JP2006209613A - Holography recorder, reproducing device and method thereof, and holography medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photography recorder and a reproducing device capable of performing reproduction on an angle/wavelength condition corresponding to a page by detecting a page position even when the reference of an angle and wavelength changes. <P>SOLUTION: This holography recorder for changing the angle of reference light which irradiates a holography medium and performs multiplex recording of information data at different angles is provided with: an optical modulating means for outputting signal light modulated by information data to be written in the holography medium; a reference light irradiation means for sequentially changing the angles of reference light to be interfered with the signal light for each information data page to be written in and making the reference light incident on the holography medium; and an angle detection information writing means for writing angle detection information showing the angle of an information data page with the information data written therein in the holography medium. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a holographic recording apparatus, a reproducing apparatus and method used for recording information data, and a holographic medium.

2. Description of the Related Art A holographic recording system is used in which signal light composed of information data and reference light are irradiated on a holographic medium, an interference pattern is generated in the holographic medium, and the information data is recorded.
As a method for multiplex recording and reproduction of digital data consisting of “1” or “0” on this holographic medium, there is a method described in Patent Document 1 shown below and an apparatus corresponding to this method.
In this document, as a method for multiplex recording of information data at each of a plurality of locations of a holographic medium, a recording angle reproduction method in which recording and reproduction are performed by changing the angle of the reference light, and a recording by changing the wavelength of the reference light are performed. -The method of performing playback is described.

In the multiple recording method shown in Patent Document 1, in the case of writing angle multiplexing, information data recorded on a holographic medium is read with reference light for reading at an angle similar to the reference light at the time of recording. If irradiation can be performed, the information data (information data of the data page) written at a desired angle from among the multiplexed data can be arbitrarily read out.
JP 2004-177958 A

However, in the recording / reproducing method described above, when the holographic medium is irradiated with the reference light at the time of reading, the angle is the same as the angle of the reference light at the time of recording due to the mechanical accuracy in the optical system of the reproducing apparatus. There is a problem that information data cannot be read with high accuracy.
In particular, when considering recording with a holographic recording device and reading with a holographic reproducing device, the holographic medium needs to be loaded into the reproducing device for every reading, and for this reason, a predetermined incident angle of reference light for each rotation Since the angle deviation of the holographic medium with respect to may not be constant and varies, it becomes more difficult to set the reference light at the time of reading to the angle of the reference light at the time of recording. .
For example, in the case of angle multiplexing, if the reference light having the same angle as the angle recorded on the medium can be incident, the data of the desired page can be reproduced by the holography reproducing device.

However, when considering the hologram ROM, it is difficult to make the reference light incident on the medium (hologram ROM) at the same angle as the optical system recorded due to the mechanical accuracy of the optical system. Considering the replacement of the medium in particular, when the medium is loaded again on the reproducing apparatus, the incident angle of the reference light is deviated from the recorded angle.
Therefore, the conventional holographic reproducing device has a problem that it is difficult to match the angle of the reference light for reading with the angle when the holographic recording device records on the medium every time loading is performed.

Also, by multiplexing the wavelength of the reference light, when recording / reproducing information data on the media, for example, by adjusting the temperature of a wavelength tunable laser such as a VCSEL (surface emitting semiconductor laser) The wavelength of the emitted light is controlled to multiplex-record information data.
Here, the temperature of the VCSEL can be controlled to have an error within a certain range by adjusting the operating current.
However, the control temperature depends on the ambient temperature and the mounting form, and the operating current and the temperature of the VCSEL do not always coincide with each other, and the wavelength of the reference light to be used is recorded on the medium during recording and during reproduction. There is a problem that it is difficult to match the wavelength.

  The present invention has been made in view of such circumstances, and when reproducing information data from a medium in which information data is multiplexed and recorded by changing the angle and wavelength at a predetermined pitch, the angle and wavelength in the reproducing apparatus are provided. Holographic recording device that can detect the position of a media page (information data page) and reproduce it under the conditions of the desired angle or wavelength corresponding to the page even if the standard of the image changes (even if the angle and wavelength control accuracy is poor) An object of the present invention is to provide a playback apparatus and method.

The holographic recording device of the present invention is a holographic recording device that changes the angle of the reference light applied to the holographic medium and multiplex-records information data at different angles, and outputs signal light modulated by the information data written to the holographic medium A light modulating unit that performs interference with the signal light, and sequentially changes an angle of the reference light for each information data page to be written, and enters the holographic medium to enter the holographic medium, and an information data page on which the information data is written. Angle detection information writing means for writing angle detection information indicating an angle to the holographic medium.
The holographic recording method of the present invention is a holographic recording method in which the angle of the reference light applied to the holographic medium is changed and information data is multiplexed and recorded at different angles. The process of outputting the signal light, the process of sequentially changing the angle of the reference light to be interfered with the signal light by the reference light irradiating means for each information data page to be written, and entering the holographic medium, and written by the information data Writing angle detection information indicating the angle of the information data page to the holographic medium by the angle detection information writing means.
Accordingly, the holography recording apparatus / method records angle detection information for detecting the angle of the reference light corresponding to the information data page for each information data page, thereby the information data from the medium (holography medium). When reproducing, a medium capable of detecting an appropriate angle at the time of reproduction can be created from the angle detection information even if there is a deviation in angular accuracy of the holographic reproducing apparatus or an angular deviation in the loading of the medium.

In the holographic recording apparatus of the present invention, the angle detection information writing means records the angle detection information by deviating a predetermined amount of angle from the angle before and after the angle of the reference light on the information data page.
In the holography recording apparatus of the present invention, the angle detection information writing unit includes first angle information obtained by causing the angle detection information to deviate in a negative angle direction with respect to the angle of the reference light on the information data page; Write as second angle information deviated in the positive angle direction.
As a result, the holographic recording apparatus of the present invention provides the angle detection information for detecting the angle of the reference light corresponding to the information data page, the angle of the reference light in writing for each information data page, in a predetermined manner. By recording by deviating by the amount, the angle of the reference beam when reading the information data page can be easily detected from the angle detection information, and a medium that reads the information data from the information data page with high accuracy is created. can do.

