Patent Publication Number: US-2012026161-A1

Title: Stereoscopic display

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority benefit of U.S. provisional application Ser. No. 61/369,085, filed on Jul. 30, 2010. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of specification. 
    
    
     TECHNICAL FIELD 
     The disclosure relates to a display, and more particularly, to a stereoscopic display. 
     BACKGROUND 
     With development of display technology, displays having better image quality, richer color performance and better performance effect are continuously developed. In recent years, a stereoscopic display technology has extended to home display applications from cinema applications. Since a key technique of the stereoscopic display technology is to ensure a left eye and a right eye of a user to respectively view left-eye images and right-eye images of different viewing angles, according to the conventional stereoscopic display technology, the user generally wears a special pair of glasses to filter the left-eye images and the right-eye images. 
     However, to wear the special pair of glasses may generally cause a lot of inconveniences, especially for a nearsighted or farsighted user who has to wear a pair of glasses which corrects vision, the extra pair of special glasses may cause discomfort and inconvenience. Therefore, a naked-eye stereoscopic display technology, i.e. autostereoscopic display technology, becomes one of the key focuses in researches and developments. 
     The autostereoscopic display technology is categorized into spatial multiplexing technology and temporal multiplexing technology. The spatial multiplexing technology compromises the resolution of the frame to generate a plurality of view regions. On the other hand, the temporal multiplexing technology generates a plurality of view regions but does not compromise the resolution of the frame. However, conventional temporal multiplexing technology needs scanning element operating at very high frequency, which encounters more difficulty in mass production and limits the applicability of the autostereoscopic display. 
     SUMMARY 
     A stereoscopic display including a displaying element, a light converging element, and a scanning element is introduced herein. The displaying element is adapted to provide a light. The light converging element is disposed on a transmission path of the light for converging the light to at least one view region. The scanning element is disposed on the transmission path of the light for changing at least one transmission direction of the light with time. The scanning element comprises a plurality of scanning units. Each of the scanning units comprises a first electrode, a second electrode, and a first material with anisotropic refractive indices. The first material with anisotropic refractive indices is disposed between the first electrode and the second electrode. When voltage between the first electrode and the second electrode is changed, the molecules of the first material with anisotropic refractive indices rotate so as to change the transmission direction of the light with time. 
     Several exemplary embodiments accompanied with figures are described in detail below to further describe the disclosure in details. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are comprised to provide further understanding, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments and, together with the description, serve to explain the principles of the disclosure. 
         FIG. 1A  is a schematic perspective view of a stereoscopic display according to an exemplary embodiment. 
         FIG. 1B  is a schematic cross-sectional view of the stereoscopic display in  FIG. 1A . 
         FIG. 2  is a schematic cross-sectional view of the scanning element in  FIG. 1B . 
         FIGS. 3A and 3B  are schematic cross-sectional views of the scanning unit in  FIG. 2  respectively in two different states. 
         FIG. 4  is schematic cross-sectional view of the scanning unit of a stereoscopic display according to another exemplary embodiment. 
         FIGS. 5A and 5B  are schematic cross-sectional views of the scanning unit of a stereoscopic display according to yet another exemplary embodiment. 
         FIG. 6  is schematic cross-sectional view of the scanning unit of a stereoscopic display according to still another exemplary embodiment. 
         FIGS. 7A and 7B  are schematic cross-sectional views of the scanning unit of a stereoscopic display in two different states according to yet still another exemplary embodiment. 
         FIG. 8  is a schematic cross-section view of a stereoscopic display according to yet still another exemplary embodiment. 
         FIG. 9  is a schematic cross-section view of a stereoscopic display according to yet still exemplary embodiment. 
         FIG. 10  is a schematic cross-section view of a stereoscopic display according to yet still exemplary embodiment. 
         FIG. 11  is a schematic cross-section view of a stereoscopic display according to yet still exemplary embodiment. 
         FIG. 12  is a schematic cross-section view of a stereoscopic display according to yet still exemplary embodiment. 
         FIG. 13A  is a schematic cross-section view of a stereoscopic display according to yet still exemplary embodiment. 
         FIG. 13B  is a schematic cross-section view of the lenticular array assembly in  FIG. 13A . 
         FIG. 14  is a schematic cross-section view of a stereoscopic display according to yet still exemplary embodiment. 
         FIG. 15  is a schematic cross-section view of a stereoscopic display according to yet still exemplary embodiment. 
         FIG. 16  is a schematic cross-section view of a stereoscopic display according to yet still exemplary embodiment. 
         FIG. 17  is a schematic cross-sectional view of the stereoscopic display according to yet still exemplary embodiment. 
         FIG. 18A  is a schematic cross-sectional view of the stereoscopic display according to still yet another exemplary embodiment. 
         FIG. 18B  is a schematic cross-sectional view of the scanning element in  FIG. 18A . 
