JP6915840B2 - Hologram recording / playback method and hologram recording / playback device - Google Patents

Description

The present invention relates to a hologram recording / reproducing method and a hologram recording / reproducing device. More specifically, the present invention relates to a hologram recording / reproducing method and a hologram recording / reproducing apparatus that are suitably used for constructing a large-capacity optical memory by multiple-recording a two-dimensional digital bit pattern as a hologram on a recording medium.

Conventionally, a hologram recording / reproducing device for two-dimensionally recording / reproducing digital information using a hologram has been proposed. In a hologram recording / reproducing device, a signal light carrying digital information (data information) modulated by a spatial light modulator composed of a plurality of pixels is made to interfere with the signal light and a coherent reference light in a recording medium. The interference fringes obtained by this are recorded as a hologram. Further, when reproducing a hologram recorded on a recording medium, diffracted light is generated by irradiating the hologram with reference light used for recording, and the hologram is recorded as a hologram on an image sensor such as a CCD. Form an image of digital information.

As one of such hologram recording / reproducing methods, for example, a spherical reference light shift multiple recording method using a spherical wave (hereinafter, also referred to as “spherical reference light”) as a reference light is known.
However, in the spherical reference optical shift multiple recording method which has been conventionally studied, the shift selectivity in the uniaxial direction along the plane formed by the optical axis of the signal light and the optical axis of the spherical reference light is excellent. However, the shift selectivity is weak in the direction perpendicular to the axial direction, and multiple recording in two dimensions is difficult. Therefore, it is difficult to increase the density of the recorded information only by the spherical reference optical shift multiple recording method.
In view of such circumstances, the inventors of the present application have proposed a method of performing multiple recording by crossing shift multiple hologram sequences in a recording medium plane, that is, in a two-dimensional plane (see, for example, Patent Document 1). .. This method is a method of overwriting shift multiple holograms in a two-dimensional direction.

Therefore, when recording and reproducing a hologram, it is necessary to obtain position information and address information that specify a location on the recording medium. For example, Patent Document 2 describes a technique in which a servo pit for position control is provided on a recording medium and a position is detected by reflected light from the servo pit.

Japanese Unexamined Patent Publication No. 2016-219087 Japanese Unexamined Patent Publication No. 2003-178484

However, the invention described in Patent Document 2 only describes a method for positioning the recording / reproducing light when the hologram is concentrically shifted and multiplexed with respect to the disc-shaped recording medium. In fact, there is no known method for accurately positioning the recording / reproducing light with respect to the recording medium when performing shift multiple recording of a hologram.

The present invention has been made based on the above circumstances, and can accurately position the irradiation positions of the signal light and the reference light, and can perform multiple recording of holograms with high reliability. It is an object of the present invention to provide a hologram recording / reproducing method and a hologram recording / reproducing apparatus capable of performing the same.

In the hologram recording / reproducing method of the present invention, the hologram obtained by interfering the signal light generated by separating the recording / reproducing light with the spherical reference light is multiple-recorded on the recording medium by the shift multiplexing method, and the hologram is recorded. In a hologram recording / reproducing method in which data information recorded on a hologram is reproduced by irradiating the recording medium with spherical reference light.
As a recording medium, a plurality of positioning guide grooves are formed concentrically, and a plurality of markers whose positions can be detected by light are formed at positions arranged in the circumferential direction at a predetermined pitch in each positioning guide groove. Disc-shaped ones are used
From an optical head equipped with a recording / reproducing light irradiation optical system and a light irradiation optical system for detecting servo error signals, light for detecting servo error signals having a wavelength that is insensitive to the recording layer in the recording medium is irradiated toward the positioning guide groove. As a result, the diffracted light emitted from the positioning guide groove is detected by the split type photodetector, and the irradiation of the servo error signal detection light is based on the servo error signal obtained from the differential output of the split type photodetector. The signal light is controlled by controlling the position to follow the positioning guide groove as the recording medium rotates, and by detecting the position of the marker located in the positioning guide groove by the servo error signal detection light. And the position of the irradiation position of the spherical reference light with respect to the position of the marker is performed.
Shift multiple recording is performed in one direction that intersects the tangential direction of the positioning guide groove at the position of the marker.
In the split photodetector, one of the boundary lines that divides the light receiving surface into a plurality of detection regions extends in an angular direction parallel to the tangential direction of the positioning guide groove at the position of the marker corresponding to the hologram recording / playback start position. , The feature is that the posture is controlled.

