JP2005257885A - Recording or reproducing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recording and reproducing apparatus with which the surface of a recording medium can be irradiated with light used for recording and reproducing of information with good accuracy. <P>SOLUTION: Object light 50 is condensed by an objective lens 309 and reference light 51 is deflected by a hologram element 316 and both are irradiated to an information recording region of the hologram recording medium 1. Sensing light 52 transmitted through the objective lens 309 is irradiated to a servo information region. A photodetector 322 for servo detects position information based on the reflected light of the sensing light 52. A photodetector 326 for servo detects position information based on the transmitted light of the sensing light 52. The objective lens 309, a deflecting means 315, the hologram element 316, and an objective lens 323 are moved and controlled in a focusing control direction or tracking control direction based on the focusing drive signal and tracking drive signal generated based on the position information. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a recording / reproducing apparatus that records information on a hologram memory medium and reproduces the recorded information.

  In recent years, rewritable optical discs such as phase change type and magneto-optical type are widely used as information recording media. In order to further increase the recording density of these optical discs, techniques such as reducing the beam spot diameter and shortening the distance between adjacent tracks or adjacent bits are required.

  As described above, the density of optical discs is increasing year by year. However, since the above optical disc records data in a plane, the recording density is limited to the diffraction limit of light, and physical recording of high density recording is performed. Approaching the limit. Therefore, in order to further increase the capacity, three-dimensional (volume type) multiplex recording including the depth direction is required.

  Therefore, a hologram memory having both a large capacity derived from a three-dimensional multiple recording area and a high speed derived from a two-dimensional batch recording / reproducing system has attracted attention as a next-generation computer file memory. Hologram memory, for example, irradiates a recording medium formed by sandwiching a recording layer made of a photopolymer or the like between two glass plates with object light corresponding to recording information and reference light, and is generated by both lights The recorded interference fringes are recorded as a change in the refractive index of the recording material. When reproducing the information, only the reference light is irradiated to the recorded interference fringes, and the recorded information is based on the diffracted light of the reference light. The optical information corresponding to is extracted.

  Since this hologram memory can multiplex-record a plurality of two-dimensional data in the same area, it has been attracting attention as a terabyte memory having a huge recording capacity while having the same shape as a CD or the like. With respect to a reproducing apparatus for such a hologram memory, for example, as shown in Patent Document 1, a technique for writing a positioning signal as hologram information separately from a data signal has been proposed.

Japanese Patent Application Laid-Open No. 2004-228561 provides an address servo area in which positioning information for controlling the positions of object light and reference light is provided on a recording medium, and positions the object light and reference light based on this information. Is described. Patent Document 3 describes a technique for deflecting an incident light beam by relatively rotating a pair of wedge-shaped prisms using a rotating mechanism, and recording data on a recording medium in a multiplexed manner.
JP 2000-268380 A JP 10-124872 A JP 2000-338846 A

  However, although the technique described in Patent Document 1 can record data on the entire surface of a recording medium, for example, when reproducing data in different drive devices, the deviation of the spindles of the respective drive devices. The center amount is different, and the amount of eccentricity changes every time the recording medium is chucked. Therefore, there is a problem that compatibility between apparatuses is poor and accurate positioning control is difficult.

  In the technique described in Patent Document 2, since the address / servo areas are provided at predetermined intervals, the recording area is reduced. Further, since the sampled servo system is used as the servo system, there is a problem that it is necessary to move the recording medium at a high speed and there is a limitation in recording and reproduction time. Further, in the technique described in Patent Document 3, since a pair of wedge prisms is used, two parts are required, and two rotation driving units for rotating the parts are required, which complicates the apparatus. And there was a problem of increasing the size.

  The present invention has been made in view of the above-described problems, and provides a recording / reproducing apparatus capable of accurately irradiating a recording medium with light used for recording and reproducing information. Objective. It is a second object of the present invention to provide a recording / reproducing apparatus capable of detecting a servo signal regardless of the moving speed of the recording medium and performing multiplex recording of data without increasing the size of the apparatus. .

  The present invention has been made to solve the above problems, and the invention according to claim 1 irradiates an optical recording medium with object light and reference light, and interferes with the information of the object light on the optical recording medium. Provided on the first main surface side of the optical recording medium in a recording / reproducing apparatus for recording information as a fringe and irradiating the interference light with the reference light and reproducing information based on the diffracted light of the reference light Object light irradiating means for condensing the object light by a first objective lens and irradiating the object light on an information recording area on the optical recording medium on which information is recorded; and the reference light on the information recording area The first recording light for position detection is condensed by the reference light irradiating means for irradiating from the first or second main surface side and the first objective lens for condensing the object light, and the optical recording is performed. A first area for irradiating an area different from the information recording area on the medium; A light emitting irradiation means; and a control means for controlling an irradiation position of the object light and the reference light based on a position detection result by the first detection light, and is incident on the first objective lens. An optical axis of object light and an optical axis of the first detection light are non-parallel.

  In an area different from the information recording area on the optical recording medium, for example, a concave or convex portion is formed, and is distinguished from the information recording area. The object light irradiation unit, the reference light irradiation unit, and the first detection light irradiation unit include a light source, a lens, and the like. The object light irradiating means condenses the object light to which information to be recorded is added by a first objective lens provided on the first main surface side of the optical recording medium, and collects it in the information recording area of the optical recording medium. Irradiate. The reference light irradiation means irradiates the information recording area with reference light for forming interference fringes and for reproducing information from the first or second main surface side of the optical recording medium. The first detection light irradiation means condenses the first detection light by the first objective lens and irradiates an area different from the information recording area.

  The first detection light has, for example, position information in the direction parallel to the recording surface of the optical recording medium or in the normal direction of the recording surface, and the control means uses the object light and the reference light based on this position information. Control the irradiation position. The optical axis of the object light incident on the first objective lens and the optical axis of the first detection light are non-parallel. For example, the optical axis of the object light and the optical axis of the first detection light can be made non-parallel by setting the positions of the optical components included in the object light irradiation means and the first detection light irradiation means. .

  According to a second aspect of the present invention, there is provided the recording / reproducing apparatus according to the first aspect, wherein the second objective lens that is provided on the second main surface side and collects the transmitted light of the first detection light is provided. Further, the reference light irradiating means irradiates the information recording area with the reference light from the second main surface side, and the control means outputs a position detection result by reflected light of the first detection light. Based on this, the irradiation position of the object light is controlled, and the irradiation position of the reference light is controlled based on the position detection result by the transmitted light of the first detection light.

