Patent Publication Number: US-2016223826-A1

Title: Image display device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2015-020648, filed on Feb. 4, 2015; the entire contents of which are incorporated herein by reference. 
     FIELD 
     Embodiments described herein relate generally to an image display device. 
     BACKGROUND 
     Conventionally, there has been known an image display device including two lenticular lenses and an element for reducing crosstalk. 
     It is useful to achieve a novel structure of such an image display device with the lenticular lenses for reducing inconveniency. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exemplary side view schematically illustrating a part of an image display device according to a first embodiment; 
         FIG. 2  is an exemplary side view schematically illustrating a part of an image display device according to a first modification of the first embodiment; 
         FIG. 3  is an exemplary graph of a corresponding relation between a viewing angle and a light amount in an image display device according to the first embodiment; 
         FIG. 4  is an exemplary graph of a corresponding relation between the viewing angle and the light amount as a reference in which the projections are removed from the image display device according to the first embodiment; 
         FIG. 5  is an exemplary exploded perspective view schematically illustrating the image display device according to the first embodiment; 
         FIG. 6  is an exemplary plan view schematically illustrating a lens assembly and a medium on which an image is drawn and a mark is provided in the image display device according to the first embodiment, when the lens assembly is aligned with the medium; 
         FIG. 7  is an exemplary plan view schematically illustrating a lens assembly and a medium on which an image is drawn and a mark is provided in the image display device according to the first embodiment, when the lens assembly is misaligned with respect to the medium before the alignment of the lens assembly with the medium; 
         FIG. 8  is an exemplary side view schematically illustrating the image display device according to the first embodiment, when the lens assembly is aligned with the medium on which the image is drawn and the mark is provided; 
         FIG. 9  is an exemplary exploded perspective view schematically illustrating an image display device according to a second modification of the first embodiment; 
         FIG. 10  is an exemplary exploded perspective view schematically illustrating an aligning member and a medium on which an image is drawn and a mark is provided in an image display device according to a third modification of the first embodiment; 
         FIG. 11  is an exemplary exploded perspective view schematically illustrating an aligning member and a medium on which an image is drawn and a mark is provided in an image display device according to a fourth modification of the first embodiment; 
         FIG. 12  is an exemplary plan view schematically illustrating a mark provided on a medium on which an image is drawn in an image display device according to a second embodiment; 
         FIG. 13  is an exemplary plan view of a part of the mark illustrated in  FIG. 12  viewed through the lens assembly, with the medium and the lens assembly aligned with respect to each other; 
         FIG. 14  is an exemplary plan view of the part of the mark illustrated in  FIG. 12  viewed through the lens assembly, with the medium and the lens assembly misaligned with respect to each other; 
         FIG. 15  is an exemplary plan view providing a wider view of the part of the mark illustrated in  FIG. 12  viewed through the lens assembly, with the medium and the lens assembly misaligned with respect to each other; 
         FIG. 16  is an exemplary plan view schematically illustrating a mark provided on a medium on which an image is drawn in an image display device according to a modification of the second embodiment; 
         FIG. 17  is an exemplary plan view of a part of the mark illustrated in  FIG. 16  viewed through the lens assembly, with the medium and the lens assembly aligned with respect to each other; 
         FIG. 18  is an exemplary plan view of the part of the mark illustrated in  FIG. 16  viewed through the lens assembly, with the medium and the lens assembly misaligned with respect to each other; and 
         FIG. 19  is an exemplary wider plan view the part of the mark illustrated in  FIG. 16  viewed through the lens assembly, with the medium and the lens assembly misaligned with respect to each other. 