Furthermore, in the hologram recording / reproduction method of the present invention, after recording the first shift multiple hologram sequence in which a plurality of holograms are partially overlapped with each other and arranged in one direction, the recording medium is placed on a plane along the surface thereof. A new shift is performed in a state where the optical head is positioned with respect to the recording medium by rotating the inside and moving one of the recording medium and the optical head in parallel by a movement amount corresponding to the rotation angle of the recording medium. By performing multiple recording, it is preferable that the second shift multiple hologram sequence is multiple-recorded in a state in which a part of the recording area overlaps with the recording area of the first shift multiple hologram sequence.

Furthermore, in the hologram recording / reproducing method of the present invention, when recording the second shift multiplex hologram sequence, after positioning the optical head with respect to the recording medium, the irradiation position of the servo error signal detection light is set to the first position. It is preferable that the position correction is performed so as to match the position of the marker corresponding to the recording area in which the shift multiple hologram sequence is recorded.

The hologram recording / reproducing device of the present invention multiplex-records a hologram formed by interfering a signal light carrying data information with a spherical reference light by a shift multiplexing method, and simultaneously records the hologram recorded on a recording medium with a spherical reference light. In a hologram recording / reproducing device that reproduces data information recorded on the hologram by irradiating with
As a recording medium, a disk shape in which a plurality of positioning guide grooves are formed concentrically and markers whose positions can be detected by light are arranged in the circumferential direction at a predetermined pitch in each positioning guide groove. Is used,
Recording / playback light irradiation that irradiates the recording medium with signal light and spherical reference light generated by separating the recording / playback light from the recording / playback light source. An optical head having a light irradiation optical system for detecting a servo error signal that irradiates the recording medium with light, and a split type light detector that detects the diffracted light emitted from the positioning guide groove and the marker by the light for detecting the servo error signal. A control mechanism that positions the optical head with respect to the recording medium based on the servo error signal and marker detection signal obtained from the differential output of the type optical detector, and optics that move the optical head in one direction along the surface of the recording medium. A head moving mechanism, a recording medium driving mechanism that rotates and parallel moves the recording medium in a plane including the moving direction of the optical head, and a boundary line that divides the light receiving surface of the split type optical detector into a plurality of detection regions. One is provided with an attitude control means for controlling the attitude of the split-type optical detector so as to extend in an angular direction parallel to the tangential direction of the positioning guide groove at the position of the marker at the hologram recording / reproduction start position.

According to the present invention, the irradiation positions of the signal light and the spherical reference light are positioned with respect to the recording medium based on the distribution of the light receiving intensity of the diffracted light emitted from the positioning guide groove and the marker in the recording medium. It is possible to accurately position the irradiation positions of light and reference light, and multiple recording of holograms can be performed with high reliability.
In particular, when cross-shift multiplex recording is performed on the same recording area on the recording medium, not only the recording medium is rotated, but also the optical head or the recording medium is translated in a plane along the surface of the recording medium. The present invention is extremely useful when positioning the irradiation positions of the signal light and the spherical reference light with respect to the recording medium.

Further, the above effect can be obtained more reliably by performing position correction for correcting the positional deviation of the irradiation position of the signal light and the spherical reference light due to the eccentric rotation of the recording medium with respect to the marker position.

It is a top view which shows the structure in an example of the recording medium used in this invention. FIG. 5 is a cross-sectional view schematically showing a cross section of the recording medium shown in FIG. 1 along the circumferential direction. It is explanatory drawing which shows an example of the shift multiplex recording in the hologram recording reproduction method of this invention. It is explanatory drawing which shows the outline of the spherical reference optical shift multiplex recording. It is explanatory drawing which shows an example of the method of multiplex recording by crossing a shift multiplex hologram sequence in the hologram recording reproduction method of this invention. It is explanatory drawing which shows the outline of the attitude control of a split type photodetector. It is explanatory drawing which shows the outline of the position correction with respect to the marker position of the irradiation position of the signal light and the reference light due to the eccentric rotation of a recording medium. It is explanatory drawing which shows the outline of the structure of the recording / reproduction light irradiation optical system in the hologram recording / reproduction apparatus of this invention. It is explanatory drawing which shows the outline of the structure of the light irradiation optical system for servo error signal detection in the hologram recording / reproduction apparatus of this invention. It is explanatory drawing which shows the outline of the structure of the optical system for reading the block information of the recording medium in the hologram recording / reproduction apparatus of this invention. It is explanatory drawing which shows the outline of another structural example of the recording-reproduction light irradiation optical system in the hologram recording-reproduction apparatus of this invention. It is explanatory drawing which shows the outline of the other structural example of the recording-reproduction light irradiation optical system in the hologram recording-reproduction apparatus of this invention.