  The first detection light passes through the optical recording medium and is collected by the second objective lens. The reference light is applied to the information recording area from the second main surface side. The control unit controls the irradiation position of the object light based on the detection result of the position of the first detection light reflected by the optical recording medium, and detects the position of the first detection light by the transmitted light. Based on the result, the irradiation position of the reference light is controlled.

  According to a third aspect of the present invention, in the recording / reproducing apparatus according to the first aspect, the second detection light for position detection is condensed by the second objective lens provided on the second main surface side. And a second detection light irradiating means for irradiating an area different from the information recording area on the optical recording medium, wherein the reference light irradiating means emits the reference light to the information recording area. Irradiating from the surface side, the control means controls the irradiation position of the object light based on the detection result of the position by the reflected light of the first detection light, and by the reflected light of the second detection light. The irradiation position of the reference light is controlled based on the position detection result.

  According to a fourth aspect of the present invention, in the recording / reproducing apparatus according to the second or third aspect, the optical axes of the first and second objective lenses coincide with each other.

  According to a fifth aspect of the present invention, in the recording / reproducing apparatus according to the third aspect, the optical axis of the second detection light incident on the second objective lens and the optical axis of the second objective lens are not It is characterized by being parallel.

  According to a sixth aspect of the present invention, in the recording / reproducing apparatus according to any one of the second to fifth aspects, the reference light irradiation means includes a light beam deflecting means for deflecting the reference light, and the information The image forming apparatus further includes a rotating unit that rotates the second objective lens and the light beam deflecting unit integrally around the optical axis of the object light irradiated to the recording area.

  According to a seventh aspect of the present invention, in the recording / reproducing apparatus according to the sixth aspect, the light beam deflecting unit includes a first light beam deflecting unit and a second light beam deflecting unit, and the first light beam deflecting unit includes: A deflection surface that deflects the reference light, and is disposed at a position that intersects with the optical axis of the object light, and the reference light is incident at a position at which the deflection surface and the optical axis of the object light intersect. The second light beam deflecting unit deflects the reference light deflected by the deflecting surface and irradiates the information recording area.

  The deflection surface included in the first light beam deflecting unit is disposed at a position that intersects the optical axis of the object light. The reference light is incident on a position where the deflection surface and the optical axis of the object light intersect, and is deflected by the deflection surface. Another light beam deflecting unit may be provided between the deflecting surface and the second light beam deflecting unit. The second light beam deflecting unit deflects the reference light and irradiates the information recording area.

  According to an eighth aspect of the present invention, in the recording / reproducing apparatus according to any one of the first to seventh aspects, the wavefront conversion is arranged in the optical path of the reference light and converts the reference light into a non-plane wave. The apparatus further comprises means.

  According to a ninth aspect of the present invention, in the recording / reproducing apparatus according to the eighth aspect, the wavefront converting means spatially modulates the phase, amplitude, or traveling direction of the reference light.

  According to a tenth aspect of the present invention, in the recording / reproducing apparatus according to the eighth aspect, the wavefront converting means converts the reference light into a spherical wave. The means for converting the reference light into a spherical wave is, for example, a lens.

  The invention according to claim 11 is the recording / reproducing apparatus according to any one of claims 8 to 10, wherein the wavefront converting means is a hologram.

  For example, the hologram irradiates other optical recording media as light with the phase, amplitude, or traveling direction spatially modulated or transmitted through the lens as object light, and applies reference light to the position where the object light is irradiated. It is formed by irradiation.

  According to a twelfth aspect of the present invention, in the recording / reproducing apparatus according to the eighth aspect, the wavefront conversion unit includes a first wavefront conversion unit that spatially modulates a phase of the reference light, and an amplitude of the reference light. Of the second wavefront converting means for spatially modulating, the third wavefront converting means for spatially modulating the traveling direction of the reference light, and the fourth wavefront converting means for converting the reference light into a spherical wave And at least two.

  According to a thirteenth aspect of the present invention, in the recording / reproducing apparatus according to the eighth aspect, the wavefront converting means includes first wavefront converting means for spatially modulating the phase of the reference light, and the amplitude of the reference light. Functions of second wavefront conversion means for spatially modulating, third wavefront conversion means for spatially modulating the traveling direction of the reference light, and fourth wavefront conversion means for converting the reference light into a spherical wave Of these, a hologram having at least two functions is provided.

  According to a fourteenth aspect of the present invention, in the recording / reproducing apparatus according to any one of the eighth to thirteenth aspects, the wavefront converting means and the light beam deflecting means are integrally provided. Features.

  According to a fifteenth aspect of the present invention, in the recording / reproducing apparatus according to any one of the eighth to fourteenth aspects, the control means further includes transmitted light of the first detection light or the second detection light. By moving the second objective lens, the light beam deflecting unit, and the wavefront converting unit integrally in a direction parallel to the main surface of the optical recording medium based on the detection result of the position by the reflected light of the light, The irradiation position of the reference light is controlled.

  According to a sixteenth aspect of the present invention, in the recording / reproducing apparatus according to any one of the eighth to fourteenth aspects, the control means further includes a transmitted light of the first detection light or the second detection light. Based on the detection result of the position by the reflected light of the light, by moving the second objective lens, the light beam deflecting means and the wavefront converting means integrally in the normal direction of the main surface of the optical recording medium, The irradiation position of the reference light is controlled.

  According to a seventeenth aspect of the present invention, in the recording / reproducing apparatus according to any one of the first to sixteenth aspects, the object light, the reference light, and the detection light are generated by the same light source. It is characterized by.

  According to an eighteenth aspect of the present invention, in the recording / reproducing apparatus according to any one of the first to seventeenth aspects, a polarization direction of the object light and the reference light and a polarization direction of the detection light are orthogonal to each other. It is characterized by that.

  According to a nineteenth aspect of the present invention, there is provided a recording / reproducing apparatus according to any one of the sixth to eighteenth aspects, wherein a plurality of information on the object light is recorded in the same area of the optical recording medium. As described above, a combination of the peristaltic multiplexing method and the shift multiplexing method is used.

  According to the present invention, the position information is detected by the detection light, and based on the position information, the irradiation position on the recording medium of the light used for recording and reproducing the information is controlled. The effect that the light used for reproduction can be accurately irradiated onto the recording medium is obtained.