     
    
    
     DETAILED DESCRIPTION 
     In general, according to one embodiment, an image display device comprises a first lens member and a second lens member. The first lens member includes a plurality of first cylindrical lenses and a plurality of first projections. The plurality of first cylindrical lenses extend in a first direction and are arranged in a second direction that is perpendicular to the first direction. The plurality of first projections protrude between two adjacent ones of the first cylindrical lenses and extend in the first direction. The second lens member has a same composition as the first lens member, and includes a plurality of second cylindrical lens and a plurality of second projections. The plurality of second cylindrical lens has a same composition as the first cylindrical lenses. The plurality of second projections have a same composition as the first projections. The first lens member and the second lens member are placed on top of each other with each of the first projections inserted between two adjacent ones of the second cylindrical lenses and each of the second projections inserted between two adjacent ones of the first cylindrical lenses. The image display device is configured such that an image is shown through the first lens member and the second lens member. 
     Some exemplary embodiments of the present invention will now be explained. The configuration, the control (technical features), and the actions and the results (effects) achieved by the configuration and the control according to the embodiments below are merely exemplary. The same or like components are included in the embodiments and modifications explained below as examples. Such same or like components are, therefore, assigned with the same or like reference numerals, and redundant explanations thereof are omitted herein. 
     First Embodiment 
     As illustrated in  FIG. 1 , an image display device  1  according to a first embodiment includes a lens assembly  2  including a plurality of lens members arranged on top of each other in a Z direction, and a medium  3 . The Z direction may also be referred to as a thickness direction or a stacking direction. A user looks at an image (not illustrated) on a surface  3   a  of the medium  3  through the lens assembly  2  from the opposite side of the medium  3 . Each of the lens members of the lens assembly  2  is a lenticular lens. Through the lens assembly  2 , a user can view a stereoscopic image on the surface  3   a  processed according to a configuration and characteristics of the lens assembly  2  without wearing any three-dimensional viewing glasses, for example. A working principle and effects of a lenticular lens are known. 
     The lens assembly  2  according to the embodiment also includes some novel features. That is, the lens assembly  2  includes a plurality of lens members  21  and  22 . Each of the lens members  21  and  22  is a lenticular lens. At least two lens members  21  and  22 , which are included as a pair, have at least same lens surfaces  21   a  and  22   a  and are the same components having the same specifications, for example. Compared with the lens assembly of lens members with different lens surfaces, it is able to reduce manufacturing loads and costs for the lens surfaces  21   a  and  22   a , the lens members  21  and  22 , and the lens assembly  2 . More specifically, with use of the lens members  21  and  22  made from a transparent synthetic resin material such as plastic by injection molding, for example, the lens members  21  and  22  can be injection-molded with the same mold (mold tool, die), enabling a reduction in the loads and costs required for creating molds. The lens surfaces  21   a  and  22   a  can also be referred to as convex or concave-convex surfaces, for example. 
     The lens member  21  has a plurality of cylindrical lenses  23  extending in an X direction that is perpendicular to the drawing of  FIG. 1 . Each of the cylindrical lenses  23  has the same or common convex (curved) surface  23   a  extending in the X direction. The cylindrical lenses  23  are disposed adjacent to each other at a constant interval (first interval, first pitch) in a Y direction perpendicular to or intersecting the X direction. The lens member  21  also has a flat surface  21   b  opposite the lens surface  21   a  having the convex surface  23   a . The X direction is an example of a first direction and the Y direction is an example of a second direction. The lens member  21  is an example of the first lens member, and the cylindrical lenses  23  of the lens member  21  are an example of a first cylindrical lens. 
     The lens member  22  is disposed on the opposite side of the medium  3  of the lens member  21 . The lens member  22  is the same component as the lens member  21 . In other words, the lens member  22  includes a plurality of cylindrical lenses  23  having the same specifications as those of the lens member  21 . The lens member  22  also has a lens surface  22   a  having the same specifications as the lens surface  21   a  and a surface  22   b  having the same specifications as the surface  21   b . The lens member  22  is an example of a second lens member, and the cylindrical lenses  23  of the lens member  22  are an example of a second cylindrical lens. 