Hereinafter, embodiments of the present invention will be described in detail.

The hologram recording / reproduction method of the present invention performs multiple recording of holograms on a disk-shaped recording medium, for example, by spherical reference optical shift multiple recording in the uniaxial direction, and specifically, in the uniaxial direction. By cross-recording the shift multiple hologram train formed by the spherical reference optical shift multiple recording in the plane of the recording medium, that is, in the two-dimensional plane, the recording information in the recording medium is densified. .. In the following, first, the recording medium used in the present invention will be described.

FIG. 1 is a plan view showing a configuration in an example of a recording medium used in the present invention. FIG. 2 is a cross-sectional view schematically showing a cross section of the recording medium shown in FIG. 1 along the circumferential direction.
The recording medium 10 of this example is a transmissive type, and is a support substrate 11 made of a light-transmitting material such as glass, a hologram recording layer 15 laminated on one surface of the support substrate 11, and a hologram recording layer. It is composed of a light-transmitting substrate 16 such as glass laminated on one surface of 15. In the present invention, the recording medium 10 may be a reflective type. When the recording medium 10 is configured as a reflective type, a reflective layer that reflects diffracted light from, for example, a hologram is provided on the other surface of the support substrate 11. Further, the reflective layer may be provided between the hologram recording layer 15 and the support substrate 11. The reflective layer can be formed of, for example, a thin-film deposition film.

The hologram recording layer 15 is made of a photoreactive monomer that is sensitive to, for example, a blue laser light used as recording / reproducing light.
The thickness of the hologram recording layer 15 is, for example, 0.3 to 2.0 mm, preferably 0.5 to 1.0 mm, from the viewpoint of recording / reproducing ability.

A plurality of positioning guide grooves 12 are concentrically formed on the support substrate 11 of the recording medium 10, and markers 13 whose positions can be detected by light in each of the positioning guide grooves 12 are rotated at a predetermined pitch. It is formed in a position arranged in a direction.

Each positioning guide groove 12 may be continuously formed or intermittently formed.
The width dimension of each positioning guide groove 12 is, for example, about 0.5 μm.

The marker 13 is composed of, for example, a diffractive optical element in which phase information of a two-dimensional data pattern related to labeling information including position information on the recording medium 10 is recorded.
The diffractive optical element can be composed of, for example, a phase hologram having a concavo-convex pattern in which the depth of the concavo-convexity differs depending on the amount of phase. Such a diffractive optical element can be formed by, for example, a nanoimprint method.
The information recorded on the marker 13 is basically position information for access, for example, playback conditions such as the position information (track number) and format information of the recording track, recording conditions, and optimum filter parameters during playback. Can be mentioned.
Further, the marker 13 does not need to be composed of a diffractive optical element using a phase hologram, and even if it has the same configuration as a marker on a normal optical disk, which can be detected by the servo error signal detection light described later. good.

As will be described later, in the hologram recording / reproducing method of the present invention, for example, the recording / reproducing region in the recording medium 10 is in the radial direction from the rotation center C of the recording medium toward the outer peripheral edge according to the formation position of the positioning guide groove 12. Each recording / reproducing portion B1 is further divided into a plurality of block units B2 arranged in the circumferential direction of the recording medium 10, and each block unit B2 is divided into spherical reference optical shift multiple recording. Is done. Therefore, it is preferable that each of the block units B2 on the recording medium 10 is provided with a marking unit 18 on which marking information such as the position information of the block unit B2 is recorded.
The marking unit 18 can be configured by a phase hologram having a multi-gradation uneven pattern as described above. Further, the sign unit 18 may be composed of, for example, a bar code or a QR code (registered trademark). The labeling portion 18 can be formed on the surface of the light transmissive substrate 16, for example.

In the hologram recording / reproducing method of the present invention, the irradiation positions of the signal light and the spherical reference light are positioned with respect to the position of the marker 13 on the recording medium 10 and intersect with the tangential direction of the positioning guide groove 12 at the position of the marker 13. It is characterized by performing spherical reference optical shift multiple recording in one direction. The hologram recording method may be either transmissive recording or reflective recording.

