JP2007183506A - Information recording system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an information recording system where a high precision, complicated driving mechanism is made needless, and shift multiple recording can be achieved with a simple constitution. <P>SOLUTION: Regarding a light source device 1 in the information recording system, light emitted from a light source 32 is made incident on a half mirror 34. The light reflected by the half mirror 34 is introduced into a light emission part 33a via a shutter member 37. On the other hand, the light passed through the half mirror 34 is reflected by a reflection mirror 35, and is introduced into a light emission part 33b via a shutter member 37. At this time, by driving each shutter member 37 so as to be ON/OFF by a driving part 38, the emission of the light from each light emission part 33 is controlled, and the emission position of the light emitted from the light source device 1 changes. Since the plurality of light emission parts 33a, 33b are located on a face conjugated with the recording face in a recording medium, by changing the emission position of the light from the light source device 1, while shifting an interference image, its recording on the recording medium is made possible. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an information recording apparatus that records an interference image on a recording surface of a recording medium by causing information light and reference light to interfere with each other.

  Conventionally, various apparatuses for recording information as an interference image on a recording surface of a recording medium or reproducing information recorded as an interference image have been proposed. For example, FIGS. 16A and 16B are perspective views schematically showing the configuration of the main part of the apparatus described in Non-Patent Document 1. FIG.

  In this apparatus, when information is recorded, a pattern 101a for information light is displayed at the center of an SLM (Spatial Light Modulator) 101, while a pattern 101b for reference light is displayed at the periphery as shown in FIG. The SLM 101 is irradiated with laser light from a light source (not shown). Then, the SLM 101 emits information light (light at the center of the laser light) and reference light (light at the periphery of the laser light). These lights are converged by the objective lens 102 and condensed on the recording surface of the recording medium 103. At this time, information (interference image) is recorded in the state of interference fringes on the recording surface due to interference between the information light and the interference light.

  On the other hand, at the time of reproducing information, as shown in FIG. 5B, only the same reference light pattern 101b as that at the time of recording is displayed on the SLM 101, and laser light from a light source is irradiated. In this case, only the reference light is emitted from the SLM 101 and irradiated onto the recording medium 103 via the beam splitter 104 and the objective lens 102. Then, light having information recorded as interference fringes is reproduced from the recording medium 103. The reproduction light returns to the objective lens 102, changes its direction by the beam splitter 104, and is received by the light receiving element 105. The light receiving element 105 detects the reproduced image as a two-dimensional image.

Hideyoshi Horie et al., Holographic media nearing takeoff, realized 200 GB in 2006, Nikkei Electronics, Nikkei BP, January 17, 2005, No. 891, p. 105-114

  By the way, when information is recorded on a recording medium using the holographic technique as described above, for example, interference fringes are multiplexed and recorded by a so-called shift multiple recording method in which the recording medium is shifted by a minute amount for each interference fringe recording. As a result, the recording capacity of the recording medium can be increased.

  However, in order to realize such shift multiplex recording, conventionally, it has been necessary to provide a highly accurate and complicated drive mechanism for shifting a recording medium by a minute amount.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide information that can realize shift multiplex recording with a simple configuration without providing a highly accurate and complicated drive mechanism. It is to provide a recording apparatus.

  An information recording apparatus according to the present invention includes a light source device that emits coherent light, a portion of the light emitted from the light source device, and emits information light having information to be recorded on a recording medium. A modulation means for modulating the remainder of the light as necessary and emitting it as reference light; and a Fourier transform optical system for guiding the light emitted from the modulation means to the recording medium, the information light and the reference An information recording apparatus for recording an interference image on a recording surface of the recording medium by causing interference with light, wherein the light source device includes at least one light source, a plurality of light emitting units, and a light source from the light source. An optical element group that guides light to each light emitting unit; and a control unit that performs ON / OFF control of light supply from the light source to each light emitting unit, wherein the plurality of light emitting units are conjugated with the recording surface. It is located on a flat surface There. In addition, as said optical element group, the combination of a half mirror and a reflective mirror can be assumed, for example, and as said control means, the combination of a shutter member and its drive part can be assumed, for example.

  According to said structure, a part of coherent light radiate | emitted from a light source device is modulated by a modulation means, and is radiate | emitted as information light. On the other hand, the remainder of the light is modulated as necessary by the modulation means and emitted as reference light. These lights are irradiated onto the recording medium via a Fourier transform optical system, and an interference image is recorded on the recording surface by mutual interference of the lights.

  Here, in the light source device described above, light emitted from at least one light source is guided to each light emitting unit via the optical element group, and is emitted from the device to the outside. At this time, the light emission position from the light source device can be changed by controlling the ON / OFF of the light supply from the light source to each light emitting unit. That is, the light emission part from which light is emitted can be switched. On the other hand, since the plurality of light emitting portions are located on a plane conjugate with the recording surface of the recording medium, the position of each light emitting portion (each emitting position) and the interference image recorded on the recording surface of the recording medium Is in a one-to-one correspondence relationship.

  Therefore, by changing the emission position of the light from the light source device under the control of the control means, it is possible to record on the recording medium while shifting the interference image. As a result, shift multiplex recording can be realized without providing a complicated mechanism for moving the recording medium with high accuracy.

  In particular, if the control unit performs ON / OFF control of the light supply from the light source to each light emitting unit so that light is emitted from a different light emitting unit for each recording of the interference image on the recording medium. It becomes possible to record on the recording medium while shifting the interference image with certainty.

  In the present invention, it is desirable that the plurality of light emitting portions are arranged at a pitch equal to or smaller than the size of the interference image. In this case, by changing the emission position of light from the light source device under the control of the control means, it is possible to record a plurality of interference images that are gradually shifted so that adjacent interference images overlap. . Therefore, shift multiplex recording can be realized easily and reliably.

  In the present invention, the modulation means modulates the light incident on one area and radiates it as the information light when the incident area of the light emitted from the light source device is divided into two, while the other area You may comprise the light modulation element which modulates the light which injects into an area | region as needed, and radiate | emits it as the said reference light. In this case, the information light and the reference light can be obtained even if the modulation means is composed of one light modulation element, and the modulation means can be realized with a simple structure.

  Further, in the present invention, the modulation means is composed of a light modulation element and an optical element provided corresponding to each area when the incident area of the light emitted from the light source device is divided into two, The light modulation element modulates light incident on one of the incident areas and emits the information light, and the optical element emits light incident on the other area of the incident area as the reference light. It may be configured to.

  In this configuration, two members, ie, a light modulation element and an optical element (for example, an LC shutter for a transmission type and a reflection mirror for a reflection type) are required as modulation means. Also, an inexpensive one can be used, and the modulation means can be configured at a low cost.

  At this time, it is desirable that the light modulation element and the optical element are provided corresponding to individual areas when the incident area is divided into two by a plane including the optical axis of the Fourier transform optical system. In this case, the light modulation element and the optical element can be disposed adjacent to each other with the above-mentioned surface as a boundary, and the arrangement is facilitated.

  According to the present invention, the reading surface receives light reproduced from the recording medium when the recording medium is irradiated with the same reference light as the reference light irradiated to the recording medium when the interference image is recorded. Thus, the information processing apparatus may further include a reading unit that reads information recorded as the interference image, and the reading surface of the reading unit may be positioned on a conjugate plane with the light emitting surface of the modulation unit. . As the reading means, for example, a CMOS image sensor and a control unit can be considered. As the reading surface, for example, the light receiving surface of the image sensor can be considered.

  According to the above configuration, since the reading surface of the reading means is located on the conjugate plane with the light emitting surface of the modulating means, the light reproduced from the recording medium by irradiation of the reference light is applied to the reading surface of the reading means. When the light is received, the reading means can reproduce and read out the image displayed on the light emitting surface (display surface) of the modulating means from the interference image recorded on the recording surface of the recording medium.

