JP5003721B2 - Hologram recording medium and manufacturing method thereof - Google Patents

Description

  The present invention relates to a hologram recording medium and a manufacturing method thereof, and more particularly to a hologram recording medium in which a completely different original image is observed by changing a viewpoint position and a manufacturing method thereof.

  Holograms have been widely used as anti-counterfeiting applications for vouchers and credit cards. Usually, an area for recording a hologram is provided on a part of a medium to be subjected to forgery prevention measures, and a stereoscopic image or the like is recorded in the form of a hologram in this area.

  At present, commercially available holograms are obtained by recording an original image as interference fringes on a medium by an optical method. That is, an object constituting an original image is prepared, and light from this object and reference light are guided onto a recording surface coated with a photosensitive agent using an optical system such as a lens, and interference fringes are formed on the recording surface. The method of forming is adopted. This optical method requires a highly accurate optical system in order to obtain a clear image, but is the most direct method for obtaining a hologram and is the most widely used method in the industry. is there.

  In addition, recently, a method of creating a hologram by forming interference fringes on a recording surface by a calculation using a computer is known, and a hologram created by such a method is generally called a “computer-generated hologram (CGH). : Computer Generated Hologram) ”, or simply“ Computer Hologram ”. This computer generated hologram can be obtained by simulating an optical interference fringe generation process on a computer, and the entire process of generating an interference fringe pattern is performed as an operation on the computer. When image data of an interference fringe pattern is obtained by such calculation, physical interference fringes are formed on an actual medium based on the image data. Specifically, for example, a method of forming physical interference fringes by applying image data of an interference fringe pattern created by a computer to an electron beam drawing apparatus and scanning the electron beam on a medium has been put into practical use. Yes.

  With the development of computer graphics technology, it is becoming common in the printing industry to handle various images on a computer. Therefore, it is convenient if the original image to be recorded on the hologram can be prepared as image data obtained using a computer. In order to meet such demands, a technique for creating a computer generated hologram has become an important technique, and it is expected that it will become a technique to replace an optical hologram creating method in the future. Various techniques relating to such computer generated holograms are disclosed in, for example, the following Patent Documents 1 to 10. Further, the following Patent Documents 11 to 13 disclose a technique for creating a pseudo hologram using a diffraction grating pattern.

JP-A-9-319290 JP-A-10-123919 Japanese Patent Laid-Open No. 11-24539 Japanese Patent Laid-Open No. 11-24540 JP 11-24541 A JP 11-202741 A JP 2000-214750 A JP 2000-214751 A JP 2001-013858 A JP 2001-013859 A JP-A-6-337622 JP-A-8-21909 JP-A-8-75912

  In the hologram recording medium, the original image can be recorded in three dimensions, and the original image can be observed from different angles by changing the viewpoint position. As described above, a feature of the hologram recording medium is that a stereoscopic image can be recorded on a plane. However, recently, a prototype of a hologram recording medium having a further feature has been made in which a completely different original image is reproduced when observed from different angles. As described above, a method of performing multiple exposure is known as a method for recording a plurality of original images on a single medium. For example, after exposing the interference fringes for the first object on the photosensitive surface and then exposing the interference fringes for the second object on the same photosensitive surface, the interference fringes for the two objects are superimposed and recorded. can do. However, in such a method using multiple exposure, a part of the information of the interference fringes recorded earlier is lost due to the influence of the interference fringes recorded later, and a clear reproduced image cannot be obtained. is there. This problem becomes more prominent as the number of multiple exposures increases.

  Accordingly, an object of the present invention is to provide a hologram recording medium and a method for manufacturing the same, which can clearly reproduce a completely different original image by changing the viewpoint position.

(1) According to a first aspect of the present invention, in a hologram recording medium, a plurality of recording areas are provided on a recording surface, and each recording area belongs to one of N groups (N ≧ 2), In the recording area belonging to the n th (1 ≦ n ≦ N) group, the interference between the object light from the nth original image of the N patterns and the nth reference light of the N patterns The fringes are recorded, and the incident directions of the N reference lights with respect to the recording surface at the time of recording are set to be different from each other so that different original images are reproduced when viewed from N viewpoint positions. configured,
In addition, a plurality of recording areas belonging to the same group are distributed over the entire recording surface, and belong to the distributed nth group when observed from the nth viewpoint position. The nth original image is observed by the light from the recording area.

(2) A second aspect of the present invention is the hologram recording medium according to the first aspect described above,
A plurality of recording areas belonging to the same group are regularly arranged on the recording surface at a constant cycle.

(3) A third aspect of the present invention is the hologram recording medium according to the first or second aspect described above,
On the recording surface defined on the XY plane, a large number of recording areas consisting of elongated rectangles in the X-axis direction are arranged in the Y-axis direction, and the recording areas adjacent in the Y-axis direction belong to different groups. Is.

(4) A fourth aspect of the present invention is the hologram recording medium according to the first to third aspects described above,
When the reference light incident on the recording surface defined on the XY plane is projected onto the YZ plane, the angle θyz formed by the projected image and the normal set up on the recording surface is substantially the same for all N reference lights. Thus, when projected onto the XZ plane, settings are made so that the angle θxz between the projected image and the normal line set up on the recording surface is sufficiently different as necessary for observation of different original images for all N reference lights. It is what I did.

(5) A fifth aspect of the present invention is the hologram recording medium according to the first to third aspects described above,
When the reference light incident on the recording surface defined on the XY plane is projected onto the YZ plane, the angle θyz formed by the projected image and the normal set up on the recording surface differs for all N reference lights. The setting is such that the angle θxz between the projected image and the normal line standing on the recording surface is substantially the same for all N reference lights when projected onto the XZ plane, sufficiently different to the extent necessary for observing the original image. It is what I do.

(6) The sixth aspect of the present invention is the hologram recording medium according to the first to third aspects described above,
The angle formed between the reference light incident on the recording surface defined on the XY plane and the normal line standing on the recording surface is substantially the same for all N reference lights, and this reference light is applied to the recording surface. In the case of projection, settings are made so that all the reference lights having N angles between the projected image and the X axis or the Y axis are sufficiently different as necessary for observation of different original images.

(7) A seventh aspect of the present invention is the hologram recording medium according to the first to sixth aspects described above,
When the interference fringes are recorded, the spread angle of the object light from the original image toward the recording surface is limited.

(8) The eighth aspect of the present invention is the hologram recording medium according to the first to seventh aspects described above,
Each of the N original images is composed of one frame of still image that constitutes a series of videos, and when the viewpoint position is changed in N ways with time, a video consisting of N frames can be observed. Is.

(9) A ninth aspect of the present invention is the hologram recording medium according to the eighth aspect described above,
A moving image is composed of still images of a plurality of frames including the same display object, and the display position of the display object in each frame is made different so that a moving image showing a state in which the display object moves can be observed. It is a thing.

(10) A tenth aspect of the present invention is the hologram recording medium according to any one of the first to ninth aspects ,
For the specific group, M (M ≧ 2) subgroups are further defined, and each of the recording areas belonging to the mth (1 ≦ m ≦ M) subgroup is colored with a single color. Among the original images composed by combining the original single-color partial original images, an interference pattern between the object light from the m-th single-color partial original image and the reference light having the same color as the object light is recorded, When the white reproduction illumination light is irradiated and observed from a predetermined viewpoint position, the original image is reproduced as a color image having M colors.

(11) An eleventh aspect of the present invention is the hologram recording medium according to the first to ninth aspects described above,
The recording area belonging to a specific group is divided into T divided areas (T ≧ 2), and the t th (1 ≦ t ≦ T) divided area is obtained from an original image having T color components. When interference fringes between the object light corresponding to the t-th color component and the reference light of the same color as the object light are recorded and observed from a predetermined viewpoint position by irradiating white reproduction illumination light In addition, the original image is reproduced as a color image having T colors.

(12) According to a twelfth aspect of the present invention, in the hologram recording medium, a plurality of recording areas are provided on the recording surface, and each recording area includes N interference fringe recording groups (N ≧ 1) and K diffraction gratings. In the recording area belonging to any of the recording groups (K ≧ 1) and belonging to the nth (1 ≦ n ≦ N) interference fringe recording group, the nth interference fringe recording of N patterns. Interference fringes between the object light from the original image and the nth reference light among the N patterns are recorded, and within the recording area belonging to the kth (1 ≦ k ≦ K) diffraction grating recording group Records the k-th original image for recording a diffraction grating as K diffraction patterns ,
In addition, a plurality of recording areas belonging to the same interference fringe recording group are distributed over the entire recording surface, and when observed from the nth viewpoint position, the nth interferences are distributed. The nth original image is observed by light from the recording area belonging to the fringe recording group.

(13) A thirteenth aspect of the present invention is the hologram recording medium according to the twelfth aspect ,
By adjusting the relationship between the incident direction of the reference beam on the recording surface when recording the interference fringes and the arrangement direction of the grating lines when recording the diffraction grating, the original image for recording the interference fringes and the diffraction grating recording are adjusted. The original image is configured to be reproduced when observed at different viewpoint positions.

(14) A fourteenth aspect of the present invention is the hologram recording medium according to the twelfth aspect ,
At the time of interference fringe recording, the incidence directions of the N kinds (N ≧ 2) of reference light with respect to the recording surface are set to be different from each other, and when viewed from N viewpoint positions, different interference fringe recording original images are obtained. It is designed to be played back.

(15) A fifteenth aspect of the present invention is the hologram recording medium according to the twelfth aspect ,
When K diffraction (K ≧ 2) diffraction grating recording original images are recorded by diffraction gratings having different radiation directions of the diffracted light, and observed from K viewpoint positions, different diffraction grating recording original images are obtained. It is designed to be played back.

(16) A sixteenth aspect of the present invention is the hologram recording medium according to the first to fifteenth aspects described above,
The interference fringes, or the interference fringes and the diffraction grating pattern, are configured by a fine uneven structure formed on the medium surface.

(17) The seventeenth aspect of the present invention provides the hologram recording medium according to the first to sixteenth aspects described above,
Covering the surface of the photosensitive plate constituting the recording surface with a light-shielding mask so that only the recording area belonging to the same group is exposed, and optically recording one original image in the exposed recording area It is intended to be executed repeatedly only.