     The lens members  21  and  22  are integrated with each other, facing opposite directions, that is, in reversed states with respect to each other in the Z direction. The lens members  21  and  22  may be joined by various kinds of joining methods or members. The lens members  21  and  22  are placed on top of each other, with apexes (ridges, generatrixes) of the respective cylindrical lenses  23  abutting on one another. 
     Each of the lens members  21  and  22  also has a plurality of projections  24 , as illustrated in  FIG. 1 . Each of the projections  24  is positioned in a recess  23   b  (at a border) between two adjacent cylindrical lenses  23 ,  23  and protrudes in the protruding direction (Z direction) of the cylindrical lenses  23 . Because the lens members  21  and  22  are placed on top of each other with the apexes of the respective cylindrical lenses  23  abutting on each other, as mentioned above, the projections  24  of the lens member  21  protrude into the corresponding recesses  23   b  on the lens member  22 , and the projections  24  of the lens member  22  protrude into the corresponding recesses  23   b  on the lens member  21 . The projections  24  also extend as a wall in the X direction perpendicular to the drawing. 
     At least the lens surfaces  21   a  and  22   a  of the lens members  21  and  22 , that is, the portions including the cylindrical lenses  23  and the projections  24  are configured to have the same composition (specifications, shapes, or characteristics), as mentioned above. Therefore, it is necessary for the projections  24  to be arranged not to overlap each other in the Z direction while the lens members  21  and  22  are placed on top of each other with the lens surfaces  21   a  and  22   a  facing each other. In view of this, in the example illustrated in  FIG. 1 , the projections  24  are positioned in every other recess  23   b  between the two adjacent cylindrical lenses  23  of the lens member  21 , and the projections  24  are positioned in every other recess  23   b  between the two adjacent cylindrical lenses  23  of the lens member  22 . Thereby, the lens assembly  2  in which the projections  24  of the lens member  21  and the projections  24  of the lens member  22  are provided alternately in the Y direction can be attained. Arrangements of the projections  24  should not be, however, limited to the arrangements explained above. A constant number n (n≧2, n=2 in  FIG. 2 ) of recesses  23   b  in which the projections  24  are provided and, and a constant number n of the recesses  23   b  in which no projections  24  are provided can be arranged in an alternating manner, as illustrated in  FIG. 2 , corresponding to a first modification of the first embodiment, for example. As another example, the projections  24  can be provided in all of the recesses  23   b  on one side from the center in the Y direction, although not illustrated. In this manner, the lens members  21  and  22  can be placed on top of each other without the projections  24  of the lens member  21  interfering with the projections  24  of the lens member  22 . 
     As apparent from  FIG. 1 , tips  24   a  of the projections  24  of the lens member  21  are inserted into the corresponding recesses  23   b  of the lens member  22 , and the tips  24   a  of the projections  24  of the lens member  22  are inserted into the corresponding recesses  23   b  of the lens member  21 . The lens members  21  and  22  are configured in such a manner that the ridges of the cylindrical lenses  23  are brought into contact with the ridges of the corresponding cylindrical lenses  23  with minute gaps of more than zero between the tips  24   a  and the corresponding recesses  23   b . The tips  24   a  each have a curved surface in this example but should not be limited thereto. 
     These projections  24  also serve as light shields or light scatters. The light is blocked or scattered by the projections  24 . By the projections  24 , the light from one of the cylindrical lenses  23  of the lens member  21  can be prevented from being incident on a non-opposing cylindrical lens  23  of the lens member  22  adjacent to the opposing cylindrical lens  23  on which the light is supposed to be incident, and from becoming a noise component (crosstalk), as indicated in the long dashed double-short dashed line N in  FIG. 1 .  FIG. 3  is an exemplary graph of a corresponding relation between a viewing angle (an angle with respect to the Z direction around the X direction) and the light amount in the image display device  1  provided with the projections  24  according to the embodiment.  FIG. 4  is an exemplary graph of a corresponding relation between the viewing angle and the light amount in an image display device  1  with no projections for comparison. It can be understood from  FIGS. 3 and 4  that noise components CT (crosstalk) are reduced in the embodiment illustrated in  FIG. 3  from those in the comparative example illustrated in  FIG. 4 . The surfaces of the projections  24  may be formed more coarsely than the surfaces of the cylindrical lenses  23 . The coarse surfaces of the projections  24  more easily scatter light. To roughen the surfaces of the projections  24 , the cavities of the mold of the lens members  21  and  22  corresponding to the projections  24  may be subjected to surface roughening such as sand blast. 