In positioning the irradiation positions of the signal light and the spherical reference light with respect to the recording medium, the wavelengths of the signal light and the spherical reference light are different from those of the signal light and the spherical reference light because they are insensitive to the photoreactive monomers constituting the hologram recording layer 15 in the recording medium 10. Light for detecting a servo error signal having the above, for example, red laser light is used. The servo error signal detection light is, for example, irradiated at the same position as the signal light through the condenser lens.

First, by irradiating the servo error signal detection light toward the positioning guide groove 12 in the recording medium 10, the diffracted light emitted from the positioning guide groove 12 is detected by the split photodetector. Here, when the servo error signal detection light is applied to the positioning guide groove 12, the differential output becomes zero. On the other hand, when the servo error signal detection light is irradiated at a position deviated from the positioning guide groove 12, the amount of diffracted light incident on each of the plurality of detection regions on the light receiving surface of the split photodetector. A differential output corresponding to the difference can be obtained.
Then, the irradiation position of the servo error signal detection light follows the positioning guide groove 12 as the recording medium 10 rotates so that the servo error signal obtained from the differential output of the split photodetector becomes zero. Control. The irradiation position of the servo error signal detection light can be adjusted, for example, by driving the condenser lens with an actuator. Further, the recording medium 10 may be moved in a plane along the surface thereof.
Next, the position of the marker 13 located in the positioning guide groove 12 is detected by the servo error signal detection light, so that the irradiation positions of the signal light and the spherical reference light are positioned with respect to the position of the marker 13. .. Similarly, for the detection of the marker 13, the irradiation position of the servo error signal detection light is adjusted based on the marker detection signal obtained from the differential output of the split photodetector.

The spherical reference light shift multiple recording intersects the tangential direction of the positioning guide groove 12 at the position of the marker 13 in a state where the irradiation positions of the signal light and the spherical reference light are positioned with respect to the position of the predetermined marker 13. This is performed by moving one of the optical head and the recording medium 10 that irradiate the signal light and the spherical reference light in the uniaxial direction relative to the other. As a result, as shown in FIG. 3, a shift multiple hologram sequence HL recorded so that a plurality of holograms H are arranged in one direction in a state where a plurality of holograms H partially overlap each other is recorded. Here, one hologram H has a substantially circular shape in a plan view, and its size is, for example, 500 μm in diameter.

Explaining the principle of spherical reference light shift multiple recording with reference to FIG. 4, it is considered that the spherical reference light has a plurality of plane waves. Therefore, as shown in FIG. 4A, the recording medium 10 on which the hologram H1 is recorded is placed in one direction (right in FIG. 4A) along the surface of the recording medium 10 (upper surface in FIG. 4A). If a slight distance shift is made in the direction), the already recorded hologram H1 cannot be reproduced, and a new hologram H2 is recorded in a state where a part of the recording area overlaps with the already recorded recording area of the hologram H1. Is possible. The shift amount of the recording medium 10 is usually about 10 μm or more. In FIG. 4A, the hologram H1 and the hologram H2 are shown in a separated state for convenience.
As shown in FIG. 4B, the reproducible condition is a case where the wave number vector ks of the signal light, the wave number vector kr of the reference light, and the wave number vector (recording lattice vector) kg of the hologram satisfy the Bragg diffraction condition. .. When the recording medium 10 is shifted, as shown in FIG. 4C, the wave number vector relationship deviates from Bragg's diffraction conditions, and the hologram H1 cannot be reproduced.
Here, FIG. 4B is an explanation showing the relationship between the wave number vector ks of the signal light related to the hologram H2 in FIG. 4A, the wave number vector kr of the reference light, and the wavenumber vector (recording lattice vector) kg of the hologram. It is a figure. Further, FIG. 4C shows a wave number vector ks of the signal light related to the hologram H1 recorded earlier, a wave number vector kr of the reference light, and a wavenumber vector of the hologram (recording lattice vector) in the state shown in FIG. 4A. ) It is explanatory drawing which shows the relationship with kg.

In the hologram recording / reproduction method of the present invention, after recording the first shift multiplex hologram sequence on a recording medium, the spherical reference light is emitted to the primary shift multiplex hologram in the same recording area as the first shift multiplex hologram sequence. A new shift multiple hologram sequence may be multiple-recorded by irradiating from an incident direction different from the spherical reference light used for recording the column. Alternatively, after irradiating the signal light and the spherical reference light from one side of the recording medium to record the first shift multiple hologram sequence on the recording medium, the signal light is irradiated from one side of the recording medium and the other side of the recording medium. A new shift multiplex hologram sequence may be overwritten in the same recording area as the first shift multiplex hologram sequence by irradiating the spherical reference light from the side.
Even when shift multiplex recording is performed by such a method, since each shift multiplex hologram sequence has recording lattice vectors in different directions, the recorded information is high without causing crosstalk. Capacity can be increased efficiently.