     
    
    
     DETAILED DESCRIPTION OF DISCLOSED EMBODIMENTS 
       FIG. 1A  is a schematic perspective view of a stereoscopic display according to an exemplary embodiment,  FIG. 1B  is a schematic cross-sectional view of the stereoscopic display in  FIG. 1A , and  FIG. 2  is a schematic cross-sectional view of the scanning element in  FIG. 1B . Referring to  FIGS. 1A ,  1 B, and  2 , the stereoscopic display  100  in this embodiment comprises a displaying element  110 , a light converging element  120 , and a scanning element  200 . In this embodiment, the stereoscopic display is, for example, an autostereoscopic display. The displaying element  110  is adapted to provide a light I. In this embodiment, the displaying element  110  is a display, for example, a liquid crystal display (LCD). However, in other embodiments, the displaying element  110  may be a self-luminous display, for example, an organic light emitting diode (OLED) array display, a plasma display panel (PDP), a light emitting diode (LED) array display, a cathode ray tube (CRT), or another display device. Moreover, in this embodiment, the light I is, for example, an image light carrying the information of image frames. 
     The light converging element  120  is disposed on a transmission path of the light I for converging the light I to at least one view region. For example, the light converging element  120  converges the light I (i.e. the light I 1  shown in  FIG. 1B ) to a view region A 1  as shown in  FIG. 1B . In this embodiment, the converging element  120  is a lenticular array. Specifically, the lenticular array comprises a plurality of rod-shaped lenticular lenses  122  arranged along a direction, e.g. the x-direction in  FIG. 1B . Each of the rod-shaped lenticular lenses  122  extends along a y-direction substantially perpendicular to the x-direction, as shown in  FIG. 1B . In this embodiment, each of the rod-shaped lenticular lenses  122  is a plane-convex lens, but the disclosure is not limited thereto. Moreover, in this embodiment, the pitch P 1  of the rod-shaped lenticular lenses  122  corresponds to N time(s) the pitch P 2  of pixels  112  of the displaying element  110 , and N is a natural number. In this embodiment, the pitch P 1  corresponds to one time the pitch P 2 . That is to say, the size of the pitch P 1  is about the size of the pitch P 2 . For example, the pitch P 1  is 0.9 times to 1 time the pitch P 2 . As a result, the light converging element  120  of this embodiment generates a single view image. 
     The scanning element  200  is disposed on the transmission path of the light I for changing at least one transmission direction of the light I with time. In this embodiment, the light converging element  120  is disposed between the displaying element  110  and the scanning element  200 . Since the light converging element  120  converges the light I, the light I after passing through the light converging element  120  has multiple transmission directions. In this embodiment, the scanning element  200  is adapted to change the transmission directions of the light I 1  to the transmission directions of the light I 2 , so that the light I can be transmitted to the view region A 2 . Moreover, the scanning element  200  is also adapted to change the transmission directions of the light I 1  to the transmission directions of the light I 3 , so that the light can be transmitted to the view region A 3 . The scanning element  200  transmits the light Ito the view regions A 1 , A 2 , and A 3  at different time. 
     Specifically, the scanning element  200  comprises a plurality of scanning units  210 . Each of the scanning units  210  comprises a first electrode  212 , a second electrode  218 , and a first material  214  with anisotropic refractive indices. The first material  214  with anisotropic refractive indices is disposed between the first electrode  212  and the second electrode  218 . In this embodiment, the first material  214  with anisotropic refractive is a birefringent material, for example, liquid crystal. Each liquid crystal molecule has an extraordinary index of refraction n e  and an ordinary index of refraction n o . In this embodiment, when the electric field of light is parallel to the optical axis of the liquid crystal molecule, the liquid crystal molecule serves as a material with the extraordinary index of refraction n e . On the other hand, when the electric field of light is perpendicular to the optical axis of the liquid crystal molecule, the liquid crystal molecule serves as a material with ordinary index of refraction n o . In this embodiment, n e &gt;n o . However, in other embodiment, the liquid crystal with n e &lt;n o  may also be used. 
     In this embodiment, each of the scanning units  210  further comprises a transparent material  216  disposed beside the first material  214  with anisotropic refractive indices and between the first electrode  212  and the second electrode  218 , and an interface  223  of the first material  214  with anisotropic refractive indices and the transparent material  216  is inclined with respect to a displaying surface  111  of the displaying element  110 . In this embodiment, the transparent material  216  is, for example, a solid prism. 
       FIGS. 3A and 3B  are schematic cross-sectional views of the scanning unit in  FIG. 2  respectively in two different states. Referring to  FIGS. 1B ,  2 ,  3 A, and  3 B, when voltage between the first electrode  212  and the second electrode  218  is changed, the molecules  215  of the first material  214  with anisotropic refractive indices rotate so as to change the transmission direction of the light I with time. 
