JP6136520B2 - Optical information recording device - Google Patents

Description

  The present invention relates to an optical information recording apparatus, an optical information recording method, an optical information reproducing apparatus, an optical information reproducing method, and an optical element.

  Conventionally, holographic recording using a hologram has been proposed as one method for optically recording and reproducing information. Holographic recording is a technique for recording information on an information recording medium as a hologram using interference of light. Therefore, according to holographic recording, information can be recorded three-dimensionally as a three-dimensional (3D) refractive index distribution in an information recording medium. Therefore, in holographic recording, a larger amount of information can be recorded by effectively utilizing the thickness of the information recording medium.

  More specifically, in holographic recording, information light is recorded on an information recording medium as a hologram by irradiating the information recording medium with signal light having information and reference light that interfere with each other. This is an optical information recording / reproducing system in which reproduction light having information is reproduced by irradiating the information recording medium with light.

  Furthermore, polarization holographic recording has been proposed as an application of holographic recording (see, for example, Patent Document 1, Non-Patent Document 1, and Non-Patent Document 2). Polarization holographic recording is recording that forms a hologram having polarization characteristics.

  More specifically, in polarization holographic recording, signal light and reference light having an arbitrary polarization state are irradiated onto an information recording medium having polarization sensitivity. In this case, in the information recording medium having polarization sensitivity, optical anisotropy corresponding to the polarization is induced, and information is recorded as a polarization hologram. The recorded information is reproduced by irradiating the information recording medium with reference light or signal light in the same manner as in normal holographic recording. In other words, polarization holographic recording utilizes the property of a light vector wave having the degree of freedom of polarization orientation (vibration orientation of electromagnetic field), and records information on an information recording medium as a 3D birefringence distribution. It is.

  In holographic recording in which information is recorded on an information recording medium having no polarization sensitivity, the polarization states of the signal light and the reference light must be the same. In contrast, in polarization holographic recording, information can be recorded using signal light and reference light whose polarization states are not the same.

JP 2013-37751 A

Takanori Ochiai et al., "Angular multiplex recording of data pages by dual-channel polarization holography", OPTICS LETTERS / Vol. 38, No. 5 / March 1, 2013, p748-750 Daisuke Barada et al., "Dual-channel polarization holography: a technique for recording two complex amplitude components of a vector wave", Optics Letters, Vol. 37, Issue 21, pp. 4528-4530 (2012)

  In the information recording apparatus and information reproducing apparatus of the holographic recording method and the polarization holographic method, the simplification of the device and the reduction of the size are problems for practical use.

  Therefore, the present invention provides an optical information recording apparatus, an optical information recording method, an optical information reproducing apparatus, an optical information recording apparatus that can record or reproduce information with a simpler configuration using holographic recording or polarization holographic recording. An object is to provide an information reproducing method and an optical element.

An optical information recording apparatus according to an embodiment of the present invention includes an irradiation light generation system and an irradiation system. The irradiation light generation system generates signal light having a polarization component in which information is recorded by spatial modulation of at least one of phase and amplitude as light divided by + 1st order diffracted light, −1st order diffracted light, or a birefringent prism. On the other hand, the reference light is generated as zero-order light corresponding to the + 1st order diffracted light and the −1st order diffracted light or as another light divided by the prism. The irradiation system records the information on the recording medium as a three-dimensional optical anisotropy distribution by irradiating the recording medium having photosensitivity with the signal light and the reference light.
An optical information reproducing apparatus according to an embodiment of the present invention includes an irradiation light generation system, an irradiation system, an imaging system, and an information reproduction system. The irradiation light generation system generates reference light. The irradiation system irradiates the reference light onto a recording medium having photosensitivity and having information recorded as a three-dimensional optical anisotropy distribution. The imaging system is signal light generated as light corresponding to light divided by the reference light from the recording medium by a + 1st order diffracted light, a −1st order diffracted light, or a birefringent prism, and has a phase and amplitude. Corresponding to the signal light having the polarization component in which the information is recorded as at least one spatial modulation, the 0th order light corresponding to the + 1st order diffracted light and the −1st order diffracted light, or another light divided by the prism Imaging is performed in a state where the reference light generated as light is superimposed. The information reproducing system reproduces the information based on the imaged signal light.
In addition, the optical information recording method according to the embodiment of the present invention converts signal light having a polarization component in which information is recorded by spatial modulation of at least one of phase and amplitude into + 1st order diffracted light, −1st order diffracted light, or birefringence. Generating reference light as zero-order light corresponding to the + 1st order diffracted light and the −1st order diffracted light or another light divided by the prism, Irradiating the recording medium with the signal light and the reference light to record the information on the recording medium as a three-dimensional optical anisotropy distribution.
An optical information reproducing method according to an embodiment of the present invention includes a step of generating reference light, and the reference light is applied to a recording medium that has photosensitivity and has information recorded as a three-dimensional optical anisotropy distribution. A signal light generated as light corresponding to light divided by the reference light by a + 1st order diffracted light, a −1st order diffracted light, or a birefringent prism from the recording medium, and having a phase and an amplitude Corresponding to the signal light having the polarization component in which the information is recorded as at least one of the spatial modulation, the 0th order light corresponding to the + 1st order diffracted light and the −1st order diffracted light, or another light separated by the prism Imaging the reference light generated as the light to be superimposed and regenerating the information based on the captured signal light.
An optical element according to an embodiment of the present invention has a plurality of variable diffraction gratings arranged two-dimensionally, and the transmittance of each variable diffraction grating is inclined with respect to the arrangement direction of the plurality of variable diffraction gratings. It is configured to change to the specific direction according to the incident polarized light.
An optical element according to an embodiment of the present invention includes a first electrode, a plurality of second electrodes, and a liquid crystal layer. The plurality of second electrodes are arranged two-dimensionally. Liquid crystal layer, wherein the first electrode is disposed between the plurality of second electrodes, the according to the incident polarization particular a particular direction inclined with respect to the arrangement direction of the second electrode In this direction, the thickness periodically changes at a period corresponding to each width of the plurality of second electrodes.

  According to the optical information recording apparatus, the optical information recording method, the optical information reproducing apparatus, the optical information reproducing method, and the optical element according to the embodiment of the present invention, a simpler configuration using holographic recording or polarization holographic recording Information can be recorded or reproduced.

1 is a configuration diagram of an optical information recording / reproducing apparatus according to a first embodiment of the present invention. FIG. The figure which looked at 2nd SF shown in FIG. 1 from the advancing direction of light. The figure which shows the modification of 2nd SF which looked at 2nd SF shown in FIG. 1 from the advancing direction of light. The figure which shows an example of the 2D image information encoded in the 2D encoding part shown in FIG. The figure which shows another example of 2D image information encoded in the 2D encoding part shown in FIG. FIG. 2 is a top view showing reference light and signal light generated in a first SLM when information is recorded on an information recording medium by the optical information recording / reproducing apparatus shown in FIG. 1. The front view which looked at the reference light and signal light which are shown in FIG. 6 from the direction perpendicular | vertical to the entrance plane of 2nd SLM. The front view which looked at 2nd SF shown in FIG. 7 from the advancing direction of light. FIG. 3 is a top view showing reference light and signal light generated in a second SLM when information is recorded on an information recording medium by the optical information recording / reproducing apparatus shown in FIG. 1. FIG. 10 is a front view of the reference light and the signal light shown in FIG. 9 viewed from a direction perpendicular to the incident surface of the second SLM. The front view which looked at 2nd SF shown in FIG. 10 from the advancing direction of light. FIG. 3 is a top view showing reference light generated in the first SLM and reproduced signal light when information recorded on an information recording medium is reproduced by the optical information recording / reproducing apparatus shown in FIG. 1. The front view which looked at the reference light and reproduction | regeneration signal light which are shown in FIG. 12 from the direction perpendicular | vertical to the entrance plane of 2nd SLM. The front view which looked at 2nd SF shown in FIG. 13 from the advancing direction of light. FIG. 3 is a top view showing reference light generated in a second SLM and signal light to be reproduced when information recorded in information on an information recording medium is reproduced by the optical information recording / reproducing apparatus shown in FIG. 1. The front view which looked at the reference light shown in FIG. 15, and the signal light to reproduce | regenerate from the direction perpendicular | vertical to the entrance plane of 2nd SLM. The front view which looked at 2nd SF shown in FIG. 16 from the advancing direction of light. FIG. 4 is a front view of the second SF viewed from the traveling direction of light when reproducing the information recorded on the information recording medium when the second SF having the structure shown in FIG. 3 is used. The front view which shows the structure of the variable diffraction grating array used for the spatial modulation system of the optical information recording / reproducing apparatus concerning the 2nd Embodiment of this invention. FIG. 20 is a cross-sectional view of the variable diffraction grating array shown in FIG. 19. The perspective view of the 1st alignment film shown in FIG. The figure which shows the modification of VGA shown in FIG. The figure which shows the structure of the spatial modulation system with which the optical information recording / reproducing apparatus which concerns on the 3rd Embodiment of this invention is equipped. The figure which shows the structure of the spatial modulation system with which the optical information recording / reproducing apparatus which concerns on the 4th Embodiment of this invention is equipped. The block diagram which shows the modification of the spatial modulation system shown in FIG. The figure which shows the structure of the spatial modulation system with which the optical information recording / reproducing apparatus which concerns on the 5th Embodiment of this invention is equipped. The figure which shows the structure of the spatial modulation system with which the optical information recording / reproducing apparatus which concerns on the 6th Embodiment of this invention is equipped. The figure which shows the structure of the spatial modulation system with which the optical information recording / reproducing apparatus which concerns on the 7th Embodiment of this invention is equipped.

  An optical information recording apparatus, an optical information recording method, an optical information reproducing apparatus, an optical information reproducing method, and an optical element according to embodiments of the present invention will be described with reference to the accompanying drawings.

(First embodiment)
(Configuration and function)
FIG. 1 is a block diagram of an optical information recording / reproducing apparatus according to the first embodiment of the present invention.

  The optical information recording / reproducing apparatus 1 is an apparatus that records information on an information recording medium 2 having photosensitivity using holographic recording or polarization holographic recording, and reproduces the recorded information. That is, the optical information recording / reproducing apparatus 1 uses an optical information recording apparatus for recording information on an information recording medium 2 having photosensitivity using holographic recording or polarization holographic recording, and performs holographic recording or polarization holographic recording. This is an apparatus that also serves as an optical information reproducing apparatus that reproduces information recorded on the information recording medium 2 having photosensitivity.

  FIG. 1 shows an optical information recording / reproducing apparatus 1 that can both record and reproduce information. However, an optical information recording apparatus that performs only information recording is manufactured as a recorder, or conversely, only information reproduction is performed. An optical information reproducing apparatus that performs the above can also be manufactured as a player. The information recording medium 2 can be incorporated as a component of the optical information recording / reproducing apparatus 1, the optical information recording apparatus, or the optical information reproducing apparatus. The optical information recording device or the optical information reproducing device may be replaced without being a constituent element.

  An optical information recording / reproducing apparatus 1 shown in FIG. 1 includes an irradiation light generation system 3, an irradiation system 4, an imaging system 5, and an information reproduction system 6.

The irradiation light generation system 3 is an optical system for generating the signal light L _S and the reference light L _R having a polarization component in which information is recorded. In particular, the irradiation light generation system 3 records information on the polarization component of the signal light L _S as an optical complex signal by spatial modulation of at least one of phase and amplitude, that is, spatial modulation of complex amplitude, and the signal light L _S While generating as + 1st order diffracted light or −1st order diffracted light, the reference light L _R is generated as 0th order light corresponding to the + 1st order diffracted light and −1st order diffracted light. Hereinafter, a case where the signal light L _S is generated as + 1st order diffracted light will be described as an example. The irradiation light generation system 3 also serves as an optical system for generating a reference beam L _R emitted for reproducing information recorded on the information recording medium 2.

