Abstract:
A display device includes a screen having first and second overlapping lenticular screen structures. The first overlapping lenticular screen structure is a series of columns having a negative slope and the second overlapping lenticular screen structure is another series of columns having a positive slope. The display provide three dimensional views in horizontal and vertical dimensions and maintains three-dimensional capabilities even when viewers tilt their heads.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a three dimensional display device having a lenticular screen structure. 
       BACKGROUND OF THE INVENTION 
       [0002]    Displays having lenticular screens have become one of several different types of stereoscopic devices that are being developed and considered for three dimensional (3D) displays. Typical 3D displays with lenticular screens work well as long as viewers are positioned within certain viewing angles, viewing distances, and viewing orientations with respect to the lenticular screen. The reason is a lenticular screen is a collection of optical lenses that takes advantage of the phenomenon of parallax. In other words, lenticular components guide light from each stripe to each eye correctly for a 3D effect, and therefore each eye has an independent and different picture view. Optimal distance and optimal viewing angle each depend on the lenticular optical properties such as focal length. 
         [0003]      FIG. 5  is a cross sectional view of a conventional lenticular screen  18  where the lenticular lenses  21  run in vertical columns and each vertical column includes a series of left pixels  16  designed to be seen by left eyes  19  and each vertical column includes a series of right pixels  17  designed to be seen by right eyes  20 . In the figure, the viewing distance is optimized by the lenticular component&#39;s optical properties (e.g. focal length) such that the left eye  19  only sees the left pixels  16  and the right eye  20  only sees the right pixels  17 . However, as the viewer moves from the optimized position, a blending of the left and right pixels will begin to occur, thereby diminishing the 3D effect. This is called “cross talk.” 
         [0004]    The lenticular screen  18  has been further improved by constructing the lenticular lenses with liquid crystal material which can change the refractive index of the lenses when the liquid crystal material is poled. Such capability also allows for easy switching between two dimensional (2D) and three dimensional (3D) viewing. However, the position of the viewer is still critical for these lenticular screens with liquid crystal material. 
         [0005]    Another 3D display concept is the parallax display. With this technology, the screen includes a parallax barrier instead of lenticular components in front of the left and right images.  FIGS. 6A and 6B  generally represent a conventional parallax display yielding a vertically interlaced image  11 .  FIG. 6A  shows that the left pixel columns  12  effectively yield the left image  14  and the right pixel columns  13  yield the right image  15 . The viewers who are appropriately positioned with respect to the display will see the left pixel columns  12  with their left eye  19  and see the right pixel columns  13  with their right eye  20 .  FIG. 6B  shows how the parallax barrier  28  generally permits the left eye  19  and the right eye  20  to see the left pixels columns  12  and the right pixel columns  13 , respectively. As with the conventional lenticular displays, if not appropriately positioned, the viewer will see both the left and right columns with both eyes because light delivery is angle sensitive for a certain separation between two eyes. 
         [0006]    There are also other display technologies for 3D viewing. One is the use of passive glasses with polarized light projection. Another is the use active auto-shutter glasses using LCDs. However, it is hard to judge which is better because requirements vary for different applications (e.g., passive methodology is more favored for cinema viewing due to multi-viewing positions and active methodology is typically favored for gaming). 
         [0007]    With the current state of the art in 3D lenticular screen and parallax screen technologies having restrictive viewer positional constraints and the other 3D technologies requiring glasses, a need exists for a novel screen that can broaden the viewing latitude without requiring glasses. 
       SUMMARY OF THE INVENTION 
       [0008]    A display device includes a screen having first and second overlapping lenticular screen structures. The first overlapping lenticular screen structure is a series of columns having a negative slope and the second overlapping lenticular screen structure is another series of columns having a positive slope. The columns in each series are parallel and comprise repeat units of convex lenses. A plurality of the columns in each series crosses columns in the other series, wherein each intersection forms an individual lenticular segment or lens. Each lenticular segment has a peak saggital height at the center and decreasing saggital height as a function of the distance from the center of each lenticular segment. 
         [0009]    Additionally, the lenticular screens can contain liquid crystal material such that the refractive index of the lenticular screens can be controlled, thereby providing the display with easy conversion capability between two dimension (2D) and three dimension (3D) modes and adjustability for suitable viewing latitudes. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The invention will now be described by way of example with reference to the accompanying drawings. 
           [0011]      FIG. 1  is a plan view of the lenticular screen according to the invention. 
           [0012]      FIG. 2  is a cross sectional view of convex lenses of the lenticular screen according to the invention. 
           [0013]      FIG. 3  is a plan view of the pixels of the lenticular screen according to the invention. 
           [0014]      FIG. 4  shows a lenticular screen that includes liquid crystals. 
           [0015]      FIG. 5  is a cross sectional view of a conventional lenticular screen. 
