Abstract:
This invention is a device for displaying three-dimensional images using an array of tilting microcolumns. It can create high-resolution, large-scale, moving, three-dimensional images that can be viewed by people in different locations, with full parallax, without special eyewear. Unlike currently available methods, this invention: does not require special eyewear, works for multiple viewers, provides parallax in all directions, does not have a very restrictive viewing zone, does not produce only transparent images, does not require coherent light, is scalable to large displays, does not require liquid movement to adjust lens shape, and does not require complex systems to individually control large numbers of lenses.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application claims the priority benefit of provisional patent application Ser. No. 61/011,200 entitled “System for displaying three-dimensional video images” filed on Jan. 16, 2008 by Robert A. Connor of Holovisions LLC. 
    
    
     FEDERALLY SPONSORED RESEARCH 
     Not Applicable 
     SEQUENCE LISTING OR PROGRAM 
     Not Applicable 
     BACKGROUND 
     1. Field of Invention 
     This invention relates to the display of three-dimensional images. 
     2. Background and Related Art 
     Currently, there are four general approaches to displaying three-dimensional images: (1) methods requiring special eyewear; (2) methods using three-dimensional display surfaces; (3) methods using holography; and (4) methods using parallax barriers and lenses. 
     (1) Special Eyewear 
     Several methods of three-dimensional imaging require special eyewear. The eyewear presents different images to a viewer&#39;s right and left eyes. Such methods involving only two different images are generally called “stereoscopic.” Many eyewear-based methods have a common source for right and left eye images, but the two different images are differentiated by two different types of lenses on the eyewear. For example, the lenses may differ by color, polarization, or sequential shutters. Other eyewear-based methods involve two different sources for right and left eye images, such as two independent mini-screens close to the eyes. 
     Disadvantages of special eyewear methods include: the inconvenience of having to wear special eyewear; the lack of multiple perspectives, occlusion, and image shifting in response to viewer movement; and eye strain or damage from conflicting convergence vs. accommodation cues that stress the human visual system. Lack of multiple perspectives, occlusion, and response to image shifting in response to viewer movement can be partially addressed by adding systems that track viewer motion, but these are also inconvenient and are difficult to apply in multi-viewer situations. 
     (2) Three-Dimensional Display Surfaces 
     Several methods of three-dimensional imaging use display surfaces that are themselves three-dimensional. Variations in these display surfaces include whether these surfaces are “full-scale” (on the same scale as displayed images) or “micro-scale” (on the same scale as pixels comprising the displayed images), whether these surfaces are stationary or moving, and whether these surfaces emit or reflect light. 
     Full-scale three-dimensional display surfaces are generally called “volumetric.” Stationary volumetric displays often include a series of parallel two-dimensional panels whose transparency can be varied. These panels emit or reflect light to create two-dimensional image slices which, when viewed together, form a three-dimensional image. Less commonly, a translucent gel can be used. Moving volumetric displays often have a spinning (or otherwise cyclically moving) two-dimensional structure that emits or reflects light. The light paths formed as its light emitting or reflecting members sweep through space create a three-dimensional image. Disadvantages of full-scale three-dimensional display surfaces include: they are cumbersome to construct and use for large-scale images with multiple viewers; and displays with transparent or translucent members produce transparent ghost-like images that are not desirable for many purposes. 
     Micro-scale three-dimensional display surfaces are less well-developed than full-scale surfaces and do not yet have a commonly-used label, but can be thought of as “three-dimensional pixels.” In theory, the concept of a three-dimensional pixel is a pixel comprised of an array of sub-pixels, each with image directionality as well as image content. Three-dimensional pixels could be in the form of a cube, sphere, or other shape. The concept of three-dimensional pixels has potential, but entails significant technical and practical challenges that have not yet been resolved. It is very challenging to create an extremely small structure with a sufficient number of fixed radiating “sub-pixels” to produce an image with reasonable resolution from different perspectives. Also, even if such structures of multiple “sub-pixels” can be created, it is very challenging to get them sufficiently close together for image precision without one structure blocking views of an adjacent structure. If the reader will pardon a colorful analogy, it is like trying to design a city block full of several-story apartment buildings wherein people in each apartment all want a view of the river; it is tough to do. 