In the holographic recording device of the present invention, the angle detection information writing means writes the angle detection information in a plurality of locations inside and / or around a recording area where information data is recorded.
As a result, the holographic recording apparatus of the present invention disperses the angle detection information at a plurality of locations as described above even if the angle detection information recorded at any location cannot be read due to some reading obstruction. Therefore, the angle of the reference light at the time of reading the information data page can be easily detected from the angle detection information from the angle detection information of the place where the information can be read, and the information data page can be detected with high accuracy. Media for reading information data can be created.

In the holographic recording device of the present invention, the angle detection information writing unit writes the angle detection information for each information data page to be angle multiplexed.
Accordingly, when the information data page is multiplexed with the predetermined angle pitch of the reference light, the holographic recording device of the present invention detects the angle for each information data page by the angle detection information. Access processing to the page becomes easy, and a medium capable of reading information data at high speed can be created.

In the holographic recording device according to the present invention, the angle detection information writing unit further changes the information by the angle that is sequentially changed with respect to the angle of the reference light of the first information data page on which the information data is recorded. Writes angle detection information for detecting the angle of the data page.
Accordingly, when the holographic recording apparatus of the present invention continuously reads the information data recorded on the medium by sweeping the angle of the reference beam during reproduction, the first information data page on which the information data is recorded Since the dummy information data page extended in advance is used as the head information data page, the angle of the reference light of the information data page in which the information data is recorded can be estimated from the set angle pitch. It is possible to create a medium that efficiently reproduces information data.

In the holographic recording device of the present invention, the angle detection information writing means encodes and records predetermined information among the page information of the information data page with respect to the angle detection information.
Thereby, the holography recording device of the present invention encodes and records not only the information for detecting the angle of the reference light of the information data page but also the incidental information such as the page number of the information data page, A medium capable of efficiently accessing a desired information data page during reproduction can be created.

When reproducing a holographic medium in which information data is multiplexed and recorded by any one of the above holographic recording apparatuses, the holographic reproducing apparatus of the present invention changes the angle of the reference light applied to the holographic medium, and is multiplexed and recorded at different angles. A holographic reproducing device that reads out information data, and detects reference light irradiation means for sequentially irradiating the holographic medium while changing the angle of the reference light, and detects angle detection information emitted from the holographic medium by the reference light. A recording angle detecting unit that controls an angle of the reference light of the data page; and a data detecting unit that receives the reproduction light emitted from the information data page by the reference light and detects information data from the reproduction light.
In the holographic reproduction method of the present invention, when reproducing a holographic medium on which information data is multiplexed and recorded by any one of the above holographic recording methods, the angle of the reference light applied to the holographic medium is changed and multiplexed recording is performed at different angles. A holographic reproduction method for reading out information data, a process of irradiating the holographic medium sequentially with reference light irradiation means by changing the angle of the reference light, and an angle emitted from the holographic medium by the recording angle detection means with the reference light The process of detecting the detection information and controlling the angle of the reference light of the information data page, and the data detection means irradiates the reproduction light emitted from the information data page by irradiating the reference light and the information from the reproduction light. Detecting data.
Accordingly, the holography reproducing device / method of the present invention reads out the angle detection information for detecting the angle of the reference beam corresponding to the information data page when reproducing the information data from the medium (holographic medium). Even if there is a deviation in angular accuracy of the holographic reproduction apparatus or an angular deviation in the loading of the media, an appropriate angle at the time of reproduction can be detected by the angle detection information, and information information can be read efficiently. .

In the holographic reproducing device according to the present invention, the recording angle detection means causes the first angle detection information obtained by deviating a negative angle with respect to the angle of the information data page as the angle detection information and a positive angle. Second angle detection information is detected, a sum component and a difference component of the first angle detection information and the second angle detection information are obtained, and the difference component is divided by the sum component to obtain a standardized numerical value. The angle of the information data page is detected.
As a result, the holographic reproducing apparatus of the present invention can stably read out the difference component by the sum component even if the detection intensity (reproduction intensity) of the angle detection information changes in units of information data due to some condition. The angle information of the reference light at the time can be calculated.

In the holographic reproduction device of the present invention, the recording angle detection unit detects a code corresponding to page information of the information data page included in the angle detection information, and detects a position of the information data page being reproduced.
Thereby, the holographic reproducing device of the present invention can obtain not only information for detecting the angle of the reference light of the information data page from the angle detection information, but also auxiliary information such as the page number of the information data page. By retrieving this page number from the page, it is possible to access a desired information data page, and an efficient reading process of information data can be performed.

In the holographic medium of the present invention, the angle detection information indicating the recorded angle of the information data page deviates from a predetermined amount of angle with respect to the reference light angle of the information data page when the information data is written. Recorded.
Thereby, in the holographic medium of the present invention, the angle detection information for detecting the angle of the reference light corresponding to the information data page is predetermined for each information data page before and after the reference light angle in writing. Therefore, the angle of the reference beam when reading the information data page can be easily detected from the angle detection information during reproduction, and the information data can be read from the information data page with high accuracy. Can be done.

