JP3566033B2 - Hologram memory device and method for recording and reproducing information to be recorded by the hologram memory device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a hologram memory device using the principle of holography, and a method for recording and reproducing information using the hologram memory device.
[0002]
[Prior art]
FIG. 11 shows an example of a conventional hologram memory device. Information recording in the hologram memory device shown in FIG. 11 is performed as follows. That is, first, the laser light emitted from the laser light source 101 is split by the beam splitter 102 into object light and reference light.
[0003]
Of these, the object light passes through the liquid crystal panel 103 functioning as a page composer. When passing through the liquid crystal panel 103, the object light is added with information as a surface, and is incident on the hologram recording medium 104 made of lithium niobate crystal. The image of the information added by the liquid crystal panel 103 is as shown by 103a. In the image 103a shown in FIG. 11, for example, the white portion is digital data representing 1 and the black portion is digital data representing 0. .
[0004]
On the other hand, the reference light is deflected by the mechanical scanner 105, passes through the beam splitter 106, and enters the grating mirror 107. The reference light is reflected by any part of the lattice mirror 107 and enters the hologram recording medium 104 via the beam splitter 106 and the lens 108.
[0005]
The object light and the reference light interfere with each other in the hologram recording medium 104, and the interference information is recorded in the hologram recording medium 104. Note that the angle of incidence of the reference light on the hologram material is determined by the scanner 105.
[0006]
When information is read, object light is reproduced by irradiating the hologram recording medium 104 with reference light at the same angle as when the information is recorded, and the reproduced object light is transferred to a CCD (CCD array) 109. Is led to. The CCD 109 photoelectrically converts the object light into an electric signal, and this signal is converted into digital data.
[0007]
[Problems to be solved by the invention]
In the hologram memory device as described above, an enormous amount of information can be recorded by using the multiple recording property of the hologram recording medium. However, this means that when reproducing the multiplex-recorded information, it is necessary to accurately reproduce the incident angle of the reference light on the hologram recording medium at the time of recording.
[0008]
Further, in the hologram memory device, since it is necessary to rapidly convert digital data added to the object light into electrical digital data without error, it is necessary to precisely adjust the positional relationship between the hologram recording material and the CCD 109. .
[0009]
Therefore, it is very difficult to record and reproduce different information by replacing the hologram material as a recording medium like a magnetic disk or an optical disk. For this reason, in the conventional hologram memory device, for example, the above-mentioned hologram memory device, the hologram recording medium 104 is provided as an immovable component, and the relative positional relationship between the hologram recording medium 104 and the CCD 109 also does not change. ing. However, if the hologram recording medium is a component of the device as in the conventional hologram memory device, the large-capacity recording capability inherent in the hologram memory cannot be fully utilized.
[0010]
The present invention has been made in view of the above circumstances, and provides a method of recording / reproducing information on a hologram recording medium capable of enabling a recording medium to be replaced, and is suitable for performing the method. It is an object to provide a hologram memory device.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a method of recording information to be recorded on a hologram recording medium by a hologram memory device having a spatial light modulator for adding information to object light by a plurality of information adding elements. Information and playback condition information indicating the playback condition of this information to be recorded And a second data area surrounding the first data area with only one of the bright and dark parts and further surrounding the first data area with only one of the bright and dark parts Creating a map for assigning to a second data area for assigning as an information addition element of the spatial light modulator, and a state of each information addition element of the spatial light modulator based on the created map Is adjusted to one of a first state in which the incident object light is guided to the hologram recording medium and a second state in which the incident object light is not guided to the hologram recording medium. A step of causing the object light to be incident on the hologram recording medium via the adjusted spatial light modulator, and causing the reference light to be incident on the hologram recording medium, and recording interference information between the object light and the reference light on the hologram recording medium. Recording the information on a medium, and when the object light is incident on the hologram recording medium via the spatial light modulator, the information with the first state is added. Only the object light incident on the element is incident on the hologram recording medium, whereby one of digital data 0 and 1 corresponding to the information-added element in the first state is written on the hologram recording medium. Combination of a bright part to represent and a dark part representing the other of 0 and 1 of digital data corresponding to the information addition element in the second state Having A two-dimensional image is projected, the reproduction condition information includes reproduction position detection information including dummy data, and the reproduction position detection information and the recording target information are allocated on the map in a predetermined positional relationship. Thus, at the time of reproduction, it is possible to specify the position of the recording target information on the two-dimensional image by specifying the position of the reproduction position detection information on the two-dimensional image to be reproduced. It is characterized by the following.
[0013]
Further, the present invention uses a hologram memory device provided with an image sensor on which an object light reproduced from a hologram recording medium is projected by irradiating a reference light, and recording target information and reproduction condition information indicating its reproduction condition. In the method for reproducing the information to be recorded from the hologram recording medium on which the information including is recorded, the provisional reading step of temporarily reading out the information added to the object light by the image sensor, and the reproduction condition information from the read out information Extracting the recording target information based on the extracted reproduction condition information, and adjusting the reproduction condition based on the extracted reproduction condition information; and reading the recording target information based on the adjusted reproduction condition. , The object light is a bright portion representing one of digital data 0 and 1, and a dark portion representing the other of digital data 0 and 1. And a second data area surrounding the first data area with only one of the bright part and the dark part surrounding the first data area with only one of the bright part and the dark part. The reproduction condition information is projected on the image sensor as a two-dimensional image, and the reproduction condition information includes dummy data. Having Including playback position detection information, the playback position detection information and the recording target information are allocated on the two-dimensional image with a predetermined positional relationship, and the extracting step is performed on the image sensor. Specifying a position of an area corresponding to the reproduction position detection information on the two-dimensional image, wherein the adjusting step is based on a position of the area corresponding to the reproduction position detection information specified in the extraction step. The method further includes a step of determining whether the object light is correctly projected on the predetermined position of the image sensor, and a step of adjusting a reproduction condition based on the determination.
