Abstract:
A three-dimensional display device includes a plurality of projection portions to project a plurality of images, respectively, a plurality of wedge-shaped light guide plates corresponding to the plurality of projection portions, respectively, to emit the plurality of images, respectively, and a plurality of directional diffuser screen corresponding to the plurality of wedge-shaped light guide plates, respectively, to diffuse or transmit the plurality of images.

Description:
[0001]    This application claims the benefit of Korean Patent Application No. 10-2006-0055783, filed in Korea on Jun. 21, 2006, which is hereby incorporated by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a three-dimensional display device, and more particularly, relates to a volumetric type three-dimensional display device. 
         [0004]    2. Background of the Related Art 
         [0005]    A three-dimensional display uses technology that allows an observer to perceive a three-dimensional effect from a two-dimensional image. This technology has been widely utilized in display-relevant technical fields as well as home appliances, communication, aerospace, art and automobiles. To achieve a three-dimensional effect, a parallax of both eyes, namely, a distance of 65 mm, acts as a primary factor, and mental state and memory act as other factors. Thus, according to three-dimensional information transferred to a user, a three-dimensional display technology may be divided into a volumetric type, a holographic type and a stereoscopic type. Of these types, the volumetric type is suitable for an I-MAX film and has the advantage of supplying large-sized display images. 
         [0006]      FIG. 1  is a view schematically illustrating a volumetric type three-dimensional display device  10  according to the related art. As shown in  FIG. 1 , the volumetric type three-dimensional display device  10  includes first to fourth display portions  20 ,  30 ,  40  and  50 . The first to fourth display portions  20 ,  30 ,  40  and  50  display first to fourth partial images I 1 , I 2 , I 3  and I 4 , respectively. The first to fourth partial images I 1  to I 4  are produced by dividing one image according to depths of the one image. A user  60  synthesizes the first to fourth partial images I 1  to I 4  as a three-dimensional one image. Also, the user  60  adds positions of the first to fourth display portions  20  to  50 , namely, distances from the user  60  to the first to fourth display portions  20  to  50 , into image information of the first to fourth partial images I 1  to I 4 , thereby perceiving the one image as a three-dimensional image. 
         [0007]    However, the related art volumetric type three-dimensional display device  10  has the following limitations and disadvantages. Each display portion should display the display image produced by itself, and also should transmit the display images produced by the display portions behind it. Specifically, the second display portion  30  should transmit the first partial image I 1  produced by the first display portion  20 , the third display portion  40  should transmit the first and second partial images I 1  and I 2  produced by the first and second display portions  20  and  30 , and the fourth display portion  40  should transmit the first to third partial images I 1  to I 3  produced by the first to third display portions  20  to  30 . Accordingly, qualification of the display portion is limited. For this reason, emissive type display devices, such as organic electroluminescent display devices, field emission display devices, plasma display devices and the like, can not be used as the display portion of the volumetric type three-dimensional display device. 
         [0008]    While a non-emissive type display device, such as a liquid crystal display device, can be used for the display portion, it is difficult to set up a light source such as a backlight unit. When the non-emissive type display device has a low transmissivity, the partial images should pass through a plurality of non-emissive type display devices, thereby decreasing the brightness. Accordingly, a projection type display device is used as the display portion. The projection type display device generally needs a large complicated optical portion and a screen where an image is projected. When the projection type display device is adopted for the volumetric type three-dimensional display device, a distance between the screens should be long enough to set up the optical portion. However, due to the long distance, the user may not normally perceive the three-dimensional one image synthesized from the partial images. 
       SUMMARY OF THE INVENTION 
       [0009]    Accordingly, the present invention is directed to a three-dimensional display device that substantially obviates one or more of the problems due to limitations and disadvantages of the related art. 
         [0010]    An object of the present invention is to provide a three-dimensional display device with improved performance. 
         [0011]    Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
         [0012]    To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, according to an aspect of the present invention, the three-dimensional display device includes a plurality of projection portions to project a plurality of images, respectively, a plurality of wedge-shaped light guide plates corresponding to the plurality of projection portions, respectively, to guide the plurality of images, respectively, substantially toward a same direction, and a plurality of directional diffuser screen corresponding to the plurality of wedge-shaped light guide plates, respectively, to diffuse or transmit the plurality of images. 