     Specifically, the light I provided by the displaying element  110  is, for example, a linearly polarized beam. In this embodiment, when the scanning unit  210  is in the state of  FIG. 3A , the molecules  215  lie down and is about parallel to the second electrode  218 , and the electric field E of the light I is parallel to the optical axes of the molecules  215 . At this time, the first material  214  serves as a material with n e  to transmit the light I. Moreover, the transparent material  216  has an index of refraction n t . In this embodiment, n e &gt;n t &gt;n o , but the disclosure is not limited thereto. Since n e &gt;n t , when the light I passes through the interface  223 , the light I is refracted toward the left. 
     On the other hand, when the scanning unit  210  is in the state of  FIG. 3B , the molecules  215  stands up and is about perpendicular to the second electrode  218 , and the electric field E of the light I is perpendicular to the optical axes of the molecules  215 . At this time, the first material  214  serves as a material with n o  to transmit the light I. Since n o &lt;n t , when the light I passes through the interface  223 , the light I is refracted toward the right. 
     The orientations of the molecules  215  are determined by the voltage between the first electrode  212  and the second electrode  218 . Therefore, by changing the voltage between the first electrode  212  and the second electrode  218  with time, the transmission directions of the light I are changed with time. As a result, the stereoscopic display transmits the light Ito the view regions A 1 , A 2 , and A 3  at different time. In this embodiment, the changing period of the transmission directions of the light I is short enough so that a user can observe continuous images. In this way, when a left eye and a right eye of the user are respectively located in the view regions A 2  and A 1 , the user observes a stereoscopic image at a viewing angle. Moreover, when a left eye and a right eye of a user are respectively located in the view regions A 1  and A 3 , the user observes another stereoscopic image at another viewing angle. 
     As long as the changing period of the transmission directions of the light I is short enough so that the user can observe continuous images, the changing period of the transmission directions is short enough to generate good multi-view images, and thus the operation frequency of the scanning element can be lower. As a result, the stereoscopic display  100  of this embodiment is favorable for mass production, and it has more applicability. 
     In this embodiment, the stereoscopic display  100  further comprises a control unit  130  for controlling the voltage between the first electrode  212  and the second electrode  218  so as to control rotation of the molecules of the first material with anisotropic refractive indices. Moreover, the control unit  130  controls the displaying element  110  to display a plurality of frames at different time respectively corresponding to transmission orientations of the light I at different time. For example, when the control unit  130  controls the voltage so that the light I is transmitted to the view region A 2 , the displaying element  110  provides the light I 2  containing a first view frame. When the control unit  130  controls the voltage so that the light I is transmitted to the view region A 1 , the displaying element  110  provides the light I 1  containing a second view frame. When the control unit  130  controls the voltage so that the light I is transmitted to the view region A 3 , the displaying element  110  provides the light I 3  containing a third view frame. When the left eye and the right eye of the user are respectively located in the view regions A 2  and A 1 , the brain of the user combines the first view frame and the second view frame to form a first view stereoscopic image. On the other hand, when the left eye and the right eye of another user are respectively located in the view regions A 1  and A 3 , the brain of the user combines the second view frame and the third view frame to form a second view stereoscopic image. The first view stereoscopic image simulates a view seen by the user from an orientation, and the second view stereoscopic image simulates a view seen by the user from another orientation. As a result, a plurality of users can watch the stereoscopic display  100  at the same time, and the users can see different stereoscopic images from different orientation, which is similar to that the objects in the images are in the 3-dimensional space so that the users located at different positions see different portions of the objects from different orientations. 
     In this embodiment, when the control unit  130  changes the voltage between the first electrode  212  and the second electrode  218  from a first voltage value to a second voltage value, the light I scans from a first orientation (e.g. the orientation in which the light I is transmitted to the view region A 2 ) to a second orientation (e.g. the orientation in which the light I is transmitted to the view region A 3 ). On the other hand, when the control unit  130  changes the voltage between the first electrode  212  and the second electrode  218  from the second voltage value to the first voltage value, the light I scans from the second orientation to the first orientation. In this embodiment, when the light I scans from the first orientation to the second orientation, the light scans through a third orientation (e.g. the orientation in which the light I is transmitted to the view region A 1 ). Moreover, when the light I scans from the second orientation to the first orientation, the light I also scans through a third orientation. 
     In this embodiment, the first voltage value is substantially zero. For example, the second electrode  218  is grounded. When the control unit  130  does not apply voltage to the first electrode  212 , the voltage between the first electrode  212  and the second electrode  218  is substantially zero. At this time, the molecules  215  lie down, and the light I is refracted toward the left. When the control unit  130  applies voltage to the first electrode  212 , the voltage between the first electrode  212  and the second electrode  218  is not zero, and the light is refracted toward the right. That is to say, when the control unit  130  turns on the voltage, the molecules  215  rotate from the orientation shown in  FIG. 3A  to the orientation shown in  FIG. 3B , and the light I scans the view regions A 2 , A 1 , and A 3  in sequence. When the control unit  130  turns off the voltage, the molecules  215  rotates from the orientation shown in  FIG. 3B  to the orientation shown in  FIG. 3A , and the light I scans the view regions A 3 , A 1 , and A 2  in sequence. As a result, if the frequency of each frame is 60 Hz, the scanning frequency of the canning element  200  may be 30 Hz, and the frequency of the control unit  130  to drive the scanning element  200  may be 30 Hz. That is to say, the operation frequency of the scanning element  200  is effectively reduced. Moreover, in this embodiment, what the control unit  130  does is to turn on the voltage to a single value and turn off the voltage, which is very simple. As a result, the control unit  130  may be effectively simplified, which reduces the cost of the control unit  130 . 