[0014]
According to the present invention, there is provided a hologram memory device for recording information to be recorded on a hologram recording medium, a space having means for generating object light and reference light, and a plurality of information addition elements for adding information to the object light. Create a map for allocating the optical modulator and the recording target information and the reproduction condition information indicating the reproduction condition of the recording target information to each information additional element of the spatial light modulator based on a predetermined rule. And a means for controlling the spatial light modulator based on the map, wherein each information adding element of the spatial light modulator is such that incident object light is guided to the hologram recording medium. And a second state in which incident object light is prevented from being guided to the hologram recording medium. Accordingly, the object light traveling toward the hologram recording medium via the spatial light modulator is a bright portion representing one of digital data 0 and 1 corresponding to the information-added element in the first state. And a two-dimensional image having a dark portion representing the other of 0 and 1 of digital data corresponding to the information-added element in the second state And a second data area surrounding the first data area with only one of the bright part and the dark part surrounding the first data area with only one of the bright part and the dark part. Is projected onto the hologram recording medium, and the reproduction condition information is dummy data. Having Including playback position detection information, the map creation means is configured to allocate the playback position detection information and the recording target information on the map with a predetermined positional relationship, whereby during playback, By specifying the position of the reproduction position detection information on the two-dimensional image to be reproduced, it is possible to specify the position of the recording target information on the two-dimensional image.
[0015]
In addition, the present invention provides a hologram memory device that reproduces recording target information from a hologram recording medium on which information including recording target information and reproduction condition information indicating reproduction conditions of the recording target information is recorded. An image sensor onto which the object light reproduced when the hologram recording medium is irradiated with the reference light is projected; an extraction means for extracting reproduction condition information from information read by the image sensor; Adjusting means for adjusting the reproduction condition of the information based on the reproduction condition information among the read information, wherein the reproduction condition information is dummy data. Having Playback position detection information, wherein the playback position detection information and the recording target information are allocated on the two-dimensional image in a predetermined positional relationship, and the extraction unit outputs digital data 0 and 1 A bright part expressing one and a dark part expressing the other of 0 and 1 of digital data And a second data area surrounding the first data area with only one of the bright part and the dark part and surrounding the first data area with only one of the bright part and the dark part. Means for specifying a position of an area corresponding to the reproduction position detection information of the two-dimensional image from object light projected on the image sensor as a two-dimensional image; Means for determining whether the object light is correctly projected on a predetermined position of the image sensor based on the position of the area corresponding to the playback position detection information, and means for adjusting the playback condition based on the determination. It is characterized by including.
[0016]
Further, the present invention provides a hologram recording medium in which interference information between an object light to which information is added and a reference light that interferes with the object light is recorded, wherein information recorded in the hologram recording medium includes information to be recorded. And reproduction condition information indicating a reproduction condition of the information to be recorded. The information recorded on the hologram recording medium includes a bright portion representing one of digital data 0 and 1 on the hologram recording medium. And combination of dark parts representing the other of 0 and 1 of digital data And a second data region surrounding the first data region with only one of the bright and dark portions surrounding the first data region with only one of the bright portion and the dark portion. The interference information between the object light projected as a two-dimensional image and the reference light, wherein the reproduction condition information is dummy data. Having The playback position detection information includes the playback position detection information, and the playback position detection information and the recording target information are assigned in a predetermined positional relationship to the two-dimensional image. By specifying the position of the reproduction position detection information on an image, it is possible to specify the position of the recording target information on the two-dimensional image.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 to 8 are views showing an embodiment of the present invention.
[0018]
First, the overall configuration of the hologram memory device will be described. As shown in FIG. 1, the hologram memory device includes a light source device 1 that generates light having good coherence, for example, a laser beam, and a beam splitter 2 that divides the laser light from the light source device 1 into reference light and object light. Have.
[0019]
A spatial light modulator 3 for adding information to the object light is provided on the optical path of the object light of the hologram memory device, and the spatial light modulator 3 is controlled by a modulator control unit 4. The spatial light modulator 3 is composed of, for example, a liquid crystal panel.
[0020]
In addition, as the spatial light modulator, for example, a DMD (digital micromirror array device) manufactured by TI (Texas Instrument Incorporated) can be used in addition to the liquid crystal panel. The addition of information to the object light by the DMD is performed by oscillating each micromirror constituting the DMD, and a part of the object light having a predetermined width is incident on the hologram recording medium by the micromirror oriented in the first direction. This is performed by deflecting the remaining part of the object light in a direction that does not enter the hologram recording medium by a micromirror that is reflected as described above and faces in the second direction. When the object light is reflected in different directions as described above, when the object light is projected on a plane perpendicular to the optical path, a projection image similar to a projection image 60 described later is obtained. In this way, information can be added to the object light by the DMD.
[0021]
On the optical path of the reference light, a reference light deflector 10 is provided as a means for adjusting the incident angle of the reference light on the hologram recording medium 5. A deflector controller 20 for controlling the operation of the deflector 10 is provided.
[0022]
An image sensor 30 in which photoelectric conversion elements such as CCDs are arranged in an array is provided on the optical path of the object light reproduced from the hologram recording medium 5.
[0023]
As shown in FIG. 2, the image sensor 30 is mounted on an image sensor holder 40. The image sensor holder 40 has four piezoelectric elements 42, 43, 44, on a mounting table 41 fixed to the hologram memory device main body. Attached via 45. Each piezoelectric element is controlled by the image sensor control unit 8.
[0024]
The image sensor 30 provided in the above-described mode is configured to apply the same voltage to the piezoelectric elements 42 and 43 or to apply the same voltage to the piezoelectric elements 44 and 45 so that the plane perpendicular to the optical path of the object light is applied. It can be translated upward.
[0025]
The image sensor 30 rotates and moves on a plane perpendicular to the optical path of the object light by applying a reverse voltage to the piezoelectric elements 42 and 43 or by applying a reverse voltage to the piezoelectric elements 44 and 45. You can do it.
[0026]
The mechanism for displacing the image sensor 30 is not limited to the above-described mechanism, and another type of actuator may be used.
[0027]
The above-described image sensor control unit 8, deflector control unit 20, and modulator control unit 3 are controlled by a central control arithmetic unit 7 that controls the entire hologram memory device. Is connected to the input / output device 9.
[0028]
Further, as schematically shown in FIG. 1, the hologram memory device is provided with a holding device 6 for detachably holding the hologram recording medium 5.
[0029]
Next, the configuration of the reference light deflector 10 will be described.
[0030]
The reference light deflector 10 has rotating mirrors 11 and 12 sequentially arranged on the optical path of the reference light. Of these, the rotating mirrors 11 and 12 are provided such that their respective reflecting surfaces face each other, and are rotatable by actuators (not shown) around respective rotating axes 11a and 12a facing in the same direction. .
