JP2006317886A - Hologram recording reproducing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simplify an optical system in an entire hologram recording reproducing apparatus of a multi-angle system by employing a method of varying an incident angle of reference light to a hologram recording material by varying angles of the reference light. <P>SOLUTION: The hologram recording reproducing apparatus reproduces data by steps of: irradiating a hologram recording material 50 with reference light 200 through a reference light optical system 40 upon reproducing; changing the propagation direction of the light transmitted through the hologram recording material 50 into an opposite direction by a phase conjugate reference light optical system composed of a lens 24 and a reflective mirror 25 to generate phase conjugate reproducing light; irradiating the hologram recording material 50 with the phase conjugate reproducing light to generate conjugate reproducing signal light; and guiding the reproducing signal light through a signal light optical system 22 and a PBS (polarization beam splitter) 21 to an image sensor 26. The phase conjugate reproducing light can be produced by the phase conjugate reference light optical system in a simple configuration and the optical system can be made compact. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a hologram recording / reproducing apparatus that records interference fringes of signal light and reference light on a recording material, and more particularly to a phase conjugate light reproducing system that uses the same optical system for both recording and reproduction.

  In recent years, there has been a holographic data storage system (hologram recording / reproducing apparatus) that records and reproduces a large amount of data by using a hologram technology for recording volume interference fringes between signal light and reference light spatially modulated by information on a hologram recording material. It has been proposed (see, for example, Non-Patent Document 1).

  FIG. 12 is a schematic diagram showing a conventional configuration of an angle multiplexing type hologram recording / reproducing apparatus. Coherent laser light emitted from the laser light source 1 is branched into signal light 100 and reference light 200 by an optical component (not shown). The signal light 100 is modulated by the data pattern displayed on the spatial modulator (SLM) 2, passes through the recording signal light optical system 401, and is collected on the hologram recording material 50. At this time, since the hologram recording material 50 is irradiated with the reference light 200 whose incident angle is adjusted by the rotating mirror 3, the signal light 100 interferes with the reference light 200, and the interference fringes are the same as those of the hologram recording material 50. Hologram multiplex recording is performed every time the incident angle of the reference beam 200 is changed in the region. At the time of reproduction, the hologram is reproduced by irradiating the hologram recorded on the hologram recording material 50 with the same reference light as that at the time of recording, and the reproduced light passes through the reproduction signal light optical system 402. The image is formed on the image sensor 4, and after photoelectric conversion, image processing is performed to reproduce data.

  In the conventional hologram recording / reproducing apparatus as described above, since the recording signal light optical system 401 and the reproducing signal light optical system 402 are separated, the entire optical system inevitably becomes large. Therefore, a method called a phase conjugate light reproduction method described below is known.

  FIG. 13 is a schematic view showing a conventional example of a hologram recording / reproducing apparatus of an angle multiplexing type and a phase conjugate light reproducing type. During recording, coherent laser light emitted from the laser light source 1 is branched into signal light 100 and reference light 200 by an optical component (not shown). The signal light 100 is modulated by the data pattern displayed on the spatial modulator (SLM) 2, and then passes through the polarization beam splitter (PBS) 5 and the recording signal light optical system / reproduction signal light optical system 400. Then, the light is focused on the hologram recording material 50. On the other hand, the reference light 200 is applied to the hologram recording material 50 after the incident angle with respect to the hologram recording material 50 is adjusted by the rotating mirror 3. Thereby, the signal light 100 interferes with the reference light 200, and the interference fringes are recorded on the hologram recording material 50. At this time, every time the incident angle of the reference light 200 is changed, the data is recorded on the hologram recording material. Multiple recording is performed in 50 identical areas. During recording, the hologram recording material 50 is irradiated with the reference light 200 using the recording reference light optical system 301 shown in FIG.

