JP6525808B2 - Hologram recording medium multiplex recording and reproducing method and hologram recording medium multiplex recording and reproducing apparatus - Google Patents

Description

  The present invention relates to a hologram recording medium multiplex recording / reproducing method and a hologram recording medium multiplex recording / reproducing apparatus, and more specifically, a hologram recording medium multiplex recording / reproducing method and hologram recording capable of efficiently reproducing page data information multiplexed and recorded in a hologram. The present invention relates to a medium multiplex recording and reproducing apparatus.

  In recent years, hologram recording has attracted attention as a large-capacity and high-speed information recording and reproducing system. Hologram recording causes two coherent lights from the same light source called reference light and signal light to interfere, and records and holds the generated interference fringes on the recording medium as a change in refractive index. The signal light is spatially modulated by a two-dimensional data image called "page data" and irradiated to the recording medium through a lens. Since multiple page data can be multiplexed and recorded at the same location of the medium while changing the conditions of the reference light (for example, incident angle to the recording medium, wavelength, phase, etc.), high density and large capacity are realized Is possible. Various methods have been proposed so far, and among them, one that performs multiple recording and reproduction while changing the incident angle of the irradiation light is called an angular multiplexing method (see, for example, Patent Document 1).

For example, as shown in FIG. 7, in the recording / reproducing apparatus using the angle multiplexing method, a plurality of page data is recorded in the form of a hologram while changing the incident angle of the reference light to the recording medium 410 little by little by the galvano mirror 425. Do. At the time of reproduction, the reference light under the same conditions as when recording is applied to the recording medium 410 from the side opposite to the reference light irradiation direction at the time of recording (phase conjugate reproduction). The light is diffracted to obtain reproduced light. It is possible to read out the original information by photographing this with a camera 420 etc. and decoding (note that the reference numerals given to the respective members shown in FIG. 7 correspond to the respective ones in FIG. 2 ( Reference Example 1). It is what added 300 to the code | symbol attached | subjected to the member).

  By the way, in the angle multiplexing, the incident angle of the reference beam to the recording medium 410 is restricted within a certain range. This arises from the need to prevent physical interference from occurring when the signal light and the reference light are incident on the recording medium 410.

  In consideration of this restriction, for example, in the case where the incident angle of the reference beam to the recording medium 410 is within a variable range of 30 degrees and the angle interval for angle multiplexing is 0.2 degrees, 151 multiplexing is possible. Although recording density and recording capacity can be improved by angularly multiplexing more holograms to the same part of the recording medium 410, it is not always easy to significantly improve the angular multiplexing number due to problems such as crosstalk.

  By the way, when reproducing page data recorded in the hologram recording medium (410), the hologram recording medium (410) is irradiated with reference light which is set to a predetermined polarization angle by a half-wave plate (422) or the like disposed in the optical path. . When the reference light is incident on the hologram recording medium (410), it is diffracted by the hologram interference fringes, and the reproduction light carrying page data information is output. Thereafter, the reproduction light is incident on a camera (420) or the like, and the page data information is imaged by a two-dimensional imaging device such as a camera (420).

JP, 2006-154163, A

However, when increasing the amount of data per page data, the sensitivity of the camera increases with the increase in the number of pixels of the imaging device, the resolution of the pixels, and the increase in the number of pixels of the imaging device and the resolution of the pixels. And speeding up data transfer are needed.
Further, even in the case of improving the frame rate of the camera, it is necessary to increase the sensitivity of each pixel of the camera and to speed up data transfer.
As described above, in the conventional apparatus, the transfer speed of reproduction data has been limited by the performance of the camera. In this case, in order to improve the transfer rate of reproduction data, it is necessary to improve the function of the camera itself.

  On the other hand, in recent years, a photosensitive resin material (hereinafter referred to as a photopolymer) is widely used as a write-once recording medium. A medium based on photopolymer has advantages such as high multiplicity index and long-term stable data retention. However, in the case of photopolymer, a hologram (interference fringe) is recorded by causing a refractive index difference inside the recording medium. At this time, the medium shrinks due to photopolymerization. When a temperature difference occurs between signal recording and signal reproduction, the recording medium may be contracted or expanded due to the influence of the temperature difference. When the recording medium contracts or expands, so-called interference fringe distortion (hologram recording information distortion: hereinafter referred to as “hologram distortion”) occurs in which the interference fringes recorded in the medium are distorted.

Even if reference light similar to that at the time of recording is incident on the distorted interference fringes, it becomes difficult to reproduce the recorded bit data without error, and the SNR (Signal to Noise Ratio) of the reproduced data is lowered.
Therefore, a method of improving the SNR of reproduced data by optically compensating for hologram distortion has been considered. Specifically, it is a method of controlling the wavelength and incident angle of the reference light, and the wavefront.