         [0013]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiments of the invention and together with the description serve to explain the principle of the invention. In the drawings: 
           [0015]      FIG. 1  is a view schematically illustrating a volumetric type three-dimensional display device according to the related art; 
           [0016]      FIG. 2  is a view schematically illustrating a volumetric type three-dimensional display device according to an exemplary embodiment of the present invention; 
           [0017]      FIG. 3  is a view schematically illustrating a wedge-shaped light guide plate of the volumetric type three-dimensional display device according to the exemplary embodiment of the present invention; and 
           [0018]      FIG. 4  is a view schematically illustrating a directional diffuser screen of the volumetric type three-dimensional display device according to the exemplary embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0019]    Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. 
         [0020]      FIG. 2  is a view schematically illustrating a volumetric type three-dimensional display device  110  according to an exemplary embodiment of the present invention. As shown in  FIG. 2 , the volumetric type three-dimensional display device  110  includes first, second and third display portions  120 ,  130  and  140 . The first to third display portions  120  to  140  are sequentially disposed far to near from a user  160 . The first to third display portions  120  to  140  are spaced apart from each other. 
         [0021]    The first display portion  120  is disposed the farthest from the user  160  and includes a first projection portion  120   a , a first wedge-shaped light guide plate  120   b  and a first directional diffuser screen  120   c . The first display portion  120  serves to supply a first partial image I 1  to the user  160 . The second display portion  130  is disposed between the first and third display portions  120  and  140  and includes a second projection portion  130   a , a second wedge-shaped light guide plate  130   b  and a second directional diffuser screen  130   c . The second display portion  130  serves to supply a second partial image  12  to the user  160 . The third display portion  140  is disposed the nearest to the user  160  and includes a third projection portion  140   a , a third wedge-shaped light guide plate  140   b  and a third directional diffuser screen  140   c . The third display portion  140  serves to supply a third partial image I 3  to the user  160 . 
         [0022]    Each of the first to third projection portions  120   a  to  140   a  includes a display panel that produces each of the partial images I 1  to I 3 . The first to third wedge-shaped light guide plates  120   b  to  140   b  guide the respective partial images I 1  to I 3  substantially toward the same direction. The first to third directional diffuser screens  120   c  to  140   c  are arranged parallel with and apart from each other. The first to third display portions  120  to  140  display the first to partial images I 1  to I 3  in a similar manner. For example, the first projection portion  120   a  is disposed below the first wedge-shaped light guide plate  120   b , so as to project the first partial image I 1  into the first wedge-shaped light guide plate  120   b . The first partial image I 1  is projected to be reflected repeatedly on a front surface and a rear surface of the first wedge-shaped light guide plate  120   b . In other words, the first partial image I 1  is repeatedly reflected on the front and rear surfaces of the first wedge-shaped light guide plate  120   b  while an incidence angles of the first partial image I 1  on the front and rear surfaces is varied. When the incidence angle of the first partial image I 1  is equal to or less than a specific incidence angle, the first partial image I 1  is not reflected but emitted outside the first wedge-shaped light guide plate  120   b . The emitted first partial image I 1  is thus diffused by the first directional diffuser screen  120   c  and transferred to the user  160 . The first directional diffuser screen  120   c  diffuses or intactly transmits an incident light thereon according to an incidence angle of the incident light. For example, an incident light having an incidence angle within a specific range is diffused, whereas an incident light having another incidence angle, which is outside the specific range, is directly transmitted. 