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a recording / reproducing apparatus according to an embodiment of the present invention. In the figure, reference numeral 1 denotes a hologram recording medium (optical recording medium) on which information is recorded by interference fringes formed by object light and reference light. A spindle motor 2 rotates the hologram recording medium 1 at a constant linear velocity, for example, when the outer shape of the hologram recording medium 1 is a disk. The number of rotations is controlled by the output of the driver IC 7.

  Reference numeral 3 denotes an optical pickup, optical components such as a laser light source (not shown), a collimator lens, an objective lens, and a polarizing beam splitter (object light irradiation means, reference light irradiation means, detection light irradiation means, wavefront conversion means, etc.), focusing An actuator (control means), a tracking actuator (control means), and a two-dimensional light detection array as a light receiving element are provided. The objective lens is driven in the thickness direction of the hologram recording medium 1 by a focusing actuator, and is driven in the in-plane direction of the recording surface of the hologram recording medium 1 by a tracking actuator.

  A feed motor (control means) 4 is a mechanism for sending the optical pickup 3 from the inner periphery to the outer periphery of the hologram recording medium 1, for example. The feed motor 4 controls the position of the optical pickup 3 based on the drive signal of the tracking actuator. Reference numeral 5 denotes a signal processing IC which receives a data reproduction signal, an address signal, a spindle control signal, a focus error signal, and a track error signal based on the return light from the hologram recording medium 1 incident on a light receiving element such as a two-dimensional photodetection array. Generate. Further, the signal processing IC 5 generates a focusing drive signal and a tracking drive signal based on the generated focus error signal and track error signal, and outputs them to the driver IC 7 together with the spindle control signal.

  The address signal is a signal for detecting a physical address on the hologram recording medium 1 detected based on the data reproduction signal. The spindle control signal is a signal for controlling the rotation of the spindle motor 2, and is a signal based on the address signal. The focus error signal is a signal for detecting a focus shift of the irradiation laser in the optical pickup 3, and the track error signal is a signal for detecting a track shift of the irradiation laser in the optical pickup 3. The focus error signal is generated by the astigmatism method or the like based on the return light output obtained by the light receiving element in the optical pickup 3, for example. The track error signal is generated by, for example, a push-pull method.

  Reference numeral 6 denotes a CPU (Central Processing Unit), which controls the entire apparatus based on a control program stored in a ROM (ROM: Read Only Memory) (not shown). In the present embodiment, the CPU 6 controls various servo operations related to information recording and reproduction operations on the hologram recording medium 1.

  The driver IC 7 amplifies the focusing drive signal, the tracking drive signal, and the spindle control signal input from the signal processing IC 5 to desired magnitudes, and supplies them to the focusing actuator, tracking actuator, and spindle motor 2, respectively. Further, the feed motor drive signal generated from the tracking drive signal is amplified to a desired magnitude and supplied to the feed motor 4.

  FIG. 2 is a cross-sectional structure diagram showing a cross-sectional structure of the hologram recording medium 1. In the figure, reference numeral 100 denotes a substrate having a concave (convex) portion formed in advance. On the substrate 100, a semi-transmissive film layer 101, a protective layer 102, a recording layer 103, and a protective layer 104 are stacked in this order, and the protective layer 104 is covered with the substrate 105. The recording layer 103 can be expected to have high reading (reproduction) efficiency, recording and erasing can be repeated, and there is no deterioration in characteristics due to the recording layer 103. Multiple recording is possible and high resolution can be expected. A single crystal or the like is used.

  The distance A between the concave (convex) portions is approximately 100 to 500 (μm) depending on the optical system, and the interval B between the convex (concave) portions is approximately 0.1 to 2 (μm) although it depends on the optical system. ) A flat area between the concave (convex) parts is the information recording area 106, and a concave (convex) part is the servo information area 107. Reference numerals 108 and 109 denote main surfaces of the hologram recording medium 1. The outer shape of the hologram recording medium 1 may be a disk type or a card type.

  FIG. 3 is a schematic configuration diagram showing a schematic configuration of an optical system provided in the optical pickup 3. In the figure, reference numeral 301 denotes a laser serving as a light source. Reference numeral 302 denotes a lens such as a collimator lens, which converts light emitted from the laser 301 into parallel rays. A beam splitter 303 transmits and reflects light transmitted through the lens 302 in accordance with transmission / reflection characteristics. Reference numeral 304 denotes a half-wave plate that emits light by rotating the polarization plane of incident light. A polarization beam splitter 305 transmits P-polarized light and reflects S-polarized light.

  Reference numeral 306 denotes a half-wave plate. A spatial light modulator 307 adds two-dimensional data to the transmitted light. Reference numeral 308 denotes a polarization beam splitter. Reference numeral 309 denotes an objective lens (first objective lens) that collects object light and detection light and irradiates the hologram recording medium 1.

  Reference numerals 311 to 313 denote deflection prisms that deflect light. Reference numeral 314 denotes a beam splitter. Reference numeral 315 denotes a deflection unit (light beam deflection unit), which includes a beam splitter 315a and a deflection surface 315b. Reference numeral 316 denotes a hologram element (wavefront conversion means) that simultaneously has a condensing function and an effect of spatially randomizing the phase and amplitude of the light beam. Details of the hologram element 316 will be described later.

  Reference numeral 317 denotes a condensing lens having a condensing function. Reference numeral 318 denotes a two-dimensional light detection array that detects two-dimensional data included in the diffracted light of the reference light to which reproduction information is added during reproduction. Reference numeral 319 denotes a deflecting prism. Reference numeral 320 denotes a condenser lens. Reference numeral 321 denotes a cylindrical lens. A light receiving element for servo 322 detects position information used for position control of object light based on reflected light of detection light for position detection. Reference numeral 323 denotes an objective lens (second objective lens). Reference numeral 324 denotes a condenser lens. Reference numeral 325 denotes a cylindrical lens. Reference numeral 326 denotes a servo light receiving element.

  The deviation between the object light and the reference light is detected as a focus error signal and a track error signal based on the output of the servo light receiving element 322 or 326. Based on the focus error signal and the track error signal, a focusing drive signal and a tracking drive signal are detected. Is generated. A focusing actuator (not shown) controls the movement of the objective lens 309 in the focusing control direction (normal direction of the recording surface; vertical direction in FIG. 3) based on a focusing drive signal based on the output of the servo light receiving element 322. Based on the focusing drive signal based on the output of the servo light receiving element 326, the deflection means 315, the hologram element 316, and the objective lens 323 are integrally moved in the focusing control direction.