[0031]
The reference light deflector 10 changes only the incident angle without changing the incident position of the reference light on the hologram recording medium 5 by simultaneously rotating the rotating mirrors 11 and 12 as described in detail below. You can do it.
[0032]
That is, as shown in FIG. 3, when the turning mirrors 11 and 12 are at the solid line position in FIG. 3, the reference light reflected by the turning mirror 11 passes through the point P1 on the reflection surface of the turning mirror 12 and becomes a hologram. The light enters the point Q of the recording medium 5.
[0033]
With reference to the solid line position, the rotating mirror 11 is rotated clockwise by a predetermined angle so as to be at the position indicated by the two-dot chain line. Rotate in the direction. As a result, the reference light reflected by the rotating mirror 11 passes through the point P2 on the reflecting surface of the rotating mirror 12, and is stored in the hologram recording medium 5 in the same manner as when the rotating mirrors 11 and 12 are at the solid line positions. It is incident on point Q.
[0034]
As can be understood from the above description, the reference light deflector 10 has a function of changing only the angle of incidence on the hologram recording medium 5 without changing the position of incidence on the hologram recording medium 5. Note that the relationship between the rotation angles required for each of the turning mirror 11 and the turning mirror 12 to realize the above function can be easily calculated by a geometric calculation.
[0035]
The configuration of the reference light deflector 10 is not limited to the above. That is, in addition to the above-described configuration developed by the present inventor, for example, by using a known configuration in which an acousto-optic element and a so-called 4f optical system are combined, only the incident angle of the reference light can be changed without changing the incident position of the reference light. It is possible to realize the function of changing.
[0036]
Next, the configuration of the deflector controller 20 will be described. As shown in FIG. 1, the deflector controller 20 includes a sensor 21 for monitoring the turning angles of the two turning mirrors 11 and 12 of the reference light deflector 10, a turning angle of each turning mirror, and hologram recording. A database 22 storing a relational expression with a nominal incident angle θn of the reference light to the medium (the definition of the “nominal incident angle” will be described later), an arithmetic unit 23, and a calibration operation (the contents of the calibration operation will be described later) 2), a memory 24 for storing the relationship between the rotation angles of the rotation mirrors 11 and 12 and the angle of incidence of the reference light on the hologram recording medium, and the rotation mirror 11 and And a driver 25 for driving the drive 12.
[0037]
In FIG. 1, reference numeral 71 denotes a beam expander, 72 and 73 denote reflecting mirrors, 74 and 75 denote Fourier transform lenses, and 76 denotes a collimator lens. These components are publicly known, and These components are not referred to in the following description because they are not directly related to the gist of the present invention.
[0038]
Next, the hologram recording medium 5 used in the present embodiment will be described. As shown in FIG. 8A, the hologram recording medium 5 includes a main body 5a made of a hologram material such as lithium niobate or a photopolymer, and a frame 5b supporting the main body 5a. The holding device 6 holds the hologram recording medium 5 at a predetermined position in the hologram memory device by supporting the frame 5b of the hologram recording medium 5.
[0039]
Next, the operation of the hologram memory device having the above configuration will be described. Before proceeding with the following description, the reason why the concept of “nominal incident angle θn” is introduced in the present embodiment and “nominal incident angle θn” will be described. The definition of terms will be described.
[0040]
The true value of the incident angle of the reference light on the hologram recording medium 5 (hereinafter, referred to as the “actual incident angle θr”; see FIG. 1) indicates not only the operating state of the reference light deflector 10 but also the assembly accuracy of the hologram memory device. Holographic recording medium 5 may vary depending on individual factors, such as the accuracy of attachment of the hologram recording medium 5 to the holding device 6, and the like. This poses a problem when data is exchanged between hologram memory devices manufactured according to the same standard. This is because, in order to reproduce the information multiplex-recorded in the hologram memory device, the incident angle of the reference light at the time of reproduction on the hologram recording medium 5 must exactly match the incident angle at the time of recording.
[0041]
In order to make the incident angles at the time of recording and reproduction coincide with each other, the actual incident angle θr is recorded together with the information to be recorded, and the incident angle of the reference light at the time of reproduction is determined based on the recorded actual incident angle θr data. However, it is extremely difficult to measure the actual incident angle θr.
[0042]
In order to solve this problem, in this embodiment, data of the nominal incident angle θn is recorded on the hologram recording medium 5 together with the information to be recorded at the time of recording.
[0043]
Here, the nominal angle of incidence θn means that the hologram memory device and the hologram recording medium 5 are manufactured without any manufacturing error, and that the hologram recording medium 5 is held by the holding device 6 in an ideal state. This is a hypothetical incident angle determined on the basis of only the operating state of the reference light deflector 10.
[0044]
The above is the definition of the term of the nominal incident angle θn. Therefore, the nominal incident angle θn is different from the actual incident angle θr in the individual production accuracy of the hologram memory device and the hologram recording medium 5 and the hologram recording medium for the holding device 6. 5 always includes an error caused by the mounting accuracy.
[0045]
Hereinafter, the operation of the present embodiment will be described.
[0046]
First, digital data to be recorded (recording target information) is input from the input / output device 9, and the digital data is transmitted to the central control arithmetic unit 7.
[0047]
Next, the rotation angle of the reference light deflector 10 with respect to the reference position of the turning mirrors 11 and 12 is detected by the sensor 21 of the deflector control unit 20, and the rotation angle data is transmitted to the calculation unit 23 of the deflector control unit 20. Is done.
[0048]
The relational expression between the operation state of the reference light deflector 10 (that is, the rotation angles of the rotating mirrors 11 and 12) and the nominal incident angle θn is stored in the database 22 of the deflector control unit 20, and the calculation unit 23 The relational expression is extracted from 22 and the nominal incident angle θn of the reference light to the hologram recording medium 5 at the present time is calculated. Here, for example, when the value of the nominal incident angle θn is β1, this value β1 is transmitted to the central control calculation unit 7. The following description will be made on the assumption that the actual incident angle θr at this point is α1.
[0049]
The central control calculation unit 7 encodes the data β1 of the nominal incident angle θn. The central control arithmetic unit 7 converts the encoded nominal incident angle θn data β1 and the digital data (recording target information) input from the input / output device 9 and the dummy data generated by the central control arithmetic unit 7 into The map is created by arranging (mapping) based on a predetermined rule.