         [0023]    A display operation of the second display portion  130  is similar to that of the first display portion  120 . The second projection portion  130   a  is disposed below the second wedge-shaped light guide plate  130   b  so as to project the second partial image I 2  into the second wedge-shaped light guide plate  130   b . The second partial image I 2  is projected to be reflected repeatedly on a front surface and a rear surface of the second wedge-shaped light guide plate  130   b . In other words, the second partial image I 2  is repeatedly reflected on the front and rear surfaces of the second wedge-shaped light guide plate  130   b  while an incidence angle of the second partial image I 2  on the front and rear surfaces is varied. When the incidence angle of the second partial image I 2  is equal to or less than a specific incidence angle, the second partial image I 2  is not reflected but emitted outside the second wedge-shaped light guide plate  130   b . The emitted second partial image I 2  is thus diffused at the second directional diffuser screen  130   c  and transferred to the user  160 . The second directional diffuser screen  130   c  diffuses or intactly transmits an incident light thereon according to an incidence angle of the incident light. For example, an incident light having an incidence angle within a specific range is diffused, whereas an incident light having another incidence angle, which is outside the specific range, is directly transmitted. 
         [0024]    A display operation of the third display portion  140  is similar to those of the first and second display portions  120  and  130 . The third projection portion  140   a  is disposed below the third wedge-shaped light guide plate  140   b  to project the third partial image I 3  into the third wedge-shaped light guide plate  140   b . The third partial image I 3  is projected to be reflected repeatedly on a front surface and a rear surface of the third wedge-shaped light guide plate  140   b . In other words, the third partial image I 3  is repeatedly reflected on the front and rear surfaces of the third wedge-shaped light guide plate  140   b  while an incidence angle of the third partial image I 3  on the front and rear surfaces is varied. When the incidence angle of the third partial image I 3  is equal to or less than a specific incidence angle, the third partial image I 3  is not reflected but emitted outside the third wedge-shaped light guide plate  140   b . The emitted third partial image I 3  is diffused at the third directional diffuser screen  140   c  and transferred to the user  160 . The third directional diffuser screen  140   c  diffuses or intactly transmits an incident light thereon according to an incidence angle of the incident light. For example, an incident light having an incidence angle within a specific range is diffused, whereas an incident light having another incidence angle, which is outside the specific range, is directly transmitted. 
         [0025]    As a result, the user  160  receives and synthesizes the first to third partial images I 1  to I 3 , thereby perceiving those as a three-dimensional image. Because each of the first to third wedge-shaped light guide plates  120   b  to  140   b  or each of the first to third directional diffuser screens  120   c  to  140   c  does not have a separate layer or a pattern that reduces transmissivity, the volumetric type three-dimensional display device  110  of the exemplary embodiment having the first to third display portions  120  to  140  can realize high transmissivity. Because the first to third display portions  120  to  140  use the first to third wedge-shaped light guide plates  120   b  to  140   b  instead of large optical portions of the related art, a set-up space for the large optical portion is omitted and a distance between the display portions  120  to  140  is minimized, thereby optimizing a three-dimensional effect. 
         [0026]    In the exemplary embodiment, three display portions  120  to  140  are described above. However, it is noted that the number of the display portions is not limited and can be varied. 
         [0027]      FIG. 3  is a view schematically illustrating a wedge-shaped light guide plate W of the volumetric type three-dimensional display device according to the exemplary embodiment. The wedge-shaped light guide plate W of  FIG. 3  is an example of the first to third wedge-type light guide plates  120   b  to  140   b  of  FIG. 2 . As shown in  FIG. 3 , the wedge-shaped light guide plate W may include a first surface  210  on which light is incident, and second and third surfaces  220  and  230  that face each other. The second surface  220  is inclined with respect to the third surface  230 . 