  The tracking actuator (not shown) moves the objective lens 309 in the tracking control direction (in-plane direction orthogonal to the concave portion or convex portion of the recording surface; based on the tracking drive signal based on the output of the servo light receiving element 322; FIG. The deflection unit 315, the hologram element 316, and the objective lens 323 are integrally moved in the tracking control direction based on the tracking drive signal based on the output of the servo light receiving element 326. 50 is object light, 51 is reference light, and 52 is detection light.

  The optical system is an optical system based on the peristrolic multiplexing method (described later) in which the trajectory of the reference light 51 rotates around the optical axis of the object light 50 so as to draw a cone. In the peritropic multiplexing method, by rotating the reference beam 51, a plurality of pieces of information can be multiplexed and recorded in the same recording area. The deflecting unit 315, the objective lens 323, and the hologram element 316 rotate together. For example, a stepping motor or the like can be used as the rotating means for this purpose.

  Next, the irradiation method of the object light, the reference light, and the detection light according to the present embodiment will be described. The object light is light to which information to be recorded on the hologram recording medium 1 is added. The reference light is irradiated on the information recording area 106 of the hologram recording medium 1 together with the object light at the time of recording information to generate interference fringes, and is irradiated on the information recording area 106 of the hologram recording medium 1 at the time of reading information. This light is diffracted light including reproduction information. The detection light is applied to the servo information area 107 of the hologram recording medium 1 and is used for detecting position information for position control of the object light and the reference light.

  Light emitted from the laser 301 (for example, S-polarized light) is converted into parallel light by the lens 302 and passes through the beam splitter 303. This light has its polarization direction rotated by the half-wave plate 304 and is converted into light having both P-polarized light and S-polarized light components. Of this light, S-polarized light is reflected by the polarization beam splitter 305 and converted to P-polarized light by the half-wave plate 306. This light is given two-dimensional data by the spatial light modulator 307, passes through the polarization beam splitter 308, and is transmitted as object light 50 by the objective lens 309 near the recording layer 103 in the information recording area 106 of the hologram recording medium 1. Focused.

  On the other hand, among the light converted into light having both P-polarized light and S-polarized light components by the half-wave plate 304, the P-polarized light is transmitted through the polarization beam splitter 305 and is polarized by the polarizing prisms 311 to 313. Then, it is guided to the back surface of the hologram recording medium 1. This light passes through the beam splitter 314 and is reflected by the beam splitter 315a and the deflecting surface 315b. The reflected light is spatially random in phase and amplitude of the light beam by the hologram element 16, and is opposite to the object light 50 with respect to the information recording area 106 of the hologram recording medium 1 irradiated with the object light 50. To be irradiated as reference light 51.

  In the recording layer 103 of the information recording area 106 of the hologram recording medium 1, the object beam 50 and the reference beam 51 interfere with each other, and interference fringes are volume-recorded. The light quantity ratio between the object light 50 and the reference light 51 can be arbitrarily set by rotating the half-wave plate 304 around the optical axis. The light quantity ratio may be selected so that the interference fringe pattern is the clearest.

  When reproducing the recorded information, the half-wave plate 304 is rotated around the optical axis so that only the P-polarized component light is emitted from the half-wave plate 304. This light is transmitted through the polarization beam splitter 305, and the information recording area 106 of the hologram recording medium 1 on which the interference fringes are recorded is the same as the above-described operation of irradiating the hologram recording medium 1 with the reference light 51. The recording layer 103 is irradiated.

  This light is diffracted by the recording layer 103 and passes through the semi-transmissive film layer 101. The transmitted light enters the objective lens 309 and passes through the polarization beam splitter 308 and the spatial light modulator 307. This light passes through the polarizing beam splitter 305 and the condenser lens 317 and enters the two-dimensional light detection array 318. The two-dimensional photodetection array 318 reproduces two-dimensional data based on this light. When reproducing the recorded data, it is desirable that the spatial light modulator 307 be in a totally transmissive state or removed from the optical path. Further, the optical axis of the half-wave plate 306 is parallel or orthogonal to the vibration direction of the P-polarized light or is removed from the optical path.

  A part of the S-polarized light emitted from the laser 301 and converted into parallel light by the lens 302 is reflected by a beam splitter 303 (for example, transmittance 80%, reflectance 20%). This light is reflected by the deflecting prism 319 and enters the polarization beam splitter 308. This light is reflected by the polarization beam splitter 308 and enters the objective lens 309. The optical axis of the light incident on the objective lens 309 is set so as to be shifted by a minute angle from the optical axis of the object light 50 by the reflection optical components (beam splitter 303, deflection prism 319, polarization beam splitter 308, etc.) in the optical path. Has been. The light condensed by the objective lens 309 enters the servo information area 107 of the hologram recording medium 1 as the detection light 52.

  The light modulated by the concave (convex) portion formed in the servo information area 107 is reflected by the semi-transmissive film layer 101 and is made into substantially parallel light again by the objective lens 309. This light is reflected by the polarization beam splitter 308 and the deflecting prism 319 and passes through the beam splitter 303. Subsequently, this light is condensed by the condenser lens 320, is given astigmatism by the cylindrical lens 321, and enters the servo light receiving element 322. The servo light receiving element 322 detects position information for controlling the irradiation position of the object light 50 based on this light.

  On the other hand, the servo light receiving element 326 detects position information for controlling the irradiation position of the reference light 51 as follows. The light reflected by the deflection prism 313 is set so as to be shifted by a minute angle with respect to the optical axis of the object light 50. This light passes through the beam splitter 315 a and is condensed on the servo information area 107 of the hologram recording medium 1 by the objective lens 323. The condensed light is reflected by the semi-transmissive film layer 101 and converted into parallel light by the objective lens 323.

  This light passes through the beam splitter 315a and is partially reflected by the beam splitter 314. The reflected light is collected by the condensing lens 324, given astigmatism by the cylindrical lens 325, and enters the servo light receiving element 326. The servo light receiving element 326 detects position information for controlling the irradiation position of the reference light 51 based on this light.