  At the time of reproduction, as shown in FIG. 14, the phase conjugate reference light is created from the reference light 200 through the reproduction reference light optical system 302 of FIG. 15, and this is recorded on the hologram from the opposite side to the surface on which the signal light 100 is incident. The material 50 is irradiated. Thereby, phase conjugate reproduction signal light (diffracted light) is generated from the hologram recording material 50, and this reproduction light passes through the recording signal light optical system / reproduction signal light optical system 400 and enters the polarization beam splitter 5. Here, the traveling direction is changed to a right angle and the image is formed on the image sensor 4. The phase conjugate reproduction signal light is photoelectrically converted by the image sensor 4 and then subjected to image processing to reproduce data. During reproduction, the hologram recording material 50 is irradiated with the reference light 200 using the reproduction reference light optical system 302 shown in FIG.

  In the phase conjugate light reproduction as described above, it is necessary to make the reference light in the direction opposite to that during recording incident on the recording signal light optical system / reproduction signal light optical system 400 during reproduction. Here, although expressed in the reverse direction, it can be expressed accurately as phase conjugate light or time-reversed light. In the figure, PBS (polarization beam splitter) is used to separate the optical path at the time of recording and at the time of reproduction. For this separation, a method of inserting a half-wave plate (not shown) into the optical path to change the polarization is also known. ing. However, in the conventional phase conjugate light reproduction, the phase conjugate reference light must be irradiated from the back side of the hologram recording material 50 during reproduction. For this purpose, a reproduction reference light optical system 302 as shown in FIG. Even if the optical system is simplified by using the recording signal light optical system 400 and the reproducing signal light optical system 400, if the reproduction reference light optical system 302 is required separately, the optical system of the entire apparatus is reduced in size. There is a problem that you can not.

Therefore, as shown in FIG. 16, the angle of the reference light 200 is fixed only by changing the path of the reference light 200 by the fixed reflecting mirror 41, and instead, the hologram recording material 50 is rotated as shown by the arrow in the figure. Then, the incident angle of the reference beam 200 to the hologram recording material 50 is relatively changed to perform recording / reproduction by angle multiplexing. Particularly in the case of reproduction, a reflection mirror 42 is arranged behind the hologram recording material 50, and the reference light transmitted through the hologram recording material 50 is reflected by the reflection mirror 42 to generate conjugate reproduction light, which is recorded in the hologram recording. The reproduction signal light is obtained by irradiation from behind the material 50. Thus, there is a known example in which it is not necessary to route the optical system as shown in FIG. 14 in order to generate conjugate reproduction light, and the optical system of the entire apparatus is miniaturized (see, for example, Patent Document 1).
JP 2002-123161 (5th page, FIG. 8) IBM J.RES DEVELOP VOL 44 NO.3 MAY 2000 `` Holographic data strage ''

  However, in the configuration in which the transmission reference light is reflected by the reflection mirror 42 behind the hologram recording material 50 and the phase conjugate reference light is generated, the reference light 200 is fixed. There is a problem that the configuration for generating the phase conjugate reference light using the reflection mirror 42 can be applied only to the angle multiplexing method to be changed.

  The present invention has been devised in view of the above circumstances, and an object of the present invention is to employ an angle multiplexing method employing a method of changing the angle of reference light to change the incident angle of the reference light on the hologram recording material. It is an object of the present invention to provide a phase conjugate light reproduction type hologram recording / reproducing apparatus capable of simplifying the optical system of the entire hologram recording / reproducing apparatus.

  In order to achieve the above object, the present invention condenses the spatially modulated recording signal light on the hologram recording material by the signal light optical system, and separately irradiates the hologram recording material with the recording reference light. Interference fringes between reference light and signal light during recording are recorded on the same hologram recording material, and phase conjugate reproduction is performed by irradiating the hologram recording material with phase conjugate reference light that travels in the opposite direction to the reference light during recording during reproduction. An angle-multiplexed hologram recording / reproducing apparatus that generates signal light and guides the phase conjugate reproduced signal light to an image sensor through the signal light optical system, and records the recording reference light on the hologram recording material during the reproduction. A phase conjugate reference light optical system that reverses the traveling direction of the recording reference light transmitted through the hologram recording material when irradiated through the same path as the time, and the phase The role reference light optical system generates the phase conjugate reproduction signal light that travels in the opposite direction of the recording reference light regardless of the incident angle of the recording reference light to the hologram recording material. Features.

  The phase conjugate reference light optical system further includes a polarization unit that polarizes the phase conjugate reproduction signal generated by the phase conjugate reference light optical system of the present invention.

