Method for preparing a hologram recording medium

Abstract

Two original images to be recorded are prepared as data (S 10 ). A plurality of unit regions, each having an adequate area to record interference fringes of visible light, are defined and positioned on a hologram recording surface (S 20 ). A gradation pattern, with which appearance probabilities of two record attributes gradually change in space, is overlapped onto the recording surface, and to each unit region, one of either record attributes is assigned according to the appearance probabilities of the respective record attributes at each individual position (S 30 ). In each unit region, to which the first record attribute is assigned, the first original image is recorded as an interference fringe pattern, a diffraction grating pattern, or a scattering structure pattern, and in each unit region, to which the second record attribute is assigned, the second original image is recorded as an interference fringe pattern, a diffraction grating pattern, or a scattering structure pattern (S 40 ), and a record pattern is formed on a physical medium (S 50 ).

1 . A hologram recording medium preparing method comprising:
 an original image preparing step of preparing, as data, a specific original image to be recorded;
 a unit region defining step of defining and positioning a plurality of unit regions, each having an adequate area for recording interference fringes of visible light, on a hologram recording surface, 
 an attribute assigning step of assigning a specific record attribute, which indicates that the specific original image is to be recorded, to a portion of the plurality of unit regions; 
 a record pattern preparing step of determining, for each unit region assigned with the specific record attribute, an interference fringe pattern, a diffraction grating pattern, or a scattering structure pattern based on the specific original image to prepare data indicating a predetermined record pattern to be formed on the recording surface; and 
 a medium forming step of forming the record pattern on a physical medium. 
   
   
   
       2 . A hologram recording medium preparing method comprising:
 an original image preparing step of preparing, as data, a specific original image to be recorded;   a unit region defining step of defining and positioning a plurality of unit regions, each having an adequate area for recording interference fringes of visible light, on a hologram recording surface;   an attribute assigning step of defining a gradation pattern, which expresses that an appearance probability of a predetermined attribute gradually changes in space, and assigning a specific record attribute, which indicates that the specific original image is to be recorded, to a portion of the unit regions that is selected according to an appearance probability at each position when the gradation pattern is overlapped onto the recording surface;   a record pattern preparing step of determining, for each unit region assigned with the specific record attribute, an interference fringe pattern, a diffraction grating pattern, or a scattering structure pattern based on the specific original image to prepare data indicating a predetermined record pattern to be formed on the recording surface; and   a medium forming step of forming the record pattern on a physical medium.   
   
   
       3 . A hologram recording medium preparing method comprising:
 an original image preparing step of preparing, as data, a plurality M of original images to be recorded;   a unit region defining step of defining and positioning a plurality of unit regions, each having an adequate area for recording interference fringes of visible light, on a hologram recording surface;   an attribute assigning step of defining a gradation pattern for each of the M original images, respectively, which expresses that an appearance probability of a record attribute corresponding to an original image gradually changes in space, and assigning any one of record attributes to each unit region according to appearance probabilities of the respective record attributes at each individual position when the respective gradation patterns are overlapped onto the recording surface;   a record pattern preparing step of determining, for each individual unit region, an interference fringe pattern, a diffraction grating pattern, or a scattering structure pattern based on a specific original image corresponding to an assigned record attribute to prepare data indicating a predetermined record pattern to be formed on the recording surface, and   a medium forming step of forming the record pattern on a physical medium.   
   
   
       4 . A hologram recording medium preparing method comprising:
 an original image preparing step of preparing, as data, a first original image and a second original image to be recorded;   a unit region defining step of defining and positioning a plurality of unit regions, each having an adequate area for recording interference fringes of visible light, on a hologram recording surface;   an attribute assigning step of defining a gradation pattern, which expresses that an appearance probability of a first record attribute and an appearance probability of a second record attribute gradually change in space, and performing a process of assigning one of either the first record attribute or the second record attribute or not assigning either attribute on each unit region according to appearance probabilities of the respective record attributes at each individual position when the gradation pattern is overlapped onto the recording surface;   a record pattern preparing step of determining an interference fringe pattern, a diffraction grating pattern, or a scattering structure pattern based on the first original image for each unit region to which the first record attribute was assigned, and determining an interference fringe pattern, a diffraction grating pattern, or a scattering structure pattern based on the second original image for each unit region to which the second record attribute was assigned to prepare data indicating a predetermined record pattern to be formed on the recording surface; and   a medium forming step of forming the record pattern on a physical medium.   
   
   
       5 . The hologram recording medium preparing method according to  claim 4 , wherein the attribute assigning step in turn comprises:
 a reference setting step of defining a distance reference line on a plane containing the recording surface;   a distribution factor setting step of defining a distribution factor f(x) as a function of a distance x that takes on values in a range of 0≦f(x)≦1; and   an attribute determining step of determining a record attribute to be assigned to each unit region in a manner such that, to unit regions, positioned on or near a positioning line, which is parallel to and is at a position separated from the distance reference line by just a distance x, the first record attribute is assigned at a proportion of f(x) and the second record attribute is assigned at a proportion of “1−f(x)” or less.   
   