     The disclosure does not limit the number of the view regions to three. In other embodiments, the view regions may be more than three, and the control unit controls the displaying element to display more than three frames respectively when the light scans more than three view regions. 
       FIG. 4  is schematic cross-sectional view of the scanning unit of a stereoscopic display according to another exemplary embodiment. Referring to  FIG. 4 , the stereoscopic display of this embodiment is similar to the stereoscopic display  100  shown in  FIG. 1B , and the differences therebetween are as follows. In the scanning unit  210   a  according to this embodiment, a first electrode  212   a  comprises a plurality of discrete sub-electrodes  213  arranged from a first end E 1  of the first electrode  212   a  to a second end E 2  of the first electrode  212   a.  When the control unit  130  apply voltage to the first electrode  212   a,  the control unit  130  respectively applies a plurality of voltage values to the discrete sub-electrodes  213 , and the voltage values decreases from the first end E 1  to the second end E 2 . Since the thickness of the first material  214  decreases from the first end E 1  to the second end E 2 , the voltage values decreasing from the first end E 1  to the second end E 2  makes the rotation of the molecules more simultaneous, which makes the refraction of the light I more accurate. In another embodiment, the second electrode  218  may also comprise a plurality of discrete sub-electrodes, and when the control unit  130  apply a plurality of voltage values, respectively to the sub-electrodes, decreasing from the first end E 1  to the second end E 2 . Alternatively, the first electrode may be a continuous electrode while the second electrode comprises a plurality of discrete sub-electrodes. 
       FIGS. 5A and 5B  are schematic cross-sectional views of the scanning unit of a stereoscopic display according to yet another exemplary embodiment. Referring to  FIGS. 5A and 5B , the stereoscopic display in this embodiment is similar to the stereoscopic display  100  in  FIG. 1B , and the differences therebetween are as follows. In this embodiment, each of the scanning unit  210   b  further comprises a transparent plate  222  disposed at the interface  223 , wherein a transparent material  216   b  is liquid, and the transparent plate  222  separates the first material  214  with anisotropic refractive indices and the transparent material  216   b.  Moreover, in this embodiment, the transparent material  216   b  is a second material with anisotropic refractive indices, for example, liquid crystal. In addition, the transparent plate  222  is a third electrode. In the state shown in  FIG. 5A , the control unit applies voltage between the first electrode  212  and the third electrode (i.e. the transparent plate  222 ), and molecules  217   b  of the transparent material  216   b  stand up, so that the transparent material  216   b  serves as a material with the ordinary index of refraction of the molecules  217   b  to transmit the light I. At this time, the control unit does not apply voltage between the second electrode  218  and the third electrode (i.e. the transparent plate  222 ), and the molecules  215  of the first material  214  lie down, so that the first material  214  serves as a material with the extraordinary index of refraction of the molecules  215  to transmit the light I. In this embodiment, the extraordinary index of refraction of the molecules  215  is greater than the ordinary index of refraction of the molecules  217   b,  so that the light I is refracted toward the right. 
     On the other hand, in the state shown in  FIG. 5B , the control unit does not apply voltage between the first electrode  212  and the third electrode (i.e. the transparent plate  222 ), and molecules  217   b  of the transparent material  216   b  lie down, so that the transparent material  216   b  serves as a material with the extraordinary index of refraction of the molecules  217   b  to transmit the light I. At this time, the control unit applies voltage between the second electrode  218  and the third electrode (i.e. the transparent plate  222 ), and the molecules  215  of the first material  214  stand up, so that the first material  214  serves as a material with the ordinary index of refraction of the molecules  215  to transmit the light I. In this embodiment, the ordinary index of refraction of the molecules  215  is less than the extraordinary index of refraction of the molecules  217   b,  so that the light I is refracted toward the left. When the scanning element  210   b  changes the state from that shown in  FIG. 5A  to that shown in  FIG. 5B , the light I scans from the right to the left. On the other hand, when the scanning element  210   b  changes the state from that shown in  FIG. 5B  to that shown in  FIG. 5A , the light I scans from the left to the right. 
     In another embodiment, the transparent plate  222  may not serve as an electrode, and the control unit does not apply voltage to the transparent plate  222 . Moreover, the molecules  215  and molecules  217   b  are respectively two different types of liquid crystal molecules. The molecules  217   b  stand up when there is no electric field and lie down when there exists an electric field, while the molecules  215  stand up when there exists an electric field and lie down when there is no electric field. Alternatively, the extraordinary index of refraction of the molecules  217   b  may be less than the ordinary index of refraction of the molecules  217   b,  while the extraordinary index of refraction of the molecules  215  may be greater than the ordinary index of refraction of the molecules  215 . In yet another embodiment, the transparent material  216   b  may also be replaced by a material with isotropic index of refraction. 