Further, in the hologram recording / reproduction method of the present invention, a plurality of shift multiple hologram sequences are multiple-recorded in the same region of the recording medium in a state where a part of the region in which each shift multiple hologram sequence is recorded overlaps with each other. By doing so (cross-shift multiple recording), the density of recorded information can be increased.
As shown in FIG. 5A, a first shift multiple hologram sequence (white arrow) is performed by performing spherical reference optical shift multiple recording in a recording area (recording track) corresponding to a predetermined marker 13 on the recording medium 10. ) Is recorded. Then, as shown in FIG. 5B, the recording medium 10 is rotated at a rotation angle θ of a predetermined size, and the recording medium 10 is moved in a plane along the surface of the recording medium 10 according to the rotation angle θ. The recording medium 10 is translated by the amounts Δx and Δy, and the position of the marker 13 on the recording medium 10 is positioned at the position when the first shift multiplex hologram sequence (indicated by the white arrow) is recorded. At this time, the irradiation positions of the recording / reproducing light and the servo signal detection light are at the same positions as when the first shift multiplex hologram sequence is recorded.
In this state, a second shift multiple hologram sequence (indicated by a filled arrow) is recorded by performing a new uniaxial spherical reference optical shift multiple recording. As a result, it is possible to obtain a state in which the first shift multiple hologram sequence and the second shift multiple hologram sequence are multiple-recorded in a state in which a part of the recording area of each shift multiple hologram sequence overlaps with each other. In the hologram recording / reproducing method of the present invention, such an operation is repeatedly performed. The angle at which the shift multiple hologram trains are crossed (rotation angle θ) is, for example, about 10 degrees.

In the present invention, for example, spherical reference optical shift multiple recording is continuously performed in each of two block units located at points symmetrical with respect to the rotation center of the recording medium 10 on the same circumference. The first shift multiplex hologram sequence is recorded. As shown in FIG. 3, in the block unit B2, the spherical reference optical shift multiple recording with respect to the recording area corresponding to each of the plurality of markers 13 located in the same positioning guide groove 12 by rotating the recording medium 10. Are performed in sequence. Then, after the first shift multiple hologram sequence is formed for all the block units, the second shift multiple hologram sequence is recorded in each block unit by the same recording method as the first shift multiple hologram sequence. Will be done. The block unit designation is the block information reproduction emitted from the labeling unit 18 by the irradiation of the block information reading light emitted from the laser light source that emits the laser light of the wavelength different from the recording / reproduction light source or the reading light source composed of the LED light source. This is done by detecting the light La.

In positioning the irradiation positions of the signal light and the spherical reference light when performing cross-shift multiple recording in the hologram recording / reproducing method of the present invention, the split photodetector divides the light receiving surface into a plurality of detection regions. It is preferable that the posture is controlled so that one of the boundary lines extends in an angular direction parallel to the tangential direction of the positioning guide groove at the position of the marker related to the hologram recording / reproduction start position. As a result, an appropriate marker detection signal can be detected, and the irradiation position of the signal light and the spherical reference light can be accurately positioned with respect to the marker.

For example, when a split photodetector in which the light receiving surface is divided into two detection regions is used as an example, when the first shift multiplex hologram sequence is recorded, it is shown in FIG. 6 (a). As described above, in the split photodetector 50, the boundary line BL that divides the light receiving surface into the two detection regions 51a and 51b extends in an angular direction parallel to the tangential direction T of the positioning guide groove 12 at the position of the marker 13. The attitude is controlled. As described above, when performing cross-shift multiplex recording, the recording medium on which the first shift multiplex hologram sequence is recorded is rotated at a predetermined angle θ. Therefore, when the attitude control of the split photodetector 50 is not performed, the boundary line BL on the light receiving surface of the split photodetector 50 is the position of the marker 13, as shown by the broken line in FIG. 6 (b). The rotation angle θ is tilted with respect to the tangential direction T of the positioning guide groove 12 in the above. Therefore, by rotating the split photodetector 50 according to the rotation angle θ of the recording medium, the boundary line BL on the light receiving surface 51 is parallel to the tangential direction T of the positioning guide groove 12 at the position of the marker 13. Attitude control is performed so that it extends in the angular direction.