  In the present invention, the modulation means can modulate a part of the light emitted from the light source device according to the search information and emit the light, and the reading means is searched by the modulation means. From the recording medium including the correlation calculation result between the Fourier image of the light and the interference image of the recording medium when the recording medium is irradiated with light modulated according to information via the Fourier transform optical system. The reproduction light may be received by the reading surface.

  According to the above configuration, the reading unit determines whether or not desired information is recorded on the recording medium based on the reproduction light (light including the correlation calculation result) from the recording medium received by the reading surface. (Search).

  In the present invention, the modulation means may be configured as a reflection type. The reflection type modulation means may be, for example, a single reflection type light modulation element (for example, LCD, DMD) or a combination of a reflection type light modulation element and a reflection mirror. According to such a configuration, for example, compared with the case where a light modulation element such as a transmissive LCD is used as the modulation means, the light utilization efficiency can be increased by increasing the aperture ratio of the light modulation element. , Low cost.

  In the present invention, the Fourier transform optical system includes an illumination optical system that guides light emitted from the light source device to the modulation means, and a recording optical system that guides light emitted from the modulation means to the recording medium. And a readout optical system that guides reproduction light from the recording medium to the readout means.

  In this case, since one Fourier transform optical system also serves as three optical systems (illumination optical system, recording optical system, and readout optical system), the configuration of the apparatus can be simplified and the apparatus can be made compact. .

  In the present invention, when the recording medium is disposed on one side with respect to the surface including the optical axis of the Fourier transform optical system, the light source device is disposed on the other side with respect to the surface. May be. In this case, when the Fourier transform optical system is divided into two (image height division) on the above surface, one can be used as the illumination optical system, and the other can be used as the recording optical system and the readout optical system. Therefore, it is possible to reliably use the three optical systems with one Fourier transform optical system.

  Further, in the present invention, each light emitting portion of the light source device is located on the same plane as the recording surface of the recording medium, and an interference image recorded on the recording medium includes each light emitting portion and the above-described recording surface. The recording may be performed at a position that is point-symmetric with respect to the optical axis. In this case, the interference image can be multiplex-recorded by changing the emission position of the light from the light source device by the control means.

  The present invention further includes a polarization separation element that transmits or reflects incident light according to its polarization state, and the polarization separation element is disposed in an optical path of light from the modulation means toward the Fourier transform optical system. It may be a configuration.

  According to the above configuration, for example, the outgoing light (for example, P-polarized light) from the modulation means can be transmitted through the polarization separation element and guided to the Fourier transform optical system. Further, light (for example, S-polarized light) reproduced from the recording medium and incident on the polarization separation element via the Fourier transform optical system can be reflected by the polarization separation element and guided to the reading unit. As described above, since a part of the optical path from the modulation means to the reading means via the recording medium is bent by the polarization separation element, the entire optical system can be compactly accommodated.

  According to the present invention, the light emitting position from the light source device can be changed by the control means performing ON / OFF control of the light supply from the light source to each light emitting portion. On the other hand, since the plurality of light emitting portions are located on a plane conjugate with the recording surface of the recording medium, the position of each light emitting portion and the position of the interference image recorded on the recording surface of the recording medium are one. It becomes a one-to-one correspondence. Therefore, by changing the emission position of the light from the light source device under the control of the control means, it is possible to record on the recording medium while shifting the interference image. As a result, shift multiplex recording can be realized without providing a complicated mechanism for moving the recording medium with high accuracy.

[Embodiment 1]
An embodiment of the present invention will be described below with reference to the drawings.
(1. Configuration of information recording apparatus)
FIG. 2 is an explanatory diagram showing a schematic configuration of the information recording apparatus according to the present embodiment. This information recording apparatus includes a light source device 1, an illumination optical system 2, a PBS (polarizing beam splitter) 3, a modulation unit 4, a quarter wavelength plate 5, a Fourier transform optical system 6, and a reading unit 7. It has.

  The light source device 1 emits coherent light, and emits, for example, S-polarized light. Details of the light source device 1 will be described later. The illumination optical system 2 converts the light emitted from the light source device 1 into parallel light and emits it. The PBS 3 is a polarization separation element that transmits or reflects incident light according to its polarization state. In this embodiment, the PBS 3 transmits P-polarized light and reflects S-polarized light. The PBS 3 is disposed in the optical path of light traveling from the light source device 1 to the modulation means 4 and in the optical path of light traveling from the modulation means 4 to the Fourier transform optical system 6.

  The modulation means 4 modulates a part of the light emitted from the light source device 1 and emits it as information light having information to be recorded on the recording medium 8, and emits the rest of the light as reference light. . More specifically, the modulation unit 4 modulates the light incident on one region 4a when the incident region of the light emitted from the light source device 1 is divided into two by the plane including the optical axis of the Fourier transform optical system 6 to thereby Light emitted as information light and incident on the other region 4b is emitted as the reference light.

  In the present embodiment, the modulation means 4 is composed of a reflective light modulation element having a plurality of pixels in a matrix. As the reflection type light modulation element, for example, a reflection type LCD or DMD (Digital Micromirror Device; manufactured by Texas Instruments Inc., USA) can be used. Therefore, the modulation unit 4 can two-dimensionally display information to be recorded on the recording medium 8 as page data, and emit light including information included in the page data as information light.

  A reflection type light modulation element has a higher aperture ratio than a transmission type light modulation element, and can be obtained at low cost. Therefore, by configuring the modulation means 4 as a reflection type as described above, it is possible to increase the light utilization efficiency and to configure the modulation means 4 at a low cost.

  In this embodiment, as will be described later, an interference image is recorded on the recording surface of the recording medium 8 by causing the information light emitted from the modulation means 4 and the reference light to interfere with each other. The means 4 may modulate the light incident on the other region 4b and emit it as the reference light. When the information recorded on the recording medium 8 is reproduced, it is necessary to irradiate the recording medium 8 with the same reference light as the reference light used at the time of recording. Therefore, by using the modulated reference light at the time of recording, the information can be easily reproduced. The recorded information on the recording medium 8 can be prevented from being reproduced. That is, the security of information recorded on the recording medium 8 can be improved. Therefore, it can be said that the modulation means 4 may modulate the light incident on the other region 4b out of the light emitted from the light source device 1 as necessary.

  The quarter-wave plate 5 converts linearly polarized light (for example, P-polarized light) incident from the modulation unit 4 via the PBS 3 into circularly polarized light, and converts circularly polarized light incident from the recording medium 8 via the Fourier transform optical system 6. The linearly polarized light is converted into linearly polarized light (for example, S-polarized light) whose polarization directions are orthogonal. The Fourier transform optical system 6 performs Fourier transform on the light emitted from the modulation means 4 and guides it to the recording medium 8, and is composed of a plurality of lenses.

  The reading means 7 uses, on the reading surface, light reproduced from the recording medium 8 when the recording medium 8 is irradiated with the same reference light as the reference light irradiated to the recording medium 8 when the interference image is recorded on the recording medium 8. By receiving the light, the information recorded as the interference image is read out, and is composed of, for example, a CMOS type image sensor and a control unit.

  In the present embodiment, the modulation unit 4 can modulate and emit a part of the light emitted from the light source device 1 according to the search information. When the light modulated in accordance with the search information by the modulation means 4 is applied to the recording medium 8 via the Fourier transform optical system 6, the reading means 7 reads the Fourier image of the light and the interference image of the recording medium 8. The reproduction light from the recording medium 8 including the correlation calculation result is received by the reading surface.