  Further, the phase conjugate reference light optical system of the present invention includes a lens disposed at a position away from the hologram recording material by a focal length, and further a reflection mirror disposed at a position away from the lens by a focal length. It is characterized by comprising.

  As described above, in the hologram recording / reproducing apparatus of the present invention, the recording reference light is irradiated onto the hologram recording material through the same path as that at the time of recording at the time of reproduction, and at that time, the progress of the recording reference light transmitted through the hologram recording material. The phase conjugate reference light used for phase conjugate reproduction is created with the direction reversed by the phase conjugate reference light optical system. In this case, the phase conjugate reference light optical system refracts the reference light during transmission recording by a lens disposed at a position away from the hologram recording material by a focal length, and is further disposed at a position away from the lens by the focal length. Since the phase conjugate reference light is generated by reflecting by the reflecting mirror, the recording reference light transmitted through the hologram recording material is transmitted even if the incident angle of the recording reference light to the hologram recording material changes during reproduction. As parallel light, the light can be vertically incident on the reflection mirror, and conjugate reproduction of the angle multiplexing type hologram recording / reproducing apparatus can be realized. Further, it is not necessary to route the reference light optical system in order to produce the phase conjugate reference light, and the optical system can be miniaturized. Furthermore, the angle is changed according to the incident angle of the reference light. At this time, even if the incident angle of the reference light changes, a lens arranged at a position separated by the focal length, and further the focal length from this lens. Since the reflection mirrors arranged at positions apart from each other become parallel light and enter the reflection mirror perpendicularly, conjugate reference light can be generated regardless of changes in the incident angle of the reference light. Therefore, the present invention is most effective for a reference light angle variable type angle multiplexing apparatus.

  A λ / 4 plate, which is a polarizing means for polarizing a phase conjugate reproduction signal, is arranged in the phase conjugate reference light optical system, and the recording reference light transmitted through the hologram recording material is passed through the λ / 4 plate in the forward path. The polarization beam splitter (PBS) can be used even if the reflected light enters the signal light optical system, for example, even if the reflected light enters the signal light optical system. ), The course can be changed by 90 degrees so that it does not enter the image sensor, and a reproduced image with good S / N can be obtained.

According to the present invention, at the time of reproduction, the recording reference light is irradiated to the hologram recording material through the same path as at the time of recording, and at this time, the traveling direction of the recording reference light transmitted through the hologram recording material is opposite By providing a conjugate reference light optical system having a simple configuration for generating phase conjugate reference light used for phase conjugate reproduction, it is not necessary to route the reference light optical system in order to produce conjugate reference light. Therefore, the reference light optical system is simplified, the optical system can be greatly reduced in size, and an expensive optical system for generating phase conjugate reference light as conventionally known is not required. Significant price reduction is possible.
Furthermore, even if the incident angle of the reference light changes, the lens arranged at a position separated by the focal length and the reflection mirror arranged at a position separated from the lens by the focal length all become parallel light, Since the incident light is perpendicularly incident on the reflecting mirror, conjugate reference light can be generated regardless of changes in the incident angle of the reference light. Therefore, the present invention can be applied to a variable reference light angle type angle multiplexing apparatus. It is most effective for this.
In addition, a λ / 4 plate which is a polarization means for polarizing the phase conjugate reproduction signal is disposed in the phase conjugate reference light optical system, and the recording reference light transmitted through the hologram recording material is passed through the λ / 4 plate in the forward path. By polarizing 90 degrees, even if the reflected light enters the signal light optical system, the path can be changed by 90 degrees by the polarization beam splitter (PBS) so that it does not enter the image sensor. A reproduced image with good / N can be obtained. This λ / 4 plate changes the reference light during recording transmitted through the hologram recording material by 90 degrees so that the signal light and the reproduced signal light are orthogonal to each other. Therefore, adjustment required for the conventional reference light optical system is necessary and expensive. Since the λ / 2 plate can be eliminated, the optical system of the apparatus can be made inexpensive.

