Patent Publication Number: US-2002012136-A1

Title: Image recording method and apparatus and image reproducing method and apparatus

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] This invention relates to an image recording method and apparatus for recording a stereographic image on a holographic stereogram and an image reproducing method and apparatus for reproducing a stereographic image from the holographic stereogram.  
       [0003] 2. Description of the Related Art  
       [0004] A holographic stereogram is produced by sequentially recording a large number of images, obtained on sequentially shooting an object from different viewing points, as original images, as strip- or dot-shaped hologram elements, on a sole recording medium.  
       [0005] For example, in a holographic stereogram having the parallax information only in the transverse direction, plural original images  301   a  to  301   e,  obtained on sequentially imaging an object  300  from plural viewing points in the transverse direction, are sequentially exposed to light and recorded on a recording medium for hologram  302  as strip-shaped hologram elements.  
       [0006] With the present holographic stereogram, since the picture information obtained on sequentially imaging an object from plural viewing points in the horizontal direction is sequentially recorded in the transverse direction as strip-shaped hologram elements, the two-dimensional pictures as viewed by left and right eyes of a viewer if the holographic stereogram is viewed by the viewer with both eyes. This the observer feels the parallax so that a three-dimensional image is reproduced.  
       [0007] However, with the conventional holographic stereogram, an optimum reproduced picture cannot be produced. Specifically, with the conventional holographic stereogram, a reproduced image is unclear, dark and poor in contrast, while the reproduced image has a narrow angle of visibility.  
       [0008] For enabling an optimum picture to be produced from a holographic stereogram,. it is necessary to completely fix a recording medium for hologram during light exposure of the recoding image to prevent minute vibrations even of the order of the light wavelength. During production of the holographic stereogram, the recording medium for hologram is moved little by little for sequentially recording an extremely large number of hologram elements. For providing a practically useful picture recording device used for producing a holographic stereogram, the recording medium for hologram needs to be transferred quickly during fabrication of the holographic stereogram. Therefore, means for holding and transferring the recording medium for hologram needs to be such a device in which not only the recording medium for hologram can be transferred quickly, but also no vibrations of the recording medium for hologram are allowed after completion and halting of the recording medium for hologram.  
       [0009] For example, if the recording medium for hologram is transferred using an ordinary electrically driven sliding stage, the time of the order of 2 seconds is required until the vibrations of the recording medium for hologram are attenuated, after transfer of the recording medium for hologram, to the extent that the hologram elements can be formed. Therefore, if the recording medium for hologram is transferred each time the hologram element is formed using the electrically driven stage, an extremely long time is consumed until completion of a sole holographic stereogram.  
       [0010] The present inventors have conducted searches into holding and transfer means capable of suppressing the vibrations of the recording medium for hologram more quickly. Thus it has been found that, by loading an elongated recording medium for hologram between two parallel rolls, holding the recording medium for hologram by a torsion coil spring for producing a pre-set tensile force and by causing an object light to fall on the recording medium for hologram placed between the two parallel rolls, the vibrations of the recording medium for hologram can be suppressed more promptly. By employing this method, the time until attenuation of the vibrations after transfer of the recording medium for hologram has been reduced to less than one fourth that when the electrically driven sliding stage is used. However, if this method is employed, the vibrations cannot be suppressed completely. Thus, it has been desired to develop a method and apparatus capable of further suppressing vibrations of the recording medium for hologram.  
       [0011] In a usual hologram, an illuminating light source for reproducing a three-dimensional picture and a hologram are spatially separated from each other. Thus, in a usual hologram, a broad spacing is required for reproduction. On the other hand, for reproduction under an optimum condition, the relative positions of the hologram and the illuminating light source need to be set under a pre-set condition. This applies for a holographic stereogram made up of plural hologram elements.  
       [0012] If the illuminating light source and the hologram are unified with each other, the spacing for illumination becomes unnecessary to make it possible to reduce the size of the apparatus. Moreover, since the relative positions of the hologram and the illuminating light become always constant, reproduction can be performed at all times under optimum conditions. As a hologram for realizing this, there is known an edge-lit system hologram in which recording and/or reproduction is carried out with a recording medium bonded to a transparent light-inlet block.  
       [0013] With such edge-lit system hologram, the optical system for reproduction can be reduced in size and reproduction can be performed at all times under optimum conditions by unifying the light source for the reproducing illuminating light and a light inlet block. Also, since the angle of incidence of the reproducing illuminating light is increased with the edge-lit type hologram, an image is not reproduced by the light incident from outside the light inlet block. Thus the edge lit type hologram is in use in a field in which it is not desirable for an image to be reproduced with, for example, the sunlight, such as in a head-up display device.  
       [0014] For producing a transmission type hologram in which a three-dimensional image is reproduced by the light transmitted through the recording medium, a recording medium for hologram  311  is bonded to a surface  310   a  of a light inlet block  310  formed of a glass plate or a synthetic resin plate of a suitable thickness, as shown in Fig.2. At this time, the recording medium for hologram  311  is bonded via an index matching liquid  312  to the light inlet block  310 . An object light beam  314  from an object  313  is illuminated from an other surface  310   b  of the light inlet block  310  towards the recording medium for hologram  311 , while a reference light beam  315  is illuminated from an end face  310   c  of the light inlet block  310  towards the recording medium for hologram  311 . This completes a transmission type edge-lit hologram.  
       [0015] For reproducing the thus produced transmission type edge-lit hologram, the hologram  321  is bonded on an end face  320   a  of the light inlet block  320  via an index matching liquid  322  and a reproducing illuminating light beam  323  is illuminated from the end face  320   b  of the light inlet block  320  towards the hologram  321 . The light transmitted through the hologram  321  is diffracted at this time by the hologram  321 . A reproduced image  325  is generated by a diffracted light beam  324  so as to be viewed by a viewer  326 .  
       [0016] For producing a reflection type hologram in which a three-dimensional image is reproduced by the light reflected by the recording medium, by the edge-lit system, a recording medium  332  is bonded via an index matching liquid  331  on one surface  330   a  of a light inlet block  330 , as in the case of producing a transmission type edge-lit hologram, as shown in FIG. 4. For the reflection type hologram, an object light beam  334  from an object  333  is illuminated from the side of bonding the recording medium  332  towards the recording medium  332 , while a reference light beam  335  is illuminated from an end face  330   b  of the light inlet block  330 . This completes the edge-lit reflection type hologram.  
       [0017] For reproducing the edge-lit reflection type hologram, thus produced, usually a hologram  341  is bonded via an index matching liquid  342  to a surface  340   a  of a light inlet block  340 , as shown in FIG. 5, and a reproducing illuminating light beam  343  is illuminated towards the hologram  341  from an end face  340   b  of the light inlet block  340 . The light reflected at this time by the hologram  341  is diffracted by the hologram  341 . A reproduced image is generated by this diffracted light  344  so as to be viewed by a viewer  346 .  
       [0018] If such edge-lit system is applied to a holographic stereogram, and an image is generated as if there were an object behind the light inlet block, the reproduced image is difficult to view and lowered in stereographic feeling to detract from the display effect. It is therefore desirable that an image can be reproduced so that an object will be as close to the view as possible. However, with the edge-lit system holographic stereogram, an image is reproduced as if the object as viewed by the viewer were at back of the light inlet block, as shown in FIG. 5.  
       [0019] For producing the image as though the object were as close to the viewer as possible, a transmission type edge-lit system holographic stereogram is preferably employed. However, if the stereogram is recorded by the transmission type hologram, both the object light beam and the reference light beam need to be incident on one side of the recording medium for hologram. This lowers the degree of freedom in arranging the optical system to raise difficulties in constituting an optimum optical system.  
       [0020] Moreover, if desired to assure a broad angle of visibility angle in the up-and-down direction in reproducing a holographic stereogram, a one-dimensional diffusion plate for diffusing the object light beam in a one-dimensional in-plane direction is desirably provided in the vicinity of the recording medium for hologram on the object light beam incident side. However, with the transmission type recording n which a light incident block needs to be arranged towards the object light beam incident side, it becomes impossible to array this one-dimensional diffusion plate. Consequently, it has hitherto not been practiced to produce the edge-lit system holographic stereogram as a transmission type stereogram.  
       SUMMARY OF THE INVENTION  
       [0021] It is therefore an object of the present invention to provide an image recording method and apparatus in which an image is recorded on a holographic stereogram so as to produce a better reproduced image.  
       [0022] It is another object of the present invention to provide an image reproducing method and apparatus which renders it possible produce a better reproduced image from the holographic stereogram.  
       [0023] In a first image recording method for sequentially recording images corresponding to image data of a parallax image string as strip- or dot-shaped hologram elements, by causing an object light beam to fall on one of the surfaces of a recording medium for hologram and by causing a reference light beam to fall on the opposite surface thereof, according to the present invention, an optical component is contacted with at least one surface of the recording medium for hologram, and a liquid is interposed between the recording medium for hologram and the optical component.  
       [0024] If a liquid is interposed between the recording medium for hologram and the optical component, the optical component can be tightly contacted with the recording medium for hologram without producing a void therebetween, so that vibrations of the recording medium for hologram during image recording can be suppressed sufficiently.  
       [0025] It may be contemplated to have the recording medium for hologram and the optical component arranged in a liquid for having the liquid interposed between the recording medium for hologram and the optical component. Herein, however, the recording medium for hologram and the optical component are arranged in air and the liquid is held by surface tension between the recording medium for hologram and the optical component.  
       [0026] For maintaining the liquid charged at all times in the space between the recording medium for hologram and the optical component, it is preferred that the liquid be continuously supplied to the space between the recording medium for hologram and the optical component.  
       [0027] The optical component contacted with the recording medium for hologram via liquid is preferably a set of a one-dimensional diffusion plate and a louver film arranged on the object light incident side. For example, the optical component, comprised of the set of the one-dimensional diffusion plate and the louver film, is thrust, during recording on the recording medium for hologram, against the recording medium for hologram placed under pre-set tensile tension. The one-dimensional diffusion plate performs the role of slightly diffusing the object light during recording in a one-dimensional direction for maintaining a broad angle of visibility in the up-and-down direction for scattering noise components ascribable to, for example, the optical system. On the other hand, the louver film prevents the reference light from being reflected by, for example, the above-mentioned one-dimensional diffusion plate to be re-incident on the recording medium for hologram after passing through the recording medium for hologram.  
       [0028] The hologram of the edge-lit system has many merits, as described above. Thus the edge-lit system may be applied to the above-mentioned first image recording method. In such case, the images corresponding to respective image data of the parallax image series are sequentially recorded as hologram elements by the edge-lit system.  
       [0029] In the edge-lit system, a recording medium for hologram is bonded to a transparent light inlet block, which then causes the reference light beam or the illuminating light beam to fall at an acute angle on the surface of the recording medium for hologram for recording or reproduction. If the edge-lit system is applied to the holographic stereogram, the illuminating light source can be integrated to the holographic stereogram, thus eliminating the necessity for providing an illuminating space. Morever, since the relative position between the holographic stereogram and the illuminating light source becomes perpetually constant, reproduction can be done perpetually under optimum conditions.  
       [0030] For recording by the edge-lit system, the light inlet block can be contacted with the recording medium for hologram from the object light incident side or from the reference light incident side. However, even in case of recording by the edge-lit system, the one-dimensional diffusion plate and the louver film are preferably arranged in a contact area with the recording medium for hologram. In this case, the one-dimensional diffusion plate and the louver film are arranged on the object light inlet side, while the light inlet block is arranged on the reference light incident side of the recording medium for hologram. The light inlet block and the recording medium for hologram are contacted with each other via a liquid. If, in the following description, it is necessary to clarify the fact that the light inlet block is arranged on the reference light incident side, the light inlet block is termed a reference light inlet block. If the reference light inlet block s contacted with the recording medium for hologram, the liquid interposed therebetween is preferably an index matching liquid responsible for index matching between the recording medium for hologram and the reference light inlet block.  
       [0031] If, during recording by the edge-lit system, the refractive index is changed drastically between the recording medium for hologram and the light inlet block, the reference light beam, incident at an acute angle on the surface of the recording medium for hologram, is reflected by total reflection on an interface between the light inlet block and the recording medium for hologram, or surface irregularities of the image recording layer of the recording medium for hologram are presented as non-uniformities like wood grains in the recorded image. For overcoming these difficulties, light exposure may be carried out in a liquid capable of achieving index matching between the recording medium for hologram and the reference light inlet block. However, if the light exposure is carried out in a liquid, the image recording device becomes complex in structure and larger in size, while being in need for frequent maintenance, thus making it difficult to automate the fabrication of the holographic stereogram.  
       [0032] Conversely, should the index matching liquid be interposed only between the recording medium for hologram and the reference light inlet block, the reference light inlet block can be contacted completely intimately with the recording medium for hologram, while there is no risk of complicating the structure or increasing the size of the image recording device. In addition, since there is no necessity of transferring the reference light inlet block in a direction towards and away from the recording medium for hologram each time the recording medium for hologram is transferred, thus even simplifying the structure of the image recording device.  
       [0033] For enabling index matching between the recording medium for hologram and the reference light inlet block by the index matching liquid, it is necessary to set a condition in which no total reflection occurs on an interface between the reference light inlet block and the index matching liquid, as well as on an interface between the index matching liquid and the recording medium for hologram, and in which the intensity reflectance (s-component) on each interface is reduced.  
       [0034] If the liquid interposed between the reference light inlet block and the recording medium reference light inlet block and the recording medium for hologram meets the above condition, the reference light passed through the reference light inlet block and the recording medium to fall on the recording medium for hologram can be prevented to occur total reflection, while non-uniformities may be prevented from being produced in the image, thus improving the image quality of the fabricated holographic stereogram.  
       [0035] For implementing the above-described first image recording method, the following first image recording apparatus is used.  
       [0036] The first image recording apparatus for sequentially recording images corresponding to image data of a parallax image series as strip- or dot-shaped hologram elements by causing an object light beam to fall on one of the surfaces of a recording medium for hologram and by causing a reference light beam to fall on the opposite surface thereof, according to the present invention, includes an optical component contacted with at least one of the surfaces of the recording medium for hologram, and liquid supplying means for supplying a liquid to a space between the recording medium for hologram and the optical component.  
       [0037] Since the first image recording apparatus includes liquid supplying means, the liquid can be interposed between the recording medium for hologram and the optical component, and hence the optical component can be tightly contacted with the recording medium for hologram without voids in-between to suppress vibrations of the recording medium for hologram sufficiently.  
       [0038] The liquid supplying means is preferably capable of continuously supplying the liquid to a space between the recording medium for hologram and the optical component. Although any known means for supplying the liquid to the space between two members can be used as such liquid supplying means, a foamed member, such as sponge, impregnated with a liquid, is preferred. That is, by arranging a foamed member, such as a liquid-impregnated sponge, may be placed in the vicinity of the interface between the recording medium for hologram and the optical component for continuously supplying the liquid to a space between the recording medium for hologram and the optical component.  
       [0039] In the above-described image recording apparatus, the optical component contacted with the recording medium for hologram via the liquid may be a set of the one-dimensional diffusion plate and the louver film on the object light incident side. Alternatively, the optical component may be a reference light inlet block on the reference light incident side if recording is done by the edge-lit system. if the recording is by the edge-lit system, the index matching liquid may be used as the liquid interposed between the recording medium for hologram and the reference light inlet block, as explained previously.  
       [0040] For raising the light exploitation efficiency for reducing image non-uniformities, a smaller interface passed through by the reference light is desirable. Thus, if the edge-lit system is used, the recording medium for hologram and the reference light inlet block may be directly intimately contacted with each other, that is without interposition of a liquid. Above all, if the recording medium for hologram used is relatively soft and adhesive, such as photopolymer, the recording medium for hologram and the reference light inlet block can be contacted relatively easily with each other. In such case, since the reference light inlet block and the recording medium for hologram can be intimately contacted with each other, without voids in-between, oscillations of the recording medium for hologram can be suppressed sufficiently.  
       [0041] In light of the above, a second image recording method includes causing an object light beam to fall on one of the surfaces of a recording medium for hologram, the opposite surface of which is optically contacted with a light inlet block, and causing a reference light beam to fall on an end of the light inlet block for fabricating a holographic stereogram of the edge-lit system.  
       [0042] A second image recording apparatus includes a light inlet block optically contacted with at least one surface of a recording medium for hologram and is designed so that, for fabricating a holographic stereogram of an edge-lit system, an object light beam is caused to fall on one of the surfaces of the recording medium for hologram and a reference light beam is caused to fall on the opposite surface via a light inlet block.  
       [0043] Preferably, the light inlet block includes a light absorbing member operating for preventing the object light and the reference light incident on the light inlet block and reaching the recording medium for hologram from undergoing needless reflection within the light inlet block.  
       [0044] In the second image recording apparatus, a film-shaped medium is used as the above-mentioned recording medium for hologram. Although the index matching liquid may be interposed between the recording medium for hologram and the reference light inlet block, as described above, image recording may also be performed with the recording medium for hologram being kept in direct contact with the light inlet block.  
       [0045] Also, in the second image recording apparatus, the light inlet block is substantially cylindrical in shape and is designed to rotate with movement of the recording medium for hologram. Preferably, the light inlet block is designed to rotate with the recording medium for hologram being kept in direct contact with the light inlet block. Also preferably, the light inlet block has an internal hollow portion within which is arranged a light absorbing member designed for preventing the object light and the reference light incident on the light inlet block and reaching the recording medium for hologram from undergoing needless reflection in the light inlet block.  
       [0046] Preferably, the second image recording apparatus includes thrusting means for thrusting the light inlet block against the recording medium for hologram.  
       [0047] In the second image recording apparatus, a recording medium for hologram having a cover sheet for protecting a photosensitive portion may be used as the recording medium for hologram. Preferably, cover sheet removal means for peeling off the cover sheet from the recording medium for hologram is preferably provided before contacting the recording medium for hologram with the light inlet block.  
       [0048] Preferably, the second image recording apparatus includes cleaning means for removing contamination of the light inlet block. Also preferably, the second image recording apparatus includes a one-dimensional diffusion plate on the object light incident side in the vicinity of the recording medium for hologram.  