(2. Operation)
Next, the operation of the information recording apparatus having the above configuration will be described. First, the operation of the information recording apparatus when information is recorded on the recording medium 8 (hereinafter simply referred to as recording time) will be described with reference to FIG. In the present embodiment, the recording medium 8 is a reflection type.

  Light (for example, S-polarized light) emitted from the light source device 1 is converted into parallel light by the illumination optical system 2, reflected by the PBS 3, and incident on the modulation unit 4. In the modulation means 4, the light incident on one region 4a is modulated and emitted as information light, while the light incident on the other region 4b is reflected as it is and emitted as reference light. Information light and reference light (both P-polarized light) emitted from the modulation means 4 are incident on the PBS 3 and transmitted therethrough, converted into circularly polarized light by the quarter-wave plate 5, and Fourier transformed by the Fourier transform optical system 6. After the conversion, the recording surface of the recording medium 8 is irradiated and condensed. On the recording surface of the recording medium 8, the interference information image is recorded by the interference between the irradiated information light and the reference light.

  Here, FIGS. 3A and 3B are explanatory views schematically showing regions in which interference images are recorded on the recording medium 8. In the recording medium 8, the reflective layer 12, the recording layer 13, and the protective layer 14 are sequentially formed on the substrate 11. Information light and reference light are incident from the protective layer 14 side, and the recording layer 13 By interference, an interference image is recorded in the state of interference fringes 21 on the recording layer 13. At this time, when the information light incident from the protective layer 14 side is reflected by the reflective layer 12 and then interferes with the reference light, the reference from the protective layer 14 toward the reflective layer 12 as shown in FIG. Interference fringes 21a are recorded on the recording layer 13 in the optical path of light. On the other hand, when the reference light incident from the protective layer 14 side is reflected by the reflective layer 12 and interferes with the information light, the information light traveling from the protective layer 14 toward the reflective layer 12 as shown in FIG. The interference fringes 21b are recorded on the recording layer 13 in the optical path.

  FIG. 4 is an explanatory diagram schematically showing an optical path of light during recording in the information recording apparatus of the present embodiment. As a result of the above-described operation, the optical path of the emitted light from the light source device 1 corresponding to the information light and the information light emitted from the modulation means 4 is L1 in the figure. On the other hand, the optical path of the emitted light from the light source device 1 corresponding to the reference light and the reference light emitted from the modulating means 4 is L2 in the figure.

  Next, the operation of the information recording apparatus at the time of reproduction of information recorded on the recording medium 8 (hereinafter simply referred to as reproduction) will be described with reference to FIG.

  Light (for example, S-polarized light) emitted from the light source device 1 is converted into parallel light by the illumination optical system 2, reflected by the PBS 3, and incident on the modulation unit 4. Here, the light incident on one region 4a of the modulation means 4 is not modulated by the modulation means 4 and is not emitted in the direction of the PBS 3. On the other hand, the light incident on the other region 4b of the modulation means 4 is reflected as it is and emitted as reference light. That is, the reference light is the same light as that used during recording. The reference light (P-polarized light) emitted from the modulation means 4 enters the PBS 3 and passes therethrough, is converted into circularly-polarized light by the quarter-wave plate 5, and passes through the Fourier transform optical system 6 to the recording medium 8. The recording surface is irradiated and condensed. Then, light having information recorded as an interference image (hereinafter also referred to as reproduction light) is reproduced from the recording surface of the recording medium 8.

  Here, when the reference light is applied to the interference fringes 21a shown in FIG. 3A, the information light that interferes with the reference light at the same time as the reference light, that is, reflected by the reflective layer 12 is reflected. Since the information light after the reproduction is reproduced from the interference fringe 21a, the reproduction light from the interference fringe 21a is emitted in a direction opposite to the incident direction of the reference light upon reproduction on the recording medium 8. When the reference light is irradiated to the interference fringe 21b shown in FIG. 3B, that is, the reference light incident from the protective layer 14 side and reflected by the reflective layer 12 is irradiated to the interference fringe 21b. In this case, the information light that interferes with the reference light at the same time as the reference light, that is, the information light incident from the protective layer 14 side is reproduced from the interference fringe 21b. Therefore, the reproduced light from the interference fringe 21b is The light is reflected by the reflective layer 12 and emitted in the direction opposite to the incident direction of the reference light during reproduction with respect to the recording medium 8. That is, both the reproduction lights from the interference fringes 21a and 21b are emitted in a direction opposite to the incident direction of the reference light at the time of reproduction with respect to the recording medium 8.

  Therefore, the reproduction light obtained from the recording medium 8 enters the Fourier transform optical system 6 again, where it is subjected to inverse Fourier transform, and the polarization direction is orthogonal to that when the recording medium 8 is irradiated by the quarter wavelength plate 5. It is converted into s-polarized light in the direction, reflected by PBS 3 and incident on reading means 7. In the reading means 7, the information recorded as an interference image on the recording medium 8 is read by receiving the reproduction light from the recording medium 8 on the reading surface.

  FIG. 5 is an explanatory diagram schematically showing an optical path of light during reproduction in the information recording apparatus of the present embodiment. As a result of the above-described operation, the light paths of the light emitted from the light source device 1 corresponding to the reference light, the reference light emitted from the modulation unit 4, and the reproduction light from the recording medium 8 are L3 in FIG.

  Next, the operation of the information recording apparatus when searching for information recorded on the recording medium 8 (hereinafter simply referred to as searching) will be described with reference to FIG.

  Light (for example, S-polarized light) emitted from the light source device 1 is converted into parallel light by the illumination optical system 2, reflected by the PBS 3, and incident on the modulation unit 4. Here, the light incident on one area 4a of the modulation means 4 is modulated by the modulation means 4 in accordance with the search information and emitted as search light, but the light incident on the other area 4b is modulated. It is not emitted in the direction of PBS3. Light (P-polarized light) emitted from the modulation means 4 enters the PBS 3 and passes therethrough, is converted into circularly polarized light by the quarter-wave plate 5, and is Fourier-transformed by the Fourier transform optical system 6 to be recorded on the recording medium. No. 8 recording surface is irradiated and condensed. Then, light including the correlation calculation result between the Fourier image of the irradiated search light and the interference image of the recording medium 8 is reproduced from the recording surface of the recording medium 8. Note that the reproduction direction of the light at the time of retrieval is opposite to the incident direction of the information light at the time of recording on the recording medium 8 based on the same principle as that described above at the time of reproduction.

  Therefore, the light obtained from the recording medium 8 enters the Fourier transform optical system 6 again, where it is subjected to inverse Fourier transform, and the direction in which the polarization direction is orthogonal to that when the recording medium 8 is irradiated by the quarter wavelength plate 5. Is reflected by the PBS 3 and enters the reading means 7. The reading means 7 receives the light from the recording medium 8 on the reading surface, and determines (searches) whether or not desired information is recorded on the recording medium 8 based on the correlation calculation result of the light. It becomes possible to do.

  FIG. 6 is an explanatory diagram schematically showing an optical path of light at the time of searching in the information recording apparatus of the present embodiment. As a result of the above operation, the optical path of the light emitted from the light source device 1 corresponding to the light for search, the light for search emitted from the modulation means 4, and the light obtained from the recording medium 8 is L4 in FIG. It becomes.

  For example, in FIG. 2, a shutter may be provided on the light emission side of the modulation means 4 in correspondence with the optical paths of the information light and the reproduction light during recording. Further, a shutter may be provided on the light incident side of the reading means 7 corresponding to the optical path of the incident light on the reading surface during reproduction and retrieval. In such a configuration, for example, at the time of reproduction and search, the shutter located in the optical path other than the light necessary for light reception on the reading surface of the reading means 7 is turned off to prevent stray light from entering the reading surface. It is possible to prevent errors during playback and search.