However, the method of compensating for the hologram distortion based on the wavelength of the reference light and the incident angle is not sufficiently compensated when the NA of the lens in the signal light path becomes high due to the recent increase in the density of information recording.
Therefore, attention is focused on a method capable of compensating for the hologram distortion even when the NA of the lens is increased by optimizing the wavefront of the reference light.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and in a multiplexed recording hologram recording medium, it is possible to improve the transfer rate of reproduction data and to compensate the hologram distortion by optimizing the wavefront of reference light. It is an object of the present invention to provide a recording medium multiplex recording and reproducing method and a hologram recording medium multiplex recording and reproducing apparatus.

Holograms recording medium multiplex recording and reproducing apparatus of the present invention,
A plurality of interference fringes formed by causing signal light carrying information related to page data to interfere with the recording reference light are superimposed at the same position and a plurality of angle lights are recorded in the hologram recording medium. A hologram recording medium multiplex recording and reproducing apparatus for reproducing the page data information by making the light incident at a predetermined angle,
First reference light polarization adjusting means for adjusting and outputting the reproduction reference light to a first reference light which is either p polarization or s polarization;
First wavefront control means for controlling the wavefront of the first reference light from the first reference light polarization adjustment means so as to reduce distortion of a hologram;
First deflection angle adjustment means for adjusting an emission angle of the first reference light from the first wavefront control means to be incident on the hologram recording medium at a predetermined angle;
Of the first reference light output from the first deflection angle adjustment means and incident on the hologram recording medium, the polarized light transmitted through the hologram recording medium is the first reference light of p-polarized light and s-polarized light. A second reference light polarization adjusting means for adjusting and outputting a second reference light having a polarization different from that of
With respect to the second reference light from the second reference light polarization adjusting means, the wavefront of the second reference beam is reduced so as to reduce distortion of the wavefront of the first reference beam and distortion of the hologram due to transmission of the hologram recording medium. Second wavefront control means for controlling
Second deflection angle adjusting means for adjusting the emission angle so that the second reference light from the second wavefront control means is incident on the hologram recording medium at an angle different from the predetermined angle;
Reproduction light separating means for separating the first reproduction light generated from the hologram recording medium by the irradiation of the first reference light and the second reproduction light generated from the hologram recording medium by the irradiation of the second reference light;
Two imaging means for respectively imaging the hologram information carried by the two separated reproduction lights;
It is characterized by having.

  Here, the “hologram recording medium multiplex recording and reproducing apparatus” refers to not only one having a multiple recording and reproducing function but also one having only a function to reproduce a multiple recorded hologram.

  Preferably, noise light trapping means is provided for trapping noise light outputted out of the optical path among the second reference light transmitted through the hologram recording medium.

Further, said multi-recording and reproduction means at holograms recording medium multiplex recording and reproducing apparatus described above, it is preferable that the a galvanometer mirror, each for deflecting the respective linearly polarized light.

  In addition, while signal light is emitted at the time of recording page data, at a predetermined position where the reproduction light is incident at the time of reproduction of page data, at the time of recording page data, a modulation element that modulates light based on page data is And an element switching mechanism for switching so as to respectively install an imaging element for imaging page data information carried by linear polarized light of either p-polarization or s-polarization among reproduced reproduction light when reproducing page data. It is preferable to have it.

Furthermore, holograms recording medium multiplex recording and reproduction method of the present invention,
A plurality of interference fringes formed by causing signal light carrying information related to page data to interfere with the recording reference light are superimposed at the same position and a plurality of angle lights are recorded in the hologram recording medium. A hologram recording medium multiplex recording and reproducing method for reproducing the page data information by making the light incident at a predetermined angle,
Adjusting the reproduction reference light to a first reference light which is either p-polarization or s-polarization;
Controlling the wavefront of the first reference beam so as to reduce distortion of the hologram;
Adjusting an incident angle of the first reference light so as to be incident on the hologram at a predetermined angle;
Of the first reference light incident on the hologram recording medium, the polarization transmitted through the hologram recording medium is adjusted to the second reference light of p-polarization and s-polarization different from the first reference light. Output
Controlling the wavefront of the second reference beam such that distortion of the wavefront of the first reference beam or distortion of the hologram due to transmission of the hologram recording medium is reduced;
Adjusting the incident angle of the second reference light so as to be incident on the hologram recording medium at an angle different from the predetermined angle;
The first reproduction light generated from the hologram recording medium by the irradiation of the first reference light and the second reproduction light generated from the hologram recording medium by the irradiation of the second reference light are separated,
The hologram information carried by the two separated reproduction lights are respectively imaged by two imaging means.
It is characterized by

  Here, the “hologram recording medium multiplex recording and reproducing method” is a process that specializes not only in performing both the multiplex recording process and the regeneration process of the multiplex recording but also in a process for reproducing the multiplex recorded hologram. It shall be called including.