  The purpose of simplifying the optical system of the entire angle-multiplexed hologram recording / reproducing apparatus adopting the method of changing the incident angle of the reference light to the hologram recording material by changing the angle of the reference light is the reference light during recording during reproduction. Is easy to create conjugate reference light used for conjugate reproduction by irradiating the hologram recording material through the same path as during recording, with the traveling direction of the recording reference light transmitted through the hologram recording material in the opposite direction. This is easily realized by providing a conjugate reference light optical system having a simple structure.

  FIG. 1 is a block diagram showing a configuration of a hologram recording / reproducing apparatus according to the first embodiment of the present invention. The hologram recording / reproducing apparatus includes a laser light source 11, a half-wave plate (λ / 2 plate) 12, a polarization beam splitter (PBS) 13, a half-wave plate (λ / 2 plate) 14, a beam expander 15, and a rotating mirror 16. Lenses 17 and 18 constituting the optical optical system 40, a beam expander 19, a transmission type spatial modulator (SLM) 20, a polarization beam splitter (PBS) 21, a signal light optical system 22, an aperture 23, and a conjugate reference light optical system The rear lens 24, the reflection mirror 25, and the image sensor 26 are formed. The aperture 23 is an optical component that blocks high-order diffracted light of the SLM 20 during recording, and blocks unnecessary scattered light from the hologram recording material 50 and diffracted light from a hologram that does not need to be reproduced during reproduction. Indispensable for hologram storage. The half-wave plate 12 changes the intensity ratio between the signal light 100 and the reference light 200, and the half-wave plate 14 rotates the polarization plane of the reference light 200 90 degrees during recording and reproduction. In some cases, the plane of polarization of the signal light 100 is aligned to improve the coherence on the hologram recording material 50, and the plane of polarization is rotated 90 degrees during reproduction, so that the reproduced signal light is guided onto the image sensor 26 by the PBS 21. It is intended to make it happen.

  Next, the operation of this embodiment will be described. At the time of recording, the laser light emitted from the laser light source 11 passes through the half-wave plate 12 and its polarization plane is adjusted, and then is branched into the signal light 100 and the reference light 200 by the PBS 13. The signal light 100 is converted into parallel light by the beam expander 19, spatially modulated by the recording data displayed on the SLM 20, and then incident on the PBS 21, so that its path is changed by 90 degrees, and the signal light optical system 22, aperture The hologram recording material 50 is irradiated through 23. On the other hand, the reference light 200 passes through the half-wave plate 14 and becomes parallel light by the beam expander 15, and this is irradiated to the hologram recording material 50 through the reference light optical system 40 of the lenses 17 and 18 through the rotating mirror 16. Thereby, interference fringes between the signal light 100 and the reference light 200 are recorded on the hologram recording material 50.

  FIG. 2 is a diagram for explaining the above-described operation during recording in more detail. The incident reference light 200 is polarized at a desired angle by the rotating mirror 16, passes through the reference light optical system 40, and then interferes with the incident signal light 100 on the hologram recording material 50 to record a hologram. At this time, since the shutter 27 of the conjugate reference light optical system 30 is closed and light does not enter the lens 24 and the reflection mirror 25, normal hologram recording is performed.

At the time of reproduction, only the reference beam 200 is incident on the hologram recording material 50. FIG. 3 is a diagram for explaining the operation during reproduction in more detail. As in recording, the reference beam 200 is incident on the hologram recording material 50 through the rotary mirror 16 and the reference beam optical system 40. At this time, the reference beam 200 is polarized at a desired angle by the rotary mirror 16, and the reference beam optics is used. It passes through the system 40 and reaches the hologram recording material 50. At that time, diffracted light is generated by the hologram recorded in the hologram recording material 50, and this is directly reproduced signal light 601 and goes out of the conjugate reference light optical system 30. This reproduced signal light corresponds to so-called direct image reproduction, and is hereinafter referred to as direct reproduction signal light. In this embodiment, only the conjugate reproduction signal light 602 that comes out later is necessary, and this direct reproduction signal light 601 is not necessary. The direct reproduction signal light 601 can also be used as a signal for controlling the position of the hologram recording material 50.