(18) An eighteenth aspect of the present invention provides the hologram recording medium according to the first to sixteenth aspects described above,
For each recording area, considering the group to which it belongs, the image data corresponding to the interference fringes or diffraction grating pattern to be recorded is obtained by calculation using a computer, and the pattern is formed on the physical medium based on the obtained image data. Is drawn.

  According to the hologram recording medium of the present invention, it is possible to reproduce a completely different original image clearly by changing the viewpoint position.

It is a principle figure which shows the preparation method of a general hologram. 3 is a perspective view showing object light gathering at one point Q (x, y) on a recording surface 20. FIG. It is a figure which shows three types of original images recorded on the hologram recording medium which concerns on this invention. FIG. 4 is a plan view showing recording areas defined on a recording surface in order to record the three types of original images shown in FIG. 3. It is a perspective view which shows the operation | work which records the 1st original image Fa shown in FIG. It is a perspective view which shows the operation | work which records the 2nd original image Fb shown in FIG. It is a perspective view which shows the operation | work which records the 3rd original image Fc shown in FIG. It is a side view of the recording medium 20 shown in FIGS. FIG. 8 is a top view of the recording medium 20 shown in FIGS. It is a top view of the recording medium 20 shown in FIGS. It is a perspective view which shows that the information of 1 point P on the original image Fc is recorded on the whole recording area C1-C3. It is a perspective view which shows that the information of the point light source on the unit line segment L1-L3 defined on the original image Fc is recorded only in the corresponding recording area C1-C3, respectively. It is a perspective view which shows the recording method which restrict | limited the divergence angle of the Y-axis direction of the object light emitted from the point light source Pij to (xi). It is a perspective view showing a recording method in which the spread angle in the Y-axis direction of the object light emitted from the point light source Pij is limited to ξ and the spread angle in the X-axis direction is limited to Ψ. It is a top view which shows the state which defined several types of recording area from which an area differs on a recording surface. It is a top view which shows the state which defined several types of recording area from which an arrangement period differs on a recording surface. It is a top view which shows some examples which defined the unitary recording area on the recording surface. It is a figure which shows an example of the original image which comprises a series of moving images. It is a figure which shows an example of the original image which comprises the moving image to which a display target object moves. It is a figure which shows the example of a monochrome original image and a multicolor original image. FIG. 21 is a plan view showing a state where recording areas for recording the two original images shown in FIG. 20 are defined. It is a figure which shows the example of a monochrome original image and a color original image. It is a top view which shows the state which defined the recording area for recording two types of original images shown in FIG. It is a figure which shows the original image which shows character "A", and its pixel information. It is a top view of the pixel pattern which has a diffraction grating which should be allocated to 1 pixel of an original image. FIG. 26 is a plan view showing a state in which the pixel pattern shown in FIG. 25 is assigned to each pixel constituting the original image shown in FIG. 24. It is a top view which shows the coordinate value of each pixel of the original image shown in FIG. It is a top view which shows the diffraction grating pattern expressing two kinds of characters. It is a top view which shows the pattern obtained by superimposing the two types of diffraction grating patterns shown in FIG. It is a figure which shows four types of original images recorded on the hologram recording medium which concerns on this invention. It is a conceptual diagram which shows the state which recorded two types of original images by combining an interference fringe and a diffraction grating pattern. FIG. 31 is a plan view showing a state where recording areas for recording the four original images shown in FIG. 30 are defined. It is a top view which shows the 1st observation aspect of the recording medium which recorded four types of original images by combining an interference fringe and a diffraction grating pattern. It is a top view which shows the 2nd observation aspect of the recording medium which recorded four types of original images by combining an interference fringe and a diffraction grating pattern. FIG. 31 is a plan view showing a state where a recording area for recording two of the four original images shown in FIG. 30 is defined. FIG. 36 is a plan view showing a state where recording is actually performed in the recording area shown in FIG. 35. FIG. 31 is a plan view showing a state where recording areas for recording three of the four original images shown in FIG. 30 are defined. FIG. 38 is a plan view showing a state in which recording is actually performed in the recording area shown in FIG. 37. FIG. 31 is a plan view showing a state in which recording areas for recording all four original images shown in FIG. 30 are defined.

<<< §1. Basic principle of hologram >>>
FIG. 1 is a principle diagram showing a general hologram creation method, and shows a method of recording an original image 10 on a recording medium 20 as interference fringes. Here, for convenience of explanation, an XYZ three-dimensional coordinate system is defined as shown, and the recording medium 20 (for convenience of explanation, a medium having no thickness, ie, the recording surface itself) is placed on the XY plane. It shall be placed. When an optical method is employed, some object is prepared as the original image 10 and a photosensitive plate is prepared as the recording medium 20. Then, coherent light such as laser light is prepared, and a part of the coherent light is irradiated onto an object constituting the original image 10 and another part is irradiated onto a photosensitive plate constituting the recording medium 20. The light irradiated on the object travels toward the recording medium 20 as object light O, and the light directly irradiated on the recording medium 20 functions as the reference light R. On the recording medium 20, interference fringes between the object light O and the reference light R are recorded. Here, when an arbitrary point P on the original image 10 is considered, the object light O emitted from the arbitrary point P travels toward the entire surface of the recording medium 20 as illustrated, and the reference light R Are recorded on the recording medium 20 as interference fringes. Eventually, all points on the original image 10 are recorded as interference fringes on the recording medium 20 in the same manner.

  The above is the principle of creating a hologram recording medium by an optical method. In order to create a computer generated hologram at the position of the recording medium 20, the original image 10, the recording medium 20, and the reference light R are used as data on a computer. Each may be defined and the interference wave intensity at each position on the recording medium 20 may be calculated. Specifically, for example, as shown in FIG. 2, the original image 10 is handled as a set of I point light sources P1, P2, P3,..., Pi,. , O3,..., Oi,..., OI respectively travel to the calculation point Q (x, y) and the reference light R is irradiated toward the calculation point Q (x, y). A calculation for obtaining the amplitude intensity at the position of the calculation point Q (x, y) of the interference wave generated by the interference between the object light O1 to OI of the book and the reference light R may be performed. The object light and the reference light are usually calculated as monochromatic light. A large number of calculation points corresponding to the required resolution are defined on the recording medium 20, and the calculation of the amplitude intensity is performed for each of these calculation points. A distribution will be obtained.

  Thus, when the intensity value of the interference wave can be calculated for each calculation point defined on the recording medium 20, a pixel having a pixel value corresponding to the intensity value of the interference wave at each calculation point position. Is defined, an interference wave image composed of a set of these pixels can be created on the recording medium 20. This interference wave image is an image showing the intensity distribution of the interference wave obtained on the recording medium. Therefore, if a physical gray pattern or emboss pattern is formed on an actual medium based on this interference wave image, a hologram recording medium in which the original image 10 is recorded as interference fringes can be created. As a technique for forming high-resolution interference fringes on a medium, drawing using an electron beam drawing apparatus is suitable. An electron beam drawing apparatus is widely used for drawing a mask pattern of a semiconductor integrated circuit, and has a function of scanning an electron beam with high accuracy. Accordingly, if image data indicating the intensity distribution of the amplitude of the interference wave obtained by calculation is applied to the electron beam drawing apparatus and the electron beam is scanned, an interference fringe pattern corresponding to the amplitude intensity distribution can be drawn.

  However, a general electron beam drawing apparatus has only a function of drawing a binary image by controlling drawing / non-drawing. Therefore, the intensity distribution obtained by the calculation may be binarized to create a binary image, and this binary image data may be given to the electron beam drawing apparatus. That is, a predetermined threshold value (for example, an average value of all amplitude intensity values distributed on the recording medium 20) is set for the amplitude intensity value of the interference wave, and the calculation point has an intensity value equal to or greater than this threshold value. Is given a pixel value “1”, a pixel value “0” is given to a calculation point having an intensity value less than this threshold value, and each calculation point Q (x, y) is assigned “1” or “ If converted into a pixel having a pixel value of “0”, a binary image consisting of a set of these pixels is obtained. If the binary image data is supplied to the electron beam drawing apparatus and drawn, interference fringes can be drawn as a physical binary image. Actually, based on the physically drawn interference fringes, for example, an embossed plate (an embossed plate having a pixel portion having a pixel value “1” as a convex portion and a pixel portion having a pixel value “0” as a concave portion, Alternatively, by creating an embossed plate having a concave-convex relationship opposite to this and performing embossing using this embossed plate, a hologram having interference fringes formed as a concave-convex structure on the surface can be mass-produced.

  In order to reproduce a recording medium on which a hologram created by the method described above is recorded under ideal conditions, light having the same wavelength as the reference light R used for recording may be irradiated from the same direction. . That is, when the reproduction illumination light R is irradiated from the direction shown in FIG. 1 and observed from the back side of the recording medium 20, the original image 10 is observed as a stereoscopic reproduction image. Note that in the case of a hologram recording medium used for a forgery prevention mark for a credit card, the viewpoint is placed on the back side of the recording medium 20 shown in FIG. In this case, the original image 10 is obtained as a three-dimensional reproduction image. However, in a normal reproduction environment, it is difficult to prepare light having the same wavelength as that of the reference light R used for recording as reproduction illumination light, and in fact, reproduction illumination light close to white is used. There are many. When reproduction is performed using white illumination light, the obtained reproduced image is observed as cloudy. Therefore, a method for limiting the spread angle of the object light is known as one method for preventing the cloudiness of the reproduced image. Since this divergence angle limiting method is also useful for the hologram recording medium according to the present invention, the details will be described in Section 3.

<<< §2. Basic principle of the present invention >>
Next, the basic principle of the hologram recording medium according to the present invention will be described. An object of the present invention is to provide a hologram recording medium capable of clearly reproducing a completely different original image by changing the viewpoint position. Therefore, here, three completely different original images such as original images Fa, Fb, and Fc as shown in FIG. 3 are recorded on a single recording medium, and a specific original is changed by changing the viewpoint position. The principle of enabling the selective reproduction of images will be described.