  For example, in FIG. 2, the positional relationship between the modulating means 4 and the reading means 7 with respect to the PBS 3 may be reversed. However, in this case, the polarization state of the light emitted from the light source device 1 needs to be opposite to that of the present embodiment (that is, P-polarized light).

(3. Positional relationship of each component)
Next, before describing the details of the light source device 1 described above, the positional relationship of main components in the information recording apparatus of the present embodiment will be described.

  FIG. 7 is an explanatory diagram showing the optical path developed in the information recording apparatus of the present embodiment. In the information recording apparatus of this embodiment, since the above-described operation is performed, the modulation unit 4 is illuminated from the light source surface of the light source device 1 to the information display surface (light incident surface and light emission surface) of the modulation unit 4. An illumination system is configured, and a recording system for recording information on the recording medium 8 is configured from the information display surface of the modulation means 4 to the recording surface of the recording medium 8, and reading means is provided from the recording surface of the recording medium 8. It can be said that up to 7 reading surfaces (light receiving surfaces) constitute a reading system for reading information recorded on the recording medium 8.

  The light source surface of the light source device 1 refers to a light emission surface, and more specifically, a surface to which an emission position of a light emission unit 33 (see FIG. 1) described later belongs. The recording surface of the recording medium 8 is the same as the recording layer 13 shown in FIGS.

  In the recording system, the front focal point of the Fourier transform optical system 6 is located on the information display surface of the modulation means 4, and the rear focal point of the Fourier transform optical system 6 is located on the recording surface of the recording medium 8. . In the readout system, the front focal point of the Fourier transform optical system 6 is located on the recording surface of the recording medium 8, and the rear focal point of the Fourier transform optical system 6 is located on the readout surface of the readout means 7. Yes. Note that FL in FIG. 7 indicates the focal length of the Fourier transform optical system 6. Further, the light source surface of the light source device 1 and the recording surface of the recording medium 8 are in an equal magnification and conjugate positional relationship, and the information display surface of the modulation means 4 and the reading surface of the reading means 7 are in a conjugate positional relationship.

  Since the reading surface of the reading means 7 is positioned on the conjugate plane with the information display surface of the modulating means 4, the light reproduced from the recording medium 8 by receiving the reference light is received by the reading surface of the reading means 7. Sometimes, the reading means 7 can reproduce and read the image displayed on the information display surface of the modulation means 4 from the interference image recorded on the recording surface of the recording medium 8.

(4. Details of light source device)
Next, the details of the light source device 1 which is the most characteristic part of the present invention will be described. FIG. 1A is a plan view schematically showing a schematic configuration of the light source device 1 of the present embodiment, and FIG. 1B is a front view of the light source device 1 from the light emitting side.

  The light source device 1 includes a light source 32, a light emitting unit 33, a half mirror 34, a reflection mirror 35, and a control unit 36 in a housing 31. The light source 32 emits coherent light. The light emitting unit 33 is an emitting unit that emits the light emitted from the light source 32 to the outside of the housing 31. In the present embodiment, as illustrated in FIG. A plurality of surfaces are provided on the PBS3 side. That is, the light emission portions 33 have different light emission positions.

  In FIGS. 2A and 2B, two light emitting portions 33 are provided. When it is particularly desired to distinguish between them, one is a light emitting portion 33a and the other is a light emitting portion 33b. Moreover, the number of the light emission parts 33 is not necessarily limited to this, and may be three or more. Moreover, each light emission part 33 may be comprised with the glass window.

The plurality of light emitting portions 33 are arranged at a pitch equal to or smaller than the size of the interference image (interference fringes) recorded on the recording medium 8. Here, the minimum size of the recorded interference image is determined by the pixel pitch d (μm) of the modulation means 4, the focal length f (mm) of the Fourier transform optical system 6, and the wavelength λ (nm). That is, as shown in FIG. 8, when the minimum radius of the interference image is r (μm), r can be expressed as follows using d, f, and λ.
r = f · (λ / d)
For example, if f = 5 (mm), λ = 532 (nm), and d = 30 (μm), then r = 89 (μm), and the minimum size of the recorded interference image is 2r, that is, 178 (μm).

On the other hand, when the numerical aperture of the Fourier transform optical system 6 is NA and the thickness of the substantially recorded portion (recording layer 13) of the recording medium 8 excluding the substrate 11 and the protective layer 14 is t (μm), the recording is performed. The maximum size R of the interference image in the medium 8 is expressed as follows.
R = r + t · NA
For example, when NA = 0.5 and t = 300 (μm), R = 239 (μm), and the maximum size of the recorded interference image is 2R, that is, 478 (μm). Therefore, in this case, the plurality of light emitting portions 33 may be arranged at a pitch of, for example, 400 μm which is equal to or smaller than the maximum size of the interference image.

  The half mirror 34 and the reflection mirror 35 are an optical element group that guides the emitted light from the light source 32 to each light emitting unit 33. More specifically, the half mirror 34 separates the light emitted from the light source 32 into two light beams, reflects one of them and guides it to the corresponding light emitting part 33a, and transmits the other to the reflecting mirror 35. The reflection mirror 35 totally reflects the light transmitted through the half mirror 34 and guides it to the corresponding light emitting portion 33b. In addition, when three or more light emission parts 33 are provided, the half mirror 34 should just be provided corresponding to each light emission part 33 to add. That is, the total number of optical elements (half mirror 34 and reflection mirror 35) constituting the optical element group may be equal to the total number of light emitting portions 33.

  The control means 36 performs ON / OFF control of the light supply from the light source 32 to each light emitting section 33, and includes a plurality of shutter members 37 and a driving section 38 that drives the shutter members 37. Each shutter member 37 is composed of, for example, a liquid crystal shutter or a mechanical shutter, and is provided in an optical path between the half mirror 34 or the reflection mirror 35 and the corresponding light emitting portion 33. Each shutter member 37 transmits (ON) or blocks (OFF) light from the light source 32 obtained via the half mirror 34 or the reflection mirror 35 according to drive control of the drive unit 38.

Next, the effect by the said structure of the light source device 1 is demonstrated.
Light emitted from the light source 32 enters the half mirror 34. The light reflected by the half mirror 34 is guided to the light emitting portion 33a through the shutter member 37. On the other hand, the light transmitted through the half mirror 34 is reflected by the reflection mirror 35 and guided to the light emitting part 33 b via the shutter member 37.

  At this time, each shutter member 37 is driven ON / OFF by the driving unit 38, whereby the emission of light from each light emitting unit 33 is controlled. That is, if the shutter member 37 corresponding to the light emitting portion 33a is turned on and the shutter member 37 corresponding to the light emitting portion 33b is turned off, only light obtained from the light source 32 via the half mirror 34 passes through the shutter member 37. The light is transmitted and emitted from the light emitting portion 33a. On the other hand, when the shutter member 37 corresponding to the light emitting portion 33a is turned off and the shutter member 37 corresponding to the light emitting portion 33b is turned on, only light obtained from the light source 32 via the reflection mirror 35 passes through the shutter member 37. The light is transmitted and emitted from the light emitting portion 33b. Thus, the emission position of the light emitted from the light source device 1 is changed by the ON / OFF drive of each shutter member 37.

  Here, FIG. 9 is an explanatory diagram schematically showing optical paths of light emitted from each of the plurality of light emitting units 33 of the light source device 1 in the information recording apparatus of the present embodiment. FIG. 10 is a sectional view of the recording medium 8 on which interference fringes 21 (interference images) are recorded in the information recording apparatus. In FIG. 10, illustration of layers other than the recording layer 13 is omitted.