       [0049] An image reproducing method for reproducing a three-dimensional image recorded on a holographic stereogram of an edge-lit system by causing an object light beam and a reference light beam to fall on one and the other surfaces of a recording medium, respectively, according to the present invention, includes arranging a holographic stereogram on a surface of the light inlet block towards a viewer, illuminating a reproducing illuminating light beam on the holographic stereogram via the light inlet block, and reproducing the three-dimensional image by light diffracted when the reproducing illuminating light beam is transmitted through the holographic stereogram.  
       [0050] With the above image producing method, a holographic stereogram of the edge-lit system, recorded with the reflection type stylized optical system having high flexibility of layout, is reproduced with the transmission type hologram in which the holographic stereogram transmits the reproducing illuminating light beam. In this manner, a reproduced three-dimensional image appears as if the object were closer to the viewer, instead of being backwardly of the holographic stereogram.  
       [0051] An image reproducing apparatus for reproducing a three-dimensional image recorded on a holographic stereogram of an edge-lit system by causing an object light beam and a reference light beam to fall on one and the other surfaces of a recording medium, respectively, according to the present invention, includes a light inlet block having a holographic stereogram on its surface towards a viewer and a light source for illuminating a reproducing illuminating light beam via the light inlet bock on the holographic stereogram. The reproducing illuminating light beam from the light source is diffracted at the time of transmission through the holographic stereogram for reproducing the three-dimensional image.  
       [0052] With the above image producing apparatus, a holographic stereogram of the edge-lit system, recorded with the reflection type stylized optical system having high flexibility of layout, is reproduced with the transmission type hologram in which the holographic stereogram transmits the reproducing illuminating light beam. In this manner, a reproduced three-dimensional image appears as if the object were closer to the viewer, instead of being at back of the holographic stereogram. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0053]FIG. 1 is a schematic view showing a method for producing a holographic stereogram.  
     [0054]FIG. 2 is a schematic view showing a method for producing a transmission type edge-lit hologram.  
     [0055]FIG. 3 is a schematic view showing the reproducing method for reproducing a transmission type edge-lit hologram with a transmission type hologram.  
     [0056]FIG. 4 is a schematic view showing a method for producing a reflection type edge-lit hologram.  
     [0057]FIG. 5 is a schematic view showing the reproducing method for reproducing a reflection type edge-lit hologram with a reflection type hologram.  
     [0058]FIG. 6 is a schematic view showing an illustrative structure of a holographic stereogram printer system.  
     [0059]FIGS. 7A and 7B are schematic views showing an example of an optical system of a holographic stereogram printer system.  
     [0060]FIG. 8 is a cross-sectional view showing an example of a recording medium for hologram.  
     [0061]FIGS. 9A, 9B and  9 C are schematic views showing a photosensitive process of a light polymerization type photopolymer.  
     [0062]FIG. 10 is a schematic view showing an illustrative structure of the vicinity of a printer head.  
     [0063]FIG. 11 is a schematic view showing an illustrative structure of the vicinity of the printer head in case of recording by an edge-lit system.  
     [0064]FIG. 12 is a schematic view showing a reproducing method of a holographic system with a reflection type hologram.  
     [0065]FIG. 13 is a schematic view showing a reproducing method of a holographic system with a transmission type hologram.  
     [0066]FIG. 14 illustrates an incident path of the reference light beam for finding a condition of refractive index of a liquid.  
     [0067]FIG. 15 shows the relation between the refractive index of a liquid and the intensity reflectance for θ g =75°.  
     [0068]FIG. 16 shows the relation between the refractive index of a liquid and the intensity reflectance for θ g =78°.  
     [0069]FIG. 17 shows the relation between the refractive index of a liquid and the intensity reflectance for θ g =45°.  
     [0070]FIG. 18 is a schematic relation showing an illustrative structure of a holographic stereogram printer system.  
     [0071]FIGS. 19A and 19B are schematic views showing an example of an optical system of a holographic stereogram printer device.  
     [0072]FIG. 20 is a schematic view showing the manner of total reflection of a reference light beam on an interface of a recording medium for hologram.  
     [0073]FIG. 21 is a schematic view showing the manner of preventing the reference light beam from re-entering a recording medium for hologram by a louver film.  
     [0074]FIG. 22 is a schematic view showing an illustrative structure of the vicinity of a printer head of a holographic stereogram printer device of the type in which a recording medium for hologram is intimately contacted with a light inlet block.  
     [0075]FIG. 23 is a schematic view showing another illustrative structure of the vicinity of a printer head of a holographic stereogram printer device of the type in which a recording medium for hologram is intimately contacted with a light inlet block.  
     [0076]FIG. 24 is a schematic view showing an illustrative structure of the vicinity of a printer head of a holographic stereogram printer device of the type in which a liquid is interposed between the recording medium for hologram and the light inlet block.  
     [0077]FIG. 25 is a schematic view showing a reproducing method of a holographic stereogram by a reflection type.  
     [0078]FIG. 26 is a schematic view showing a reproducing method of a holographic stereogram by a transmission type.  
     [0079]FIG. 27 is a cross-sectional view showing an instance in which a louver film is inserted between a light inlet block and a recording medium for hologram.  
     [0080]FIG. 28 is a cross-sectional view showing another instance in which a louver film is inserted between a light inlet block and a recording medium for hologram.  
     [0081]FIG. 29 is a schematic view showing an illustrative structure of a stereographic stereogram producing system.  
     [0082]FIGS. 30A and 30B are schematic views showing an illustrative optical system of a holographic stereogram printer device.  
     [0083]FIG. 31 is a cross-sectional view showing an illustrative recording medium for hologram.  
     [0084]FIGS. 32A, 32B and  32 C are schematic views showing a photosensitive process of a photopolymerization type photopolymer.  
     [0085]FIG. 33 is a schematic view showing an illustrative structure of an illustrative structure of a recording medium feed mechanism.  
     [0086]FIG. 34 is a schematic view showing the method for a holographic stereogram with a reflection type hologram.  
     [0087]FIG. 35 is a schematic view showing the method for a holographic stereogram with a transmission type hologram.  
     [0088]FIG. 36 is a schematic view showing an illustrative structure of an image reproducing apparatus embodying the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0089] Referring to the drawings, preferred embodiments a first image recording method and an image recording device of the present invention will be explained in detail.  
     [0090] 1. First age Recording Method and Image Recording Device  
     [0091] A first embodiment of an image recording method and image recording device according to the present invention will be hereinafter explained.  
     [0092] 1-1 Schematics of an Image Recording Device  
     [0093] The schematics of a holographic stereogram printer system of a first image recording device embodying the present invention will be explained.  
     [0094]FIG. 6 shows a structure of this holographic stereogram printer system  10 . The holographic stereogram printer system  10  is made up of a data processor  11 , a control computer  12  and a holographic stereogram printer device  13 .  
     [0095] The data processor  11  generates a parallax image series based on image data D 1  for plural image data D 2  of an rendering image (image resulting from rendering). The image data D 1 , outputted by a parallax image string imaging device  14 , is obtained by imaging an object from plural viewing points in the transverse direction, such as by simultaneously imaging by a multi-eye camera or by continuous imaging with a moving camera, while the image data D 2  of a rendering image, outputted by a computer  15 , are formed by sequentially according the parallax in the transverse direction. The data processor  11  then performs pre-set image processing for hologram on each image data D 3  of the parallax image string for transiently recording the processed image data D 3  on a recording medium  16 , such as a memory or a hard disc.  
     [0096] During the subsequent light exposure operation, the data processor  11  sequentially reads out the image data D 4  of the parallax image string recorded on the recording medium  16  and sends out the read-out image data D 5  sequentially to the control computer  12 .  
     [0097] During the light exposure, the control computer  12  controls the driving of a shutter  17  of the holographic stereogram printer device  13 , a liquid crystal display device (LCD)  18  and a printer head, as later explained, based on the image data D 5  of the parallax image string sent from the data processor  11 .  
     [0098] The holographic stereogram printer device  13  has a structure as shown in FIGS. 7A and 7B in which parts or components similar to those of FIG. 6 are depicted by the same reference numerals as those used in FIG. 6. The holographic stereogram printer device  13  is configured for driving the LCD  18  based on the image data D 5  supplied from the control computer  12  for sequentially recording the images corresponding to the image data D 5  as hologram elements on a recording medium for hologram  19  for producing a holographic stereogram.  
     [0099] Specifically, the LCD  18  is driven based on one of image data of image data D 5  supplied for the control computer  12  for displaying an image corresponding to the image data D 5  on the LCD  18 , while the control signal S 1  is sent from the control computer  12  to the shutter  17  for opening it for causing a laser light beam L 1  outgoing from a laser light source  20  via shutter  17 , half mirror  21  and mirror  22  to a spatial filter  23 .  
     [0100] The laser light beam L 1  is enlarged by the spatial filter  23  and a collimator  24  and transmitted through the LCD  18  so as to be converted into a projected light beam corresponding to the image displayed on the LCD  18 . The projecting light is incident on the collimator lens  26  via condenser lens  25  so as to be thereby converged in the transverse direction by the collimator lens  26  to fall on the recording medium for hologram  19  held by a printer head  27 .  
     [0101] The laser light beam Li reflected by the half mirror  21  is incident at an incident position on the recording medium for hologram  19  via a cylindrical lens  28 , a collimator lens  29  and a mirror  30  in this order as a beam at a pre-set angle from the back side of the recording medium for hologram  19  as a reference light.  
     [0102] The light path length for the reference light beam is selected to be equal to the light path length of the laser light beam L 1  transmitted through the half mirror  21  and incident via mirror  22  on the recording medium for hologram  19 . This laser light beam L 1  is referred to herein as an object light beam.  
     [0103] Thus, with the present holographic stereogram printer device  13 , this object light beam (projecting light beam) can be caused to interfere with the reference light beam on a recording surface of the recording medium for hologram  19  whereby the image displayed on the LCD  18  can be recorded as strip-shaped interference fringes on the recording medium for hologram  19 .  
     [0104] Moreover, with the present holographic stereogram printer device  13 , when later the recording of the image comes to a close, the shutter  17  is driven by the control computer  12  to interrupt the laser light beam L 1  outgoing from the laser light source  20 , as the same time as the LCD  18  ceases to be driven. In addition, the printer head  27  is driven under control by the control computer  12  to feed the recording medium for hologram  19  by a length equal to the transverse width of a sole hologram element.  
     [0105] The LCD  18  is then driven under control by the control computer  12  for displaying an image corresponding to the next following portions of the image data D 5 . The shutter  17  then is opened under control by the control computer  12  for recording the image displayed on the LCD  18  in a strip shape on the recording medium for hologram  19 . The above sequence of operations is repeated in succession.  
     [0106] Thus, with the holographic stereogram printer device  13 , the images corresponding to the image data of the supplied parallax image string can be sequentially recorded in a strip-like pattern on the recording medium for hologram  19  to produce a desired holographic stereogram.  
     [0107] The recording medium for hologram  19 , used in the present holographic stereogram printer system, is now explained.  
     [0108] The recording medium for hologram  19  is a so-called film coating type recording medium in which a photopolymer layer  19   b  formed of a photopolymerizable photopolymer is formed on a tape-shaped film base material  19   a  and a cover sheet  19   c  is deposited on the photopolymer layer  19   b,  as shown in FIG. 8. In the present embodiment, a photopolymer layer of ‘OMNI-DEX’, with a refractive index before light exposure of 1.487, manufactured by DU PONT Inc. as a photopolymer layer  19   b  as a photosensitive portion to a thickness of approximately 20 μm.  
     [0109] In the initial state of the photopolymerizable photopolymer, a monomer M is uniformly dispersed in a matrix polymer, as shown in FIG. 9A. If a light beam L 2  of the power of, for example, 10 to 400 mJ/cm 2  is illuminated, the monomer M is polymerized in a light-exposed portion, as shown in FIG. 9B. With progress in polymerization, the monomer M is migrated from ambient portions to cause local variation in the concentration in the monomer M to produce refractive index modulation. The polymerization of the monomer M then comes to a close by illuminating the UV light or the visible light L 3  with the power on the order of 1000 mJ/cm 2  as shown in FIG. 9C. Since the photopolymerizable photopolymer has its refractive index varied with the incident light beam, the interference fringes, brought about by interference between the reference light beam and the object light beam, can be recorded as changes in the refractive index.  
     [0110] The recording medium for hologram  19 , employing the photopolymerizable photopolymer, need not be processed with particular development operations after light exposure. Thus the holographic stereogram printer device  13  employing the recording medium for hologram  19  having its photosensitive portion formed of a photopolymerizable photopolymer can be simplified in structure.  
     [0111] Meanwhile, the first image recording device according to the present invention sequentially records images corresponding to image data of a parallax image string sequentially as strip- or dot-shaped hologram elements by having the object light beam and the reference light beam fall on one and the other surfaces of the recording medium for hologram, respectively. The first image recording device according to the present invention includes an optical component contacted with at least one surface of the recording medium for hologram and liquid supplying means for supplying the liquid to a space between the recording medium for hologram and the optical component.  
     [0112] Thus, with the above-described holographic stereogram printer system  10 , the main point of the present invention resides in a portion of the holographic stereogram printer device  13 , especially a portion thereof in the vicinity of the printer head  27 . Therefore, an illustrative structure of the vicinity of the printer head  27  is explained in detail hereinbelow by way of illustrating an embodiment of the first image recording device according to the present invention.  
     [0113] Since the image recording method according to the present invention is characterized in that, during recording on the recording medium for hologram, an optical component is contacted with at least one surface of the recording medium for hologram, and in that a liquid is interposed between the recording medium for hologram and the optical component, an embodiment of the method of the present invention is explained in connection with the explanation of the operation of the vicinity of the printer head  27 .  
     [0114] 1-2 First Embodiment  
     [0115] With the image recording device according to the present invention, optical components made up of the one-dimensional diffusion plate and the louver film are contacted via a liquid with the object light incident side of the recording medium for hologram  19 . The image recording method according to the present invention produces a holographic stereogram using the above-described image recording device.  
     [0116] For explaining the image recording device according to the present invention, the structure of the vicinity of the printer head  27  of the holographic printer device  13  in the above-described holographic stereogram printer system  10  is explained in detail. In the present embodiment, the printer head  27  is constructed as a printer head  27 - 1 , as shown in FIG. 10.  
     [0117] The printer head  27 - 1  has a mechanism for holding and transporting the recording medium for hologram  19 .  
     [0118] Specifically, the printer head  27 - 1  is configured for rotatably holding a roll  41  with a pre-set torque within a film cartridge  40  loaded in position and for holding the recording medium for hologram  19  drawn out from the film cartridge  40  between the intermittent feed rolls  42  and  43  for thereby positioning the recording medium for hologram  19  between the roll  41  and the intermittent feed roll  42  in a vertical position relative to the object light (laser light beam L 1 ).  
     [0119] The roll  41  and the intermittent feed roll  42  are biased by a torsion coil spring, not shown, in a direction away from each other, whereby a pre-set tensile force is applied on the recording medium for hologram  19  loaded so as to lie across the roll  41  and the intermittent feed roll  42 .  
     [0120] Between the roll  41  and the intermittent feed roll  42  is arranged an optical component  46 , as a rigid member made up of a one-dimensional diffusion plate  44  and a louver film  45 , unified together in a bent state, in meeting with the point of incidence of the object light beam. The optical component  46  is held for movement in a direction towards and away from the recording medium for hologram  19 , as indicate by arrow b by an optical component driving mechanism, not shown.  
     [0121] Before starting the light exposure operation, the optical component driving mechanism drives the optical component  46  based on a control signal S 2  supplied from the control computer  12  for displacing the optical component  46  in a direction towards the recording medium for hologram  19  for pressing the bent distal end of the optical component  46  against the point of incidence of the object light beam on the recording medium for hologram  19  loaded between the roll  41  and the intermittent feed roll  42 .  
     [0122] Thus, with the holographic stereogram printer device  13 , the optical component  46  operates for suppressing micro-sized vibrations of the recording medium for hologram  19  between the roll  41  and the intermittent feed roll  42 , whereby a bright holographic stereogram, that is a holographic stereogram with a higher diffraction efficiency, is produced.  
     [0123] The distal end of the optical component  46  contacted with the recording medium for hologram  19  is curved in a crown shape for protruding both end portions and a center portion thereof, whereby the distal end of the optical component  46  is contacted uniformly with both width-wise ends and with the center portion of the recording medium for hologram  19  for reliably uniformly suppressing micro-sized vibrations of the recording medium for hologram  19  between the roll  41  and the intermittent feed roll  42  along the direction of width of the recording medium for hologram  19 .  
     [0124] In the present embodiment, a sponge  51  impregnated with a liquid is arranged as liquid supplying means upstream of the optical component  46  so as to be in contact with both the optical component  46  and with the recording medium for hologram  19 . The liquid supplied from the sponge  51  is supplied to a cover sheet  19   c  sheathing the photopolymer layer  19   b  so that it is not directly contacted with the photopolymer layer  19   b.    
     [0125] Meanwhile, the sponge  51  is narrower in width than the recording medium for hologram  19  for preventing the liquid from flowing round the back side of the recording medium for hologram  19 . The liquid used for impregnating the sponge  51  is o-xylene.  
     [0126] By arranging the sponge  51 , it becomes possible to supply the liquid to a spacing between the recording medium for hologram  19  and optical component  46  at all times and to have the liquid interposed in the spacing. Since this enables the optical component  46  and the recording medium for hologram  19  to be contacted intimately with each other without void in-between, vibrations of the recording medium for hologram  19  can be suppressed sufficiently.  
     [0127] Moreover, if the liquid is interposed between the recording medium for hologram  19  and the optical component  46 , the recording medium for hologram  19  can be fed intermittently without the necessity of moving the optical component  46  in an opposite direction. This renders it possible to omit the above-mentioned optical component driving mechanism to simplify the structure of the image recording device.  