  Further, the servo light receiving element 326 can also detect position information for controlling the irradiation position of the reference light 51 as follows. In this case, a polarization beam splitter is used instead of the beam splitter 314. Of the detection light 52 irradiated from the main surface 108 side of the hologram recording medium 1, the S-polarized light transmitted through the semi-transmissive film layer 101 is converted into parallel light by the objective lens 323, transmitted through the beam splitter 315a, and beam The light is reflected by the polarization beam splitter used instead of the splitter 314. The reflected light is collected by the condensing lens 324, given astigmatism by the cylindrical lens 325, and enters the servo light receiving element 326. The servo light receiving element 326 detects position information for controlling the irradiation position of the reference light 51 based on this light.

  Next, positioning control of the irradiation position of the object light 50 and the reference light 51 in the present embodiment will be described. When the hologram recording medium 1 is a portable medium, the positions of the focusing control direction and the tracking control direction of the object light 50 and the reference light 51 irradiated on the recording layer 103 are not determined between the recording and reproducing apparatuses. Further, even in the same recording apparatus, when the hologram recording medium 1 is rotated (moved) for recording / reproduction, the focusing control direction of the object light 50 and the reference light 51 irradiated on the recording layer 103 due to surface deflection and eccentricity. In addition, the position in the tracking control direction is shifted.

  In order to prevent this, the tracking control direction is determined by the track detection method, the focus detection method, and the address detection method that are common to optical discs based on the transmitted light or reflected light of the detection light 52 applied to the servo information area 107. Further, a positional shift in the focusing control direction and a position in the in-plane direction orthogonal to the tracking control direction are detected. The tracking control direction can be detected by, for example, the push-pull method, and the focusing control direction can be detected by the astigmatism method, and the in-plane direction orthogonal to the tracking control direction is detected based on the address information configured in the servo information area 107. can do.

  A focus error signal and a track error signal are generated by the signal processing IC 5 based on the return light of the detection light 52 detected by the servo light receiving element 322, and a focusing drive signal and tracking are generated based on the focus error signal and the track error signal. A drive signal is generated. The objective lens 309 is controlled to move in the focusing control direction or the tracking control direction by the operations of the focusing actuator and the tracking actuator based on the focusing drive signal and the tracking drive signal. Thereby, the object light 51 can be irradiated to a desired position. At this time, when the movement amount is large, it is necessary to control the movement of the condenser lens 317 in the optical axis direction and the direction orthogonal to the optical axis in order to accurately form an image on the two-dimensional photodetection array 318. There is also.

  Further, based on the return light of the detection light 52 detected by the servo light receiving element 326, a focusing drive signal and a tracking drive signal are generated. By the operations of the focusing actuator and the tracking actuator based on the focusing drive signal and the tracking drive signal, the deflection unit 315, the hologram conversion element 316, and the objective lens 323 are integrally moved and controlled in the focusing control direction or the tracking control direction. Thereby, the reference beam 52 can be irradiated to a desired position.

  Next, a multiplexing method when data is multiplexed and recorded on the hologram recording medium 1 will be described. There are several types of multiplexing systems. Here, the peritropic multiplexing system and the shift multiplexing system will be described. The peritropic multiplexing method is a method in which a plurality of data is multiplexed and recorded in the same recording area while rotating the reference light within a conical surface having the hologram recording medium 1 as a vertex. The shift multiplexing method is a method of recording data while shifting a data recording area by a minute amount.

  Hereinafter, the peritropic multiplexing method will be described with reference to FIG. For example, when two patterns of different two-dimensional data (for example, data a to data d) are recorded at the same location, four types of different two-dimensional data are sequentially given to the object light. In the figure, 31a to 31d are object lights corresponding to data a to data d, respectively. Reference numerals 32a to 32d are reference lights corresponding to the object lights 31a to 31d, respectively.

  The reference beams 32a to 32d are the points where the optical axis 40 of the objective lens (not shown) for irradiating the object beam and the recording layer of the hologram recording medium 1 intersect (the data is interference fringes around this point). As the apex of the cone). When recording the data a, the object light 31a and the reference light 32a are caused to interfere with each other, the interference fringes are recorded on the recording layer, and when the data b is recorded, the object light 31b and the reference light 32b are caused to interfere with each other. When recording the interference fringes on the recording layer and recording the data c, the object light 31c and the reference light 32c are caused to interfere with each other, the interference fringes are recorded on the recording layer, and the data d is recorded. It is only necessary to cause the light 31d and the reference light 32d to interfere with each other to record interference fringes on the recording layer.

  When data is reproduced, diffracted light corresponding to the data a can be obtained by irradiating the data recording position with the reference light 32a, and if the light is converted into an electrical signal by a two-dimensional photodetector or the like, the original is obtained. 2D data is obtained. Similarly, by irradiating the recording layer with the reference light used at the time of data recording, diffracted light corresponding to each data can be obtained.

  The following [Equation 1] is an expression representing the Bragg angle in peritropic multiplexing. In [Expression 1], L is the thickness of the recording layer of the hologram recording medium 1, λ is the wavelength of light, θr is the incident angle of the reference light to the hologram recording medium 1, and θs is the hologram recording medium 1. Is the angle of incidence of the object light on. For example, if L = 200 (μm), λ = 500 (nm), θr = 50 (deg), and θs = 0 (deg), Δψ to 5.3 (deg). In the case of this condition, the reference light is rotated around the optical axis 40 every 6 °, and 60 (360/6) multiplexing can be performed in the same region.

  Hereinafter, the shift multiplexing method will be described with reference to FIG. The shift multiplexing method is a method of recording data while shifting a data recording area by a minute amount. In order to perform shift multiplexing, it is necessary to make the reference light a spherical wave or make the phase, amplitude, traveling direction, etc. of the reference wave spatially random. It is assumed that each area in which data is recorded in the shift multiplexing method overlaps with other areas.

  A certain area is irradiated with object light 33a (object light corresponding to data a), the object light 33a and reference light 34a are caused to interfere, and a hologram 35a is recorded. Subsequently, after the recording position is shifted by a small amount, the object light 33b (object light corresponding to the data b) is irradiated, the object light 33b and the reference light 34b are caused to interfere, and the hologram 35b is recorded. Thereafter, the data is multiplexed and recorded while sequentially shifting the recording position. When reproducing data, if the position of the recorded hologram 35a is irradiated with the reference light 34a, diffracted light can be obtained only from the hologram 35a recorded at that position by the reference light 34a. Dimension data can be reproduced.

  A combination of the above two types of multiplexing methods, the peritrophic multiplexing method and the shift multiplexing method, enables a large number of multiplexed recordings and realizes a recording / reproducing apparatus capable of recording a large amount of data. can do. When performing data recording by the shift multiplexing method, for example, the spot of the object beam and the reference beam may be shifted in the in-plane direction of the recording surface by the tracking actuator described above.