       FIG. 6  is schematic cross-sectional view of the scanning unit of a stereoscopic display according to still another exemplary embodiment. Referring to  FIG. 6 , a scanning unit  210   c  in this embodiment is similar to the scanning unit  210   b  in  FIGS. 5A and 5B , and the differences therebetween are as follows. In the scanning unit  210   c  according to this embodiment, the first electrode  212   a  comprises a plurality of discrete sub-electrodes  213 , and the second electrode  218   c  comprises a plurality of discrete sub-electrodes  219 . When the control unit applies a plurality of voltage values respectively to the sub-electrodes  213 , the voltage values decrease from the first end E 1  to the second end E 2 . However, when the control unit applies a plurality of voltage values respectively to the sub-electrodes  219 , the voltage values increase from the first end E 1 ′ of the second electrode  218   c  to the second end E 2 ′ of the second electrode  218   c.  The effect achieved by this embodiment is similar to that described in the embodiment of  FIG. 4 , so that it is not repeated herein. 
     In another embodiment, the second electrode may be a continuous electrode while the first electrode comprises a plurality of sub-electrodes. Alternatively, the first electrode may be a continuous electrode while the second electrode comprises a plurality of sub-electrodes. 
       FIGS. 7A and 7B  are schematic cross-sectional views of the scanning unit of a stereoscopic display in two different states according to yet still another exemplary embodiment. Referring to  FIGS. 7A and 7B , the stereoscopic display in this embodiment is similar to the stereoscopic display  100  in  FIG. 1B , and the differences therebetween are as follows. In the scanning unit  210   d  of this embodiment, there is no transparent material  216  as shown in  FIG. 2 . Moreover, the first electrode  212   a  comprises a plurality of discrete sub-electrodes  213 . In the state shown in  FIG. 7A , the control unit applies a plurality of voltage values decreasing from the first end E 1  to the second end E 2 , and the index of refraction of the first material  214  increases from the first end E 1  to the second end E 2 , so that the light I refracted toward the right. On the other hand, in the state shown in  FIG. 7B , the control unit applies a plurality of voltage values increasing from the first end E 1  to the second end E 2 , and the index of refraction of the first material  214  decreases from the first end E 1  to the second end E 2 , so that the light I refracted toward the left. 
     When the state of the scanning element  210   d  changes from that shown in  FIG. 7A  to that shown in  FIG. 7B , the light I scans from the right to the left. On the other hand, when the state of the scanning element  210   d  changes from that shown in  FIG. 7B  to that shown in  FIG. 7A , the light I scans from the left to the right. 
       FIG. 8  is a schematic cross-section view of a stereoscopic display according to yet still another exemplary embodiment. Referring to  FIG. 8 , the stereoscopic display  100   e  in this embodiment is similar to the stereoscopic display  100  in  FIG. 1B , and the difference therebetween is as follows. In the stereoscopic display  100   e,  the converging element  120   e  is a lenticular array, and the distance between the converging element  120   e  and the displaying element  110  and the pitch of the rod-shaped lenticular lenses are appropriate designed so that the spatial frequency of the view regions is increased. As a result, a plurality of view regions A 1  repeats from the left to the right, and so do the view regions A 2  and A 3 . That is to say, the stereoscopic display  100  generates a plurality of sets of three views. Specifically, when the scanning units of the scanning element  130  are in the state shown in  FIG. 3A , the light I is transmitted to the plurality of view regions A 2 , and the view regions A 2 , A 1 , and A 3  repeat again and again in the space from the left to the right. On the other hand, when the scanning units of the scanning element  130  are in the state shown in  FIG. 3B , the light I is transmitted to the plurality of view regions A 3 . When the scanning units are in the state between that shown in  FIG. 3A  and that shown in  FIG. 3B , the light I is transmitted to the plurality of view regions A 1 . The scanning angle of the scanning element  130  covers the range within which each sub-light of the light I scans from the view region A 2  through the view region A 1  to the view region A 3  in a single set of the view regions A 2 , A 1 , and A 3 , and the converging element  120   e  splits the light into a plurality of sub-lights respectively transmitted to different sets of the view regions A 2 , A 1 , and A 3 . 