     In the first embodiment, the projections  24  are also used to align the lens members  21  and  22  in the Y direction. In other words, the tips  24   a  of the projections  24  from one of the lens members  21  and  22  are inserted into the recesses  23   b  of the other. Because the tips  24   a  of the projections  24  hook onto the cylindrical lenses  23  on both sides of the corresponding recesses  23   b  in the Y direction, Y-directional movements of the lens members  21  and  22  are suppressed, and the recesses  23   b  of the lens members  21  are ensured to face the recesses  23   b  of the lens members  22  in the Z direction. Thus, the projections  24  serve as an aligner for the lens members  21  and  22  at least in the Y direction. The projections  24  can also serve as an aligner in the Z-direction. The cylindrical lenses  23  of the lens member  21  may or may not contact with the cylindrical lenses  23  of the lens member  22 . 
     The medium  3  may be directly attached to the lens assembly  2  by adhering or with a coupler, for example, or may be supported or mounted at an aligned position on another member such as a case fixed to or supporting the lens assembly  2 . An example of the medium  3  is a sheet of paper on which an image (not illustrated) is printed. 
     As illustrated in  FIGS. 5 and 6 , the lens assembly  2  and the medium  3  are provided with marks  4  and  5  for aligning the lens assembly  2  and the medium  3  at least in the Y direction among the X direction and the Y direction. One of the lens assembly  2  and the medium  3  (the medium  3  in the embodiment) is provided with three marks  4  ( 4 L,  4 C, and  4 R), and the other (the lens assembly  2  in the embodiment) is provided with one mark  5 . The marks  4 ,  5  extend as a strip (segment) in the X direction in which the cylindrical lenses  23  extend. The three marks  4 L,  4 C, and  4 R are provided at an equal interval. The interval of the marks  4 L,  4 C, and  4 R can be appropriately set. For example, the interval of the marks  4 L and  4 R can be set to substantially coincide with the interval between the two eyes of a person. These marks  4 ,  5  can be provided on the medium  3  separately from a main image and be covered with a case (not illustrated) of the image display device  1 . 
     In the example illustrated in  FIGS. 5 and 6 , the lens assembly  2  is aligned with the medium  3  (image) with the center mark  4 C of the three marks  4  of the medium  3  placed on the mark  5  of the lens assembly  2  in the Z direction. To begin with, a user places the lens assembly  2  on top of the medium  3  in the Z direction in such a manner that a part (e.g., approximately a half) of the mark  4  on the medium  3  is hidden by an end  2   a  of the lens assembly  2  and the other part (e.g., approximately a remaining half) is exposed from the end  2   a . The user then finds a position where the mark  4 C becomes continuous with the mark  5  in the length direction(X direction), as illustrated in  FIG. 6 , while moving at least one of the lens assembly  2  and the medium  3 . The user then fixes the lens assembly  2  and the medium  3  at their aligned positions illustrated in  FIG. 6  by attaching the medium  3  to the lens assembly  2  with an adhesive tape or by coupling the medium  3  to the lens assembly  2  with a coupler such as a pin, for example. 