  Next, a method for making the reference light a non-planar wave will be described. In order to perform shift multiplexing, it is necessary to make the wavefront of the reference light completely random in the light beam or to make it a spherical wave. This is because if there is a correlation between the wavefronts of the reference light before and after the shift of the object light and the reference light, the data recorded in the overlapped area before and after the shift are reproduced simultaneously.

  Hereinafter, a method for converting the reference light into a non-plane wave will be described with reference to FIGS. FIG. 4 shows an example in which means for spatially and randomly converting (modulating) the phase, amplitude, and traveling direction of the reference light are arranged in the optical system in FIG. In the figure, reference numeral 327 denotes a wavefront conversion element having the above function, and is inserted into the optical path of the reference light 51 reflected by the deflection surface 315b. FIG. 5 shows an example of the wavefront conversion element 327. A structure for converting the wavefront is formed in a region 327a of the wavefront conversion element 327 irradiated with the object light and the reference light.

  The black B, gray G, and white W regions irregularly arranged in the region 327a represent optically different regions. The light transmitted (reflected) through the region 327a is converted into light having a spatially random phase. Or each area | region of black B, gray G, and white W represents the area | region from which the transmittance | permeability (reflectance) differs. The light transmitted (reflected) through this region is converted into light having a spatially random amplitude (intensity). Or each area | region of black B, gray G, and white W represents the area | region formed so that an incident angle (reflection angle) may differ with respect to the transmitted (reflected) light. The light transmitted (reflected) through this region is converted into light whose traveling direction is spatially random.

  In this example, each example has been described in three stages of black, gray, and white. However, there are many stages, and the smaller each area, the higher the degree of randomness, such as the phase and amplitude of light, and so on. Crosstalk during playback is reduced.

  FIG. 6 shows an example in which two wavefront conversion means (wavefront conversion element 327 and lens 328) are arranged in the optical system of FIG. In FIG. 6, only a part of the optical system shown in FIG. 3 is shown. By providing means for randomly converting the phase on one surface of the glass plate and providing means for randomly converting the amplitude on the back surface, one glass plate has two wavefront conversion functions. Can have both. Making the wavefront of the reference light a non-planar wave is also effective in multiplex recording by the peritropic multiplex method.

  FIG. 7 shows an example in which the phase, amplitude (intensity), or traveling direction of the reference light is spatially randomly converted by using a hologram, or the reference light is converted from a plane wave to a spherical wave. In FIG. 7, reference numeral 62 denotes a light beam transmitted (reflected) through the wavefront conversion element 327 or light transmitted through the lens. This light beam 62 is light of a spherical wave or light whose phase, amplitude (intensity), or traveling direction is spatially randomly converted. Interference fringes generated by causing the light beam 62 to interfere with the reference light 61 as object light are recorded, and a hologram 63 is produced in the hologram element 316 in FIG. When the hologram 63 is irradiated with the reference light 64 as shown in FIG. 8, a light beam 65 equivalent to the light beam 62 and having the opposite traveling direction is generated (phase conjugate reproduction).

  In order to combine the functions of the hologram, an optical element that spatially and randomly converts the phase and amplitude (intensity) of object light and a light beam 62 that is transmitted (reflected) through a lens are used. Interference fringes generated by causing the light beam 62 and the reference light 61 to interfere with each other are recorded to produce a hologram 63. When the hologram 63 is irradiated with the reference light 64, a composite random light beam 65 equivalent to the light beam 62 and having the opposite traveling direction is generated (phase conjugate reproduction). When the hologram element 12 is mass-produced, it can be mass-produced inexpensively with good reproducibility by transferring the hologram pattern to a mold and further transferring it to glass, resin or the like.

  9 to 15 show configuration examples of the deflecting means 315. FIG. In FIG. 9, a wavefront conversion element 327 is provided instead of the hologram element 316 of FIG. The light reflected by the deflection surface 315 b passes through the wavefront conversion element 327, so that the phase, amplitude (intensity), or traveling direction is spatially randomly converted, and information recording on the hologram recording medium 1 is performed as the reference light 51. The region 106 is irradiated. In FIG. 10, a wavefront conversion element 327 is provided instead of the deflection surface 315b. The light reflected by the beam splitter 315 a is reflected by the wavefront conversion element 327, and the phase, amplitude (intensity), or traveling direction is spatially randomly converted, and the information recording area 106 is irradiated as the reference light 51. .

  In FIG. 11, a flat mirror 329 is provided instead of the beam splitter 315a. The light reflected by the flat mirror 329 is reflected by the wavefront conversion element 327, and the phase, amplitude (intensity), or traveling direction is spatially randomly converted or further converged (diverged) light, and the reference light 51 As shown in FIG. FIG. 12 has the same configuration as FIG. 3, and the light reflected by the deflecting surface 315 b passes through the hologram element 316, so that the phase, amplitude (intensity), traveling direction, or a plurality of these are spatial. The information recording area 106 is irradiated as the reference beam 51 at random.

  In FIG. 13, a flat mirror 329 and a hologram element 316 are provided. The light reflected by the flat mirror 329 is reflected by the hologram element 316. In this light, the phase, amplitude (intensity), traveling direction or a plurality of them are spatially randomly converted, or further converged (diverged) light, and applied to the information recording area 106 as reference light 51. The As shown in FIG. 14, the deflecting unit 315 may be one in which two flat mirrors 329a and 329b are opposed to each other and are integrally held by a holder.

  In the embodiment described above, the object light and the reference light may be irradiated from the same main surface side of the hologram recording medium 1.

  As described above, according to the present embodiment, different recording / reproducing operations are performed by detecting position information using detection light and controlling the irradiation position of object light and reference light on the recording medium based on the position information. Even if there is surface wobbling or eccentricity between apparatuses or recording media, information can be recorded or reproduced at an appropriate recording position in the state of optimal irradiation light on the recording surface. Further, since the control area is irradiated with the detection light without irradiating the information recording area, high-quality recording and reproduction can be performed. Furthermore, the servo signal can be detected regardless of the moving speed of the recording medium.

  Further, by condensing the detection light for detecting the position of the object light with the same objective lens as the object lens for condensing the object light, it is possible to reduce the size and cost of the apparatus. Further, by making the optical axis of the object light incident on the same objective lens non-parallel to the optical axis of the detection light, the object light and the detection light can be irradiated to different areas on the recording surface.

