 308, the light beam is transmitted through the phase mask 309, the relay lens 310 and the PBS prism 311 to obtain the spatial light modulator 312. Incident to

The signal light to which information is added by the spatial light modulator 312 is reflected by the PBS prism 311, and propagates through the relay lens 313 and the spatial filter 314. Thereafter, the signal light is condensed on the hologram medium 2 by the objective lens 315.

On the other hand, the light beam reflected by the PBS prism 305 acts as the reference beam 307 and is set to a predetermined polarization direction according to the time of recording or reproduction by the polarization direction conversion element 316, and then galvano via the mirror 317 and the mirror 318. The light is incident on the mirror 319. The angle of the galvano mirror 319 can be adjusted by the actuator 320, so that the incident angle of the reference beam incident on the hologram medium 2 after passing through the lens 321 and the lens 322 can be set to a desired angle. In addition, in order to set the incident angle of reference light, it may replace with a galvano mirror and may use the element which converts the wave front of reference light.

As described above, by causing the signal light and the reference light to be incident on the hologram medium 2 so as to overlap each other, an interference fringe pattern is formed in the recording medium, and the information is recorded by writing the pattern on the recording medium. In addition, since the incident angle of the reference light incident on the hologram medium 2 can be changed by the galvano mirror 319, recording by angular multiplexing is possible.

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

FIG. 4 shows the principle of reproduction in an example of the basic optical system configuration of the pickup 3 in the hologram recording and reproduction apparatus 1. As shown in FIG. When reproducing the recorded information, as described above, the reference light is made incident on the hologram medium 2 and the light beam transmitted through the hologram medium 2 is reflected by the galvano mirror 324 whose angle can be adjusted by the actuator 323, 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 is incident on the light detector 325 so that the recorded signal can be reproduced. For example, an imaging element such as a CMOS image sensor or a CCD image sensor can be used as the light detector 325, but any element may be used as long as page data can be reproduced.

FIG. 5 shows a configuration example of the medium attitude detection unit 34, and a pair of portions 34a in which a laser light source for emitting a light beam and a light position detection element for receiving a light beam reflected by the hologram medium 2 are paired. , 34b. The laser light source has a wavelength different from that of the signal light and the reference light so as not to affect the recording or reproduction of the hologram. For example, a PSD (Position Sensitive Detector) is used as the light position detection element. The light beam LBa emitted from the laser light source LDa of the medium attitude detection unit 34a is reflected at the position Ra of the hologram medium 2, and is incident on the light position detection element PSDb of the medium attitude detection unit 34b. On the other hand, the light beam LBb emitted from the laser light source LDb of the medium attitude detection unit 34b is reflected at the position of Rb of the hologram medium 2 and is incident on the light position detection element PSDa of the medium attitude detection unit 34a. Each of PSDa and PSDb outputs an electric signal corresponding to the position of the incident light beam as an attitude detection signal.

A method of detecting the tilt angle of the hologram medium 2 and the position in the focus direction by the medium attitude detection unit 34 will be described with reference to FIG.

FIG. 6A shows a state in which the hologram medium 2 is not inclined. The light beams LBa and LBb emitted from the light emission positions La and Lb of the laser light sources LDa and LDb of the medium attitude detection unit 34 are reflected by the radial positions Ra and Rb of the hologram medium 2, and the light reception positions Pa of the light position detection elements PSDa and PSDb , Enters Pb. Here, in order to simplify the description, the distances in the focusing direction from the medium attitude detection units 34a and 34b to the hologram medium 2 are approximately the same distance d, and the angles emitted from the laser light sources LDa and LDb to the hologram medium 2 are approximately The same angle θr is used. Further, Δr indicates the distance between the positions Ra and Rb at which the light beams LBa and LBb are reflected by the hologram medium 2. At this time, the distances r ₁ and r _{2 in} the radial direction from the light emitting positions La and Lb to the light receiving positions Pa and Pb are expressed by the following equation (2).
(2)
r ₁ = r ₂ = 2 · d / tan (θr)
Next, the case where the hologram medium 2 is inclined by the angle αr and displaced by z in the focusing direction will be described with reference to FIGS. 6 (b) and 6 (c). The light beams LBa and LBb emitted from the light emission positions La and Lb of the laser light sources LDa and LDb of the medium posture detection unit 34 are reflected by the radial positions Ra 'and Rb' of the hologram medium 2, and the light position detection elements PSDa and PSDb receive light. The light is incident on the positions Pa 'and Pb'. The angles emitted from the laser light sources LDa and LDb are the same angle θr as in the case of FIG.