     [0128] For having the liquid interposed between the recording medium for hologram  19  and the optical component  46 , it is also possible to arrange the recording medium for hologram  19  and the optical component  46  in a liquid. However, since the recording medium for hologram  19  and the optical component  46  are both arranged in air, and the liquid is held by surface tension, it becomes possible to simplify the image recording device in structure, while facilitating the maintenance.  
     [0129] On the other hand, the intermittent feed roll  42  is configured for being rotated in a direction indicated by arrow c based on the force of rotation outputted by a stepping motor, not shown. The stepping motor is configured for rotating the intermittent feed roll  42  a pre-set angle, based on the control signal S 2  supplied from the control computer  12 , each time the light exposure for one image comes to a close. This feeds the recording medium for hologram  19  by one hologram element.  
     [0130] Downstream of the intermittent feed roll  42  in the travel passage of the recording medium for hologram  19  is arranged a UV lamp  47  for extending along the travel passage whereby a UV light beam L 3  of a pre-set power for terminating the diffusion of the monomer M can be illuminated with a pre-set power to the light-exposed portion of the recording medium for hologram  19  forwarded by the intermittent feed roll  42 .  
     [0131] Downstream of the UV lamp  47  in the travel passage of the recording medium for hologram  19  are arranged a rotatably fulcrumed heat roll  48 , a pair of feed-out rolls  49 A,  49 B and a cutter  50 , in this order. The feed-out rolls  49 A,  49 B are arranged for holding the recording medium for hologram  19  in a state of being placed in tight contact by 180° around the outer periphery of the heat roll  48 .  
     [0132] The heat roll  48  is provided with internal heating means, not shown, for maintaining the peripheral surface of the roll at approximately 120° C.  
     [0133] This setting is based on an experiment by which it has been found that, by having an as-exposed photopolymerizable photopolymer (OMNI-DEX) sandwiched between a heating plate temperature-controlled for maintaining a constant temperature of 120° C. and a glass plate pressed from above by a spring pressure and by heating the resulting assembly for five minutes, the refractive index modulation of the same order of magnitude as that obtained in case the assembly is atmosphere-heated at 120° C. for two hours is achieved.  
     [0134] For this reason, the outer diameter of the heat roll  48  is selected so that the time since the recording medium for hologram  19  starts to be contacted with the outer peripheral surface of the heat roll  48  until it is detached therefrom is substantially equal to the time required for the recorded image to become fixed for thereby assuring positive fixation of the image recorded on the recording medium for hologram  19 .  
     [0135] The driving mechanism for the feed-out rolls  49 A,  49 B, referred to hereinafter as a feed-out roll driving mechanism, is configured for rotating the feed-out rolls  49 A,  49 B in synchronism with the intermittent feed roll  42  based on the control signal S 2  outputted by the control computer  12 . This enables the recording medium for hologram  19  to be kept tightly contacted with the peripheral surface of the heat roll  48  without becoming slacked between the intermittent feed roll  42  and the feed-out rolls  49 A,  49 B.  
     [0136] A driving mechanism for the cutter  50  (cutter driving mechanism) , not shown, drives the cutter  50  after a desired image is recorded on the hologram recording medium  19  based on the control signal S 2  supplied from the control computer  12  and entire areas of the hologram recording medium  19  having the image recorded therein are subsequently discharged to outside for severing the discharged portion from the remaining portion of the hologram recording medium  19 . This enables the image-baring portion of the hologram recording medium  19  to be discharged to outside as a sole holographic stereogram.  
     [0137] For explaining the image recording method embodying the present invention, the operation of the holographic stereogram printer device  13  inclusive of the printer head  27 - 1  is explained in detail.  
     [0138] For producing a holographic stereogram, using the above-described holographic stereogram printer device  13 , the hologram recording medium  19  configured as shown in FIG. 8 is coiled around the roll  41  and the resulting assembly is housed within the film cartridge  40 .  
     [0139] The hologram recording medium  19  is then loaded between the roll  41  and the intermittent feed roll  42  and the optical component  46  is set so that its curved distal end will be pressed against the recording medium for hologram  19  with a pre-set pressure. The sponge  51  as liquid supplying means is sufficiently impregnated with a liquid.  
     [0140] Before actually recording the image on the recording medium for hologram  19 , the control signal S 2  is issued from the control computer  12  to the stepping motor of the printer head  27 - 1  and to the feed-out roll mechanism for driving the stepping motor and the feed-out roll mechanism for feeding the recording medium for hologram  19  a distance necessary for establishing the contact between the recording medium for hologram  19  and the optical component  46 .  
     [0141] Since the liquid is supplied to the recording medium for hologram  19  at a position at which the recording medium for hologram  19  starts to be contacted with the recording medium for hologram  19  and the optical component  46  is contacted with the recording medium for hologram  19  already holding the liquid, the liquid can be interposed between the recording medium for hologram  19  and the optical component  46 .  
     [0142] The control computer  12  then sends the image data D 5  corresponding to the respective images of the parallax image string to the LCD  18  for driving the LCD  18  for displaying an image corresponding to the image data D 5 .  
     [0143] The control computer  12  also sends out the control signal S 1  to the shutter  17  for opening it in order to have the laser light L 1  emitted by the laser light source  20  fall on the recording medium for hologram  19  via LCD  18 . The laser light beam L 1 , outgoing from the laser light source  20 , is passed through the shutter  27 , half mirror  22 , spatial filter  23  and the collimator lens  24 , as explained previously, so as to fall on the recording medium for hologram  19  as object light (projecting light). One-half of the laser light beam L 1  radiated from the laser light source  20  to fall on the half-mirror  21  via shutter  17  is reflected to fall as reference light beam on the back side of the recording medium for hologram  19  via cylindrical lens  28 , collimator lens  29  and mirror  30 .  
     [0144] By having the object light beam interfere with the reference light beam on the recording medium for hologram  19  so as to be used for light exposure, an image displayed on the LCD  18  is recorded in a strip shape as interference fringes on the recording medium for hologram  19 .  
     [0145] When the recording of this image comes to a close, the shutter  17  is closed under control by the control computer  12  to interrupt the laser light beam L 1  radiated from the laser light source  20  to stop the driving of the LCD  18 . By sending out the control signal S 2  from the control computer  12  to the stepping motor of the printer head  27 - 1  and to the feed-out roll driving mechanism for driving these two components, the recording medium for hologram  19  is fed by one hologram element. For intermittent feeding of the recording medium for hologram  19 , there is no necessity of spacing the optical component  46  away from the recording medium for hologram  19 .  
     [0146] By repeating the operations of displaying an image corresponding to the image data D 5  on the LCD  18 , opening the shutter  17  for having the object light beam interfere with the reference light beam on the recording medium for hologram  19  for light exposure and feeding the recording medium for hologram  19  by the stepping motor and the feed-out roll driving mechanism by one hologram element, the image data D 5  corresponding to the respective images on the parallax image string supplied from the data processor  11  are sequentially recorded in a strip-like form on the recording medium for hologram  19 .  
     [0147] Downstream of the portion of the printer head  27 - 1  where the recording medium for hologram  19  is exposed to the object light and the reference light, the entire surface of the intermittently fed recording medium for hologram  19  is illuminated by the light beam L 3  from the UV lamp  47 . This completes polymerization of the monomer M in the exposed portion of the photopolymer layer  19   b  of the recording medium for hologram  19 , as shown in FIGS. 9A, 9B and  9 C.  
     [0148] Downstream of the UV lamp  47 , the recording medium for hologram  19  is heated by the heat toll  48 . This increases the refractive index modulation factor of the photopolymer layer  19   b  for fixing the recorded image.  
     [0149] Downstream of the heat roll  48 , the cutter driving mechanism is driven based on the control signal S 2  supplied from the control computer  12  so that the completed holographic stereogram is cut to a desired size by the cutter  50  so as to be discharged to outside.  
     [0150] By continuously supplying the liquid to a space between the recording medium for hologram  19  and the optical component  46  for having the liquid interposed therebetween at all times, for recording a desired image on the recording medium for hologram  19 , the optical component  46  and the recording medium for hologram  19  can be tightly contacted with each other without producing an intervening space thus sufficiently suppressing vibrations of the recording medium for hologram  19 .  
     [0151] By having the liquid interposed between the recording medium for hologram  19  and the optical component  46 , as described above, the recording medium for hologram  19  can be intermittently fed without the necessity of moving the optical component  46  in the opposite direction.  
     [0152] Moreover, the recording medium for hologram  19  and the optical component  46  are arrayed in air and the liquid is held under surface tension, thus facilitating the maintenance.  
     [0153] 1-3 Second Embodiment  
     [0154] In the image recording device of the instant embodiment, in which recording is performed by the edge-lit system, an optical component comprised of a reference light inlet block is contacted via liquid with a reference light incident side of the recording medium for hologram  19 . With the image recording method embodying the present invention, a holographic stereogram is produced using the above-described image recording device.  
     [0155] In carrying out the recording by the edge-lit system, the structure of the holographic stereogram printer system is as explained by referring to FIG. 6, while that of the holographic stereogram printer device is also as explained by referring to FIGS. 7A and 7B except that the angle of incidence of the reference light, for example, is changed from the arrangement shown in FIG. 6.  
     [0156] For illustrating the image recording method embodying the present invention, the structure of the vicinity of the printer head  27  in the holographic stereogram printer device  13  is explained in detail. In the present embodiment, the printer head  27  is constructed as a printer head  27 - 2  shown in FIG. 11.  
     [0157] With the printer head  27 - 2 , similarly to the printer head  27 - 1  shown in FIG. 10, the recording medium for hologram  19  is loaded thereon. The parts and components common to those of the printer head  27 - 1  shown in FIG. 10 are indicated by the same numerals and the corresponding description is omitted for avoiding redundancy.  
     [0158] In the printer head  27 - 2 , the optical component  46  made up of the one-dimensional diffusion plate  44  is arranged at a spacing from the recording medium for hologram  19 . That is, the present one-dimensional diffusion plate  44 , while having the same optical function as that of the printer head  27 - 1  shown in FIG. 10, has no function of retaining the recording medium for hologram  19 .  
     [0159] Meanwhile, with the printer head  27 - 2 , the reference light beam, incident on the recording medium for hologram  19  via a reference light inlet block  52  as later explained, is totally reflected on an interface with air without reaching the one-dimensional diffusion plate  44 . Thus, with the present printer head  27 - 2 , there is no necessity of providing a louver film between the recording medium for hologram  19  and the one-dimensional diffusion plate  44 .  
     [0160] Also, with the present printer head  27 - 2 , the reference light inlet block  52  formed of transparent glass is arranged in register with the point of incidence of the reference light so as to be in contact with the recording medium for hologram  19 . In carrying out the recording by the edge-lit system, the reference light beam falls on an end of the reference light inlet block  52  in order to fall at an acute angle on the surface of the recording medium for hologram  19 . The reference light inlet block  52  herein is formed of glass BK 7  having a refractive index of  1 . 51 .  
     [0161] In the present printer head  27 - 2 , interference fringes are formed on the recording medium for hologram  19  by the object light beam incident substantially at a right angle on the surface of the recording medium for hologram  19  and the reference light beam incident substantially at an acute angle on the surface of the recording medium for hologram  19 .  
     [0162] Moreover, since the reference light inlet block  52  is provided in contact with the recording medium for hologram  19 , micro-sized vibrations of the recording medium for hologram  19  between the roll  41  and the intermittent feed roll  42  can be suppressed for forming a bright holographic stereogram, that is a holographic stereogram having a high diffraction efficiency.  
     [0163] Also, with the present embodiment, a liquid-impregnated sponge  53  is arranged as liquid supply means upstream of the above-mentioned reference light inlet block  52  so as to be in contact with both the reference light inlet block  52  and the recording medium for hologram  19 . Meanwhile, the sponge  53  is narrower in width than the recording medium for hologram  19  for preventing the liquid from flowing round the back side of the recording medium for hologram  19 .  
     [0164] The liquid with which to impregnate the sponge  53  herein is o-xylene having a refractive index enabling index matching of the recording medium for hologram  19  with the reference light inlet block  52 . The conditions for the refractive index enabling index matching will be explained later.  
     [0165] By arranging the sponge  53 , it becomes possible to supply the liquid continuously to a space between the recording medium for hologram  19  and the reference light inlet block  52  in order to have the liquid interposed at all times between the recording medium for hologram  19  and the reference light inlet block  52 . Since this achieves tight contact free of voids between the recording medium for hologram  19  and the reference light inlet block  52 , oscillations of the recording medium for hologram  19  can be suppressed sufficiently.  
     [0166] Since the recording medium for hologram  19  and the reference light inlet block  52  realizes index matching, there is no risk that the reference light passed through the reference light inlet block  52  and incident on the recording medium for hologram  19  be totally reflected within the interior of the reference light inlet block  52 . Thus it becomes possible to fabricate a holographic stereogram of superior image quality.  
     [0167] Moreover, if the liquid is interposed between the recording medium for hologram  19  and the reference light inlet block  52  the recording medium for hologram  19  can be fed intermittently without the necessity of moving the reference light inlet block  52  in an opposite direction. This renders it possible to omit the above-mentioned optical component driving mechanism for displacing the reference light inlet block towards or away from the recording medium for hologram  19  to simplify the structure of the image recording device.  
     [0168] Moreover, if the liquid is interposed between the recording medium for hologram  19  and the reference light inlet block  52 , as described above, the recording medium for hologram  19  and the reference light inlet block  52  may be immersed in a liquid. However, the recording medium for hologram  19  and the optical component  46  are arrayed in air and the liquid is held under surface tension, thus simplifying the structure of the image recording device and facilitating the maintenance.  
     [0169] In the present printer head  27 - 2 , since the structure downstream of the intermittent feed roll  42  is similar to that of the printer head  27 - 1  shown in FIG. 10, the corresponding description is omitted for simplicity.  
     [0170] For explaining the image recording method embodying the present invention, the operation of the holographic stereogram printer device  13  inclusive of the printer head  27  is explained in detail.  
     [0171] For producing a holographic stereogram, using the above-described holographic stereogram printer device  13 , the hologram recording medium  19  configured as shown in FIG. 8 is coiled around the roll  41  and the resulting assembly is housed within the film cartridge  40 .  
     [0172] The hologram recording medium  19  is then loaded between the roll  41  and the intermittent feed roll  42  and the reference light inlet block  52  will be contacted with the recording medium for hologram  19 . The sponge  53  as liquid supplying means is sufficiently impregnated with a liquid.  
     [0173] Before actually recording the image on the recording medium for hologram  19 , the control signal S 2  is issued from the control computer  12  to the stepping motor of the printer head  27 - 2  and to the feed-out roll mechanism for driving the stepping motor and the feed-out roll mechanism for feeding the recording medium for hologram  19  a distance corresponding to the contact between the recording medium for hologram  19  and the reference light inlet block  52 .  
     [0174] Since the liquid is supplied to the recording medium for hologram  19  at a position at which the recording medium for hologram  19  starts to be contacted with the reference light inlet block  52  and the recording medium for hologram  19  is contacted with the recording medium for hologram  19  already holding the liquid, the liquid can be interposed between the recording medium for hologram  19  and the reference light inlet block  52 .  
     [0175] The control computer  12  then sends the image data D 5  corresponding to the respective images of the parallax image string for driving the LCD  18  for displaying an image corresponding to the image data D 5 .  
     [0176] The control computer  12  also sends out the control signal S 1  to the shutter  17  for opening it in order to have the laser light L 1  emitted by the laser light source  20  fall on the recording medium for hologram  19  via LCD  18 . The laser light beam Li, outgoing from the laser light source  20 , is passed through the shutter  17 , half mirror  21 , spatial filter  23  and the collimator lens  24 , as explained previously, to fall on the recording medium for hologram  19  as object light (projecting light). One-half of the laser light beam LI radiated from the laser light source  20  to fall on the half-mirror  21  via shutter  17  is reflected to fall as reference light beam on the back side of the recording medium for hologram  19  via cylindrical lens  28 , collimator lens  29  and mirror  30 .  
     [0177] By having the object lightbeam interfere with the reference light beam on the recording medium for hologram  19  so as to be used for light exposure, an image displayed on the LCD  18  is recorded in a strip-shape as interference fringes on the recording medium for hologram  19 .  
     [0178] When the recording of this image comes to a close, the shutter  17  is closed under control by the control computer  12  to interrupt the laser light beam Li radiated from the laser light source  20  to stop the driving of the LCD  18 . By sending out the control signal S 2  from the control computer  12  to the stepping motor of the printer head  27 - 2  and to the feed-out roll driving mechanism for driving the two components, the recording medium for hologram  19  is fed by one hologram element. For intermittent feeding of the recording medium for hologram  19 , there is no necessity of spacing the reference light inlet block  52  away from the recording medium for hologram  19 .  
     [0179] By repeating the operations of displaying an image corresponding to the image data D 5  on the LCD  18 , opening the shutter  17  for having the object light beam interfere with the reference light beam on the recording medium for hologram  19  for light exposure and feeding the recording medium for hologram  19  by the stepping motor and the feed-out roll driving mechanism by one hologram element, the image data D 5  corresponding to the respective images of the parallax image string supplied from the data processor  11  are sequentially recorded in a strip-like form on the recording medium for hologram  19 .  
     [0180] Downstream of the portion of the printer head  27 - 2  where the recording medium for hologram  19  is exposed to the object light and the reference light, the entire surface of the intermittently fed recording medium for hologram  19  is illuminated by the light beam L 3  from the UV lamp  47 . This completes polymerization of the monomer M in the exposed portion of the photopolymer layer  19   b  of the recording medium for hologram  19 , as shown in FIGS. 9A, 9B and  9 C.  
     [0181] Downstream of the UV lamp  47 , the recording medium for hologram  19  is heated by the heat toll  48 . This increases the refractive index modulation factor of the photopolymer layer  19   b  for fixing the recorded image.  
     [0182] Downstream of the heat roll  48 , the cutter driving mechanism is driven based on the control signal S 2  supplied from the control computer  12  so that the completed holographic stereogram is cut to a desired size by the cutter  50  so as to be discharged to outside.  