       FIG. 8  is a side view of the lens assembly  2  and the medium  3  that are aligned with each other. In the embodiment, the marks  4 ,  5  are designed so that, while the lens assembly  2  and the medium  3  are in alignment with each other as illustrated in  FIG. 8 , the mark  4 C, the recess  23   b , and the corresponding projection  24  lie over one another in the Z direction and the marks  4 L and  4 R lie over the respective apexes of the cylindrical lenses  23  in the Z direction. 
     Therefore, at the aligned positions, the widths of images  41 L and  41 R of the marks  4 L and  4 R which the user views through the lens assembly  2  are wider than the widths of the marks  4 L and  4 R which the user directly views without the lens assembly  2 , as illustrated in  FIG. 6 . Further, at the aligned positions an optical path is largely refracted in the recess  23   b  between the two cylindrical lenses  23  since the mark  4   c  lies over the recess  23   b  in the Z direction, so that an image  41 C of the mark  4 C through the lens assembly  2  becomes invisible (see  FIG. 7 ). However, the part of the mark  4 C not hidden behind the end  2   a  of the lens assembly  2  is linearly aligned with the mark  5  of the lens assembly  2  in the X direction. The cylindrical lenses  23  are an example of a lens unit. The marks  4 L and  4 R are examples of a first mark and the mark  4 C is an example of a second mark. 
     Meanwhile, the mark  40  may be designed so that at the misaligned positions the image  41 C thereof through the lens assembly  2  appears somewhat smaller in width or thinner, for example, as illustrated in  FIG. 7 , by adjusting a relative position of the mark  40  to the eyes, the width (size) of the mark  4 C, and the specifications of the lens assembly  2  appropriately. In  FIG. 7 , for the sake of better understanding, the misalignment of the lens assembly  2  and the medium  3  is exaggeratingly illustrated from an actual misalignment. 
     By contrast, at the aligned positions as explained above with reference to  FIG. 6 , because of the large refraction by the recess  23   b , the image of the mark  40  becomes invisible through the lens assembly  2 . In other words, according to the embodiment, the mark  4 C and the lens assembly  2  can be configured in such a manner that, while the lens assembly  2  and the medium  3  are moved from the misaligned positions in  FIG. 7  to the aligned positions in  FIG. 6 , the visible image  41 C of the mark  40  through the lens assembly  2  becomes invisible, that is, the image  41 C disappears. 
     As for the marks  4 L and  4 R and their images  41 L and  41 R through the lens assembly  2 , while the lens assembly  2  and the medium  3  are moved from the misaligned positions in  FIG. 7  to the aligned positions in  FIG. 6 , the visible marks  41 , and  4 R not hidden by the lens assembly  2  are moved from the misaligned positions in the Y direction to the linearly aligned positions in the X direction. Therefore, according to the embodiment, the lens assembly  2  and the medium  3  can be more precisely aligned in reference to the marks  4 L and  4 R and the images  41 L and  41 R and the mark  5  after generally aligned in reference to the marks  4 C and  5 , for example. 
     As explained above, in the embodiment, the parts of the two lens members  21  and  22  (the first lens member and the second lens member) including at least the lens surfaces  21   a  and  22   a , that is, the cylindrical lenses  23  and the projections  24  are designed to have the same composition (specifications) in the lens assembly  2 . Therefore, manufacturing loads and costs for the lens assembly  2  can be reduced more easily, compared with, for example, a lens assembly including a combination of lens members with different compositions (specifications). Furthermore, in the embodiment, the projections  24  facilitate the alignment of the two lens members  21  and  22  and function to suppress crosstalk as well. Therefore, the image display device  1  can be simplified in structure and reduced in size, compared with an image display device having separate components for alignment and crosstalk suppression, for example. 
     Furthermore, in the embodiment, the visually or optically enlarged images  41 L and  41 R t of the marks  4 L and  4 R (first mark) through the cylindrical lenses  23  (lens unit) are used to align the lens assembly  2  (lens members  21  and  22 ) and the medium  3  (the image provided on the medium  3 ). This can facilitate the alignment and realize more precise alignment, for example. 