FIG. 6 (c) is an enlarged view of a portion where the light beam is reflected by the hologram medium 2 in FIG. 6 (b).
The hologram medium 2 is inclined by the angle αr and displaced by z in the focusing direction, whereby the position Ra ′ at which the light beam LBa is reflected deviates by z _{1 in the} focusing direction, and the position Rb ′ at which the light beam LBb is reflected is the focusing direction It is offset by z ₂ . The amounts of deviation z ₁ and z ₂ are expressed by the following equations (3) and (4).
(Number 3)
z ₁ = {z + Δr · tan (αr) / 2} / {1-tan (αr) / tan (θr)}
(Number 4)
z ₂ = {z−Δr · tan (αr) / 2} / {1 + tan (αr) / tan (θr)}
Here, when the inclination angle αr of the hologram medium 2 is small, it can be approximated as tan (αr) ≒ αr (however, the unit of αr is radian), and the equations (3) and (4) are approximated by the following equation .
(Number 5)
z ₁ ((z + Δr · αr / 2) · {1 + αr / tan (θr)}
(Number 6)
z ₂ ((z−Δr · αr / 2) · {1−αr / tan (θr)}
Further, distances r ₁ ′ and r ₂ ′ in the radial direction from the light emitting positions La and Lb to the light receiving positions Pa ′ and Pb ′ are expressed by the following equations (7) and (8).
(Number 7)
_{r 1 '= r 1/2} + (d + z 1) / tan (θr-2αr) + z 1 / tan (θr)
(Equation 8)
_{r 2 '= r 2/2} + (d + z 2) / tan (θr + 2αr) + z 2 / tan (θr)
The amount Δr ₁ and Δr ₂ of deviation of the light receiving position when the hologram medium 2 is inclined by the angle α r from the state of FIG. 6A as in FIG. 9) and (10).
(Number 9)
Δr ₁ = r ₁ '-r ₁
(Number 10)
Δr ₂ = r ₂ '-r ₂
The calculations of (Δr ₁ + Δr ₂ ) and (Δr ₁ −Δr ₂ ) are performed using the above equation.
(Equation 11)
Δr ₁ + Δr ₂ = (d + z ₁ ) / tan (θr−2αr) + z ₁ / tan (θr)
+ (D + z ₂ ) / tan (θ r + ₂ α r) + z ₂ / tan (θ r)-r ₁
(12)
Δr ₁ −Δr ₂ = (d + z ₁ ) / tan (θr−2αr) + z ₁ / tan (θr)
-(D + z ₂ ) / tan (θr + 2αr) + z ₂ / tan (θr)
The z ₁ and z ₂ of the equations (5) and (6) are substituted into the equations (11) and (12), and the inclination angle αr of the hologram medium is small and the positional deviation z in the focusing direction is the medium attitude detection unit 34a, Considering that the distance d from the point 34 b to the hologram medium 2 is sufficiently small, approximate equations (13) and (14) are obtained.
(Equation 13)
Δr ₁ + Δr ₂ 4 4z / tan (θr)
= K · z
(Equation 14)
Δr ₁ −Δr ₂ 44αr [d + {d + tan (θr) · Δr / 2} / tan ² (θr)]
= L · α r
It is understood from equations (13) and (14) that (Δr ₁ + Δr ₂ ) is proportional to the amount z of positional deviation in the focus direction, and (Δr ₁ −Δr ₂ ) is proportional to the inclination angle αr. The proportional coefficients K and L in the equations (13) and (14) are, for example, the angle θr emitted from the laser light sources LDa and LDb to the hologram medium 2 and the distance d in the focus direction from the medium attitude detectors 34a and 34b to the hologram medium 2 The deviation Δr between the positions Ra and Rb at which the light beams LBa and LBb are reflected by the hologram medium 2 is known at the time of design and can be obtained in advance.
FIG. 7 compares the cases where (Δr ₁ + Δr ₂ ) and (Δr ₁ −Δr ₂ ) are calculated without using the approximate expression and when calculated using the approximate expressions of equations (13) and (14). It is a thing. Here, the angle θr = 20 ° emitted from the laser light sources LDa and LDb to the hologram medium 2, the distance d = 15 mm in the focusing direction from the medium attitude detectors 34a and 34b to the hologram medium 2, and the light beams LBa and LBb The calculation was performed with the distance Δr = 5 mm between the positions Ra and Rb reflected by 2.

FIG. 7A shows the result of calculation of the relationship between the deviation z in the focusing direction and (Δr ₁ + Δr ₂ ) when the inclination angle αr of the hologram medium 2 is changed as a parameter. The positional deviation z in the focusing direction is proportional to (Δr ₁ + Δr ₂ ), and the approximation shown by the solid line is not used even when the inclination angle αr is changed to 0 °, 0.05 °, and 0.1 °. The case and the case where the approximate expression shown by the dotted line is used are almost overlapped, and it can be understood that the approximate expression of the equation (13) can be calculated with sufficient accuracy.