   
       6 . The hologram recording medium preparing method according to  claim 4 , wherein the attribute assigning step in turn comprises:
 a reference setting step of defining a distance reference point on a plane containing the recording surface;   a distribution factor setting step of defining a distribution factor f(x) as a function of a distance x that takes on values in a range of 0≦f(x)≦1; and   an attribute determining step of determining a record attribute to be assigned to each unit region in a manner such that, to unit regions, positioned on or near a positioning line, which is defined as a circumference of a circle of a radius x that is centered about the distance reference point, the first record attribute is assigned at a proportion of f(x) and the second record attribute is assigned at a proportion of “1−(x)” or less.   
   
   
       7 . The hologram recording medium preparing method according to  claim 4 , wherein the attribute assigning step in turn comprises:
 a reference setting step of defining an angle reference point and an angle reference line, passing through the angle reference point, on a plane containing the recording surface;   a distribution factor setting step of defining a distribution factor f(x) as a function of an angle x that takes on values in a range of 0≦f(x)≦1; and   an attribute determining step of determining a record attribute to be assigned to each unit region in a manner such that, to unit regions, positioned on or near a positioning line, which passes through the angle reference point and is inclined by just an angle x with respect to the angle reference line, the first record attribute is assigned at a proportion of f(x) and the second record attribute is assigned at a proportion of “1−f(x)” or less.   
   
   
       8 . The hologram recording medium preparing method according to  claim 5 , wherein in the distribution factor setting step, a monotonously increasing function or a monotonously decreasing function is used as the distribution factor f(x). 
   
   
       9 . The hologram recording medium preparing method according to  claim 5 , wherein in the attribute determining step, for a plurality N of unit regions positioned on a same positioning line, a process of using random numbers to assign the first record attribute to N×f(x) unit regions and assign the second record attribute to the remaining unit regions is performed. 
   
   
       10 . The hologram recording medium preparing method according to  claim 5 , wherein
 in the attribute determining step, an integer ratio a:β that approximates “f(x)”: “1−f(x)” is determined for each individual positioning line, and for (α+β) successive unit regions among a plurality of unit regions positioned on a single positioning line, the first record attribute is assigned to a unit regions and the second record attribute is assigned to β unit regions.   
   
   
       11 . The hologram recording medium preparing method according to  claim 4 , wherein the attribute assigning step in turn comprises:
 a reference setting step of defining a two-dimensional XY coordinate system on a plane containing the recording surface;   a distribution factor setting step of defining a distribution factor f(x, y) as a function of two variables x and y of the two-dimensional XY coordinate system that takes on values in a range of 0≦f(x, y)≦1; and   an attribute determining step of determining position coordinates (x, y) for the respective unit regions and determining record attributes to be assigned to the respective unit regions in a manner such that the first record attribute is assigned at a proportion of f(x, y) and the second record attribute is assigned at a proportion of “ 1−f(x, y)” or less.   
   
   
       12 . The hologram recording medium preparing method according to  claim 4 , wherein the attribute assigning step in turn comprises:
 a distribution factor setting step of preparing a table that defines a distribution factor f, taking on values in a range of 0≦f≦1, for each individual unit region;   and   an attribute determining step of determining record attributes to be assigned to the respective unit regions in a manner such that with each unit region, the first record attribute is assigned at a proportion of f defined by the table and the second record attribute is assigned at a proportion of “1−f” or less.   
   
   
       13 . The hologram recording medium preparing method according to  claim 1 , wherein in the unit region defining step, a plurality of unit regions, having a same size and same rectangular shape and arrayed in a form of a two-dimensional matrix, are defined. 
   
   
       14 . The hologram recording medium preparing method according to  claim 13 , wherein in the attribute determining step, a dithering process using a dither mask, comprising an array adapted to the matrix of unit regions, is performed to determine record attributes of the respective individual unit regions. 
   
   
       15 . The hologram recording medium preparing method according to  claim 13 , wherein in the attribute determining step, a process using an error diffusion method is performed to determine record attributes of the respective individual unit regions. 
   
   
       16 . The hologram recording medium preparing method according to  claim 4 , wherein in the original image preparing step, digital data, expressing a two-dimensional image or a three-dimensional image, are prepared as an original image. 
   
   
       17 . The hologram recording medium preparing method according to  claim 3 , wherein in the original image preparing step, an empty image without an actual entity is prepared as one of the original images and no pattern whatsoever is formed for unit regions that have been assigned a record attribute of the empty image. 
   