  As described above, since the plurality of light emitting portions 33 are located on the surface conjugate with the recording surface (recording layer 13) of the recording medium 8, as shown in FIG. There is a one-to-one correspondence between (each emission position) and the position (recording position) of the interference fringe 21 recorded on the recording surface of the recording medium 8. Therefore, by changing the emission position of light from the light source device 1 under the control of the control means 36 described above, it is possible to record on the recording medium 8 while shifting the interference fringes 21 as shown in FIG. . As a result, shift multiplex recording can be realized without providing a complicated mechanism for moving the recording medium 8 with high accuracy as in the prior art.

  That is, in the present embodiment, the recording position of the interference image 21 on the recording medium 8 is changed by ON / OFF driving of each shutter member 37 in the light source device 1, and the recording medium 8 is changed when the recording position is changed. A conventional mechanical drive mechanism to be moved is completely unnecessary. Therefore, shift multiplex recording can be realized without providing such a mechanical drive mechanism.

  At this time, supply of light from the light source 32 to each light emitting portion 33 is turned on / off by each shutter member 37 so that light is emitted from a different light emitting portion 33 for each recording of the interference fringe 21 to the recording medium 8. When the OFF control is performed, it is possible to record on the recording medium 8 while shifting the interference fringes 21 with certainty.

  Moreover, in this embodiment, since the several light emission part 33 is arrange | positioned with the pitch below the magnitude | size of the interference fringe 21, the light emission position from the light source device 1 by the said control of the control means 36, ie, By switching the light emitting unit 33 that emits light to the outside of the housing 31, as shown in FIG. 10, a plurality of interference fringes 21 are gradually shifted and recorded so that adjacent interference fringes 21 overlap. It becomes possible. Therefore, shift multiplex recording can be realized easily and reliably.

  In the above, the example in which the light source device 1 has one light source 32 has been described. However, if an optical element such as a reflection mirror 35 is added as necessary, a plurality of light sources 32 can be arranged. It is. Therefore, it can be said that the light source device 1 only needs to include at least one light source 32.

  By the way, the light source device 1 described above may have the following configuration. FIG. 11A is an explanatory diagram illustrating another configuration example of the light source device 1, and FIG. 11B is a front view from the light emitting side of the light source device 1. In the light source device 1, in addition to the configurations of FIGS. 1A and 1B, an optical path bending member such as a half mirror 39 is disposed in the optical path between the shutter member 37 and the light emitting portion 33. .

  The half mirror 39 is disposed so as to transmit light traveling from the shutter member 37 toward the light emitting portion 33a while reflecting light traveling from the adjacent shutter member 37 toward the light emitting portion 33b. As described above, by arranging the half mirror 39 in the optical path between the shutter member 37 and the light emitting portion 33, the distance between the adjacent light emitting portions 33a and 33b can be determined from the configuration shown in FIGS. Can also be narrowed. As a result, when the light emission position from the light source device 1 is changed under the control of the control means 36, it is possible to record on the recording medium 8 while shifting the interference fringes 21 more finely.

  In the above, switching of the optical path at the time of recording information on the recording medium 8 has been described. However, at the time of reproduction and retrieval, reproduction and retrieval can be performed by switching the optical path in the same manner as described above. .

(5. Supplementary items (1))
In the present embodiment, the example in which the modulation unit 4 is configured by a reflection type light modulation element has been described. However, the modulation unit 4 may be configured by a transmission type light modulation element (for example, a transmission type LCD). In this case, the light source device 1 and the illumination optical system 2 may be arranged on the side opposite to the PBS 3 with respect to the modulation means 4.

  In the present embodiment, the example in which the modulation unit 4 is configured by one light modulation element has been described. That is, one light modulation element modulates the light incident on one region 4a (see FIG. 2) and emits it as information light, while the light incident on the other region 4b (see FIG. 2) is emitted as necessary. The example of modulating and emitting as reference light has been described. According to this configuration, since the information light and the reference light can be obtained with one light modulation element, the modulation unit 4 can be realized with a simple configuration.

  However, the modulation means 4 may be composed of two members, a light modulation element and an optical element. For example, FIG. 12 is an explanatory diagram illustrating another configuration example of the information recording apparatus. In the figure, a modulation means 4 is constituted by a reflection type light modulation element 41 (for example, a reflection type LCD) and a reflection mirror 42 as the optical element. The light modulation element 41 and the reflection mirror 42 are provided corresponding to each region when the incident region of the light emitted from the light source device 1 is divided into two. More specifically, the light modulation element 41 and the reflection mirror 42 are provided corresponding to each region when the incident region is divided into two by a plane including the optical axis of the Fourier transform optical system 6. The light modulation element 41 modulates light incident on one of the incident areas and emits it as information light, and the optical element 42 emits light incident on the other area of the incident area as reference light. To do.

  In this configuration, two members of the light modulation element 41 and the reflection mirror 42 are required as the modulation means 4. However, since the inexpensive reflection mirror 42 can be used as the optical element, the modulation means 4 is configured at low cost. be able to.

  Further, since the light modulation element 41 and the reflection mirror 42 are provided corresponding to the individual regions when the incident region is divided into two by the surface including the optical axis of the Fourier transform optical system 6, they are provided on the surface. Can be arranged adjacent to each other as a boundary, and the arrangement becomes easy.

  Even if the modulation means 4 is composed of two members, a transmissive light modulation element (for example, a transmissive LCD) and a transmissive optical element (for example, an LC (liquid crystal) shutter), the same effect as described above is obtained. Can be obtained.

(6. Supplementary items (2))
In the present embodiment, the case where the recording medium 8 to be used is a reflection type has been described. In other words, it is of course possible to apply the technical idea of the present invention that shift multiplex recording is performed on the transmission type recording medium 8 by switching the light emission position from the light source device 1.

(6-1. Other Configuration Examples of Information Recording Device)
When the recording medium 8 to be used is a transmissive type, the information recording apparatus can be configured as follows. FIG. 13 is an explanatory diagram showing still another configuration example of the information recording apparatus as an optical path diagram. In this information recording device, in the optical path between the light source device 51 and the recording surface of the transmission type recording medium 59, the illumination optical system 52, the modulation means 53, the quarter wavelength plate 54, A half mirror 55 (first optical element), a Fourier transform optical system 56, a quarter wavelength plate 57, and a polarization selective reflection element 58 (second optical element) are arranged. Further, in the optical path between the recording surface of the recording medium 59 and the reading surface of the reading means 65, the quarter wavelength plate 60, the half mirror 61 (third optical element), and Fourier transform optics are sequentially arranged from the recording surface side. A system 62, a quarter-wave plate 63, and a polarization selective reflection element 64 (fourth optical element) are arranged.

  Here, the light source device 51, the illumination optical system 52, the modulation means 53, and the Fourier transform optical system 56 have the same functions as the light source device 1, the illumination optical system 2, the modulation means 4, and the Fourier transform optical system 6 of FIG. have. However, the modulation means 53 is a transmission type. Further, the Fourier transform optical system 62 and the reading means 65 have the same functions as the Fourier transform optical system 6 and the reading means 7 of FIG.

  The quarter-wave plates 54, 57, 60, and 63 convert the incident light to linearly polarized light if it is linearly polarized light, and convert it to linearly polarized light if the incident light is linearly polarized light. The half mirrors 55 and 61 transmit half of the incident light and reflect the remaining half. The polarization selective reflection elements 58 and 64 have, for example, the characteristics of reflecting S-polarized light and transmitting P-polarized light, and are composed of, for example, a brightness enhancement film (DBEF).