FIG. 7B is the result of calculating the relationship between the inclination angle αr of the hologram medium 2 and (Δr ₁ −Δr ₂ ) when the positional deviation z in the focusing direction is changed as a parameter. Even when the inclination angle αr of the hologram medium 2 is proportional to (Δr ₁ −Δr ₂ ) and the positional deviation z in the focusing direction is changed to 0 μm, 10 μm, and 20 μm, the approximation shown by the solid line is not used When the approximate expression shown by the dotted line is used, they almost overlap, and it can be understood that the approximate expression of equation (14) can be calculated with sufficient accuracy.

As described above, the outputs of the light position detection elements PSDa and PSDb mounted on the medium attitude detection unit 34 are output to the controller 10 as attitude detection signals, and the controller 10 focuses on the basis of equations (13) and (14). And the inclination angle αr can be detected.

The distance Δr between the positions Ra and Rb at which the light beams LBa and LBb are reflected by the hologram medium 2 is made as small as possible, and the positions substantially the same as the positions on which the signal light and the reference light are incident To be As a result, it is possible to detect the amount z of positional deviation in the focus direction of the position where the signal light and the reference light are incident on the hologram medium 2 and the inclination angle αr.

FIG. 8 (a) shows an example of the flowchart of the process from the insertion of the hologram medium 2 into the hologram recording and reproducing apparatus 1 to the ejection, FIG. 8 (b) shows an example of the flowchart of the recording process, and FIG. Shows an example of a flowchart of the reproduction process.

In FIG. 8A, when the hologram medium 2 is loaded in the hologram recording / reproducing apparatus 1, the controller 10 determines whether the loaded medium is recorded or not (S801).
Next, the position of the PSD, which is a reference for medium attitude detection, is acquired (S802). By this processing, position information corresponding to r ₁ and r ₂ of equation (2) is acquired. Next, in learning adjustment processing (S 803), for example, the reproduction light incident on the light detector 325 is emitted from the laser light source 301 so as to satisfy a predetermined light amount at the time of learning or reproduction of recording conditions matched to the sensitivity of the hologram medium. Adjust the power of the reference light. In S804, it is determined whether a command for requesting recording or reproduction from the external control device 40 to the hologram recording / reproduction device 1 is input through the input / output control unit 11, and branch processing is performed. If a command to request recording or reproduction is input (Yes), it is determined in S805 whether a command to request recording is input and branch processing is performed. If a command requesting recording is input (Yes), the recording processing is performed in S806, and the process returns to processing S804 to determine again whether a command requesting recording or reproduction is input. If a command requesting reproduction is input in branch processing S805 (No), the reproduction processing is performed in S807, and the process returns to processing S804 where it is determined whether a command requesting recording or reproduction is input again. If a command to request recording or reproduction is not input in S804 (No), it is determined in S808 whether a command to request ejection of the hologram medium 2 is input from the external control device 40, and the branch processing is performed. Do. If the discharge request command has not been input (No), the process returns to step S804 to determine whether a command to request recording or reproduction has been input. If the discharge request command has been input (Yes), processing for discharging the hologram medium 2 from the hologram recording / reproducing apparatus 1 is performed in S809, and the processing is ended.

In the flowchart of the recording process shown in FIG. 8B, first, data to be recorded is received from the external control device 40 via the input / output control unit 11 (S811). Next, in the seek process (S 812), the radial direction transfer drive unit 15 is controlled via the access control circuit 12, and the medium rotation drive unit 4 is controlled via the medium rotation control unit 6. The hologram medium 2 is moved. Thereafter, a predetermined area is precured using the light beam emitted from the curing optical system 33 (S813), and data is recorded using the reference light and the signal light emitted from the recording / reproducing optical system 31 (S814). After the data is recorded, post curing is performed using the light beam emitted from the curing optical system 33 (S815), and the processing is ended.

In the flowchart of the reproduction process shown in FIG. 8C, in the seek process (S 821), the radial direction transfer drive unit 15 is controlled via the access control circuit 12, and the medium rotation drive unit via the medium rotation control unit 6. The hologram medium 2 is moved to the position where the hologram to be reproduced is recorded by controlling 4. Next, the reference light is emitted from the recording / reproducing optical system 31, the information recorded in the hologram medium 2 is read (S822), and reproduction data is transmitted to the external control device 40 via the input / output control unit 11 (S823) End the process.