  First, as shown in FIG. 4, a plurality of recording areas are defined on the recording surface of the recording medium 20. Here, it is assumed that the recording surface is on the XY plane, and each recording area is defined as an area consisting of a long and narrow rectangle in the X-axis direction. That is, in the example of FIG. 4, nine recording areas A1, B1, C1, A2, B2, C2, A3, B3, and C3 are defined, all of which are elongated in the X-axis direction and have a width h in the Y-axis direction. It is composed of the same rectangular area. In the present invention, a plurality of groups are defined according to the number of original images to be recorded, and each recording area belongs to one of the groups. In the embodiment shown here, as shown in FIG. 3, since three kinds of original images are recorded in an overlapping manner, three kinds of groups Ga, Gb, and Gc are defined, and each recording area is composed of these three kinds of groups. I belong to one of them. In the example of FIG. 4, the recording areas A1, A2, A3 belong to the group Ga, the recording areas B1, B2, B3 belong to the group Gb, and the recording areas C1, C2, C3 belong to the group Gc. Has been. Here, the group to which each recording area belongs is shown in parentheses.

  Thus, when each recording area is divided into groups, information relating to a specific original image is recorded in a recording area belonging to the specific group. For example, as shown in FIG. 3, when three original images Fa, Fb, and Fc are recorded, the original image Fa is recorded in recording areas A1, A2, and A3 belonging to the group Ga, and the original image Fb is recorded. Are recorded in the recording areas B1, B2, B3 belonging to the group Gb, and the original image Fc is recorded in the recording areas C1, C2, C3 belonging to the group Gc. Here, the important point is that the recording is performed by setting the incidence direction of the reference light to the recording surface of the recording medium 20 to be different for each group. This recording method will be specifically described with reference to FIGS.

  First, as shown in FIG. 5, the first original image Fa is recorded in the recording areas A1, A2, A3 belonging to the group Ga. At this time, the recording surface is irradiated with the reference light Ra from the first direction, and interference fringes between the object light Oa and the reference light Ra from the original image Fa are recorded in the recording areas A1, A2, and A3. To be. The hatched area in the figure is the area where the recording of interference fringes has been completed. At this time, nothing is recorded in the recording areas B1, B2, B3, C1, C2, and C3. Subsequently, as shown in FIG. 6, the second original image Fb is recorded in the recording areas B1, B2, and B3 belonging to the group Gb. At this time, the recording surface is irradiated with the reference light Rb from the second direction, and interference fringes between the object light Ob and the reference light Rb from the original image Fb are recorded in the recording regions B1, B2, and B3. To be. Finally, as shown in FIG. 7, the third original image Fc is recorded in the recording areas C1, C2, and C3 belonging to the group Gc. At this time, the recording light is irradiated with the reference light Rc from the third direction, and interference fringes between the object light Oc and the reference light Rc from the original image Fc are recorded in the recording areas C1, C2, and C3. To be. Thus, interference fringes are recorded on the entire recording surface of the recording medium 20.

  The important point here is that the reference beams Ra, Rb, and Rc are irradiated from different incident directions on the recording surface. In this way, if each original image is recorded while changing the incident direction of the reference light, the viewpoint position where each original image is observed when the reproduction illumination light is irradiated from a predetermined direction on the recording surface. Will be different. This phenomenon is that “a three-dimensional reproduction image is obtained when irradiation light for reproduction having the same wavelength as the reference light is irradiated from the same direction as the reference light used for recording (or a direction that is plane-symmetric with respect to the recording surface). Is a phenomenon based on the basic principle of holograms. That is, the observation mode of “changing the incident direction of the reproduction illumination light while fixing the viewpoint position” and the observation mode of “changing the viewpoint position while fixing the incident direction of the reproduction illumination light” are the principle of the hologram. Therefore, different original images Fa, Fb, and Fc are observed regardless of which observation mode is used.

  For example, the viewpoint is placed on the front surface (the side opposite to the side where the original image is placed) of the recording medium 20 on which the three original images Fa, Fb, and Fc are recorded by the above-described method, and the reference light Ra shown in FIG. If the reproduction illumination light is irradiated from the same direction (or a direction that is plane-symmetric with respect to the reference light Ra) with respect to the recording medium 20, the original image Fa is observed from the front viewpoint position. Further, if the reproduction illumination light is irradiated from the same direction as the reference light Rb shown in FIG. 6 (or a direction that is plane-symmetric with respect to the reference light Rb with respect to the recording medium 20), the original image is viewed from the front viewpoint position. If Fb is observed and the reproduction illumination light is irradiated from the same direction as the reference light Rc shown in FIG. 7 (or the direction that is symmetrical with respect to the reference light Rc with respect to the recording medium 20), the front surface The original image Fc is observed from the viewpoint position. Conversely, when the irradiation direction of the reproduction illumination light is fixed and the viewpoint position is moved, the same phenomenon occurs, and the original image Fa is observed from a certain viewpoint position, and the original image Fb is observed from another viewpoint position. Is observed, and the original image Fc is observed from another viewpoint position.

  In the above-described embodiment, three kinds of original images are recorded. However, in general, the present invention can be used when a plurality of N kinds of original images are recorded. That is, the hologram recording medium according to the present invention is provided with a plurality of recording areas on the recording surface of each medium, and each recording area belongs to one of N groups (N ≧ 2), and the nth In the recording area belonging to the group (1 ≦ n ≦ N), interference fringes between the object light from the nth original image of the N patterns and the nth reference light of the N patterns Is recorded, and it is only necessary that the incident directions of the N kinds of reference light with respect to the recording surface at the time of recording are set to be different from each other. In such a hologram recording medium, different original images are reproduced when viewed from N viewpoint positions.

  Incidentally, in the above-described embodiment, a plurality of recording areas belonging to the same group are distributed over the entire recording surface. More specifically, a plurality of recording areas belonging to the same group are regularly arranged on the recording surface at a constant period. For example, in FIG. 4, three recording areas A1, A2, and A3 belonging to the group Ga are distributed over the entire recording surface of the recording medium 20, and are regularly arranged with a constant period 3h. The same applies to the recording areas belonging to the groups Gb and Gc. When recording a plurality of original images in the same space, it is preferable to disperse and arrange the recording areas belonging to the same group in this way because a higher quality reproduced image can be obtained. Also, in practice, if the recording areas belonging to the same group are regularly arranged at a fixed period, the position of each recording area can be specified with a simple calculation formula. The working efficiency can be improved.

  The shape of each recording area is not necessarily a rectangular shape as in the above-described embodiment, but it is preferable to use a rectangular recording area in order to arrange each recording area regularly. In particular, as in the above-described embodiment, on the recording surface defined on the XY plane, a large number of recording areas consisting of elongated rectangles in the X-axis direction are arranged in the Y-axis direction, and each recording area adjacent in the Y-axis direction is arranged. Are configured to belong to different groups, the recording areas belonging to the same group can be easily distributed. At this time, if the width h in the Y-axis direction of each recording area is too large, a stripe pattern with horizontal stripes may be observed on the entire recording surface, so that the width cannot be visually observed (generally 0.1 mm or less). It is preferable to set. In the embodiment shown in FIGS. 4 to 7, the number of recording areas is set very small for convenience of explanation (the number of recording areas belonging to each group is only three). Actually, a large number of rectangular regions having a very small width h in the Y-axis direction are arranged so that a stripe pattern is not observed.

  Now, in creating the hologram recording medium according to the present invention, as described above, it is necessary to change the incident direction of the reference light during recording for each original image. Here, several embodiments for changing the incident direction will be described. First, in order to explain these embodiments, the following definitions are made. FIG. 8 is a side view of the recording medium 20 as viewed from the side. In the drawing, the right direction is the Z-axis direction, the downward direction is the Y-axis direction, and the direction perpendicular to the paper surface is the X-axis direction. In FIG. 8, the projection image of the reference light R incident on the position of the point Q on the recording medium 20 onto the YZ plane is Ryz, and the normal line standing on the recording surface of the recording medium 20 at the point Q is N. An angle formed between the normal N and the projection image Ryz is defined as θyz. On the other hand, FIG. 9 is a top view of the recording medium 20 as viewed from above, in which the left direction is the X-axis direction, the downward direction is the Z-axis direction, and the direction perpendicular to the paper surface is the Y-axis direction. In FIG. 9, the projected image of the reference light R incident on the position of the point Q on the recording medium 20 onto the XZ plane is Rxz, and the normal line standing on the recording surface of the recording medium 20 at the point Q is N. The angle between the normal N and the projected image Rxz is θxz. 10 is a plan view of the recording medium 20. The right direction in the figure is the X-axis direction, the downward direction is the Y-axis direction, and the direction perpendicular to the paper surface is the Z-axis direction. In FIG. 10, the projected image of the reference light R incident on the point Q on the recording medium 20 onto the XY plane is Rxy, and the angle formed by the projected image Rxy and the X axis is θxy (Y axis and It is equivalent even if the angle formed by is used).

  Now, in order to record N original images, it is necessary to set N reference lights having different incident directions with respect to the recording surface. In this case, in the first embodiment in which N types of reference lights are set, the angle θyz defined in FIG. 8 is substantially the same for all the N types of reference lights, and the angle θxz defined in FIG. The settings are such that all N reference lights are sufficiently different from each other to the extent necessary for observing different original images (here, “substantially the same” means that the same original image can be observed). That means.) In other words, this setting can be said to be a setting for moving the reference light so as to swing in the horizontal direction. A recording medium recorded with such a setting can observe a specific original image at a specific viewpoint position by moving the viewpoint position in the horizontal direction during reproduction (or tilting the recording medium itself in the horizontal direction). In other words, switching of the original image is performed by moving the viewpoint in the horizontal direction.

  However, if the difference between the angles θxz is too small, a plurality of original images will be observed at the same viewpoint position at the same time. Therefore, the angles θxz differ to some extent, that is, each original image is observed from different viewpoint positions. It is necessary to set with a difference that is possible. For example, if the difference between the angle θxz of the first reference light R1 and the angle θxz of the second reference light R2 is only about 1 °, the first recorded using the first reference light R1 There is a high possibility that the original image and the second original image recorded using the second reference light R2 are observed at the same viewpoint position. How much the difference of the angle θxz is set to allow a plurality of original images to be observed from different viewpoint positions depends on the size of the recording surface, the size of each original image, and the recording surface of each original image Since it differs depending on parameters such as the position of the image, it cannot be determined unconditionally, but in the case of a general example, if there is a difference of about 60 °, it is possible to observe each original image from different viewpoint positions. It seems to become. For reference, an example of the incident angles of the three reference beams Ra, Rb, Rc used for actually recording the three original images Fa, Fb, Fc shown in FIG. The angle θyz is the same as 18.75 ° for any reference light, and the angle θxz is 62.97 ° for the reference light Ra, 0 ° for the reference light Rb, and −62.97 ° for the reference light Rc. As a result, the original images Fa, Fb, and Fc could be observed from completely different viewpoint positions.