   
       18 . The hologram recording medium preparing method according to  claim 1 , wherein in determining an interference fringe pattern based on an original image for a unit region in the record pattern preparing step, an original image and the recording surface are positioned in a three-dimensional space, a predetermined reference light is defined, and the interference fringe pattern, formed in the unit region by an object light from the original image and the reference light, is determined by computation. 
   
   
       19 . The hologram recording medium preparing method according to  claim 1 , wherein in determining a diffraction grating pattern or a scattering structure pattern based on an original image for a unit region in the record pattern preparing step, one or a plurality of pixels are defined in the unit region, a corresponding pixel or pixels on the original image is or are determined for the defined pixel or pixels, and a diffraction grating pattern or a scattering structure pattern in each individual defined pixel is determined based on a pixel value of the corresponding pixel. 
   
   
       20 . The hologram recording medium preparing method according to  claim 4 , wherein in the record pattern preparing step, the first original image, the second original image, and the recording surface are positioned in a three-dimensional space, a predetermined reference light is defined, an interference fringe pattern of object light from the first original image and the reference light is determined by computation for each unit region, to which the first record attribute is assigned, and an interference fringe pattern of object light from the second original image and the reference light is determined by computation for each unit region, to which the second record attribute is assigned. 
   
   
       21 . The hologram recording medium preparing method according to  claim 4 , wherein in the record pattern preparing step, the first original image and the recording surface are positioned in a three-dimensional space, a predetermined reference light is defined, and an interference fringe pattern of object light from the first original image and the reference light is determined by computation for each unit region to which the first record attribute is assigned, and for each unit region to which the second record attribute is assigned, one or a plurality of pixels is or are defined in a unit region, a corresponding pixel or pixels on the second original image is or are determined for the defined pixel or pixels, and a diffraction grating pattern or a scattering structure pattern in each individual defined pixel is determined based on a pixel value of the corresponding pixel. 
   
   
       22 . The hologram recording medium preparing method according to  claim 4 , wherein in the record pattern preparing step, for each unit region to which the first record attribute is assigned, one or a plurality of pixels is or are defined in the unit region, a corresponding pixel or pixels on the first original image is or are determined for the defined pixel or pixels, and a diffraction grating pattern or a scattering structure pattern in each individual defined pixel is determined based on a pixel value of the corresponding pixel, and for each unit region to which the second record attribute is assigned, one or a plurality of pixels is or are defined in the unit region, a corresponding pixel or pixels on the second original image is or are determined for the defined pixel or pixels, and a diffraction grating pattern or a scattering structure pattern in each individual defined pixel is determined based on a pixel value of the corresponding pixel. 
   
   
       23 . The hologram recording medium preparing method according to  claim 1 , wherein a size of each unit region is set to a size, by which the presence of each individual unit region cannot be recognized by a naked eye. 
   
   
       24 . A computer program, having a function of making a computer execute the process of the attribute assigning step and the process of the record pattern preparing step of the preparing method according to  claim 1 ;
 on the basis of digital data, expressing an original image prepared in the original image preparing step of the preparing method according to  claim 1 , and digital data, expressing the unit regions defined in the unit region defining step of the preparing method according to  claim 1 .   
   
   
       25 . A hologram recording medium, prepared by the preparing method according to  claim 1 . 
   
   
       26 . A hologram recording medium preparing device comprising:
 an original image storage unit, storing, as data, a plurality M of original images to be recorded;   a unit region defining unit, defining and positioning a plurality of unit regions, each having an adequate area for recording interference fringes of visible light, on a hologram recording surface;   an attribute assigning unit, assigning a record attribute to each unit region according to appearance probabilities of respective record attributes at each individual position when a gradation pattern for each of the M original images, which expresses that an appearance probability of a record attribute corresponding to an original image changes gradually in space, is overlapped onto the recording surface; and   a record pattern preparing unit, determining, for each individual unit region, an interference fringe pattern, a diffraction grating pattern, or a scattering structure pattern based on a specific original image corresponding to an assigned record attribute to prepare data indicating a predetermined record pattern to be formed on the recording surface.   
   
   
       27 . A hologram recording medium, having a recording surface, on which a plurality of unit regions, each having an adequate area for recording interference fringes of visible light, are defined, and wherein image information concerning one original image, among a plurality M of original images, is recorded as an interference fringe pattern, a diffraction grating pattern, or a scattering structure pattern in each unit region, and appearance probabilities of unit regions, in which image information concerning the respective original images are recorded, change in space. 
   
   
       28 . A hologram recording medium, having a recording surface, on which a plurality of unit regions, each having an adequate area for recording interference fringes of visible light, are defined, and wherein either image information concerning a first original image or image information concerning a second original image is recorded as an interference fringe pattern, a diffraction grating pattern, or a scattering structure pattern in each unit region, and an appearance probability of unit regions, having a first record attribute and in which image information concerning the first original image is recorded, and an appearance probability of unit regions, having a second record attribute and in which image information concerning the second original image is recorded, gradually change in space.