Next, an example of seek processing in S812 and S821 will be described using the flowchart of FIG. In the seek process, first, the radial direction moving amount Rm and the rotational direction moving amount θm to the position of the hologram to be recorded or reproduced are calculated (S901). In branch processing S902, if the radial movement amount Rm is not 0 (Yes), the radial direction transfer drive unit 15 is controlled via the access control unit 12 to move the hologram medium 2 in the radial direction by Rm (S903) ). If the radial movement amount Rm is 0 (No) in branch processing S902 and after the radial movement processing in S903, the medium rotation control unit 6 is performed if the rotational direction movement amount θm is not 0 in branch processing S904 (Yes) The medium rotation drive unit 4 is controlled via the to move the hologram medium 2 in the rotation direction by .theta.m (S905). If the rotation direction movement amount θm is 0 (No) in the branch processing of S904 and after the rotation direction movement processing of S905, it is determined whether or not the reference PSD position acquisition processing (S802) is performed in the branch processing S906. If not (No), the seek process is ended. When the reference PSD position acquisition processing is performed in the branch processing S906 (Yes), the medium tilt angle / focus position correction processing is performed (S907). Next, in branch processing S908, it is determined whether it is seek processing in the reproduction processing, and in the case of seek processing in the reproduction processing (Yes), address information is acquired from the recorded hologram (S909) and the seek processing is ended. Do. In the case of the seek processing in the recording processing in branch processing S908 (No), the seek processing is ended.

Next, an example of a flowchart of the reference PSD position acquisition processing S802 in FIG. 8A is shown in FIG.
In FIG. 10, first, seek is performed to a predetermined reference position (S1001). The reference position may be, for example, the position of a page on which a first hologram is recorded on a new hologram medium, or a position on which medium management information such as the position on the medium on which data is recorded is recorded. The point is that the inner circumferential radial position is desirable, as long as it is a predetermined position, and the influence of the medium tilt due to the warp of the disk-like hologram medium 2 or the shift of the height position in the focusing direction is small. Next, the radial tilt drive unit 13 and the focus drive unit 14 are controlled via the radial tilt control unit 16 and the focus control unit 17 so that the height of the medium tilt and the focus direction of the hologram medium 2 in the radial direction is predetermined. Set to the initial position. In S1003, branching processing is performed based on the processing of S801 at the time of medium insertion shown in FIG. 8a, and when the hologram medium 2 is not recorded (Yes), the output of the medium attitude detection unit 34 in S1005 is used as reference PSD position information. The values r ₁ and r ₂ in equation (2) are acquired, stored in the memory 20, and the process is terminated. If the hologram medium 2 has been recorded in branch processing S1003 (No), for example, the radial direction tilt drive unit 13 and the focus drive unit 14 so that the light amount received by the light detector 325 is maximized to optimize the reproduction signal. Are controlled to adjust the height of the focus direction of the hologram medium 2 and the medium tilt in the radial direction (S1004). After adjusting the medium inclination in the focusing direction of the height and radial acquires r ₁ and r ₂ of formula (2) as a reference PSD position information from the output of the media orientation detection unit 34 in S1005, and stored in the memory 20 End the process. By the above processing, when the hologram medium 2 is not recorded, the reference PSD position information r ₁ and r ₂ are obtained from the output of the medium attitude detection unit 34 at the predetermined initial position, and when the recording is completed, the reproduction signal is Reference PSD position information r ₁ and r ₂ are obtained from the output of the medium attitude detection unit 34 in the optimum state, and stored in the memory 20.

The medium tilt angle / focus position correction process S 907 in the seek process of FIG. 9 will be described with reference to FIG. In FIG. 11, first, PSD position information r ₁ ′ and r ₂ ′ are acquired from the output of the medium attitude detection unit 34 (S 1101). Next, differences Δr ₁ and Δr ₂ with the reference PSD position information r ₁ and r ₂ stored in the memory 20 in the reference PSD position acquisition processing are obtained (S 1102). In S1103, the medium tilt angle αr and the focus height z are detected based on the equations (13) and (14). The controller 10 controls the radial tilt drive unit 13 and the focus drive unit 14 in the direction that cancels out the detected medium tilt angle αr and the focus height z via the radial direction tilt control unit 16 and the focus control unit 17, and the hologram medium A radial inclination angle of 2 and a focus height are set (S1104), and the process is ended.

In the above embodiment, as shown in FIG. 12A, by configuring the medium posture detection unit 34 by a pair of 34a and 34b arranged at different positions in the radial direction, the angle of the medium inclination in the radial direction and the focusing direction It is possible to detect the height of

Similarly, as shown in FIG. 12B, the medium orientation detection unit 34 is configured by a pair of 34c and 34d arranged at different positions in the direction (tangent direction) orthogonal to the radial direction, whereby the medium tilts in the tangential direction. It is possible to detect the angle of and the height of the focus direction.