     [0183] By continuously supplying the liquid to a space between the recording medium for hologram  19  and the reference light inlet block  52  for having the liquid interposed therebetween at all times, for recording a desired image on the recording medium for hologram  19 , the reference light inlet block  52  and the recording medium for hologram  19  can be tightly contacted with each other without producing an intervening space thus sufficiently suppressing vibrations of the recording medium for hologram  19 .  
     [0184] Moreover, since the liquid supplied to the space between the recording medium for hologram  19  and the reference light inlet block  52  realizes index matching, the reference light beam passed through the reference light inlet block  52  so as to fall on the recording medium for hologram  19  is not totally reflected within the reference light inlet block  52 , thus achieving a holographic stereogram of superior image quality.  
     [0185] By having the liquid interposed between the recording medium for hologram  19  and the optical component  46 , as described above, the recording medium for hologram  19  can be intermittently fed without the necessity of moving the reference light inlet block  52  in the opposite direction.  
     [0186] Moreover, the recording medium for hologram  19  and the optical component  46  are arrayed in air and the liquid is held under surface tension, thus facilitating the maintenance.  
     [0187] Meanwhile, if, in carrying out reproduction by the edge-lit system, an illuminating light inlet block having optical properties similar to those of the reference light inlet block  52  is contacted with the holographic stereogram, and the illuminating light beam is incident on this illuminating light inlet block at the same angle as the angle of incidence of the reference light to the surface of the recording medium for hologram  19 , the illuminating light is diffracted by interference fringes formed on the recording medium for hologram  19 , thus producing the diffracted light similar to the object light for producing a reproduced image.  
     [0188] Thus, for fabricating a transmission type holographic stereogram by the edge-lit system, the reference light beam needs to fall from the object light incident side on the recording medium for hologram. Thus the reference light inlet block is arrayed between the cylindrical lens for collecting the object light and the recording medium for hologram. However, because of spatial constraints, it is extremely difficult to arrange the reference light inlet block between the cylindrical lens and the recording medium for hologram.  
     [0189] On the other hand, with a holographic stereogram printer device  13  having the printer head  27 - 2 , as shown in FIG. 11, since the holographic stereogram of the edge-lit system is fabricated as a reflection type hologram, it is sufficient if the object light is caused to fall on one of the surfaces of the recording medium for hologram  19  and if the reference light is caused to fall on the its opposite surface. Thus it suffices if the cylindrical lens  20  for condensing the object light is arranged on one side of the recording medium for hologram  19  and the reference light inlet block  52  is arranged on the other side thereof in order to construct the optical system with ease in a manner free from spatial limitations.  
     [0190] Meanwhile, the holographic stereogram fabricated as the reflection type hologram reproduces the three-dimensional image by the reflection type hologram. For reproducing the three-dimensional image as the reflection type hologram, a holographic stereogram  62  is bonded to an illuminating light inlet block  61  via liquid  60  and, under this condition, a reproducing illuminating light beam  63  is caused to fall from an end  61   a  of the illuminating light inlet block  61  towards the holographic stereogram  62 . The holographic stereogram  62  is bonded to a surface  61   b  of the illuminating light inlet block  61  remote from a viewer  64 .  
     [0191] In this case, a reproduced image  66  generated by a diffracted light beam  65  diffracted from the holographic stereogram  62  by the reflection mode is observed by the viewer  64 . Thus, when a three-dimensional image is reproduced, a reproduced image  66  appears as if the object were behind the illuminating light inlet block  61  as viewed by the viewer  64 .  
     [0192] It is also possible for the holographic stereogram, fabricated as the reflection type hologram as described above, to reproduce a three-dimensional image as a transmission type hologram.  
     [0193] That is, with a holographic stereogram  72  bonded via a liquid  70  to an illuminating light inlet block  71 , a reproducing illuminating light beam  73  is caused to fall at an end  71   a  of the illuminating light inlet block  71  towards the holographic stereogram  72 . It is noted that the holographic stereogram  72  is bonded to a surface  71   c  of the reproducing light inlet block  71  closer to a viewer  74 .  
     [0194] At this time, a reproduced image  76  generated by a diffracted light beam  75  diffracted from the holographic stereogram  72  with the transmission mode is viewed by the viewer  74 . Thus, if a three-dimensional image is reproduced, a reproduced image  76  appears as if it were located closer to the viewer than if a three-dimensional image is reproduced with the reproducing method shown in FIG. 12. Thus, by reproducing the three-dimensional image shown in FIG. 13, the stereoscopic feeling can be emphasized thus realizing a higher display effect.  
     [0195] Meanwhile, the shape of the illuminating light inlet block  71  need not be parallelepipedic and may be optionally selected on the condition that the angle of incidence of the illuminating reproducing light  73  with respect to the holographic stereogram  72  is coincident with that of the reference light beam incident on the recording medium for hologram  19 .  
     [0196] In the present embodiment, the wavelength of the laser light used for fabricating the holographic stereogram is approximately 532 nm, while the angle the reference light makes with the object light is approximately 75°. The film thickness of a photosensitive portion of the recording medium for hologram  19  is approximately 20 μm, with its refractive index being approximately 1.5. Therefore, the allowance of selection of the wavelength of the holographic stereogram is approximately 50 nm. Thus, for reproducing the holographic stereogram, an LED emitting a light beam having a center wavelength of approximately 525 nm and the wavelength width of approximately 50 nm is desirable as the light source of the reproducing illuminating light  73 . Since the LED has an extremely high light emitting efficiency, it becomes possible to obtain the driving power of the image reproducing device from, for example, a battery, thereby enabling the size and the cost of the device to be lowered.  
     [0197] For reproducing a holographic stereogram as the reflection type, a reproduced image can be usually obtained even if the white light is used as the reproducing illumination because the stereogram has higher wavelength selectivity. Conversely, for regenerating a holographic stereogram as the reflection type, it becomes difficult to reproduce the holographic stereogram with the white light because the wavelength selectivity becomes weaker than if the holographic stereogram is reproduced as the reflection type. Therefore, if a holographic stereogram is reproduced as the transmission type, a light source with a higher color purity is preferably used as a reproducing light source. Specifically, if a LED emitting the light of high color purity is used as a reproducing light source, it becomes possible to obtain a clear reproduced image. The LED also has merits that it s closer in nature to a pont light source and hence is effective to prevent blurring of the reproduced image due to spreading of the light source, and that it scarcely generates heat.  
     [0198] However, the light source for the reproducing illuminating light is not limited to LEDs. If a light source capable of emitting the light of high color purity, such as a semiconductor laser, a reproduced image can be produced in similar manner. The light raised in color purity by a wavelength selective filter or a narrow band reflection mirror may also be used as the reproducing illuminating light.  
     [0199] L-4 Condition for Liquid Interposed between Recording Medium for Hologram and Optical Component  
     [0200] In the above-described first and second embodiments, the optical component  46  made up of a set of the one-dimensional diffusion plate  44  and the louver film  45  is contacted with the recording medium for hologram  19  via liquid and the reference light inlet block  52  is contacted with the recording medium for hologram  19  via liquid, respectively. The conditions for the liquid interposed between the reference light inlet block  52  and the recording medium for hologram  19  are hereinafter explained.  
     [0201] First, the conditions for a liquid interposed between the reference light inlet block  52  and the recording medium for hologram  19  in case of recording by the edge-lit system are explained.  
     [0202] During recording by the edge-lit system, the reference light beam falls at an acute angle on the surface of the recording medium for hologram  19 . Thus it is a frequent occurrence that this reference light beam be totally reflected on an interface between the reference light inlet block  52  and the recording medium for hologram  19  or surface irregularities on the surface of the recording photopolymer layer  19   b  of the recording medium for hologram  19  be presented on the image as stripes looking like wooden grains. It s therefore required of the liquid interposed between the recording medium for hologram  19  and the reference light inlet block  52  to achieve index matching between the recording medium for hologram  19  and the reference light inlet block  52 . That is, the above conditions need to be selected so that no total reflection occurs on the interface between the reference light inlet block  52  and the recording medium for hologram  19  and so that the intensity reflectance (s-components) on each interface is reduced.  
     [0203] Referring to FIG. 14, if a reference light beam  55  falls on an end  52   a  of the reference light inlet block  52  having a refractive index n g  and is transmitted through a liquid  56  having a refractive index n m  to reach the recording medium for hologram  19 , the following equation (1): 
       n   g  sin θ g   =nm  sin θ m   =n   p  sin θ p   (1) 
     [0204] where θ g , θ m  and θ p  are angles of the light beam on the respective interfaces. The conditions under which no total reflection occurs on the respective interfaces are given by the following equations (2) and (3) 
       n   m   &gt;n   g  sin θ g   (2) 
       n   p   &gt;n   m  sin θ m (= n   g  sin θ g )  (3) 
     [0205] Meanwhile, if the photopolymer layer  19   b  of the recording medium for hologram  19  having the refractive index of 1.487, as described above, is used, n P =1.487 is substituted into equation (3) to give n g  by the following equation (4): 
       n   g &lt;1.487/sin θ g   (4) 
     [0206] If θ g =75° or θ g =78°, n g  is given by the following equations (5) and (6): 
     θ g &lt;1.539 for θ g =75°  (5) 
     θ g &lt;1.520 for θ g =78°  (6) 
     [0207] Among materials satisfying the above equations (5) and (6) is the glass BK 7  having the refractive index of 1.51. If the glass BK 7  is used as this reference light inlet block  52 , then n m  can be found by substituting n m =1.51 in the above equation (2).  
     [0208] Therefore, if θ g =75° or θ g =78°, n m  is found by the following equations(7) and (8): 
       n   m &gt;1.458 for θ g =75°  (7) 
       n   m &gt;1.477 for θ g =78°  (8) 
     [0209] That is, for preventing total reflection of the reference light beam  55  on the interface between the reference light inlet block  52  and the recording medium for hologram  19 , it suffices to use a liquid having the refractive index nm satisfying the above equations (7) and (8) as the liquid  56  interposed between the reference light inlet block  52  and the recording medium for hologram  19 .  
     [0210] However, for fabricating the holographic stereogram, it is necessary not only to satisfy the above conditions but also to reduce the intensity reflectance (s-component) on each interface because stronger reflectance on the interface leads to increased light loss and to formation of excess hologram by the reflected light to lower the diffraction efficiency. The conditions for preventing the above-mentioned total reflection applies only for a case in which each interface is planar. With the actual recording medium for hologram  19 , the surface of the photopolymer layer  19  presents inundations to a more or less extent, such that, even if the above conditions are met, total reflection occurs locally to produce uneven portions in the form of wooden grains.  
     [0211] The intensity reflectance (s-components) Rs (g−m)  on the interface between the light inlet block  52  and the liquid  56  and the intensity reflectance (s-components) Rs (m−p)  on the interface between the liquid  56  and the recording medium for hologram  19  are represented by the following equations (9) and (10): 
       Rs   (g−m) =sin 2 (θ g −θ m )/sin 2 (θ g +θ m )  (9) 
       Rs   (m−p) =sin 2 (θ m −θ p )/sin 2 (θ m +θ p )  (10) 
     [0212] Since both Rs (g−m)  and Rs (m−p)  as close to zero as possible are desired, the value obtained by the following equation (11): 
     (1− Rs   (g−m) )×(1 −Rs   (m−p) )  (11) 
     [0213] is desirably as close to unity as possible. 
     [0214] The values of Rs (g−m) , Rs (m−p)  and (1−Rs (g−m) )×(1−Rs (g−m) ) for n p =1.487, n g =1.51, θ g =75° or θ g =78° and for various values of n m  have been found by simulation. The results of the simulation are shown in FIGS. 15 and 16.  
     [0215] The range for which the value of (1−Rs (g−m) )×(1−Rs (m−p) ) becomes 0.9 or larger has been found. The following equations (12), (13) were obtained: 
     1.475 &lt;n   m &lt;1.549 for θ g =75°  (12) 
     1.486 &lt;n   m &lt;1.514 for θ g =78°  (13) 
     [0216] It may be said that, for preventing total reflection on the respective interfaces and for sufficiently reducing the intensity reflectance for satisfying the condition for prevention of total reflection given by the above equations (7) and (8), it suffices to have the liquid  56  with the refractive index nm satisfying the above equations (12) and (13) interposed between the reference light let block  52  and the recording medium for hologram  19 .  
     [0217] Among the liquids  56  satisfying these conditions, there are, for example, ethyl benzene, o-xylene, tetrachloroethylene, toluene, pyridine, pyrrole and mesitylene.  
     [0218] An instance in which there is no necessity for the reference light beam  55  to fall at an acute angle on the surface of the recording medium for hologram  19  is explained.  
     [0219] In order to prevent total reflection on the interface between the reference light inlet block  52  and the liquid  56  and on the interface between the liquid  56  and the recording medium for hologram  19 , for n p =1.487 and θ g =45°, n g  is given by the following equation (14): 
       n   g &gt;2.103  (14) 
     [0220] from the above equation (4).  
     [0221] If n m =1.51 and n g =1.51 and θ g =45° are substituted in the above equation (2), n m  is given by the following equation (15): 
       n   m &gt;1.068  (15) 
     [0222] For finding the condition for suppressing the intensity reflectance to a smaller value, the values of Rs (g−m)  and Rs (m−p)  for various values of n m  with n p =1.487, n g =1.51 and θ g 45° were found by simulation. The results are shown in FIG. 17.  
     [0223] The range of n m  for which the value of (1−Rs (g−m) )×(1−Rs (m−p) ) is 0.9 or larger was found. The range was found to have an extremely large width as given by the following equation (18): 
     1.26 &lt;n   m &lt;1.97  (16) 
     [0224] If the value of (1−Rs (g−m) )×(1−Rs (m−p) ) is set to  0 . 98  or larger, the range of n m  was found to have a broad width as indicated by the equation (17): 
     1.38 &lt;n   m &lt;1.67.  (17) 
     [0225] Since the above equation (17) satisfies the above equation (15) which is the condition for preventing total reflection, it becomes possible to prevent total reflection occurring on the interfaces to suppress the intensity reflectance to a sufficiently small value if a liquid having the refractive index n m  in meeting with the equation (17) is used as the liquid  56  interposed between the reference light let block  52  and the recording medium for hologram  19 .  
     [0226] If the reference light beam  55  is not incident at an acute angle on the surface of the recording medium for hologram  19 , total reflection inherently is less liable to occur, while the intensity reflectance is also small, so that the condition required of the liquid  56  interposed between the reference light let block  52  and the recording medium for hologram  19  become extremely moderate. Therefore, most of known organic solvents become usable as the liquid  56  satisfying the conditions for the refractive index  56 .  
     [0227] In the foregoing, it is assumed that the reference light let block  52  is contacted via liquid  56  with the recording medium for hologram  19 , as shown in FIG. 14, even in cases wherein the reference light beam  55  need not fall at an acute angle to the surface of the recording medium for hologram  19 . However, in the first embodiment, since it is not only the reference light let block  52  but also the optical component  46 , made up of the one-dimensional diffusion plate  44  and the louver film  45 , that are contacted via liquid  56  with the recording medium for hologram  19 , there is produced certain deviation in the range of n m  due to the difference in refractive index between the reference light inlet block  52  and the optical component  46 .  
     [0228] Also, the refractive index of the photopolymer layer  19   b  is adopted as the refractive index n p  of the recording medium for hologram  19 . However, in the recording medium for hologram  19 , actually in use, the photopolymer layer  19   b  is sandwiched between the film base  19   a  and the cover sheet  19   c , without the photopolymer layer  19   b  being in contact with the liquid  56 . If the refractive index of the film base  19   a  or the cover sheet  19   c  is not equal to that of the photopolymer layer  19   b  or of the liquid  56 , there is produced certain deviation in the above range of n m .  
     [0229] 1-5 Modification  
     [0230] Although the first embodiment of the image recording method and apparatus according to the present invention has been described above, the present invention is not limited to these particular embodiments. For example, although sponges  51  or  53  have been used as liquid supplying means, liquid supplying means may be of any suitable structure if it can supply liquid to a space between the recording medium for hologram  19  and the optical component  46  or the reference light inlet block  52 . The liquid supplying means may be designed as a coater employing a die coater or a coater employing a roll for applying a liquid to the recording medium for hologram  19 .  
     [0231] In the second embodiment, since the reference light inlet block  52  is contacted with the recording medium for hologram  19 , the optical component  46  made up of the one-dimensional diffusion plate  44  and the louver film  45  is arranged at a spacing from the recording medium for hologram  19 , both the reference light inlet block  52  and the optical component  46  may be contacted via liquid with the recording medium for hologram  19 .  
     [0232] In the above-described embodiments, the present invention is applied to fabrication of a holographic stereogram having the parallax information only in the transverse direction. The present invention is, however, not limited to these embodiments, but may also be applied to fabrication of a holographic stereogram having the parallax information only in the longitudinal direction or to a holographic stereogram having the parallax information in both the transverse direction and the longitudinal direction.  
     [0233] In addition, although the above embodiments are directed to fabrication of a monochromatic holographic stereogram, the present invention may similarly be applied to fabrication of a colored holographic stereogram. For producing of the colored holographic stereogram, three light beams corresponding to the three prime colors of light may be used as the recording light. For reproducing a colored holographic stereogram recorded using three light beams corresponding to the three prime colors of light, three light sources are provided in an image reproducing device for emitting three prime colors of light so that light beams from the light sources will be illuminated simultaneously on the holographic stereogram as reproducing illuminating light beams. However, if such plural light sources are used, the optical system needs to be constructed so that light beams from the light sources will be parallel to one another. For reproducing the white holographic stereogram, light sources with high color purity are preferably used as the light sources because reproduction with the transmission type hologram suffers from weak wavelength selectivity. This renders it possible to reproduce the colored holographic stereogram clearly even with the transmission type.  
     [0234] In addition, the direction of incidence of the reference light beam, number or types of lenses or the combination thereof may be suitably modified from je above-described arrangement.  
     [0235] 2. Second Image Recording Method and Apparatus  
     [0236] The schematics of a holographic stereogram printer system  100 , as an embodiment of the second image recording device according to the present invention, is hereinafter explained.  