In the holographic medium of the present invention, the angle detection information is recorded at a plurality of locations either inside or around a recording area where information data is recorded.
In the holographic medium of the present invention, the angle detection information is deviated in the negative angle direction with respect to the angle of the reference light on the information data page, and the second angle information is deviated in the positive angle direction. And angle information.
As a result, the holographic medium of the present invention disperses the angle detection information at a plurality of locations as described above even when the angle detection information recorded at any location cannot be read due to some reading hindrance. Therefore, the angle of the reference light at the time of reading the information data page can be easily detected from the angle detection information from the angle detection information of the location where the information can be read, and information can be obtained from the information data page with high accuracy. Data can be read.

The holographic recording apparatus of the present invention is a holographic recording apparatus that changes the wavelength of the reference light irradiated to the holographic medium and multiplex-records information data at different wavelengths, and outputs the signal light modulated by the information data written to the holographic medium Light modulation means, reference light irradiating means for sequentially changing the wavelength of the reference light that interferes with the signal light for each information data page to be written, and entering the holographic medium; and the information data page on which the information data is written Wavelength detection information writing means for writing wavelength detection information indicating a wavelength into the holographic medium.
The holographic recording method of the present invention is a holographic recording method in which the wavelength of reference light applied to the holographic medium is changed and information data is multiplexed and recorded at different wavelengths. The holographic recording method is modulated by the information data written to the holographic medium by a light modulation means. The process of outputting the signal light, the process of sequentially changing the wavelength of the reference light to be interfered with the signal light by the reference light irradiation means for each information data page to be written, and entering the holographic medium, and the wavelength detection information writing means Writing wavelength detection information indicating the wavelength of the information data page in which the information data is written to the holographic medium.
Accordingly, the holography recording apparatus / method records the wavelength detection information for detecting the wavelength of the reference light corresponding to the information data page for each information data page, thereby the information data from the medium (holography medium). When reproducing, a medium capable of detecting an appropriate wavelength at the time of reproduction can be created by the above-described wavelength detection information even if there is a deviation of the laser device in the holography reproducing apparatus.

When reproducing a holographic medium on which information data is multiplexed and recorded by any one of the holographic recording methods described above, the holographic reproducing apparatus of the present invention changes the wavelength of the reference light applied to the holographic medium, and multiplex recording is performed at different wavelengths. A holographic reproducing device that reads out information data, and detects reference light irradiation means for sequentially irradiating the holographic medium while changing the wavelength of the reference light, and detects wavelength detection information emitted from the holographic medium by the reference light. A recording wavelength detecting unit that controls the wavelength of the reference light of the data page; and a data detecting unit that receives the reproduction light emitted from the information data page by the reference light and detects information data from the reproduction light.
When reproducing a holographic medium in which information data is multiplexed and recorded by any one of the above holographic recording methods, the holographic reproducing method of the present invention changes the wavelength of the reference light on the holographic medium and multiplexly records the information data at different wavelengths. Is a holographic reproduction method for reading out light from a holographic medium by a reference light irradiating means, sequentially changing the wavelength of the reference light, and wavelength detection information emitted from the holographic medium by the recording wavelength detecting means. And detecting the wavelength of the reference light of the information data page, and the data detection means makes the reproduction light emitted from the information data page incident by irradiating the reference light by the data detection means, and the information data from the reproduction light Detecting.
Thereby, the holography reproducing device / method of the present invention reads out the wavelength detection information for detecting the wavelength of the reference light corresponding to the information data page when reproducing the information data from the medium (holographic medium). Even if there is a deviation in wavelength accuracy of the holographic reproducing device, an appropriate wavelength at the time of reproduction can be detected by the wavelength detection information, and efficient information data can be read out.

  In the holographic medium of the present invention, the wavelength detection information for detecting the wavelength of the reference light corresponding to the information data page has a predetermined amount before and after the reference light wavelength in writing for each information data page. Since the data is recorded with a deviation, the wavelength of the reference light when reading the information data page can be easily detected from the wavelength detection information during reproduction, and the information data can be read from the information data page with high accuracy.

  As described above, the holographic recording apparatus / method of the present invention multiplexes the angle (or wavelength) of the reference light at a predetermined angle (wavelength) pitch for each information data page when recording information data on a medium. When the angle (or wavelength) detection information for detecting the angle (or wavelength) of the reference light corresponding to the angle (or wavelength) information data page is recorded for each information data page, the medium (holographic medium) When the information data is reproduced from the above, even if there is a deviation in the angle (or wavelength) accuracy of the holography reproduction device or an angle deviation in the media loading, an appropriate angle at the time of reproduction is determined by the angle (or wavelength) detection information. Media that can detect (or wavelength) can be created.

  The holographic reproducing device / method according to the present invention also provides a reference light angle (corresponding to an information data page) when reproducing predetermined information data from a medium on which information data is multiplexed and recorded by the holographic recording device / method. Or, the angle (or wavelength) detection information for detecting the wavelength) is read out when reproducing the information data from the medium (holographic medium), so that the deviation of the angle (or wavelength) wavelength accuracy of the holography reproducing device, Even if there is an angle shift in media loading, an appropriate angle (or wavelength) at the time of reproduction can be detected from the angle (or wavelength) detection information, and information data can be read efficiently.

Hereinafter, a holographic recording apparatus and a reproducing apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows the same implementation when multiple recording of information data is performed by generating a plurality of pages for recording information data (hereinafter referred to as information data pages) by changing the angle of the reference light when multiplexing information data. It is a conceptual diagram which shows the concept of the holographic recording and reproduction | regeneration method in a form.
In the present invention, as shown in FIG. 1, angle detection information indicating the irradiation angle of the reference light of each information data page is recorded for each information data page that is multiplexed and recorded in the holographic medium (hereinafter, medium). .