In the above, assuming that the recording medium is rotated without eccentricity, if the irradiation position of the servo error signal detection light is positioned so that the servo error signal detection light is irradiated to the positioning guide groove, the servo error signal detection is performed. The lighting follows the positioning guide groove as the recording medium rotates. Therefore, as the recording medium rotates, the position of the marker in the positioning guide groove with respect to the irradiation position of the servo error signal detection light does not deviate in the radial direction. On the other hand, when the recording medium is eccentrically rotated, as shown in FIG. 7, each marker 13 in the positioning guide groove 12 is displaced in the radial direction with respect to the irradiation position of the servo error signal detection light. In FIG. 7, the straight line indicated by the alternate long and short dash line indicates the positioning guide groove (trajectory of the irradiation position of the servo error signal detection light) when the recording medium is rotated without eccentricity, and the white circle indicates the marker 13. show.

Therefore, in the hologram recording / reproducing method of the present invention, it is preferable to perform position correction for correcting the positional deviation of the irradiation position of the signal light and the spherical reference light due to the eccentric rotation of the recording medium with respect to the marker position.
The position correction can be performed, for example, by moving the recording medium in a plane along the surface of the recording medium so that the servo error signal generated by the eccentric rotation of the recording medium becomes zero level. Further, when the first shift multiple hologram train HL is recorded when performing the cross shift multiple recording, the reference hologram HS in the first shift multiple hologram train HL is irradiated with the reference light for proper reproduction. It can also be done by moving the recording medium so that light is obtained. Alternatively, the recording medium is moved so as to obtain the correlated signal light by irradiating the signal light having the phase information of the data pattern of the reference hologram HS and the phase-coupled data pattern in the first shift multiplex hologram train HL. You can also.

Hereinafter, a hologram recording / reproducing device in which the above hologram recording / reproducing method is executed will be described.

The hologram recording / playback apparatus of the present invention records a recording / reproducing light irradiation optical system that irradiates a recording medium with signal light and spherical reference light generated by separating recording / reproducing light from a recording / reproducing light source, and light for detecting a servo error signal. An optical head having a light irradiation optical system for detecting a servo error signal to irradiate a medium and a reproduced light (diffractive light) emitted from the hologram by irradiating a hologram recorded on the recording medium with spherical reference light are detected. Servo error obtained from the regenerated light detection optical system, the split-type photodetector that detects the diffracted light emitted from the positioning guide groove and marker by the servo error signal detection light, and the differential output from the split-type photodetector. A control mechanism that positions the optical head with respect to the recording medium based on the signal and the marker detection signal, an optical head moving mechanism that moves the optical head in one direction along the surface of the recording medium, and a moving direction of the optical head that moves the recording medium. It is provided with a recording medium driving mechanism that rotates and moves in parallel in a plane including.

As shown in FIG. 8, the recording / reproducing light irradiation optical system modulates the light for signal light separated from the recording / reproducing light emitted from the recording / reproducing light source by using the spatial information corresponding to the page data to be recorded. A spatial light modulator (SLM) 21 that generates signal light Ls, a signal light condensing objective lens 20 that collects signal light Ls and irradiates the recording medium 10, and recording / playback emitted from a recording / playback light source. It is provided with a reference light condensing objective lens 30 that converts the light for reference light separated from the light into a spherical wave, condenses it as spherical reference light Lr, and irradiates the recording medium 10. Reference numeral 35 denotes a wavelength selective mirror that transmits light for reference light and reflects light for reading block information, which will be described later.

The regenerated light detection optical system detects the regenerated light (diffracted light) Lg emitted from the hologram by irradiating the hologram recorded on the recording medium 10 with the spherical reference light Lr via the regenerating light condensing lens 41. The image pickup element 40 is provided. Reference numeral 45 denotes a deflecting beam splitter that transmits the reproduced light (diffracted light) Lg emitted from the hologram and reflects the diffracted light emitted from the positioning guide groove and the marker described later.

In the servo error signal detection light irradiation optical system, for example, as shown in FIG. 9, the servo error signal detection light Lc emitted from a light source separate from the recording / reproduction light source is coaxial with the signal light Ls and the signal light Ls. It is configured to be irradiated from the same direction as the irradiation direction via the signal light condensing objective lens 20. Reference numeral 25 denotes a deflecting beam splitter that transmits the signal light Ls and reflects the servo error signal detection light Lc. In such a configuration, the servo error signal detection light Lc has a polarization direction orthogonal to the signal light Ls.
The light irradiation optical system for detecting the servo error signal may constitute an optical system separate from the signal light irradiation optical system. In this case, the light Lc for detecting the servo error signal is condensed and recorded on the recording medium 10. The configuration is provided with a condenser lens that irradiates the signal light Ls at the same position as the irradiation position in the above.