  The reference light 200 that hits the hologram recording material 50 is partly directly reproduced signal light 601, but most of the reference light 200 passes through the hologram recording material 50 without being diffracted as it is, and the transmitted light 201 is a distance from the hologram recording material 50. After passing through a rear lens 24 having a focal length f at a position f away, the light is further condensed on a reflection mirror 25 at a position f. As can be seen from FIG. 3, the light that has passed through the hologram recording material 50 as parallel light is focused on the reflection mirror 25. Further, in the arrangement as shown in FIG. 3, the transmitted light 201 enters the reflecting mirror 25 vertically. The light 202 reflected by the reflecting mirror 25 travels in the opposite direction on the same path as the original path, and the light that has passed through the rear lens 24 is light having a traveling direction opposite to that of the original reference light 200, that is, conjugate reference. It becomes light 203. When this conjugate reference light 203 strikes the hologram recording material 50, conjugate reproduction signal light 602 is obtained based on the principle of conjugate reproduction, and this is generated in the opposite direction to the signal light at the time of recording. The light passes through the optical optical system 22, passes through the PBS 21, and forms an image on the image sensor 26. The conjugate reproduction signal light 602 is subjected to photoelectric conversion by the image sensor 26, and then subjected to image processing to become reproduction data.

  According to the present embodiment, at the time of reproduction, when the hologram recording material 50 is irradiated with the reference light 200 from the same direction as that at the time of recording, the transmitted light that has passed through the hologram recording material 50 is reflected by the reflection mirror 25 and conjugated. By generating the reference beam 203 and reproducing the recorded data of the hologram recording material 50 using the conjugate reference beam 203, there is no need for a reproduction reference beam optical system that draws the reference beam during reproduction. The apparatus can be miniaturized. Further, in the angle multiplexing method, the reference light 200 is changed in accordance with the incident angle with respect to the hologram recording material 50 at the time of recording at the time of reproduction. At this time, even if the incident angle of the reference light 200 is changed, the latter lens 24, all become parallel light and enter the reflecting mirror 25 perpendicularly, so that the conjugate reference light 203 can be generated regardless of the change in the incident angle of the reference light 200. This is effective for 200 angle variable type most practical angle multiplexing systems.

  FIG. 4 is a block diagram showing a configuration of a hologram recording / reproducing apparatus according to the second embodiment of the present invention. However, the same parts as those in the first embodiment shown in FIG. Since the spatial modulator (SLM) 29 of the hologram recording / reproducing apparatus of the present embodiment is a reflection type, the signal light becomes parallel light by the beam expander 19, and immediately passes through the PBS 21 and enters the SLM 29. Reflected after being spatially modulated by the displayed data. The path of the spatially modulated signal light is changed by 90 degrees in the PBS 21, and the hologram recording material 50 is irradiated through the signal light optical system 22 and the aperture 23. On the other hand, the reference light 200 is applied to the hologram recording material 50 through the reference light optical system 40 similar to that of the first embodiment. Thereby, interference fringes between the signal light 100 and the reference light 200 are recorded on the hologram recording material 50.

  During reproduction, when the hologram recording material 50 is irradiated with the reference light 200 from the same direction as during recording, the transmitted light that has passed through the hologram recording material 50 is reflected by the reflection mirror 25 to generate conjugate reference light, By irradiating from the back surface of the hologram recording material 50 using this conjugate reference light, conjugate reproduction signal light corresponding to the recording hologram of the hologram recording material 50 is generated, and this conjugate reproduction signal light is opposite to the signal light at the time of recording. The light passes through the aperture 23 and the signal light optical system 22 in the direction, passes through the PBS 21, and forms an image on the image sensor 26. The conjugate reproduction signal light is subjected to photoelectric conversion by the image sensor 26 and then subjected to image processing to become reproduction data.

  According to the present embodiment, even when the reflective SLM 29 is used, the conjugate reference light can be generated by the conjugate reference light generation optical system similar to the first embodiment, and the hologram can be reproduced. The same effect as that of the first embodiment can be obtained.

  FIG. 5 is a block diagram showing a configuration of a hologram recording / reproducing apparatus according to the third embodiment of the present invention. In the hologram recording / reproducing apparatus of this embodiment, the magnification conversion optical system 33 is inserted between the PBS 21 and the image sensor 26 when the display pixels of the SLM 29 and the light receiving pixels of the image sensor 26 do not have a one-to-one correspondence. The correspondence between the two pixels is adjusted. Other configurations are the same as those of the first embodiment, and the same effects can be obtained. Further, even if the magnification conversion optical system is inserted between the SLM 29 and the PBS 21, the same effect can be obtained.