According to the hologram reproducing method and apparatus of the present invention, the reference light during reproduction is separated into p-polarized light and s-polarized light, and these polarized lights are simultaneously incident on the same position of the hologram recording medium with different incident angles. Since page data information multiplexed and recorded on these hologram recording media is sequentially reproduced by two pages using the method of multiplex recording and reproduction, data per page of page data in the multiplex recorded hologram It is possible to improve the transfer speed of data reproduced from the hologram, without increasing the amount or increasing the frame rate of the camera, etc., without particularly improving the functions on the camera side.

  Moreover, control is performed to reduce distortion of the wave front before irradiating the hologram recording medium with reference light for reproduction for reproducing each page data. The SNR of the data can be improved.

It is the schematic for demonstrating the principle of the hologram recording-medium multiple recording and reproducing apparatus based on embodiment of this invention. FIG. 5 is a schematic view showing an optical system of a hologram recording medium multiplex recording and reproduction apparatus according to a reference example 1; FIG. 6 is a schematic view showing an optical system of a hologram recording medium multiplex recording and reproduction apparatus according to a reference example 2; FIG. 2 is a schematic view showing an optical system of a hologram recording medium multiplex recording and reproducing apparatus according to an embodiment of the present invention. It is a photograph which shows the data obtained by the hologram recording-medium multiplex recording and reproducing apparatus based on embodiment of this invention. A part of the optical system of the variation of the holographic recording medium multiplex recording and reproducing apparatus according to an embodiment of the present invention is a schematic diagram showing. It is the schematic which shows the optical system of the hologram recording-medium multiplex recording-and-reproducing apparatus based on a prior art.

Hereinafter, a hologram recording medium multiplex recording and reproducing method and a hologram recording medium multiplex recording and reproducing apparatus according to an embodiment of the present invention will be described together with a reference example with reference to the drawings.
FIG. 1 shows the principle of reproduction of a hologram recording medium capable of simultaneously reproducing page data of two pages by compensating distortion of the hologram recording medium and distortion of the reference light wavefront.

When reproducing a hologram recording medium, two polarization states of p-polarization and s-polarization are used as reference light to be incident on the hologram recording medium.
Wavefront controllers 40a and 40b for controlling the wavefront, and galvano mirrors 50a and 50b for controlling the incident angle to the hologram recording medium 10, each of which comprises a phase modulation SLM, a deformable mirror or the like in each reference light path. Set up. When reproducing an angle-multiplexed hologram, predetermined page data uses p-polarized reference light, and page data adjacent to the predetermined page data uses s-polarized reference light, and these two reference lights are used. Are simultaneously incident on the recording medium 10. The reproduction light obtained by diffracting each reference light with the hologram travels along the same optical path. Therefore, PBS (polarization separation means) is provided in the reproduction optical path to separate the light into p-polarization reproduction light and s-polarization reproduction light, and data can be reproduced by imaging each reproduction light with a camera. The wavefronts of the respective polarizations control the wavefront controllers 40a and 40b in the reference optical path so as to optimize the reproduced image, based on the information of the camera for capturing the respective reproduced images.
Hereinafter, two reference examples and examples will be specifically described.

Reference Example 1
According to the reference example 1, a hologram recording medium multiplex recording and reproducing apparatus shown in FIG. 2 is configured as a recording and reproducing apparatus having a recording and playback functions of the hologram.
The hologram recording medium 110 is made of a photopolymer and has a configuration corresponding to the phase conjugation type.
However, the material of the hologram recording medium 110 according to the devices of the first and second embodiments and the present invention is not limited to the photopolymer, and the optical system is not necessarily limited to the phase conjugate type.

  As shown in FIG. 2, at the time of recording, the coherent laser beam emitted from the laser light source 111 passes through a shutter (not shown), and the beam diameter is expanded by a beam expander consisting of a diverging lens 112 and a collimating lens 113, The light passes through the half-wave plate 114, is deflected at a right angle by the mirror 115, and is split into two light fluxes by a polarization beam splitter (PBS: hereinafter simply referred to as PBS) 116.

  A light flux (signal-carrying light: p-polarized light) traveling from the PBS 116 to the left in the figure passes through the PBS 117 and is not shown in FIG. 2. A spatial light modulator (SLM (amplitude modulator): hereinafter simply referred to as SLM: recording Sometimes, an SLM is arranged so as to replace the illustrated camera 130, and is spatially modulated by the SLM to be signal light carrying page data information consisting of a digital image. Note that this amplitude modulation SLM is arranged in the same manner as the amplitude modulation SLM 460 shown in FIG.

