Patent Publication Number: US-2011069394-A1

Title: Lens array image

Description:
FIELD OF THE INVENTION 
     This invention relates in general to electrographic printing, and more particularly to printing of raised toner to form one or more optical elements by electrography. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to images incorporating a lens array. It finds particular application in conjunction with printing an image, incorporating a lens array, on a multi-planar or curved surface and will be described with particular reference thereto. It will be appreciated, however, that the invention is also amenable to other applications. 
     Lens array images include motion images, lenticular images, and integral images. One embodiment of a motion image includes a non-planar (e.g., folded) substrate having two images, with alternating narrow segments of each image printed side by side. This type of motion image is also referred to as a folded image. A lenticular image includes a planar substrate with interdigitated segments of at least two images adjacent a lens array that focuses on a first image at a first viewing angle and focuses on a second image at a second viewing angle. An integral image includes an array of spherical lenses, each having a separate, single image representing the light that would be projected to an observer from a location in the array so that a 3-D display is created. 
     Although motion (folded) images produce good separation between images, the images may be difficult to produce and handle during manufacturing. Additionally, the width of the image segments used in folded images must be larger than a width of a crease in the image segment (e.g., approximately the thickness of the substrate). Folded images are commonly limited to containing two interdigitated images. 
     Separation between interdigitated segments of lenticular images depends on a first image being in focus when viewed from a first viewing angle and a second image being out of focus when viewed from the first viewing angle. At a second viewing angle, the second image is in focus and the first image is out of focus. However, the second image may be out of focus at all viewing angles unless complicated lens profiles are used. Also, in a lenticular image, when viewing a first image from a first viewing angle, a portion of the second image may be visible. Therefore, lenticular images often include non-distinct separations between the interdigitated segments of the images. Lens arrays used in lenticular imaging may be made mechanically, such as by molding, extrusion or cutting processes. The lenses in the array are usually wide to accommodate mechanical forming and are necessarily thick. Image segments are typically wide to accommodate wide lenses and some misregistration. Therefore, the segments of the first image are often multiple pixels wide, with the second image being similarly sized. In addition, the first and second images must be registered with the lens array. 
     Integral images may have similar issues as lenticular images. For example, an integral image may be in focus from a first viewing angle, but out of focus from a second viewing angle. 
     The present invention provides a new and improved apparatus and method which addresses the above-referenced problems. 
     SUMMARY OF THE INVENTION 
     In one aspect of the present invention, a lens array image includes a substrate, a first lens on a first side of the substrate, and a second lens on the first side of the substrate. The first and second lenses form a lens array. Respective first image segments are at the second side of the substrate. Each of the first image segments is in focus when viewed from a first viewing angle through a respective one of the first and second lenses. Respective second image segments are at a second side of the substrate. Each of the second image segments is in focus when viewed from a second viewing angle through a respective one of the first and second lenses. At least a portion of each of the first image segments is on a first plane. At least a portion of the respective second image segments is on a second plane. The first plane is different than the second plane. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings which are incorporated in and constitute a part of the specification, embodiments of the invention are illustrated, which, together with a general description of the invention given above, and the detailed description given below, serve to exemplify the embodiments of this invention. 