     Furthermore, in the embodiment, the cylindrical lens  23  is used as the lens unit for enlarging the marks  4  for the alignment. Because the cylindrical lens  23  can also be used as the lens unit, the image display device  1  can be further simplified and downsized advantageously, for example, with the one including the cylindrical lens  23  and the lens unit separately. 
     Furthermore, in the embodiment, the lens assembly  2  (lens members  21  and  22 ) and the medium  3  (image) become aligned with each other in reference to the marks  4 L and  4 R and the visually enlarged images  41 L and  41 R t of the marks  4 L and  4 R through the lens assembly  2 . Therefore, the manufacturing loads and costs for providing the lens assembly  2  with the marks  5  for the alignment can be reduced, as an example. 
     Furthermore, in the embodiment, the lens assembly  2  (lens members  21  and  22 ) and the medium  3  (image) become aligned with respect to each other at a position where at least a part of the mark  4 C (second mark) becomes invisible, overlapping with the recess  23   b  (border). By the disappearance of the image  41 C of the mark  4 C indicating that the lens assembly  2  and the medium  3  are moved from the misaligned positions to the aligned positions, a user can more easily recognize the alignment of the lens assembly  2  and the medium  3 , for example. Because the projections  24  (first projections, second projections) are provided in the recesses  23   b , the mark  4 C may be positioned to overlap with the projection  24 . 
     Furthermore, a lens unit  6  for visually enlarging the mark  4  may be provided separately from the cylindrical lens  23 , as in the modification illustrated in  FIGS. 9 to 11 . In the example illustrated in  FIG. 9 , the lens unit  6  is provided at an end (a corner, a side, or a periphery) of the lens assembly  2  that is separated from the cylindrical lenses  23 . In the example illustrated in  FIGS. 10 and 11 , the lens unit  6  is provided on a different aligning member  7  from the lens assembly  2  (not illustrated in  FIGS. 10, 11 ). In the example illustrated in  FIGS. 9 to 11 , the lens assembly  2  can be aligned with the medium  3  using the marks  5  and a visually enlarged image (not illustrated), by the lens unit  6 , of the mark  4  on the medium  3  for displaying an image (not illustrated). Furthermore, the mark  4  and a visually enlarged image of the mark  4  through the lens unit  6  may be used for the alignment. Furthermore, at least one of the marks  4 ,  5  may be linear, as illustrated in  FIGS. 9 and 10 , or may have a cross shape, as illustrated in  FIGS. 9 to 11 . Furthermore, with the cross-shaped marks  4 ,  5  or with the marks  4 ,  5  positioned away from each other in the X direction, the lens assembly  2  can be also aligned with the medium  3  (image) in the X direction. Furthermore, the lens unit  6  and the marks  4 ,  5  may be covered with a case (not illustrated) of the image display device  1 , for example. 
     Furthermore, in the example illustrated in  FIGS. 10 and 11 , the lens assembly  2  and the medium  3  (the image on the medium  3 ) are aligned with respect to each other indirectly via the aligning member  7 . Specifically, while the medium  3  and the aligning member  7  are in alignment with each other using the marks  4 ,  5 , the medium  3  is cut along an edge  7   a  (end) of the aligning member  7  with a cutter (not illustrated), for example. The cutting line CL is indicated by an alternate long and short dash line in  FIGS. 10 and 11 . In this case, by aligning a cut edge  3   b  (end) of the medium  3  with an end of the lens assembly  2  (not illustrated) at least in the Y direction, for example, the lens assembly  2  and the image become aligned with each other. Furthermore, for example, by aligning a case (not illustrated) of the image display device  1  with the lens assembly  2  at least in the Y direction and by allowing a wall (not illustrated) of the case to hit the edge  3   b  in the Y direction, the lens assembly  2  and the image can be aligned at least in the Y direction. In the example illustrated in  FIGS. 10 and 11 , with no necessity to provide the lens unit  6  in the lens assembly  2 , for example, the manufacturing loads and costs for the lens assembly  2  can be reduced, and the lens assembly  2  can be further simplified and downsized. 