  In addition, the signal light emitted (reflected) from the SLM changes its polarization state from the incident state depending on the page data to be s-polarized light, is reflected downward in the figure by the PBS 117, and is reflected by the lens (FTL) 118 It is optically Fourier-transformed and irradiated to the hologram recording medium 110.

  On the other hand, a light beam (s-polarized light) directed downward from the PBS 116 is used as a reference light (reference light during recording) so that the half-wave plate 122 (the optical axis of the half-wave plate 122 matches the polarization direction of the incident light) It passes through and is deflected at a right angle by the mirror 123, but since it is s-polarized, it is reflected by the PBS 124 and is directed downward from the PBS 124 in the figure. The luminous flux is angularly controlled by the galvano mirror 125, and is irradiated to the place where the signal light in the recording medium 110 is irradiated through the relay lens 126 at an angle different from that of the signal light, whereby the recording material of the recording medium 110 A refractive index change corresponding to the intensity of interference fringe light is induced therein, and this is held as hologram information.

In the reference examples 1 and 2 and the apparatus according to the present embodiment, since angle multiplex recording is assumed, page data is displayed on the SLM, and while sequentially displaying page data on the SLM, By changing the incident angle of the reference beam to the recording medium little by little by means of the galvano mirror 125 for each update, it becomes possible to multiplex and record different page data at the same position in the recording medium, and high density information Storage is possible.

  At the time of recording, a measurement control unit (not shown) performs drive control of the laser light source 111 and angle control of the galvano mirror 125, and sends page data to the SLM and instructs it to display.

Next, with reference to FIG. 2, it will be described playback function of the hologram recording medium multiplex recording and reproducing apparatus of Example 1.
As shown in FIG. 2, when the page data information recorded in the hologram recording medium 110 is reproduced, the polarization direction of the reference light is changed from s-polarization to p-polarization by adjusting the position of the half-wave plate 122. )Convert. The reference light is reflected by the mirror 123 and reaches the PBS 124, but since it is p-polarized by the half-wave plate 122, it travels straight through the PBS 124.

Next, the reference beam is split into two by a beam splitter (BS) 131 disposed in the reference beam path for reproduction. The wavefront of the reference beam reflected by the beam splitter (BS) 131 is controlled by the wavefront controller 140a, and the reference beam is reflected by the mirror 132 to reach the PBS 135, but since it is p-polarized, it passes through the PBS 135. On the other hand, the reference light transmitted through the beam splitter (BS) 131 is converted to s-polarized light by the half-wave plate 134, the wavefront is controlled by the wavefront controller 140b, and angle controlled by the galvano mirror 150b to reach the PBS 135, Since the light is s-polarized, it is reflected by the PBS 135.

  The p-polarized light transmitted through the PBS 135 and the s-polarized light reflected by the PBS 135 reach the galvano mirror 150 a in an overlapping manner, and the galvano mirror 150 a converts the p-polarized reference light and the s-polarized reference light for reproduction. On the other hand, control of the incident angle for performing angle multiplexing processing is performed.

  That is, the incident angle of the reproduction reference beam 2 to the hologram recording medium 110 is different from the incident angle of the reproduction reference beam 1 (usually, it differs by the incident angle of the adjacent step in which the page data is recorded) So that the rotation angle of the galvano mirror 150b is controlled. That is, the galvano mirror 150 b is provided to correspond to the angle difference between the incident angles of the p-polarized light and the s-polarized light simultaneously incident on the recording medium 110.

Further, as described above, the angle of the s-polarized light incident on the recording medium 110 is p-polarized recording medium 110 by adjusting the angle of the s-polarized reproduction reference light from the wavefront controller 140 b by the galvano mirror 150 b. The angle between the adjacent pages of the angle multiplex recording hologram is controlled to be given with respect to the incident angle to the light.
A relay lens 136 is disposed between the galvano mirror 150 a and the hologram recording medium 110.
As described above, the s-polarized reproduction reference light and the p-polarized reproduction reference light incident on the recording medium 110 are recorded on the recording medium 110 from the back side to the place where the signal light is irradiated. The light is emitted from the direction opposite to the incident direction of the reference light.

As described above, the reproduction light of predetermined page data is emitted from the hologram recording medium 110 by the irradiation of the reproduction reference light of s-polarization, and the predetermined page of the hologram recording medium 110 is the irradiation of the reproduction reference light of p-polarization. A reproduction light of page data adjacent to the data is emitted.
The two reproduction lights thus emitted are emitted in the same direction (upward direction in the drawing), and are irradiated to the PBS 117 through the lens 118. The PBS 117 transmits p-polarized reproduction light and reflects s-polarization reproduction light. Therefore, page data information carried by the p-polarization reproduction light is incident on the camera 120 and imaged. On the other hand, page data information carried by reproduction light which is s-polarized light is incident upon the camera 130 and imaged.