  In the second embodiment in which N kinds of reference lights are set, the setting is made by switching the vertical and horizontal directions of the first embodiment described above. That is, the angle θyz defined in FIG. 8 is sufficiently different for all the N types of reference lights to be necessary for the observation of different original images, and the angle θxz defined in FIG. The settings are almost the same for all. In other words, this setting can be said to be a setting for moving the reference light so as to swing in the vertical direction. A recording medium recorded with such a setting can observe a specific original image at a specific viewpoint position by moving the viewpoint position in the vertical direction during reproduction (or tilting the recording medium itself in the vertical direction). In other words, the original image is switched by moving the viewpoint in the vertical direction. Also in this case, each original image cannot be observed separately unless the difference in angle θyz is set to a certain level.

  The third embodiment for setting N types of reference light is a setting that combines the first embodiment and the second embodiment described above, and the reference light is applied to a point Q on the recording surface. When incident, the angle formed with the normal set at the position of the point Q on the recording surface is substantially the same for all N reference lights, and when this reference light is projected onto the recording surface, For all the reference beams having N angles with the X-axis or the Y-axis, settings are made so as to be sufficiently different as necessary for observation of different original images. In this setting, when a normal is set on a point Q shown in FIG. 10 and a cone having the normal as a central axis and a point Q as an apex is considered, the direction of one edge of the cone is set as one reference beam. It can be said that the reference light is moved like a rotation axis of a topping during precession. When a recording medium recorded with such a setting moves the viewpoint position along the circumference of the bottom surface of the cone described above during reproduction (or when the recording medium itself moves like a precession of the top) ), A specific original image can be observed at a specific viewpoint position. In this case as well, each original image cannot be observed separately unless the difference in angle θxy is set to a certain level.

  Although the basic principle of the hologram recording medium according to the present invention has been described above, such a hologram recording medium can be manufactured by an optical technique, or a computer generated hologram technique using a computer. It is also possible to manufacture. If manufactured by an optical method, the surface of the photosensitive plate constituting the recording surface is covered with a light-shielding mask so that only the recording area belonging to the same group is exposed, and one original image is formed in the exposed recording area. The optical recording process may be repeatedly executed for the number of groups. For example, as shown in FIG. 5, when the first original image Fa is recorded, a recording that constitutes the photosensitive plate using a light shielding mask that exposes only the recording areas A1 to A3 belonging to the group Ga. It is only necessary to cover the medium 20 and record the interference fringes between the object light Oa from the object forming the original image Fa and the reference light Ra only in the exposed recording areas A1 to A3. Similarly, when performing the process shown in FIG. 6, a light-shielding mask that exposes only the recording areas B1 to B3 belonging to the group Gb is used, and when performing the process shown in FIG. 7, it belongs to the group Gc. A light shielding mask that exposes only the recording areas C1 to C3 to be used may be used.

  However, the above-described manufacturing method using the optical technique requires a considerable amount of labor for the mask alignment process and the like. For this reason, the hologram recording medium according to the present invention is preferably produced using a computer generated hologram method. If the computer generated hologram method is used, image data corresponding to the interference fringes to be recorded can be obtained by calculation using a computer in consideration of the group to which each recording area belongs. For example, as shown in FIG. 5, when the first original image Fa is recorded, only the recording areas A1 to A3 belonging to the group Ga are subject to calculation, and the interference wave is applied only to the calculation points in these areas. What is necessary is just to obtain | require the intensity value. Once the interference wave intensity values have been obtained for the entire recording surface, this is given as binary image data to an electron beam drawing apparatus or the like, and if a concavo-convex structure is formed on the surface of the physical medium, a hologram recording medium can be created Can do.

<<< §3. Limiting the divergence angle of object light >>>
As shown in FIG. 1, the basic principle of the hologram is to record the interference fringes between the object light O and the reference light R from an arbitrary point P on the original image 10 on the entire surface of the recording medium 20, Information on one point P is recorded on the entire recording surface. In other words, the object light O from one point P spreads over the entire recording surface. Such a concept is basically the same even in the case of the hologram recording medium according to the present invention. Therefore, for example, as shown in FIG. 11, when the information of the original image Fc is recorded in the recording areas C1 to C3 belonging to the group Gc, information on an arbitrary point P on the original image Fc is recorded. It is recorded in all the areas C1 to C3. As described above, the feature of the hologram is that the information of an arbitrary point on the original image is recorded over the entire recording surface, and a three-dimensional reproduction image is obtained by this feature.

  However, the basic principle of the hologram described above is based on the premise that reproduction is performed using monochromatic light having the same wavelength as that of the monochromatic light originally used for recording. When reproduction is performed using white light, The original three-dimensional reproduction image cannot be obtained. However, in reality, in the case of a hologram recording medium used for a forgery prevention seal for a credit card or the like, reproduction using white light is generally performed. When white illumination light is used during reproduction, reproduction light having various wavelengths is emitted from various parts of the recording medium in various directions (the emission direction of the reproduction light depends on the wavelength) A cloudy and unclear reproduction image will be observed. Thus, as a device for obtaining a clear reproduction image even when reproduction is performed using white illumination light, a technique for limiting the divergence angle of object light during recording has been proposed in the above-mentioned several publications. . Since this method is difficult to apply to a process of optically creating a hologram, it is practically a method based on a computer generated hologram.

  For example, as shown in FIG. 12, unit line segments L1 to L3 are defined on the original image Fc. Here, three cut planes parallel to the XZ plane are defined, and three unit line segments L1 to L3 are defined as line segments (curve segments) that appear at the cut end when the original image Fc is cut by the cut planes. Defined. The interval between the three cut surfaces is set equal to the arrangement interval (3h) of the recording areas C1, C2, C3 belonging to the group Gc. In the illustrated example, since the original image Fc is a soccer ball having a sphere, each of the unit line segments L1 to L3 is defined as a circle on the sphere. Subsequently, a large number of point light sources are defined at predetermined intervals on each of the unit line segments L1 to L3. In the illustrated example, point light sources P11, P12, P13,... Are defined on the unit line segment L1, and point light sources P21, P22, P23,. Point light sources P31, P32, P33,... Are defined on L3.

  Thus, when a number of point light sources are defined, interference fringes are recorded using these point light sources as sample light sources representing the original image Fc. That is, interference fringes between the object light emitted from each point light source and the predetermined reference light are recorded in the recording areas C1, C2, and C3. However, only the interference fringes based on the object light from the point light sources P11, P12, P13,... On the unit line segment L1 are recorded in the recording area C1, and the point light source on the unit line segment L2 is recorded in the recording area C2. Only interference fringes based on object light from P21, P22, P23,... Are recorded, and only interference fringes based on object light from point light sources P31, P32, P33,. To record. From another viewpoint, such a recording method can be said to be a recording method in which the spread angle of the object light emitted from the point light source is limited. That is, considering a general model as shown in FIG. 13, information on the j-th point light source Pij arranged on the i-th unit line segment Li defined on the original image is recorded on the recording medium 20. Recording only in the rectangular recording area Ci (shown by hatching in the figure) having a width h in the Y-axis direction defined above means that the object light emitted from the point light source Pij is in the Y-axis direction. This is equivalent to recording interference fringes generated by the object beam and the reference beam R (in the example shown, a plane wave traveling in a direction parallel to the YZ plane).

  Thus, when recording is performed with the divergence angle of the object light in the Y-axis direction limited to a predetermined angle ξ, as in the illustrated example, the same direction as the reference light R traveling in the direction parallel to the YZ plane (or recording In the case of observation by irradiating with white illumination light from a plane that is symmetrical with respect to the surface), the reproduction light having information on the point light source Pij is the light having any wavelength component. Since it only advances in the direction according to ξ, it is possible to suppress the phenomenon that a cloudy and unclear reproduction image is observed.

  The example shown in FIG. 14 is an example in which the spread angle of the object light in the X-axis direction is further limited to a predetermined angle Ψ. In this case, the object light emitted from the point light source Pij reaches only the area S (shown by hatching in the drawing) on the recording medium 20, and the information on the point light source Pij is stored in the area S. Will be recorded only. This method has an advantage that unevenness in luminance of a reproduced image can be suppressed.

  However, the method of limiting the divergence angle of object light can be said to be a method that goes against the original concept of hologram. As described in §1, in the original hologram, information on an arbitrary point P on the original image is recorded as interference fringes on the entire recording surface, thereby enabling stereoscopic viewing of the original image. It becomes. Therefore, the original stereoscopic vision of the reproduced image does not occur in the hologram recorded by limiting the spread angle of the object light. For example, in the example shown in FIG. 12, only the information about the point light source on the unit line segment L1 is recorded in the recording area C1, and the information about the point light source on the unit line segment L2 is recorded in the recording area C2. Only the information about the point light source on the unit line segment L3 is recorded in the recording area C3. Therefore, even if the hologram recorded on the recording medium 20 is reproduced, stereoscopic viewing in the vertical direction does not occur. Furthermore, in the example shown in FIG. 14, the stereoscopic viewing in the horizontal direction is also limited (when the spread angle Ψ in the X-axis direction becomes a certain degree or less, the stereoscopic viewing in the horizontal direction is not generated at all).

  In this way, the method of recording interference fringes by limiting the spread angle of the object light prevents the cloudiness of the reproduced image at the time of reproduction with white illumination light, and has the advantage of making the reproduced image clearer. Since there is a demerit that impairs the function of reproducing a stereoscopic image, which is the original characteristic of the hologram, it is preferable to use it properly depending on the application. For example, if it is an application such as an anti-counterfeit mark for a credit card, even if the stereoscopic view in the vertical direction is lost, it can function sufficiently if a certain degree of stereoscopic view in the horizontal direction is secured. As shown in FIG. 13, when recording is performed by limiting only the spread angle in the Y-axis direction, it is possible to realize a hologram recording medium capable of obtaining a practically sufficiently clear reproduced image.

<<< §4. Various variations >>
So far, the basic principle of the hologram recording medium according to the present invention has been described. Here, various modifications of the hologram recording medium will be described.