This angle detection information is composed of a combination of the first angle detection information E and the second angle detection information L, and is an outer peripheral portion of the recording area of the information data page recorded in a multiplexed manner (FIG. 1 (a)). Alternatively, an angle detection information writing unit, which will be described later, is provided at one or a plurality of locations in the inner peripheral portion (FIG. 1B) or a predetermined position (preset position, FIG. 1C) inside the recording area. 9 (see FIG. 4).
Here, when the angle detection information is written to the outer peripheral portion and / or the inner peripheral portion of the recording area by a holographic recording device, for example, one of the sides, the pair of opposite sides, or the set of adjacent sides. You may provide in any one or all four sides.
At this time, the combination of the first angle detection information E and the second angle detection information L may be dispersed and recorded on each side.

The angle detection information includes first angle detection information E recorded by shifting (deviation) the angle in a predetermined negative direction with respect to the angle of the reference light for recording information data, and predetermined positive This is a combination with the second angle detection information L recorded by shifting (deviation) the angle in the direction of, and shifting the angle of, for example, about 1/4 of the angle pitch of the reference light in both the positive direction and the negative direction. Amount.
Therefore, the holography reproducing device of this embodiment detects the angle detection information during the reproduction process of information data from the medium, and detects the angle pitch of the information data page on which the information data is recorded, thereby reading out the information data. The angle of the reference light to be used can be easily controlled.

Hereinafter, the flow of the detection processing of the angle of the reference light corresponding to the information data page from the angle detection information described above will be described with reference to FIG. The reference light angle detection process and reference light angle control at the time of reading based on the angle detection information described below are performed in a recording angle detection unit 10 (see FIG. 4) described later.
In each angle detection information, the first angle detection information E and the second angle detection information L are detected as different intensity peaks by a detector (detector) corresponding to the change in the angle of the reference light during reproduction. The

Here, assuming that the detection intensity of the first angle detection information E detected by the detector is e and the detection intensity of the second angle detection information L is l, the following equation (1) is calculated.
PES = (e−l) / (e + l) (1)
In FIG. 2, when detecting the angle θ1 of the read reference light, the PES is calculated using the detection intensity e1 of the first angle detection information E1 and the detection intensity l1 of the second angle detection information L1. Become.

That is, the difference component between the detection intensity e1 of the first angle detection information E1 and the detection intensity l1 of the second angle detection information L1 is obtained by the above equation (1), and the sum component of the detection intensity e1 and the detection intensity l1 is obtained. Divide and normalize the difference component by the sum component to calculate the PES.
As a result, even if the detection intensity (reproduction intensity) of the angle detection information changes in units of information data due to some condition, the difference component is normalized by the sum component, and the PES can be calculated stably.

In the above equation (1), PES (Page Error Signal) is a numerical value indicating a deviation amount from each information data page (access position error amount).
Then, in the negative slope portion of the PES, the point A at which the zero (0) cross is made, that is, the angle at which “el” is “0” becomes the angle of the reference light for reading the information data in each information data page. The angle of the reference light for reading corresponds to the angle θ of the reference light when writing the information data page, and the reproduction intensity (diffraction efficiency) S of the recorded information data in the detector is maximized.
That is, it is possible to detect the angles θ1, θ2, θ3, θ4,... Of the reference light corresponding to each information data page that maximize the reproduction intensity S1, S2, S3, S4,. .

Therefore, the PES can be used for servo control for accessing the information data page when reading the information data recorded on each information data page, that is, for adjusting the angle of the reference light for reading.
As described above, the angle detection information may be recorded around the recording area where the information data is recorded, or may be recorded at a preset position inside the recording area.
Furthermore, by recording the angle detection information in a plurality of locations instead of one location (distributed recording), even if any location is not detected, using the read angle detection information in a plurality of locations, The angle of the reference light corresponding to the information data page can be calculated.

That is, as shown in the following equation (2), the PES is calculated by calculating the sum of the detection intensity e of the first angle detection information E and the detection intensity l of the second angle detection information L. Thus, it can be used for servo control for adjusting the angle of the reference light for reading.
PES = (Σe−Σl) / (Σe + Σl) (2)
At this time, the combination of the angle detection information, that is, the arrangement of the first angle detection information E and the second angle detection information L is made different as shown in FIG. Thereby, the accuracy of the angle of the reference beam corresponding to the information data page can be improved.
As described above, the angle detection information is recorded for each information data page, whereby the angle of the reference light when reading the information data stored in each information data page can be detected.

Further, when the information data is reproduced, the angle of the reference beam is swept to detect each information data page, so that the head of the top information data page can be easily found, as shown in FIG. It is also possible to record angle information data by extending to an angle region where no is recorded.
In this case, the angle θ0 one page before is detected with respect to the angle of the reference light at which the information data is actually written, that is, the first information data page (reference light angle θ1) which is the actual first page. Therefore, the angle θ1 of the reference light of the first information data page can be roughly estimated from the angle θ0 based on the angle pitch of the reference light corresponding to the information data page set in advance in advance.

As a result, the recording angle detection unit 10 to be described later, when continuously reproducing each information data page, sets the position where the angle pitch is added to the angle θ of the reference light of the immediately preceding information data page as the next information data page. The angular position of the reference light corresponding to the original information data page is corrected from the deviation value of the PES signal calculated at that time, and the mirror 8 is controlled according to the angle. It can be reflected in the prediction of the information data page.
As a result, the holographic reproduction processing according to the present invention can reproduce information data continuously at high speed.

<First Embodiment>
Next, a holographic recording / reproducing apparatus according to the first embodiment of the present invention will be described with reference to FIG. FIG. 4 is a block diagram showing a configuration example of the holographic recording / reproducing apparatus according to the first embodiment. That is, FIG. 4 is an optical layout diagram showing a configuration example for recording and reproducing on a medium.
In the first embodiment of FIG. 4, a transmission hologram in which signal light and reference light are incident on the medium 4 from the same side is described as an example.
The holographic recording / reproducing apparatus shown in FIG. 4 includes a beam splitter 2, a shutter 1, an SLM, 2, an FT lens 3 and 7, a detector 6, a shutter 7, a mirror 8, an angle detection information writing unit 9, and a recording angle detection unit. 10 and a laser light source (not shown).