[0050]
FIG. 4A shows the created map 50. In FIG. 4A, 1-bit data is mapped to each cell in which any of the codes A1, A2, B0, and B1 is entered.
[0051]
As shown in FIG. 4A, the map 50 has a rectangular first data area 51 with a code A1 or A2, and a code B0 or B1 surrounding the first area 51 in a frame shape. And a second data area 52. The second data area 52 includes an area 52a directly surrounding the first data area 51 and an area 52b further surrounding the area 52a.
[0052]
Here, a nominal incident angle θn of the reference light to the hologram recording medium 5 is provided in an area 51a for the first n bits (5 bits in FIG. 4A) of the first data area 51, which is denoted by the reference symbol A1. (Reference light information) is written. Here, the bit number n is determined based on the recording multiplicity, and the higher the multiplicity, the more the bit number n is allocated.
[0053]
The “recording target information” input from the input / output device 9 is assigned to the area 51b to which the reference symbol A2 is assigned. In the present specification, the “recording target information” refers to the original information to be recorded on the hologram recording medium 5, for example, audio information, image information, document information, and the like (these are merely examples, and “recording target information” (The term does not limit the concept of the term.)
[0054]
Then, in the areas to which reference numerals B0 and B1 are attached, that is, in the second data area 52, reproduction position detection data for specifying the position of the first data area 51 (hereinafter also referred to as "reproduction position detection information"). (Corresponding to the dummy data described above). The digital data 1 is written in the area 52a labeled B1, and the digital data 0 is written in the area 52b labeled B0. As will be described later, the digital data in the second data area 52 is used exclusively for specifying the first data area 51, and does not have any meaning as data itself.
[0055]
The above-described reference light information (area 51a) and reproduction position detection information (second data area 52) are collectively referred to as "reproduction condition information". That is, in the present specification, “reproduction condition information” means information used for reading “recording target information”.
[0056]
The format of the map 50 described above (the number of bits recorded on one page, the shape and positional relationship of each area, the number of bits allocated to each area, etc.) is standardized, and this standard is applied to all hologram memory devices. You.
[0057]
The above-described method of allocating data to the map 50 shows the best mode for carrying out the present invention, but is not limited to this. That is, the second data area 52 to which the reproduction position detection information is allocated has a fixed positional relationship with the first data area 51 as long as the position of the first data area 51 to which the recording target information is allocated can be specified. Is sufficient. Further, the shape of the first data area 51 is not limited to a rectangular shape.
[0058]
The data of this map 50 is transmitted to the modulator controller 4, and the modulator controller 4 controls the state of each information addition element of the spatial light modulator 3 based on this map 50.
[0059]
Here, when the spatial light modulator 3 is a liquid crystal panel, the “information addition element” refers to one pixel or an aggregate of a plurality of pixels expressing one bit of information. When the spatial light modulator 3 is a DMD, it refers to one micromirror or an aggregate of a plurality of micromirrors expressing one bit of information. That is, the "information additional element" means one unit element expressing one bit of information in the spatial light modulator 3, and one unit of the information additional element is indicated by the first cell in FIG. 4B. It is.
[0060]
That is, when FIG. 4B shows the liquid crystal panel surface of the spatial light modulator 3, the hatched cells block the object light, and the cells left white allow the object light to pass. It shows that it is in a state. When FIG. 4B shows the reflecting surface of the micromirror of the spatial light modulator 3, the hatched square-shaped area reflects the object light so as not to enter the hologram recording medium. The white area indicates that the object light is reflected so as to be guided to the hologram recording medium.
[0061]
Then, the object light passes through the spatial light modulator 3 or is reflected by the spatial light modulator 3, thereby adding planar information that can be expressed as a two-dimensional image 60. That is, when the object light that has passed through the spatial light modulator 3 is projected on a plane perpendicular to the optical path of the object light, a two-dimensional image 60 expressed by light and dark as shown in FIG. 4B is obtained.
[0062]
The object light to which the information is added in this way enters the hologram recording medium 5.
[0063]
On the other hand, the reference light enters the hologram recording medium 5 via the reference light deflector 10 at a predetermined actual incident angle θr. The reference light interferes with the object light, and this interference information (interference fringes) is recorded on the hologram recording medium 5. As described above, one page of recording target information is recorded on the hologram recording medium 5. That is, information including recording target information and reproduction condition information is recorded on the hologram recording medium 5.
[0064]
When writing the information of the next page (recording target information), the reference light deflector 10 is adjusted to change the incident angle of the reference light on the hologram recording medium 5, and the recording target information is recorded in the same procedure as described above. A record is made. Also in this case, the recording of the nominal incident angle θn calculated based on the state of the reference light deflector 10 is similarly performed. That is, the reproduction condition information corresponding to the recording target information for one page is recorded.
[0065]
When information of a plurality of pages (recording target information) is recorded, the recording is performed so that the page number (number indicating whether the page is the Nth page) N and the value of the nominal incident angle θn uniquely correspond to each other. Done. Further, the difference between the nominal incident angles θn of the reference beams respectively corresponding to the pages adjacent to each other is always constant. Accordingly, the difference between the actual incident angles θr of the reference beams respectively corresponding to the pages adjacent to each other is always constant (see FIG. 6).
[0066]
Therefore, in the area 51a of the first data area 51 of the map 50 described above, reference light information uniquely corresponding to the nominal incident angle θn, for example, the page number N may be recorded.
[0067]
Next, an operation when the recording target information thus recorded is reproduced by another hologram memory device will be described with reference to a flowchart shown in FIG.
[0068]
The hologram memory devices and the hologram recording medium 5 shown in the present embodiment are manufactured under a predetermined standard, and the specifications of the hologram memory devices are the same.
[0069]
First, the hologram recording medium 5 is removed from the hologram memory device on which recording has been performed, and is mounted on the holding device 6 of the hologram memory device for reproduction.
[0070]
When the reproduction is performed, first, the page number N of the recording target information to be read is input from the input / output device 9, and the page number of the recording target information recorded on the hologram recording medium 5 is read. Is specified (step S100). In the following description, for the sake of simplicity, the case where the information to be recorded on the first page in which the value of the actual incident angle θr is α1 and the value of the nominal incident angle θn is β1 at the time of recording is read out. An example will be described.