       FIG. 9  is a schematic cross-section view of a stereoscopic display according to yet still exemplary embodiment. Referring to  FIG. 9 , the stereoscopic display  100   f  in this embodiment is similar to the stereoscopic display  100  in  FIG. 1B , and the difference therebetween is as follows. The stereoscopic display  100  uses temporal multiplexing technology, i.e. the light I scanning different view regions A 2 , A 1 , and A 3  at different time. However, the stereoscopic display  100   f  uses both the temporal multiplexing technology and the spatial multiplexing technology. Specifically, in this embodiment, the pitch P 1 ′ of the rod-shaped lenticular lenses  122   f  of a converging element  120   f  corresponds to 2 times the pitch P 2  of pixels  112  of the displaying element  110 . That is to say, the size of the pitch P 1 ′ is about two times the size of the pitch P 2 . For example, the pitch P 1 ′ is 1.8 to 2 times the pitch P 2 . As a result, the converging element  120   f  of this embodiment generates two view images. For example, the light I 1  from the odd columns of the pixels  112  is transmitted to the view region A 1 , and the light I 1 ′ from the even columns of the pixels  112  is transmitted to the view region A 1 ′. Moreover, the scanning element  200  makes the light I scan from where the light I 1  scans to where the image I 2  scans, and the scanning element  200  makes the light I scan from where the light I 1 ′ scans to where the light I 2 ′ scans. As a result, the converging element  120   f  achieves spatial multiplexing, and the scanning element  200  achieves temporal multiplexing. 
     Specifically, every two adjacent lines of the pixels  112  (one line is denoted by  112   a,  and the other line is denoted by  112   b ) form a pixel set  113 , and the control unit  130  (referring to  FIG. 1B ) is also for driving different lines of the pixels  112  in each of the pixel sets  113  to respectively show images of two different viewing angles. Specifically, all the pixels  112   a  of the displaying element  110  show an image of a first viewing angle, and meanwhile all the pixels  112   b  of the displaying element  110  show another image of a second viewing angle, which achieves spatial multiplexing. When the scanning element  200  scans, the pixels  112   a  show images of different viewing angles at different time, and the pixels  112   b  also show images of different viewing angles at different time, which achieves temporal multiplexing. 
     In other embodiments, the pitch of the rod-shaped lenticular lenses of the converging element corresponds to K times the pitch P 2  of pixels  112  of the displaying element  110 , wherein K is an integer greater than and equal to 3. As a result, the converging element generates K view images. That is to say, the size of the pitch of the rod-shaped lenticular lenses is about K times the size of the pitch P 2 . For example, the pitch of the rod-shaped lenticular lenses is 0.9K to 1K times the pitch P 2 , every K adjacent lines of the pixels  112  form a pixel set  113 , and the control unit  130  (referring to  FIG. 1B ) is also for driving different lines of the pixels  112  in each of the pixel sets  113  to respectively show images of K different viewing angles. 
       FIG. 10  is a schematic cross-section view of a stereoscopic display according to yet still exemplary embodiment. Referring to  FIG. 10 , the stereoscopic display  100   g  in this embodiment is similar to the stereoscopic display  100  in  FIG. 1B , and the difference therebetween is as follows. In the stereoscopic display  100   g  in this embodiment, the scanning element  200  is disposed between the displaying element  110  and the light converging element  120 . The scanning element  200  makes the light I scan the converging element  120  first, and the converging element  120  then converges the image I to the view regions A 2 , A 1 , and A 3  at different time. 
       FIG. 11  is a schematic cross-section view of a stereoscopic display according to yet still exemplary embodiment. Referring to  FIG. 11 , the stereoscopic display  100   h  in this embodiment is similar to the stereoscopic display  100  in  FIG. 1B , and the difference therebetween is as follows. The stereoscopic display  100   h  in this embodiment further comprises a sensor  170  for detecting positions of eyes of at least one user ( FIG. 11  showing two users). The sensor  170  is, for example, a charge coupled device (CCD) camera, or a complementary metal oxide semiconductor (CMOS) camera. The control unit  130  controls the rotation of the molecules of the first material  214  (see  FIG. 2 ) with anisotropic refractive indices so that the light I scans the positions of the eyes of the user. For example, the light I scans the left eye L 1  and the right eye R 1  of a first user, and scans the left eye L 2  and the right eye R 2  of a second user. When the light I scans the left eye L 1 , the right eye R 1 , the left eye L 2 , and the right eye R 2  in sequence, the control unit  130  controls the displaying element  110  to respectively display corresponding frames to left eye L 1 , the right eye R 1 , the left eye L 2 , and the right eye R 2  in sequence. As a result, the operation frequency of the displaying element  110  may be adjusted according to the number of the user(s). When the number of the user(s) is less, the displaying element  110  may operate in lower frequency, which saves the power and lengthen the life span of the displaying element  110 . Moreover, in this embodiment, when the positions of the eyes of the user move, the control unit  130  controls the rotation of the molecules so that the light dynamically follows movement of the eyes of the user. Moreover, when the molecules of the first material  214  rotate to the orientation corresponding to the positions of the eyes of the user, the control unit  130  controls the displaying element  110  to display corresponding frames. As a result, the user can see correct stereoscopic frames at different positions. 