In this example, the diffracted light emitted from the positioning guide groove and the diffracted light Ld emitted from the marker 13 are incident on the deflection beam splitter 45 via, for example, the regenerated light condensing lens 41 in the regenerated light detection optical system. The split light detector 50 is positioned so that the diffracted light Ld reflected by the deflection beam splitter 45 is incident.
Further, in the hologram recording / reproducing device of the present invention, by rotating the split photodetector 50 according to the rotation angle of the recording medium 10, one of the boundary lines on the light receiving surface is a positioning guide groove at the position of the marker 13. An attitude control means (not shown) for controlling the attitude is provided so as to extend in an angular direction parallel to the tangential direction of the.

Further, the optical head irradiates the marking unit 18 on which the marking information (block information) related to the block unit B2 set in the recording medium 10 is recorded with the light for reading the block information from the light source for reading the marking information. It has an optical system. As shown in FIG. 10, for example, this optical system is configured such that the block information reading light Lb is irradiated through the optical path in the reference light irradiation optical system. The reading light source can be composed of, for example, a laser light source or an LED light source that emits a laser light having a wavelength different from that of the hologram recording / reproducing light source.
The block information reproduction light La emitted from the labeling unit 18 by the irradiation of the block information reading light Lb is reflected by the deflection beam splitter 45 and incident on the split photodetector 50.

The hologram recording / reproducing device of the present invention may be configured to superimpose a shift multiple hologram sequence in the same recording area on a recording medium by changing the incident direction of the spherical reference light with respect to the signal light. In such a configuration, for example, a plurality of reference light condensing objective lenses are arranged on one side of the recording medium. For example, FIG. 11 shows an example in which two reference light condensing objective lenses 30a and 30b are arranged on one side of the recording medium 10. Each of the reference light condensing objective lenses 30a and 30b is irradiated with spherical reference lights Lr1 and Lr2 having wavenumber vectors that can obtain recording lattice vectors in different directions in relation to the wavenumber vector of the signal light. Be placed.

Furthermore, the hologram recording / playback apparatus of the present invention is configured to superimpose a shift multiple hologram sequence by transmission type hologram recording and a shift multiplex hologram sequence by reflection type hologram recording in the same recording area on the recording medium. You may. In such a configuration, at least one reference light condensing objective lens is arranged on each of one side and the other side of the recording medium. For example, FIG. 12 shows an example in which one reference light condensing objective lens 30a and 30b are arranged on each of one side and the other side of the recording medium 10. Each of the reference light condensing objective lenses 30a and 30b is irradiated with spherical reference lights Lr1 and Lr2 having wavenumber vectors that can obtain recording lattice vectors in different directions in relation to the wavenumber vector of the signal light. Be placed. For example, it is preferable that the reference light condensing objective lenses 30a and 30b are arranged so that the recording lattice vector of the transmissive hologram and the recording lattice vector of the reflective hologram are opposite to each other.

Therefore, in the hologram recording / reproducing method of the present invention and the hologram recording / reproducing device in which the hologram recording / reproducing method is carried out, the positioning of the irradiation positions of the signal light Ls and the spherical reference light Lr with respect to the recording medium 10 is performed on the recording medium 10. By performing this based on the distribution of the light receiving intensity of the diffracted light Ld emitted from the positioning guide groove 12 and the marker 13, it is possible to accurately position the irradiation positions of the signal light and the reference light, and multiple hologram recording is performed. Can be performed with high reliability.
In particular, when cross-shift multiple recording is performed on the same recording area on the recording medium 10, not only the recording medium 10 is rotated, but also the optical head or the recording medium 10 is placed in a plane along the surface of the recording medium 10. The present invention becomes extremely useful when the irradiation positions of the signal light Ls and the spherical reference light Lr are positioned with respect to the recording medium 10 by translating them in parallel.

Further, the above effect can be obtained more reliably by performing position correction for correcting the positional deviation of the irradiation position of the signal light and the spherical reference light due to the eccentric rotation of the recording medium with respect to the marker position.