The irradiation system 4 is an optical system that records information on the information recording medium 2 as a 3D optical anisotropy distribution by irradiating the photosensitive information recording medium 2 with the signal light L _S and the reference light L _R when recording information. Functions as a system. In particular, the illumination system 4, when the reference light L _R for reproducing information is irradiated on the information recording medium 2, the signal light L _S and the information recording medium is reproduced from the information recording medium 2 +1 order diffracted light 2 and the reference beam L _R for reproduction of the transmitted information, so as to overlap the imaging element without passing through the optical element, +1 as a signal light L _S and 0-order beam generated order diffracted light for recording of information It is configured to irradiate the generated reference light L _R on the information recording medium 2. On the other hand, at the time of reproducing information, the irradiation system 4 functions as an optical system that irradiates the information recording medium 2 having photosensitivity and recorded information as a 3D optical anisotropy distribution with reference light.

State imaging system 5, the signal light L _S occurring as from the information recording medium 2 + 1st-order diffracted light when irradiated with the reference light L _R, superimposed with the reference beam L _R that occurs as a 0-order light corresponding to + 1-order diffracted light This is a system for imaging. In other words, the imaging system 5, two-dimensional interference fringes between the signal light L _S and the reference light L _R having a polarization component information as at least one of the spatial modulation of phase and amplitude were recorded: as (2D two dimensional) image It is configured to shoot. Therefore, it is not always necessary to dispose an optical element between the image pickup element provided in the image pickup system 5 and the information recording medium 2. That is, through the signal light L _S occurring as from the information recording medium 2 + 1st-order diffracted light, the reference light L _R that occurs as a 0-order light corresponding to + 1-order diffracted light, without passing through the optical element, or the required optical elements Then, an image is picked up by the image pickup device provided in the image pickup system 5.

The information reproduction system 6 is a system that reproduces information based on the signal light L _S imaged by the imaging system 5. Since the signal light L _S is imaged as a combined light with the reference light L _R , the signal light L _S is extracted in the information reproduction system 6. Then, the information recorded in the signal light L _S is reproduced in the information reproduction system 6.

  FIG. 1 shows an arrangement example of components such as an optical element for constituting the irradiation light generation system 3, the irradiation system 4, the imaging system 5, and the information reproduction system 6 as described above. In FIG. 1, an optical path indicated by a solid line indicates an optical path of 0th order light, an optical path indicated by an alternate long and short dash line indicates an optical path of + 1st order diffracted light, and an optical path indicated by a dotted line indicates an optical path of −1st order diffracted light.

  The irradiation light generation system 3 includes a laser light source 7, a half-wave plate (HWP) 8, a first collimator lens 9, a first spatial filter (SF) 10, and a second collimator. Lens 11, first mirror 12, second mirror 13, polarizing beam splitter (PBS) 14, first spatial light modulator (SLM) 15, second SLM 16, third The collimator lens 17, the second SF 18, and the information input system 19 can be arranged and configured as shown. An optical element such as a compensation plate or a Faraday rotator having a function of adjusting the polarization state may be disposed between the PBS 14 and the first SLM 15 and between the PBS 14 and the second SLM 16.

  The laser light source 7 is a light source that outputs linearly polarized light. Accordingly, the polarization direction of the linearly polarized light output from the laser light source 7 rotates in the direction other than the 0 degree direction or the 90 degree direction with the transmission axis of the PBS 14 being 0 degrees in the half-wave plate 8. In other words, in the half-wave plate 8, 45-degree linearly polarized light other than s (senkrecht) polarized light whose electric field component vibration direction is perpendicular to the incident surface or p (parallel) polarized light whose electric field component vibration direction is parallel to the incident surface. Any linearly polarized light is generated.

  The linearly polarized light whose beam diameter is expanded by a beam expander (BE) formed by the first collimator lens 9, the first SF 10 and the second collimator lens 11 is converted into the first mirror 12 and the second mirror 12. The light is reflected by the two mirrors 13 and enters the PBS 14 in a three-dimensional oblique direction. That is, linearly polarized light such as 45 degree linearly polarized light having a polarization orientation other than the 0 degree direction and the 90 degree direction is incident on the PBS 14 while being inclined in the direction penetrating the paper surface of FIG.

The polarized light incident on the PBS 14 can be any polarized light such as circularly polarized light or elliptically polarized light as long as it is polarized light other than p-polarized light and s-polarized light. In other words, the PBS 14, can be incident arbitrary polarization, including at least the s-polarized light component and p-polarized light component as the incident light L _IN. It is also possible to impart spatial distribution to the incident light L _IN to be incident on PBS 14. In that case, an optical element necessary for generating incident light L _IN such as circularly polarized light or elliptically polarized light and making it incident on the PBS 14 and an optical element for imparting a spatial distribution to the incident light L _IN on the PBS 14 include: Arranged in the irradiation light generation system 3.

  For this reason, the polarized light including the s-polarized component and the p-polarized component incident on the PBS 14 is separated into s-polarized light and p-polarized light.

  The s-polarized light reflected by the PBS 14 is incident on the first SLM 15 in an oblique direction. In the first SLM 15, the polarization state of the s-polarized light changes according to the intensity of the input signal for each 2D space position corresponding to the 2D pixel position.

  For example, if the first SLM 15 is an SLM in which liquid crystal is oriented in a 45 degree direction, and the polarization direction of linearly polarized light incident on the first SLM 15 is 0 degree, the voltage applied to each position of the first SLM 15 Is increased from 0 degree linearly polarized light to 0 degree elliptically polarized light, from 0 degree elliptically polarized light to circularly polarized light, from circularly polarized light to 90 degree elliptically polarized light, and from 90 degree elliptically polarized light to 90 degree linearly polarized light at the corresponding positions. The polarization state of polarized light changes.

  In addition, an input signal is input to the first SLM 15 such that a striped intensity distribution is generated for each unit region in the incident linearly polarized reflected light. Accordingly, diffraction occurs in each unit region in the first SLM 15, and 0th-order diffracted light, + 1st-order diffracted light, and −1st-order diffracted light are generated from each unit region of the first SLM15. In other words, the first SLM 15 is controlled so that the diffraction in the first SLM 15 generates the 0th-order diffracted light, the + 1st-order diffracted light, and the −1st-order diffracted light for each unit region. Further, the tilt angle of the polarized light incident on the PBS 14 is also determined so that the 0th-order diffracted light, the + 1st-order diffracted light, and the −1st-order diffracted light are generated by the diffraction in the first SLM 15.

  The amplitudes of the + 1st order diffracted light and the −1st order diffracted light generated from one unit region change according to the height difference of the striped intensity distribution in the unit region. Specifically, the intensity of the diffracted light increases as the height difference of the striped intensity distribution increases, and the intensity of the diffracted light decreases as the height difference of the striped intensity distribution decreases. In addition, the phase of the + 1st order diffracted light and the −1st order diffracted light generated from one unit region varies depending on the position of the striped intensity distribution.

  Therefore, the amplitude and phase of the zero-order light and the diffracted light can be modulated by controlling the voltage applied to each pixel position of the first SLM 15. That is, the amplitude of the diffracted light is modulated by the difference in level of the voltage applied in the unit region of the first SLM 15, and the zero-order light and the diffraction are determined by the voltage pattern applied in the unit region of the first SLM 15. The phase of light can be modulated.

  Therefore, by controlling the voltage applied to each position of the first SLM 15, the 0th-order diffracted light, the + 1st-order diffracted light, and the −1th order reflected by the first SLM15 and transmitted through the PBS 14 as the p-polarized component according to the polarization state. The amplitude and phase of the next diffracted light can be modulated. That is, the PBS 14 outputs 0th-order diffracted light, + 1st-order diffracted light, and −1st-order diffracted light, whose complex amplitudes are spatially modulated in accordance with an input signal to the first SLM 15, as p-polarized light.

  On the other hand, the p-polarized light transmitted through the PBS 14 is incident on the second SLM 16 in an oblique direction. Also in the second SLM 16, the polarization state of the p-polarized light changes according to the intensity of the input signal for each 2D space position corresponding to the 2D pixel position. Similarly to the first SLM 15, the applied voltage to the second SLM 16 is controlled so that the second SLM 16 also generates 0th-order diffracted light, + 1st-order diffracted light, and −1st-order diffracted light for each unit region in the second SLM16. The

  Then, the complex amplitudes of the 0th-order diffracted light, the + 1st-order diffracted light, and the −1st-order diffracted light reflected by the second SLM 16 and reflected by the PBS 14 as the p-polarized component according to the polarization state are spatially modulated. That is, the PBS 14 outputs 0th-order diffracted light, + 1st-order diffracted light, and −1st-order diffracted light, whose complex amplitudes are spatially modulated in accordance with the input signal to the second SLM 16, as s-polarized light.

  P-polarized 0th-order diffracted light, + 1st-order diffracted light and -1st-order diffracted light whose complex amplitude is spatially modulated in the first SLM 15, and s-polarized 0th-order diffracted light whose complex amplitude is spatially modulated in the second SLM 16 The folded light and the −1st order diffracted light are narrowed down by the third collimator lens 17 and enter the second SF 18.

  However, the p-polarized + 1st order diffracted light whose complex amplitude is spatially modulated in the first SLM 15 and the s-polarized + 1st order diffracted light whose complex amplitude is spatially modulated in the second SLM 16 are combined with each other in the second state. Each optical element constituting the irradiation light generation system 3 is arranged so as to be incident on the SF 18. Therefore, a vector wave including p-polarized + 1st order diffracted light and s-polarized + 1st order diffracted light as components is incident on the second SF 18.

  FIG. 2 is a view of the second SF 18 shown in FIG. 1 as viewed from the traveling direction of light.

  As shown in FIG. 2, the second SF 18 can be configured by providing three rectangular holes for allowing the vector waves of the p-polarized 0th-order diffracted light, the s-polarized 0th-order diffracted light, and the + 1st-order diffracted light to pass through. .

  FIG. 3 is a view showing a modification of the second SF 18 when the second SF 18 shown in FIG. 1 is viewed from the light traveling direction.

  FIGS. 1 and 2 show an example in which p-polarized + 1st order diffracted light and s-polarized + 1st order diffracted light are superimposed on each other. May be generated separately. In that case, the optical element of the irradiation light generation system 3 is arranged so that the p-polarized + 1st-order diffracted light and the s-polarized + 1st-order diffracted light pass through different optical paths.

  When p-polarized + 1st-order diffracted light and s-polarized + 1st-order diffracted light are generated separately, as shown in FIG. 3, p-polarized 0th-order diffracted light, s-polarized 0th-order diffracted light, p-polarized + 1st-order diffracted light In addition, the second SF 18 can be configured by providing four rectangular holes for allowing the + 1st order diffracted light of s-polarized light to pass therethrough.

  Of course, the second SF 18 may be configured by providing a hole having an arbitrary shape such as a circle instead of the rectangular hole, or by providing a common hole.

  The second SF 18 having such a structure blocks p-polarized −1st order diffracted light and s-polarized light and −1st order diffracted light. When the information recording medium 2 having polarization sensitivity is used for polarization holographic recording, only one of the p-polarized 0th-order diffracted light and the s-polarized 0th-order diffracted light passes through the second SF 18. You may do it.

The vector wave of + 1st order diffracted light that has passed through the second SF 18 is used as the signal light L _S. Further, 0-order diffracted light of p-polarized light is used as reference light L _R for p-polarized light component contained in the signal light L _S, 0-order diffracted light of the s-polarized light, for s-polarized light component contained in the signal light L _S used as the reference light L _R. When the information recording medium 2 having polarization sensitivity is used, any one of the p-polarized 0th-order diffracted light and the s-polarized 0th-order diffracted light is a p-polarized component and an s-polarized component included in the signal light L _S. Are used as both reference lights.