<< 4.1 Modifications Regarding Recording Area Arrangement >>>>
In the embodiment shown in FIG. 4, a recording area consisting of a rectangle of the same size having a width h in the Y-axis direction is defined. However, the size of each recording area can be changed for each group. It is. For example, in the example shown in FIG. 15, the recording areas A1 to A3 belonging to the group Ga and the recording areas C1 to C3 belonging to the group Gc are all from rectangles having the same size with a width h in the Y-axis direction. The recording regions B1 to B3 belonging to the group Gb are rectangular recording regions having a width 2h in the Y-axis direction. Eventually, the total area of the recording area belonging to the group Gb is twice as large as the entire area of the recording area belonging to the group Ga or the entire area of the recording area belonging to the group Gc. The area of the recording area is a factor that affects the brightness of the reproduced image. That is, when the three original images Fa, Fb, and Fc shown in FIG. 3 are recorded on the recording surface in which each recording area is defined as shown in FIG. 15, the original image Fb recorded in the group Gb is recorded. The brightness of the reproduced image is twice the brightness of the reproduced image of the original image Fa recorded in the group Ga or the brightness of the reproduced image of the original image Fc recorded in the group Gc. In the example shown in FIG. 3, the original images Fa and Fc are images composed of general pictures, whereas the original image Fb is an image composed of characters “PAT”. Thus, there is a request that an original image made up of characters is included in a plurality of N original images to be recorded, and that the original image made up of these characters is reproduced more remarkably at the time of playback. In the case where there is an image, it is effective to set so that the area of the recording area for the original image Fb made up of characters increases as in the example shown in FIG.

  In addition, with respect to an original image made up of characters, there is a considerable demand for “to obtain a reconstructed image with higher resolution” rather than “a desire to make a reconstructed image brighter”. In order to meet such a demand, the spatial arrangement cycle of the recording area for recording the original image composed of characters may be set shorter than the spatial arrangement period of the recording area for recording other original images. Such an embodiment is shown in FIG. In this example, if the width in the Y-axis direction of the recording areas B1-1, B1-2, B2-1, B2-2, B3-1, B3-2 belonging to the group Gb is h, it belongs to the group Ga. The widths of the recording areas C1 to C3 belonging to the recording areas A1 to A3 and the group Gc in the Y-axis direction are 2h, which is set to double. However, while the spatial arrangement period of the recording areas belonging to the group Gb is 3h, the spatial arrangement period of the recording areas belonging to the group Ga and the spatial arrangement period of the recording areas belonging to the group Gc. Is doubled with 6h. When the three original images Fa, Fb, and Fc shown in FIG. 3 are recorded on the recording surface in which such a recording area is defined, the resolution of the reproduced image of the original image Fb recorded in the group Gb is as follows. The resolution of the reproduced image of the original image Fa recorded in the group Ga or the resolution of the reproduced image of the original image Fc recorded in the group Gc is doubled (because the total recording area is equal for each original image). , The brightness will be the same.) Eventually, when it is desired to obtain a higher-resolution reproduced image of the original image composed of characters, the spatial arrangement period of the recording region for recording the original image composed of characters is set to the space of the recording region for recording another original image. What is necessary is just to set shorter than a typical arrangement period.

  When each recording area is configured by a rectangular figure elongated in the X-axis direction, as described above, unless the width in the Y-axis direction of each recording area is set so as not to be visually observable, a horizontal stripe pattern is formed. It will be recognized and will lead to undesirable results. When the inventor of the present application actually implemented the modification shown in FIG. 15 or FIG. 16, when h = 26 μm and 2h = 52 μm were set, a preferable result in which the stripe pattern was not recognized was obtained. Of course, this dimension setting is just an example, and any dimension setting may be used as long as the stripe pattern is not recognized. In addition, if a special design effect is aimed by intentionally recognizing a stripe pattern, the width in the Y-axis direction of each recording area may be set to a size that allows visual observation.

<<< 4.2 Modification Example in which Recording Areas are not Dispersed >>>
In the embodiments described so far, a plurality of recording areas belonging to the same group are distributed over the entire recording surface. However, in creating the hologram recording medium according to the present invention, it is not always necessary to distribute a plurality of recording areas belonging to the same group. FIG. 17 shows several examples in which one group is configured by only a single recording area. In any example, only three recording areas A, B, and C are defined, and each of these recording areas is a recording area belonging to the groups Ga, Gb, and Gc. Therefore, for example, when three types of original images Fa, Fb, Fc as shown in FIG. 3 are recorded on a recording surface in which a recording area as shown in FIG. The information is recorded only in the recording area A, the information of the original image Fb is recorded only in the recording area B, and the information of the original image Fc is recorded only in the recording area C.

  However, such a recording method is inappropriate when the three types of original images Fa, Fb, and Fc occupy almost the same spatial position. For example, when the vertical dimensions of three types of original images Fa, Fb, and Fc are substantially equal to the vertical dimension of the recording medium, in other words, each original image is reproduced almost completely within the screen of the recording medium. In this case, the original images are reproduced at positions that are spatially overlapped with each other. However, if a recording area as shown in FIG. 17A is defined, the information of the original image Fa is recorded only in the recording area A located at the upper part on the recording medium. Even if the information above the image Fa can be properly recorded, the information below the original image Fa cannot be properly recorded. For this reason, at the time of reproduction, there is a possibility that the lower part of the original image Fa becomes unclear or missing. In particular, when the method for limiting the divergence angle of the object light described in §3 is used, information on the lower part of the original image Fa is not recorded at all.

  Therefore, when a recording area as shown in FIG. 17 (a) is defined, the arrangement of the original image needs to correspond to the arrangement of each recording area. Specifically, for example, the vertical dimension of each of the three types of original images Fa, Fb, Fc shown in FIG. 3 is set to about 1/3 of the vertical dimension of the recording medium, and the original images Fa, Fb are sequentially arranged from the top. If they are arranged in the order of Fc and Fc, even if a recording area as shown in FIG. 17A is set, three types of original images can be appropriately recorded.

  For the same reason, when the recording areas A, B, and C are arranged as shown in FIG. 17 (b), the original image Fa is arranged at the center, and the original image Fb is arranged so as to surround it. It is necessary to arrange the original image Fc so as to surround the image, and the pattern of each original image needs to be a pattern suitable for such arrangement. The same applies to the example shown in FIG.

<<< 4.3 Modified Example with Animation Effect >>>
Since the N original images to be recorded in the present invention may be any original image, each of the N original images is represented by one frame of still images constituting a series of moving images. If configured, it is possible to create a hologram recording medium in which a moving image composed of N frames can be observed when the viewpoint position is changed in N ways with time. For example, three original images Fa, Fb, and Fc as shown in FIG. 18 are still images for one frame constituting a series of moving images in which balloons break, and these three original images are represented by the present invention. If the recording method is used, the original image Fa is observed from the first viewpoint position, the original image Fb is observed from the second viewpoint position, and the original image Fc is observed from the third viewpoint position. It will be. Therefore, when the viewpoint position is changed with time so as to reach the third viewpoint position from the first viewpoint position through the second viewpoint position, a series of moving images in which a balloon breaks can be observed.

  In addition, when a moving image is composed of still images of a plurality of frames including the same display object, and the display position of the display object in each frame is changed, this moving image shows a state in which the display object moves. It is also possible to create a hologram recording medium that can be observed. For example, three kinds of original images Fa, Fb, and Fc as shown in FIG. 19 all include the same display object called an automobile. However, the display position of the car is different for each original image. If such three kinds of original images are recorded by the method according to the present invention, as in the above-described modified example, from the first viewpoint position to the third viewpoint position via the second viewpoint position, If you change the viewpoint position with time, you can observe a series of videos that the car moves.

<<< 4.4 Modified Example of Recording Multicolor Original Image >>
When creating a general hologram, light having a specific single wavelength is used as object light and reference light used during recording. As described above, if the illumination light having the same single wavelength as that during recording is used during reproduction, a correct reproduction image having the color of this single wavelength can be obtained. However, reproduction using white illumination light is possible. When this is done, a phenomenon occurs in which reproduced light of various color components is mixed and the reproduced image becomes cloudy. However, as described in §3, if the method of limiting the spread angle of the object light is adopted, this clouding phenomenon can be suppressed, and a reproduced image close to a certain color can be obtained.

  Therefore, here, an example of recording a multicolor original image will be described. In addition, since various embodiments are disclosed in Japanese Patent Application Laid-Open No. 2001-1000062, the method described below is referred to for details. First, here, two kinds of original images Fa and Fb as shown in FIG. 20 are prepared. Here, the original image Fa is a monochrome original image, but the original image Fb is a two-color original image composed of two colors. More specifically, the original image Fb is composed of a combination of the upper half single-color partial original image Fbα and the lower half single-color partial original image Fbβ. The single-color partial original image Fbα is red and is a single-color partial original image. It is assumed that Fbβ is colored blue.

  When such two original images Fa and Fb are recorded, the recording area belonging to the group Ga and the recording area belonging to the group Gb are defined on the recording surface. Are further divided into two subgroups, subgroups Gbα and Gbβ, and a recording area belonging to subgroup Gbα and a recording area belonging to subgroup Gbβ are defined. FIG. 21 is a diagram showing an example in which each recording area is defined based on such group settings. In this example, four recording areas A1, A2, A3, A4 are defined as recording areas belonging to the group Ga, and four recording areas Bα1, Bα2, Bβ1, Bβ2 are also defined as recording areas belonging to the group Gb. Each of these recording areas is a rectangular area having a width h in the Y-axis direction. However, among the recording areas belonging to the group Gb, the two recording areas Bα1 and Bα2 arranged above belong to the subgroup Gbα, and the two recording areas Bβ1 and Bβ2 arranged below belong to the subgroup Gbβ. To do.