     (3) Holographic Animation 
     Holographic animation has tremendous potential, but is still at an early stage with many technical challenges yet unresolved. Current systems for animated holographic imaging produce relatively small translucent images with limited viewing zones and poor image resolution. They also require coherent light with associated expense and safety concerns. Some day holographic animation may become the method of choice for three-dimensional imaging, but thus far it remains very limited. 
     (4) Parallax Barriers and Lenses 
     There are many methods of three-dimensional imaging using parallax barriers, lenticular lenses, fly&#39;s eye lenses, variable focal-length lenses, and combinations thereof. 
     Parallax barriers allow different images to reach a viewer&#39;s right and left eyes by selectively blocking portions of images, generally via a layer that is close to the image surface. Light-blocking vertical strips and light-transmitting vertical slits are often used as parallax barriers. Some parallax barriers are stationary. Other parallax barriers move in response to viewer head motion in systems that track this motion. Lenticular lenses are (semi-circular) columnar lenses. They are generally combined in vertical arrays near an image surface. Lenticular lenses direct different views (generally vertical image strips) to a viewer&#39;s right and left eyes. Parallax barriers and lenticular lenses can be used together. 
     Lenticular lenses and parallax slits only provide parallax in one direction. Some parallax in another direction can be achieved by adding a viewer head tracking system and varying image content to reflect viewer head motion, but this is cumbersome for one viewer and problematic for multi-viewer applications. Another disadvantage of parallax barriers and lenticular systems are “pseudoscopic” images outside a severely-restricted viewing zone. “Pseudoscopic” views occur when the images that the eyes see are improperly reversed. “Pseudoscopic” views can cause eye strain, headaches, and other health problems. 
     A “fly&#39;s eye” lens is an array of convex lenses. Three-dimensional imaging using a fly&#39;s eye lens is called “integral photography.” A fly&#39;s eye lens can display a large number of small two-dimensional images from different perspectives. Ideally, as a viewer moves, the viewer sees the same point from different perspectives. Although this concept has considerable potential, it involves significant practical challenges. It is difficult to have a sufficient number of two-dimensional images to achieve high image resolution on a very small scale structure. Viewing zones remain limited. Production of fly&#39;s eye screens is also relatively expensive. 
     New methods have also been proposed for creating three-dimensional images using lenses whose focal lengths can be changed in real time. Such lenses include electro-wetting controlled droplet lenses and liquid-crystal microlenses. Lenses whose focal lengths can be changed are called “dynamic” or “active” lenses. Although application of such lenses to the creation of three-dimensional images has considerable potential, there remain many technical challenges. Systems to independently adjust the focal lengths of a large number of microlenses are complex. Liquids may not move sufficiently rapidly to adjust focal length fast enough for three-dimensional viewing. Viewing zones remain limited. 
     (5) Summary of Background and Related Art 
     To summarize the related art, considerable work has been devoted to create ways to display three-dimensional images. However, all of the current methods still have disadvantages. Some methods require inconvenient eyewear and cause eye strain. Some methods require viewer tracking that is inconvenient and does not work well for multiple viewers. Some methods have restrictive viewing zones. Some methods produce transparent, ghost-like images. Some methods produce very small, low-resolution images and require use of coherent light. Some methods have significant unresolved technical challenges concerning the creation of complex microstructures. Some methods do not adjust rapidly enough to display moving three-dimensional images. None of the current methods provide a practical means to create high-resolution, large-scale, moving, three-dimensional images that can be viewed by people in different locations, with full parallax, without special eyewear. The invention disclosed herein addresses these disadvantages. 