FIG. 13 shows a block diagram of a configuration example of a hologram recording and reproducing apparatus corresponding to FIG. 12 (b). The same components as those in the block diagram of FIG. In FIG. 13, media attitude detection units 34a and 34b disposed at different radial positions in FIG. 1 have media attitude detection units 34 disposed at tangential different positions as shown in FIG. 12B. , 34d (for the sake of description, they are the same arrangement as in FIG. 1). In addition, a tangential direction tilt drive unit 18 and a tangential direction tilt control unit 19 are provided to the radial direction tilt drive unit 13 and the radial direction tilt control unit 16 in FIG. 1.
A posture detection signal for detecting the tilt angle of the hologram medium 2 in the tangential direction and the position in the focus direction is output to the controller 10 from the medium posture detection unit configured by a pair of 34c and 34d arranged at different positions in the tangential direction. Do. The controller 10 detects the tilt angle and focus position in the tangential direction of the hologram medium 2 based on the attitude detection signal, and the tangential tilt control command signal is sent to the tangential tilt control unit 19 and the focus control command signal to the focus control unit 17. Output. The tangential tilt control unit 19 can change the tilt angle in the tangential direction of the hologram medium 2 by controlling the tangential tilt drive unit 18 based on the tangential tilt control command signal. The focus control unit 17 can change the position of the hologram medium 2 in the focus direction by controlling the focus drive unit 14 based on the focus control command signal.

An example of the flowchart of reference | standard PSD position acquisition process S802 corresponding to the hologram recording and reproducing apparatus of FIG. 13 is shown in FIG. In FIG. 14, first, seek is performed to a predetermined reference position (S1401). The reference position is the same position as the reference position seek process (S1001) in FIG. Next, the tangential direction tilt drive unit 18 and the focus drive unit 14 are controlled via the tangential direction tilt control unit 19 and the focus control unit 17, and the height of the medium inclination angle and the focus direction in the tangential direction of the hologram medium 2 is specified. Set to the initial position of. In S1403, the branching process is performed based on the process of S801 at the time of medium insertion shown in FIG. 8A, and when the hologram medium 2 is not recorded (Yes), the output of the medium attitude detection unit 34 in S1405 is used as reference PSD position information. The times t ₁ and t ₂ of equation (15) are acquired, stored in the memory 20, and the process is terminated.
(Equation 15)
t ₁ = t ₂ = 2 · d / tan (θt)
Here, d represents the distance in the focusing direction from the medium attitude detection units 34c and 34d to the hologram medium 2, and θt represents the angle emitted from the laser light source of the medium attitude detection units 34c and 34d to the hologram medium 2.
When the hologram medium 2 has been recorded in the branching process S1403 (No), for example, the tangential direction tilt drive unit 18 and the focus drive unit 14 so that the amount of light received by the light detector 325 is maximized to optimize the reproduction signal. Are controlled, and the inclination angle in the tangential direction of the hologram medium 2 and the height in the focusing direction are adjusted (S1404). After adjusting the inclination angle and the focusing direction height of the tangential obtains t ₁ and t ₂ of the formula (15) as a reference PSD position information from the output of the media orientation detection unit 34 in S1405, and stored in the memory 20 End the process. By the above processing, when the hologram medium 2 is not recorded, the reference PSD position information t ₁ and t ₂ are acquired from the output of the medium attitude detection unit 34 at the predetermined initial position, and when the recording is completed, the reproduction signal is Reference PSD position information t ₁ and t ₂ are obtained from the output of the medium attitude detection unit 34 in the optimum state, and stored in the memory 20.

The medium tilt angle / focus position correction process S 907 in the seek process corresponding to the hologram recording / reproducing apparatus in FIG. 13 will be described with reference to FIG. In FIG. 15, first, PSD position information t ₁ ′ and t ₂ ′ are acquired from the output of the medium attitude detection unit 34 (S 1501).
Next, differences Δt ₁ and Δt ₂ from the reference PSD position information t ₁ and t ₂ stored in the memory 20 in the reference PSD position acquisition processing are obtained (S 1502). In S1503, the medium inclination angle αt and the focus height z are detected based on the equations (16) and (17).
(Equation 16)
Δt ₁ + Δt ₂ 4 4z / tan (θt)
= P · z
(17)
Δt ₁ −Δt ₂ 44αt [d + {d + tan (θt) · Δt / 2} / tan ² (θt)]
= N · α t
The proportional coefficients P and N in the equations (16) and (17) are, for example, the angle θt emitted from the laser light source of the medium attitude detection units 34c and 34d to the hologram medium 2, and from the medium attitude detection units 34c and 34d to the hologram medium 2 The distance d in the focus direction and the deviation Δt of the position at which the light beam emitted from the laser light sources of the medium attitude detectors 34c and 34d is reflected by the hologram medium 2 are known at the time of design and can be obtained in advance.

The controller 10 controls the tangential tilt drive unit 18 and the focus drive unit 14 in the direction that cancels out the detected medium tilt angle αt and the focus height z via the tangential direction tilt control unit 19 and the focus control unit 17, and the hologram medium The inclination angle and focus height in the tangential direction of 2 are set (S1504), and the process is ended.

In the above embodiment, as shown in FIG. 12 (b), the inclination angle of the hologram medium 2 in the tangential direction and the inclination angle of the hologram medium 2 can be obtained by configuring the medium posture detection unit 34 as a pair of 34c and 34d arranged at different positions in the tangential direction. It is possible to detect the height in the focus direction.