  In the reproduction light information acquired by the camera 120, for example, an evaluation value represented by the following equation is calculated, and the wavefront controller 140a is controlled so that the evaluation value becomes high.

  Similarly, in the reproduction light information acquired by the camera 130, the wavefront controller 140b is controlled. This makes it possible to obtain reproduction data with high SNR. Further, since the hologram distortions of adjacent page data are similar, the setting values of the wavefront controllers 140a and 140b for compensation are also similar. Therefore, control may be performed only on the wavefront controller 140a (or 140b), and the wavefront controller 140b (or 140a) may be controlled using the same value as the wavefront controller 140a (or 140b).

  Furthermore, in view of the fact that the hologram distortions of adjacent page data are similar to each other, the wavefront controllers 140a and 140b may be controlled by the average value of the reproduction light information acquired by the camera 120 and the camera 130 respectively. Good.

This also provides reproduced data with high SNR.
5 (a) shows the p-polarization reproduction data (page number 003) from the camera 120, and FIG. 5 (b) shows the s-polarization reproduction data (page number 00) from the camera 130.
4) is shown. As described above, since reproduction data of two-page data having high SNR can be obtained simultaneously, the data transfer rate can be greatly improved.

Reference Example 2
According to the reference example 2, the hologram recording medium multiplex recording and reproducing apparatus shown in FIG. 3, similar to that of Reference Example 1, and is configured as a recording and reproducing apparatus having a recording and playback functions of the hologram.
Holographic recording medium multiplex recording and reproducing apparatus of this reference example 2, since most have the same construction as that of Example 1, for these same members, the sign of the corresponding reference example 1 of member 100 The symbol which added and represents, represents, and abbreviate | omits detailed description.
The feature point of the reference example 2 is that wavefront control by the wavefront controller 240 is performed before the reproduction reference light is separated into p-polarized light and s-polarized light by the BS 231.

That is, the wavefront of the reproduction reference beam transmitted through the PBS 224 is controlled by the wavefront controller 240, and the reference beam is split into two systems by the beam splitter (BS) 231.
Since the reproduction reference light transmitted through the beam splitter (BS) is kept as p-polarized light, it transmits through the PBS 235 and reaches the galvano mirror 250a.
On the other hand, the reproduction reference light reflected by the beam splitter (BS) 231 enters the half-wave plate 234 through the mirror 232, and the p-polarized light is converted into s-polarized light. Thereafter, the reproduction reference light converted into s-polarized light is reflected by the galvano mirror 250 b, reflected by the PBS 235, and reaches the galvano mirror 250 a.

Effects on reproduction reference light after this are similar to those of Reference Example 1.
That is, the incident angle of the reproduction reference beam 2 to the hologram recording medium 210 is different from the incident angle of the reproduction reference beam 1 (usually, it differs by the incident angle of the adjacent step in which the page data is recorded) So that the rotation angle of the galvano mirror 250b is controlled. That is, the galvano mirror 250 b is provided to correspond to the angle difference between the incident angles of the p-polarized light and the s-polarized light simultaneously incident on the recording medium 210.

Further, as a control method of wavefront in the same manner as in Reference Example 1, in the obtained playback information on the camera 220 and the camera 230, an evaluation value represented by the formula (1) described above were calculated respectively, the average value is higher that Control the wavefront controller 240 in the same manner. Since the hologram distortion of adjacent pages is similar, high SNR reproduced data can be obtained for both p-polarization and s-polarization. Further, in the same manner as in Reference Example 1, the camera 220 only, or by using the reproduction data of the camera 230 to calculate the evaluation value, it may control the wavefront controller 240 so that the value is higher.

<Example>
According to this embodiment, holographic recording medium multiplex recording and reproducing apparatus shown in FIG. 4, similar to that of Reference Example 1, and is configured as a recording and reproducing apparatus having a recording and playback functions of the hologram.
The optical configuration according to the recording function of the hologram are similar to those in Reference Examples 1 and 2, detailed description will be omitted, only will be described optical arrangement according to the reproduction function.

  As shown in FIG. 4, in the case of reproducing page data information recorded in the hologram recording medium 310, the polarization direction of the reference light is converted (from s-polarization to p-polarization) by adjusting the half-wave plate 322. Do. The reference light is reflected by the mirror 323 and reaches the PBS 324, but since it is p-polarized by the half-wave plate 322, it travels straight through the PBS 324. Next, it is reflected downward in the figure by the wavefront controller 340a, and since it is p-polarized, it is transmitted through the PBS 335. The p-polarization reproduction reference light traveling straight through the PBS 335 is directed to the place where the signal light in the recording medium 310 is irradiated via the galvano mirror 350a and the relay lens 336 which performs angle control, and the recording reference light on the back side. The light is emitted from the direction opposite to the incident direction of.