A. Recording process of information data on the medium 4 The laser light source emits a laser beam having a predetermined wavelength, and this laser beam is divided into a distribution light M and a distribution light N by a predetermined mechanism (such as a beam splitter (not shown)), The light enters the shutter 1 and the shutter 7, respectively.
The shutter 1 is opened when information data is written to the medium 4, and is closed when not written.

The SLM 2 is composed of a liquid crystal panel or the like, and displays a checkered dot pattern corresponding to information data to be written on the medium 4, that is, two-dimensional information data to be written, on a modulation surface perpendicular to the incident angle of the distribution light M. To form.
This SLM · 2 modulates the amplitude of the incident distributed light M with the dot pattern on the modulation surface and emits it to the FT (Fourier transform) lens 6 as signal light including information to be written on the medium 4.

In addition, the SLM · 2 associates the angle detection information (first angle detection information E and second angle detection information L) with the writing position of the angle detection information at the writing timing of each angle detection information. It is formed on the modulation surface at a different timing from the information data.
In FIG. 4, a transmissive SLM is used, but a reflective SLM can also be used in combination with a beam splitter or the like.
In addition, the SLM.2 is efficient in that it has a wider modulation surface (modulation region) so that the whole including the information data and the angle detection information can be controlled.

In FIG. 1, the area other than the area where information data and angle detection information (and wavelength detection information described later) are recorded is displayed in white.
However, in practice, it is preferable that the modulation surface be modulated in black so as not to transmit the reference light. In addition, when recording angle detection information by shifting the angle, only the corresponding angle detection information is displayed at a predetermined position where the angle is shifted, and the reference light is transmitted to the storage position of the angle detection information on another information data page. In order to avoid this, the recording is made black (without transmitting light).
Furthermore, when recording the information data in the recording area, the angle detection data portion may be recorded in black.

The FT lens 3 collects the signal light from the SLM 2 and irradiates the medium 4 to be hologram-recorded (multiplexed recording). Here, the medium 4 is installed in the vicinity of the condensing point of the FT lens 3.
The shutter 7 controls the emission of the distributed light N distributed by the beam splitter to the mirror 8 by performing an opening / closing process synchronized with the opening / closing timing of the shutter 1.
The mirror 8 is composed of a galvanometer mirror or the like that can vary the reflection angle of incident light, and the reflection angle of the incident distributed light N is sequentially changed by the control of the angle detection information writing unit 9 so that the medium is used as reference light. 4 is emitted.

Here, the reference light is controlled to be incident so that the signal light is superimposed on the vicinity where the signal light is incident on the medium 4, and information on interference fringes formed by the interference between the signal light and the reference light is information media. 4 is recorded.
At this time, the mirror 8 changes the angle of the reference light at a predetermined angle pitch, so that information data of different signal lights is recorded in a predetermined storage area of the medium 4, that is, the SLM 2 New data can be sequentially overwritten by two-dimensional information data of different dot patterns (checkered pattern) formed on the modulation surface.

The angle of the reference beam in which the two-dimensional information data is recorded is called an information data page.
In the above-described writing process, the angle detection information writing unit 9 adjusts the writing angle of the reference light in each information data page, and this information for each reference light angle corresponding to each information data page. The reflection surface of the mirror 8 is adjusted to a negative angle by an angle amount of ¼ of the angle pitch with respect to the angle of the reference light corresponding to the data page, and the first angle detection information E is a predetermined value corresponding to the recording area. After recording the information data and writing the information data, the reflection surface of the mirror 8 is adjusted to a positive angle by an angle amount that is 1/4 of the angle pitch, and the second angle detection information L corresponds to the recording area. Record at a predetermined position.

At this time, the angle detection information writing unit 9 adjusts the reflection surface of the mirror 8 to a negative angle by an angle amount that is ¼ of the angle pitch with respect to the angle of the reference light corresponding to each information data page. When the first angle detection information E is output to the SLM · 2 and the reflecting surface of the mirror 8 is adjusted to a positive angle by an angle amount that is ¼ of the angle pitch, the second angle detection information L is changed to the SLM · Output to 2.
As a result, the SLM · 2 forms the first angle detection information E and the second angle detection information L as dot patterns at the positions of the modulation surfaces corresponding to the writing positions in the medium 4, respectively.

Further, the angle detection information recorded in each information data page may be encoded as shown in FIG. 5 and the page information of the corresponding information data page, for example, the page number of each information data page may be recorded in advance. .
By including such information, the angular position of the information data page can be detected, and information such as the page number of the information data page can be detected at the same time, and the search processing of the information data recorded on the medium 4 is more reliable and flexible. Enable data access.

The above-described encoding may be in the form of a one-dimensional barcode pattern shown in FIG. 5A for easy reading, and the two-dimensional shown in FIG. 5B for the purpose of increasing the amount of information. A dot pattern may be used.
In addition, the angle detection information pattern does not necessarily need to be a dot pattern with the same resolution as that of the information data, and the reading and detection of the code can be facilitated by reducing the dot resolution.

In the multiplex recording method described above, the medium 4 is a hologram medium having a relatively thick recording layer (a layer in the thickness direction where interference fringes are formed) (for example, 1 mm or more), and the angle of the reference light is multiplexed. When recording, the angular resolution at the angular pitch of the information data page is determined by the wavelength λ of the laser light, the incident angle θ of the signal light and the reference light with respect to the surface of the medium 4, and the thickness D of the medium 4.
That is, the angular resolution at the angular pitch is proportional to the laser wavelength λ and inversely proportional to the thickness D of the medium 4.
Here, the incident angle θ is an angle formed by the reference light incident direction with respect to the vertical axis P of the reference light incident surface of the medium 4.