[0071]
The central control calculation unit 7 obtains a nominal incident angle θn corresponding to the designated page number 1. As described above, the page number N uniquely corresponds to the nominal incident angle θn, and the relationship between the page number N and the nominal incident angle θn is common to all devices. The value of the nominal incident angle θn thus obtained is β1. This value β1 is transmitted to the deflector controller 20.
[0072]
The arithmetic unit 23 of the deflector control unit 20 calculates the nominal incident angle θn based on the relational expression between the nominal incident angle θn (in the present reproducing apparatus) and the operation state of the reference light deflector 10 stored in the database 22. The rotation angles of the turning mirrors 11 and 12 of the reference light deflector 10 for realizing the value β1 are calculated, and the reference light deflector 10 is adjusted based on the calculation result (step S101).
[0073]
Next, the hologram recording medium 5 is irradiated with reference light, whereby object light is reproduced from the hologram recording medium 5. The reproduced object light is read by the image sensor 30 (step S102).
[0074]
Here, FIG. 6 is a diagram schematically showing a change in the intensity of the reproduced object light when the actual incident angle θr of the reference light is sequentially changed on the hologram recording medium 5 on which the multiplex recording has been performed. .
[0075]
As shown in FIG. 6, peaks of the intensity distribution of the object light corresponding to each page appear at certain angles. When the actual incident angle θr of the reference light slightly deviates from the actual incident angle θr at which the intensity of the object light indicates a peak, the intensity of the object light is greatly attenuated. Also, in FIG. 6, the lower limit (threshold) of the object light intensity at which the image sensor 30 can recognize the information added to the object light as information is indicated by a broken line.
[0076]
Here, due to a positioning error of the hologram recording medium 5 with respect to the holding device 6 or an individual difference of the device, the value of the actual incident angle θr of the reference light is equal to the value α2 of the actual incident angle θr corresponding to the second page. It is assumed that αr is between the actual incident angle θr and the value α3 corresponding to the third page (see FIG. 6).
[0077]
In this case, since the intensity of the object light is equal to or less than the threshold value indicated by the broken line, the image sensor 30 is in a state where it cannot recognize information added to the object light as information.
[0078]
The central control arithmetic unit 7 monitoring the intensity of the image signal photoelectrically converted by the image sensor 30 determines whether or not the intensity of the image signal is sufficient (step S103). In this case, a scan command signal is transmitted to the deflector controller 20.
[0079]
The deflector control unit 20 appropriately rotates the turning mirrors 11 and 12 of the reference light deflector 10 via the driver 25, and continuously changes the actual incident angle θr of the reference light (Step S104).
[0080]
The central control calculation unit 7 monitors the intensity of the image signal from the image sensor 30 that changes in response to the change in the actual incident angle θr of the reference light, and when the intensity of the image signal becomes maximum (in FIG. 6, At the time when the value of the actual incident angle θr becomes α3), a scanning stop signal is transmitted to the deflector controller 20. Then, the operation of the reference light deflector 10 stops. By the processing in step S104, the image sensor 30 can sufficiently recognize the information added to the object light.
[0081]
Here, before describing the next processing step, how the image sensor 30 of the hologram memory device reads the information added to the object light will be described.
[0082]
When the reproduced object light is incident on the image sensor 30, an image 60 as shown in FIG. 4B is projected on the imaging surface of the image sensor 30.
[0083]
In the hologram memory device, the image sensor 30 converts the first data area 61 corresponding to the first data area 51 of the map 50 (see FIG. The principle is to read in a specific area 31 (see FIGS. 2 and 7). Therefore, information (brightness / darkness information) added to each cell constituting the image 60 (hereinafter, one cell is referred to as an “image element”) is read by a specific pixel of the image sensor 30 in principle. It has become. Preferably, at least four pixels are assigned to one image element.
[0084]
As described above, by specifying the pixels from which each image element is read, the image signal photoelectrically converted by the image sensor 30 can be converted into data in a map 50 format as shown in FIG. Can be restored.
[0085]
Hereinafter, the information reading operation will be described continuously.
[0086]
Next, the central control calculation unit 7 determines the positional relationship between the first data area 61 of the image 60 projected on the imaging surface of the image sensor 30 and the specific area 31 of the image sensor 30 (Step S106). .
[0087]
Here, the position where the first data area 61 of the image 60 is projected is shifted from the area 31 of the image sensor 30 due to a positioning error of the hologram recording medium 5 with respect to the holding device 6 or an individual difference of the device. It is normal to be. The positional relationship of the first data area 61 of the image 60 with respect to the area 31 of the image sensor 30 may be a parallel-moved relation as shown in FIG. 7A, a rotationally-moved relation as shown in FIG. As shown in FIG. 7C, one of the relations in which both the parallel movement and the rotational movement are performed.
[0088]
The positional relationship between the first data area 61 and the area 31 is calculated based on an image signal corresponding to a frame-shaped second data area 62 surrounding the outside of the first data area 61. Is done.
[0089]
The central control calculation unit 7 calculates the position of the outer bright area 62b (preferably, the four corners of the area 62b) in the second data area 62 of the image 60 on the imaging surface of the image sensor 30.
[0090]
In the present embodiment, a dark area 62 a inside the second data area 62 is located between the area 62 b of the second data area 62 of the image 60 and the first data area 61. Therefore, it is easy to recognize the first data area 61. That is, when the bright area 62b is provided directly outside the first data area 61 without providing the dark area 62a, the position of the first area may not be recognized correctly (this may be the case when the projected image Is remarkable when rotating with respect to the imaging surface). On the other hand, in the present embodiment, since the first data area 61 and the bright area 62b of the second data area 62 are separated by the dark area 62a, it is necessary to accurately specify the position of the bright area 62b. Can be.
[0091]
Next, the central control operation unit 7 specifies the current position of the first data area 61 of the image 60 based on the data indicating the position of the bright area 62b of the second data area 62 of the image 60, and The amount of movement of the image sensor 30 required to completely match the data area 61 with the area 31 on the imaging surface of the image sensor 30 is calculated. Data of the calculated required movement amount is transmitted to the image sensor control unit 8.
[0092]
Upon receiving this, the image sensor control unit 8 calculates the voltage to be applied to the piezoelectric elements 42 to 45 for moving the image sensor based on the data of the required movement amount, and applies the calculated voltage to each of the piezoelectric elements 42 to 45. Apply. Thereby, the first data area 61 of the image 60 and the area 31 of the imaging surface of the image sensor 30 completely match (Step S107).