  By the way, according to the first, second, and third embodiments described above, when an optical system is used, depending on the angle condition between the reference beam 200 and the hologram recording material 50, as shown in FIG. 50 surface reflected light 500 may overlap with the hologram image, which may reduce the SN ratio. Further, for example, in FIG. 1, since the hologram reproduction image is separated and detected by the PBS 21 at the time of reproduction, it is necessary to adjust the polarization of the reference light 200. Therefore, the reference light optical system is expensive and requires adjustment 1 There is also a problem that the / 2λ plate 14 must be inserted. Therefore, the embodiment described below has solved such a problem.

  FIG. 7 is a block diagram showing a configuration of a hologram recording / reproducing apparatus according to the fourth embodiment of the present invention. The hologram recording / reproducing apparatus includes a laser light source 11, a half-wave plate (λ / 2 plate) 12, a polarization beam splitter (PBS) 13, a beam expander 15, a rotating mirror 16, and a 4f lens constituting a reference light optical system 40. 17 and 18, a reflective spatial light modulator (SLM) 29, a polarization beam splitter (PBS) 21, a signal light optical system lens 22, an image sensor 26, a rear-stage lens 24 forming a conjugate reference light optical system, and a reflection mirror 25. The λ / 4 plate 28 is inserted between the rear lens 24 and the reflecting mirror 25.

  Next, the operation of this embodiment will be described. The operation of this embodiment is almost the same as that of the second embodiment shown in FIG. 4, but the differences will be described with reference to FIG. 8 which is a detailed view of the vicinity of the hologram recording material 50 shown in FIG. When reproducing a hologram, the angle of the optical path of the reference beam 200 whose polarization is linearly polarized in (1) is changed by the rotating mirror 16. Then, when the reference light 200 enters the hologram recording material 50 by passing through the 4f system (reference light optical system) constituted by the lens having the focal length f of (2), the hologram recording material 50 is made as shown in (3). Incident light is incident on the same spot as parallel light. When the reference light 200 is incident on the hologram recording material 50, both the light (9) reflected by the material surface and the light (4) transmitted are generated.

  First, in terms of transmitted light, the transmitted light passes through the lens 24 having a focal length f located at a distance f through the optical path (4). The transmitted light is reflected by the reflection mirror 25 located at a distance f from the lens 24, passes through the optical path (5), and is transmitted through the lens 24 again. Here, by passing through the lens 24 twice, a single lens can form a 4f system. Therefore, even if the angle of the reference light 200 incident on the recording material 50 is changed by the rotating mirror 16, the corresponding conjugate light (6 ) Can be obtained.

  Here, in the optical system of FIG. 8, unlike FIG. 4, a λ / 4 plate 28 is placed between the hologram recording material 50 and the reflection mirror 25. The polarization of the reference light 200 is changed to circularly polarized light by the λ / 4 plate 28, reflected by the reflection mirror 25, and then transmitted again through the λ / 4 plate 28, so that the conjugate light is orthogonal to the polarization of the reference light 200. It has a component that does. The conjugate light (6) having a polarization direction perpendicular to the reference light 200 conjugately reproduces the recorded hologram. The reproduction signal light (7) generated thereby has a polarization direction that passes through the PBS 21 after passing through the lens 22 constituting the signal light optical system. Therefore, the reproduction signal light (7) passes through the PBS 21 as shown in (8) and is detected by the image sensor 26.

  On the other hand, the reference light 200 reflected by the hologram recording material 50 changes depending on the position of the lens, the angle of the hologram recording material 50, the angle of the incident reference light 200, and the like, as shown in (9), to the lens 22 of the signal light optical system. An incident light beam is generated. However, since this light beam has a polarization direction orthogonal to the conjugate light, it is totally reflected by the PBS 21 and can be prevented from entering the image sensor 26 by passing through the optical path (10).