     Second Embodiment 
     A second embodiment includes the same configuration as that of the first embodiment, therefore, can attain the same effects and results as those of the first embodiment. The mark  4 A on the medium  3  according to the second embodiment is, however, differently configured from that according to the first embodiment. Specifically, as illustrated in  FIG. 12 , the mark  4 A includes a plurality of lines  4   a  arranged with an interval in the Y direction and extending in the X direction. The mark  4 A also includes a plurality of patterns P 1  and P 2  consisting of lines  4   a  provided at different intervals (pitches). The intervals between the lines  4   a  in the pattern P 1  and in the pattern P 2  are slightly different. The pattern P 1  is positioned on one side and the pattern P 2  is positioned on the other side in the X direction. When “d” denotes the number of dots in an image corresponding to the width of one cylindrical lens  23  in the Y direction, that is, the width of the cylindrical lens  23  in the Y direction, the interval between the lines  4   a  in the pattern P 1  is set to d+m (dots) (where “m” denotes an integer equal to or greater than one), and the interval between the lines  4   a  in the pattern P 2  is set to d-m (dots), for example. In the example illustrated in  FIG. 12 , a line  4   b  thicker than the other lines  4   a  and extending in the X direction is provided at the center in the Y direction. The pattern P 1  is an example of a first area and the pattern P 2  is an example of a second area. The interval between the lines  4   a  in the pattern P 1  is an example of a first interval and the interval between the lines  4   a  in the pattern P 2  is an example of a second interval. The lines  4   a  are an example of the mark (first mark). The pattern P 1  and the pattern P 2  may be provided adjacent to each other as illustrated in  FIG. 12  or may be separately provided. Furthermore, only one of the pattern P 1  and the pattern P 2  can be provided for the alignment. 
     Moire appears in the mark  4 A in  FIG. 12  when viewed through the lens assembly  2 . If the array of the marks  4 A is misaligned or tilted with respect to the array of the cylindrical lenses  23  of the lens assembly  2 , such moire facilitates a user to visually recognize the misalignment.  FIG. 13  illustrates an example in which the mark  4 A and the lens assembly  2  are aligned with each other.  FIG. 14  illustrates an example in which the mark  4 A and the lens assembly  2  are misaligned in the Y direction.  FIG. 15  illustrates an example in which the mark  4 A and the lens assembly  2  are tilted with respect to each other. It can be understood from  FIGS. 13 to 15  that moire appears as a result of using the mark  4 A according to the second embodiment, and the mark  4 A facilitates a user to recognize the alignment or misalignment of the lens assembly  2  and the medium  3  based on how the moire appears. Note that in  FIGS. 14 and 15 , the line  4   b  at the center is hard to recognize. The peripheries of the lens assembly  2  and the medium  3  may also be aligned in reference to the mark  4 A. Furthermore, moire may easily viewable if the lines  4   a  are provided in different colors between the patterns P 1  and P 2  or if the lines  4   a  are colored in different colors to set color patterns. 