Spatial modulation of the complex amplitude of the p-polarized component and spatial modulation of the complex amplitude of the s-polarized component included in the signal light L _S that is a vector wave can be performed independently of each other. That is, the input signal to the first SLM 15 and the input signal to the second SLM 16 can be generated independently of each other. Therefore, information on two channels can be recorded in the signal light L _S.

  The information input system 19 converts information to be recorded on the information recording medium 2 into a 2-channel 2D image signal, and inputs the 2-channel input signal corresponding to the converted 2D image signal to the first SLM 15 and the second SLM 16. Each is a system to input. For this purpose, the information input system 19 includes an information processing device 22 to which a first input device 20 and a first display device 21 are connected.

  The information processing apparatus 22 is a computer that functions as the information acquisition unit 23 and the 2D encoding unit 24 by executing a program. A circuit may be used to configure the information input system 19.

  The information acquisition unit 23 has a function of acquiring information to be recorded on the information recording medium 2 via a network or from a desired storage in accordance with instruction information from the first input device 20. The information recording medium 2 can record all kinds of information that can be output as digital signals such as audio and text document data, in addition to images such as moving images and still images.

  The 2D encoding unit 24 uses the information corresponding to the 2D spatial positions of the first SLM 15 and the second SLM 16 to obtain the information acquired by the information acquisition unit 23 according to the instruction information from the first input device 20. The first SLM 15 and the second SLM 16 are controlled according to the converted two pieces of 2D image information. Specifically, the 2D encoding unit 24 is configured to individually apply a voltage distribution corresponding to the pixel value at each position constituting the 2D image information to the first SLM 15 and the second SLM 16.

  FIG. 4 is a diagram illustrating an example of 2D image information encoded by the 2D encoding unit 24 illustrated in FIG. 1.

  If the information to be recorded on the information recording medium 2 is digital information, it can be expressed as binary data examples of 0 and 1 regardless of the type of information. The information expressed in binary numbers can be expressed as 2D image information having a plurality of white and black binary pixels as shown in FIG. A specific method for converting information into a binary image as shown in FIG. 4A is described in Japanese Patent Laid-Open No. 2013-37751.

  The binary image information shown in FIG. 4A can be further converted into grayscale image information having multi-valued pixel values as shown in FIG. Specifically, each binary pixel constituting the black and white image information can be expressed by a plurality of pixel regions that periodically change between multi-values in which the pixel value is three or more. In the illustrated example, each pixel constituting a 16 × 16 pixel binary image is represented by 4 × 4 pixels having three more pixel values. That is, a 16 × 16 pixel binary image is converted into a 64 × 64 pixel multivalued image representing 0 and 1 in units of 4 × 4 pixels.

  As shown in FIG. 4B, 2D image information is generated by encoding a plurality of pixel regions whose pixel values periodically change as unit regions, and a voltage corresponding to the pixel value of the 2D image information is set to the first SLM 15. Diffracted light whose amplitude is modulated for each unit region in the first SLM 15 can be generated. In other words, each unit region of the 2D image information is expressed by a pixel value having a regular striped intensity distribution so that diffracted light whose amplitude is modulated for each unit region is generated in the first SLM 15. Can do.

  Note that the change direction of the pixel value in each unit region is the diffraction direction, that is, the direction in which the + 1st order diffracted light and the −1st order diffracted light are generated with respect to the 0th order light. Therefore, the change direction of the pixel value in the unit region is determined in a direction in which the + 1st order diffracted light and the −1st order diffracted light are generated in the first SLM 15. The change direction of the pixel value in the unit region, that is, the direction in which the + 1st order diffracted light and the −1st order diffracted light are generated can be arbitrarily determined, but it is efficient to incline in the direction of ± 45 degrees with respect to the pixel array direction. Is.

  In the example shown in FIG. 4B, the stripe-shaped intensity distribution pattern is the same in all unit regions that generate diffracted light. Therefore, when the first SLM 15 is controlled in accordance with the 2D image information shown in FIG. 4B, diffracted light having a spatially modulated amplitude is generated from the first SLM 15.

As a result, it becomes possible to generate signal light L _{S in} which binary image information as shown in FIG. 4A is recorded as amplitude spatial modulation as + 1st order diffracted light. In addition, it is possible to generate the reference light L _R for reproducing the signal light L _S as 0-order diffracted light. In other words, interference of spatially modulated reflected light from a plurality of pixel regions as units such as 4 × 4 pixels of the first SLM 15, and PBS + 1 as a polarizer and + 1st order diffracted light whose complex amplitude is spatially modulated by PBS14 and 0 Next-order diffracted light can be generated.

  The same applies to the second SLM 16. However, the direction of diffracted light generated in the second SLM 16 is orthogonal to the direction of diffracted light generated in the first SLM 15. Accordingly, the stripe-shaped change direction of the pixel value in the unit area of the 2D image information used for controlling the voltage applied to the second SLM 16 is orthogonal to the change direction corresponding to the first SLM 15. That is, in the 2D image information generated as the control information of the first SLM 15 and the second SLM 16, the direction in which the pixel value regularly changes in the unit region is the generation direction of the + 1st order diffracted light and the −1st order diffracted light. The corresponding direction.

Thus, in order to record the information to be recorded on the information recording medium 2 once as a binary image as shown in FIG. 4A and record the binary image on the signal light L _S , FIG. Can be output to the first SLM 15 and the second SLM 16, respectively. By encoding such information into a 2D image, the information transfer rate can be improved.

  FIG. 5 is a diagram illustrating another example of the 2D image information encoded by the 2D encoding unit 24 illustrated in FIG. 1.

  Information to be recorded on the information recording medium 2 is not limited to a binary image, but can be expressed as a multi-valued image. FIG. 5A shows an example in which information to be recorded on the information recording medium 2 is converted into a 4-frame multi-value image. Each multi-value image is composed of 16 × 16 pixels, and each pixel can take four values of 1.5, 0.5, −0.5, and −1.5 as relative pixel values.

Then, the four-frame multi-value image is transformed into the real part of the p-polarized component, the imaginary part of the p-polarized component, the real part of the s-polarized component and the imaginary part of the s-polarized component. It can be recorded as a spatial modulation of the real part and the imaginary part. In this case, + 1 a 2D image information shown in FIG. 5 (A) to the polarization component of the signal light L _S of the order diffracted light was recorded, and 0 first SLM15 and second to generate a reference light L _R order diffracted light The control signal to be output to the second SLM 16 is a signal corresponding to a 2D multi-value image of 64 × 64 pixels as shown in FIG.

When such information is coded, 4 frames × 4 amplitude values = 16 kinds of information can be recorded in one unit area of the signal light L _S. For this reason, it is possible to increase the density of information. Specifically, the amount of information that can be recorded can be quadrupled compared to the case where a black and white binary image is recorded on the signal light L _S.

The transmittance T (x, y) of incident polarized light at the position (x, y) of the first SLM 15 and the second SLM 16 can be expressed by Expression (1).
However, in Expression (1), U _S is the complex amplitude of each polarization component of the signal light L _S , and U _R is the reference light L _R that satisfies the relationship | U _S | ≦ | U _R | corresponding to each polarization component. The complex amplitudes of * and * are conjugate complex numbers, respectively.

Moreover, the complex amplitude U _S of each polarization component of the signal light L _S in the formula (1) is represented by the formula (2) using the amplitude A _S and phase phi _S.
U _S = A _S exp (iφ _S ) = Re (U _S ) + Im (U _S ) (2)

Furthermore, complex amplitude U _R of the reference light L _R in the formula (1) can be represented by the formula (3-1) with an amplitude A _R and the constant k _x, a k _y. Note that φ _R is the phase of the reference light L _R. In addition, the constants k _x and k _{y satisfy} the relations of equations (3-2) and (3-3) using arbitrary integers n _x and n _y and arbitrary positive integers N _x and N _y , respectively. To be decided.
U _R = A _R exp (iφ _R ) = A _R exp {i (k _x x + k _y y)} (3-1)
k _x = 2n _x π / N _x (3-2)
k _y = 2n _y π / N _y (3-3)

  Therefore, each control signal to be output to the first SLM 15 and the second SLM 16 and each 2D image information for generating each control signal are determined by the equations (1), (2), and (3). Can do.

That is, to be generated in accordance with information to be recorded from the equation (2), the real part and the imaginary part can be determined complex amplitude U _S of each polarization component of the spatial modulated signal light L _S. On the other hand, the formula (3-1), can be the reference light L _R determined by determining the amplitude A _R and the constant k _x, k _y in the formula (3-2) and (3-3). Then, the voltage to be applied to each position (x, y) of the first SLM 15 and the second SLM 16 can be obtained by the equation (1).

However, it is desirable to make the absolute values of the two constants k _x and k _y equal. This is because the pixel positions in the x-axis direction and the y-axis direction in the first SLM 15 and the second SLM 16 have a square lattice shape. The amplitude A _R of the reference light L _R is, | U _S | ≦ | like the relationship is satisfied, the absolute value of the complex amplitude U _S of the signal light _{L S | | U R U S} | maximum or more If so, an arbitrary value can be set.

  When the control signals to be output to the first SLM 15 and the second SLM 16 are determined by the equations (1), (2), and (3), the first SLM 15 and the second SLM 16 have + 1st order diffracted light and A striped light pattern whose intensity changes with an integer period in the generation direction of the −1st order diffracted light can be formed in a unit region composed of a plurality of pixels. Accordingly, the first SLM 15 and the second SLM 16 can generate the + 1st order diffracted light and the −1st order diffracted light, respectively. In other words, the intensity of the expressions (1), (2), and (3) is changed by the first SLM 15 and the second SLM 16 with an integer period in the generation direction of the + 1st order diffracted light and the −1st order diffracted light, respectively. It is a formula showing the conditions for forming the pattern of the striped light which does in a unit area.

By such calculation, the voltage distribution to be input to the first SLM 15 and the second SLM 16 in order to generate the signal light L _S having the target complex amplitude U _S as the + 1st order diffracted light can be obtained.

That is, the information to be recorded on the information recording medium 2 is an image in which a plurality of two-dimensional pixel regions whose pixel values regularly change in the direction corresponding to the generation direction of the + 1st order diffracted light and the −1st order diffracted light. Can be converted into information. Then, the polarization state of the polarized light incident in the direction corresponding to the generation direction of the + 1st order diffracted light and the −1st order diffracted light can be spatially modulated by the modulation amount corresponding to the pixel value of the image information. Further, the diffracted light whose phase and amplitude are spatially modulated thereby passes through the PBS 14 which is a polarizer, so that the signal light L _S and the reference light L _R whose complex amplitude is spatially modulated can be generated. In addition, information can be recorded in each polarization component of the signal light L _S as coded binary image information or multi-valued image information of three or more values.

That is, in the irradiation light generation system 3, a space in which the complex amplitude spatial modulation is independently performed on the p-polarized component and the s-polarized component of the vector wave by the PBS 14, the first SLM 15, the second SLM 16, and the information input system 19. A modulation system is formed. The incident light L _IN that is incident on the spatial modulation system by the laser light source 7, the HWP 8, the first collimator lens 9, the first SF 10, the second collimator lens 11, the first mirror 12, and the second mirror 13. Is formed.

The reference light L _R and the signal light L _S generated in the irradiation light generation system 3 having such a configuration are output to the irradiation system 4. That is, the signal vector wave as + 1st-order diffracted light including p-polarized light component and s-polarized light component, p-polarized reference light 0 order diffracted light of the light component L _R and s 0 reference light L _R of the order diffracted light for the polarization component The light enters the irradiation system 4 in a separated state.

  The irradiation system 4 can be configured by disposing the fourth collimator lens 25 and the fifth collimator lens 26 so as to face each other. Moreover, the imaging system 5 can be comprised with a single imaging device. In the illustrated example, the imaging system 5 is configured by a single photo detector (PD) 27.