     [0237] 2-1 Schematics of Image Recording Device  
     [0238] The schematics of the holographic stereogram printer system, as an embodiment of the second image recording device according to the present invention, are hereinafter explained.  
     [0239]FIG. 18 shows a structure of the holographic stereogram printer system  100  made up of a data processor  101 , a control computer  102  and a holographic stereogram printer device  103 .  
     [0240] The data processor  101  generates a parallax image string, based on image data D 11  or plural images of image data D 12  for plural rendering images, performs pre-set image processing for hologram on image data D 13  of the parallax image string to produce image data for hologram D 14  and transiently records the image data for hologram D 14  on a recording medium  114 , such as a hard disc. The image data D 11  of plural images are obtained on imaging an object from plural viewing points in the transverse direction, such as on simultaneous imaging by a multi-eye camera or on continuous imaging by a moving camera, while the image data D 12  is produced on sequentially according the parallax in the transverse direction and is outputted by the image data generating computer  112 .  
     [0241] During the subsequent light exposure operation, the data processor  101  sequentially reads out the image data D 14  of the parallax image string recorded on the recording medium  114  to send the read-out image data D 15  sequentially to the control computer  102 .  
     [0242] During light exposure, the control computer  102  driving-controls the shutter  132 , LCD  141  and the printer head, as later explained, of the holographic stereogram printer device  103 , based on the image data D 15  of the parallax image string supplied from the data processor  101 .  
     [0243] The holographic stereogram printer device  103  has the structure shown in FIGS. 19A, 19B in which corresponding parts to those shown in FIG. 18 are denoted by the same reference numerals. Specifically, the holographic stereogram printer device  103  drives the LCD  141  based on the image data D 15  supplied from the above-described control computer  102  for sequentially recording respective images corresponding to the image data D 15  as strip-shaped hologram elements on a recording medium for hologram  130  for fabricating the holographic stereogram. The recording medium for hologram  130  used may be similar to that explained above in connection with the first image recording method and device.  
     [0244] With the present holographic stereogram printer device  103 , the LCD  141  is driven based on one of the image data D 15  supplied from the control computer  102  for displaying an image corresponding to the image data D 15  on the LCD  141 . In addition, a control signal S 11  is sent from the control computer  102  to the shutter  132  for opening the shutter  132  for causing a laser light beam L 11  radiated from the laser light source  131  to fall via shutter  132 , half mirror  133  and mirror  138  on a spatial filter  139 .  
     [0245] This laser light beam L 11  is enlarged in width by a spatial filter  139  so as to be then collimated by a collimator lens  140 . The collimated light beam is transmitted through a LCD  141  so as to be converted into projecting light corresponding to an image displayed on the LCD  141 . The projecting light is then incident on a cylindrical lens  143  so as to be thereby converged in the transverse direction. The converged light beam is then incident on the recording medium for hologram  130  held by a printer head  150 .  
     [0246] At a position directly before incidence of the object light and out of contact with the recording medium for hologram  130  is arranged a one-dimensional diffusion plate  144  exhibiting diffusion characteristics only in the longitudinal direction. This one-dimensional diffusion plate  144  has the function of securing the angle of visibility in an up-and-down direction when the holographic stereogram is reproduced for viewing.  
     [0247] The laser light beam  111 , reflected by the half-mirror  133 , is transmitted through a cylindrical lens  134 , a collimator lens  135  and a mirror  136  in this order so as to fall at a pre-set angle on the reverse surface of the recording medium for hologram  130 . In this case, if the angle of incidence of the reference light beam is increased, surface reflection on the surface of the recording medium for hologram  130  is increased. Thus, a light inlet block  137  is used and the reference light beam is allowed to fall at an end of the block  137 . The light path length of the reference light beam is selected to be substantially equal to that of a laser light beam L 11  transmitted through the half mirror  133  and the mirror  138  to fall on the recording medium for hologram  130 . This laser light beam L 11  is referred to herein as an object light beam.  
     [0248] With the holographic stereogram printer device  103 , this object light beam can be caused to interfere with the reference light beam on a recording surface of the recording medium for hologram  130  so that the image displayed on the LCD 141  can be recorded as strip-shaped interference fringes on the recording medium for hologram  130 .  
     [0249] With the holographic stereogram printer device  103 , the shutter  132  is driven, after the end of recording the image, under control by the control computer  102 , for interrupting the laser light L 11  radiated by the laser light source  131 . The LCD  141  then ceases to be driven and the printer head  150  is driven, under control by the control computer  102 , for feeding the recording medium for hologram  130  by a length equal to the width of a sole hologram element.  
     [0250] The LCD  141  is further driven, under control by the control computer  102 , for displaying an image corresponding to the next following image data D 15 . The shutter  132  is then opened, under control by the control computer  102 , for recording an image displayed on the LCD  141  on the recording medium for hologram  130 . The similar operations are then sequentially carried out in succession.  
     [0251] Thus, in the present holographic stereogram printer device  103 , the images of the respective image data of the supplied parallax image string can be sequentially recorded in the form of strips on the recording medium for hologram  130 , thus producing a desired holographic stereogram.  
     [0252] For recording an image on the recording medium for hologram  130 , two holograms, namely a hologram reproducible as the reflection type and a hologram reproducible as the transmission type, are produced simultaneously. This mechanism is explained by referring to FIG. 20. For simplicity of explanation, it is assumed that the refractive index of the light inlet block  137  is equal to that of the recording medium for hologram  130 .  
     [0253] Referring to FIG. 20A, a light beam L 11 A, incident via light inlet block  137  as reference light beam on the recording medium for hologram  130 , proceeds straightly within the recording medium for hologram  130  so as to be reflected by total reflection on an interface  130   a  with air. A light beam L 11 B returned after total reflection is also used as a reference light beam. The result is that the recording medium for hologram is illuminated by two reference light beams of different proceeding directions. Therefore, if an illuminating light beam corresponding to the light beam L 11 A prior to total reflection is used as the reproducing illuminating light beam for the holographic stereogram, fabricated as described above, the recorded image can be reproduced as the reflection type whereas, if the illuminating light corresponding to the lightbeam L 11 B subsequent to total reflection is used as an illuminating light beam, the recorded image can be reproduced as the transmission type.  
     [0254] Meanwhile, it depends on the refractive index of the recording medium for hologram  130  and on the angle of incidence of the reference light beam whether or not the reference light beam undergoes total reflection on the interface  130   a  between the recording medium for hologram  130  and air. Thus, in the present embodiment, the refractive index of the recording medium for hologram  130  and the angle of incidence of the reference light beam are set in such a manner that the reference light beam undergoes total reflection.  
     [0255] Conversely, if, when the reference light beam is not reflected by total reflection on the interface  130   a  between the recording medium for hologram  130  and air, that is when the reference light beam is transmitted through the recording medium for hologram  130 , the reference light beam is transmitted through the recording medium for hologram  130  falls on the one-dimensional diffusion plate  144  arranged on the object light incident side for the purpose of diffusing the object light beam, the reference light beam is reflected by the one-dimensional diffusion plate  144  so as to be again incident on the recording medium for hologram  130 . Thus the light beam reflected by the one-dimensional diffusion plate  144  so as to be re-incident on the recording medium for hologram  130  represents a noisy component in image recording.  
     [0256] Thus, if the reference light beam is not reflected by total reflection on the interface  130   a  between the recording medium for hologram  130  and air, a louver film  145  needs to be arranged between the one-dimensional diffusion plate  144  and the recording medium for hologram  130  for preventing such re-incidence, as shown in FIG. 21. Thus it becomes possible to prevent the reference light beam from being reflected by the one-dimensional diffusion plate  144  to be re-incident on the recording medium for hologram  130 .  
     [0257] However, since such louver film  145  is arranged in the light path of the object light beam, the object light beam tends to be thereby disturbed to detract from image uniformity or brightness. Conversely, if the reference light beam is reflected by total reflection on the interface  130   a  between the recording medium for hologram  130  and air, the reference light beam is not transmitted through the recording medium for hologram  130 , so that the louver film  145  may be eliminated. Moreover, the optical system may be correspondingly simplified in structure.  
     [0258] For improving sharpness of the recorded image, the one-dimensional diffusion plate  144  is preferably arranged at a position as close to the recording medium for hologram  130  as possible. However, a void is provided between the recording medium for hologram  130  and the one-dimensional diffusion plate  144  for permitting total reflection of the reference light beam on the interface  130   a  between the recording medium for hologram  130  and air. That is, total reflection of the reference light is allowed to occur on the interface  130   a  between the recording medium for hologram  130  and air which is interposed between the one-dimensional diffusion plate  144  and recording medium for hologram  130 .  
     [0259] Meanwhile, a material having the refractive index satisfying the condition of total reflection of the reference light on the interface to the recording medium for hologram  130  may be interposed, in place of air, between the one-dimensional diffusion plate  144  and the recording medium for hologram  130 . That is, the recording medium for hologram  130 , a spacer having a refractive index satisfying the condition for total reflection of the reference light beam and the one-dimensional diffusion plate  144  may be arranged in superposition.  
     [0260] Meanwhile, the second image recording device according to the present invention sequentially records images corresponding to image data of the parallax image string as strip- or dot-shaped hologram elements by causing the object light and the reference light to fall on one and the other surfaces of the recording medium for hologram  130 . To this end, the second image recording device includes an optical component contacted with the reference light incident surface of the recording medium for hologram.  
     [0261] Thus, in the above-described holographic stereogram printer system  100 , the feature of the present invention resides in the structure of the holographic stereogram printer device  103 , in particular the vicinity of the printer head  150 . Thus, an illustrative structure of the vicinity of the printer head  150  is now explained in detail by way of illustrating an embodiment of the image recording device of the present invention.  
     [0262] 2-2 First Embodiment  
     [0263] The image recording device of the present embodiment is configured so that the optical component is contacted in a void-free fashion on the reference light inlet side of the recording medium for hologram  130 . The image recording device of the instant embodiment fabricates a holographic stereogram using the above-described image recording device.  
     [0264] For illustrating the image recording device of the instant embodiment, the structure of the vicinity of the printer head  150  of the holographic stereogram printer device  103  of the above-described holographic stereogram printer system  100  is explained in detail. In the present embodiment, the printer head  150  is configured as a printer head  150 - 1  as shown in FIG. 22.  
     [0265] The printer head  150 - 1  is configured for holding and transporting the recording medium for hologram  130 .  
     [0266] That is, the printer head  150 - 1  is configured for rotatably fulcruming a roll  152  in a film cartridge  151  loaded in position with a pre-set torque and for holding the recording medium for hologram  130  drawn out from the film cartridge  151  between a first intermittent feed roll  153 A and a second intermittent feed roll  153 B.  
     [0267] Between the roll  152  and the intermittent feed rolls  153 A and  153 B, a light inlet block  137 A formed of a transparent rigid material, such as glass, is arranged in contact with the recording medium for hologram  130  on the object light inlet side on the opposite surface to the object light incident side. The light inlet block  137 A is columnar-shaped and is held by a holding mechanism, not shown, for rotation about the shaft as center.  
     [0268] The recording medium for hologram  130  is adapted for being contacted with the light inlet block  137 A between the roll  152  and the intermittent fed rolls  153 A,  153 B. The object light beam is adapted to fall at a right angle on the recording medium for hologram  130  in an area thereof in contact with the light inlet block  137 A.  
     [0269] The recording medium for hologram  130  enclosed within the film cartridge  151  has a cover sheet for protecting the photosensitive portion. That is, the recording medium for hologram  130  is of a sandwiched structure in which the photopolymer layer as the photosensitive portion is sandwiched in an initial state between the base film material and the cover film and is coiled about the roll  152  within the film cartridge  151 . In the printer head  150 - 1 , the cover sheet  130   a  is peeled from the recording medium for hologram  130  so as to be taken up on another roll  154  before the recording medium for hologram  130  led out from the film cartridge  151  is contacted with the light inlet block  137 A, as shown in FIG. 22. The recording medium for hologram  130 , from which the cover sheet  130   a  has been peeled off, is led out towards the light inlet block  137 A, so that the object light incident side and the reference light incident side prove to be a base film material and the photopolymer layer, respectively.  
     [0270] If the recording medium for hologram  130  devoid of the cover sheet is used it is unnecessary to peel the cover sheet off in order to take up the cover sheet on another roll. That is, the recording medium for hologram  130  having the photopolymer layer formed on the base film material may directly be routed to the light inlet block  137 A without peeling the cover film from the recording medium for hologram  130 . Meanwhile, the printer head  150 - 2  shown in FIG. 23 is similar to the printer head  150 - 1  shown in FIG. 22 except the slight difference in the structure of the film cartridge  151 .  
     [0271] The light inlet block  137 A light inlet block  137 A is used for routing the reference light to the recording medium for hologram  130 . The reference light is incident on ne end face of the light inlet block  137 A. This light inlet block is supported by a first thrusting roll  155 A and a second thrusting roll  155 B arranged on the object light incident side and by a third thrusting roll  155 C arranged on the reference light incident side. The first thrusting roll  115 A and the second thrusting roll  115 B are fixed while the third thrusting roll  155 C is movable in the fore-and-aft direction as indicated by arrow d in FIG. 22. The recording medium for hologram  130  is passed through a space between the first thrusting roll  155 A and the light inlet block  130  and into a space between the second thrusting roll  155 B and the light inlet block  130 . In this state, the third thrusting roll  155 C is moved as indicated by arrow d in FIG. 22 and exerts a pressure against the light inlet block  137 A in a direction of thrusting the light inlet block  137 A against the first thrusting roll  155 A and the second thrusting roll  155 B. In this manner, the recording medium for hologram  130  and the light inlet block  137 A are supported with the recording medium for hologram  130  being pressed against the light inlet block  137 A.  
     [0272] That is, the recording medium for hologram  130  is led out of the film cartridge  151  so that the object light inlet side proves to be the base film material and the reference light inlet side, that is the side of the light inlet block  137 A, proves to be the photopolymer layer. The recording medium for hologram  130  is kept in a state in which the photopolymer layer is contacted tightly with the light inlet block  137 A so that there is left no gap between the photopolymer layer and the light inlet block  137 A.  
     [0273] With the printer head  150 - 1 , having the light inlet block  137 A, the light inlet block  137 A is a rigid member, and is positioned by a bearing, not shown, micro-sized vibrations of the light-exposed portions of the recording medium for hologram  130  can be suppressed extremely efficiently. This produces a holographic stereogram of increased brightness, that is of high diffraction efficiency.  
     [0274] The printer head  150 - 1  is provided with a cleaning member  156  in a portion of the light inlet block  137 A not in contact with the recording medium for hologram  130 . The function of this cleaning member  156  is to remove dust and dirt affixed to the lateral side of the rotating light inlet block  137 A. To this end, the cleaning member  156  is formed by s plate member of, for example, urethane rubber, or s soft cloth, and is supported in contact with the lateral side of the light inlet block  137 A.  
     [0275] When the recording medium for hologram  130  is peeled off from the light inlet block  137 A, as when the dust and dirt in air has become affixed to the light inlet block  137 A or recording of the hologram elements has come to a close, part of the recording medium for hologram  130  is occasionally left on the light inlet block  137 A. The cleaning member  156  removes part of the recording medium for hologram  130  left on the light inlet block  137 A or dust and dirt in air out of the light inlet block  137 A. Thus, the light inlet block  137 A is completely cleaned before coming into contact with the recording medium for hologram  130 . That is, with the present printer head  150 - 1 , the light inlet block  137 A and the recording medium for hologram  130  are brought into tight contact with each other after cleaning of the light inlet block  137 A.  
     [0276] The cleaning member  156  is built into the film cartridge  151  so that, when the film cartridge  151  is built into the printer head  150 - 1 , the cleaning member  156  is contacted with the lateral side of the light inlet block  137 A. Thus, when exchanging the film cartridge  151  having enclosed therein the recording medium for hologram  130 , the cleaning member  156  can be exchanged simultaneously to facilitate maintenance.  
     [0277] The first and second intermittent feed rolls  153 A,  153 B are configured for being rotated in a direction shown by arrow e under the force of rotation outputted by a stepping motor, not shown. This stepping motor sequentially rotates the intermittent feed rolls  153 A,  153 B a pre-set angle, under control by a control signal S 12  furnished from the control computer  102  each time light exposure for one image comes to a close. Thus the recording medium for hologram  130  is fed by one hologram element each time light exposure for one image comes to a close.  
     [0278] Downstream of the intermittent feed rolls  153 A,  153 B in the travel passage of the recording medium for hologram  130  is arranged a UV lamp  157  for extending along the travel passage whereby a UV light beam L 13  of a pre-set power for terminating the diffusion of the monomer M is illuminated on the light-exposed portion of the recording medium for hologram  130  forwarded by the intermittent feed rolls  153 A,  153 B.  
     [0279] Downstream of the UV lamp  157  in the travel passage of the recording medium for hologram  130  are arranged a rotatably fulcrumed heat roll  158 , a pair of feed-out rolls  159 A,  159 B and a cutter  160 , in this order. The feed-out rolls  159 A,  159 B are arranged for holding the recording medium for hologram  130  in a state of being tightly placed 180° around the outer periphery of the heat roll  158 .  
     [0280] The heat roll  158  is provided with internal heating means, not shown, for maintaining the peripheral surface of the roll at approximately 120° C. This setting is based on an experiment by which it has been found that, by having as-exposed photopolymerizable photopolymer (OMNI-DEX) sandwiched between a heating plate temperature-controlled for maintaining a constant temperature of 120° and a glass plate pressed from above by a spring pressure and by heating the resulting assembly for five minutes, the refractive index modulation of the same order of magnitude as that obtained in case the assembly is atmosphere-heated at 120° C. for two hours can be achieved.  
     [0281] The outer diameter of the heat roll  158  is selected so that the time since the recording medium for hologram  130  starts to be abutted against the outer peripheral surface of the heat roll  158  until it is detached therefrom is substantially equal to the time required for the recorded image to become fixed for thereby assuring positive fixation of the image recorded on the recording medium for hologram  130  passed through the heat roll  158 .  