  In addition, position information is detected by detection light for detecting the position of the object light that has passed through the recording medium, and the reference light irradiation position is controlled based on the position information, so that a part of the reference light is referenced. Since it is not necessary to use the detection light for light, the light utilization efficiency of the reference light can be increased.

  Further, by matching the optical axis of the objective lens for objective light (objective lens 309) for condensing the object light with the optical axis of the objective lens (objective lens 323) for condensing the detection light for reference light The position of the reference light, which is positioned with respect to the detection light for reference light, with respect to the object light can always be kept constant.

  Also, by making the optical axis of the objective lens that collects the detection light for reference light and the optical axis of the detection light for reference light non-parallel, the reference surface and the detection light are irradiated on different areas on the recording surface. can do. Therefore, the detection light for reference light does not adversely affect information recording or reproduction.

  Further, there is provided a rotating means (stepping motor or the like) for integrally rotating a light beam deflecting means (deflecting means 315) for deflecting the reference light flux and an objective lens (objective lens 323) for condensing the reference light detection light. As a result, the reference light can be rotated within the conical surface around the optical axis of the object light, and data can be multiplexed and recorded by the peritropic multiplexing method. Furthermore, multiple recording of data can be performed without increasing the size of the apparatus.

  Further, even if the light beam deflecting unit rotates around the optical axis of the object light by causing the reference light to enter the position where the deflection surface (beam splitter 315a) of the light beam deflecting unit intersects the optical axis of the object light, The position of the reference light is not shifted, and the reference light can always be rotated without being decentered around the optical axis of the object light.

  In addition, by providing wavefront conversion means (hologram element 316, wavefront conversion element 327) for converting the reference light into a non-plane wave in the optical path of the reference light, data is multiplexed and recorded by peritropic multiplexing, and shift multiplexing is used. Multiple recording can be performed. Furthermore, by using a hologram as the wavefront conversion means for converting the reference light into a non-planar wave, an optical element that realizes the function of the wavefront conversion means can be manufactured at low cost with good reproducibility.

  Also, at least two of the functions of converting the reference light into a non-plane wave (the function of converting the phase of the reference light, the function of converting the amplitude, the function of converting the traveling direction, and the function of converting the reference light into a spherical wave) By providing an optical element having a function (that realizes at least two functions by combining a single optical element or a combination of a plurality of optical elements) in the optical path of the reference light, the reference light is made more random. Can do. Therefore, the multiplicity by shift multiplexing can be increased. Furthermore, when the optical element that realizes the at least two functions is a hologram, the optical element can be manufactured at low cost with good reproducibility.

  Further, by providing the wavefront conversion unit and the light beam deflection unit as a unit, the movable part can be reduced in size and weight.

  Further, based on the detection result of the position by the detection light for the reference light, the objective lens (objective lens 323) for condensing the detection light for the reference light, the light beam deflecting means, and the wavefront conversion means are integrated into the focusing control direction. By controlling the movement, the irradiation position of the reference light can always be controlled to a desired position even if the recording medium has a surface shake. Further, based on the detection result of the position by the detection light for the reference light, the objective lens that collects the detection light for the reference light, the light beam deflecting means, and the wavefront conversion means are integrally moved and controlled in the tracking control direction. Thus, even if the recording medium has eccentricity or lateral deviation, the irradiation position of the reference light can always be controlled to a desired position. Alternatively, it is possible to always control the irradiation position of the reference light to a desired position even between different recording / reproducing apparatuses. Therefore, high-quality data multiplex recording and reproduction can be performed by the shift multiplex method and the peritropic multiplex method.

  Further, by using the same light source as the light source for the object light, the reference light, and the detection light, it is possible to reduce the size and cost of the apparatus. Furthermore, the object light and the reference light in this embodiment are P-polarized light, and the detection light is S-polarized light. In this way, by making the polarization directions of the object light, the reference light, and the detection light orthogonal to each other, the reproduction light and the detection light can be separated by the polarization optical element, so that detection becomes a noise component of the reproduction light during reproduction. Light can be cut.

  In addition, the data recording capacity can be increased by multiplex recording data by combining the peritropic multiplexing method and the shift multiplexing method.

  As described above, the embodiments of the present invention have been described in detail with reference to the drawings, but the specific configuration is not limited to these embodiments, and includes design changes and the like within a scope not departing from the gist of the present invention. It is.

It is a block diagram which shows the structure of the recording / reproducing apparatus by one Embodiment of this invention. FIG. 2 is a cross-sectional structure diagram showing a cross-sectional structure of a hologram recording medium 1 in the same embodiment. It is a schematic block diagram which shows schematic structure of the optical system with which the optical pick-up 3 by the embodiment is provided. It is a schematic block diagram which shows the other schematic structure of the optical system with which the optical pick-up 3 by the embodiment is provided. FIG. 4 is a reference diagram illustrating an example of means for spatially and randomly converting the phase, amplitude, and traveling direction of reference light in the embodiment. It is a schematic block diagram which shows the other schematic structure of the optical system with which the optical pick-up 3 by the embodiment is provided. FIG. 6 is a reference diagram illustrating a method for producing a hologram 63 that spatially and randomly converts the phase, amplitude, or traveling direction of reference light in the embodiment. FIG. 6 is a reference diagram showing a method of generating random light 65 in which the phase, amplitude, or traveling direction of reference light is spatially random in the embodiment. It is a schematic block diagram which shows the structure of the deflection | deviation means 315 by the embodiment. It is a schematic block diagram which shows the structure of the deflection | deviation means 315 by the embodiment. It is a schematic block diagram which shows the structure of the deflection | deviation means 315 by the embodiment. It is a schematic block diagram which shows the structure of the deflection | deviation means 315 by the embodiment. It is a schematic block diagram which shows the structure of the deflection | deviation means 315 by the embodiment. It is a schematic block diagram which shows the structure of the deflection | deviation means 315 by the embodiment. It is a reference figure for demonstrating the principle of the data recording by a peritropic multiplexing system. It is a reference figure for demonstrating the principle of the data recording by a shift multiplexing system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Hologram recording medium, 2 ... Spindle motor, 3 ... Optical pick-up, 4 ... Feed motor, 5 ... Signal processing IC, 6 ... CPU, 7 ... Driver IC, 31a, 31b, 31c, 31d, 33a, 33b, 50... Object light, 32a, 32b, 32c, 32d, 34a, 34b, 51, 61, 64... Reference light, 35a, 35b, 63. Hologram, 40 ... optical axis, 52 ... detection light, 62, 65 ... luminous flux, 100, 105 ... substrate, 101 ... transmission film layer, 102, 104 ... protective layer, 103 ... Recording layer, 106 ... Information recording area, 107 ... Servo information area, 108, 109 ... Main surface, 301 ... Laser, 302, 328 ... Lens, 303, 314, 315a ... Beam sp , 304, 306, half-wave plate, 305, 308, polarizing beam splitter, 307, spatial light modulator, 309, 323, objective lens, 311, 312, 313 319 ... Deflection prism, 315 ... Deflection means, 315b ... Deflection surface, 316 ... Hologram element, 317, 320, 324 ... Condensing lens, 318 ... Two-dimensional photodetection array, 321, 325... Cylindrical lens, 322, 326... Light receiving element for servo, 327... Wavefront conversion element, 327 a... Region, 329, 329 a, 329 b.