In FIG. 12C, the medium attitude detection unit 34 is configured by a pair of 34e and 34f arranged obliquely with respect to the radial direction, so that the inclination angle of the hologram medium 2 in the radial direction, the inclination angle in the tangential direction, and the focus direction To detect the height of the In FIGS. 12A and 12B, by using an element capable of detecting the position in at least one dimension direction as the light position detection element of the medium attitude detection unit 34, the height in the focus direction and the radial or tangential direction can be obtained. The inclination of one direction is detected. On the other hand, in FIG. 12C, an element capable of detecting the position in the two-dimensional direction is used as the light position detection element of the medium attitude detection unit 34 to detect the height in the focus direction and the inclination in the radial and tangential directions. It is like that.

FIG. 16 shows a block diagram of a configuration example of a hologram recording and reproducing apparatus corresponding to FIG. The same components as those in the block diagram of FIG. Referring to FIG. 16, the medium attitude detection unit 34 is disposed obliquely in the radial direction as shown in FIG. 12C with respect to the medium attitude detection units 34a and 34b arranged at different positions in the radial direction in FIG. It is configured to be a pair of 34f (for convenience of description, it is a view of the same arrangement as FIG. 1).
Further, in addition to the radial direction tilt drive unit 13 and the radial direction tilt control unit 16 in FIG. 1, a tangential direction tilt drive unit 18 and a tangential direction tilt control unit 19 are provided.

The attitude detection signal for detecting the inclination angle of the hologram medium 2 in the radial direction, the inclination angle in the tangential direction, and the position in the focusing direction from the medium attitude detection unit configured by a pair of 34e and 34f arranged diagonally in the radial direction It outputs to the controller 10. The controller 10 detects the inclination angle in the radial direction, the inclination angle in the tangential direction, and the focus position of the hologram medium 2 based on the attitude detection signal, and the radial direction tilt control unit 16 controls the radial direction tilt control command signal. A tangential direction tilt control command signal is output to the unit 19 and a focus control command signal is output to the focus control unit 17. The radial tilt control unit 16 can change the tilt angle of the hologram medium 2 in the radial direction by controlling the radial direction tilt drive unit 13 based on the radial direction tilt control command signal. The tangential tilt control unit 19 can change the tilt angle in the tangential direction of the hologram medium 2 by controlling the tangential tilt drive unit 18 based on the tangential tilt control command signal. The focus control unit 17 can change the position of the hologram medium 2 in the focus direction by controlling the focus drive unit 14 based on the focus control command signal.

An example of the flowchart of reference | standard PSD position acquisition process S802 corresponding to the hologram recording and reproducing apparatus of FIG. 16 is shown in FIG. In FIG. 17, first, seek is performed to a predetermined reference position (S1701). The reference position is the same position as the reference position seek process (S1001) in FIG. Next, the radial direction tilt drive unit 13, the tangential direction tilt drive unit 18 and the focus drive unit 14 are controlled via the radial direction tilt control unit 16, the tangential direction tilt control unit 19 and the focus control unit 17. The media tilt angle in the radial direction, the media tilt angle in the tangential direction, and the height in the focus direction are set to predetermined initial positions. In S1703, branching processing is performed based on the processing of S801 at the time of medium insertion shown in FIG. 8A, and when the hologram medium 2 is not recorded (Yes), the output of the medium attitude detection unit 34 in S1705 is used as reference PSD position information. The r ₁ and r ₂ of the equation ( ₂ ) and the t ₁ and t ₂ of the equation (15) are acquired and stored in the memory 20 to complete the process. If the hologram medium 2 has been recorded in branch processing S1703 (No), for example, the radial direction tilt drive unit 13 and the tangential direction tilt drive so that the light amount received by the light detector 325 is maximized to optimize the reproduction signal. The unit 18 controls the focus drive unit 14 to adjust the inclination angle of the hologram medium 2 in the radial direction, the inclination angle in the tangential direction, and the height in the focusing direction (S1704). After adjusting the inclination angle in the radial direction, the inclination angle in the tangential direction, and the height in the focus direction, the output of the medium attitude detection unit 34 in S1705 uses r ₁ , r ₂ and (2) 15) t ₁ and t ₂ are acquired, stored in the memory 20, and the process ends. By the above processing, when the hologram medium 2 is not recorded, the reference PSD position information r ₁ , r ₂ , t ₁ , t ₂ is obtained from the output of the medium attitude detection unit 34 at a predetermined initial position, and recorded. In this case, the reference PSD position information r ₁ , r ₂ , t ₁ and t ₂ are acquired from the output of the medium attitude detection unit 34 in the state where the reproduction signal is optimum, and stored in the memory 20.