     [0282] The driving mechanism for the feed-out rolls  49 A,  49 B, referred to hereinafter as a feed-out roll driving mechanism, is configured for rotating the feed-out rolls  153 A,  153 B in synchronism with the intermittent feed rolls  153 A,  153 B based on the control signal S 12  outputted by the control computer  102  during intermittent feed of the recording medium for hologram  130 . This enables the recording medium for hologram  130  to be kept tightly contacted with the peripheral surface of the heat roll without becoming slacked between the intermittent feed rolls  153 A and  153 B and the feed-out rolls  159 A,  159 B.  
     [0283] A driving mechanism for the cutter  160  (cutter driving mechanism) , not shown, drives the cutter  160 , after a desired image is recorded on the hologram recording medium  130  based on the control signal S 12  supplied from the control computer  102  and entire areas of the hologram recording medium  130  having the image recorded therein are subsequently discharged to outside, for severing the discharged portion from the remaining portion of the hologram recording medium  130 . This enables the image-bearing portion of the hologram recording medium  130  to be discharged to outside as a sole holographic stereogram.  
     [0284] For explaining the image recording method embodying the present invention, the operation of the holographic stereogram printer device  103  inclusive of the printer head  150 - 1  is explained in detail.  
     [0285] For producing a holographic stereogram, using the above-described holographic stereogram printer device  13 , the hologram recording medium  130  is coiled around the roll  152  and the resulting assembly is housed within the film cartridge  151 .  
     [0286] The cover film  130   a  is peeled off from the hologram recording medium  130 . The cover film  130   a , thus peeled off, is taken up on the roll  154 . The portion of the hologram recording medium  130 , from which the cover film  130   a  has been peeled off, that is which has the photopolymer layer formed on a base film thereof, is loaded up to the intermittent feed rolls  155 A,  155 B in a state in which the recording medium  130  is thrust by the first and second rolls  155 A,  155 B in a gap-free manner against the light inlet block  137 A.  
     [0287] The control computer  102  then sends the image data D 15  corresponding to the respective images of the parallax image string for driving the LCD  141  for displaying an image corresponding to the image data D 15 . The control computer  102  also sends out the control signal S 11  to the shutter  132  for opening it in order to cause the laser light L 11  emitted by the laser light source  131  to fall on the recording medium for hologram  130  via LCD  141 . The laser light beam L 11 , outgoing from the laser light source  131 , is passed through the shutter  132 , half mirror  133 , mirror  138 , spatial filter  139  and the collimator lens  140 , as explained previously, to fall on the recording medium for hologram  130  as object light (projecting light). One-half of the laser light beam L 11  radiated from the laser light source  131  to fall on the half-mirror  133  via shutter  132  is reflected by the half mirror  133  to fall as reference light beam on the back side of the recording medium for hologram  130  via cylindrical lens  134 , collimator lens  135  and mirror  136 .  
     [0288] By having the object light beam interfere with the reference light beam on the recording medium for hologram  130  so as to be used for light exposure, an image displayed on the LCD  141  is recorded in a strip-shape as interference fringes on the recording medium for hologram  130 .  
     [0289] When the recording of this image comes to a close, the shutter  132  is closed under control by the control computer  102  to interrupt the laser light beam L 11  radiated from the laser light source  131  to stop the driving of the LCD  141 . By sending out the control signal S 12  from the control computer  102  to the stepping motor of the printer head  150 - 1  and to the feed-out roll driving mechanism for driving these two components, the recording medium for hologram  130  is fed by one hologram element.  
     [0290] The recording medium for hologram  130  is fed without displacing the light inlet block  137 A from the recording medium for hologram  130 , with the recording medium for hologram  130  being kept in tight contact with the light inlet block  137 A. The light inlet block  137 A, while not having its own driving mechanism, can be rotated freely. Thus, if the recording medium for hologram  130  is fed without being displaced away from the light inlet block  137 A, the latter is also rotated with movement of the recording medium for hologram  130 . That is, with the present printer head  150 - 1 , the light inlet block  137 A can be rotated while the recording medium for hologram  130  and the light inlet block  137 A are kept in contact with each other.  
     [0291] By repeating the operations of displaying an image corresponding to the image data D 15  on the LCD  141 , opening the shutter  132  for having the object light beam interfere with the reference light beam on the recording medium for hologram  130  for light exposure and feeding the recording medium for hologram  130  by the stepping motor and the feed-out roll driving mechanism a distance corresponding to one hologram element, the image data D 15  corresponding to the respective images on the parallax image string supplied from the data processor  101  are sequentially recorded in a strip-like form on the recording medium for hologram  130 .  
     [0292] Downstream of the portion of the printer head  150 - 1  where the recording medium for hologram  130  is exposed to the object light and the reference light, the entire surface of the intermittently fed recording medium for hologram  130  is illuminated by the UV light beam L 13  from the UV lamp  157 . This completes polymerization of the monomer M in the exposed portion of the photopolymer layer  19   b  of the recording medium for hologram  130 .  
     [0293] Downstream of the UV lamp  157 , the recording medium for hologram  130  is heated by the heat toll  48 . This increases the refractive index modulation degree of the photopolymer layer for fixing the recorded image. Downstream of the heat roll  158 , the cutter driving mechanism is driven based on the control signal S 12  supplied from the control computer  102  so that the completed holographic stereogram is cut to a desired size by the cutter  160  so as to be discharged to outside.  
     [0294] For recording a desired image on the recording medium for hologram  130 , the recording medium for hologram  130  is contacted with the light inlet block  137 A at the same time as the air is expelled continuously by the thrusting rolls  155 A,  155 B for eliminating voids between the recording medium for hologram  130  and the light inlet block  137 A, for enabling the reference light beam to fall at an acute angle without interposition of, for example, an index matching liquid. Meanwhile, the light inlet block  137 A is a rigid member and has its relative position rigidly fixed with respect to, for example, a casing. Thus, the vibrations of the recording medium for hologram  130 , held in tight contact with the light inlet block  137 A, can be suppressed sufficiently.  
     [0295] Meanwhile, it depends on characteristics of the recording medium for hologram  130 , in particular its hardness or thickness, whether or not the recording medium for hologram  130  can be tightly contacted with the light inlet block  137 A without voids. However, since the photopolymer, as a material for the recording medium for hologram  130 , usually exhibits moderate pliability, the recording medium for hologram  130  can be brought easily into tight contact with the light inlet block  137 A without voids. If ‘OMNI-DEX’ manufactured by DU PONT Inc. is used as a material for a photopolymer layer for the recording medium for hologram  130  and its film thickness is set to approximately 20 μm, the recording medium for hologram  130  could be bonded tightly with the light inlet block  137 A without voids.  
     [0296] 2-3 Second Embodiment  
     [0297] The image recording device of the present embodiment performs edge-lit recording via an index matching liquid and is configured so that a light inlet block is contacted via liquid with the reference light incident side of the recording medium for hologram  130 . The image recording method of the present embodiment fabricates a holographic stereogram using the above image recording device.  
     [0298] Meanwhile, in performing edge-lit recording via an index matching liquid, the structure of the holographic stereogram printer system is as explained with reference to FIG. 18, while the structure of the holographic stereogram printer device is as explained with reference to FIGS. 19A and 19B except for the partially modified light inlet block.  
     [0299] For illustrating an image recording device of the instant embodiment, the structure of the vicinity of the printer head  150  of the holographic stereogram printer device  103  is explained in detail. In the instant embodiment, the printer head  150  is constructed as a printer head  150 - 3  shown in FIG. 24.  
     [0300] The printer head  150 - 3  is designed to load the recording medium for hologram  130  in the same manner as the printer head  150 - 2  shown in FIG. 23. The parts or components similar to those of the printer head  150 - 1  or  150 - 2  are denoted by common numerals and are not described for avoiding redundancy.  
     [0301] With the printer head  150 - 3 , the one-dimensional diffusion plate  144  is arranged at a position spaced away from the recording medium for hologram  130 . Also, with the printer head  150 - 3 , a light inlet block  137 B, formed of transparent glass, is arranged in register with the reference light incident position in contact with the recording medium for hologram  130 . In carrying out recording by the edge-lit system, the reference light beam is caused to fall at an edge portion of the light inlet block  137 B so as to fall at an acute angle on the surface of the recording medium for hologram  130 . For the light inlet block  137 B, glass BK 7  having the refractive index of 1.51 was used.  
     [0302] Thus, on the recording medium for hologram  130 , interference fringes are formed by the object light incident at a right angle on the surface of the recording medium for hologram  130  and the reference light incident thereon at an acute angle.  
     [0303] Since the light inlet block  137 B is arranged in contact with the recording medium for hologram  130 , micro-sized vibrations of the recording medium for hologram  130  between the film cartridge and the intermittent feed rolls  153 A,  153 B can be suppressed for producing a holographic stereogram of higher brightness, that is of higher diffraction efficiency.  
     [0304] In the present embodiment, a sponge  161  impregnated with a liquid is arranged as liquid supplying means upstream of the light inlet block  137 B so as to be in contact with both the light inlet block  137 B and with the recording medium for hologram  130 . The sponge  51  is narrower in width than the recording medium for hologram  130  for preventing the liquid from flowing round the back side of the recording medium for hologram  130 .  
     [0305] The liquid used for impregnating the sponge  51  is o-xylene having the refractive index enabling index matching between the recording medium for hologram  130  and the light inlet block  137 B. The conditions for the liquid interposed between the light inlet block  137 B and the recording medium for hologram  130  are the same as those explained in connection with the first embodiment of the image recording method and device.  
     [0306] By arranging the sponge  161 , it becomes possible to supply the liquid to a spacing between the recording medium for hologram  130  and the light inlet block  137 B at all times in order to have the liquid interposed therein. Since this enables the light inlet block  137 B and the recording medium for hologram  130  to be contacted intimately with each other without voids, vibrations of the recording medium for hologram  130  can be suppressed sufficiently.  
     [0307] Moreover, since the liquid supplied to the space between the recording medium for hologram  130  and the light inlet block  137 B performs index matching, the reference light transmitted through the light inlet block  137 B so as to fall on the recording medium for hologram  130  is not reflected by total reflection within the light inlet block  137 B. The result is the holographic stereogram of superior image quality.  
     [0308] Moreover, if the liquid is interposed between the recording medium for hologram  130  and the light inlet block  137 B, the recording medium for hologram  130  can be fed intermittently without the necessity of moving the light inlet block  137 B in an opposite direction. This renders it possible to omit a driving mechanism for moving the light inlet block  137 B towards and away from the recording medium for hologram  130  to simplify the structure of the image recording device.  
     [0309] For having the liquid interposed between the recording medium for hologram  130  and the light inlet block  137 B, it is also possible to arrange the recording medium for hologram  130  and the light inlet block  137 B in a liquid. However, in the instant embodiment, since the recording medium for hologram  130  and the light inlet block  137 B are both arranged in air and the liquid is held by surface tension, it becomes possible to simplify the image recording device in structure, while facilitating the maintenance.  
     [0310] In the printer head  150 - 3 , since the structure downstream of the intermittent feed rolls  153 A,  153 B is similar to that of the printer head  150 - 1  shown in FIG. 22 and the printer head  150 - 2  shown in FIG. 23, the corresponding description is omitted for avoiding redundancy.  
     [0311] For illustrating the picture recording method according to the present embodiment, the operation of the holographic stereogram printer device having the above-mentioned printer head  150 - 3  is explained in detail.  
     [0312] For producing a holographic stereogram, using the above-described holographic stereogram printer device  103 , the hologram recording medium  130  is coiled around the roll  152  and the resulting assembly is housed within the film cartridge  151 . The hologram recording medium  130  is then loaded between the film cartridge  151  and the intermittent feed rolls  153 A,  153 B and the light inlet block  137 B is set in contact with the recording medium for hologram  130 . The sponge  161  as liquid supplying means is sufficiently impregnated with a liquid.  
     [0313] Before actually recording the image on the recording medium for hologram  130 , the control signal S 12  is issued from the control computer  102  to the stepping motor of the printer head  150 - 3  and to the feed-out roll mechanism for driving the stepping motor and the feed-out roll mechanism for feeding the recording medium for hologram  130  a distance for establishing the contact between the recording medium for hologram  130  and the light inlet block  137 B.  
     [0314] Since the liquid is supplied from the sponge  161  to the recording medium for hologram  130  at a position at which the recording medium for hologram  130  starts to be contacted with the light inlet block  137 B and the light inlet block  137 B is contacted with the recording medium for hologram  130  already holding the liquid, the liquid can be interposed between the recording medium for hologram  130  and the light inlet block  137 B.  
     [0315] The control computer  102  then sends the image data D 15  corresponding to the respective images of the parallax image a string for driving the LCD  141  for displaying an image corresponding to the image data D 15 .  
     [0316] The control computer  102  also sends out the control signal S 12  to the shutter  132  for opening it in order to cause the laser light L 11  emitted by the laser light source  131  to fall on the recording medium for hologram  130  via LCD  141 . The laser light beam L 11 , outgoing from the laser light source  131 , is passed through the shutter  132 , half mirror  133 , mirror  138 , spatial filter  139  and the collimator lens  140 , as explained previously, to fall on the recording medium for hologram  130  as object light (projecting light). One-half of the laser light beam L 11  radiated from the laser light source  131  to fall on the half-mirror  13  via shutter  132  is reflected to fall as reference light beam on the back side of the recording medium for hologram  130  via cylindrical lens  134 , collimator lens  135  and mirror  136 .  
     [0317] By having the object light beam interfere with the reference light beam on the recording medium for hologram  130  so as to be used for light exposure, an image displayed on the LCD  141  is recorded in a strip-shape as interference fringes on the recording medium for hologram  130 .  
     [0318] When the recording of this image comes to a close, the shutter  132  is closed under control by the control computer  102  to interrupt the laser light beam L 11  radiated from the laser light source  131  to stop the driving of the LCD  141 .  
     [0319] By sending out the control signal S 12  from the control computer  102  to the stepping motor of the printer head  150 - 3  and to the feed-out roll driving mechanism for driving the two components, the recording medium for hologram  130  is fed by one hologram element. For intermittent feeding of the recording medium for hologram  130 , there is no necessity of spacing the optical component  137 B away from the recording medium for hologram  130 .  
     [0320] By repeating the operations of displaying an image corresponding to the image data D 15  on the LCD  141 , opening the shutter  132  for having the object light beam interfere with the reference light beam on the recording medium for hologram  130  for light exposure and feeding the recording medium for hologram  130  by the stepping motor and the feed-out roll driving mechanism by one hologram element, the image data D 15  corresponding to the respective images on the parallax image string supplied from the data processor  11  are sequentially recorded in a strip-like form on the recording medium for hologram  130 .  
     [0321] Downstream of the portion of the printer head  150 - 3  where the recording medium for hologram  130  is exposed to the object light and the reference light, the entire surface of the intermittently fed recording medium for hologram  130  is illuminated by the light beam L 13  from the UV lamp  157 . This completes polymerization of the monomer M in the exposed portion of the photopolymer layer of the recording medium for hologram  130 .  
     [0322] Downstream of the UV lamp  157 , the recording medium for hologram  130  is heated by the heat toll  158 . This increases the refractive index modulation degree of the photopolymer layer for fixing the recorded image.  
     [0323] Downstream of the heat roll  48 , the cutter driving mechanism is driven based on the control signal S 12  supplied from the control computer  102  so that the completed holographic stereogram is cut to a desired size by the cutter  50  so as to be discharged to outside.  
     [0324] By continuously supplying the liquid to a space between the recording medium for hologram  130  and the light inlet block  137 B for having the liquid interposed therebetween at all times, for recording a desired image on the recording medium for hologram  130 , the light inlet block  137 B and the recording medium for hologram  130  can be tightly contacted with each other without producing an intervening space thus sufficiently suppressing vibrations of the recording medium for hologram  19 .  
     [0325] Also, since the liquid supplied to the space between the recording medium for hologram  130  and the light inlet block  137 B performs index matching, the reference light beam transmitted through the light inlet block  137 B to fall on the recording medium for hologram  130  is not reflected by total reflection within the light inlet block  137 B thus producing a holographic stereogram of superior image quality.  
     [0326] By having the liquid interposed between the recording medium for hologram  130  and the light inlet block  137 B, as described above, the recording medium for hologram  130  can be intermittently fed without the necessity of moving the light inlet block  137 B in the opposite direction.  
     [0327] Moreover, since the recording medium for hologram  130  and the light inlet block  137 B are both arranged in air and the liquid is held by surface tension, it becomes possible to simplify the image recording device in structure, while facilitating the maintenance.  
     [0328] For carrying out reproduction by the edge-lit system, an illuminating light inlet block having optical properties similar to those of the light inlet block  137 B is contacted with the holographic stereogram and an illuminating light beam is caused to fall on the illuminating light inlet block at the same angle as the angle of incidence of the reference light beam to the surface of the recording medium for hologram  130 , the illuminating light beam is diffracted by the interference fringes formed on the recording medium for hologram  130  to produce a diffracted light beam similar to that produced by the object light beam thus producing a reproduced image.  
     [0329] Thus, for fabricating the transmission type holographic stereogram by the edge-lit system, it is necessary to have the reference light beam fall on the recording medium for hologram via a reference light inlet block from the object light incident side. To this end, the reference light inlet block is arranged between the cylindrical lens configured for converging the object light and the recording medium for hologram. However, because of spatial limitations, it is extremely difficult to arrange the reference light inlet block between the cylindrical lens and the recording medium for hologram. Moreover, the one-dimensional diffusion plate cannot be inserted in position with ease.  
     [0330] Conversely, with the holographic stereogram printer device  103  having the printer head  150 - 3  as shown in FIG. 24, the holographic stereogram of the edge-lit system is fabricated with the reflection type, so that it suffices if the object light and the reference light are caused to fall on one and the opposite surfaces of the recording medium for hologram  130 , respectively. Thus, with the present embodiment, it suffices if the cylindrical lens  143  for converging the object light and the one-dimensional diffusion plate  144  are arranged on one surface of the recording medium for hologram  130  and the reference light inlet block  137 B is arranged on the opposite surface thereof to enable the optical system to be constructed easily without spatial limitations.  