  According to this embodiment, since the polarization of the conjugate light is changed by 90 degrees by the λ / 4 plate 28 placed between the hologram recording material 50 and the reflection mirror 25, the reference light 200 at the hologram recording material 50 is changed. The reflected light has a polarization direction orthogonal to the conjugate light, so that even if the reflected light enters the signal light optical system, the path is changed by 90 degrees by the PBS 21 and passes through the optical path (10). Incident to the sensor 26 can be prevented, and a reproduced image with good S / N can be obtained. Further, since the polarization of the conjugate light is changed by 90 with the inexpensive and adjustment-free λ / 4 plate 28, the expensive and adjustment-necessary λ / 2 plate, which has been necessary for the optical path of the reference light 200 in the related art, becomes unnecessary. The price can be lowered. Other effects are the same as those of the second embodiment shown in FIG.

  FIG. 9 is a block diagram showing a configuration of a hologram recording / reproducing apparatus according to the fifth embodiment of the present invention. The configuration of the hologram recording / reproducing apparatus is substantially the same as that shown in FIG. 7, but the positional relationship between the PBS 13 and the laser light source 11 is changed, and the polarization directions of the signal light 100 and the reference light 200 are changed from those shown in FIG. As shown in the figure, the positional relationship between the image sensor 26 and the SLM 29 can be changed with respect to the PBS 21. However, the operation of the hologram recording / reproducing apparatus is the same as that of the fourth embodiment shown in FIG.

  FIG. 10 is a block diagram showing a configuration of a hologram recording / reproducing apparatus according to the sixth embodiment of the present invention. The configuration of the hologram recording / reproducing apparatus is almost the same as that shown in FIG. 7, but the SLM 20 is a transmission type, and the signal light 100 is incident on the PBS 21 through the SLM 20. However, the operation of the hologram recording / reproducing apparatus is the same as that of the fourth embodiment shown in FIG.

  FIG. 11 is a block diagram showing a configuration of a hologram recording / reproducing apparatus according to the seventh embodiment of the present invention. The hologram recording / reproducing apparatus is a shift multiplex type, and includes a laser light source 11, a half-wave plate (λ / 2 plate) 12, a polarization beam splitter (PBS) 13, a beam expander 15, a fixed mirror 30, and a lens constituting a reference light optical system. 32, a reflective spatial modulator (SLM) 29, a polarization beam splitter (PBS) 21, a signal light optical system lens 22, an image sensor 26, a rear lens 24 forming a conjugate reference light optical system, a reflective mirror 25, and a rear stage A λ / 4 plate 28 inserted between the lens 24 and the reflection mirror 25 is provided.

  According to the present embodiment, the configuration is the same as that of FIG. 7 except that the hologram recording material is moved slightly in the track direction to perform multiple recording, and the conjugate light is placed between the hologram recording material 50 and the reflection mirror 25. Since the polarization is changed by 90 degrees by the λ / 4 plate 28, the reflected light of the reference light 200 on the hologram recording material 50 has a polarization direction orthogonal to the conjugate light, so that the reflected light is compared with signal light optics, for example. Even if the system enters the system, the path is changed by 90 degrees by the PBS 21 to prevent the incident on the image sensor 26, and a reproduced image with a good S / N can be obtained. Other effects are also the same as those of the first embodiment shown in FIG.

  In addition, this invention is not limited to the said embodiment, In the range which does not deviate from the summary, it can implement also with another various form in a concrete structure, a function, an effect | action, and an effect. For example, the third embodiment described above can also be easily configured using the reflective SLM of the second embodiment.