B. Next, when reproducing information data recorded on the medium 4, the signal light side shutter 1 is closed, the reference light side shutter 7 is opened, and only the distribution light N is obtained. By making the light incident on the medium 4, the information data recorded on the medium 4 is reproduced.
Based on the angle detection information written by the angle detection information writing unit 9, the recording angle detection unit 10 detects the angle of the reference light at the time of reading corresponding to the angle of the reference light at the time of recording. Information data corresponding to the information data page is reproduced and emitted from the back surface of the medium 4 (reverse to the surface on which the reference light is incident) to the FT lens 5 as reproduction light.

The FT lens 5 returns the incident reproduction light to signal light incident on the FT lens 3, that is, returns to parallel light (coherent light), and projects it onto a detector (detector) 9.
Here, the focal lengths of the FT lens 3 and the FT lens 5 are the same, and the SLM · 2, the FT lens 3, the media 4, the FT lens 5, and the detector 6 are arranged apart from each other by the focal length.
In other words, the SLM 2 and the detector 6 are respectively placed at the front focal point of the FT lens 3 and the rear focal point position of the FT lens 5.

Therefore, the reference light is diffracted by the information data stored in each information data page in the recording area of the medium 4, that is, interference fringes, and the reproduction light is generated.
This reproduction light is converted into parallel components by the FT lens 5 and imaged on the detector 6 as a pattern similar to the two-dimensional dot pattern on the modulation surface of the SLM · 2, and information data is reproduced.
The detector 6 is composed of a two-dimensional CCD, a C-MOS image sensor or the like, reads the pattern, and outputs it as information data to an external circuit.

Here, the recording angle detector 10 adjusts the angle of the reflecting surface of the mirror 8 and controls the angle θ of the reference light incident on the medium 4, thereby reproducing information data stored in different information data pages. .
For this reason, the recording angle detection unit 10 reads the detection intensities e and l of the angle detection information for which the arrangement position is set in advance from the detector 6, performs the processing of the equation (1) or (2), and performs the PES processing. Detects the angle θ of the reference light that becomes “0” at a negative inclination, and performs servo control of the reflecting surface of the mirror 8 so that the angle θ becomes this angle θ.

The reproduction intensity S of the reproduction signal light observed when the angle of the reference light is continuously changed is schematically shown in FIG.
The intensity of the reproduction light of the information data stored in each information data page shows a distribution approximated by the square of the approximate SINC function (SIN (πX) / πX) with respect to the angle θ of the reference light.
For this reason, each information data page was recorded without being interfered by the adjacent information data page by arranging each information data page so that the centers of the adjacent information data pages come near the second zero point of the SINC function. Information data can be read efficiently and with high accuracy.

Ideally, the maximum diffraction efficiency can be obtained from the interference fringes of the information data page to be read in the recording area if the angle of the reference light at the time of recording can be reproduced and the reference light can be incident at that angle. Thus, the maximum reproduction intensity S is obtained on the detector 6.
However, when the medium 4 is once taken out and loaded, when the medium 4 is tilted and fixed at the time of reinsertion, or when the loaded medium is recorded by another holography recording device, the medium is fixed. Cannot be set to the same angle as during recording.

For this reason, the angle of the reproduction light at the time of writing cannot be reproduced at the time of reproduction, and it is difficult to reproduce the information data written on the medium.
In particular, in a medium with high multiplicity having a thickness exceeding 1 mm, the angle pitch between information data pages is on the order of 0.1 degree, and the angle accuracy required at the time of reproduction is about 0.01 degree. Therefore, even if there is a slight angle shift of the optical system or an angle shift at the time of loading the medium, it is impossible to reproduce at the same angle.
However, as described above, in the present invention, the angle of reference light corresponding to each information data page can be detected by the recording angle detection unit 10 based on the angle detection information recorded on the medium. Even when the medium is loaded at an inclination, the angle of the reflecting surface of the mirror 8 can be adjusted so that the angle of the reference light corresponding to the information data page is successively obtained.

<Second Embodiment>
Next, as a second embodiment, a system configuration corresponding to a ROM (read only memory) type or a write-once type medium in which a holographic recording device and a holographic reproducing device are separated may be employed.
For example, in the system configuration shown in FIG. 6, signal light and reference light are incident from the opposite side of the medium 4 during recording (FIG. 6A), and the reference light is used as phase conjugate reproduction illumination light during reproduction. A reflection hologram is used as an example (FIG. 6B).

In the case of the configuration shown in FIG. 6, in the holographic recording device shown in FIG. 6A, the angle of the reference beam is changed, and the medium 4 on which the information data is multiplexed and recorded on a plurality of information data pages is used as the holography ROM. create.
Here, similarly to FIG. 4, the signal light is emitted from the SLM · 2 and the reference light is emitted from the mirror 8. For other configurations, the recording angle detection unit 10 is not provided, and the FT lens 3 is connected to the SLM · 2 is the same as FIG. A rectangular opening 11 is provided between the SLM 2 and the medium 4.
And the writing process of the information data and the angle detection information to the medium 4 is performed by the same process as in the first embodiment.
At this time, the reference light is incident on the recording area where the incident light is incident on the medium 4 from the surface opposite to the surface on which the signal light is incident.

In the holographic reproducing device shown in FIG. 6B, at the time of reading, the phase conjugate reproducing illumination light is used instead of the reference light, and the information data reproducing process is performed by the reading process described in the first embodiment. .
In this holographic reproducing device, phase conjugate reproduced illumination light is incident on the same surface as the surface on which signal light is input in the holographic recording device. Thereby, it is not necessary to provide an FT lens on the holography reproducing device side.
Since the phase conjugate reproduction illumination light is configured to be read from behind, it is defined so that the reference light becomes phase conjugate light, and is the same beam as the reference light in FIG.