         FIG. 1  illustrates a schematic view of a lens array in accordance with several embodiments of an apparatus illustrating principles of the present invention; 
         FIG. 2  illustrates a schematic view of at least one image printed on parallel planes that intersect or are tangent to loci of foci of the lens array in accordance with one embodiment of an apparatus illustrating principles of the present invention; 
         FIG. 3  illustrates a schematic view of at least one image printed on planes tangent to the loci of foci of the lens array in accordance with one embodiment of an apparatus illustrating principles of the present invention; 
         FIG. 4  illustrates a schematic view of at least one image printed on a curved surface substantially in alignment with loci of foci of the lens array in accordance with one embodiment of an apparatus illustrating principles of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Motion images are made using non-planar substrates. A common embodiment is a folded image made of a sheet of paper containing two images, with alternating narrow segments of each image printed side by side. The sheet is folded at the edge of each image portion in an alternating concave-convex-concave (et cetera) fashion to produce a folded image so that a first image is seen when the sheet is viewed from the left at a first viewing angle, and a second image is seen only when the sheet is viewed from the right at a second viewing angle. 
     Lenticular images are made with a planar substrate containing interdigitated segments of at least two and optionally three or more images adjacent a lens array that focuses on a first image at a first viewing angle and focuses on a second image at a second viewing angle. Usually, the first image is visible primarily at a first viewing angle that is 90 degrees or normal to the lens array. The second image is visible primarily at a second viewing angle that is perhaps 30 degrees from normal. Other configurations are possible. For example, the first image can be visible at an angle 15 degrees from normal, and the second image can be visible at an angle −15 degrees from normal. The lenses in the array can be cylindrical lenses that focus on a line or spherical lenses that focus on a dot. Lenses of elliptical cross-section have been used to improve the focus of lenticular images. 
     Integral images are made with an array of spherical lenses, each having a separate, single image representing the light that would be projected to the observer from that location in the array so that a 3-D display is created. 
     With reference to  FIG. 1 , a lens array  100 , which is illustrated in cross section, includes a plurality of lenses  200 . It is contemplated that the lenses  200  in the array  100  are cylindrical or spherical shaped. Each lens  200  has a first (upper) surface  210 , a center portion  212 , a radius (R 1 )  214 , a second (lower) surface  215 , and a loci of foci  220  with radius (R 2 )  224 . In the illustrated embodiment, the second (lower) surface  215  is between the first surface  210  and the loci of foci  220 . Alternatively, the second (lower) surface  215  may intersect the loci of foci  220  on at least one point. In one embodiment, at least one image  230  (e.g., a color image) is printed on multiplanar or curved surfaces that are registered with the loci of foci and intersect or are tangent to the loci of foci on at least one point in the image so that, for example, either: surfaces  300  and  310  intersect or are tangent to the loci of foci, or cross the loci of foci; surfaces  320 ,  330 , and  340  are tangent to the loci of foci; or surface  350  is curved and substantially in alignment with the loci of foci. In one embodiment, the surfaces  300 ,  310 ,  320 ,  330 ,  340 , and  350  are on a separation layer of toner (e.g., a separation layer of transparent or clear tone), and the at least one image consists of colored toner optionally including a backing layer  380  of another color (e.g., white) or clear toner, as discussed in more detail below. In the illustrated embodiment, a backing layer  380  of white or clear toner is included on the lens array  100 . 
     The focal length of a spherical or cylindrical lens  200  is found by simple ray tracing with Snell&#39;s law and is well known to be a distance L from the outer surface of the lens, where: 
     