  The photosensitive information recording medium 2 is disposed between the irradiation system 4 and the PD 27 that is the imaging system 5. Of the information recording medium 2 having photosensitivity, a photopolymerizable polymer material or the like is known as the information recording medium 2 for holographic recording having no polarization sensitivity. On the other hand, among the information recording medium 2 having photosensitivity, the material of the information recording medium 2 for polarization holographic recording having polarization sensitivity includes an azobenzene-based material, an axially selective photoreactive molecule-added polymer, and photocrosslinkability. Polymer liquid crystals are known. As a practical specific example, a PQ-PMMA (phenanthrenequinone doped polymethylmethacrylate) film having a thickness of about 3 mm can be used as the information recording medium 2 having polarization sensitivity.

In particular, when the information recording medium 2 having polarization sensitivity is irradiated with linearly polarized light or elliptically polarized light, optical anisotropy such as birefringence or dichroism having a principal axis corresponding to the polarization direction of the irradiated polarized light is induced. Has properties. Therefore, if the information recording medium 2 having polarization sensitivity is used, it is possible to record information as a hologram even if the signal light L _S and the reference light L _R whose polarization states are not identical in principle are superimposed and irradiated. It is. That is, in the case of polarization holographic recording, information can be recorded on the information recording medium 2 as a 3D optical anisotropy distribution such as a 3D birefringence distribution or a 3D dichroism distribution. On the other hand, in the case of holographic recording using the information recording medium 2 having no polarization sensitivity, information is recorded as a 3D refractive index distribution.

  By sliding or rotating such an information recording medium 2 with a moving mechanism, it is possible to sequentially record information at different positions on the information recording medium 2. For example, it is possible to sequentially record information while rotating the information recording medium 2 configured as a disk-like disk like a conventional recording medium.

The positional relationship among the irradiation system 4, the information recording medium 2, and the imaging system 5 is as follows. The signal vector wave and p-polarized component as + 1st order diffracted light including the p-polarized component and the s-polarized component transmitted through the information recording medium 2 are shown. 0 reference light L _R as 0-order diffracted light of the reference light L _R and s-polarized component of the order diffracted light of use is determined to overlap in PD27. That is, the arrangement of the irradiation system 4, the information recording medium 2, and the imaging system 5 is determined so that the combined light of the signal light L _S and the reference light L _R is imaged in the PD 27. Accordingly, the arrangement of the optical elements of the irradiation light generation system 3 that causes the reference light L _R and the signal light L _S to enter the irradiation system 4 is also determined in the PD 27 so that the signal light L _S and the reference light L _R overlap. It will be.

Further, information on a recording medium 2, the signal light L _S and the reference light L _R is present a region of overlap, and the signal light L _S and the reference so that the signal light L _S and the reference light L _R overlap in PD27 Light L _R is irradiated.

When the optical system of the optical information recording / reproducing apparatus 1 is configured such that the signal light L _S and the reference light L _R transmitted through the information recording medium 2 overlap in the PD 27 without passing through other optical elements, the information recording medium 2 and the PD 27 An optical element becomes unnecessary between the two. In other words, the optical system of the optical information recording / reproducing apparatus 1 can be configured without providing an optical element between the information recording medium 2 and the PD 27.

However, not limited to the example shown in FIG. 1, an optical element is arranged between the information recording medium 2 and the PD 27 so that the signal light L _S and the reference light L _R passing through the arranged optical element overlap in the PD 27. The optical system of the optical information recording / reproducing apparatus 1 may be configured. In that case, the imaging system 5 is configured by an optical element for superimposing the signal light L _S and the reference light L _R in the PD 27 and an imaging element such as the PD 27. The irradiation system 4, when the reference light L _R for reproducing information is irradiated on the information recording medium 2, the signal light L _S and the information recording medium is reproduced from the information recording medium 2 +1 order diffracted light 2 and the reference light L _R for reproduction of the transmitted information, so as to overlap the imaging device through the optical element, produced as a recording +1 signal light L _S and 0-order beam generated as diffracted light information the be configured reference light L _R to irradiate the information recording medium 2.

  The information reproducing system 6 includes an information reproducing unit 30 to which a second input device 28 and a second display device 29 are connected. The information reproducing unit 30 can be configured by a computer loaded with a program. However, a circuit may be used to configure the information reproducing unit 30.

The information reproducing unit 30 outputs, as an output signal from the PD 27, the complex amplitude of the combined light imaged as an interference fringe between the signal light L _S and the reference light L _R in the PD 27 when reproducing the information recorded on the information recording medium 2. A function to acquire, a function to extract the complex amplitude of the signal light L _S based on the complex amplitude of the combined light of the signal light L _S and the reference light L _R , and a reproduction signal of information based on the complex amplitude of the signal light L _S And a function of outputting a reproduction signal to the second display device 29 or another output device.

The intensity pattern I (x, y) of the combined light at the position (x, y) on the PD 27 is expressed by Expression (4).
I (x, y) = | U _S '+ U _R ' | ² = A _S ² + A _R ² + 2A _S A _R cos (φ _S -φ _R + φ ₀ ) (4)
However, in equation (4), U _S ′ is the complex amplitude of signal light L _S reproduced in proportion to the complex amplitude U _S of each polarization component of signal light L _S represented by equation (2), U _R ′ is proportional to the complex amplitude U _R of the reference light L _R of the formula (3-1), known complex amplitude of the reference beam L _R emitted to the information recording medium 2 at the time of reproduction, the a _S is regenerated The amplitude of the signal light L _S , φ _S is the phase of the signal light L _S to be reproduced, A _R is the amplitude of the irradiated reference light L _R , φ _R is the phase of the irradiated reference light L _R , and φ ₀ is the information This is a constant determined by information recording conditions and reproducing conditions such as the type of the recording medium 2. The value of the constant φ ₀ is not fixed. For this reason, when using a phase for recording and reproducing information, a relative value from a reference phase value can be used on the basis of a phase value in a certain pixel.

Therefore, the equation (4), it is possible to obtain the complex amplitude U _S of the signal light L _S from the complex amplitude U _R of the intensity pattern I (x, y) of the imaged composite light and the reference light L _R.

Further, by executing relative 2D image information corresponding processing and reverse processing of encoding information in the 2D image information into complex amplitude U _S of the signal light L _S, the information recorded on the signal light L _S Can be played. The reproduced information can be output to an output device such as the second display device 29 as a reproduction signal.

As yet another method, the complex amplitude U _S of the signal light L _S can be obtained using a spatial phase difference distribution generated between the signal light L _S and the reference light L _R. That is, a spatial phase difference distribution is given between the signal light L _S and the reference light L _R in the first SLM 15 and the second SLM 16 during information recording. The spatial phase difference distribution between the signal light L _S and the reference light L _R during the information recording is maintained between the reproduced signal light L _S and the reference light L _R.

Therefore, the signal light L _S and the reference beam L _R of the combined light intensity pattern I (x, y) is thus being phase-modulated by different modulation amount for each position. Therefore, an equation for the number of phase modulation amounts is obtained, and an unknown number of phase modulation amounts can be calculated. Therefore, the discrete Fourier transform of each unit area: by (DFT discrete Fourier transform) calculation such, it is possible to obtain the complex amplitude U _S of the signal light L _S at each pixel position (x, y).

When the complex amplitude U _S of the signal light L _S at the position of the PD 27 that is the observation position of the combined light is obtained, the complex amplitude of the signal light L _{S at} an arbitrary observation position of the signal light L _{S in} the computer by the technique of digital holography. Can be obtained. Therefore, if the distortion on the wavefront of the signal light L _S has occurred, you are possible to correct the wavefront. Therefore, these calculation functions can be provided in the information reproducing unit 30. A specific example of a method for calculating the complex amplitude U _S of the signal light L _S by giving a spatial phase difference distribution to the reference light L _R is described in the specification of Japanese Patent Application No. 2012-255092. .

(Operation and action)
Next, the operation and action of the optical information recording / reproducing apparatus 1 will be described.

FIG. 6 is a top view showing the reference light L _R and the signal light L _S generated in the first SLM 15 when information is recorded on the information recording medium 2 by the optical information recording / reproducing apparatus 1 shown in FIG. FIG. 8 is a front view of the reference light L _R and the signal light L _S shown in FIG. 6 viewed from a direction perpendicular to the incident surface of the second SLM 16, and FIG. 8 is a view of the second SF 18 shown in FIG. FIG.

9 is a top view showing the reference light L _R and the signal light L _S generated in the second SLM 16 when information is recorded on the information recording medium 2 by the optical information recording / reproducing apparatus 1 shown in FIG. 10 is a front view of the reference light L _R and the signal light L _S shown in FIG. 9 as viewed from the direction perpendicular to the incident surface of the second SLM 16, and FIG. 11 shows the light traveling direction of the second SF 18 shown in FIG. It is the front view seen from.

  In FIGS. 6 to 11, p-polarized light and s-polarized light in which at least one of the amplitude and the phase is spatially modulated by the first SLM 15 and the second SLM 16 are separately illustrated. p-polarized light and s-polarized light are generated.

The 45-degree linearly polarized light generated from the laser light source 7 through the HWP 8, the first collimator lens 9, the first SF 10, the second collimator lens 11, the first mirror 12 and the second mirror 13 is incident light L _IN. As shown in FIGS. 6 and 7, the s-polarized light reflected by the PBS 14 enters the first SLM 15 in an oblique direction.

  When information is recorded on the information recording medium 2, a control signal corresponding to the first information to be recorded is output from the information input system 19 to the first SLM 15. Therefore, the p-polarized components of the 0th order light, the + 1st order diffracted light, and the −1st order diffracted light generated by the diffraction in the first SLM 15 are transmitted through the PBS 14. As a result, p-polarized 0th-order light, + 1st-order diffracted light, and −1st-order diffracted light with spatially modulated complex amplitude corresponding to the first information to be recorded are generated. The p-polarized 0th-order light, + 1st-order diffracted light, and −1st-order diffracted light are focused by the third collimator lens 17 and are incident on the second SF 18.

In the second SF 18, as shown in FIGS. 6, 7, and 8, the −1st order diffracted light is blocked and only the 0th order light and the + 1st order diffracted light pass. Then, the p-polarized + 1st order diffracted light that has passed through the second SF 18 is used as the signal light L _S, and the 0th order light is used as the reference light L _R. The signal light L _S composed of p-polarized light in which the first information is recorded as spatial modulation of complex amplitude is irradiated with the reference light L _R and composed of the fourth collimator lens 25 and the fifth collimator lens 26. The information recording medium 2 is irradiated in a spot shape by the system 4.

In this case, as the reference light L _R and the signal light L _S of the p-polarized light transmitted through the information recording medium 2 is a positional relationship of imaged as a combined light in PD27 of the imaging system 5, the reference light L _R and the signal light L _S is applied to the information recording medium 2. Accordingly, the first information is recorded on the information recording medium 2 as a 3D optical anisotropy distribution such as a 3D birefringence distribution.

On the other hand, as shown in FIGS. 9 and 10, p-polarized light transmitted through the PBS14 the incident light L _IN is incident on PBS14 is incident obliquely on the second SLM 16.

  When information is recorded on the information recording medium 2, a control signal corresponding to the second information to be recorded is output from the information input system 19 to the second SLM 16. For this reason, the s-polarized components of the 0th order light, the + 1st order diffracted light, and the −1st order diffracted light generated by the diffraction in the second SLM 16 are reflected by the PBS 14. As a result, s-polarized 0th-order light, + 1st-order diffracted light, and -1st-order diffracted light with spatially modulated complex amplitude corresponding to the second information to be recorded are generated. The s-polarized 0th-order light, + 1st-order diffracted light, and −1st-order diffracted light are focused by the third collimator lens 17 and are incident on the second SF 18.

In the second SF 18, as shown in FIGS. 9, 10, and 11, the −1st order diffracted light is blocked and only the 0th order light and the + 1st order diffracted light pass. Then, the s-polarized + 1st order diffracted light that has passed through the second SF 18 is used as the signal light L _S, and the 0th order light is used as the reference light L _R. The signal light L _S composed of s-polarized light in which the second information is recorded as spatial modulation with complex amplitude is irradiated with the reference light L _R and composed of the fourth collimator lens 25 and the fifth collimator lens 26. The information recording medium 2 is irradiated in a spot shape by the system 4.