     [0331] As a matter of fact, it is possible with the holographic stereogram, fabricated as the reflection type, to reproduce a three-dimensional image as the reflection type. That is, a holographic stereogram  172  is bonded via a liquid  170  on an illuminating light inlet block  171  and a reproducing illuminating light beam  173  is caused to fall from an end  171   a  of the illuminating light inlet block  171  towards the holographic stereogram  172 . The holographic stereogram  172  is bonded to a surface  171   b  of the illuminating light inlet block  171  remote from a viewer  174 .  
     [0332] In this case, a reproduced image  176  generated by a diffracted light beam  175  diffracted from the holographic stereogram  172  by the reflection mode is observed by the viewer  174 . Thus, when a three-dimensional image is reproduced, a reproduced image  176  appears as if the object were behind the illuminating light inlet block  171  as viewed by the viewer  174 .  
     [0333] It is also possible for the holographic stereogram fabricated as the reflection type as described above, to reproduce a three-dimensional image as a transmission type.  
     [0334] That is, with a holographic stereogram  182  bonded via a liquid  180  to an illuminating light inlet block  181 , a reproducing illuminating light beam  183  is caused to fall at an end  181   a  of the illuminating light inlet block  181  towards the holographic stereogram  182 . It is noted that the holographic stereogram  182  is bonded to a surface  181   c  of the reproducing light inlet block  181  closer to a viewer  184 .  
     [0335] At this time, a reproduced image  186  generated by a diffracted light beam  185  diffracted from the holographic stereogram  182  with the transmission mode is viewed by the viewer  184 . Thus, if a three-dimensional image is reproduced, a reproduced image  186  appears as if it were located closer to the viewer than with the reproducing method shown in FIG. 25. Thus, by reproducing the three-dimensional image shown in FIG. 26, the stereoscopic feeling can be emphasized for improving the display effect.  
     [0336] Meanwhile, the shape of the illuminating light inlet blocks  171 ,  181  need not be parallelepipedic and may be optionally selected on the condition that the angle of incidence of the illuminating reproducing light beams  173 ,  183  with respect to the holographic stereograms  172 ,  182  is coincident with that of the reference light beam incident on the recording medium for hologram  130  during recording.  
     [0337] In the present embodiment, the wavelength of the laser light used for fabricating the holographic stereogram is approximately 523 nm, while the angle e the reference light makes with the object light is approximately 75°. The film thickness of a photosensitive portion of the recording medium for hologram  130  is approximately 20 μm, with its refractive index being approximately 1.5. Therefore, the allowance of selection of the wavelength of the holographic stereogram is approximately 50 nm. Thus, for reproducing the holographic stereogram, an LED emitting a light beam having a center wavelength of approximately 525 nm and the wavelength width of approximately 50 nm is desirable as the light source of the reproducing illuminating light beams  173 ,  183 . Thus it becomes possible to obtain the driving power of the image reproducing device from, for example, a battery, thereby enabling the size and the cost of the device to be lowered.  
     [0338] For reproducing a holographic stereogram as the reflection type, a reproduced image can be usually obtained, even if the white light is used as the reproducing illumination, due to higher wavelength selectivity. Conversely, for regenerating a holographic stereogram as the transmission type, it becomes difficult to reproduce the holographic stereogram with the white light because the wavelength selectivity becomes weaker than if the holographic stereogram is reproduced as the reflection type. Therefore, if a holographic stereogram is reproduced as the transmission type, a light source with a higher color purity is preferably used as a reproducing light source. Specifically, if a LED emitting the light of high color purity is used as a reproducing light source, it becomes possible to compensate for weak wavelength selectivity in order to obtain a clear reproduced image. The LED also has merits that it is closer in nature to a point light source, and hence is effective to prevent the reproduced image from becoming blurred due to spreading of the light source, and that it scarcely generates heat.  
     [0339] However, the light source for the reproducing illuminating light is not limited to LEDs. If a light source capable of emitting the light of high color purity such as a semiconductor laser is used, a reproduced image can be produced in similar manner. The light raised in color purity by a wavelength selective filter or a narrow band reflection mirror may also be used as the reproducing illuminating light.  
     [0340] 2-4 Modification  
     [0341] Although the second embodiment of the image recording method and apparatus according to the present invention has been described above, the present invention is not limited to these particular embodiments. For example, although sponge  161  is used as liquid supplying means, liquid supplying means may be of any suitable structure may be used if it can supply liquid to a space between the recording medium for hologram  130  and the light inlet block  137 B. The liquid supplying means may be designed as a die coater or a coater employing a roll for applying a liquid to the recording medium for hologram  130 .  
     [0342] In the above-described embodiments, the present invention is applied to fabrication of a holographic stereogram having the parallax information only in the transverse direction. The present invention is, however, not limited to these embodiments, but may also be applied to fabrication of a holographic stereogram having the parallax information only in the longitudinal direction or to a holographic stereogram having the parallax information in both the transverse direction and the longitudinal direction.  
     [0343] In addition, although the above embodiments are directed to fabrication of a monochromatic holographic stereogram, the present invention may similarly be applied to fabrication of a colored holographic stereogram. For producing the colored holographic stereogram, three light beams corresponding to the three prime colors of light may be used as the recording light. For reproducing a colored holographic stereogram recorded with use of three light beams corresponding to the three prime colors of light, three light sources are provided in an image reproducing device for emitting three prime colors of light so that light beams from the light sources will be illuminated simultaneously on the holographic stereogram as reproducing illuminating light beams. For reproducing the white holographic stereogram, light sources with high color purity are preferably used as the light sources because reproduction with the transmission type suffers from weak wavelength selectivity. This renders it possible to reproduce the colored holographic stereogram clearly even as the transmission type.  
     [0344] The structure of the light inlet block also is not limited to that shown in the previous embodiments. For example, the object light beam converged and incident on a recording medium for hologram is likely to be transmitted through the recording medium for hologram to be incident on a light inlet block, with the incident light being partially reflected on an opposite lateral surface of the light inlet block to return to the light inlet block. If this occurs, unneeded interference fringes tend to be formed in the light exposed portion to lower the contrast of the reproduced image. Also, if an unexposed portion of the recording medium for hologram is illuminated by light, the unexposed portion is likely to be sensitized before light exposure to render it impossible to effect regular recording. Thus it is possible to form the light inlet block as a cylinder in the hollow inner portion of which is arranged a light absorbing member. The light absorbing member is arranged at a position of not obstructing inlet of the reference light. This eliminates unneeded reflection in the interior of the light inlet block.  
     [0345] It is desirable that air, for example, be not present in a space between the light inlet block and the light absorbing member. Also, the refractive index is desirably close to that of the light absorbing member. Specifically, a black adhesive tape having an adhesive the refractive index of which is close to that of the light absorbing member may be used. Alternatively, clay or a black liquid may be enclosed in a hollow portion of the light inlet block.  
     [0346] The same holds if a square prismatic light inlet block is used in place of the cylindrical block. That is, a black adhesive tape, for example, may be arranged at a position around the light inlet block not obstructing introduction of the reference light beam for preventing unneeded reflection in the light inlet block for improving the image quality.  
     [0347] In an image recording device, a louver film  193  may be arranged between a light inlet block  191  and a recording medium for hologram  192 , as shown in FIGS.  27  or  28 . FIG. 27 shows an instance of a prismatic light inlet block  191 , while FIG. 28 shows an instance of a cylindrical or columnar light inlet block  191 .  
     [0348] The louver film  193  is made up of a large number of louvers, at a pre-set interval from each other, as physical blinds, having an angle of the order of the reference light incident angle relative to its surface, and has characteristics of not passing the light entering the surface at a right angle.  
     [0349] If such louver film  193  is arranged optically between the light inlet block  191  and the recording medium for hologram  192 , without interposition of air or the like, the light radiated through the light inlet block  191  at an acute angle to the recording medium for hologram  192  is transmitted through the louver film  193  to reach the recording medium for hologram  192 , while the object light incident at a right angle on the surface of the louver film  193  is absorbed by the louver film  193  after passing through the recording medium for hologram  192  and hence cannot reach the light inlet block  191 . This eliminates unneeded reflection to improve the image quality.  
     [0350] In addition, the direction of incidence of the reference light or the number, type or combination of lenses in the holographic stereogram printer device is not limited to those of the previous embodiments and may comprise various modifications.  
     [0351] 3. Image Reproducing Method and Device  
     [0352] Illustrative embodiments of the image reproducing method and apparatus according to the present invention will be hereinafter explained.  
     [0353] 3-1 Holographic Stereogram Producing System  
     [0354] First, an illustrative structure of a system for producing a holographic stereogram in which an image is reproduced using an image reproducing method and an image reproducing device according to the present invention is explained. The present embodiment is directed to a holographic stereogram in which plural strip-shaped hologram elements are recorded on a recording medium for generating the parallax information in the transverse direction. However, the present invention is applicable to a holographic stereogram in which plural dot-shaped hologram elements are recorded on a sole recording medium for generating the parallax information in both the transverse and longitudinal directions.  
     [0355] The present holographic stereogram producing system is a system in which a recording medium for hologram, having recorded thereon interference fringes by the object light and the reference light to prove to be a holographic stereogram, or a so-called one-step holographic stereogram, is fabricated by an edge-lit system. The system includes a data processor  201  for processing image data to be recorded, a control computer  202  for controlling the entire system and a holographic stereogram printer device  203 , as shown in FIG. 29.  
     [0356] The data processor  201  generates a parallax image string D 23  based on plural image data D 21  including the parallax information furnished by a parallax image string imaging device  213  having a multi-eye camera and a moving camera and plural image data D 22  including the parallax information generated by an image data generating computer  214 .  
     [0357] The plural image data D 21 , inclusive of the parallax information furnished by a parallax image string imaging device  213 , are image data of plural images obtained on imaging an object from plural viewing points in the transverse direction by simultaneously imaging by a multi-eye camera or by continuous imaging by a moving camera.  
     [0358] The plural image data D 22 , inclusive of the parallax information generated by the image data generating computer  214 , are image data, such as plural CAD (computer aided design) images or CG (computer graphics) images, produced on sequentially according the parallax in the transverse direction.  
     [0359] The data processor  201  performs pre-set image processing for holographic stereogram by an image processing computer on the parallax image string D 23  and records the processed image data D 24  on a storage device  212 , such as a memory or a hard disc.  
     [0360] When recording an image on the recording medium for hologram, the data processor  201  sequentially reads out data on the image basis for sending the image data D 25  to the control computer  202 .  
     [0361] The control computer  202  drives the holographic stereogram printer device  203  for sequentially recording images corresponding to the image data D 25  furnished from the data processor  201  on a recording medium for hologram  230  set in the holographic stereogram printer device  203  as strip-like hologram elements.  
     [0362] At this time, the control computer  202  controls a shutter  232 , a display device  241  and a recording medium feed mechanism provided on the holographic stereogram printer device  203 . That is, the control computer  202  sends out a control signal S 21  to the shutter  232  for controlling the opening/closure of the shutter  232 , while furnishing the image data D 25  to the display device  241  for causing the display device  241  to display an image corresponding to the image data D 25  and for sending out a control signal S 22  to the recording medium feed mechanism for controlling the feed operation of the recording medium for hologram  230  by the recording medium feed mechanism.  
     [0363] By referring to FIGS. 30A and 30B, the holographic stereogram printer device  203  will be explained in detail. FIG. 30A and FIG. 30B view the entire optical system of the holographic stereogram printer device  203  from above, and the portion of the optical system of the holographic stereogram printer device  203  associated with the object light, from a lateral side, respectively.  
     [0364] The holographic stereogram printer device  203  includes a laser light source  231  for radiating a laser light beam of a pre-set wavelength, and a shutter  232  and a half-mirror  233  arranged on the optical axis of the laser light beam L 21  from the laser light source  231 , as shown in FIG. 30A. In the instant embodiment, a laser light source emitting a laser light beam with a wavelength of approximately 532 nm is used as laser light source  231 .  
     [0365] The shutter  232  is controlled by the control computer  202  and is closed or opened when the recording medium for hologram  230  is not exposed to light or is exposed to light, respectively. The half-mirror  233  has the function of separating the laser light beam L 22  transmitted through the shutter  232  into a reference light beam and an object light beam, with the light beam L 23  reflected by the half-mirror  233  and the laser light beam L 24  transmitted through the half-mirror  233  proving to be the reference and object light beams, respectively.  
     [0366] On the optical axis of the light beam L 23  reflected by the half-mirror  233  are arranged, as an optical system for the reference light, a cylindrical lens  234 , a collimator lens  235  for collimating the reference light beam and a total reflection mirror  236  for reflecting the collimated light beam from the collimator lens  235 .  
     [0367] The light reflected by the half-mirror  233  is first diffused by the cylindrical lens  234  and collimated by the collimator lens  235 . The collimated light is then reflected by the total reflection mirror  236  so as to fall on the recording medium for hologram  230 . The recording medium for hologram  230  is arranged in contact with a light inlet block  237  of transparent glass, via a matching liquid, for recording hologram elements by the edge-lit system. The reference light falls on the recording medium for hologram  230  from the side of the light inlet block  237 .  
     [0368] That is, the reference light enters the inside of the light inlet block  237  from the end  237 a of the light inlet block  237  so as to fall with a large angle of incidence on the recording medium for hologram  230  arranged for contacting the light inlet block  237  via matching liquid. In the present embodiment, the wavelength of the laser light used for fabricating the holographic stereogram is approximately 523 nm, while the angle θ the reference light makes with the object light is approximately 75°.  
     [0369] On the optical axis of the light beam L 24  transmitted through the half-mirror  233  are arranged, as an optical system for the object light, a total reflection mirror  238  for reflecting the transmitted light from the half mirror  233 , a spatial filter  239  combined from a convex lens and a pinhole, a collimator lens  240  for collimating the object light, a display device  241  for displaying an image of an object, a diffusion plate  242  for diffusing the light transmitted through the display device  241  and a cylindrical lens  243  for converging the object light on the recording medium for hologram  230 , in this order, as shown in FIGS. 30A and 30B. In addition, a mask  244  having a strip-shaped opening is arranged directly ahead of the recording medium for hologram  230 .  
     [0370] The light beam L 24  transmitted through the half-mirror  233  is reflected by the total reflection mirror  238  and turned into a diffused light from a point light source by the spatial filter  239 . The diffused light is then turned by the collimator lens  240  into collimated light which then falls on the display device  241 . The display device  241  is a transmission type image display device formed by, for example, a liquid crystal display, and is configured for displaying an image corresponding to image data D 25  sent from the control computer  220  under control by the control computer  202 . The light transmitted through the display device  241  is modulated in accordance with the image displayed on the display device  241 . The modulated light is diffused by the diffusion plate  242  to fall on the cylindrical lens  243 . The diffusion plate  242  slightly diffuses the transmitted light from the display device  241  for contributing to improving the image quality of the produced holographic stereogram.  
     [0371] The light transmitted through the display device  241  is converged by the cylindrical lens  243  in the transverse direction. Of the converged light, the light transmitted through the strip-shaped opening of the mask  242  falls as object light on the recording medium for hologram  230 . The object light falls on the recording medium for hologram  230  from the side thereof devoid of the light inlet block  237  so that its optical axis will be perpendicular to the surface of the recording medium for hologram  230 .  
     [0372] In the above optical system, the light path length of the reference light reflected by the half-mirror  233  so as to fall via light inlet block  237  on the recording medium for hologram  230  is selected to be substantially equal to that of the object light transmitted through the half-mirror  233  to fall via display device  241  on the recording medium for hologram  230 . This enhances interference characteristics between the reference light and the object light to enable the production of a holographic stereogram which gives a clearer reproduced image.  
     [0373] In the above-described holographic stereogram printer device  203 , it is desirable to provide a mechanism for dripping an index matching liquid to a space between the light inlet block  237  and the recording medium for hologram  230  for index matching for the recording medium for hologram  230 . Thus, in the present embodiment, a sponge impregnated with the index matching liquid is arranged in the vicinity of the contact portion between the light inlet block  237  and the recording medium for hologram  230 . Thus, each time the recording medium for hologram  230  is fed, the index matching liquid is supplied from the sponge to the space between the light inlet block  237  and the recording medium for hologram  230  for index matching between the light inlet block  237  and the recording medium for hologram  230 .  
     [0374] For fabricating the transmission type holographic stereogram, both the object light and the reference light are caused to fall on one surface of the recording medium for hologram  230 . Thus, for fabricating the transmission type holographic stereogram by the edge-lit system, it is necessary for the reference light to fall via light inlet block on the recording medium for hologram  230  from the object light incident side. Thus the light inlet block is arranged in a space between the object light converging cylindrical lens and the recording medium for hologram. However, because of spatial limitations, it is extremely difficult to arrange the light inlet block between the cylindrical lens and the recording medium for hologram.  
     [0375] Conversely, with the holographic stereogram printer device  203  in which the holographic stereogram of the edge-lit system is fabricated as the reflection type, it suffices if the object light and the reference light are caused to fall on one and the opposite surface of the recording medium for hologram  230 , respectively. Therefore, with the present embodiment, it suffices if the cylindrical lens  243  for converging the object light is arranged on one of the surfaces of the recording medium for hologram  230  and the light inlet block  237  is arranged on the opposite surface thereof to enable the optical system to be constructed easily without spatial constraints The holographic stereogram printer device  203  has a recording medium feed mechanism  250  for intermittently feeding the recording medium for hologram  230  by one hologram element responsive to a control signal from the control computer  202 . This recording medium feed mechanism  250  is designed to feed the recording medium for hologram  230  intermittently under control by the control computer  202 , as will be explained subsequently. For fabricating the holographic stereogram by the holographic stereogram printer device  203 , images corresponding to image data of the parallax image string sequentially recorded, as strip-shaped hologram elements, on the recording medium for hologram  230  set under a pre-determined condition on the recording medium feed mechanism  250 .  