     SUMMARY 
     This invention is a device for displaying three-dimensional images that comprises an image display surface (wherein this image display surface emits or reflects light to display an image comprised of multiple small image elements such as pixels) and an array of tilting microcolumns (wherein the image contents displayed by small image elements are coordinated with the movement of the tilting microcolumns, through which those image contents pass, to form a pattern of light rays with the proper content and directionality so as to create perception of three-dimensional images). 
     This invention provides a novel and practical means to create high-resolution, large-scale, moving, three-dimensional images that can be viewed by people in different locations, with full parallax, without special eyewear. Unlike currently available methods, this invention: does not require special eyewear, works for multiple viewers, provides parallax in all directions, does not have a very restrictive viewing zone, does not produce only transparent images, does not require coherent light, is scalable to large displays, does not require liquid movement to adjust lens shape, and does not require complex systems to individually control large numbers of lenses. 
    
    
     
       DRAWINGS 
       Introduction 
         FIGS. 1 through 14  show some examples of how an array of tilting microcolumns can be used to display three-dimensional images. They do not limit the full generalizability of the claims. The claims can be applied in many other examples. 
         FIGS. 1 and 2  provide an introductory perspective on what is required to have a two-dimensional image display surface that creates the perception of three-dimensional images, with full parallax, when viewed by people in different locations. 
         FIG. 1  shows a top-down perspective of an actual cube being seen by two viewers. Specific details are shown for the lines-of-sight from two points on that cube to the eyes of the two viewers.  FIG. 2  shows a top-down perspective of a three-dimensional image of a virtual cube based on the actual cube, or at least two points thereof. Perception of those two points on the virtual cube is accomplished by recreating the original image display elements along the original lines-of-sight for the actual points on the actual cube. To reduce clutter in these figures, details are only shown for two points on the cube. However, the concepts apply to other points on the cube. A display system that is able to faithfully display these two points in three-dimensions would be able to display the entire virtual cube in three-dimensions. 
         FIGS. 3 through 8  show a top-down cross-sectional perspective of one example of how an array of tilting microcolumns can redirect light rays from small image elements on a display surface along different lines-of-sight.  FIGS. 3 through 6  show a moving series wherein the array of tilting microcolumns tilts to display the content of different small image elements along different lines-of-sight (exiting the image display surface at different angles).  FIGS. 7 and 8  show how this device can display different content from different lines-of-sight from the same small image element. 
         FIGS. 9 and 10  show an oblique perspective of an array of tilting microcolumns with hexagonal cross-sections that are held together by a moving honeycomb structure, as the structure tilts up and down.  FIG. 11  shows this same honeycomb-style array, as the structure moves in a circle. 
         FIG. 12  focuses on one hexagonal microcolumn of a hexagonal array (the total array is not shown) as the microcolumn tilts around in a spiral path.  FIG. 13  focuses on one hexagonal microcolumn of a hexagonal array (the total array is not shown) as the microcolumn tilts back and forth in a zig-zag path.  FIG. 14  shows one example of how the microcolumns may be tilted mechanically. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1 through 14  show some examples of how three-dimensional imaging may be achieved by using an array of tilting microcolumns. However, they do not limit the full generalizability of the claims given later. Many other examples and variations may be created based on the claims. 
       FIGS. 1 and 2  provide a conceptual introduction to what types of image elements and light beam directions are required in order to have a two-dimensional surface create the appearance of three-dimensional images, with full parallax, when viewed by people in different locations. In this example, the phrase “small image element” refers to a pixel. In other examples, the term “small image element” could be one of a different type of small image element, wherein these small elements are combined to form an overall image. The creation of two-dimensional images only requires small image elements with image content (such as image color and intensity) and two-dimensional location (such as location in a two-dimensional array). The creation of three-dimensional images from a generally two-dimensional display surface requires small image elements to have appropriate line-of-sight directionality (e.g. display angle) as well as content and two-dimensional location. Creating three-dimensional images from a generally two-dimensional display surface often requires different content to be viewed from the same point from different angles. 