[0093]
In step S107, the first data area 61 of the image 60 is matched with the area 31 of the imaging surface of the image sensor 30 by moving the image sensor 30, that is, the projection position of the object light on the image sensor 30 Was performed, but the present invention is not limited to this.
[0094]
That is, the processing equivalent to the above processing may be performed only by the arithmetic processing without moving the image sensor 30. In this arithmetic processing, a signal from the image sensor 30 is transformed by software so that the image 60 projected from the predetermined position of the image sensor 30 can be processed as being projected at the predetermined position of the image sensor 30. It is implemented by doing.
[0095]
In particular, since the processing for correcting the parallel movement as shown in FIG. 7A can be easily performed by the arithmetic processing, the correction processing for the rotational movement is performed by moving the image sensor 30, and the correction processing for the parallel movement is performed. It is also preferable to perform the above by arithmetic processing.
[0096]
In the present embodiment, the relative positional relationship between the image sensor and the object light is corrected by displacing the image sensor 30, but the present invention is not limited to this. That is, a mechanism for moving the holding device 6 may be provided, and the hologram recording 5 may be moved by operating the mechanism, thereby correcting the positional relationship. Since the reference light is incident on the hologram recording medium 5 with a certain width, the correction can be performed by such a method.
[0097]
By the way, the projected image also moves in the optical path direction of the object light reproduced due to the displacement of the hologram recording medium 5 or the like, that is, in the normal direction of the imaging surface of the image sensor 30. No correction operation is required because the influence is small.
[0098]
When step S107 is completed, the information (recording target information and reproduction condition information) added to the reproduced object light can be read. The information recorded in the data area 61 is provisionally read (step S108).
[0099]
Thereby, the value (reference light information) of the nominal incident angle θn of the reference light at the time of recording, which is recorded in the area 51a of the first data area 51, is read out. In this case, since the wrong third page has been read, the value of the read nominal incident angle θn is β3. The central control operation unit 7 transmits the value β3 to the deflector control unit 20.
[0100]
Next, the calculation unit 23 of the deflector control unit 20 calculates the nominal incident angle θn based on the current state of the reference light deflector 10 using the relational expression stored in the database 22, and centrally controls the calculated value. The value is compared with the value of the nominal incident angle θn sent from the calculation unit 7 (step S109).
[0101]
Normally, there is a difference between the two nominal incident angles due to individual differences of the hologram memory device, positioning errors of the hologram recording medium, and the like. In this example, the differences are as follows.
[0102]
That is, as shown in FIG. 6, when step S104 is completed, the reference light modifier 10 is in a state where the reference light is incident on the hologram recording medium 5 at the actual incident angle α3. Here, the hologram memory device performing the reproduction uses the nominal incidence of the reference light at the present time based on the relational expression between the state of the reference light modifier 10 stored in the database 22 and the nominal incidence angle θn of the reference light. It is recognized that the value of the angle θn is β1 + (α3−αr).
[0103]
Therefore, there is a difference of β3− {β1 + (α3−αr)} between the nominal incident angle read from the hologram recording medium 5 and the nominal incident angle recognized by the calculation unit 23 of the deflector control unit 20. There is.
[0104]
The calculation unit 23 calibrates the relational expression read from the database 22 based on the difference β3− {β1 + (α3−αr)}. Specifically, for example, when the reference light modifier 10 is in a state where the reference light enters the hologram recording medium 5 at the actual incident angle α3, the arithmetic unit 23 determines that the nominal incident angle is β3. Calibrate the relational expression so that it can be recognized. Then, the arithmetic unit 23 stores the calibrated relational expression in the memory 24 (step S110).
[0105]
Thereafter, the calculation of the nominal incident angle θn in the deflector controller 20 is performed based on the calibrated relational expression stored in the memory 24. The relational expression stored in the memory 24 is not changed unless the mounting state of the hologram recording medium 5 changes.
[0106]
Next, the central control operation unit 7 obtains the page number N currently read based on the value of the nominal incident angle θn read from the hologram recording medium 5 and matches the page number specified in step S101. Is checked (step S111).
[0107]
In this specific example, since it is understood that the third page is read while the first page is specified, the central control calculation unit 7 sets the incident angle of the reference light to an amount corresponding to two pages. A command is issued to the deflector controller 20 so as to shift, and the deflector controller 20 receiving the command rotates the rotation mirrors 11 and 12 so as to shift the incident angle of the reference light by a predetermined angle (in this case, β3−β1). The corner is corrected (step S112).
[0108]
When step S112 ends, the information recorded on the designated page can be read correctly. The central control operation unit 7 restores the image signal transmitted from the image sensor 30 to data in the map 50 format. Further, the central control calculation unit 7 extracts the recording target information from the data in the map 50 format including the recording target information and the reproduction condition information, and outputs the information to the input / output device 9 (step S113). Thus, the reading of the recording target information is completed.
[0109]
In the above description, the operation when the hologram recording medium 5 recorded by one hologram memory device is read by another hologram memory device has been described. When the remaining portion is further recorded on the hologram recording medium 5 on which the recording has been partially performed by another hologram memory device, the already written information (reference light information) is once read out and the same as above. Then, a calibration process of the relational expression may be performed, and a nominal incident angle at the time of subsequent recording may be calculated and recorded based on the calibrated relational expression.
[0110]
That is, the nominal incident angle in another device is corrected with reference to the nominal incident angle recorded by the device that first writes information on the hologram recording medium 5.
[0111]
In the above embodiment, the matching between the devices is performed using the reference of the nominal incident angle. However, the present invention is not limited to this. Since the measurement of the actual incident angle is theoretically possible (although the configuration of the device is complicated), matching between the devices may be performed based on the actual incident angle.
[0112]
As described above, according to the present embodiment, even if there is a positioning error of the hologram recording medium or an error of the incident angle of the reference beam for reproduction, the error can be reduced without impairing the large-capacity recording of the hologram memory device. Correction can be made appropriately. For this reason, it is possible to provide a hologram memory device in which the hologram recording medium can be replaced and which can be used even in an environment having vibration or the like. Thereby, the following application examples can be realized.
[0113]
Next, a system to which the present embodiment is applied will be described.
[0114]
[First application example]
FIG. 9 shows an example in which the hologram memory device is applied to a video system including a video camera 81 and an editing device 82. A video image has a huge data amount even if data compression is performed, and a long-time shooting requires a large-capacity recording medium. However, the hologram memory device of the present embodiment is applied as a recording device of the video camera 81. This enables long-time shooting.