Claims (19)

Based on the diffracted light of the reference light, irradiating the optical recording medium with object light and reference light, recording the information of the object light on the optical recording medium as interference fringes, irradiating the interference light with the reference light In a recording / reproducing apparatus for reproducing information,
The object light is condensed by a first objective lens provided on the first main surface side of the optical recording medium, and the object light is irradiated onto an information recording area on the optical recording medium on which information is recorded. Object light irradiation means;
A reference light irradiating means for irradiating the information recording area from the first or second main surface side;
First detection light for condensing first detection light for position detection by the first objective lens that condenses the object light and irradiating the area different from the information recording area on the optical recording medium Irradiation means;
Control means for controlling an irradiation position of the object light and the reference light based on a detection result of the position by the first detection light;
Comprising
The recording / reproducing apparatus, wherein an optical axis of the object light incident on the first objective lens and an optical axis of the first detection light are non-parallel. A second objective lens provided on the second main surface side for condensing the transmitted light of the first detection light;
The reference light irradiating means irradiates the information recording area from the second main surface side with the reference light,
The control means controls the irradiation position of the object light based on the position detection result of the reflected light of the first detection light, and based on the position detection result of the transmitted light of the first detection light. The recording / reproducing apparatus according to claim 1, wherein an irradiation position of the reference light is controlled. Second detection light for position detection is condensed by a second objective lens provided on the second main surface side, and is irradiated onto a region different from the information recording region on the optical recording medium. Further comprising a detection light irradiation means,
The reference light irradiating means irradiates the information recording area from the second main surface side with the reference light,
The control means controls the irradiation position of the object light based on the position detection result of the reflected light of the first detection light, and based on the position detection result of the reflected light of the second detection light. The recording / reproducing apparatus according to claim 1, wherein an irradiation position of the reference light is controlled.   4. The recording / reproducing apparatus according to claim 2, wherein the optical axes of the first and second objective lenses coincide with each other.   4. The recording / reproducing apparatus according to claim 3, wherein the optical axis of the second detection light incident on the second objective lens and the optical axis of the second objective lens are non-parallel. The reference light irradiating means includes a light beam deflecting means for deflecting the reference light,
3. A rotating means for rotating the second objective lens and the light beam deflecting means integrally around the optical axis of the object light irradiated on the information recording area. The recording / reproducing apparatus according to claim 5. The light beam deflecting unit includes a first light beam deflecting unit and a second light beam deflecting unit,
The first light beam deflecting unit includes a deflecting surface that deflects the reference light, and is disposed at a position that intersects the optical axis of the object light.
The reference light is incident on a position where the deflection surface and the optical axis of the object light intersect,
The recording / reproducing apparatus according to claim 6, wherein the second light beam deflecting unit deflects the reference light deflected by the deflecting surface and irradiates the information recording area.   8. The recording / reproducing apparatus according to claim 1, further comprising a wavefront converting unit that is disposed in an optical path of the reference light and converts the reference light into a non-plane wave.   9. The recording / reproducing apparatus according to claim 8, wherein the wavefront converting unit spatially converts the phase, amplitude, or traveling direction of the reference light.   9. The recording / reproducing apparatus according to claim 8, wherein the wavefront converting unit converts the reference light into a spherical wave.   The recording / reproducing apparatus according to any one of claims 8 to 10, wherein the wavefront conversion means is a hologram.   The wavefront conversion means includes first wavefront conversion means for spatially modulating the phase of the reference light, second wavefront conversion means for spatially modulating the amplitude of the reference light, and the traveling direction of the reference light in space. 9. The recording / reproducing apparatus according to claim 8, further comprising at least two of a third wavefront converting unit that modulates the signal and a fourth wavefront converting unit that converts the reference light into a spherical wave. apparatus.   The wavefront conversion means includes first wavefront conversion means for spatially modulating the phase of the reference light, second wavefront conversion means for spatially modulating the amplitude of the reference light, and the traveling direction of the reference light in space. 3. A hologram having at least two functions among the functions of a third wavefront converting means for modulating optically and a fourth wavefront converting means for converting the reference light into a spherical wave. 9. The recording / reproducing apparatus according to 8.   The recording / reproducing apparatus according to claim 8, wherein the wavefront conversion unit and the light beam deflection unit are provided integrally.   The control means further includes the second objective lens, the light beam deflection means, and the wavefront conversion means based on a position detection result of the transmitted light of the first detection light or the reflected light of the second detection light. 15. The irradiation position of the reference light is controlled by integrally moving the reference light in a direction parallel to the main surface of the optical recording medium. Recording / playback device.   The control means further includes the second objective lens, the light beam deflection means, and the wavefront conversion means based on a position detection result of the transmitted light of the first detection light or the reflected light of the second detection light. 15. The irradiation position of the reference light is controlled by integrally moving the reference light in the normal direction of the main surface of the optical recording medium. Recording / playback device.   The recording / reproducing apparatus according to any one of claims 1 to 16, wherein the object light, the reference light, and the detection light are generated by the same light source.   18. The recording / reproducing apparatus according to claim 1, wherein a polarization direction of the object light and the reference light and a polarization direction of the detection light are orthogonal to each other. 19. The multiplex recording method for recording a plurality of information on the object light in the same area of the optical recording medium, wherein a peritropic multiplex method and a shift multiplex method are combined. The recording / reproducing apparatus according to the section.

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