By the way, although the reproduction reference light 1 irradiated to the hologram recording medium 310 is diffracted inside the hologram recording medium 310 to generate reproduction light, most of the irradiation light does not contribute as reproduction light, but the hologram It passes through the recording medium 310 as it is.
In this embodiment, a part of the irradiation light thus transmitted is again irradiated to the hologram recording medium 310 as the reference light 2 for reproduction, and the reproduction speed of data from the hologram recording medium 310 is approximately doubled. To increase it.

  That is, the p-polarized light transmitted through the hologram recording medium 310 is used as the reference light 2 for reproduction, travels backward the incident path of the reproduction light for recording, passes through the relay lens 326, is reflected by the galvano mirror 325, and goes straight on the PBS 324 The light is reflected leftward in the figure by the mirror 332 and reaches the half-wave plate 334. The half-wave plate 334 converts the p-polarized light into s-polarized light, and thereafter, the reproduction reference light 2 reaches the PBS 335 via the wavefront controller 340 b and the galvano mirror 350 b. At this time, since the reproduction reference light 2 is s-polarized light, it is reflected downward in the figure by the PBS 335, and the signal light in the hologram recording medium 310 is irradiated through the galvano mirror 350a and the relay lens 336 which performs angle control. The light is irradiated from the direction opposite to the incident direction of the recording reference light on the back side of the light source.

  The incident angle of the reproduction reference beam 2 to the hologram recording medium 310 is different from the incident angle of the reproduction reference beam 1 (usually, it differs by the incident angle of the adjacent step in which the page data is recorded). So that the rotation angle of the galvano mirror 350b is controlled. That is, the galvano mirror 350 b is provided to correspond to the angle difference between the incident angles of the p-polarized light and the s-polarized light simultaneously incident on the recording medium 310.

  As described above, the second reproduction light is emitted from the hologram recording medium 310 by the irradiation of the reproduction reference light 2. This second reproduction light is emitted in the same direction (upward direction in the figure) as the first reproduction light emitted from the hologram recording medium 310 by the irradiation of the reproduction reference light 1, and is sent to the PBS 317 via the lens 318. It is irradiated. In this PBS 317, the first reproduction light that is p-polarized light is transmitted, and the second reproduction light that is s-polarized light is reflected, so the page data information carried by the first reproduction light is incident on the camera 320 And the page data information carried by the second reproduction light is incident upon the camera 330 and imaged.

After this, the two reproduction reference beams are the Galvano mirror 325 and the Galvano mirror 350a.
And b, the incident angle to the hologram recording medium 310 is controlled so that reproduction of angle multiplex recording is sequentially performed.
As a result, simultaneous reproduction of two page data recorded in angle multiplex recording can be performed without increasing the reference light irradiation time or increasing the power of the light source, and the reproduction speed of data from the hologram recording medium 310 can be increased. It can be increased by about two times.

  A measurement control unit (not shown) performs drive control of the laser light source 311 and angle control of the galvano mirrors 325, 350a, 350b at the time of reproduction, and processes the page data information signal output from the cameras 320, 330. It instructs to display as a page data image on a monitor not shown.

  In addition, when the first reproduction light and the second reproduction light described above are compared, the amount of light obtained by each camera at the time of imaging is usually different. Among the reference lights 1 and 2 for reproduction irradiated to the hologram recording medium 310, the reflected light amount, diffracted light amount, absorbed light amount in the hologram recording medium 310, and further, absorbed light amount in optical parts such as a mirror and PBS, This is because the power of the reference light at the time of reproduction in the reproduction reference light 2 is lower than that of the reproduction reference light 1 due to the reflected light amount.

  Therefore, in the present embodiment, a light reduction means such as an ND filter (other light reduction means may be used: not shown) is provided on the lens front surface of the camera 320 on which the first reproduction light is incident. By adjusting the amount of light incident on the camera 320, it is possible to make the amounts of light of the two page data equal, even if the reproduction time of the two page data is equal.

  Further, as with the reproduction reference light 1, most of the reproduction reference light 2 is also transmitted through the hologram recording medium 310. Therefore, in the present embodiment, a noise light trap means (not shown) for trapping the transmitted light is provided so that the transmitted light does not become stray light and exerts an adverse effect as noise light.