       FIG. 1  shows a top-down perspective of two sample points, point  102  (also labeled “A”) and point  103  (also labeled “B”), on actual cube  101  which is seen by two viewers in different locations. One viewer is represented by that viewer&#39;s right eye  104  (also labeled “C”) and left eye  105  (also labeled “D”). A second viewer is represented by that viewer&#39;s right eye  106  (also labeled “E”) and left eye  107  (also labeled “F”). 
     To avoid the clutter of showing lines-of-sight from all of the points on the cube to all four viewer eyes,  FIG. 1  shows line-of-sight detail for only the two points,  102  (A) and  103  (B). However the concepts also apply to creating images of a large number of points on the cube. A system that can faithfully recreate eight points of view for two points on the cube can do so for many other points on the entire cube.  FIG. 1  shows the eight lines-of-sight, from each of the two points to each of the four eyes. Each line-of-sight is labeled according the directional path of the light ray, starting with the lower-case letter of the originating point (a or b) on the cube and ending with the letter of the receiving eye (c,d,e, or f). For example, the line-of-sight from point “A” to eye “C” is labeled “a→c”. 
     In  FIG. 2 , there is no longer an actual cube. Instead, there is a three-dimensional image of a virtual cube as perceived by the two viewers. To be precise, to reduce diagram clutter  FIG. 2  only shows the lines-of-sight required to create perception of two points,  202  (A) and  203  (B). It does not show all lines-of-sight for the entire virtual cube  201 . However, as mentioned earlier, the general concepts could be applied to many points on the cube so as to create a three-dimensional image of the entire virtual cube  201 . Accordingly, as a conceptual introduction to the overall imaging process, the entire virtual cube  201  is shown in  FIG. 2 . 
     In the example shown in  FIG. 2 , several image display points, including point  109 , are shown along a cross-section of two-dimensional image display surface  108 . From these image display points, the eight original lines-of-sight radiate outwards from the two-dimensional surface toward the viewers at the appropriate angles. This creates three-dimensional perception of points  202  (A) and  203  (B) on virtual cube  201 . The means by which these image elements are created and these lines-of-sight are directed along different angles is not specified here in  FIG. 2 , but it is specified in figures that follow.  FIG. 2  is intended to provide a conceptual introduction to what is needed, in terms of display content and lines-of-sight, to create three dimensional images. This sets the stage and provides context for the specific examples in the figures that follow. 
       FIGS. 3 through 8  show a top-down cross-sectional perspective of one example of how an array of tilting microcolumns provides the ability to control the lines-of-sight for passage of light rays from small image elements on the display surface. In this example, each tilting microcolumn allows passage of light rays along different lines-of-sight from the same small image element on a display surface, allowing the perception of different content when the small image element is viewed from different directions. This allows three-dimensional imaging, with full parallax, from people in different locations. 
       FIGS. 3 through 6  show a progressive sequence wherein the array of tilting microcolumns is tilting to display the content of different small image elements along different lines-of-sight (exiting the image display surface at different angles).  FIG. 3  shows a top-down cross-sectional perspective of an array of small image elements (including  302 ,  303 ,  304 , and  305 ), individually enclosed by an array of tilting microcolumns (including  306 ,  307 ,  308 , and  309 ) that are attached via swiveling means to display surface  301 . 
     In the example shown in  FIG. 3 , the small image elements ( 302 ,  303 ,  304 , or  305 ) are Light Emitting Diodes (LEDs). In other examples, the small image elements may be different types of light-emitting elements (such as points on a back-lit screen) or light-reflecting elements (such as points on a front-lit screen or mirror). There are many methods in the prior art by which images can be recorded and reproduced in two-dimensional arrays, so they are not specified here. 