       FIG. 12  is a schematic cross-section view of a stereoscopic display according to yet still exemplary embodiment. Referring to  FIG. 12 , the stereoscopic display  100   i  in this embodiment is similar to the stereoscopic display  100  in  FIG. 1B , and the difference therebetween is as follows. In this embodiment, the stereoscopic display  100   i  further comprises a switchable scattering panel  140  disposed on the transmission path of the light I between the light converging element  120  and the scanning element  200 . In this embodiment, the switchable scattering panel  140  is, for example, a polymer dispersed liquid crystal (PDLC) panel, and comprises an electrode  142 , an electrode  146 , and a PDLC layer  144  between the electrode  142  and the electrode  146 . The switchable scattering panel  140  is adapted to switch to a blurry condition (for example, the control unit  130  applying voltage between the electrodes  142  and  146  to make the PDLC layer  144  blurry) to scatter the light or a clear condition (for example, the control unit  130  not applying voltage between the electrodes  142  and  146  to make the PDLC layer  144  clear) to pass the light through, so as to switch the stereoscopic display  100   i  between a 2-dimensional mode and a 3-dimensional mode. That is to say, when the switchable scattering panel  140  is in the blurry condition, the stereoscopic display  100   i  is switched to the 2-dimensional mode. When the switchable scattering panel  140  is in the clear condition, the stereoscopic display  100   i  is switched to the 3-dimensional mode. 
     In another embodiment, the switch between the 2-dimensional mode and the 3-dimensional mode may also be achieved by the stereoscopic display  100  (referring to  FIG. 1B ). The stereoscopic display  100  does not have switchable scattering panel  140 . 
     However, when the stereoscopic display  100  is switched to 2-dimensional mode, the pixels  112  of the displaying element  110  show the same image when the scanning element  210  scans from the state shown in  FIG. 3A  to the state shown in  FIG. 3B , so that the user can see the same image in view regions A 1 , A 2 , and A 3 , which means the user sees a 2-dimensional image. 
       FIG. 13A  is a schematic cross-section view of a stereoscopic display according to yet still exemplary embodiment, and  FIG. 13B  is a schematic cross-section view of the lenticular array assembly in  FIG. 13A . Referring to  FIGS. 13A and 13B , the stereoscopic display  100   j  in this embodiment is similar to the stereoscopic display  100  in  FIG. 1B , and the difference therebetween is as follows. In this embodiment, the stereoscopic display  100   j  further comprises a lenticular array assembly  150 , wherein the scanning element  200  is disposed between the displaying element  110  and the lenticular array assembly  150 . The lenticular array assembly  150  comprises a plurality of first strip-shaped convex surfaces  152  and a plurality of second strip-shaped convex surfaces  154 . The first strip-shaped convex surfaces  152  are arranged along a direction (e.g. the x-direction), and each of the first strip-shaped convex surfaces  152  extends along another direction (e.g. the y-direction). The second strip-shaped convex surfaces  154  are arranged along the x-direction, and each of the second strip-shaped convex surfaces  154  extends along the y-direction. The first strip-shaped convex surfaces  152  and the second strip-shaped convex surfaces  154  face away from each other. In this embodiment, the lenticular array assembly  150  further comprises a diffusion film  156  disposed between the first strip-shaped convex surfaces  152  and the second strip-shaped convex surfaces  154 . For example, the first strip-shaped convex surfaces  152  are on a lenticular array  162 , the second strip-shaped convex surfaces  154  are on another lenticular array  164 , and the diffusion film  156  is disposed between the lenticular arrays  162  and  164 . 
     In this embodiment, the diffusion film  156  is substantially disposed on foci f 1  of the first strip-shaped convex surfaces  152  and on foci f 2  of the second strip-shaped convex surfaces. If the scanning angle range of the scanning element  200  is θ, after the light I passes through the lenticular array assembly  150 , the scanning angle range of the image I become θ′, wherein θ′=tan −1 (f 2 ·tan θ/f 1 ). In this embodiment, f 2  is greater than f 1 , so that θ′ is greater than θ. When f 2 /f 1  is greater, θ′ is greater than θ more. As a result, if the scanning angle range of the scanning element  200  is not very large, the lenticular array assembly  150  effectively increases the scanning angle range of the light I. Besides, the lenticular array assembly  150  transmit the light I to a view region opposite to the view region to which the scanning element  200  transmit. For example, when the scanning element  200  scans from the left to the right, the light I after passing through the lenticular array assembly  150  scans from the right to the left. As a result, the sequence of the frames displayed by the displaying element  110  in this embodiment is reversed with respect to the sequence of the frames displayed by the displaying element  110  of the stereoscopic display  100  in  FIG. 1B . 
       FIG. 14  is a schematic cross-section view of a stereoscopic display according to yet still exemplary embodiment. Referring to  FIG. 14 , the stereoscopic display  100   k  in this embodiment is similar to the stereoscopic display  100  in  FIG. 1B , and the difference therebetween is as follows. In this embodiment, the converging element  120   k  is a parallax barrier. The parallax barrier comprises a plurality of discrete opaque strips  122   k  arranged along a direction (e.g. the x-direction), and each of the opaque strips  122   k  extends along another direction (e.g. the y-direction). The pitch of the discrete opaque strips  122   k  corresponds to N times the pitch of pixels  112  of the displaying element  110 , and N is a natural number. The light I passes through the region between two opaque strips  122   k,  and the effect of the parallax barrier is similar to that of the lenticular array. 