  That is, of the reproduction reference light 2 irradiated to the hologram recording medium 310, s-polarized light transmitted through the hologram recording medium 310 is reflected to the right in the figure by the PBS 324 through the relay lens 326 and the galvano mirror 325. , And is converted to p-polarized light by the half-wave plate 322. Since the converted p-polarized light can be transmitted through the PBS 316 and become noise light output to the outside, noise light trapping means is disposed in the vicinity of the upper side of the PBS 316 in the drawing to trap noise light. As a result, the light does not return to the hologram recording medium 310 again, and the signal quality of the page data to be reproduced can be prevented from being deteriorated.

  Although it is preferable to use a light absorbing material or a beam pocket as the noise light trapping means, it is not limited thereto.

  In addition, since the hologram recording medium multiplex recording and reproducing apparatus according to the present embodiment is configured as a recording and reproducing apparatus having a hologram recording function and a reproduction function, the above-described SLM used at the time of recording and FIG. The camera 330 shown at the time of reproduction is switchable and installable. For example, the SLM and the camera 330 are respectively mounted on a linearly moving linear plate and a rotating plate. It is preferable to arrange the corresponding SLM or camera 330 on the optical path by arranging and switching and moving the linear plate and the rotary plate. In addition, it is preferable that the start of the switching movement is automatically performed according to the switching timing of recording / reproducing and the like.

Further, as a control method of wavefront in the same manner as in Reference Example 1, the reproduced data obtained by the camera 320 and the camera 330, and calculates an evaluation value of the formula (1), respectively, such that each evaluation value increases Control the respective wavefront controllers 340a and 340b. Since the reference light wavefront control of s-polarization can simultaneously control distortion of the wavefront due to transmission of the recording medium, reproduction data with a higher SNR than before can be obtained.

Further, Oite to the above embodiment, for example, as shown in FIG. 6, the number of optical elements so as to achieve commonality of a portion of the optical path of the reference light for reproduction 2 with the optical path of the reference light for reproduction 1 It may be reduced.

  That is, as shown in FIG. 6, at the time of reproduction, the reproduction reference light 1 incident as p-polarized light is irradiated to the PBS 524 through the mirror 523 and transmitted to the left in the drawing by the PBS 524 to control the wavefront. The position where the signal light is irradiated in the hologram recording medium 510 via the galvano mirror 550 and the relay lens 536 that performs angle control, and the back side of the hologram recording medium 510 face the incident direction of the recording reference light. It is irradiated from such a direction.

  Of the reproduction reference light 1 irradiated to the hologram recording medium 510, the p-polarized light transmitted through the hologram recording medium 510 is used as the reproduction reference light 2 to reverse the incident path of the recording reproduction light. It passes, is reflected by the galvano mirror 525, is incident on the half-wave plate 534, and is converted from p-polarization to s-polarization. The s-polarized reproduction reference light 2 is reflected leftward in the figure by the PBS 524, reflected by the wavefront controller 540, and controlled via the galvano mirror 550 and the relay lens 536 for angle control in the hologram recording medium 510. The area irradiated with the reproduction reference light 1 is irradiated from the direction opposite to the incident direction of the recording reference light on the back surface side.

Thus, without achieving high power of prolonged or source of the reference beam irradiation, also can make the angular multiplexing recording reproducing two page data while simultaneously compensating for the distortion of the reference wavefront, reference example Similar to the one, the reproduction speed of data from the hologram recording medium 510 can be doubled.
However, in this modification, when recording data, the PBS 524 is rotated 90 degrees in the direction of arrow A, and the recording reference light which is s-polarized light incident from the mirror 523 direction is on the polarization reflection surface of this PBS 524 It is necessary to set to be reflected downward in the figure.

Further, described above, in the real施例device has been assumed to have combined both recording function and playback function, as the hologram recording medium multiplex recording and reproducing apparatus of the present invention, even as having only the reproduction function I do not mind.

As described above, in angle-multiplexed recording and reproduction, the angle and position of the galvano mirror are gradually changed. Specifically, for example, the reference light is incident on the axis of the signal light. For example, 0.2 degrees in a range of 55 degrees to 75 degrees (in a range where the light emitting end structure and the emitted light do not physically cause interference (vignetting) when the signal light and the reference light are incident on the recording medium) The page data information may be recorded or reproduced in the area each time it is changed.

Also, by way of the upper you施例, first deflection angle adjustment means (e.g. galvanomirror 3 50a in the embodiment) and the second deflection angle adjusting means (e.g. galvanomirror 3 50a, 3 50b in the embodiment) Although a portion (e.g., galvanometer mirror 3 50a in the embodiment) are configured with the same deflection angle adjusting means, it is also possible to adopt a configuration in which the two deflection angle adjustment means disjoint from each other .
Incidentally, the noise light trapping unit of the real施例described above, but be provided in the vicinity of the optical element noise light is output, and the element to guide the noise light in an optical fiber or the like from this position Noise light may be trapped at spaced locations.
In addition, if the concept of the present invention is extended and used, it can be applied to various multiplexing methods such as perimetric multiplexing other than angle multiplexing.