In this case, as the reference light L _R and the signal light L _S of the s-polarized light transmitted through the information recording medium 2 is a positional relationship of imaged as a combined light in PD27 of the imaging system 5, the reference light L _R and the signal light L _S is applied to the information recording medium 2. Thereby, the information recording medium 2 records the second information as a 3D optical anisotropy distribution such as a 3D birefringence distribution.

As described above, generation of p-polarized light in which the first information is recorded as spatial modulation and generation of s-polarized light in which the second information is recorded as spatial modulation are performed simultaneously. In addition, the p-polarized light path on which the first information is recorded matches the s-polarized light path on which the second information is recorded. Therefore, a vector wave in which the first information is recorded in the p-polarized component and the second information is recorded in the s-polarized component is spot-irradiated on the information recording medium 2 as the signal light L _S. As a result, the first information and the second information are simultaneously recorded on the information recording medium 2 as a 3D optical anisotropy distribution. On the other hand, the reference light L _R for p-polarized light component, the reference light L _R for s-polarized light component is spot irradiation respectively through separate optical paths to the information recording medium 2.

FIG. 12 shows the reference light L _R generated in the first SLM 15 and the reproduced signal light L _S when the information recorded on the information recording medium 2 is reproduced by the optical information recording / reproducing apparatus 1 shown in FIG. top view, FIG. 13 is the reference light L _R and the reproduced signal beam L _S a front view seen from the direction perpendicular to the incident surface of the second SLM16 shown in FIG. 12, FIG. 14 is a second SF18 shown in FIG. 13 showing It is the front view which looked at from the advancing direction of light.

FIG. 15 shows the reference light L _R generated in the second SLM 16 and the reproduced signal when the information recorded in the information recording medium 2 is reproduced by the optical information recording / reproducing apparatus 1 shown in FIG. 16 is a top view showing the light L _S , FIG. 16 is a front view of the reference light L _R shown in FIG. 15 and the signal light L _S to be reproduced viewed from a direction perpendicular to the incident surface of the second SLM 16, and FIG. It is the front view which looked at 2nd SF18 shown to from the advancing direction of light.

In FIG. 17 from FIG. 12, although the reference light L _R and reproduced signal light L _S is generated by the first SLM15 and second SLM16 are shown separately, in fact at the same time the reference beam L _R and reproduction signal light L _S are generated.

  When reproducing the information recorded on the information recording medium 2, the control signal corresponding to the information is not output from the information input system 19 to the first SLM 15 and the second SLM 16. Therefore, the first SLM 15 and the second SLM 16 do not execute spatial modulation for recording information. Then, the first SLM 15 and the second SLM 16 are controlled so that diffracted light is not generated in the first SLM 15 and the second SLM 16.

For this reason, as shown in FIGS. 12 and 13, when the incident light L _IN composed of the p-polarized component and the s-polarized component is incident on the PBS 14 and reflected, and the s-polarized light is incident on the first SLM 15 in an oblique direction. The first SLM 15 reflects only the 0th-order light whose polarization state has changed uniformly according to the applied voltage. Zero-order reflected light from the first SLM15 is a p-polarized light of the reference light L _R is transmitted through the PBS 14. Therefore, in the first SLM 15, it is preferable to rotate the polarization direction of s-polarized light uniformly by 90 degrees and reflect p-polarized light from the first SLM 15.

However, it may be provided with the same spatial distribution as the time of recording the incident light L _IN to be incident on PBS14 during playback. In that case, the reference light _LR is generated as a non-plane wave.

The p-polarized light transmitted through the PBS 14 passes through the third collimator lens 17, the second SF 18 and the irradiation system 4 to the information recording medium 2 as the reference light L _R as shown in FIGS. 12, 13 and 14. Spot irradiation. As a result, from the information recording medium 2 to the PD27 of the imaging system 5, along with the transmitted light of the reference light L _R, + 1 signal light L _S of the p-polarized light is generated as diffracted light. That is, the p-polarized signal light L _S is reproduced as the + 1st order diffracted light.

Due to the nature of holography, the complex amplitude of the + 1st order diffracted light to be reproduced is equivalent to the complex amplitude of the + 1st order diffracted light recorded on the information recording medium 2. Therefore, the regenerated p-polarized signal light L _S overlaps the transmitted light of the reference light L _{R in} the PD 27. Thereby, in PD27, the intensity pattern of the interference pattern of p polarization | polarized-light equivalent to the time of the information recording on the information recording medium 2 is imaged.

Similarly, as shown in FIGS. 15 and 16, transmitted is incident on the incident light L _IN is PBS 14, the p-polarized light is incident obliquely on the second SLM 16, depending on the applied voltage from the second SLM 16 Thus, only the 0th order light whose polarization state has changed uniformly is reflected. 0-order light reflected from the second SLM16 becomes s-polarized light of the reference light L _R reflected by the PBS 14. Therefore, it is preferable that the polarization direction of the p-polarized light is uniformly rotated by 90 degrees in the second SLM 16 and the s-polarized light is reflected from the second SLM 16.

The s-polarized light reflected by the PBS 14 passes through the third collimator lens 17, the second SF 18 and the irradiation system 4 to the information recording medium 2 as the reference light L _R as shown in FIGS. 15, 16 and 17. Spot irradiation. As a result, from the information recording medium 2 to the PD27 of the imaging system 5, along with the transmitted light of the reference light L _R, + 1 signal light L _S of the s-polarized light as a diffracted light is generated. That is, the s-polarized signal light L _S is reproduced as the + 1st order diffracted light.

Therefore, similarly to the p-polarized light of the reproduced signal beam, s-polarized light of the reproduced signal beam overlaps with the transmitted light of the reference light L _R at PD27. As a result, the PD 27 images an intensity pattern of s-polarized interference fringes equivalent to that when recording information on the information recording medium 2.

As described above, the reproduction of the p-polarized signal light L _{S and} the reproduction of the s-polarized signal light L _S are performed simultaneously. Further, p-polarized light of the reproduction signal light, transmitted light p-polarized reference light L _R, s-polarized light of the reproduction signal light, transmitted light of the reference light L _R of the s-polarized light, overlap in PD27. Therefore, the first information and the second information recorded as the 3D optical anisotropy distribution on the information recording medium 2 refer to the vector wave recorded as the complex amplitude spatial modulation in the p-polarized component and the s-polarized component, respectively. The light L _R is incident on the PD 27 in a combined state.

Then, in the information reproduction system 6, the amplitude and phase of the signal light L _S can be obtained based on the contrast and phase of the intensity pattern of the synthesized light imaged by the PD 27. Since the signal light L _S has two orthogonal polarization components, the first information and the second information can be acquired independently from the amplitude and phase of each polarization component. Then, the acquired first information and second information can be output to an output device such as the second display device 29.

When a spatial distribution is given to the polarization direction of the incident light L _IN incident on the PBS 14 at the time of reproduction, the intensity pattern of the synthesized light imaged by the PD 27 is changed to the polarization of the incident light L _IN incident upon the recording. Divide by the spatial distribution of orientation.

  FIG. 18 is a front view of the second SF 18 as viewed from the traveling direction of light when reproducing the information recorded on the information recording medium 2 when the second SF 18 having the structure shown in FIG. 3 is used. is there.

If the second information using the SF18 having four rectangular holes as shown in FIG. 3 has been recorded, p-polarized light and s-polarized light of the reference light L _R separately generated as shown in FIG. 18 Only the information is reproduced by passing through the second SF 18. Others are the same as when information is reproduced using the second SF 18 having three rectangular holes.

That more than the optical information recording and reproducing apparatus 1 as the signal light L _S produced as a + 1st-order diffracted light for the recording of information, 0 while irradiating with the reference light L _R generated order diffracted light on the information recording medium 2, the information during the reproduction, it is obtained by such imaging by the imaging device + 1-order signal light L _S to be reproduced as a diffracted light 0 completely overlapped with the reference light L _R irradiated order diffracted light.

In the above example, the case where the optical system of the optical information recording / reproducing apparatus 1 is configured so that the optical path of the signal light L _S is mainly the center of the optical element including the second SF 18 has been described. The optical system may be configured such that the optical path of L _S is inclined with respect to the central axis of the optical element. That is, the direction of the incident light L _IN incident on the PBS 14, the inclination of the striped pattern formed on the first SLM 15 and the second SLM 16, and the direction of the optical path of the signal light L _S are signals generated as + 1st order diffracted light. The condition can be changed so that the light L _S and the reference light L _R generated as the 0th-order diffracted light are incident on the PD 27 in a state where they overlap each other.

(effect)
According to the optical information recording / reproducing apparatus 1 as described above, the configuration can be greatly simplified. Therefore, it is possible to reduce the size of the apparatus for practical use.

  In the conventional holographic recording and polarization holographic recording, it is necessary to dispose an optical element between the information recording medium and the imaging element so that the signal light does not overlap with the reference light. That is, in the conventional holographic recording and polarization holographic recording, an imaging optical system for imaging the signal light in the imaging element is required.

On the other hand, according to the optical information recording / reproducing apparatus 1, information included in the vector wave of the reproduction signal light L _S can be reproduced using a single image sensor. That is, the information recorded in the minute area of the information recording medium 2 can be enlarged and reproduced without arranging an optical element between the information recording medium 2 and the imaging element.

Further, according to the optical information recording and reproducing apparatus 1, the reference light L _R and the signal light L _S, it can be generated using a common optical element. Therefore, it is not necessary to specially provide an optical path of the reference light L _R optics and the reference light L _R for generating.

Furthermore, according to the optical information recording / reproducing apparatus 1, the complex amplitudes of the two modulated polarization components can be obtained simultaneously from the intensity pattern of the synthesized light imaged by the image sensor. That is, the complex amplitude of the reproduction signal light L _S that is a vector wave can be acquired. Therefore, even when the wavefront of the signal light L _S is distorted, it is possible to correct the wavefront of the signal light L _{S in} the computer by the digital holography technique. As a result, even when an image that has not been imaged is captured, it can be imaged on a computer.

  On the other hand, in the conventional holographic recording and polarization holographic recording apparatus, it is necessary to adjust the optical system so that distortion does not occur in an image picked up by the image pickup device. On the other hand, the optical information recording / reproducing apparatus 1 does not require an optical system for reducing distortion of an image captured by the image sensor.

  As described above, the optical information recording / reproducing apparatus 1 can eliminate various optical systems that have been conventionally required.

In addition, according to the optical information recording / reproducing apparatus 1, the sensitivity to the signal to be reproduced can be improved. As in the prior art, when only the signal light is photographed, a signal whose intensity is proportional to the square of the amplitude of the signal light is acquired. On the other hand, when the signal light L _S is photographed with the reference light L _R superimposed, a signal having an amplitude proportional to a value obtained by multiplying the amplitude of the signal light L _{S by} the amplitude of the reference light L _R and 2 is acquired. The Therefore, the sensitivity to the signal to be reproduced can be improved.

As a result, the intensity of the necessary reproduction signal light L _S can be reduced. Therefore, the energy of the signal light L _S to be irradiated on the information recording medium 2 for recording information can also be reduced.

  As a specific example, when only the signal light with an amplitude of 1 is detected when the maximum value of the amplitude of the signal light is 65535, the square of the amplitude is also 1, so the noise level of the image sensor is obtained. Therefore, it is difficult to detect signal light having an amplitude of 1.

On the contrary, when the reference light L _R and the signal light L _S of amplitude 1 of the amplitude 255 is synthesized and photographed, the amplitude of the multiplied by the amplitude 255 of the reference light L _R and the second signal light L _S becomes 510. Therefore, it is possible to detect the signal light L _S having an amplitude of 1. That is, the optical information recording / reproducing apparatus 1 can reproduce the signal light L _S having an amplitude smaller than that in the conventional case when the imaging elements having the same sensitivity are used.