The medium tilt angle / focus position correction process S 907 in the seek process corresponding to the hologram recording / reproducing apparatus in FIG. 16 will be described with reference to FIG. In FIG. 18, first, PSD position information r ₁ ′, r ₂ ′, t ₁ ′ and t ₂ ′ are obtained from the output of the medium attitude detection unit 34 (S 1801). Next, differences Δr ₁ , Δr ₂ , Δt ₁ , Δt ₂ with the reference PSD position information r ₁ , r ₂ , t ₁ , t ₂ stored in the memory 20 in the reference PSD position acquisition processing are obtained (S 1802). In S1803, the radial inclination angle αr, the tangential inclination angle αt, and the focus height z are detected based on the equations (13), (14) and (17). In the controller 10, the radial tilt is performed in the direction to cancel the detected radial tilt angle αr, the tangential tilt angle αt, and the focus height z via the radial tilt control unit 16, the tangential direction tilt control unit 19, and the focus control unit 17. The drive unit 13, the tangential direction tilt drive unit 18, and the focus drive unit 14 are controlled to set the inclination angle in the radial direction of the hologram medium 2, the inclination angle in the tangential direction, and the focus height (S1804), and the processing is ended.

In the embodiment of FIG. 16, as shown in FIG. 12C, the medium posture detection unit 34 is configured by a pair of 34e and 34f arranged at diagonally different positions in the radial direction. It is possible to detect the inclination angle, the tangential inclination angle and the height in the focus direction. As a method of detecting the inclination angle in the radial direction, the inclination angle in the tangential direction, and the height in the focus direction of the hologram medium 2, an optical position detection element capable of detecting the position in one dimension is used. As shown, the medium attitude detection unit 34 may be configured by two pairs whose positions are different in the radial direction and the tangential direction.

In the above embodiment, the medium rotation drive unit 4 and the rotation angle detection unit 5 are mounted on the radial direction tilt drive unit 13 and / or the tangential direction tilt drive unit 19 and the focus drive unit 14 to make the hologram medium 2 relative to the pickup 3 The radial inclination angle and / or the tangential inclination angle, and the focus height can be changed. On the other hand, by mounting the pickup 3 on the radial direction tilt drive unit 13 and / or the tangential direction tilt drive unit 19 and the focus drive unit 14 as shown in FIG. 17, the relative radius of the pickup 3 to the hologram medium 2 The directional tilt angle and / or the tangential tilt angle, and the focus height may be changed.

In FIG. 19, the same parts as those in the block diagram of FIG. Attitude detection for detecting the relative inclination angle in the radial direction and the position in the focusing direction of the pickup 3 with respect to the hologram medium 2 from the medium attitude detection unit constituted by a pair of 34a and 34b arranged at different positions in the radial direction A signal is output to the controller 10. The controller 10 detects the tilt angle and focus position of the pickup 3 relative to the hologram medium 2 in the radial direction based on the attitude detection signal, and the radial direction tilt control unit 16 receives the radial direction tilt control command signal. Outputs a focus control command signal. The radial tilt control unit 16 can change the tilt angle of the pickup 3 in the radial direction by controlling the radial direction tilt drive unit 13 based on the radial direction tilt control command signal. Further, the focus control unit 17 can change the position of the pickup 3 in the focusing direction by controlling the focus driving unit 14 based on the focus control command signal.

The reference PSD position acquisition processing and seek processing corresponding to the hologram recording / reproducing apparatus of FIG. 19 controls the radial tilt drive unit 13 and the focus drive unit 14 by the same processing as the flowchart of FIG. 10 and the flowchart of FIG. This can be achieved by setting the radial inclination angle relative to the hologram medium 2 and the height in the focusing direction.

As described in the above embodiments, according to the present invention, at least a pair of media posture detection units including a laser light source and a light position detection element are provided at positions separated in the radial direction or tangential direction, thereby tilting the hologram medium. It is possible to correctly detect the position in the focus direction together with the angle, and to correct the tilt angle of the hologram medium and the position in the focus direction.

Although the radial direction tilt drive unit 13 and / or the tangential direction tilt drive unit 18 are disposed on the focus drive unit 14 in the above embodiments, the present invention is not limited to this. And the position in the focusing direction can be changed while inclining in the radial direction and / or the tangential direction.

In the above description, the hologram medium is a disk, but the invention is not limited thereto. A square plate-like medium may be used, and the inclination of the medium posture detection unit including the laser light source and the light position detection device is corrected. By providing at least one pair at positions separated in the direction, it is possible to correctly detect the position of the focus direction together with the tilt angle of the hologram medium and correct the tilt angle of the hologram medium and the position of the focus direction.

Furthermore, although the hologram recording and reproducing apparatus capable of recording and reproducing the hologram has been described in the above embodiment, the present invention is not limited thereto, but the hologram reproducing apparatus having only the function of reproducing the hologram medium recorded in advance The present invention can be similarly applied to a hologram recording apparatus that performs only recording on the hologram medium of

The present invention is not limited to the embodiments described above, but includes various modifications. For example, the embodiments described above are described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the configurations described. Also, 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. In addition, with respect to a part of the configuration of each embodiment, it is possible to add, delete, and replace other configurations.