  After defining each recording area in this way, the original image Fa is recorded in the recording areas A1 to A4 belonging to the group Ga, and the original image is recorded in the recording areas Bα1, Bα2, Bβ1, and Bβ belonging to the group Gb. From the viewpoint of recording Fb, it is the same as the embodiment described so far. However, subgroups are further defined in the group Gb, the monochrome partial original images Fbα are recorded in the recording areas Bα1 and Bα2 belonging to the subgroup Gbα, and the recording areas Bβ1 and Bβ2 belonging to the subgroup Gbβ are recorded. Is characterized by the fact that the monochrome partial original image Fbβ is recorded. Here, the recording areas Bα1 and Bα2 for recording the monochrome partial original image Fbα constituting the upper half of the two-color original image Fb are arranged in the upper half position of the recording surface, and the monochrome constituting the lower half The recording areas Bβ1 and Bβ2 for recording the partial original image Fbβ are arranged at the lower half position of the recording surface. In this way, if there is a spatial consistency between the arrangement of the individual monochrome partial original images and the arrangement of the recording area for recording the individual monochrome partial original images, each monochrome is caused by the spatial arrangement condition. A situation in which the partial image is not properly recorded does not occur.

  The important point here is that the wavelength of the object light and the reference light used when recording the original image Fa may be any wavelength, but the wavelength of the object light and the reference light used when recording the monochromatic partial original image Fbα. The wavelength corresponding to red is used, and the wavelengths of the object light and reference light used when recording the monochrome partial original image Fbβ are set to wavelengths corresponding to blue. As described above, when the wavelength used for recording the original image Fb is changed for each single-color partial original image, the two single-color partial original images are observed at the same viewpoint position during reproduction. It will be observed in color. That is, in the illustrated example, the monochrome partial original image Fbα is observed as a red reproduced image, and the monochrome partial original image Fbβ is observed as a blue reproduced image. Here, the example of recording the two-color original image Fb composed of the two single-color partial original images Fbα and Fbβ has been described, but the three-color original image composed of the three single-color partial original images can also be recorded. However, it is also possible to record a multicolor original image composed of more colors.

  In general, N groups are defined for N original images to be observed at different viewpoint positions, and there are further M groups (M (M ≧ 2) subgroups are defined, and M monochromatic partial original images colored with a single color are combined in the recording area belonging to the mth (1 ≦ m ≦ M) subgroup. If the interference fringes between the object light from the mth monochrome original image and the reference light of the same color as the object light are recorded, the white reproduction illumination light is When the image is irradiated and observed from a predetermined viewpoint position, a multicolor image having M colors is reproduced. However, in reality, when reproduction is performed using white illumination light, a phenomenon occurs in which the reproduction image of various color components is mixed and the reproduction image becomes clouded. Therefore, each monochrome partial original image has the color as intended. It is not always played back. However, if the method of limiting the divergence angle of the object light described in §3 is adopted, it is possible to obtain color reproducibility close to the state intended at the time of recording.

  In the above-described embodiment, as shown in FIG. 20, the hologram recording medium capable of switching and reproducing the monochrome original image Fa and the two-color original image Fb according to the viewpoint position is created. It is also possible to prepare a plurality of multicolor original images and create a hologram recording medium in which these multicolor original images are switched and reproduced according to the viewpoint position.

<<< 4.5 Modified Example of Recording Color Original Image >>>
According to the above-described embodiment, when an original image composed of several parts is recorded, it becomes possible to record with different colors for each part, and recording of a multicolor original image as a whole is possible. It becomes possible. Here, a method of recording a general color original image together with color information and reproducing the color information will be described. Various examples of such a method for recording a color original image are disclosed in Japanese Patent Application Laid-Open No. 2000-214751. For details, refer to the publication. First, here, two kinds of original images Fa and Fb as shown in FIG. 22 are prepared. Here, the original image Fa is a monochrome original image, but the original image Fb is a color image expressed by combining three primary colors of RGB, and a red component image Fb (R), a green component image Fb (G), and a blue component. The image (B) can be decomposed into three images.

  When such two original images Fa and Fb are recorded, a recording area belonging to the group Ga and a recording area belonging to the group Gb are defined on the recording surface. The recording areas belonging to the group Gb to be recorded are further divided into three divided areas. For example, in the example shown in FIG. 23, four recording areas A1 to A4 belonging to the group Ga and four recording areas B1 to B4 belonging to the group Gb are alternately defined on the recording surface, and Each of the recording areas B1 to B4 is further divided into three divided areas. Specifically, for example, the recording area B1 is divided into three divided areas B1 (R), B1 (G), and B1 (B).

  Here, the information of the original image Fa is recorded in each of the recording areas A1 to A4 belonging to the group Ga, but each color component constituting the original image Fb is recorded in each of the recording areas B1 to B4 belonging to the group Gb. Only the information related to the image is recorded. That is, only information related to the interference fringes of the object light emitted from the red component image Fb (R) is recorded in the divided region B1 (R), and emitted from the green component image Fb (G) in the divided region B1 (G). Only the information related to the interference fringes of the object light thus recorded is recorded, and only the information related to the interference fringes of the object light emitted from the blue component image Fb (B) is recorded in the divided region B1 (B). At this time, for recording in the divided area B1 (R), interference fringes using the object light having the wavelength corresponding to red emitted from the red component image Fb (R) and the reference light having the same wavelength are calculated. For recording in the divided area B1 (G), interference fringes using the object light having the wavelength corresponding to the green color emitted from the green component image Fb (G) and the reference light having the same wavelength are calculated, and the divided area B1 is obtained. For recording in (B), interference fringes are calculated using object light having a wavelength corresponding to blue emitted from the blue component image Fb (B) and reference light having the same wavelength.

  If recording is performed by such a method, the original image Fa is reproduced as a single color image when irradiated with white reproduction illumination light and observed from a predetermined viewpoint position, but the original image Fb has three types of RGB. It will be reproduced as a color image with color. Of course, a color image does not necessarily have to be represented by the three primary colors RGB, and generally may be represented by the T primary color. In this case, the recording area belonging to the group corresponding to the color primary image expressed in the T primary color is divided into T divided areas (T ≧ 2), and the t th (1 ≦ t ≦ T) divided area. If the interference fringes between the object light corresponding to the t-th color component from the original image having T color components and the reference light of the same color as the object light are recorded, When the reproduction illumination light is irradiated and observed from a predetermined viewpoint position, the original image is reproduced as a color image having T colors.

  However, in reality, when reproduction is performed using white illumination light, a phenomenon occurs in which reproduced images of various color components are mixed and the reproduced image becomes cloudy. Therefore, in this embodiment as well, the object described in §3 is used. It is preferable to adopt a method of limiting the light spread angle. Even when white illumination light is irradiated from the same direction, there is a slight difference in the reproduction light emission direction for each color component, so that the reproduction light of each color component of the T primary color is directed to exactly the same viewpoint position. In order to achieve this, it is preferable to perform color-specific correction on the incident angle of the reference light during recording. For example, the divided regions B1 (R), B1 (G), and B1 (B) in FIG. 23 are irradiated with red, green, and blue object light and reference light, respectively. If correction is performed to slightly change the irradiation angle in red, green, and blue, respectively, when reproduction is performed by irradiating with white illumination light, red reproduction light emitted from the divided region B1 (R) and divided The green reproduction light emitted from the area B1 (G) and the blue reproduction light emitted from the divided area B1 (B) can be directed to the same viewpoint position.

  In the above-described embodiment, as shown in FIG. 22, a hologram recording medium capable of switching and reproducing the monochrome original image Fa and the color original image Fb according to the viewpoint position is created. It is also possible to prepare a holographic recording medium in which various color original images are prepared and the color original images are switched and reproduced according to the viewpoint position.

<<< §5. Combination with diffraction grating pattern >>
In the embodiments described so far, a plurality of original images are recorded as interference fringes in different recording areas, and the observed original images can be switched according to the viewpoint position. Here, a mode in which an original image recorded as interference fringes and an original image recorded as a diffraction grating pattern can be switched during observation will be described. First, a method for recording an original image as a diffraction grating pattern will be briefly described. Various examples of this method are disclosed in, for example, JP-A-6-337622, JP-A-8-21909, and JP-A-8-75912. For details, refer to these publications. Please refer.

  The method described so far for recording an original image as interference fringes is basically a method based on the principle of hologram, and can record a three-dimensional stereoscopic image. On the other hand, the method of recording an original image as a diffraction grating pattern is basically a method of expressing an image as a set of pixels composed of diffraction gratings, and can only record a two-dimensional planar image. Therefore, the medium recorded by this method should be a pseudo hologram, not an original hologram. Consider a two-dimensional original image as shown in FIG. FIG. 24B shows pixel information of the original image. This original image is composed of 7 × 7 pixels, and is a binary image in which each pixel has a pixel value of “1” or “0”.

  On the other hand, a pixel pattern as shown in FIG. 25 is prepared. In FIG. 25, one pixel pattern is shown in an enlarged manner, but actually, the size of this pixel pattern corresponds to the size of one pixel constituting the original image shown in FIG. This pixel pattern is a pattern made of a diffraction grating. Inside, a lattice line L having a line width d is arranged in the closed region V at a pitch p with a predetermined arrangement angle θ. Here, if the XY coordinate system is defined as shown in the figure, the arrangement angle θ of each grid line L can be defined as an angle formed with the X axis, for example. Of course, since this pixel pattern is a diffraction grating pattern, the pitch p of the grating lines L is set to a dimension close to the wavelength of light, and the set of grating lines L needs to function as a diffraction grating.

  Now, when the pixel pattern shown in FIG. 25 is assigned to each pixel having the pixel value “1” in the original image shown in FIG. 24, a diffraction grating pattern as shown in FIG. 26 is obtained. As shown in FIG. 27, such an assignment operation can be performed by a simple calculation process if the position of each pixel is expressed by coordinate values (a, b). Eventually, a diffraction grating pattern representing a desired original image can be obtained as image data by computer calculation. If the image data obtained in this way is given to, for example, an electron beam drawing apparatus and a diffraction grating pattern is formed as an uneven structure on an actual medium, this medium will function as a pseudo-hologram recording medium. Become. That is, when observing a medium on which a diffraction grating pattern as shown in FIG. 26 is recorded, since pixel portions having a pixel value “1” are diffraction gratings, some diffracted light is observed from these pixel portions. It will be. With this diffracted light, the letter “A” can be recognized in the example shown in FIG. The intensity and wavelength of the diffracted light obtained in the environment of white illumination light changes when the viewpoint position is moved (or the medium itself is moved), so that a visual effect close to that obtained when observing the hologram reproduction image is obtained. become.

  In fact, the original image recorded as a diffraction grating pattern in this way has a feature that a bright and clear reproduced image can be obtained as compared with an original image recorded as a general hologram image. For this reason, it is often used for recording planar images such as characters and marks that require sharp outlines.