111, 211, 311, 411 Laser light source 112, 212, 312, 412 Divergence lens 113, 213, 313, 413 Collimate lens 114, 122, 134, 222, 234, 314, 322, 334, 414, 422, 534 Half-wave plate 115, 123, 132, 215, 223, 232, 323, 332, 415, 423, 432, 523 Mirror 17, 116, 117, 124, 135, 216, 217, 224, 235, 316, 317 , 324, 335, 416, 417, 424, 524
Polarizing beam splitter (PBS) 131, 231 Beam splitter (BS)
118, 126, 136, 218, 226, 236, 318, 326, 336, 418, 426, 518, 526, 536 Lenses 10, 110, 210, 310, 410, 510 Holographic recording medium (recording medium) 20, 30, 120, 130, 220, 230, 320, 330, 420 cameras 50a, 50b, 125, 150a, 150b, 225, 250a, 250b, 325, 350a, 350b, 425, 450, 525, 550 Galvano mirror 460 amplitude modulation SLM
40a, 40b, 140a, 140b, 240, 340a, 340b, 540
Wavefront controller

Claims (3)

A plurality of interference fringes formed by causing signal light carrying information related to page data to interfere with the recording reference light are superimposed at the same position and a plurality of angle lights are recorded in the hologram recording medium. A hologram recording medium multiplex recording and reproducing apparatus for reproducing the page data information by making the light incident at a predetermined angle,
First reference light polarization adjusting means for adjusting and outputting the reproduction reference light to a first reference light which is either p polarization or s polarization;
First wavefront control means for controlling the wavefront of the first reference light from the first reference light polarization adjustment means so as to reduce distortion of a hologram;
First deflection angle adjustment means for adjusting an emission angle of the first reference light from the first wavefront control means to be incident on the hologram recording medium at a predetermined angle;
Of the first reference light output from the first deflection angle adjustment means and incident on the hologram recording medium, the polarized light transmitted through the hologram recording medium is the first reference light of p-polarized light and s-polarized light. A second reference light polarization adjusting means for adjusting and outputting a second reference light having a polarization different from that of
Second wavefront control means for controlling the wavefront of the second reference light from the second reference light polarization adjustment means so as to reduce distortion of the wavefront of the reference light due to transmission of the hologram recording medium and distortion of the hologram; ,
Second deflection angle adjusting means for adjusting the emission angle so that the second reference light from the second wavefront control means is incident on the hologram recording medium at an angle different from the predetermined angle;
Reproduction light separating means for separating the first reproduction light generated from the hologram recording medium by the irradiation of the first reference light and the second reproduction light generated from the hologram recording medium by the irradiation of the second reference light;
Two imaging means for respectively imaging the hologram information carried by the two separated reproduction lights;
A hologram recording medium multiplex recording and reproducing apparatus comprising: When recording page data, signal light is emitted, and when reproducing page data, at a predetermined position where the reproduction light is incident, when page data is recorded, a modulation element that modulates light based on page data is used. The apparatus further comprises an element switching mechanism for switching an image pickup element for picking up page data information carried by linear polarization of either p-polarization or s-polarization among the reproduced light to be reproduced at the time of data reproduction. holographic recording medium multiplex recording and reproducing apparatus according to claim 1, wherein the. A plurality of interference fringes formed by causing signal light carrying information related to page data to interfere with the recording reference light are superimposed at the same position and a plurality of angle lights are recorded in the hologram recording medium. A hologram recording medium multiplex recording and reproducing method for reproducing the page data information by making the light incident at a predetermined angle,
Adjusting the reproduction reference light to a first reference light which is either p-polarization or s-polarization;
Controlling the wavefront of the first reference beam so as to reduce distortion of the hologram;
Adjusting an incident angle of the first reference light so as to be incident on the hologram at a predetermined angle;
Of the first reference light incident on the hologram recording medium, the polarization transmitted through the hologram recording medium is adjusted to the second reference light of p-polarization and s-polarization different from the first reference light. Output
Controlling the wavefront of the second reference beam such that distortion of the wavefront of the reference beam or distortion of the hologram due to transmission of the hologram recording medium is reduced;
Adjusting the incident angle of the second reference light so as to be incident on the hologram recording medium at an angle different from the predetermined angle;
The first reproduction light generated from the hologram recording medium by the irradiation of the first reference light and the second reproduction light generated from the hologram recording medium by the irradiation of the second reference light are separated,
A hologram recording medium multiplex recording and reproducing method characterized in that the hologram information carried by the two separated reproduction lights are respectively imaged by two imaging means.