10 Recording medium 11 Support board 12 Positioning guide groove 13 Marker 15 Hologram recording layer 16 Light transmissive board 18 Labeling part 20 Signal light focusing objective lens 21 Spatial light modulator (SLM)
25 Deflection beam splitter 30 Reference light condensing objective lens 30a Reference light condensing objective lens 30b Reference light condensing objective lens 35 Wavelength selective mirror 40 Imaging element 41 Regenerative light condensing lens 45 Deflection beam splitter 50 Split type Optical detector 51a Detection area 51b Detection area B1 Recording / playback part B2 Block unit BL Boundary line H Hologram H1 Hologram H2 Hologram HL Shift multiplex hologram string HS Reference hologram La Block information Reproduction light Lb Block information reading light Lc Servo error signal detection Light Diffracted light emitted from the Ld marker Lg Regenerated light Lr Spherical reference light Ls Signal light

Claims (4)

The hologram obtained by interfering the signal light generated by separating the recording / reproducing light with the spherical reference light is multiple-recorded on the recording medium by the shift multiplexing method, and the recording medium on which the hologram is recorded is irradiated with the spherical reference light. In the hologram recording / reproducing method, which reproduces the data information recorded on the hologram by doing so,
As a recording medium, a plurality of positioning guide grooves are formed concentrically, and a plurality of markers whose positions can be detected by light are formed at positions arranged in the circumferential direction at a predetermined pitch in each positioning guide groove. Disc-shaped ones are used
From an optical head equipped with a recording / reproducing light irradiation optical system and a light irradiation optical system for detecting servo error signals, light for detecting servo error signals having a wavelength that is insensitive to the recording layer in the recording medium is irradiated toward the positioning guide groove. As a result, the diffracted light emitted from the positioning guide groove is detected by the split type photodetector, and the irradiation of the servo error signal detection light is based on the servo error signal obtained from the differential output of the split type photodetector. The signal light is controlled by controlling the position to follow the positioning guide groove as the recording medium rotates, and by detecting the position of the marker located in the positioning guide groove by the servo error signal detection light. And the position of the irradiation position of the spherical reference light with respect to the position of the marker is performed.
Shift multiple recording is performed in one direction that intersects the tangential direction of the positioning guide groove at the position of the marker.
In the split photodetector, one of the boundary lines that divides the light receiving surface into a plurality of detection regions extends in an angular direction parallel to the tangential direction of the positioning guide groove at the position of the marker corresponding to the hologram recording / playback start position. , A hologram recording / playback method characterized by attitude control. After recording the first shift multiple hologram sequence in which a plurality of holograms partially overlap each other in one direction, the recording medium is rotated in a plane along the surface of the recording medium and the optical head. A second shift multiple hologram sequence is performed by performing new shift multiple recording in a state where the optical head is positioned with respect to the recording medium by moving one in parallel with a movement amount corresponding to the rotation angle of the recording medium. The hologram recording / reproduction method according to claim 1, wherein a part of the recording area is overlapped with the recording area of the first shift multiplex hologram sequence. When recording the second shift multiple hologram sequence, after positioning the optical head with respect to the recording medium, the irradiation position of the servo error signal detection light corresponds to the recording area in which the first shift multiple hologram sequence is recorded. The hologram recording / reproducing method according to claim 2, wherein position correction is performed to match the position of the marker. The hologram formed by interfering the signal light carrying the data information with the spherical reference light is multiple-recorded by the shift multiplexing method, and the hologram recorded on the recording medium is recorded on the hologram by irradiating the spherical reference light. In a hologram recording / playback device that reproduces the data information
As a recording medium, a disk shape in which a plurality of positioning guide grooves are formed concentrically and markers whose positions can be detected by light are arranged in the circumferential direction at a predetermined pitch in each positioning guide groove. Is used,
Recording / playback light irradiation that irradiates the recording medium with signal light and spherical reference light generated by separating the recording / playback light from the recording / playback light source. An optical head having a light irradiation optical system for detecting a servo error signal that irradiates the recording medium with light, and a split type light detector that detects the diffracted light emitted from the positioning guide groove and the marker by the light for detecting the servo error signal. A control mechanism that positions the optical head with respect to the recording medium based on the servo error signal and marker detection signal obtained from the differential output of the type optical detector, and optics that move the optical head in one direction along the surface of the recording medium. A head moving mechanism, a recording medium driving mechanism that rotates and parallel moves the recording medium in a plane including the moving direction of the optical head, and a boundary line that divides the light receiving surface of the split type optical detector into a plurality of detection regions. A hologram characterized in that one is provided with an attitude control means for controlling the attitude of the split-type optical detector so as to extend in an angular direction parallel to the tangential direction of the positioning guide groove at the position of the marker at the hologram recording / reproduction start position. Recording / playback device.

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