(Second Embodiment)
In the optical information recording / reproducing apparatus according to the second embodiment, two SLMs used in the spatial modulation system are respectively replaced with special optical elements in which a plurality of variable diffraction gratings are arranged in a 2D shape. This is different from the optical information recording / reproducing apparatus 1 in FIG. Unless otherwise specified, the other configuration and operation of the optical information recording / reproducing apparatus in the second embodiment are substantially the same as those of the optical information recording / reproducing apparatus 1 in the first embodiment.

  For this reason, only a special optical element in which a plurality of variable diffraction gratings are arranged in a 2D shape is illustrated, and the description of the same contents as those of the optical information recording / reproducing apparatus 1 in the first embodiment is omitted. Hereinafter, a special optical element in which a plurality of variable diffraction gratings are arranged in a 2D shape is referred to as a variable diffraction grating array.

  FIG. 19 is a front view showing the structure of a variable diffraction grating array used in the spatial modulation system of the optical information recording / reproducing apparatus according to the second embodiment of the present invention, and FIG. 20 is a sectional view of the variable diffraction grating array shown in FIG. FIG. 21 is a perspective view of the first alignment film shown in FIG.

  A variable grating array (VGA) 31 corresponds to a first alignment film 33, a liquid crystal layer 34, a second alignment film 35, and pixels that form a substrate on a flat plate-like first electrode 32. A plurality of second electrodes 36 arranged two-dimensionally are stacked. Accordingly, by independently applying a desired voltage to each of the plurality of second electrodes 36, the spatial modulation of the amplitude of the polarization component can be performed for each pixel.

  However, the first alignment film 33 that forms the substrate has a wave shape in which irregularities are periodically repeated in an oblique direction with respect to the arrangement direction of the second electrodes 36. On the other hand, the second alignment film 35 has a flat shape without unevenness. Therefore, the shape of the liquid crystal layer 34 formed between the first alignment film 33 and the second alignment film 35 is a shape that fits the shape of the first alignment film 33.

  That is, the shape of the liquid crystal layer 34 on the first alignment film 33 side also has a wave shape that repeats unevenness periodically in an oblique direction with respect to the arrangement direction of the second electrodes 36. Therefore, when the plurality of second electrodes 36 are arranged in two directions, the x-axis direction and the y-axis direction, the thickness of the liquid crystal layer 34 is periodic in the two arrangement directions of the x-axis direction and the y-axis direction. Will change. In the illustrated example, the unevenness of the substrate and the liquid crystal layer 34 is a sine curve.

  As described above, in the VGA 31 having the structure in which the liquid crystal layer 34 in which the smooth unevenness periodically changes is sandwiched between the first electrode 32 and the number of the second electrodes 36 corresponding to the number of pixels, In FIG. Therefore, diffracted light can be generated for each pixel in the direction in which the transmittance changes. That is, it is possible to create a striped light-dark pattern simply by applying a single voltage to one second electrode 36. This corresponds to controlling the SLM with 2D image information in which pixel values continuously change within one pixel.

  In other words, the boundary is not clear, but information is recorded by coding into 2D image information using a single pixel equivalent to a unit area composed of a plurality of pixel areas as shown in FIG. It becomes possible to do. In other words, by controlling one second electrode 36, a multi-value unit region that is substantially equivalent to a plurality of pixel regions can be created. Therefore, 16 × 16 pixel 2D image data as shown in FIG. 4A can be recorded in the signal light by using 16 × 16 second electrodes 36.

  FIG. 22 is a diagram showing a modification of the VGA 31 shown in FIG.

  As shown in FIG. 22, the uneven shape of the liquid crystal layer 34 can be various shapes. In the VGA 31 shown in FIG. 22, the thickness of the liquid crystal layer 34 changes linearly. That is, the liquid crystal layer 34 is a region surrounded by a plane.

  Of course, unevenness may be provided on the second alignment film 35 side. However, from the viewpoint of concentrating energy on the 0th-order light and the + 1st-order diffracted light reflected by the VGA 31, as shown in FIGS. 20 and 21, the liquid crystal layer 34 changes in thickness along the sine curve. It is preferred to determine the shape of layer 34.

  As described above, the VGA 31 has a plurality of variable diffraction gratings arranged two-dimensionally, and an optical element in which the transmittance of each variable diffraction grating changes in a direction inclined with respect to the arrangement direction of the plurality of variable diffraction gratings. It is an element. Specifically, the VGA 31 is a direction in which the thickness of the liquid crystal layer 34 disposed between the first electrode 32 and the plurality of second electrodes 36 is inclined with respect to the arrangement direction of the second electrodes 36. In addition, the optical element is periodically changed at a period corresponding to each width of the plurality of second electrodes 36.

  For this reason, according to the VGA 31, it is possible to form a striped light pattern whose intensity changes in an integer period in the generation direction of the + 1st order diffracted light and the −1st order diffracted light in the unit region corresponding to the second electrode 36. it can.

  In the second embodiment, signal light and reference light are generated by spatial modulation of incident polarized light by the VGA 31.

  For this reason, according to the second embodiment, in addition to the effect equivalent to the effect in the first embodiment, the number of electrodes required corresponding to the number of pixels in the spatial modulation system can be reduced. That is, in the case of performing amplitude spatial modulation on signal light, a unit region composed of a plurality of pixels as shown in FIG. 4B can be handled as one pixel.

  In the VGA 31, the position of the striped pattern generated at each pixel position cannot be shifted. However, if the position of the VGA 31 is mechanically shifted, the phase of incident polarized light can be modulated. Further, although the example in which the VGA 31 is configured by arranging the liquid crystal variable diffraction grating has been shown, the VGA 31 can also be configured by arranging other variable diffraction gratings.

(Third embodiment)
In the optical information recording / reproducing apparatus in the third embodiment, a spatial modulation system is configured so that the phase and amplitude of a single polarization component can be spatially modulated using two VGAs 31 exemplified in the second embodiment. This point is different from each optical information recording / reproducing apparatus in the first and second embodiments. Unless otherwise specified, the other configurations and operations of the optical information recording / reproducing apparatus in the third embodiment are substantially the same as those of the optical information recording / reproducing apparatuses in the first and second embodiments. For this reason, only the spatial modulation system is shown, and the description of the same contents as those of the optical information recording / reproducing apparatuses in the first and second embodiments is omitted.

  FIG. 23 is a diagram showing a configuration of a spatial modulation system provided in an optical information recording / reproducing apparatus according to the third embodiment of the present invention.

  As shown in FIG. 23, the spatial modulation system 40 includes a first VGA 41, a second VGA 42, a first quarter-wave plate (QWP) 43, a second QWP 44, and a PBS 45. They can be arranged and configured as such. When the change in transmittance corresponding to the period of unevenness of the two VGAs, that is, the first VGA 41 and the second VGA 42 is shifted by a quarter period, the phase is also spatially modulated in addition to the amplitude of a single polarization component. It becomes possible. This is because when the sin curve and the cos curve are added, all phases can be expressed by the addition theorem of the trigonometric function.

When the incident light L _IN is incident on the PBS 45 of the spatial modulation system 40 shown in FIG. 23, the p-polarized + 1st order diffracted light whose phase and amplitude are spatially modulated by the first VGA 41 and the second VGA 42 is used as the signal light. Can be generated as Further, reference light corresponding to p-knitted light can be generated as zero-order diffracted light.

  The first 1 / 4QWP 43 is provided to transmit the reflected light reflected by the PBS 45 and the first VGA 41 through the PBS 45. Similarly, the second QWP 44 is provided to reflect the reflected light that is transmitted through the PBS 45 and reflected by the second VGA 42 at the PBS 45.

  According to the third embodiment, in addition to the same effect as that of the second embodiment, the phase of the signal light can be spatially modulated by combining two VGAs.

(Fourth embodiment)
In the optical information recording / reproducing apparatus according to the fourth embodiment, the phase and amplitude of the two polarization components are spatially reduced by using two sets of the spatial modulation system 40 composed of the two VGAs exemplified in the third embodiment. This is different from the optical information recording / reproducing apparatuses in the first, second, and third embodiments in that the spatial modulation system is configured so that the optical modulation can be performed. Unless otherwise specified, the other configurations and operations of the optical information recording / reproducing apparatus in the fourth embodiment are substantially the same as those of the optical information recording / reproducing apparatuses in the first, second, and third embodiments. For this reason, only the spatial modulation system is illustrated, and the description of the same contents as those of the optical information recording / reproducing apparatuses in the first, second, and third embodiments is omitted.

  FIG. 24 is a diagram showing a configuration of a spatial modulation system provided in an optical information recording / reproducing apparatus according to the fourth embodiment of the present invention.

  As shown in FIG. 24, the spatial modulation system 50 includes a first VGA 51, a second VGA 52, a third VGA 53, a fourth VGA 54, a first PBS 55, a second PBS 56, a third PBS 57, a first The QWP 58 and the second QWP 59 can be arranged and configured as shown. The spatial modulation system 50 includes the first SLM 15 shown in FIG. 1 as an optical system including a first VGA 51 and a second VGA 52, and the second SLM 16 includes a third VGA 53 and a fourth VGA 54. This corresponds to an optical system. That is, the spatial modulation system 50 is configured using four VGAs for phase modulation of the p-polarized component, amplitude modulation of the p-polarized component, phase modulation of the s-polarized component, and amplitude modulation of the s-polarized component. .

  Therefore, the spatial modulation of the amplitude and phase of the p-polarized component and the s-polarized component can be performed using the four VGAs. For example, if four VGAs of 16 × 16 pixels are used, 4 frames of 2D multi-value image information as shown in FIG. 5 can be recorded in the signal light.

  FIG. 25 is a block diagram showing a modification of the spatial modulation system 50 shown in FIG.

  As shown in FIG. 25, the spatial modulation system 50 can be configured by combining and arranging various optical elements.

  In the fourth embodiment as described above, 4-frame image information is recorded by using the real part and the imaginary part of two polarization components orthogonal to each other by the spatial modulation system 50 having at least four VGAs. The generated signal light is generated. For this reason, as in the first and second embodiments, it is possible to record information and reproduce information using two channels.

(Fifth embodiment)
In the optical information recording / reproducing apparatus according to the fifth embodiment, the phase and amplitude of a single polarization component can be spatially modulated using an AO element array in which a plurality of acousto-optic (AO) elements are arranged. The difference between the optical information recording / reproducing apparatuses in the first to fourth embodiments is that a spatial modulation system is configured. Unless otherwise specified, the other configurations and operations of the optical information recording / reproducing apparatus in the fifth embodiment are substantially the same as those of the optical information recording / reproducing apparatuses in the first to fourth embodiments. For this reason, only the spatial modulation system is illustrated, and the description of the same contents as those of the optical information recording / reproducing apparatuses in the first to fourth embodiments is omitted.

  FIG. 26 is a diagram showing the configuration of the spatial modulation system provided in the optical information recording / reproducing apparatus according to the fifth embodiment of the present invention.

  As shown in FIG. 26, the spatial modulation system 60 can be configured using an AO element array 61 in which AO elements are arranged in a two-dimensional manner in the x-axis direction and the y-axis direction. For example, if a plurality of 64 × 64 AO elements are arranged, a binary image of 64 × 64 pixels as shown in FIG. 4B or a large number of 64 × 64 pixels as shown in FIG. A value image can be recorded in a single polarization component.

  Specifically, the amplitude of the polarization component can be spatially modulated by independent control of the voltage applied to each AO element. Further, the phase of the polarization component can be spatially modulated by mechanically shifting each AO element independently in a direction parallel to the plane on which the plurality of AO elements are arranged. The mechanical movement of the AO element can be performed, for example, by applying a voltage to the piezo element.