     In the example shown in  FIG. 3 , the tilting microcolumns ( 306 ,  307 ,  308 , and  309 ) are hollow cylindrical columns with: opaque walls; a rounded and closed end that encloses a small image element ( 302 ,  303 ,  304 , or  305 , respectively) and is attached via a swiveling means to display surface  301 ; and an open end facing away from the display surface  301  out of which light from the small image element exits along a particular line-of-sight. In another example, tilting microcolumns  306 ,  307 ,  308 , and  309  could be made from a solid transparent substance such as glass, crystal, or polymer. In another example, tilting microcolumns  306 ,  307 ,  308  and  309  could be hollow hexagonal columns with shared opaque walls made from flexible, stretchable material. 
     In  FIG. 3 , image content concerning cube point “B” along line of sight “b→c” is displayed by small image element  303  and passes through the hollow longitudinal axis of microcolumn  307  toward eye  104  (C). This recreates the original “b→c” line-of-sight. In  FIG. 4 , the array of tilting microcolumns have tilted slightly so that microcolumn  308 , which encapsulates small image element  304 , is properly angled to direct content concerning cube point “B” along line-of-sight “b→d” towards eye  105  (D). In  FIG. 5 , the tilting continues. In  FIG. 5 , the array has tilted further so that microcolumn  306  is now properly angled to direct content concerning cube point “A” along line-of-sight “a→c” from small image element  302  towards eye  104  (C). In  FIG. 6 , the tilting continues and now microcolumn  309  is properly angled to direct content concerning cube point “B” along line-of-sight “b→e” from small image element  305  towards eye  106  (E). 
       FIGS. 3 through 6  just demonstrated how an array of tilting microcolumns can direct content from different small image elements along different lines-of-sight.  FIGS. 7 and 8  now demonstrate how an array of tilting microcolumns can also direct content from the same small image element along different lines-of-sight. This is important for creating three-dimensional images. In  FIG. 7 , the tilt of microcolumn  307  allows it to display and direct content concerning cube point “B” along line-of-sight “b→c” from small image element  303  towards eye  104  (C). In  FIG. 8 , this same column has been tilted so as to allow it to display and direct content concerning cube point “A” along line-of-sight “a→e” from the same small image element towards eye  106  (E). 
     When the tilting motion is sufficiently rapid, and the image display is properly coordinated with the tilting motion, then both images are viewed virtually simultaneously due to image persistence in human visual processing. The ability of this device to display different images from the same small image element when viewed from different directions allows perception of three-dimensional images, with full parallax, by people in different positions. 
       FIGS. 9 and 10  show an oblique perspective of an example of an array of tilting microcolumns with hexagonal cross-sections that are held together by a moving honeycomb structure. The hexagonal structure is shown tilting up and down in  FIGS. 9 and 10 . In this example, the tilting microcolumns are hollow hexagonal columns with shared opaque walls made from flexible, stretchable material. Specifically, in  FIG. 9 , the end of one microcolumn  901  that is closest to the image display surface is a hexagon. This hexagonal end  901  encloses small image element  902  on the image display surface. In this example, small image element  902  is an LED. In this example, the walls of this microcolumn  903  are opaque stretchable material and the microcolumns share walls with each other. The microcolumns in this example are hollow. The end  904  of this microcolumn facing away from the image display surface is also a hexagon. 
     The end  904  of this microcolumn is joined with the ends of other microcolumns in the array to form a moveable honeycomb structure that is generally parallel to the image display surface. In this example, the honeycomb surface can be kept relatively parallel to the image display surface even when it moves due to the stretchability of the microcolumn walls. In this example, if the microcolumn walls did not stretch, then the honeycomb structure could not be freely moved and stay parallel with the image display surface.  FIGS. 9 and 10  provide an oblique view of how this array of tilting microcolumns would look as the outer honeycomb structure moves up and down in a plane parallel to the image display surface, tilting the microcolumns up and down in the process. 