           [0016]      FIG. 6  is a vertically interlaced image for a 3D effect for a conventional parallax screen. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0017]      FIG. 1  shows a plan view localized region of the novel overlapping lenticular screen structure  30  according to the invention. The first overlapping lenticular screen structure  31  is a series of first columns having a first configuration and the second overlapping lenticular screen structure  32  is a series of second columns having a second configuration, which is different than the first configuration. In a preferred embodiment, the first configuration is the first columns having a negative slope  33  and the second configuration is the second columns having a positive slope  34 . The angle between the slope  33  and the vertical axis is shown as angle a in  FIG. 1 . The angle between the slope  34  and the vertical axis is shown as angle −a in  FIG. 1 . Element  40  is a line parallel to the vertical axis Y. The slopes allow for reduction in the distance between viewers, and therefore, they enable the display to have more viewers in a given viewing angle. The columns in each series are generally parallel. A plurality of the columns in each series cross columns in the other series. In  FIG. 1 , each intersection of the columns of screen structure  31 ,  32  comprise repeat units of parallelograms defined by low saggital height points  38 . These repeat units are lenticular segments or lens  43 . In these repeat units, the low saggital height points  38  surround low sagittal height regions  37 , the low sagittal height regions  37  surround medium sagital height regions  36 , and medium sagitial height regions  36  surround high sagittal height regions  35 . Each lenticular segment has a peak point (or region)  39  at the center and decreasing saggital height as a function of the distance from the center of each lenticular segment. This means that the value of the height H decreases with increasing dimension from the center of each lenticular segment. In a preferred embodiment, the low saggital height points have the same saggital position. 
         [0018]      FIG. 2  more clearly shows the profile of the overlapping lenticular screen structures  30 ,  31  and the nature of the lenticular lenses  43  in  FIG. 1 .  FIG. 2  shows a peak point  39  of height H in a high sagittal height region  35 , a medium sagittal height region  36 , a low sagittal height region  37  and low saggital height points  38 . Height H is the saggital drop of any point in the lenticular segment to the lowest lying point in the lenticular segment.  FIG. 2  shows height H for the peak point  39  to the low saggital height points  38 .  FIG. 2  further shows how the height for each portion or point of the overlapping lenticular screen structures  30 ,  31  varies as a function of the distance from the center of each lenticular segment, wherein the value of the height H decreases with increasing dimension from the center of each lenticular segment  43 . 
         [0019]      FIG. 3  shows how the individual pixels of the screens are defined. Four specific pixels  51 ,  52 ,  53 ,  54  are defined within lenticular lenses or lenticular segments  43 . A lens or lenticular segment  43  is the common space between the low saggital height points  38  where two adjacent columns of the first overlapping screen structure  31  of positive slope  33  traverse two adjacent columns of second screen structure  32  of negative slope  34 . The lenticular segment  43  is a region that is generally a parallelogram or rhombus-shaped. Specifically, the four pixels are contained within a lenticular segment by a vertical demarcation line  41  (which runs through the upper and lower points of intersection of the low saggital height points  38 ) and a horizontal demarcation line  41  (which runs through the far left and far right points of intersection of the low saggital height points  38 ). The pixels are specifically the upper left pixel  51 , the lower left pixel  53 , the upper right pixel  52  and the lower right pixel  54 . The upper left pixel  51  and the lower left pixel  53  are designed to be seen by left eyes of the viewers and the upper right pixel  52  and the lower right pixel  54  are designed to be seen by the right eyes of the viewers. In addition, high frequency of 4-pixel control enables the display to perform 3D vertically and horizontally, while conventional lenticular technology is limited to a horizontal 3D effect. 
         [0020]    With the novel lenticular screen provided in  FIG. 1 , viewers can move such as by tilting sideways and yet still perceive a 3D effect. With the conventional lenticular screen, viewers who tilt their heads can lose the 3D effect due to cross talk between eyes. 
         [0021]    Additionally, the lenticular screens can contain liquid crystal material such that the refractive index of the lenticular screens can be controlled, thereby providing the display with easy conversion capability between 2D and 3D modes and adjustability of suitable viewing distances.  FIG. 4  shows how the lenticular screen that includes liquid crystal operates.  FIG. 4A  shows the case where the liquid crystal is poled, wherein the left eye  19  will see the upper left pixels  51  and the right eye  20  will see the upper right pixels  52 . However, if the liquid crystal is not poled as shown in  FIG. 4B , the left eye  19  and the right eye  20  will see the both the upper left pixels  51  and upper right pixels  52 . 
         [0022]    The foregoing illustrates only some of the possibilities for practicing the invention. Many other embodiments are possible within the scope and spirit of the invention. It is, therefore, intended that the foregoing description be regarded as illustrative rather than limiting, and that the scope of the invention is given by the appended claims together with their full range of equivalents.