  In this information recording apparatus, at the time of recording, light (information light, reference light) emitted from the light source device 51 is converted into parallel light by the illumination optical system 52 and enters the modulation means 53. Linearly polarized light (for example, P-polarized light) emitted from the modulation means 53 is converted into circularly polarized light by the quarter wavelength plate 54 and is transmitted through the half mirror 55. The light transmitted through the half mirror 55 is incident on the quarter-wave plate 57 via the Fourier transform optical system 56, where it is converted into linearly polarized light (for example, S-polarized light) and incident on the polarization selective reflection element 58. Since the S-polarized light is reflected by the polarization selective reflection element 58, the light incident on the polarization selective reflection element 58 is turned back there.

  The light reflected by the polarization selective reflection element 58 is converted into circularly polarized light by the quarter-wave plate 57 and then enters the half mirror 55 via the Fourier transform optical system 56, where the optical path is folded. The light reflected by the half mirror 55 enters the quarter-wave plate 57 via the Fourier transform optical system 56, where it is converted into linearly polarized light (for example, P-polarized light) and enters the polarization selective reflection element 58. . Since the polarization selective reflection element 58 transmits the P-polarized light, the light incident on the polarization selective reflection element 58 is transmitted therethrough and irradiated onto the recording medium 59.

  On the other hand, at the time of reproduction, light (reproduction light) emitted from the recording medium 59 is converted into circularly polarized light by the quarter-wave plate 60, and then ¼ via the half mirror 61 and the Fourier transform optical system 62. The light enters the wave plate 63, where it is converted into linearly polarized light (for example, S-polarized light) and then enters the polarization selective reflection element 64. Since the S-polarized light is reflected by the polarization selective reflection element 64, the light that has entered the polarization selective reflection element 64 is folded back there.

  The light reflected by the polarization selective reflection element 64 is converted into circularly polarized light by the quarter wavelength plate 63, then enters the half mirror 61 through the Fourier transform optical system 62, and is reflected there. The light reflected by the half mirror 61 enters the quarter-wave plate 63 via the Fourier transform optical system 62, where it is converted into linearly polarized light (for example, P-polarized light) and then enters the polarization selective reflection element 64. . Since the P-polarized light is transmitted through the polarization selective reflection element 64, the light incident on the polarization selective reflection element 64 is transmitted therethrough and received by the reading surface of the reading means 65.

  As described above, the information recording apparatus of FIG. 13 is provided with the optical elements (half mirror 55 and polarization selective reflection element 58) having two reflecting surfaces facing each other in the optical path between the modulation means 53 and the recording medium 59. And an optical element (half mirror 61, polarization selective reflection element) having two reflecting surfaces facing each other in the optical path between the recording medium 59 and the reading surface of the reading means 65. 64), and the optical axis (optical path) is turned back.

  In principle, the distance between the information display surface of the modulation means 53 and the recording surface of the recording medium 59 is required to be twice the focal length FL of the Fourier transform optical system 56. As described above, the information display surface and the recording surface are recorded. The distance between the information display surface and the recording surface can be set to 2FL or less by providing two reflecting members facing each other in the optical path between the information surface and the optical path. Similarly, the distance between the recording surface of the recording medium 59 and the reading surface of the reading means 65 is in principle required to be twice the focal length FL of the Fourier transform optical system 62. The distance between the recording surface and the reading surface can be set to 2FL or less by providing two reflecting members facing each other in the optical path between them to fold the optical path. Therefore, according to the configuration of the information recording apparatus, it is possible to reduce the overall size and size of the apparatus that can handle the transmissive recording medium 59.

(6-2. Still another configuration example of the information recording apparatus)
By the way, in the information recording apparatus of FIG. 13, when the light emitted from the modulation means 53 passes through the half mirror 55, the emitted light quantity (transmitted light quantity) from the half mirror 55 becomes 1/2 of the incident light quantity. In addition, when the light reflected by the polarization selective reflection element 58 is reflected by the half mirror 55, the amount of light emitted from the half mirror 55 (the amount of reflected light) is ½ of the amount of incident light. If it compares with the light quantity which injects into this, it will be 1/4. That is, a light amount loss occurs with respect to the light emitted from the light source device 51 and irradiated onto the recording surface of the recording medium 59.

  Therefore, in order to eliminate such light loss, the information recording apparatus may be configured as follows. FIG. 14 is an explanatory diagram showing still another configuration example of the information recording apparatus as an optical path diagram.

  In this information recording apparatus, in the optical path between the light source device 71 and the recording surface of the transmissive recording medium 77, the illumination optical system 72, the modulation means 73, the first reflecting member 74, A Fourier transform optical system 75 and a second reflecting member 76 are disposed. Further, in the optical path between the recording surface of the recording medium 77 and the reading surface of the reading means 81, a third reflecting member 78, a Fourier transform optical system 79, and a fourth reflecting member 80 are arranged in this order from the recording surface side. Has been.

  Here, the light source device 71, the illumination optical system 72, the modulation means 73, and the Fourier transform optical system 75 have the same functions as the light source device 1, the illumination optical system 2, the modulation means 4, and the Fourier transform optical system 6 of FIG. have. However, the modulation means 73 is a transmission type. Further, the Fourier transform optical system 79 and the reading unit 81 have the same functions as the Fourier transform optical system 6 and the reading unit 7 of FIG.

  The first reflecting member 74 has a so-called donut shape in which the vicinity of the center through which the optical axis passes is hollow, and has a transmissive region 74a and a reflective region 74b. The transmission region 74a corresponds to the hollow portion and transmits the light emitted from the modulation means 73. On the other hand, the reflection region 74b is a region where the surface facing the Fourier transform optical system 75 is a reflection surface, and is formed in a donut shape outside the optical axis with respect to the transmission region 74a. .

  The second reflective member 76 has a reflective region 76a and a transmissive region 76b. The reflection region 76a is a region in which the surface facing the Fourier transform optical system 75 is a reflection surface, and is formed in a substantially disk shape. The transmission region 76b is a region that transmits the light reflected by the reflection region 74b of the first reflection member 74 and guides it to the recording medium 77, and is located outside the optical axis with respect to the reflection region 76a. .

  The third reflection member 78 has a reflection region 78a and a transmission region 78b. The reflection region 78a is a region where the surface facing the Fourier transform optical system 79 is a reflection surface, and is formed in a substantially disk shape. The transmission region 78b is a region that transmits light (reproduction light) emitted from the recording medium 77, and is located outside the optical axis with respect to the reflection region 78a.

  The fourth reflecting member 80 has a so-called donut shape in which the vicinity of the center through which the optical axis passes is hollow, and has a transmissive region 80a and a reflective region 80b. The transmission region 80 a corresponds to the hollow portion and transmits light reflected by the third reflection member 78. On the other hand, the reflective region 80b is a region where the surface facing the Fourier transform optical system 79 is a reflective surface, and is formed in a donut shape outside the optical axis with respect to the transmissive region 80a. .

  According to the above configuration, at the time of recording, light (information light, reference light) emitted from the light source device 71 is converted into parallel light by the illumination optical system 72 and is incident on the modulation unit 73. Of the light emitted from the modulation means 73, the light transmitted through the transmission region 74a of the first reflection member 74 is incident on the second reflection member 76 via the Fourier transform optical system 75, and is reflected by the reflection region 76a. Reflected. Then, the reflected light from the reflective region 76a enters the first reflective member 74 via the Fourier transform optical system 75 and is reflected by the reflective region 74b. Reflected light from the reflective region 74 b enters the second reflective member 76 via the Fourier transform optical system 75, passes through the transmissive region 76 b, and is irradiated onto the recording medium 77.