  Accordingly, if two spatial modulation systems 60 for the p-polarized component and the s-polarized component are provided in the optical information recording / reproducing apparatus, information on two channels is recorded on the signal light using the p-polarized component and the s-polarized component. Is possible,

  In the fifth embodiment as described above, information is recorded in the polarization component of signal light using a plurality of AO elements that are two-dimensionally arranged corresponding to a plurality of pixels. For this reason, also in 5th Embodiment, the effect similar to 1st Embodiment can be acquired. Further, since the response of the AO element is faster than the response of the SLM, information can be recorded on the signal light at a higher speed.

(Sixth embodiment)
In the optical information recording / reproducing apparatus in the sixth embodiment, the spatial modulation system is configured so that only the phase of a single polarization component is spatially modulated by making linearly polarized light having a predetermined polarization direction obliquely incident on the SLM. This is different from the optical information recording / reproducing apparatuses in the first to fifth embodiments. Unless otherwise specified, the other configurations and operations of the optical information recording / reproducing apparatus in the sixth embodiment are substantially the same as those of the optical information recording / reproducing apparatuses in the first to fifth embodiments. For this reason, only the spatial modulation system is shown, and the description of the same contents as those of the optical information recording / reproducing apparatuses in the first to fifth embodiments is omitted.

  FIG. 27 is a diagram showing a configuration of a spatial modulation system provided in the optical information recording / reproducing apparatus according to the sixth embodiment of the present invention.

As shown in FIG. 27, the spatial modulation system 70 can be configured by an SLM 71 arranged to be inclined with respect to incident light L _IN that is incident as, for example, 45-degree linearly polarized light. If the liquid crystal is oriented in the 0 degree direction parallel to the paper surface in the SLM 71, the phase of only the 0 degree linearly polarized light component of the 45 degree linearly polarized light can be spatially modulated.

Therefore, it is possible to produce a polarization of the zero-order light having an amplitude perpendicular direction of 90 degrees to the plane as the reference light L _R. At the same time, the polarization of the + 1st order diffracted light having the amplitude in the 0 degree direction parallel to the paper surface and the phase of which is spatially modulated by the SLM 71 can be generated as the signal light L _S. Therefore, information on one channel can be recorded in the signal light L _S using a single polarization component.

In this case, the polarization direction of the reference light L _{R and} the polarization direction of the signal light L _S are orthogonal to each other. Therefore, as shown in the drawing, a polarizer 72 is disposed in front of the PD 27. That is, the imaging system 5 includes a polarizer 72 and a PD 27 as an imaging element.

On the other hand, if oriented in a vertical direction of 90 degrees of the liquid crystal SLM71 on paper, it is possible to produce a polarization of the zero-order light having an amplitude of parallel 0-degree direction to the paper surface as the reference light L _R. At the same time, the polarization of the + 1st order diffracted light having an amplitude in the direction of 90 degrees perpendicular to the paper surface and the phase of which is spatially modulated by the SLM 71 can be generated as the signal light L _S. Therefore, if two spatial modulation systems 70 are provided in the optical information recording / reproducing apparatus for two polarization components having orthogonal polarization directions, information on two channels is recorded on the signal light L _S using the two polarization components. It becomes possible.

In the sixth embodiment as described above, a signal having a polarization component in which information is recorded by spatial modulation of the reference light _LR and the phase by making linearly polarized light having a predetermined polarization direction obliquely incident on the SLM 71. The light L _S is generated. For this reason, also in 6th Embodiment, the effect similar to 1st Embodiment can be acquired.

Further, in the sixth embodiment, the incident light L _IN incident on the SLM 71 is not uniform and is a beam array. As a result, in principle, noise can be sufficiently reduced even if the intensity change of the striped light pattern formed in the generation direction of the + 1st order diffracted light and the −1st order diffracted light does not become an integer period. Therefore, the reference light L _R and the reproducible signal light L _S can be generated by forming, on the SLM 71, a striped light pattern whose intensity changes with an integer period or a non-integer period in the unit region. .

(Seventh embodiment)
In the optical information recording / reproducing apparatus in the seventh embodiment, the amplitude ratio and the phase difference between the p-polarized component and the s-polarized component are obtained using a VR array configured by arranging a plurality of variable retarders (VR). The difference between the optical information recording / reproducing apparatuses in the first to sixth embodiments is that the spatial modulation system is configured so that at least one of them can be spatially modulated.

  Further, in the optical information recording / reproducing apparatus in the seventh embodiment, orthogonal polarization components are used as signal light and reference light, as in the sixth embodiment. However, in the optical information recording / reproducing apparatus in the seventh embodiment, a WR array configured by arranging a plurality of Wollaston prisms (WP) is used to separate the signal light and the reference light.

  Unless otherwise specified, the other configurations and operations of the optical information recording / reproducing apparatus in the seventh embodiment are substantially the same as those of the optical information recording / reproducing apparatuses in the first to sixth embodiments. For this reason, only the spatial modulation system is illustrated, and the description of the same contents as those of the optical information recording / reproducing apparatuses in the first to sixth embodiments is omitted.

  FIG. 28 is a diagram showing a configuration of a spatial modulation system provided in an optical information recording / reproducing apparatus according to the seventh embodiment of the present invention.

  As shown in FIG. 28, the spatial modulation system 80 includes first and second VR arrays 81 and 82 configured by arranging VRs in 2D in the x-axis direction and the y-axis direction, and the x-axis direction. And a single WP array 83 configured by arranging WPs in 2D in the y-axis direction. VR is composed of an electro-optic element or a liquid crystal element.

First VR array 81 is an optical element for performing modulation of the p-polarized light component and s the amplitude ratio of the polarized light components contained in the incident light L _IN to spatial modulation system 80. On the other hand, the second VR array 82 is an optical element for modulating the phase difference between the p-polarized component and the s-polarized component included in the polarized light transmitted through the first VR array 81. Specifically, one or both of the amplitude ratio and the phase difference between the p-polarized component and the s-polarized component are controlled by independent control of the voltage applied to each VR constituting the first and second VR arrays 81 and 82. Spatial modulation can be performed. Therefore, when both the amplitude ratio and the phase difference are modulated, the spatial modulation system 80 is configured using a pair of the first VR array 81 and the second VR array 82.

  For example, if the first and second VR arrays 81 and 82 in which 64 × 64 VRs are arranged are provided in the spatial modulation system 80, the image data of 64 × 64 pixels as shown in FIG. Any of 64 × 64 pixel multi-value image data as shown in (B) can be recorded in a single polarization component.

The polarized light on which information is recorded in the first and second VR arrays 81 and 82 enters the WP array 83. Each WP constituting the WP array 83 is an optical element having birefringence in which two prisms made of calcite, quartz, and the like are combined so that their crystal axes are orthogonal to each other. When WP is used, incident light can be separated into two orthogonal polarization components forming an opening angle. Accordingly, the polarized light incident on the WP array 83 is separated into the signal light L _S and the reference light L _R.

Then, the signal light L _S and the reference light L _R emitted from the WP array 83 are focused by the collimator lens 84 and enter the SF 85. Then, the signal light L _S and the reference light L _R that have passed through the SF 85 are used as output light of the irradiation light generation system.

In the seventh embodiment as described above, information is recorded in a polarization component that becomes signal light using a plurality of VRs that are two-dimensionally arranged corresponding to a plurality of pixels. In addition, the signal light L _S and the reference light L _R that are orthogonal as two polarization components are separated into ordinary rays (ordinary ray: O rays) and extraordinary rays (E rays) by a prism. is there.

That is, in the seventh embodiment, the signal light L _S is generated not as + 1st order diffracted light but as light separated by a birefringent prism. Meanwhile, instead of the reference light L _R is as 0-order light is produced as a separate light separated by the prism. Therefore, when reproducing information, the reproduction signal light generated as light corresponding to the light divided by the prism and the reference light generated as light corresponding to another light divided by the prism are superimposed and imaged. .

  For this reason, also in 7th Embodiment, the effect similar to other embodiment can be acquired. Further, since the response of the electro-optical element is faster than the response of the SLM, information can be recorded on the signal light at a higher speed.

(Other embodiments)
Although specific embodiments have been described above, the described embodiments are merely examples, and do not limit the scope of the invention. The novel methods and apparatus described herein can be implemented in a variety of other ways. Various omissions, substitutions, and changes can be made in the method and apparatus described herein without departing from the spirit of the invention. The appended claims and their equivalents include such various forms and modifications as are encompassed by the scope and spirit of the invention.

  For example, in the first, second, and fourth embodiments described above, the first information and the second information are recorded in the two polarization components of the p-polarization component and the s-polarization component of the signal light as a vector wave. As described above, the first information and the second information may be recorded in two polarization components other than the p-polarization component and the s-polarization component. For example, if the QWP is arranged on the optical path of the signal light, the first information and the second information can be recorded in two polarization components of clockwise circular polarization and counterclockwise circular polarization. As described above, by arranging an arbitrary optical element on the optical path of the signal light, the first information and the second information can be recorded in the two polarization components of the clockwise elliptical polarization and the counterclockwise elliptical polarization. .

  That is, it is possible to generate signal light in which information is recorded in any two polarization components orthogonal to each other using at least two SLMs or a necessary number of variable diffraction grating arrays. It is also possible to generate signal light in which information is recorded in the real part and the imaginary part of the polarization component by spatial modulation of the phase and amplitude.

  In other words, by arranging an optical element on the optical path of the signal light, the p-polarized component in which the first information is recorded and the s-polarized component in which the second information is recorded are changed to other polarized components, respectively. be able to. Alternatively, the polarization component in which the first information is recorded and the polarization component in which the second information is recorded can be generated in the spatial modulation system as two polarization components other than the p-polarization component and the s-polarization component. Even in this case, information can be recorded on the information recording medium 2 and information recorded on the information recording medium 2 can be reproduced in the same manner as when information is recorded on the p-polarized component and the s-polarized component. .

  In the third, fifth, and sixth embodiments in which information is recorded in a single polarization component, linearly polarized light such as p-polarized light and s-polarized light, clockwise circularly polarized light, and left Information can be recorded in circularly polarized light such as circularly polarized light and elliptically polarized light such as clockwise elliptically polarized light and counterclockwise elliptically polarized light.

  The VGA 31 shown in the second embodiment is an example when p-polarized light or s-polarized light is incident. For this reason, the direction in which the transmittance changes in each variable diffraction grating is inclined 45 with respect to the arrangement direction of the variable diffraction grating. However, when circularly polarized light or elliptically polarized light is incident on the VGA 31, the direction in which the transmittance of each variable diffraction grating changes can be determined as an arbitrary direction. That is, the VGA 31 can be configured as an optical element in which the transmittance of the plurality of variable diffraction gratings changes in a specific direction in accordance with the incident polarized light. Further, the direction in which the transmittance is changed can be determined by the tilt direction of the liquid crystal in the example shown in FIG.

