Abstract:
The invention provides a display unit for displaying two or more consecutively changing images, the unit including a curved lenticular panel having front and rear faces; a displaceable, lightweight, image-carrying film spread out along the rear face; an electric drive coupled to the film for periodically displacing the film across the lenses of the panel, and guide means facilitating the smooth reciprocating movement of the film.

Description:
FIELD OF THE INVENTION 
     The present invention relates to display units, and particularly to display units that exhibit two or more consecutively changing images to be viewed by a viewer. 
     BACKGROUND OF THE INVENTION 
     Multiple image display devices of various kinds are known; among them are those comprising lenticular lenses in array with multi-dimensional lithographs moving in parallel planes. Such displays are described in U.S. Pat. No. 5,100,300 (Sediguchi) and U.S. Pat. No. 5,488,451 (Goggins), and also in U.S. patent application Ser. No. 09/248,318. The devices described in these documents relate basically to small-sized units, mainly for indoor use. These devices, however, prove to be inadequate for large-sized displays such as outdoor billboards. 
     The basic optical principles of these devices require an accurate positioning of the linear lenses in juxtaposition with the lithographic film. When large-sized displays are involved, such accuracy cannot be adequately achieved. Thermal changes and inconsistencies of printing processes are the main causes of such a drawback. U.S. Pat. 5,146,703 (Boden) and others tried to overcome this difficulty, but the fact that billboards based on the aforementioned optic principle are not in commercial use, suggests that an adequate device has not yet been devised. 
     Japanese Patent 0211437 (Kumagai) discloses a large-sized display having a cylindrical lens group, a framed body which supports an image carrier constituted of a transparent printing positive, and a light source at its rear face. The image processing of such a system imposes accurate positioning of the image carrier in close juxtaposition with the lenticular panel. Such conditions are achieved by the Kumagai device, which utilizes a rigid frame sliding along mechanical guide means disposed at a constant spacing from the lens group. Thus, an expensive and complicated solution is proposed, which also has its limitations regarding size and accuracy relationships between the lithographic prints and the lenses. 
     SUMMARY OF THE INVENTION 
     It is the object of the present invention to provide a display unit which ameliorates the above-described disadvantages of the prior art devices. It is a further object of the present invention to provide a low-cost display unit having disposable lithographic film of a large size disposed in close juxtaposition to the lenticular panel at an accurate distance from the lenses, for achieving a clear display of the images printed on the film, including changing images and stereoscopic animation. 
     It is a still further object of the present invention to provide a custom-made display unit consisting of only two fundamental parts: a lenticular panel and a lithographic film, without requiring a rear panel or frame, the unit being configured to be integrated into a custom-made platform of any shape or a light-box of any size, and which can also advantageously serve as a stand-alone product at points of sale, without connection to the electrical mains. 
     A yet further object of the invention is to provide a large-sized display unit for outdoor use that is capable of functioning in changing conditions of temperature and despite inaccuracies of the printing process. 
     In accordance with the present invention, there is therefore provided a display unit for displaying two or more consecutively changing images, said unit comprising a curved lenticular panel having front and rear faces; a displaceable, lightweight, image-carrying film spread out along said rear face; an electric drive coupled to said film for periodically displacing the film across the lenses of said panel, and guide means facilitating the smooth reciprocating movement of said film. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described in connection with certain preferred embodiments with reference to the following illustrative figures so that it may be more fully understood. 
     With specific reference now to the figures in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice. 
     In the drawings: 
     FIG. 1 is a rear view of a display unit according to the present invention; 
     FIG. 2 is a front view of the display unit of FIG. 1; 
     FIG. 3 is an enlarged, cross-sectional view of a portion of the display unit along lines III—III of FIG. 1; 
     FIG. 4 is a perspective view of a large-sized display unit according to the present invention; 
     FIG. 5 is an enlarged, cross-sectional view of the display unit along lines V—V of FIG. 4; 
     FIGS. 6 and 7 illustrate lateral portions of a display unit furnished with means for controlling thermal expansion; 
     FIGS. 8 and 9 are schematic, optical representations of the present invention; 
     FIG. 10 is a block diagram illustrating a method of forming an image-carrying film utilizable with the display unit of the present invention; 
     FIG. 11 is a schematic representation illustrating considerations for forming an image-carrying film for large-sized display units; 
     FIGS. 12 and 13 illustrate different embodiments of the invention, and 
     FIGS. 14 and 15 respectively depict the front and back views of a still further embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIGS. 1 and 2 illustrate front and back views of a display unit for exhibiting two or more consecutively changing images. Seen is a lenticular panel  1  composed of cylindrical lenses  2  on its front side and ribs  4  on its back side. Panel  1  is slightly arched in a direction perpendicular to the axes of the lenses. A light-weight film  6  is spread out on the convex back side of panel  1  (FIG. 1) and is coupled thereto by means of, e.g., four springs  8  attached at one of their ends to pins  10  connecting rulers  12  across the upper and lower edges of film  6 , and at their other ends to pins  14  anchored adjacent to the upper and lower corners of panel  1 . Each of the upper and lower rulers  12  is provided with a tab  16  having a slot  18 , through which penetrates a further pin  20  affixed to panel  1 . The combination of slot  18  and pin  20  forms a guide means for film  6 , assuring its accurate movement along panel  1 . 
     The movement of film  6  is effected by a high-efficiency electric motor  22  powered by batteries  24 . The motor  22  rotates a cam  26  (FIG.  3 ), connecting its rotating movement to the linear movement of film  6 . For illustration, on the front side of the panel  1  is displayed an image of the letter A (FIG.  2 ). The display unit can be hung from a ceiling by means of rods or wires  28 , or otherwise, a custom-made unit can be incorporated into an existing display frame. 