     When N is greater than or equal to 2, every N adjacent lines of the pixels  112  form a pixel set, and the control unit  130  is also for driving different lines of the pixels  112  in each of the pixel sets to respectively show images of N different viewing angles at substantially the same time. 
       FIG. 15  is a schematic cross-section view of a stereoscopic display according to yet still exemplary embodiment. Referring to  FIG. 15 , the stereoscopic display  1001  in this embodiment is similar to the stereoscopic display  100  in  FIG. 1B , and the difference therebetween is as follows. In the stereoscopic display  1001  according to this embodiment, the light converging element  1201  is a lens, for example, a single plane-convex lenticular lens, and the light I provided by the displaying element  110  is a collimated beam, for example, a parallel beam. The light converging element  1201  converges the light I to the view region A 1 , and the scanning element  200  makes the light I scan from view region A 1  through view region A 2  to the view region A 3 . 
       FIG. 16  is a schematic cross-section view of a stereoscopic display according to yet still exemplary embodiment. Referring to  FIG. 16 , the stereoscopic display  100   m  in this embodiment is similar to the stereoscopic display  1001  in  FIG. 15 , and the difference therebetween is as follows. In the stereoscopic display  100   m,  the light converging element  120   m  is a Fresnel lens, which has a reduced thickness smaller than the thickness of the light converging element  1201 . As a result, the overall thickness of the stereoscopic display  100   m  can be reduced. 
       FIG. 17  is a schematic cross-sectional view of the stereoscopic display according to yet still exemplary embodiment. Referring to  FIG. 17 , the stereoscopic display  100   n  of this embodiment is similar to the stereoscopic display  100  shown in  FIG. 1B , and the difference therebetween is as follows. In the stereoscopic display  100   n  of this embodiment, the displaying element  110   n  comprises a backlight module  114  and a display panel  116 . In this embodiment, the backlight module  114  comprises a plurality of linear light sources  115 . The linear light sources  115  may be substantially parallel to the rod-shaped lenticular lenses  122 . Each of the linear light source  115  is, for example, a cold cathode fluorescent lamp (CCFL), a line of light emitting diodes (LEDs), or another light emitting element. Moreover, in this embodiment, the display panel  116  is, for example, a liquid crystal display panel. 
     The light I n  comprises an illumination light B 1  and an image light B 2 . The backlight module  114  is adapted to emit the illumination light B 1 . The display panel  116  is disposed on a transmission path of the illumination light B 1  for converting the illumination light B 1  into the image light B 2 , and the light converging element  120  is disposed on the transmission path of the illumination light B 1  between the backlight module  114  and the display panel  116 . In this embodiment, the scanning element  200  is disposed on the transmission path of the illumination light B 1  between the display panel  116  and the light converging element  120 . However, in other embodiments, the scanning element  200  may also be disposed on a transmission of the image light B 2  between the display panel  116  and the user. 
       FIG. 18A  is a schematic cross-sectional view of the stereoscopic display according to still yet another exemplary embodiment, and  FIG. 18B  is a schematic cross-sectional view of the scanning element in  FIG. 18A . Referring to  FIG. 18A  and 
       FIG. 18B , the stereoscopic display  100   p  of this embodiment is similar to the stereoscopic display  100  in  FIG. 1B , and the difference therebetween is as follows. In the stereoscopic display  100   p  of this embodiment, a light converging element  120   p  comprises a plurality of transparent materials  124   p  respectively disposed on the first material  214  with anisotropic refractive indices, and the interfaces  223  respectively between the first material  214  with anisotropic refractive indices and the transparent materials  214  have different slopes with respect to a displaying surface  111  of the displaying element  110 . In this embodiment, the slopes of the interfaces  223  increase from the center of the light converging element  120   p  to the edges of the light converging element  120   p,  so that the light converging element  120   p  may also converge the light I. In this embodiment, each of the transparent materials  124   p  is disposed between the first electrode  212  and the second electrode  218 . In other words, the converging element  120   p  of this embodiment is combined into the scanning element  200   p,  and the transparent materials  124   p  of the light converging element  120   p  are respectively combined into the scanning units  120   p  of the scanning element  200   p.  Each of the transparent materials  124   p  is, for example, a solid prism, a liquid, or a material with anisotropic refractive indices, and this material with anisotropic refractive indices is, for example, liquid crystal. 
     In view of the above, the stereoscopic display according to the exemplary embodiments has the scanning element using the material with anisotropic refractive indices to make the light scan a plurality of view regions, so that the multi-view images are achieved. Moreover, the operation frequency of the scanning element according to the exemplary embodiments can be lower, so that the stereoscopic display  100  of this embodiment is favorable for mass production, and it has more applicability. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the disclosed embodiments without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the disclosure cover modifications and variations of this disclosure provided they fall within the scope of the following claims and their equivalents.