At this time, the angle of the phase conjugate reproduction illumination light is controlled by the recording angle detection unit 10 detecting the incident angle θ of the phase conjugate reproduction illumination light based on the angle detection information as in the first embodiment. The reflection surface of the mirror 8 is controlled so that the phase conjugate reproduction illumination light is incident at an angle corresponding to the information data page.
Although the holographic reproduction device is not shown, a laser device, a shutter 7, a mirror 8, and a recording angle detection unit 10 are provided as necessary as in the first embodiment.
The difference from the first embodiment is that the detector 6 is the same as the surface of the medium 4 to which the phase conjugate reproduction illumination light is input via the rectangular opening 12 (the area corresponding to the detection surface of the detector 6). It is arranged on the side.

Therefore, the holographic reproducing device shown in FIG. 6B is a holographic ROM reproducing device that makes phase conjugate reproduction illumination light incident from a desired angle based on angle detection information recorded on the medium 4 and reproduces recorded information data. It can be.
In the above-described holographic ROM reproducing device, it is difficult to make the angle of the reference light at the time of writing and the angle of the phase conjugate reproducing illumination light at the time of reading particularly the same in the configuration. Assuming that different media are loaded, angular deviation is inevitable.
However, as described above, by recording the angle information number on the medium by the method shown in the second embodiment, it is possible to reproduce the information data accurately while allowing the angle deviation.

<Third Embodiment>
Next, a holographic recording / reproducing apparatus according to the third embodiment of the present invention will be described.
In the first and second embodiments, as described above, the information data in each storage area is multiplexed by generating the information data page for each different angle by changing the angle of the reference light. .
On the other hand, the third embodiment is an example applied to a wavelength multiplexing system in which the laser light source 1 is controlled to change the wavelength of the emitted laser light and to multiplex each wavelength.
However, in general, the wavelength resolution of transmission holograms is significantly inferior to that of reflection holograms. Therefore, in the case of multiplexing by wavelength, the reflection hologram method, that is, the phase conjugate light of the second embodiment is used. A configuration example in which the information signal is reproduced by using is preferable.

However, in the case of using any of the transmission hologram and the reflection hologram, the recording process in the third embodiment uses the angle in the first and second embodiments as a wavelength and does not shift the angle. Multiple recording of information data is performed by a plurality of information data pages by shifting the wavelength for each information data page.
On the other hand, in the reproduction processing in the third embodiment, the angle in the first and second embodiments is set as the wavelength, the recording angle detection unit 10 is changed to read the wavelength information data recorded on the medium by the recording wavelength detection unit, As in the first and second embodiments, the PES is calculated, the wavelength corresponding to the desired information data page is detected, the laser device is controlled to be this wavelength, and the information data page corresponding to this wavelength Read the information data. (See Figure 7)

  Here, the wavelength detection information is composed of a combination of the first wavelength detection information E and the second wavelength detection information L, and the first wavelength with respect to the wavelength of the reference light for recording the information data. The detection information E is recorded by shifting (deviation) the wavelength in a predetermined negative (short) direction, and the second wavelength detection information L is shifted (deviation) in the predetermined positive (long) direction. The shift amount is a wavelength that is about ¼ of the wavelength pitch of the reference light, for example, a wavelength that is ¼ or less in both the positive direction and the negative direction.

In addition, as described in the first and second embodiments, the method for extending the wavelength detection information and adding the page number and the method for encoding the wavelength detection information are applied in the same manner as in the case of angle multiplexing. Is possible.
In wavelength multiplexing, the temperature of the VCSEL or the like is controlled to change the wavelength of the emitted laser light, so it is difficult to set a control reference beyond the angle, and the method using the wavelength detection information in the present invention is as follows. This is effective as a method of reading information data recorded in each information data page.

The plane of the medium indicating the recording position of the angle (or wavelength) detection information indicating the angle (or wavelength) of the reference light with respect to the multiple recorded information data page in the first and second (or third) embodiments of the present invention FIG. It is a conceptual diagram explaining the detection method of the angle of the reference beam corresponding to the information data page by which angle multiplexing recording was carried out in the 1st Embodiment of this invention. It is a conceptual diagram at the time of recording an angle (or wavelength) detection signal extended to an angle where no information data is recorded. 1 is a block diagram illustrating a configuration example of a holographic recording / reproducing apparatus according to a first embodiment of the present invention. It is a conceptual diagram which shows the pattern shape at the time of encoding angle (or wavelength) detection information. It is a conceptual diagram explaining the holography recording device and holography reproducing | regenerating apparatus in the 2nd Embodiment of this invention. In the 3rd Embodiment of this invention, it is a conceptual diagram explaining the detection of the wavelength corresponding to an information data page from wavelength detection information.

Explanation of symbols

1,7 ... Shutter 2 ... SLM
3, 5 ... FT lens 4 ... Media 6 ... Detector 8 ... Mirror 9 ... Angle detection information writing unit 10 ... Recording angle detection unit 11, 12 ... Rectangular opening

Claims (20)