  A method has also been proposed in which a plurality of original images are recorded as a diffraction grating pattern superimposed on the same recording medium, and the reproduced original images can be switched by changing the viewpoint position. Has already been put to practical use. For example, two diffraction grating patterns P (A) and P (B) as shown in FIG. 28 are prepared. Here, the diffraction grating pattern P (A) is a pattern constituting the letter “A”, and the diffraction grating pattern P (B) is a pattern constituting the letter “B”. A pixel pattern as shown in FIG. 25 is assigned to a portion constituting each character (a pixel portion having a pixel value “1”). However, the arrangement angle θ of the grid line of the pixel pattern allocated in the diffraction grating pattern P (A) is 45 °, whereas the grid line of the pixel pattern allocated in the diffraction grating pattern P (B) is 45 °. The arrangement angle θ is 90 °. In addition, since both the diffraction grating patterns P (A) and P (B) are configured so that the pixel pattern is not assigned to the pixel positions indicated by the same coordinates at the same time. By overlapping the patterns P (A) and P (B), a diffraction grating pattern P (AB) as shown in FIG. 29 can be obtained.

  When such a diffraction grating pattern P (AB) is formed on an actual medium, the character “A” is recognized or the character “B” is recognized by changing the viewpoint position. This is because the direction of the diffracted light is determined by the arrangement angle θ of the grating lines constituting the diffraction grating. That is, if the observation is made with a viewpoint at the position where the diffracted light from the diffraction grating having the grating line arrangement angle θ = 45 ° arrives, only the diffraction grating pattern P (A) shown in FIG. ”Is recognized, but if the observation is made with the viewpoint at the position where the diffracted light from the diffraction grating having the grating line arrangement angle θ = 90 ° arrives, only the diffraction grating pattern P (B) shown in FIG. Since it is observed, the letter “B” is recognized.

  The embodiment described here is a combination of the original image recording method using the interference fringes described up to §4 and the above-described original image recording method using the diffraction grating pattern. Here, it is assumed that four original images Fa, Fb, Fc, and Fd are prepared as shown in FIG. Here, the original images Fa and Fc are stereoscopic original images and are images to be recorded by interference fringes, whereas the original images Fb and Fd are planar original images and images to be recorded by a diffraction grating pattern. It is. For convenience of explanation, an example in which an image to be recorded with interference fringes is a three-dimensional image and an image to be recorded with a diffraction grating pattern is a planar image is shown. However, an original image to be recorded with interference fringes is not necessarily It need not be a stereoscopic image. For example, the planar original images Fb and Fd shown in FIG. 30 can be recorded by interference fringes. In this case, a state in which the two-dimensional character string is arranged in the three-dimensional space is recorded as a hologram three-dimensional image.

  FIG. 31 is a conceptual diagram showing a medium in which the stereoscopic original image Fa shown in FIG. 30 is recorded as interference fringes in the recording area A and the planar original image Fb is recorded as a diffraction grating pattern in the recording area B. FIG. 31 shows the state in which the original images Fa and Fb are displayed at the same time for convenience. The incident direction of the reference light with respect to the recording surface when recording the interference fringes in the recording area A, and the recording area B are shown. The original image Fa recorded as interference fringes and the original image Fb recorded as diffraction grating patterns are respectively adjusted by adjusting the relationship between the arrangement direction of the grating lines when the diffraction grating pattern is recorded inside. It can be configured to be reproduced when observed at different viewpoint positions.

  FIG. 32 is a plan view showing the configuration of each recording area when all of the four original images Fa, Fb, Fc, and Fd shown in FIG. 30 are recorded on the same recording medium. Each recording area belonging to four groups Ga, Gb, Gc, and Gd corresponding to Fa, Fb, Fc, and Fd is shown. That is, recording areas A1, A2, A3, A4 belonging to the interference fringe recording group Ga and recording areas C1, C2, C3, C4 belonging to the interference fringe recording group Gc are alternately arranged in the central portion. Has been. Here, interference fringes between the object light from the original image Fa and the predetermined reference light are recorded in the recording areas A1, A2, A3, and A4, and the original image Fc is recorded in the recording areas C1, C2, C3, and C4. Interference fringes between the object light from and the predetermined reference light are recorded. On the other hand, recording areas B1, B2 belonging to the diffraction grating recording group Gb and recording areas D1, D2 belonging to the diffraction grating recording group Gd are arranged at the four corners. Here, the original image Fb is recorded as a diffraction grating pattern in each of the recording areas B1 and B2, and the original image Fd is recorded as a diffraction grating pattern in the recording areas D1 and D2 (in the recording areas B1 and B2). The same contents are recorded and the same contents are also recorded in the recording areas D1 and D2.)

  Also in this case, the incident direction with respect to the recording surface of the reference light when the interference fringes are recorded in the recording areas A1 to A4 and the recording areas C1 to C4, and the diffraction gratings in the recording areas B1 and B2 and the recording areas D1 and D2 It is possible to arbitrarily set which original image is to be observed at a specific viewpoint position by adjusting the relationship between the arrangement direction of the grid lines when recording the pattern. For example, when observed from the first viewpoint position, as shown in FIG. 33, the original image Fa recorded in the recording areas A1 to A4 and the original image Fb recorded in the recording areas B1 and B2 Are simultaneously observed and observed from the second viewpoint position, as shown in FIG. 34, the original image Fc recorded in the recording areas C1 to C4 and the original images recorded in the recording areas D1 and D2 are displayed. It can also be set so that the image Fd is observed simultaneously. Of course, it is possible to set the original images Fa, Fb, Fc, and Fd to be observed separately at four different viewpoint positions, and any setting can be made according to preference. . In short, for the original image recorded as interference fringes, the observable viewpoint position can be freely set by adjusting the angle of the reference light at the time of recording. For the original image recorded as the diffraction grating pattern, The observable viewpoint position can be freely set by adjusting the lattice line angle in the pixel pattern assigned to the pixel position.

  The hologram recording medium according to the embodiment described here is eventually provided with a plurality of recording areas on the recording surface of the medium, and each recording area has N interference fringe recording groups (N ≧ 1) and K patterns. In the recording area belonging to any one of the diffraction grating recording groups (K ≧ 1) and belonging to the nth (1 ≦ n ≦ N) interference fringe recording group. Interference fringes of the object light from the interference fringe recording original image and the nth reference light among the N patterns are recorded and belong to the kth (1 ≦ k ≦ K) diffraction grating recording group. In the recording area, the k-th original image for recording a diffraction grating is recorded as a diffraction grating pattern.

  Here, in order to reproduce a plurality of N kinds of original images for interference fringe recording when viewed from N viewpoint positions, different N images at the time of interference fringe recording (N ≧ 2) The incident directions of the reference light with respect to the recording surface may be set to be different from each other. When a plurality of K diffraction grating recording original images are observed from K viewpoint positions, they are different from each other. In order to reproduce an image, each original image may be recorded by diffraction gratings having different radiation directions of diffracted light (in other words, diffraction gratings having different grating line arrangement angles).

  FIG. 35 is a plan view showing the configuration of each recording area in the case where the stereoscopic original image Fa and the planar original image Fb shown in FIG. 30 are recorded on the same recording medium, and the two original images Fa, Each recording area belonging to two groups Ga and Gb respectively corresponding to Fb is shown. That is, in this example, the recording areas A1 to A6 belonging to the interference fringe recording group Ga and the recording areas B1 to B5 belonging to the diffraction grating recording group Gb are alternately arranged. FIG. 36 is a plan view showing a state in which interference fringes or diffraction grating patterns are actually recorded on the medium in which each recording area is defined as shown in FIG. In this example, the vertical widths (specifically, 50 μm) of the recording areas A1 to A6 and B1 to B5 are set so as to correspond to the vertical width of one pixel constituting the original image Fb. Therefore, each of the recording regions B1 to B5 is assigned a diffraction grating pattern corresponding to a pixel array for one row. Of course, the vertical width of each of the recording areas B1 to B5 is set to W times the vertical width of one pixel, and the diffraction grating pattern corresponding to the pixel array of W rows in each of the recording areas B1 to B5. May be assigned. In each of the recording areas A1 to A6, interference fringes between the object light from the original image Fa and the predetermined reference light are recorded.

  Also in the embodiment as shown in FIG. 36, when the interference fringes are recorded in the recording areas A1 to A6, the incident direction with respect to the recording surface of the reference light and when the diffraction grating pattern is recorded in the recording areas B1 to B5. By adjusting the relationship with the arrangement direction of the grid lines, it is possible to set so that only the original image Fa is observed at a certain viewpoint position and only the original image Fb is observed at another viewpoint position.

  FIG. 37 is a plan view showing the configuration of each recording area in the case where the stereoscopic original images Fa and Fc and the planar original image Fb shown in FIG. 30 are recorded on the same recording medium. Each recording area belonging to three groups Ga, Gb, and Gc corresponding to Fa, Fb, and Fc is shown. That is, in this example, the recording areas A1 to A3 belonging to the interference fringe recording group Ga, the recording areas B1 to B5 belonging to the diffraction grating recording group Gb, and the recording areas C1 to C3 belonging to the interference fringe recording group Gc , Are regularly arranged. FIG. 38 is a plan view showing a state in which interference fringes or diffraction grating patterns are actually recorded on the medium in which each recording area is defined as shown in FIG. A diffraction grating pattern corresponding to a pixel array for one row of the original image Fb is assigned to each of the recording areas B1 to B5, and object light from the original image Fa and a predetermined amount are assigned to each of the recording areas A1 to A3. Interference fringes with reference light are recorded, and interference fringes between object light from the original image Fc and predetermined reference light are recorded in the recording areas C1 to C3.

  Also in the embodiment as shown in FIG. 38, the incident direction with respect to the recording surface of the reference light when the interference fringes are recorded in the recording areas A1 to A3 and the interference fringes in the recording areas C1 to C3 are recorded. If the relationship between the incident direction of the reference light with respect to the recording surface and the arrangement direction of the grating lines when recording the diffraction grating pattern in the recording areas B1 to B5 is adjusted, only the original image Fa is observed at a certain viewpoint position. Further, it is possible to set so that only the original image Fb is observed at another viewpoint position, and only the original image Fc is observed at another viewpoint position.