     Referring to FIGS. 4 and 5, there is illustrated a display unit configured as a large billboard. Seen is a metallic frame  30  forming a support for a panel  1 , and an array of lamps  32 , e.g., fluorescent lamps, disposed behind panel  1  and film  6 . The film  6  is coupled at its upper and lower edges to rollers  34 ,  36 . The lower roller  36  is tensioned by means of a spring  38  connected to the base of frame  30 . The upper roller  34  is coupled to a stepping motor  40  by means of, e.g., a belt  42 , for transmitting a controlled, stepwise movement to the film. 
     Referring to FIGS. 6 and 7, there are illustrated the front and back lateral portions of, e.g., the billboard unit of FIG.  4 . In order to assure proper alignment between the film  6  and the lenses  2  in panel  1  under changing temperatures or, in other words, in order to assure the same thermal expansion of both the lenses  2  and the film  6 —there are provided metal profiles having the same thermal expansion coefficient, as follows: Panel  1  is composed of a multiplicity of identical transparent panel modules  44 , each having a rib  46  projecting towards the film  6 . Modules  44  are affixed to the billboard frame profile  50  by rivets or screws  52  spaced equidistant from each other, for example at a distance S. Similarly, film  6  is provided with holes spaced apart at the same distance S facilitating its attachment to profiles  53  by means of pins  54 . Several profiles may be attached to film  6  for large billboards. An enlarged portion of the panel  1  and film  6  of FIGS. 1 and 2 is illustrated in FIG.  8 . Seen are the cylindrical lenses  2  spaced apart from film  6  by means of ribs  4  projecting between two adjacent cylindrical lenses. The lithographic printing on the film is composed of an array of strips A, B and C, constituting frames  56  having an overall modular dimension M, which is substantially equal to the width of a single lens and the images produced on the lens by the three strips A, B and C. The distance d between the film  6  and a lens  2  will be fx⅔, wherein f is the focal length of the lens  2 . The relationship between the focal length f of the lenses  2  and the frames  56  is further explained with reference to FIG.  9 . Strips A, B and C carry information in a compressed form. Whenever, e.g., strip B is positioned behind a lens  2 , the compressed information is magnified to its non-compressed size. 
     The compression of the images can be achieved by the process shown in FIGS. 10 and 11.  1 n the first step  1 , three basic images A, B and C are entered into a computer&#39;s memory. Each image has a vertical dimension of L/3. In the next step II, the images are stripped into N independent frames, wherein N also constitutes the number of lenses in the lenticular panel  1 . In step III, the individual strips are interlaced to form a file having the dimension L=A+B+C. The file is then compressed (step IV) by a factor K calculated according to the number of the stripped basic images N, the size of the lenses M, the distance d of the film  6  from the lenses  2 , and the radii of curvature R of the lenses. In order to calculate such a factor K of a planar lenticular panel, it is sufficient to divide by the number of images, i.e.,          K   =     1   3       ,                          
     namely, the film should be compressed by 33⅓%. 
     A curved or arched panel, however, requires further compression. Strip B (FIG.  11 ), which is located at the lower edge of a lens  2  at the upper portion of the panel  1 , must be shifted towards the axis of curvature  58  of the panel near its central portion. Each of the strips B should accordingly be shifted so that the line of sight which is parallel to the axis  58  of the panel will meet the strip B in each lens of the panel. The amount of shifting Δx is calculated as follows:          Δ                 x     =         M   N        d       2      R                              
     where M N  is the vertical dimension of the lenticular panel compression factor=         K   =         M   N     -     Δ                 x         3        M   N           ;                          
     and for three images,          K   =       1   3          (     1   -     d     2      R         )         ;                          
     for P images,        K   =       1   P            (     1   -     d     2      R         )     .                              
     After compression (FIG.  10 ), the operator may wish to view the results of the compression for approval or correction, and that is effected in step V, on a suitable monitor. The interlaced and compressed lithography can now be printed on a film (step VI). 
     Three-dimensional images on film  6  can also be utilized with the display units according to the present invention. Such three-dimensional films can be produced in accordance with the description in, e.g., U.S. Pat. No. 5,436,738, or others. 
     In FIG. 12 there is illustrated a modification of the display unit of FIGS. 1 to  5 , in which three-dimensional images can be displayed. The display unit includes an arched panel  1  having vertically extending linear lenses  2  supporting a film  6  stretched along the tips of ribs  4 . The film  6  is rolled along its vertically extending lateral edges, to be moved in controlled steps in a horizontal direction. 
     A further possible modification of the invention is presented in FIG. 13 Instead of the panel  1  having cylindrical lenses  2 , the invention can be embodied in a panel having an array of microprisms  60  which are embossed on the rear face  62  of the panel. Each array of microprisms  60  represents a linear lens of a modular dimension M. The dimensions of the panel, calculated according to Fresnel principles, provide a thin, light-weight, flat screen. The film  6  is spaced apart from the rear side of the panel by means of ribs  4 , to be slid there across by means of the roller  34  and roller  36  (not shown), similar to the movement of the film  6  according to FIGS. 4 and 5. 
     Turning now to FIGS. 14 and 15, there is illustrated a still further embodiment of the invention in which the curvature of the panel is along the axis of the cylindrical lenses  2 . The light-weight film  6  is retained across the rear face of the panel  1  by means of two laterally extending guides  64 , which may be constituted by bent portions integrally formed as lateral channels with panel  1  as shown in FIG.  15 . The film  6  is freely supported at its bottom edge on a shelf  66  movable about an axis  68 . Shelf  66  is provided, at its lower surface, with a member  70  suitably configured to be coupled at its free end to a cam  72 , rotatable by a drive  74  powered from a battery  76 . 
     It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrated embodiments and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.