[0115]
Further, even if the mounting state of the hologram recording medium changes due to vibration or the like during photographing, photographing can be continued without any problem by the above-described position shift correction function and nominal incident angle calibration function.
[0116]
In addition, when the hologram recording on which the video information is recorded is detached from the video camera 81 and attached to the editing device 82, the problems of mechanical errors between the individual hologram memory devices and variations in the attachment state of the hologram recording medium are also described above. This can be solved by a position shift correction function and a nominal incident angle calibration function.
[0117]
[Second application example]
FIG. 10 shows an example in which the hologram memory device is applied to a so-called car navigation system. In a car navigation system, a large-capacity recording medium is required because it is necessary to provide wide area and detailed map information. Therefore, the hologram recording medium is used as a ROM (read only memory) storing map information.
[0118]
In this case as well, it is conceivable that the hologram recording medium may be misaligned due to vibrations during traveling or the like, and the image sensor may be misaligned due to aging. Thus, continuous use is possible without any problem. No special mechanical adjustment is required even when the apparatus changes over time.
[0119]
Note that this application example is not limited to application to a car navigation system, but can also be applied to a recording / reproducing device of an information device mounted on another moving body, for example, a ship or an airplane.
[0120]
[Third application example]
As still another application example, it is also possible to perform collation and retrieval of image data and the like by using the position shift correction function of the present embodiment.
[0121]
For example, consider searching for an image that matches a specific image from an image database. The images handled here include, for example, fingerprint images and data of official documents.
[0122]
Here, it is assumed that the image database handles binary images and is stored in the hologram recording medium in the form of an image as it is.
[0123]
In this application example, in addition to the configuration of the above-described embodiment, the image sensor 30 is provided with a memory function for recording a comparison image to be compared and a comparison function for each pixel. In advance.
[0124]
Then, the sequentially registered images are reproduced from the hologram recording medium, the positions of the reproduced images are aligned, and the images are compared at the same time.
[0125]
With this configuration, it is possible to search for an image without transferring a large amount of image data registered in the image database to the external memory.
[0126]
[Modification of hologram recording medium]
In the description of the above-described embodiment, the description has been made on the assumption that the hologram recording medium 5 is relatively small and that a plurality of pieces of information are recorded at one point in the hologram recording medium 5. However, as described above, the hologram memory device according to the present invention has an extremely excellent misalignment correction function and an incident angle calibration function. Each piece of information may be recorded. In this case, a mechanism for moving the holding device 6 is required.
[0127]
Further, as shown in FIG. 8B, the main body 5a of the hologram recording medium 5 may be formed in a disk shape. In this case, the hologram recording medium is chucked by the spindle motor 90 and held rotatably.
[0128]
In this case, by providing a mechanism capable of moving the spindle motor 90 in the radial direction of (the main body 5a of) the hologram recording medium, or by providing a mechanism for optically changing the incident position of the reference light (and the object light), It is possible to access the recording target information written at an arbitrary position on the hologram recording medium.
[0129]
In the above two modifications, the information to be recorded is recorded in a plurality of areas of the hologram recording medium. Therefore, information indicating the address of each area is used as one of the reproduction condition information in the above-described map. It is preferable that the data is allocated to the first data area 51 and recorded. Note that it is naturally possible to apply this modified example to the above three application examples.
[0130]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a hologram memory device that can exchange a recording medium between different devices and that can be used even in an environment having vibration or the like.
[Brief description of the drawings]
FIG. 1 is a view showing one embodiment of a hologram memory device according to the present invention, and is a schematic view showing the entire configuration of a hologram memory device.
FIG. 2 is a diagram illustrating an example of a unit that displaces an image sensor.
FIG. 3 is a diagram showing the configuration and operation of a reference light deflector.
FIG. 4A is a diagram showing a map for allocating information to each information addition element of the spatial light modulator, and FIG. 4B is controlled based on the map; The figure which shows the image obtained when the object light to which information was added by the spatial light modulator is projected on a plane. The cells in FIG. 4A and the cells in FIG. 4B correspond one-to-one.
FIG. 5 is a flowchart showing a procedure for reading recording target information.
FIG. 6 is a diagram showing a procedure for calibrating a nominal incident angle.
FIG. 7 is a diagram showing a mode of a positional shift of object light projected on an image sensor.
FIG. 8 is a diagram showing a configuration of a hologram recording medium.
FIG. 9 is a diagram showing an application example of the present invention.
FIG. 10 is a diagram showing an application example of the present invention.
FIG. 11 is a diagram showing a conventional hologram memory device.