     In the simple cross-sectional perspectives shown thus far, the array of tilting microcolumns is shown with the ends of the columns facing away from the image surface being tilted in just a one-dimensional linear manner. If the tilting motion were restricted to such one-dimensional linear movement, then the device would not create full three-dimensional viewing and parallax in all directions. The lines-of-sight from the small image elements would fan out into space in flat planes. However, the ends of the columns facing away from the image surface can be can be moved in two-dimensional patterns, including circles, spirals, squares, and zig-zag patterns. With such two-dimensional patterns, the lines-of-sight from the small image elements fan out into space in three-dimensions. In this manner, full three-dimensional viewing and parallax can be achieved in all directions. This is a significant advantage over methods in the prior art that use vertical slits and only offer horizontal parallax. 
       FIG. 11  shows the same honeycomb array of tilting microcolumns shown in  FIGS. 9-10 , but now the structure is shown moving in a two-dimensional path. Specifically, the two-dimensional path is a circle. 
       FIG. 12  focuses on one hexagonal microcolumn of a hexagonal array as the microcolumn tilts around in a spiral path  1206 . Although this one hexagonal microcolumn is part of an array, the entire array is not shown to more clearly focus on the motion of a single column. All the other columns in the array would be moving in tandem with this one. Specifically,  FIG. 12  shows one hexagonal end  1202  of the tilting microcolumn enclosing small image element  1201 . In this example, the walls  1203  of the hexagonal tilting microcolumn are opaque and stretchable. The microcolumn is hollow. The end  1204  facing away from the image display surface is also a hexagon and is part of an outer honeycomb structure with the ends of other microcolumns that is not shown in this figure for the sake of reducing image clutter. In this example, the end  1204  of the microcolumn traces out a cyclical (in, then out, then in, then out) spiral path as the microcolumn tilts. In this manner, the line-of-sight  1205  from small image element, passing through the longitudinal axis of the microcolumn, traces out an expanding cone of light into the viewing space. Within this cone of light, people in different locations can see different content from the same point on the display surface. This creates three-dimensional images, with full parallax, without the need for special glasses. 
       FIG. 13  focuses on the same hexagonal microcolumn shown in  FIG. 12 , but in this example the microcolumn tilts in a zig-zag pattern  1301 . In this manner, the line-of-sight  1205  from small image element, passing through the longitudinal axis of the microcolumn, traces out an expanding square-base-pyramid of light into the viewing space. Within this pyramid of light, people in different locations can see different content from the same point on the display surface. This creates three-dimensional images, with full parallax, without the need for special glasses. 
     Thus far, we have shown microcolumns tilting along various paths, but have not specified what makes them tilt. There are a number of ways by which the microcolumns can be tilted.  FIG. 14  shows one example of how they may be tilted by moving a honeycomb structure  1401  that connects all the microcolumn ends that face away from the image display surface. This honeycomb structure is moved in a plane that is generally parallel to the image display surface. In this example, there is also a second honeycomb structure  1402  that connects all the microcolumn ends that face toward the image display surface. In this example, this second honeycomb structure is stationary. With the ends of the microcolumns facing away from the image display surface being moved and the ends of the microcolumns facing toward the image display surface being stationary, the microcolumns all go through cyclical tilting motions. 
     In this example, the honeycomb structure  1401  farther away from the image display surface is moved in a two-dimensional path by its attachment to two rods ( 1403  and  1405 ) which are, in turn, attached to rotating wheels  1404  and  1406 , which may be driven by electric motors. In another variation on this example, the microcolumns may be tilted by MEMS (Micro Electrical Mechanical Systems). In an alternative to direct mechanical tilting means, the array of tilting microcolumns may be moved in a two-dimensional pattern by changes in a surrounding electromagnetic field. A combination of mechanical and electromagnetically-induced tilting is also possible.