     [0376] Referring to FIGS. 31 and 32A to  32 C, the recording medium for hologram  230  used in the above-described holographic stereogram fabricating system is explained in detail.  
     [0377] The recording medium for hologram  230  is a so-called film coating type recording medium in which a photopolymer layer  230   b  formed of a photopolymerizable photopolymer is formed on a tape-shaped film base material  230   a  and a cover sheet  230   c  is deposited on the photopolymer layer  230   b,  as shown in FIG. 31. In the present embodiment, a photopolymer layer of ‘OMNI-DEX’, manufactured by DU PONT Inc. is formed as a photopolymer layer  19   b  as a photosensitive portion to a thickness of approximately 20 μm.  
     [0378] In the initial state of the photopolymerizable photopolymer, a monomer M is uniformly dispersed in a matrix polymer, as shown in FIG. 32A. If a light beam LA of the power of, for example, 10 to 400 mJ/cm 2  is illuminated, the monomer M is polymerized in a light-exposed portion. With progress in polymerization, the monomer M is migrated from ambient portions to cause local variation in the concentration in the monomer M to produce refractive index modulation. The polymerization of the monomer M then comes to a close by illuminating the UV light or the visible light LB with the power on the order of 1000 mJ/cm 2  as shown in FIG. 32C. Since the photopolymerizable photopolymer has its refractive index changed with the incident light beam, the interference fringes, brought about by interference between the reference light beam and the object light beam, can be recorded as changes in the refractive index.  
     [0379] The recording medium for hologram  230 , employing the photopolymerizable photopolymer, need not be processed with particular development operations after light exposure. Thus the holographic stereogram printer device  203  employing the recording medium for hologram  230  having its photosensitive portion formed of a photopolymerizable photopolymer can be simplified in structure.  
     [0380] The recording medium feed mechanism  250  will be explained in detail by referring to FIG. 33. For. 33  is an enlarged view showing a portion of the recording medium feed mechanism  250  of the holographic stereogram printer device  203 .  
     [0381] Referring to FIG. 33, the recording medium feed mechanism  250  has a roll  251  and an intermittent feed roll  252 . The recording medium for hologram  230  is housed within the film cartridge  253  in the state of being coiled around the roll  251 . The recording medium feed mechanism  250  rotatably fulcrums the roll  251  in the film cartridge  253  loaded in position with a re-set torque and holds the recording medium for hologram  230  pulled out of the film cartridge  253  by the roll  251  and the intermittent feed roll  252 . The recording medium feed mechanism  250  holds the recording medium for hologram  230  so that the surface of the recording medium for hologram  230  will be substantially at right angles to the object light between the roll  251  and the intermittent feed roll  252 . The roll  251  and the intermittent feed roll  252  are biased by a torsion spring in a direction away from each other for applying a pre-set tension on the recording medium for hologram  230  loaded for extending between the roll  251  and the intermittent feed roll  252 .  
     [0382] The intermittent feed roll  252  of the recording medium feed mechanism  250  is connected to a stepping motor, not shown, and is adapted for being rotated in a direction indicated by arrow f in FIG. 33 under the force of rotation of the stepping motor. Based on the control signal S 22  supplied form the control computer  202 , the stepping motor sequentially rotates the intermittent feed roll  252  a pre-set angle corresponding to a hologram element each time the light exposure for one image is terminated. This causes the recording medium for hologram  230  to be fed one hologram element each time an image is exposed.  
     [0383] Downstream of the intermittent feed roll  252  in the travel path of the recording medium for hologram  230  is arranged a UV lamp  254  along the travel path. This UV lamp  254  has the function of competing the polymerization of the monomer M of the recording medium for hologram  230  exposed to light and is adapted for radiating UV light of a pre-set power on the recording medium for hologram  230  fed by the intermittent feed roll  252 .  
     [0384] Downstream of the TJV lamp  254  in the travel path of the recording medium for hologram  230  are sequentially arranged a rotatably fulcrumed heat roll  255 , a pair of feed-out rolls  256 ,  257  and a cutter  258 .  
     [0385] The feed-out rolls  256 ,  257  are adapted for feeding the recording medium for hologram  230  so that the cover sheet side of the recording medium for hologram  230  will be placed over  180 ° in tight contact with the periphery of the heat roll  255 . Based on the control signal S 22  supplied form the control computer  202 , this stepping motor sequentially rotates the feed-out rolls  256 ,  257  in synchronism with the rotation of the intermittent feed roll  252  by a pre-set angle corresponding to one hologram element each time the light exposure for one image is terminated. This enables the recording medium for hologram  230  to be kept tightly contacted with the peripheral surface of the heat roll  255  without becoming slacked between the intermittent feed roll  252  and the feed-out rolls  256 ,  257 .  
     [0386] The heat roll  255  has internal heating means, such as heaters, whereby the peripheral surface of the heat roll  255  is maintained at a temperature of the order of 120° C. This heat roll  255  heats the photopolymer layer  230   b  of the recording medium for hologram  230  fed thereto via cover sheet  230   c  for increasing the refractive index modulation factor of the photopolymer layer  230   b  for fixing the recording image on the recording medium for hologram  230 . The outer diameter of the heat roll  255  is selected so that the time since the recording medium for hologram  230  starts to be contacted with the outer peripheral surface of the heat roll  255  until it is detached therefrom is substantially equal to the time required for fixing the recorded image.  
     [0387] The cutter  258  includes a cutter driving mechanism, not shown, and drives this cuter driving mechanism for severing the recording medium for hologram  230  fed thereto. Based on the control signal S 22 , supplied from the control computer  202 , the cutter driving mechanism drives the cutter  258  when all image-bearing portions of the recording medium for hologram  230  are discharged outwardly from the cutter  258  after the images corresponding to the image data of the parallax image string have been recorded on the recording medium for hologram  230 . This severs the image data bearing portions from the remaining portions so as to be discharged to outside as a sole holographic stereogram.  
     [0388] The operation for fabricating a holographic stereogram by the above-described holographic stereogram producing system hereinafter explained.  
     [0389] For fabricating a holographic stereogram, the control computer  202  drives the display device  241  based on image data D 25  supplied thereto from the data processor  201  for displaying an image on the display device  241 . The control computer  202  then sends out the control signal S 21  to the shutter  232  for opening the shutter  232  for a pre-set time for exposing the recording medium for hologram  230  to light. Of the laser light beam L 22  radiated at this time from the laser light source  231  so as to be transmitted through the shutter  232 , the light beam  123  reflected by the mirror  233  falls at this time as a reference light beam on the recording medium for hologram  230  via light inlet block  237 . The light beam L 24  transmitted through the half-mirror  233  proves to be a projecting light having an image displayed on the display device  241  projected therein. This projecting light is incident as an object light beam on the recording medium for hologram  230 . This records an image displayed on the display device  241  as a strip-shaped hologram element on the recording medium for hologram  230 .  
     [0390] When an image has been recorded on the recording medium for hologram  230 , the control computer  202  sends out the control signal S 22  to the stepping motor connected to the intermittent feed roll  252  and to the stepping motor connected to the feed-out rolls  256 ,  257  for driving these rolls for feeding the recording medium for hologram  230  by one hologram element.  
     [0391] Based on the next image data D 25  supplied from the data processor  201 , the control computer  202  drives the display device  241  for displaying the next image thereon. The above sequence of operations is then repeated for sequentially recording the images corresponding to the image data D 25  from the data processor  201  as strip-shaped hologram elements on the recording medium for hologram  230 . Since the recording medium for hologram  230  is fed by one hologram element from one image to another, the hologram elements are arrayed in succession in the transverse direction. Thus, plural images inclusive of the parallax information in the transverse direction are recorded on the recording medium for hologram  230  for producing a holographic stereogram having the parallax in the transverse direction.  
     [0392] The recording medium for hologram  230 , having the hologram elements recorded thereon as described above, is illuminated by UV light from the UV lamp  254 . This completes polymerization of the monomer M. The recording medium for hologram  230  then is heated by the heat roll  255  for fixing the recorded image.  
     [0393] When the entire image-bearing portion of the recording medium for hologram  230  has been sent out, the control computer  202  sends the control signal S 22  to the cutter driving mechanism for driving it so that the image bearing portion of the recording medium for hologram  230  is severed by the cutter  258  so as to be discharged to outside as a sole holographic stereogram.  
     [0394] The above-described process competes the reflection type holographic stereogram of the edge-lit system having the parallax in the transverse direction.  
     [0395] 3-2 Reproduction of Holographic Stereogram  
     [0396] The reproduction of the holographic stereogram, fabricated as described above, is hereinafter explained.  
     [0397] For reproducing a three-dimensional image from the holographic stereogram as the reflection type, fabricated as described above, a holographic stereogram  262  is bonded to a light inlet block  261  via an index matching liquid  260 , as shown in FIG. 34, and a reproducing illuminating light beam  263  is caused to fall from the end  261   a  of the light inlet block  261  to the holographic stereogram  262 . The holographic stereogram  262  is bonded to a surface  261   b  of the light inlet block  261  remote from the viewer  264 . At this time, a reproduced image  266  generated by a light beam  265  diffracted with the reflection mode from the holographic stereogram  262  is viewed by the viewer  264 . However, when a three-dimensional image is reproduced with the reflection mode in this manner, a reproduced image  266  is reproduced as if the object were behind the illuminating light inlet block  261  as viewed by the viewer  264 .  
     [0398] With the present invention, the three-dimensional image from the reflection type holographic stereogram of the edge-lit system, fabricated as described above, is reproduced as the transmission type. That is, with the reproducing method according to the present invention, after a holographic stereogram  272  is bonded via index matching liquid  270  on the light inlet block  271 , a reproducing illuminating light beam  273  is caused to fall at an end  271   a  of the light inlet block  271  towards the holographic stereogram  272 . The holographic stereogram  272  is bonded to the surface  271   a  of the light inlet block  271  closer to a viewer  274 .  
     [0399] At this time, a reproduced image  276 , generated by the diffracted light beam  275  diffracted with the transmission mode from the holographic stereogram  272 , is viewed by the viewer  274 . If a three-dimensional image is reproduced in this manner, the reproduced image  276  appears as though the object were closer to the viewer than with the reproducing method explained with reference to FIG. 34. Thus, by reproducing the three-dimensional image as shown in FIG. 35, the stereoscopic feeling can be emphasized for improving the display effect.  
     [0400] Referring to FIG. 36, an illustrative structure of an image reproducing device by the transmission type is hereinafter explained.  
     [0401] The image reproducing device is of the edge-lit system and includes a light inlet block  281  on which is bonded a holographic stereogram  280  and a light source  283  for illuminating a reproducing illuminating light beam from an end face  281   a  of the light inlet block  281 . The holographic stereogram  280  of an object is a holographic stereogram of the edge lit system on which the three-dimensional image information is recorded by causing the object light and the reference light to fall on one and the other of the surfaces of the recording medium for hologram, respectively.  
     [0402] The light inlet block  281  is used for introducing the reproducing illuminating light beam  282  into the holographic stereogram  280  and is a parallelepipedic block of transparent glass similar to that used for recording. The holographic stereogram  280  to be reproduced is bonded to the light inlet block  281  via an index matching liquid. It is noted that the holographic stereogram  280  is bonded to a surface  281   b  of the light inlet block  281  closer to a viewer  284 .  
     [0403] Meanwhile, the shape of the illuminating light inlet block  281  need not be parallelepipedic and may be optionally selected on the condition that the angle of incidence of the illuminating reproducing light beam  282  will be incident at a pre-set angle on the holographic stereogram  280 . That is, the light inlet block  281  may be of any suitable shape if, during recording, the angle of incidence of the reference light on the recording medium for hologram during recording is set so as to coincide with that of the reproducing illuminating light  282  for the holographic stereogram  280 .  
     [0404] On the other hand, the light source  283  is an LED arranged for illuminating the reproducing illuminating light beam  282  on the holographic stereogram  280 . Since the LED used as the light source  283  has extremely high light emitting efficiency, a battery, for example, may be used for a practically sufficient time interval. Thus the driving power source of the image reproducing device may be furnished from the battery or the like for reducing the size and cost of the device.  
     [0405] In the above-described image reproducing device, the light source  283  of the reproducing illuminating light beam  282  may be integrated with the light inlet block  281  for simplifying and reducing the size of the optical system. Morever, by integrating the light source  283  of the illuminating light beam  282  with the light inlet block  281 , the angle of incidence of the reproducing illuminating light beam  282  to the holographic stereogram  280  may be perpetually set to an optimum value for producing a high-quality reproduced image  285 .  
     [0406] In the present embodiment, the wavelength of the laser light used for fabricating the holographic stereogram is approximately 523 nm, while the angle θ the reference light makes with the object light is approximately 75°. The film thickness of a photosensitive portion of the recording medium for hologram  230  is approximately 20 μm, with its refractive index being approximately 1.5. Therefore, the allowance of selection of the wavelength of the holographic stereogram is approximately 50 nm. Thus, in the above image reproducing device, a LED emitting the light with the wavelength of approximately 525 nm and the wavelength width of approximately 50 nm is optimum.  
     [0407] For reproducing a three-dimensional image from the holographic stereogram  280  by the above image reproducing device, the holographic stereogram  280  is bonded to the light inlet block  281  via index matching liquid. At this time, the holographic stereogram  280  is arranged on the side of a viewer  284 . The illuminating light beam  282  is illuminated from the light source  283  via light inlet bock  281  to the holographic stereogram  280 . A reproduced image  285  is generated by a light beam  286  diffracted when the illuminating light beam  282  is transmitted through the holographic stereogram  280 . This reproduced image  285  is formed as if the object were at a position closer to the viewer to give an extremely stereoscopic image.  
     [0408] For reproducing a holographic stereogram by the reflection type, a reproduced image can be usually obtained even if the white light is used as the reproducing illumination due to higher wavelength selectivity. Conversely, for regenerating a holographic stereogram by the transmission type, it becomes difficult to reproduce the holographic stereogram with the white light because the wavelength selectivity becomes weaker than if the holographic stereogram is reproduced as the reflection type. Therefore, if a holographic stereogram is reproduced as the transmission type, a light source with a higher color purity is preferably used as a reproducing light source. Specifically, if a LED emitting the light of high color purity is used as a reproducing light source, it becomes possible to compensate for weak wavelength selectivity in order to obtain a clear reproduced image. The LED also has merits that it is closer in nature to a point light source and hence is effective to prevent blurring of the reproduced image  285  due to spreading of the light source, while scarcely generating heat, However, the light source  283  for the reproducing illuminating light  282  is not limited to LEDs. If a light source capable of emitting the light of high color purity such as a semiconductor laser is used, a reproduced image  285  can be produced in similar manner. The light raised in color purity by a wavelength selective filter or a narrow band reflection mirror may also be used as the reproducing illuminating light  282 .  
     [0409] In addition, although the above embodiments are directed to fabrication of a monochromatic holographic stereogram, the present invention may similarly be applied to fabrication of a colored holographic stereogram. For producing the colored holographic stereogram, three light beams corresponding to the three prime colors of light may be used as the recording light. For reproducing a colored holographic stereogram recorded using three light beams corresponding to the three prime colors of light, three light sources are provided in an image reproducing device for emitting three prime colors of light so that light beams from the light sources will be illuminated simultaneously on the holographic stereogram as reproducing illuminating light beams. For reproducing the white holographic stereogram, light sources with high color purity are preferably used as the light sources because reproduction as the transmission type suffers from weak wavelength selectivity. This renders it possible to reproduce the colored holographic stereogram clearly even as the transmission type.  
     [0410] It is seen from above that, with the first image recording method and device according to the present invention, vibrations can be suppressed sufficiently during recording on the recording medium for hologram. This enables accurate recording for improving the diffraction efficiency during reproduction. That is, with the first image recording method and device according to the present invention, a holographic stereogram producing a bright clear reproduced image may be produced. Moreover, the queuing time until attenuation of the vibrations after transfer of the recording medium for hologram may be significantly reduced thus enabling reduction in the process time in fabricating a holographic stereogram by transferring the recording medium for hologram each time a hologram element is recorded. Moreover, the queuing time which elapses after transfer of the recording medium for hologram until attenuation of the oscillations can be significantly reduced thus significantly reducing the queuing time in fabrication of the holographic stereogram by transferring the recording medium for hologram each time a hologram element is recorded. Also, by using, as a liquid interposed between the recording medium for hologram and the optical component, an index matching liquid having an optimized refractive index, recording by the edge-lit system can be carried out in a state in which total reflection of the reference light in the light inlet block is prohibited and the intensity reflectance is suppressed, thus assuring fabrication of the edge-lit holographic stereogram having improved image quality.  
     [0411] With the second image recording method and device according to the present invention, an edge-lit holographic stereogram that can be reproduced as the transmission type can be fabricated easily. Moreover, oscillations during recording on the recording medium for hologram can be suppressed sufficiently. This enables correct recording and improves the diffraction efficiency during reproduction. That is, in the second image recording method and device according to the present invention, an edge-lit holographic stereogram which gives a clear and bright reproduced image can be produced. In addition, the queuing time which elapses since the end of transfer of the recording medium for hologram until attenuation of oscillations again can be reduced significantly, thus significantly shortening the processing time in fabricating the holographic stereogram by transferring the recording medium for hologram each time a hologram element is recorded.  
     [0412] With the image recording method and apparatus according to the present invention, since the edge-lit holographic stereogram recorded as the reflection type having high degree of freedom of the optical system is reproduced as the transmission type, the reproduced image appears as if it were situated close to the viewer. Thus, with the image recording method and device according to the present invention, an extremely stereoscopic image with excellent display effect can be reproduced. That is, in the image recording method and device according to the present invention, a three-dimensional image which appears as if it were situated close to the viewer can be reproduced from en edge-lit holographic stereogram recorded using an optical system having a high degree of freedom and that may be fabricates easily.  
     [0413] Thus, the present invention provides an image recording method and device for recording an image on a holographic stereogram in such a manner as to generate an optimum reproduced image, and an image reproducing method and device for generating an optimum reproduced image from the holographic stereogram.