         [0028]    Although not shown in the drawings, a projection portion is disposed below the first surface  210  to supply a partial image, as described in  FIG. 2 . To explain a light path in the wedge-shaped light guide plate W, first and second lights L 1  and L 2  from the partial image will be described below. The first and second lights L 1  and L 2  are incident on the first surface  210  with different incidence angles. The first and second lights L 1  and L 2  are repeatedly reflected on the second and third surfaces  220  and  230  until the first and second lights L 1  and L 2  have incidence angles on the third surface  230  equal to or less than specific incidence angles. For example, the first light L 1  passes through the first surface  210  and has a first incidence angle θ 1  on the third surface  230 . Since the first incidence angle θ 1  is larger than a critical angle θc that is for a total reflection of the first light L 1 , the first light L 1  is reflected by the third surface  230  to the second surface  220 . Since the second and third surfaces  220  and  230  are inclined with respect to each other, the first light L 1  is reflected by the second surface  220 , and has a second incidence angle θ 2  less than the first angle θ 1  when it is incident on the third surface  230 . In this manner, as the first light L 1  is repeatedly reflected on the second and third surfaces  220  and  230 , the incidence angle of the first light L 1  on the third surface  230  is reduced. When the second incidence angle θ 2  is less than the critical angle θc, the first light L 1  incident on the third surface  230  is not reflected by the third surface  230  but emitted outward. The critical angle θc depends on a refractive index of a material of the wedge-shaped light guide plate W. In other words, the critical angle θc is controlled by the material of the wedge-shaped light guide plate W. 
         [0029]    Similar to the first light L 1 , the second light L 2  is also emitted outward when the second light L 2  has an incident angle on the third surface  230  less than the critical angle θc by being repeatedly reflected on the second and third surfaces  220  and  230 . Because the first and second lights L 1  and L 2  are incident differently on the first surface  210 , the first and second lights L 1  and L 2  may be emitted outward at different positions of the wedge-shaped light guide plate W. For example, the first light L 1  may be emitted at a position that has a first distance d 1  away from the first surface  210 , whereas the second light L 2  may be emitted at a position that has a second distance d 2  away from the first surface  210 . 
         [0030]    As described above, the wedge-shaped light guide plate W receives an image through the first surface  210  having a narrow width and projects the image through the third surface having a wide width. Thus, the volumetric type three-dimensional display device using the wedge-shaped light guide plate does not need a set-up space for an optical portion of the related art. 
         [0031]      FIG. 4  is a view schematically illustrating a directional diffuser screen of the volumetric type three-dimensional display device according to the exemplary embodiment of the present invention. The directional diffuser screen D of  FIG. 4  is an example of the first to third directional diffuser screens  120   c  to  140   c  of  FIG. 2 . As shown in  FIG. 4 , when first to third lights L 1  to L 3  are incident on the directional diffuser screen D with different incidence angles, the directional diffuser screen D diffuses lights having a specific condition and intactly transmits other lights. Specifically, the directional diffuser screen D diffuses lights having an incidence angle between a first incidence angle θ 1  and a second incidence angle θ 2 , and the directional diffuser screen D intactly transmits lights having other incidence angles. In other words, a partial image produced by a display portion having the directional diffuser screen D includes lights having incidence angles between the first incidence angle θ 1  and the second incidence angle θ 2 . Because the lights for the partial image have the incidence angles between the first and second incidence angles ƒ 1  and θ 2 , the lights for the partial image are all diffused by the directional diffuser screen D. On the contrary, lights having incidence angles not between the first and second angles θ 1  and θ 2 , namely, less than the first incidence angle θ 1  and more than the second incidence angle θ 2 , is not diffused but directly transmitted by the directional diffuser screen D. For example, as shown in  FIG. 4 , the third light L 3  has a third incidence angle θ 3  that is less than the first incidence angle θ 1 , and therefore intactly passes through the directional diffuser screen D and is transferred to the user  160 . 
         [0032]    As described above, the directional diffuser screen D serves as a screen when the light has an incidence angle within the range of θ 1  to θ 2 , and the directional diffuser screen D serves as a transparent plate when the light is not within the incidence angle range. Accordingly, the directional diffuser screen D serves as a screen for a partial image produced by the display portion having the directional diffuser screen D, and the directional diffuser screen serves as a transparent plate produced by other display portions behind the display portion having the directional diffuser screen D. According to such an arrangement, the volumetric type three-dimensional display device using the directional diffuser screen D can increase brightness. 
         [0033]    The display panel of the display portion as described in the above exemplary embodiments may include a flat display panel, for example, a liquid crystal display (LCD), a field emission display (FED), a plasma display panel (PDP) and a electroluminescent display (EL). 
         [0034]    It will be apparent to those skilled in the art that various modifications and variations can be made in the three-dimensional display device of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.