A holographic recording device that multiplexes and records information data at different angles by changing the angle of reference light applied to the holographic medium,
A light modulating means for outputting signal light modulated by information data written to the holographic medium;
Reference light irradiation means for sequentially changing the angle of the reference light to be interfered with the signal light for each information data page to be written and entering the holographic medium,
A holography recording apparatus comprising: angle detection information writing means for writing angle detection information indicating an angle of an information data page in which the information data is written to the holographic medium.   2. The angle detection information writing unit records the angle detection information with a predetermined amount of angle being deviated from before and after the angle of the reference light on the information data page. Holographic recording device.   3. The angle detection information writing unit writes the angle detection information in a plurality of locations inside and / or around a recording area in which information data is recorded. Holographic recording device.   The angle detection information writing means causes the angle detection information to deviate in the positive angle direction from the first angle information that is deviated in the negative angle direction with respect to the angle of the reference light on the information data page. 4. The holographic recording device according to claim 2, wherein the holographic recording device is written as second angle information.   The holographic recording apparatus according to claim 1, wherein the angle detection information writing unit writes the angle detection information for each information data page to be angle multiplexed.   An angle at which the angle detection information writing means detects an angle of an information data page that is the previous one by an angle that is sequentially changed with respect to the angle of the reference light of the first information data page in which the information data is recorded. 6. The holographic recording apparatus according to claim 1, wherein detection information is written.   7. The angle detection information writing means encodes and records predetermined information of page information of the information data page with respect to the angle detection information. The holographic recording device described. A holographic reproducing device that reads out information data that is multiplexed and recorded at different angles by changing the angle of the reference light that irradiates the holographic medium,
Reference light irradiation means for sequentially irradiating the holographic medium while changing the angle of the reference light;
Recording angle detection means for detecting angle detection information emitted by the reference light from the holographic medium and controlling the angle of the reference light on the information data page;
A holography reproducing apparatus, comprising: a data detecting unit configured to detect the information data from the reproduction light by inputting the reproduction light emitted from the information data page by the reference light.   The recording angle detection means includes, as the angle detection information, first angle detection information in which a negative angle is deviated from the angle of the information data page, and second angle detection information in which a positive angle is deviated. Is detected, the sum component and the difference component of the first angle detection information and the second angle detection information are obtained, and the angle of the information data page is detected from the standardized numerical value by dividing the difference component by the sum component. The holographic reproducing device according to claim 8, wherein   9. The recording angle detecting means detects a page information code of the information data page included in the angle detection information, and detects a position of the information data page being reproduced. 9. The holographic reproducing device according to 9.   Angle detection information indicating the recorded angle of the information data page is recorded with a predetermined amount of deviation from the angle before and after the reference light angle of the information data page when the information data is written. Holographic media characterized by   12. The holographic medium according to claim 11, wherein the angle detection information is recorded in a plurality of locations inside and / or around a recording area in which information data is recorded.   The angle detection information includes first angle information that is deviated in the negative angle direction and second angle information that is deviated in the positive angle direction with respect to the angle of the reference light on the information data page. The holographic medium according to claim 11 or 12, characterized in that A holographic recording device that multiplexes and records information data at different wavelengths by changing the wavelength of the reference light applied to the holographic medium,
A light modulating means for outputting signal light modulated by information data written to the holographic medium;
Reference light irradiation means for sequentially changing the wavelength of the reference light to be interfered with the signal light for each information data page to be written and entering the holographic medium,
A holography recording apparatus comprising: wavelength detection information writing means for writing wavelength detection information indicating a wavelength of an information data page in which the information data is written into the holographic medium. A holography reproduction device that reads out information data that is multiplexed and recorded at different wavelengths by changing the wavelength of the reference light that irradiates the holographic medium,
Reference light irradiation means for sequentially irradiating the holographic medium while changing the wavelength of the reference light;
Recording wavelength detection means for detecting wavelength detection information emitted from the holographic medium by the reference light and controlling the wavelength of the reference light on the information data page;
A holography reproducing apparatus, comprising: a data detecting unit configured to detect the information data from the reproduction light by inputting the reproduction light emitted from the information data page by the reference light.   Wavelength detection information indicating the wavelength recorded in the information data page is recorded with a predetermined amount of wavelength being deviated from the wavelength of the reference light on the information data page when the information data is written. Holographic media characterized by It is a holographic recording method in which the angle of the reference light applied to the holographic medium is changed, and information data is multiplexed and recorded at different angles.
A step of outputting signal light modulated by information data written to the holographic medium by a light modulation means;
The process of sequentially changing the angle of the reference light to be interfered with the signal light by the reference light irradiation means for each information data page to be written, and entering the holographic medium,
A holographic recording method comprising: writing angle detection information indicating an angle of an information data page written by the information data to the holographic medium by an angle detection information writing unit. It is a holographic reproduction method for changing the angle of the reference light applied to the holographic medium and reading out information data recorded in multiple angles at different angles.
A process of sequentially irradiating the holographic medium with a reference light irradiation means while changing the angle of the reference light,
Detecting angle detection information emitted by the reference light from the holographic medium by a recording angle detection means, and controlling the angle of the reference light on the information data page;
A holographic reproduction method comprising: a step of detecting reproduction data emitted from the information data page by irradiating a reference beam by data detection means and detecting information data from the reproduction beam. A holographic recording method that multiplexes information data at different wavelengths by changing the wavelength of the reference light applied to the holographic medium,
A step of outputting signal light modulated by information data written to the holographic medium by a light modulation means;
The process of sequentially changing the wavelength of the reference light to be interfered with the signal light by the reference light irradiation means for each information data page to be written and entering the holographic medium,
A holographic recording method, comprising: writing wavelength detection information indicating a wavelength of an information data page in which the information data is written by a wavelength detection information writing unit to the holographic medium. A holographic reproduction method that reads out information data that is multiplexed and recorded at different wavelengths by changing the wavelength of the reference light on the holographic medium,
Irradiating the holographic medium by changing the wavelength of the reference light sequentially by the reference light irradiation means;
Detecting wavelength detection information emitted by the reference light from the holographic medium by a recording wavelength detection means, and controlling the wavelength of the reference light on the information data page;
A holography reproduction method comprising: a step of detecting reproduction data emitted from the information data page by irradiating a reference beam by data detection means and detecting information data from the reproduction beam.

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