1 is a block diagram showing a configuration of a hologram recording / reproducing apparatus according to a first embodiment of the present invention. It is a figure explaining the recording operation of the hologram recording / reproducing apparatus shown in FIG. It is a figure explaining the reproducing operation of the hologram recording / reproducing apparatus shown in FIG. It is the block diagram which showed the structure of the hologram recording / reproducing apparatus which concerns on the 2nd Embodiment of this invention. It is the block diagram which showed the structure of the hologram recording / reproducing apparatus which concerns on the 3rd Embodiment of this invention. FIG. 2 is a block diagram showing details in the vicinity of the hologram recording material shown in FIG. 1. It is the block diagram which showed the structure of the hologram recording / reproducing apparatus which concerns on the 4th Embodiment of this invention. FIG. 7 is a block diagram showing details in the vicinity of the hologram recording material shown in FIG. 6. It is the block diagram which showed the structure of the hologram recording / reproducing apparatus which concerns on the 5th Embodiment of this invention. It is the block diagram which showed the structure of the hologram recording / reproducing apparatus which concerns on the 6th Embodiment of this invention. It is the block diagram which showed the structure of the hologram recording / reproducing apparatus which concerns on the 7th Embodiment of this invention. 1 is a schematic diagram showing a conventional configuration of an angle multiplexing type hologram recording / reproducing apparatus. It is the schematic explaining the recording operation | movement of the hologram recording / reproducing apparatus of the conventional angle multiplexing system and conjugate light reproduction | regeneration system. It is the schematic explaining the reproduction | regeneration operation | movement of the hologram recording / reproducing apparatus of the conventional angle multiplexing system and conjugate light reproduction | regeneration system. FIG. 15 is a block diagram illustrating a configuration example of a reference light optical system at the time of recording and reproduction used in FIGS. 13 and 14. It is the block diagram which showed the structural example of the hologram recording / reproducing apparatus of the conventional angle multiplexing system and conjugate light reproduction | regeneration system.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Laser light source, 12, 14 ... Half-wave plate ((lambda) / 2 plate), 13, 21 ... Polarizing beam splitter (PBS), 15, 19 ... Beam expander, 16 ... Rotating mirror, 17, 18 ... Lens, 20, 29 ... Spatial modulator (SLM), 22 ... Signal light optical system, 23 ... Aperture, 24 ... Rear lens, 25 ... Reflective mirror, 26 ... Image sensor, 27 ... ... Shutter, 28 ... λ / 4 plate, 30 ... Conjugate reference light optical system, 33 ... Magnification conversion optical system, 40 ... Reference light optical system, 50 ... Hologram recording material.

Claims (8)

The spatially modulated signal light during recording is focused on the hologram recording material by the signal light optical system, and the reference light and the signal light during recording are separately irradiated by irradiating the hologram recording material with the reference light during recording. Interference fringes are recorded on the same hologram recording material, and at the time of reproduction, phase conjugate reference light traveling in a direction opposite to the recording reference light is irradiated to the hologram recording material to generate phase conjugate reproduction signal light, and this phase conjugate reproduction An angle multiplexing type hologram recording / reproducing apparatus for guiding signal light to an image sensor through the signal light optical system,
Phase conjugate reference light that reverses the traveling direction of the recording reference light that has passed through the hologram recording material when the recording reference light is irradiated onto the hologram recording material through the same path as during recording during the reproduction. With an optical system,
The phase conjugate reference light optical system generates the phase conjugate reproduction signal light that travels in the opposite direction of the recording reference light regardless of the incident angle of the recording reference light to the hologram recording material. Hologram recording / reproducing apparatus characterized by the above.   2. The hologram recording / reproducing apparatus according to claim 1, wherein the phase conjugate reference light optical system further comprises a polarization means for polarizing a phase conjugate reproduction signal generated by the phase conjugate reference light optical system.   3. The hologram recording / reproducing apparatus according to claim 2, wherein the polarization means is a λ / 4 plate that polarizes the recording reference light transmitted through the hologram recording material in an outward path.   The phase conjugate reference light optical system includes a lens disposed at a position separated from the hologram recording material by a focal length, and a reflection mirror disposed at a position separated from the lens by a focal length. The hologram recording / reproducing apparatus according to claim 1, wherein:     5. The hologram recording / reproducing apparatus according to claim 4, wherein a λ / 4 plate is disposed between the hologram recording material and the reflection mirror.   The hologram recording / reproducing apparatus according to claim 1, further comprising a magnification conversion optical system that adjusts a correspondence relationship between a display pixel of a spatial modulator that spatially modulates the signal light and a light receiving pixel of the imaging element.   2. The hologram recording / reproducing apparatus according to claim 1, wherein the spatial light modulator that spatially modulates the signal light is a transmission type.   2. The hologram recording / reproducing apparatus according to claim 1, wherein the spatial modulator for spatially modulating the signal light is a reflection type.

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