  On the other hand, during reproduction, light (reproduction light) emitted from the recording medium 77 passes through the transmission region 78 b of the third reflection member 78 and enters the fourth reflection member 80 via the Fourier transform optical system 79. Reflected by the reflection region 80b. Then, the reflected light from the reflective region 80b enters the third reflective member 78 via the Fourier transform optical system 79 and is reflected by the reflective region 78a. Reflected light from the reflective region 78 a enters the fourth reflective member 80 via the Fourier transform optical system 79, passes through the transmissive region 80 a, and is received by the readout surface of the readout means 81.

  As described above, the information recording apparatus shown in FIG. 14 has a configuration in which the optical path is folded back without using an optical element that leads to light loss such as a half mirror, so that the light from the light source device 71 is effectively used without causing light loss. It can be used, and the entire apparatus can be made compact and small.

  In addition, you may give curvature to each reflective surface of the 1st reflective member 74, the 2nd reflective member 76, the 3rd reflective member 78, and the 4th reflective member 80 which were mentioned above. In addition, the first reflecting member 74 and the fourth reflecting member 80 are also used, the second reflecting member 76 and the third reflecting member 78 are also used, and the Fourier transform optical systems 75 and 79 are also used. Thus, even if the recording medium 77 is a reflection type, it is possible to cope with it.

[Embodiment 2]
The following will describe another embodiment of the present invention with reference to the drawings. For convenience of explanation, the same components as those in the first embodiment are denoted by the same member numbers, and the description thereof is omitted.

  FIG. 15A is an explanatory diagram showing a schematic configuration of the information recording apparatus according to the present embodiment. In this information recording apparatus, the arrangement of the light source device 1 is different from that of the first embodiment, so that one Fourier transform optical system 6 is divided into three optical systems: an illumination optical system, a recording optical system, and a reading optical system. There is the biggest feature in the point that it was made to share in. Based on this point, the information recording apparatus of this embodiment will be described.

  The information recording apparatus of this embodiment includes a light source device 1, a PBS 3, a modulation unit 4, a quarter wavelength plate 5, and a Fourier transform optical system 6. When the recording medium 8 is disposed on one side with respect to the plane including the optical axis of the Fourier transform optical system 6, the light source device 1 is symmetrical with the recording medium 8 on the other side with respect to the plane. Is arranged. Each light emitting portion 33 of the light source device 1 is located on the same plane as the recording surface of the recording medium 8.

  In the present embodiment, the PBS 3 is configured, for example, in a plate shape, and is disposed in an optical path of light from the modulation unit 4 toward the Fourier transform optical system 6. The modulation means 4 includes a reflection type light modulation element 41 (for example, a reflection type LCD) and a reflection mirror 42 as an optical element. That is, the modulation means 4 is a reflection type. The light modulation element 41 and the reflection mirror 42 correspond to individual areas when the incident area of the light emitted from the light source device 1 in the modulation means 4 is divided into two on the plane including the optical axis of the Fourier transform optical system 6. Is provided.

  The Fourier transform optical system 6 serves as an illumination optical system, a recording optical system, and a readout optical system. Here, the illumination optical system is an optical system (lens group) that guides the light emitted from the light source device 1 to the modulation unit 4, and the recording optical system records the light emitted from the modulation unit 4. An optical system (lens group) that leads to the medium 8, and the reading optical system is an optical system (lens group) that guides reproduction light from the recording medium 8 to the reading means 7.

  The reading unit 7 includes a first image sensor 91 (for example, a CMOS image sensor) and a second image sensor 92 (for example, a CMOS image sensor) that are arranged adjacent to each other. The first image sensor 91 receives light reproduced from the recording medium 8 through the Fourier transform optical system 6 during reproduction, that is, irradiation of the reference light from the modulation unit 4. On the other hand, the second image sensor 92 receives the information recorded on the recording medium 8 and the search light obtained from the recording medium 8 when searching, that is, when the search light from the modulation unit 4 is irradiated. Light including a correlation calculation result with the information it has is received via the Fourier transform optical system 6.

Next, operations during recording, reproduction, and search will be described in order.
At the time of recording, the light emitted from the light source device 1 enters the modulation means 4 via the Fourier transform optical system 6. In the modulation means 4, the light incident on the light modulation element 41 is modulated there and emitted as information light. On the other hand, the light incident on the reflection mirror 42 of the modulation means 4 is reflected there and emitted as reference light.

  Light emitted from the modulation means 4 (for example, P-polarized light) passes through the PBS 3 and is converted into circularly polarized light by the quarter-wave plate 5, and then the recording surface of the recording medium 8 through the Fourier transform optical system 6. Irradiated and condensed. On the recording surface of the recording medium 8, the interference information image is recorded by the interference between the irradiated information light and the reference light.

  Here, FIG. 15B is a plan view schematically showing each light emitting portion 33 of the light source device 1 and the interference image 93 recorded on the recording medium 8. In the present embodiment, the light source device 1 is positioned symmetrically with the recording medium 8 with respect to the plane including the optical axis of the Fourier transform optical system 6, and each light emitting portion 33 of the light source device 1 is a recording medium. 8 is located on the same plane as the recording surface 8, the interference image 93 recorded on the recording medium 8, as shown in FIG. It is recorded at a position that is point-symmetric with respect to the axis. Therefore, the interference image 93 can be multiplex-recorded on the recording surface of the recording medium 8 by switching the light emission position of the light source device 1.

  At the time of reproduction, the light emitted from the light source device 1 enters the modulation means 4 via the Fourier transform optical system 6. In the modulation means 4, the light incident on the light modulation element 41 is not modulated and is not emitted in the direction of the PBS 3. On the other hand, the light incident on the reflection mirror 42 of the modulation means 4 is reflected there and emitted as the same reference light as that at the time of recording. Reference light (for example, P-polarized light) emitted from the modulation means 4 is transmitted through the PBS 3 and converted into circularly polarized light by the quarter-wave plate 5, and then the recording surface of the recording medium 8 through the Fourier transform optical system 6. Irradiated and condensed. Then, light (reproduction light) having information recorded as the interference image 93 is reproduced from the recording surface of the recording medium 8.

  The reproduction light obtained from the recording medium 8 is incident again on the Fourier transform optical system 6, where it is subjected to inverse Fourier transform, and the polarization direction is orthogonal to that when the recording medium 8 is irradiated by the quarter wavelength plate 5. It is converted to S-polarized light, reflected by PBS 3 and incident on reading means 7. In the reading means 7, the first image sensor 91 receives the reproduction light from the recording medium 8 on the reading surface, so that information recorded as the interference image 93 on the recording medium 8 is read.

  At the time of search, the light emitted from the light source device 1 enters the modulation means 4 through the Fourier transform optical system 6. In the modulation means 4, the light incident on the light modulation element 41 is modulated according to the search information and emitted as search light. On the other hand, the light incident on the reflection mirror 42 of the modulation means 4 is reflected there, but is not necessary at the time of retrieval, and is therefore shielded by a shutter member (not shown) provided on the light emission side of the reflection mirror 42, for example.

  Search light (for example, P-polarized light) emitted from the modulation means 4 is transmitted through the PBS 3 and converted into circularly polarized light by the quarter-wave plate 5 and then Fourier-transformed by the Fourier transform optical system 6 and recorded. The recording surface of the medium 8 is irradiated and condensed. Then, light including a correlation calculation result between the Fourier image of the irradiated search light and the interference image 93 of the recording medium 8 is reproduced from the recording surface of the recording medium 8.

  The light obtained from the recording medium 8 enters the Fourier transform optical system 6 again, where it is subjected to inverse Fourier transform, and S in the direction in which the polarization direction is orthogonal to that when the recording medium 8 is irradiated by the quarter wavelength plate 5. It is converted into polarized light, reflected by PBS 3 and incident on reading means 7. In the reading means 7, the second imaging element 92 receives light from the recording medium 8 on the reading surface, and a control unit (not shown) applies to the recording medium 8 based on the correlation calculation result of the light. It is determined (searched) whether or not desired information is recorded.