Further, each of the configurations, functions, processing units, processing means, etc. described above may be realized by hardware, for example, by designing part or all of them with an integrated circuit. Further, each configuration, function, etc. described above may be realized by software by the processor interpreting and executing a program that realizes each function. Information such as programs, tables, and files for realizing each function can be placed in a memory, a hard disk, a recording device such as a solid state drive (SSD), or a recording medium such as an IC card, an SD card, or a DVD.

Further, control lines and information lines indicate what is considered to be necessary for the description, and not all control lines and information lines in the product are necessarily shown. In practice, almost all configurations may be considered to be mutually connected.

1: Hologram recording and reproducing apparatus 2: Hologram medium 3: Pickup 30: Light source drive circuit
31: recording / reproducing optical system, 32: reference light optical system for reproduction, 33: curing optical system, 34: medium attitude detection unit, 4: medium rotation driving unit, 5: Rotation angle detection unit, 6: medium rotation control unit, 10: controller, 11: input / output control unit, 12: access control unit,
13: radial tilt drive, 14: focus drive, 15: radial transfer drive,
16: radial direction tilt control unit, 17: focus control unit, 18: tangential direction tilt drive unit,
19: Tangent direction tilt control unit 20: Memory 40: External control device

Claims (6)

1. A hologram recording and / or reproducing apparatus that irradiates signal light and reference light to a hologram recording medium to record or reproduce information.
   A medium posture detection unit configured of at least a pair of portions including a light source for emitting a light beam to the hologram recording medium and a light position detection unit for receiving the light beam reflected from the hologram recording medium;
   A hologram recording and / or reproducing apparatus characterized in that the medium attitude detection unit is arranged at different positions in a radial direction and / or a tangential direction orthogonal to the radial direction.
2. The hologram recording and / or reproducing apparatus according to claim 1,
   A rotation drive unit that rotates the hologram recording medium;
   The tilt drive unit that changes the tilt angle of the rotation drive unit in the radial direction and / or the tangential direction orthogonal to the radial direction; and a focus drive unit that moves the rotation drive unit in the focus direction.
   A controller unit is provided which detects a tilt angle in the tangential direction orthogonal to the radial direction and / or the radial direction of the hologram medium based on the output of the medium attitude detection unit and a position in the focus direction and outputs a signal for correction. A hologram recording and / or reproducing apparatus characterized in that.
3. The hologram recording and / or reproducing apparatus according to claim 1,
   First and second position detection results r ₁ and r ₂ obtained from the output of the light position detection unit of the medium attitude detection unit configured by the pair of portions at the reference position, and the position at which the hologram is recorded or reproduced The difference between the third and fourth position detection results r ₁ ′ and r ₂ ′ obtained from the output of the light position detection unit is Δr ₁ = r ₁ ′ −r ₁ and Δr ₂ = r ₂ ′ −r ₂ The inclination angle in the radial direction and / or the tangential direction orthogonal to the radial direction of the hologram medium is detected from Δr ₁ −Δr ₂ , and the position in the focus direction of the hologram recording medium is detected from Δr ₁ + Δr ₂ Hologram recording and / or reproducing apparatus characterized by
4. The hologram recording and / or reproducing apparatus according to claim 1,
   A pickup for irradiating the hologram recording medium with the signal light and the reference light;
   And a focus drive unit for moving the pickup in a focusing direction. The tilt drive unit changes the tilt angle of the pickup in the radial direction and / or the tangential direction orthogonal to the radial direction.
   A controller unit is provided which detects a tilt angle in the tangential direction orthogonal to the radial direction and / or the radial direction of the pickup based on the output of the medium attitude detection unit and a position in the focus direction and outputs a signal for correction. Hologram recording and / or reproducing apparatus characterized in that
5. A hologram recording and / or reproducing apparatus that irradiates signal light and reference light to a hologram recording medium to record or reproduce information.
   Medium posture detection comprising a pair of portions including a light source for emitting a light beam to a hologram recording medium and a light position detection unit for receiving a light beam reflected from the hologram recording medium and detecting a two-dimensional position Equipped with
   A hologram recording and / or reproducing apparatus characterized in that the medium posture detection unit is arranged at different positions in a direction oblique to the radial direction.
6. The hologram recording and reproducing apparatus according to claim 5, wherein
   A rotation drive unit that rotates the hologram recording medium;
   A tilt drive unit that changes the inclination angle of the rotation drive unit in a radial direction and a tangential direction orthogonal to the radial direction; a focus drive unit that moves the rotation drive unit in a focusing direction;
   A controller unit is provided which detects a tilt angle in a tangential direction orthogonal to the radial direction and the radial direction of the hologram recording medium based on the medium attitude detection unit and a position in a focus direction and outputs a signal for correction. Hologram recording and / or reproducing apparatus characterized by the above.

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