DESCRIPTION OF SYMBOLS 1 ... Optical information recording / reproducing apparatus, 2 ... Information recording medium, 3 ... Irradiation light generation system, 4 ... Irradiation system, 5 ... Imaging system, 6 ... Information reproduction system, 7 ... Laser light source, 8 ... 1/2 wavelength plate (HWP), 9 ... first collimator lens, 10 ... first spatial filter (SF), 11 ... second collimator Lens, 12 ... first mirror, 13 ... second mirror, 14 ... polarization beam splitter (PBS), 15 ... first spatial light modulator (SLM), 16 ... Second SLM, 17 ... third collimator lens, 18 ... second SF, 19 ... information input system, 20 ... first input device, 21 ... first display Device, 22 ... information processing device, 23 ... information acquisition unit, 24 ... 2D encoding unit, 25 ... fourth collimator lens, 26 ... fifth collimator lens, 27 ... .. Photodetector (PD), 28 ... second input device, 29 ... second display device, 30 ... information reproducing unit, 31 ... variable diffraction grating Ray (VGA) 32 ... first electrode 33 ... first alignment film 34 ... liquid crystal layer 35 ... second alignment film 36 ... second electrode 40 ... Spatial modulation system, 41 ... First VGA, 42 ... Second VGA, 43 ... First quarter wave plate (QWP), 44 ... Second QWP 45 ... PBS, 50 ... spatial modulation system, 51 ... first VGA, 52 ... second VGA, 53 ... third VGA, 54 ... fourth VGA 55 ... first PBS 56 ... second PBS 57 ... third PBS 58 ... first QWP 59 ... second QWP 60 ... Spatial modulation system, 61 ... Acousto-optic (AO) element array, 70 ... Spatial modulation system, 71 ... SLM, 72 ... Polarizer, 80 ... Spatial modulation system, 81 ... No. 1 variable phase shifter (VR) array, 82 ... second VR array, 83 ... Wollaston prism (WP) array, 84 ... collimator lens, 85 ... SF, L _S ... Signal light, L _R ... Reference light, L _IN ... Incident light

Claims (18)

Signal light having a polarization component in which information is recorded by spatial modulation of at least one of phase and amplitude is generated as light divided by a + 1st order diffracted light, a −1st order diffracted light, or a birefringent prism, while a reference light is generated An irradiation light generation system that generates zero-order light corresponding to the + 1st-order diffracted light and the −1st-order diffracted light, or another light divided by the prism;
An irradiation system that records the information on the recording medium as a three-dimensional optical anisotropy distribution by irradiating the recording medium having photosensitivity with the signal light and the reference light;
With
The irradiation system includes a signal light reproduced from the recording medium when the reference light for reproducing the information is irradiated on the recording medium, and the reference light for reproducing the information transmitted through the recording medium. , The signal light generated as the light divided by the + 1st order diffracted light, the −1st order diffracted light, or the prism and the other light divided by the 0th order light or the prism so as to overlap in the image sensor the optical information recording apparatus which is configured to irradiate the generated and said reference light to said recording medium as a. Signal light having a polarization component in which information is recorded by spatial modulation of at least one of phase and amplitude is generated as light divided by a + 1st order diffracted light, a −1st order diffracted light, or a birefringent prism, while a reference light is generated An irradiation light generation system that generates zero-order light corresponding to the + 1st-order diffracted light and the −1st-order diffracted light, or another light divided by the prism;
An irradiation system that records the information on the recording medium as a three-dimensional optical anisotropy distribution by irradiating the recording medium having photosensitivity with the signal light and the reference light;
With
The irradiation light generation system forms a striped light pattern whose intensity changes in an integer period in the generation direction of the + 1st order diffracted light and the −1st order diffracted light in a unit region, thereby the + 1st order diffracted light and the -1 optical information recording apparatus which is configured to produce diffracted light. Signal light having a polarization component in which information is recorded by spatial modulation of at least one of phase and amplitude is generated as light divided by a + 1st order diffracted light, a −1st order diffracted light, or a birefringent prism, while a reference light is generated An irradiation light generation system that generates zero-order light corresponding to the + 1st-order diffracted light and the −1st-order diffracted light, or another light divided by the prism;
An irradiation system that records the information on the recording medium as a three-dimensional optical anisotropy distribution by irradiating the recording medium having photosensitivity with the signal light and the reference light;
With
The irradiation system includes a signal light reproduced from the recording medium when the reference light for reproducing the information is irradiated on the recording medium, and the reference light for reproducing the information transmitted through the recording medium. However, the signal light generated as the + 1st order diffracted light or the −1st order diffracted light and the reference light generated as the 0th order light are applied to the recording medium so as to overlap each other in the image sensor without passing through the optical element. the optical information recording apparatus which is configured to illuminate. Signal light having a polarization component in which information is recorded by spatial modulation of at least one of phase and amplitude is generated as light divided by a + 1st order diffracted light, a −1st order diffracted light, or a birefringent prism, while a reference light is generated An irradiation light generation system that generates zero-order light corresponding to the + 1st-order diffracted light and the −1st-order diffracted light, or another light divided by the prism;
An irradiation system that records the information on the recording medium as a three-dimensional optical anisotropy distribution by irradiating the recording medium having photosensitivity with the signal light and the reference light;
With
The irradiation light generation system converts the information into image information having a plurality of two-dimensional pixel regions whose pixel values regularly change in a direction corresponding to the generation direction of the + 1st order diffracted light and the −1st order diffracted light. And the signal light by spatially modulating the polarization state of the polarized light incident in the direction corresponding to the generation direction of the + 1st order diffracted light and the −1st order diffracted light with a modulation amount corresponding to the pixel value of the image information. and an optical information recording device that is configured to generate the reference beam. Signal light having a polarization component in which information is recorded by spatial modulation of at least one of phase and amplitude is generated as light divided by a + 1st order diffracted light, a −1st order diffracted light, or a birefringent prism, while a reference light is generated An irradiation light generation system that generates zero-order light corresponding to the + 1st-order diffracted light and the −1st-order diffracted light, or another light divided by the prism;
An irradiation system that records the information on the recording medium as a three-dimensional optical anisotropy distribution by irradiating the recording medium having photosensitivity with the signal light and the reference light;
With
The irradiation light generation system has a plurality of variable diffraction gratings arranged two-dimensionally, and has a specific direction in which the transmittance of each variable diffraction grating is inclined with respect to the arrangement direction of the plurality of variable diffraction gratings. the optical information recording apparatus which is configured to generate the signal light and the reference light by the spatial modulation of the incident polarized light by the optical element that changes the specific direction corresponding to the incident polarization there. The irradiation light generation system uses the real part and the imaginary part of two polarization components orthogonal to each other by a spatial modulation system including at least four of the optical elements having the plurality of variable diffraction gratings. The optical information recording apparatus according to claim 5 , wherein the optical information recording apparatus is configured to generate signal light on which the image information is recorded. The irradiation light generation system, an optical information recording apparatus according to any one of claims 1 to 5 arranged to generate a signal light recorded each information into two polarization components perpendicular to each other. Signal light having a polarization component in which information is recorded by spatial modulation of at least one of phase and amplitude is generated as light divided by a + 1st order diffracted light, a −1st order diffracted light, or a birefringent prism, while a reference light is generated An irradiation light generation system that generates zero-order light corresponding to the + 1st-order diffracted light and the −1st-order diffracted light, or another light divided by the prism;
An irradiation system that records the information on the recording medium as a three-dimensional optical anisotropy distribution by irradiating the recording medium having photosensitivity with the signal light and the reference light;
With
The irradiation light generation system, the phase and the amplitude of the spatial modulation by the polarization component real part and the imaginary part the optical information recording apparatus in which information each of which is configured to generate a recorded signal light to the. The irradiation light generation system said information, either configured to record the polarization components as image information of the image information or 3 or more values of the encoded binary claims 1 to 8 2. An optical information recording apparatus according to item 1. Signal light having a polarization component in which information is recorded by spatial modulation of at least one of phase and amplitude is generated as light divided by a + 1st order diffracted light, a −1st order diffracted light, or a birefringent prism, while a reference light is generated An irradiation light generation system that generates zero-order light corresponding to the + 1st-order diffracted light and the −1st-order diffracted light, or another light divided by the prism;
An irradiation system that records the information on the recording medium as a three-dimensional optical anisotropy distribution by irradiating the recording medium having photosensitivity with the signal light and the reference light;
With
The irradiation light generation system, an optical information recording apparatus that is configured the information using at least two spatial light modulator to record the polarization components. The irradiation light generation system, one of the claims 1 to 4 configured to record the information to the polarization component using a plurality of acousto-optic elements which are two-dimensionally arranged to correspond to a plurality of pixels An optical information recording apparatus according to claim 1. Signal light having a polarization component in which information is recorded by spatial modulation of at least one of phase and amplitude is generated as light divided by a + 1st order diffracted light, a −1st order diffracted light, or a birefringent prism, while a reference light is generated An irradiation light generation system that generates zero-order light corresponding to the + 1st-order diffracted light and the −1st-order diffracted light, or another light divided by the prism;
An irradiation system that records the information on the recording medium as a three-dimensional optical anisotropy distribution by irradiating the recording medium having photosensitivity with the signal light and the reference light;
With
The irradiation light generation system records the information in the polarization component using a plurality of variable phase shifters arranged two-dimensionally corresponding to a plurality of pixels, and the signal light is divided by the prism. while it generated as an optical information recording device that is configured to generate the reference light as a separate light separated by the prism. Signal light having a polarization component in which information is recorded by spatial modulation of at least one of phase and amplitude is generated as light divided by a + 1st order diffracted light, a −1st order diffracted light, or a birefringent prism, while a reference light is generated An irradiation light generation system that generates zero-order light corresponding to the + 1st-order diffracted light and the −1st-order diffracted light, or another light divided by the prism;
An irradiation system that records the information on the recording medium as a three-dimensional optical anisotropy distribution by irradiating the recording medium having photosensitivity with the signal light and the reference light;
With
The irradiation light generation system causes the polarization component in which the information is recorded by the spatial modulation of the reference light and the phase by causing linearly polarized light having a predetermined polarization direction to enter the spatial light modulator in an oblique direction. the optical information recording apparatus which is configured to generate the signal light having. An irradiation light generation system for generating reference light;
An irradiation system for irradiating the reference light onto a recording medium having photosensitivity and having information recorded as a three-dimensional optical anisotropy distribution;
Signal light generated as light corresponding to light divided from the recording medium by the reference light by a + 1st order diffracted light, a −1st order diffracted light, or a birefringent prism, and has at least one space of phase and amplitude The signal light having a polarization component in which the information is recorded as modulation, the 0th order light corresponding to the + 1st order diffracted light and the −1st order diffracted light, or the light corresponding to another light separated by the prism An imaging system for imaging in a state in which the reference light is superimposed;
An information reproducing system for reproducing the information based on the imaged signal light;
An optical information reproducing apparatus comprising: Signal light having a polarization component in which information is recorded by spatial modulation of at least one of phase and amplitude is generated as light divided by a + 1st order diffracted light, a −1st order diffracted light, or a birefringent prism, while a reference light is generated Generating as zero-order light corresponding to the + 1st order diffracted light and the −1st order diffracted light, or as another light divided by the prism;
Irradiating the photosensitive recording medium with the signal light and the reference light to record the information as a three-dimensional optical anisotropy distribution on the recording medium;
Have,
When the recording medium is irradiated with reference light for reproducing the information, signal light reproduced from the recording medium and the reference light for reproducing the information transmitted through the recording medium are received in the imaging device. The signal light generated as the light divided by the + 1st order diffracted light, the −1st order diffracted light, or the prism and the 0th order light or the light generated as another light divided by the prism so as to overlap each other An optical information recording method for irradiating the recording medium with reference light . Generating a reference beam;
Irradiating a recording medium having photosensitivity and recorded information as a three-dimensional optical anisotropy distribution with the reference light;
Signal light generated as light corresponding to light divided from the recording medium by the reference light by a + 1st order diffracted light, a −1st order diffracted light, or a birefringent prism, and has at least one space of phase and amplitude The signal light having a polarization component in which the information is recorded as modulation, the 0th order light corresponding to the + 1st order diffracted light and the −1st order diffracted light, or the light corresponding to another light separated by the prism Imaging with reference light superimposed,
Regenerating the information based on the imaged signal light;
An optical information reproducing method. A plurality of variable diffraction gratings arranged two-dimensionally;
An optical element configured such that a transmittance of each variable diffraction grating is a specific direction inclined with respect to an arrangement direction of the plurality of variable diffraction gratings and changes in the specific direction according to incident polarized light. A first electrode;
A plurality of second electrodes arranged two-dimensionally;
Disposed between the first electrode and the plurality of second electrodes, and the said specific direction in response to the incident polarized light to a particular direction inclined with respect to the arrangement direction of the second electrode A liquid crystal layer whose thickness periodically changes at a period corresponding to each width of the plurality of second electrodes;
An optical element.