[Explanation of symbols]
3 Spatial light modulator
5 Hologram recording medium
5a (hologram recording medium) body
10. Reference light deflector
30 Image sensor
50 Map (indicating information allocation)

Claims (10)

In a method of recording information to be recorded on a hologram recording medium by a hologram memory device including a spatial light modulator that adds information to object light by a plurality of information addition elements,
A first data area for allocating recording target information and reproduction condition information indicating a reproduction condition of the recording target information as a combination of a light part and a dark part, and an area surrounding the first data area with only one of the light part and the dark part Creating a second data area for allocating a second data area and a map for allocating the second data area to the information addition element of the spatial light modulator , further enclosing the second data area only in the other of the bright part and the dark part ;
Based on the created map, the state of each information adding element of the spatial light modulator is changed to a first state in which the incident object light is guided to the hologram recording medium or the incident object light is changed to the hologram recording medium. Adjusting to any one of the second states so as not to be guided to the medium;
The object light is incident on the hologram recording medium via the adjusted spatial light modulator, the reference light is incident on the hologram recording medium, and interference information between the object light and the reference light is recorded on the hologram recording medium. The process of
With
When the object light is incident on the hologram recording medium via the spatial light modulator, only the object light incident on the information addition element in the first state is incident on the hologram recording medium, On the hologram recording medium, a bright portion representing one of digital data 0 and 1 corresponding to the information additional element in the first state and the information additional element in the second state are provided. A two-dimensional image having a combination of dark areas representing the other of 0 and 1 of the digital data,
The reproduction condition information includes reproduction position detection information having dummy data, and the reproduction position detection information and the recording target information are allocated on the map in a predetermined positional relationship, whereby the reproduction A hologram recording medium, wherein the position of the recording target information on the two-dimensional image can be specified by specifying the position of the reproduction position detection information on the two-dimensional image to be reproduced. How to record information to be recorded in The method according to claim 1, wherein the reproduction condition information includes reference light information corresponding to an incident angle of the reference light on the hologram recording medium during recording. By using a hologram memory device having an image sensor that projects an object beam reproduced from a hologram recording medium by irradiating a reference beam, information including recording target information and reproduction condition information indicating its reproduction condition is recorded. In the method of reproducing the information to be recorded from the hologram recording medium,
A provisional reading step of temporarily reading information added to the object light by the image sensor, an extracting step of extracting reproduction condition information from the read information, and adjusting reproduction conditions based on the extracted reproduction condition information. An adjustment process;
Recording target information reading step of reading the recording target information according to the adjusted reproduction condition,
In the provisional readout step, the object light includes a first data area having a combination of a bright part representing one of digital data 0 and 1 and a dark part representing the other of digital data 0 and 1, and the first data area. Projecting on the image sensor as a two-dimensional image having a second data area surrounding a region surrounding only one of the bright part and the dark part and further surrounding only the other of the bright part and the dark part ,
The reproduction condition information includes reproduction position detection information having dummy data, and the reproduction position detection information and the recording target information are allocated on the two-dimensional image with a predetermined positional relationship,
The extracting step includes a step of specifying a position of an area corresponding to the reproduction position detection information on the two-dimensional image projected on the image sensor,
The adjusting step is a step of determining whether or not the object light is correctly projected on a predetermined position of the image sensor based on the position of the area corresponding to the reproduction position detection information specified in the extracting step. Adjusting the reproduction conditions based on the hologram recording medium. The reproduction condition information includes reference light information corresponding to an incident angle of the reference light to the hologram recording medium during recording,
The extracting step further includes a step of extracting the reference light information,
The adjusting step further includes a step of changing an incident angle of the reference light to the hologram recording medium based on the extracted reference light information,
4. The method of claim 3, wherein: In a hologram memory device for recording information to be recorded on a hologram recording medium,
Means for generating object light and reference light;
A spatial light modulator having a plurality of information adding elements for adding information to the object light,
Map creating means for creating a map for allocating recording target information and reproduction condition information indicating a reproduction condition of the recording target information to each information additional element of the spatial light modulator based on a predetermined rule; and ,
Means for controlling the spatial light modulator based on the map,
With
Each information adding element of the spatial light modulator has a first state in which incident object light is guided to the hologram recording medium or a second state in which incident object light is not guided to the hologram recording medium. And the object light traveling toward the hologram recording medium via the spatial light modulator is transmitted to the information adding element in the first state. A combination of a two-dimensional image having a bright portion corresponding to one of digital data 0 and 1 and a dark portion corresponding to the other of digital data 0 and 1 corresponding to the information-added element in the second state. the area surrounding only one of the first data region and the first data area a bright portion and a dark portion and further having a second data area surrounding only the bright portion and the dark portion of the other having The adapted to be projected onto the holographic recording medium,
The reproduction condition information includes reproduction position detection information having dummy data,
The map creating means is configured to allocate the reproduction position detection information and the recording target information on the map with a predetermined positional relationship, whereby, during reproduction, a two-dimensional image to be reproduced is displayed. A hologram memory device, wherein the position of the recording target information on the two-dimensional image can be specified by specifying the position of the reproduction position detection information. The reproduction condition information includes reference light information corresponding to an incident angle of the reference light to the hologram recording medium at the time of recording, and the hologram memory device transmits the reference light to the hologram recording medium at the time of recording. 6. The hologram memory device according to claim 5, further comprising: means for detecting reference light information corresponding to the incident angle. In a hologram memory device that reproduces recording target information from a hologram recording medium on which information including recording target information and reproduction condition information indicating reproduction conditions of the recording target information is recorded
Means for generating a reference light;
An image sensor on which an object light to be reproduced when the reference light is applied to the hologram recording medium is projected,
Extracting means for extracting reproduction condition information from information read by the image sensor;
Adjusting means for adjusting the reproduction condition of the information based on the reproduction condition information among the information read by the image sensor;
With
The reproduction condition information includes reproduction position detection information having dummy data, and the reproduction position detection information and the recording target information are allocated on the two-dimensional image with a predetermined positional relationship,
The extracting means includes: a first data area having a combination of a bright portion expressing one of 0 and 1 of digital data and a dark portion expressing the other of 0 and 1 of digital data; The reproduction of the two-dimensional image from the object light projected on the image sensor as a two-dimensional image having a second data region surrounding a region surrounded by only one of the dark part and the dark part. Having means for specifying the position of the area corresponding to the position detection information,
The adjusting unit determines whether the object light is correctly projected on a predetermined position of the image sensor based on a position of an area corresponding to the reproduction position detection information specified by the extracting unit, and based on the determination. A hologram memory device comprising: The reproduction condition information includes reference light information corresponding to an incident angle of the reference light to the hologram recording medium during recording,
The extracting means further includes a means for extracting the reference light information,
The adjusting means further includes means for changing an incident angle of the reference light on the hologram recording medium based on the extracted reference light information,
The hologram memory device according to claim 7, wherein: In the hologram recording medium in which interference information between the object light to which the information is added and the reference light that interferes with the object light is recorded,
The information recorded on the hologram recording medium includes recording target information and reproduction condition information indicating a reproduction condition of the recording target information,
The information recorded on the hologram recording medium is a first data having a combination of a bright portion representing one of digital data 0 and 1 and a dark portion representing the other of digital data 0 and 1 on the hologram recording medium. An object light projected as a two-dimensional image having a region and a second data region surrounding the first data region with only a bright portion and a dark portion surrounding a region surrounding only the bright portion and a dark portion; Interference information with
The reproduction condition information includes reproduction position detection information having dummy data, and in the two-dimensional image, the reproduction position detection information and the recording target information are allocated with a predetermined positional relationship. Thereby, at the time of reproduction, it is possible to specify the position of the recording target information on the two-dimensional image by specifying the position of the reproduction position detection information on the two-dimensional image to be reproduced. Hologram recording medium. The hologram recording medium according to claim 9 , wherein the reproduction condition information includes reference light information corresponding to an incident angle of the reference light on the hologram recording medium at the time of recording.

Images