     Modification of Second Embodiment 
     In a modification illustrated in  FIG. 16 , a mark  4 B includes a plurality of lines  4   a  provided at an interval in the Y direction and extending in parallel in the X direction, as the mark  12 A illustrated in  FIG. 12 . The mark  4 B also includes patterns P 1  and P 2  in which the lines  4   a  are arranged at different intervals (pitches). The interval between the lines  4   a  in the pattern P 1  is slightly different from that in the pattern P 2 . In this modification, the pattern P 1  and the pattern P 2 , both of which has the same width (length) in the X direction, are arranged alternately in the X direction. As in the example illustrated in  FIG. 1  when “d” denotes the number of dots in the image corresponding to the width of one cylindrical lens  23  in the Y direction, that is, the width of the cylindrical lens  23  in the Y direction, the interval between the lines  4   a  in the pattern P 1  is set to d+m (dots) (where m is an integer equal to or greater than one) and the interval between the lines  4   a  in the pattern P 2  is set to d-m (dots). Furthermore, in this example as well, the line  4   b  thicker than the other lines  4   a  and extending in the X direction is provided at the center in the Y direction. The pattern P 1  is an example of the first area and the pattern P 2  is an example of the second area. The interval between the lines  4   a  in the pattern P 1  is an example of the first interval and the interval between the lines  4   a  in the pattern P 2  is an example of the second interval. 
     Moire appears in the mark  4 B in  FIG. 16  when viewed through the lens assembly  2 . If the array of the mark  4 B is misaligned or tilted with respect to the array of the cylindrical lenses  23  of the lens assembly  2 , such moire facilitates a user to visually recognize the misalignment.  FIG. 17  illustrates an example in which the mark  4 B and the lens assembly  2  are aligned with each other.  FIG. 18  illustrates an example in which the mark  45  and the lens assembly  2  are misaligned in the Y direction.  FIG. 19  illustrates an example in which the mark  45  and the lens assembly  2  are tilted with respect to each other. It is apparent from  FIGS. 17 to 19  that moire appears as a result of using the mark  4 B according to the modification, and the mark  4 B enables a user to recognize the alignment or misalignment of the lens assembly  2  and the medium  3  more easily based on how the moire appears. Note that in  FIGS. 17 and 18 , the line  4   b  at the center is hard to recognize. In this modification as well, the moire may be more viewable if the lines  4   a  are provided in different colors between the patterns P 1  and P 2  or if the lines  4   a  are colored in different colors to set coloring patterns. Furthermore, the modification of the second embodiment illustrated in  FIGS. 16 to 19  has the same configuration as that in the first embodiment, therefore, it can attain the same effects or results as those of the first embodiment. 
     The embodiments and the modifications may also be implemented with some components or shape partly replaced. Furthermore, the embodiments and the modifications may also be implemented with some specifications such as the configurations or the shapes (e.g., structures, types, directions, shapes, sizes, lengths, widths, thicknesses, heights, numbers, arrangements, positions, and materials), modified. For example, specifications of components such as the lens member, the cylindrical lenses, the projections, the marks, and the intervals should not be limited to those disclosed in the embodiments and the modifications. Furthermore, the cylindrical lenses used for the alignment in reference to the marks may be of one of the two lens members. Furthermore, the alignment using the marks should not be limited to the lens assembly and the image (medium) and may be also applied to, for example, two lens members. Furthermore, the lens assembly or the lens members which can be aligned in reference to the marks should not be limited to those disclosed in the embodiment described above. For example, the two lens members of the lens assembly do not need to have the same shape or the lens members do not need to include the projections. The lens assembly may include only one lens member (one lenticular lens). Furthermore, the medium may be made of various types of materials such as paper, film, and a sheet. Furthermore, the medium may be an electric display such as a liquid crystal display (LCD) or an organic electro-luminescent display (OELD), or any other electric display devices such as an electrical scoreboard and a digital signage. Furthermore, the image may be a still image or a moving image. 
     Furthermore, embodiments may be implemented as specified below. 
     [1] An image display device comprising:
         a medium on which a first mark is disposed at a fixed position with respect to an image; and       

     a lens member including:
         a lenticular lens with a plurality of cylindrical lenses; and   a lens unit, wherein       

     the image display device is configured such that the image is shown through the lens member, and 
     a visually enlarged image of the first mark by the lens portion is used for aligning the lens member. 
     [2] The image display device according to [1], wherein the lens portion is one of the cylindrical lenses. 
     [3] The image display device according to [1] or [2], further comprising the medium.