  Incidentally, as in the example shown in FIG. 38, a plurality of recording areas belonging to the same group are arranged in a distributed manner on the entire recording surface, so that the spatial area of the recording areas belonging to the same interference fringe recording group can be reduced. If the spatial arrangement period of recording areas belonging to the same diffraction grating recording group is set shorter than the arrangement period, the resolution of the original image recorded using the diffraction grating pattern is recorded using interference fringes. It can be higher than the resolution of the original image. For example, in the example of FIG. 38, the recording areas A1, A2, and A3 belonging to the interference fringe recording group Ga are arranged with a period of four rows, but the recording areas B1 to B5 belonging to the diffraction grating recording group Gb. Are arranged in a cycle of two rows, and the resolution of the original image Fb is high. In general, an original image recorded using a diffraction grating pattern can be used to record an original image composed of characters, marks, and the like because a brighter and clearer reproduced image can be obtained than an original image recorded using interference fringes. Often. Therefore, it is preferable to increase the resolution of the original image recorded using the diffraction grating pattern because the resolution of characters and marks can be increased.

  FIG. 39 is a plan view showing the configuration of each recording area when all of the four original images Fa, Fb, Fc, and Fd shown in FIG. 30 are recorded on the same recording medium. Each recording area belonging to four groups Ga, Gb, Gc, and Gd corresponding to Fa, Fb, Fc, and Fd is shown. That is, the recording areas A1, A2, A3 belonging to the interference fringe recording group Ga, the recording areas B1, B2, B3 belonging to the diffraction grating recording group Gb, and the recording areas C1, C2, belonging to the interference fringe recording group Gc. C3 and recording areas D1, D2, and D3 belonging to the diffraction grating recording group Gd are periodically arranged. The original images Fb and Fd recorded using the diffraction grating pattern can be observed from different viewpoint positions by changing the grid line arrangement angle of the pixel pattern to be used. If the incident direction of the reference light at the time of interference fringe recording is adjusted, it is possible to set so that all of the four original images Fa, Fb, Fc, and Fd are observed at different viewpoint positions.

  As mentioned above, although this invention was demonstrated based on some embodiment shown in figure, this invention is not limited to these embodiment, In addition, it can implement with a various form. For example, the hologram recording medium according to the present invention is practically preferably created as a computer generated hologram by calculation using a computer. However, if a physical operation is possible, all or part of the creation process is performed. It may be performed by an optical method.

10 ... Original image 20 ... Recording medium (recording surface)
A, A1 to A6 ... recording areas B, B1 to B5, B1-1 to B3-2, Bα1, Bα2, Bβ1, Bβ2 ... recording areas B1 (R), B1 (G), B1 (B) to B4 (R ), B4 (G), B4 (B)... Divided areas C, C1 to C4, Ci... Recording areas D1 to D3... Recording areas d... Line widths Fa, Fb, Fc, Fd ... original images Fb.alpha., Fb.beta. Original image Fb (R), Fb (G), Fb (B)... Each color component image Ga, Gb, Gc, Gd, Gbα, Gbβ... Group and subgroup h. L1 to L3, Li, unit line segment N, normal line O, O1, Oi, OI, Oa, Ob, Oc, object light P, P1, Pi, PI, point light sources P11 to P33, Pij, unit on the original image Point light sources P (A), P (B), P (AB) on the line segment ... Diffraction grating pattern p ... H Q, Q (x, y) ... one point R, Ra, Rb, Rc on the recording surface ... reference light Ryz, Rxz, Rxy ... projected image S of the reference light S ... irradiation area V of the object light ... closed area θ ... Lattice line arrangement angles θyz, θxz, θxy ... An angle indicating the incident direction of the reference light Ψ ... A spread angle in the X-axis direction of the object light ξ ... A spread angle in the Y-axis direction of the object light

Claims (18)

A plurality of recording areas are provided on the recording surface of the medium, and each recording area belongs to one of N groups (N ≧ 2) and belongs to the nth group (1 ≦ n ≦ N). In the recording area to be recorded, interference fringes between the object light from the nth original image of the N ways and the nth reference light of the N ways are recorded. The incident directions of the street reference light with respect to the recording surface are set to be different from each other, and when viewed from N viewpoint positions, different original images are reproduced .
In addition, a plurality of recording areas belonging to the same group are distributed over the entire recording surface, and belong to the distributed nth group when observed from the nth viewpoint position. A hologram recording medium, wherein an nth original image is observed by light from a recording area. The hologram recording medium according to claim 1 ,
A hologram recording medium characterized in that a plurality of recording areas belonging to the same group are regularly arranged on the recording surface at a constant period. The hologram recording medium according to claim 1 or 2 ,
On the recording surface defined on the XY plane, a large number of rectangular recording areas that are elongated in the X-axis direction are arranged in the Y-axis direction so that the recording areas adjacent in the Y-axis direction belong to different groups. A holographic recording medium comprising: In the hologram recording medium according to any one of claims 1 to 3 ,
When the reference light incident on the recording surface defined on the XY plane is projected onto the YZ plane, the angle θyz formed by the projected image and the normal set up on the recording surface is substantially the same for all N reference lights. Thus, when projected onto the XZ plane, the angle θxz between the projected image and the normal set up on the recording surface is set so that the angle θxz is sufficiently different as necessary for observing different original images. A holographic recording medium comprising: In the hologram recording medium according to any one of claims 1 to 3 ,
When the reference light incident on the recording surface defined on the XY plane is projected onto the YZ plane, the angle θyz formed by the projected image and the normal set up on the recording surface differs for all N reference lights. The setting is such that the angle θxz formed by the projected image and the normal line standing on the recording surface is substantially the same for all N reference lights when projected onto the XZ plane, sufficiently different to the extent necessary for observing the original image. A hologram recording medium characterized by being made. In the hologram recording medium according to any one of claims 1 to 3 ,
The angle formed between the reference light incident on the recording surface defined on the XY plane and the normal line standing on the recording surface is substantially the same for all N reference lights, and this reference light is applied to the recording surface. A hologram characterized in that, when projected, all the reference beams having N angles between the projected image and the X-axis or the Y-axis are set to be sufficiently different as necessary for observation of different original images. recoding media. In the hologram recording medium according to any one of claims 1 to 6 ,
A hologram recording medium on which interference fringes obtained by limiting the spread angle of object light from an original image toward a recording surface are recorded. In the hologram recording medium according to any one of claims 1 to 7 ,
Each of the N original images is composed of one frame of still images constituting a series of moving images, and when the viewpoint position is changed in N ways with time, a moving image composed of N frames can be observed. A holographic recording medium comprising: The hologram recording medium according to claim 8 , wherein
A moving image is composed of still images of a plurality of frames including the same display object, and a moving image is observed showing a state in which the display object moves by changing the display position of the display object in each frame. A hologram recording medium configured to be capable of performing the above. In the hologram recording medium according to any one of claims 1 to 9 ,
For a specific group, there are further defined M (M ≧ 2) subgroups, and each recording area belonging to the mth (1 ≦ m ≦ M) subgroup is colored with a single color. Among the original images composed by combining the M single-color partial original images, interference fringes between the object light from the m-th single-color partial original image and the reference light having the same color as the object light are recorded. The original image is reproduced as a color image having M colors when irradiated with white reproduction illumination light and observed from a predetermined viewpoint position. Hologram recording medium. In the hologram recording medium according to any one of claims 1 to 9 ,
Each recording area belonging to a specific group is divided into T divided areas (T ≧ 2), and the tth (1 ≦ t ≦ T) divided area has T color components. Interference fringes between the object light corresponding to the t-th color component from the original image and the reference light of the same color as the object light are recorded, and white reproduction illumination light is irradiated from a predetermined viewpoint position. A hologram recording medium configured to reproduce the original image as a color image having T colors when observed. A plurality of recording areas are provided on the recording surface of the medium, and each recording area belongs to one of N interference fringe recording groups (N ≧ 1) and K diffraction grating recording groups (K ≧ 1). In the recording area belonging to the nth (1 ≦ n ≦ N) interference fringe recording group, the object light from the nth interference fringe recording original image and N ways Interference fringes with the nth reference beam are recorded, and the kth of the K patterns (1 ≦ k ≦ K) in the recording area belonging to the kth (1 ≦ k ≦ K) diffraction grating recording group. The original image for recording a diffraction grating is recorded as a diffraction grating pattern ,
In addition, a plurality of recording areas belonging to the same interference fringe recording group are distributed over the entire recording surface, and when observed from the nth viewpoint position, the nth interferences are distributed. A hologram recording medium, wherein the nth original image is observed by light from a recording area belonging to a fringe recording group. The hologram recording medium according to claim 12 ,
By adjusting the relationship between the incident direction of the reference beam on the recording surface when recording the interference fringes and the arrangement direction of the grating lines when recording the diffraction grating, the original image for recording the interference fringes and the diffraction grating recording are adjusted. A hologram recording medium configured to be reproduced when an original image is observed at different viewpoint positions. The hologram recording medium according to claim 12 ,
The incident directions of the N kinds (N ≧ 2) of the reference light with respect to the recording surface at the time of interference fringe recording are set to be different from each other, and different interference fringe recording originals are observed when viewed from N viewpoint positions. A hologram recording medium configured to reproduce an image. The hologram recording medium according to claim 12 ,
The K diffraction (K ≧ 2) diffraction grating recording original images are recorded by diffraction gratings having different radiation directions of the diffracted light. When observed from K viewpoint positions, the diffraction grating recording originals differ from each other. A hologram recording medium configured to reproduce an image. In the hologram recording medium according to any one of claims 1 to 15 ,
A hologram recording medium characterized in that the interference fringes or the interference fringes and the diffraction grating pattern are constituted by a fine uneven structure formed on the surface of the medium. A method for producing the hologram recording medium according to claim 1 ,
Covering the surface of the photosensitive plate constituting the recording surface with a light-shielding mask so that only the recording area belonging to the same group is exposed, and optically recording one original image in the exposed recording area A method for producing a hologram recording medium, wherein the method is repeatedly executed. A method for producing the hologram recording medium according to claim 1 ,
For each recording area, considering the group to which it belongs, the image data corresponding to the interference fringes or diffraction grating pattern to be recorded is obtained by calculation using a computer, and the pattern is formed on the physical medium based on the obtained image data. A method for producing a hologram recording medium, characterized in that