  As described above, in this embodiment, since one Fourier transform optical system 6 also serves as three optical systems (illumination optical system, recording optical system, and readout optical system), it corresponds to each of the above optical systems. Compared with the case where the Fourier transform optical system 6 is provided, the configuration of the apparatus can be simplified and the apparatus can be made compact. Further, the reading means 7 receives light obtained from the recording medium 8 through the same Fourier transform optical system 6 during reproduction and search, so that the reading means 7 and the first image sensor 91 of the reading means 7 It becomes possible to arrange the second image sensor 92 side by side, and positioning them easily.

  In the present embodiment, the light source device 1 is disposed on the side opposite to the side on which the recording medium 8 is disposed with respect to the plane including the optical axis of the Fourier transform optical system 6. Thereby, when the Fourier transform optical system 6 is divided into two (image height division) on the above surface, one can be used as an illumination optical system, and the other can be used as a recording optical system and a readout optical system. Accordingly, the three Fourier transform optical systems 6 can reliably use the three optical systems.

  In the present embodiment, the PBS 3 is disposed in the optical path of the light from the modulation unit 4 toward the Fourier transform optical system 6, so that the light emitted from the light source device 1 can be directly transmitted via the Fourier transform optical system 6 ( It can be incident on the modulation means 4 (without being incident on the PBS 3). In addition, the outgoing light (for example, P-polarized light) from the modulation means 4 is transmitted through the PBS 3 and guided to the Fourier transform optical system 6, while the light incident on the PBS 3 from the recording medium 8 via the Fourier transform optical system 6 (for example, S-polarized light can be reflected by the PBS 3 and guided to the reading means 7. Accordingly, since a part of the optical path from the modulation means 4 to the reading means 7 via the recording medium 8 can be bent by the PBS 3, the entire optical system can be compactly accommodated.

  Of course, the information recording apparatus can be configured by appropriately combining the configurations described in the above embodiments.

(A) is a top view which shows typically the structure of the outline of the light source device in the information recording device which concerns on one Embodiment of this invention, (b) is the front view from the light emission side of the said light source device. It is. It is explanatory drawing which shows the schematic structure of the said information recording device. (A) And (b) is explanatory drawing which shows typically the area | region where an interference image is recorded in a recording medium. In the said information recording device, it is explanatory drawing which shows typically the optical path of the light at the time of recording. In the said information recording device, it is explanatory drawing which shows typically the optical path of the light at the time of reproduction | regeneration. In the said information recording device, it is explanatory drawing which shows typically the optical path of the light at the time of a search. It is explanatory drawing which expand | deploys and shows the optical path in the said information recording device. It is sectional drawing of the recording layer of the said recording medium. In the said information recording device, it is explanatory drawing which shows typically the optical path of the light radiate | emitted from each of the several light emission part of the said light source device. It is sectional drawing of the recording medium with which an interference fringe is recorded in the said information recording device. (A) is explanatory drawing which shows the other structural example of the said light source device, (b) is a front view from the light-projection side of the said light source device. It is explanatory drawing which shows the other structural example of the said information recording device. It is explanatory drawing which shows the other structural example of the said information recording device as an optical path diagram. It is explanatory drawing which shows the other structural example of the said information recording device as an optical path diagram. (A) is explanatory drawing which shows the schematic structure of the information recording device which concerns on other embodiment of this invention, (b) is each light-emitting part and recording medium of the light source device in the said information recording device. It is a top view which shows typically the interference image recorded. (A) And (b) is a perspective view which shows typically the structure of the principal part of the conventional information recording device.

Explanation of symbols

1 Light source device 3 PBS (polarization separation element)
4 Modulating means 6 Fourier transform optical system 7 Reading means 8 Recording medium 21 Interference fringes (interference image)
32 Light source 33 Light emitting part 34 Half mirror (optical element group)
35 Reflective mirror (optical element group)
36 Control means 37 Shutter member (control means)
38 Drive unit (control means)
41 Light modulation element (modulation means)
42 Reflection mirror (optical element, modulation means)
93 Interference image

Claims (13)

A light source device that emits coherent light;
Modulating means for modulating a part of the light emitted from the light source device and emitting it as information light having information to be recorded on a recording medium, and modulating the remainder of the light as necessary to emit as reference light When,
An information recording system comprising: a Fourier transform optical system that guides light emitted from the modulation means to the recording medium, and records an interference image on a recording surface of the recording medium by causing the information light and the reference light to interfere with each other A device,
The light source device is
At least one light source;
A plurality of light emitting portions;
An optical element group for guiding the light from the light source to each light emitting portion;
Control means for ON / OFF control of the supply of light from the light source to each light emitting unit,
The information recording apparatus, wherein the plurality of light emitting portions are located on a surface conjugate with the recording surface.   The control unit performs ON / OFF control of light supply from the light source to each light emitting unit so that light is emitted from a different light emitting unit for each recording of an interference image on the recording medium. The information recording apparatus according to claim 1.   The information recording apparatus according to claim 1, wherein the plurality of light emitting units are arranged at a pitch equal to or smaller than the size of the interference image.   When the incident area of the light emitted from the light source device is divided into two, the modulation means modulates the light incident on one area and emits it as the information light, while requiring the light incident on the other area The information recording apparatus according to claim 1, wherein the information recording apparatus is configured by a light modulation element that modulates in response to the light and emits the light as the reference light. The modulation means is composed of a light modulation element and an optical element provided corresponding to each area when the incident area of light emitted from the light source device is divided into two,
The light modulation element modulates light incident on one of the incident regions and emits the information light,
4. The information recording apparatus according to claim 1, wherein the optical element emits light incident on the other area of the incident area as the reference light.   6. The light modulation element and the optical element are provided corresponding to individual areas when the incident area is divided into two by a plane including the optical axis of the Fourier transform optical system. The information recording device described in 1. When the recording medium is irradiated with the same reference light as the reference light applied to the recording medium when the interference image is recorded, the reading surface receives the light reproduced from the recording medium, thereby obtaining the interference image. It further comprises a reading means for reading the recorded information,
7. The information recording apparatus according to claim 1, wherein the reading surface of the reading unit is located on a conjugate surface with a light emitting surface of the modulating unit. The modulating means is capable of modulating and emitting a part of light emitted from the light source device according to search information,
When the light modulated in accordance with the search information by the modulation means is irradiated onto the recording medium via the Fourier transform optical system, the reading means has a Fourier image of the light and an interference image of the recording medium. 8. The information recording apparatus according to claim 7, wherein reproduction light including the correlation calculation result is received by a reading surface.   9. The information recording apparatus according to claim 7, wherein the modulation means is configured as a reflection type. The Fourier transform optical system is
An illumination optical system for guiding the light emitted from the light source device to the modulation means;
A recording optical system for guiding the light emitted from the modulation means to the recording medium;
10. The information recording apparatus according to claim 9, wherein the information recording apparatus also serves as a reading optical system that guides reproduction light from the recording medium to the reading means.   When the recording medium is disposed on one side with respect to the surface including the optical axis of the Fourier transform optical system, the light source device is disposed on the other side with respect to the surface. The information recording apparatus according to claim 10. Each light emitting part of the light source device is located on the same surface as the recording surface of the recording medium,
The information recording apparatus according to claim 11, wherein the interference image recorded on the recording medium is recorded at a position that is point-symmetric with respect to each light emitting portion and the optical axis. A polarization separation element that transmits or reflects incident light according to its polarization state;
The information recording apparatus according to claim 1, wherein the polarization separation element is disposed in an optical path of light from the modulation unit toward the Fourier transform optical system.

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