       
         
           
             
               
                 
                   L 
                   = 
                   
                     
                       R 
                       1 
                     
                      
                     
                       
                         n 
                         2 
                       
                       
                         
                           n 
                           2 
                         
                         - 
                         
                           n 
                           1 
                         
                       
                     
                   
                 
               
               
                 
                   Eq 
                   . 
                   
                       
                   
                    
                   1 
                 
               
             
           
         
       
     
     and n 2  is the index of refraction of the lens material, n 1  is the index of refraction of the medium (e.g., air) adjacent the first or upper surface  210  of the lens and outside the lens, and R 1  is the radius of the lens array  214  at the point where the ray enters the lens. In  FIG. 1 , the focal length L is the distance from the upper surface of the lens  210  along a radius R 1  through the center  212  and then along a radius R 2  to the loci of foci  220 . 
     Electrophotographic printers containing at least 4 or 5 print units and capable of printing a layer of clear toner are known as discussed in US2009/0016757 and incorporated by reference. It is contemplated that a digital printer capable of 6 colors (e.g., including cyan, magenta, yellow, black, clear, and white) could also be used in one embodiment; alternatively a printer capable of duplex printing with excellent registration could be used for printing images in another embodiment of the present invention. It is also contemplated in that embodiment, the printer could print a first side of the substrate with at least 2 passes through the printer, and similarly also print a second side of the substrate. 
     In the embodiments shown in  FIG. 2 ,  FIG. 3 , and  FIG. 4 , for example, a lens array image  230  includes a substrate  500 , a first lens  200  on a first side of the substrate  500 , and a second lens  200  on the first side of the substrate  500 . For ease of understanding, the embodiments illustrated in  FIG. 2 ,  FIG. 3 , and  FIG. 4 , like components are designated by like numerals. The first and second lenses  200  form the lens array  100 . Respective second image segments  230   b  are positioned at a second side of the substrate  500 . Each of the second image segments  230   b  is in focus when viewed from a second viewing angle  430  through a respective one of the first and second lenses  200 . Respective first image segments  230   a  are positioned at the second side of the substrate  500 . Each of the first image segments  230   a  is in focus when viewed from a first viewing angle  400  through a respective one of the first and second lenses  200 . At least a portion of each of the first image segments  230   a  is on a first plane  310 ,  320 ,  350 , and at least a portion of the respective second image segments  230   b  is on a second plane  300 ,  330 ,  340 ,  350 . The first plane  310 ,  320 ,  350  is different than the second plane  300 ,  330 ,  340 ,  350 . With reference to  FIG. 4 , although the surface  350  is curved, different portions of the curved surface  350  may be viewed as defining respective planes. More specifically, a small portion of the curved surface  350  may be viewed as defining a plane. In that sense, at least a portion of each of the first image segments  230   a  is on a first plane  350  (e.g., a first portion of the surface  350  that defines a plane), and at least a portion of the respective second image segments  230   b  is on a second plane  350  (e.g., a second portion of the surface  350  that defines a plane). 
     Various examples are illustrated in  FIG. 2 ,  FIG. 3 , and  FIG. 4 . The illustrated examples assume a pixel size of 42.33 microns corresponding to 600 dpi resolution, a first viewing direction  400  normal to the lens array ±15 degrees, and a second viewing direction  430  30 degrees from normal ±15 degrees, for images and lenses printed on the substrate  500  (e.g., a transparent polyester substrate) with toner (e.g., polyester toner). For ease of understanding the embodiments illustrated in  FIG. 2 ,  FIG. 3 , and  FIG. 4 , like components are designated by like numerals in those figures. The index of refraction n 2  is approximately 1.55 for polyester, and n 1  in this example is taken to be 1. Dimensions for an image made with a lens approximately 3×3 pixels in size, 5×5 pixels, or 7×7 pixels are shown in Table 1. The width of the lens  200  corresponds in these examples to a maximum range in viewing angle of ±45 degrees from normal; however, a larger or smaller range of viewing angle is also contemplated. In these examples, L=R 1 +R 2 =R 1 ×2.81818 . . . . The sum of the lens height, substrate thickness, and total thickness of a clear layer  240  must equal L, where the clear layer  240  is between the outer first surface of the lens  210  and the most distant of the at least one image  230  (e.g.,  230   a ). The numbers in Table 1 were obtained using Equation 1 and simple trigonometry, corresponding to the general geometries of  FIG. 2 ,  FIG. 3 , and  FIG. 4 . The examples shown in  FIG. 2 ,  FIG. 3 , and  FIG. 4  specifically correspond to the first line of Table 1, which is for lenses of 3×3 pixels at 600 dpi resolution, as explained above. 
     
       
         
           
               
               
               
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                   
                   
                   
                 Lens 
                   
                 Clear 
               
               
                   
                   
                   
                   
                   
                 height 
                 Substrate 
                 layer 
               
               
                   
                   
                   
                   
                   
                 above 
                 thickness 
                 thickness 
               
               
                 Lens 
                 Width 
                 L 
                 R 1   
                 R 2   
                 substrate 
                 (min) 
                 (max) 
               
               
                 (pixels) 
                 (microns) 
                 (microns) 
                 (microns) 
                 (microns) 
                 (microns) 
                 (microns) 
                 (microns) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 3 × 3 
                 127.0 
                 253.1 
                 89.8 
                 163.3 
                 26.3 
                 179.0 
                 47.8 
               
               
                 4 × 4 
                 169.3 
                 337.4 
                 119.7 
                 217.7 
                 35.1 
                 238.6 
                 63.8 
               
               
                 5 × 5 
                 211.7 
                 421.8 
                 149.7 
                 272.1 
                 43.8 
                 298.3 
                 79.7 
               
               
                   
               
            
           
         
       
     
     In one embodiment of the invention, as shown in  FIG. 2 , a second image  230   b  is printed on the flat plane  300  on a second (lower) side of a transparent substrate  500  and covered with the layer of clear toner  240  upon which a first image  230   a  is printed. In this example, lens  200  is 26.3 microns in height, as shown in Table 1. If the second image as shown in  FIG. 2  is at the intersection of loci of foci  220  and the line of sight  430  for the viewing angle of 30 degrees, the thickness of the clear toner layer is approximately R 2 −R 2  cos(30)=21.9 microns and the thickness of the transparent substrate is L−26.3−21.9=204.9 microns. The lens array  100  is printed on the first (upper) side of substrate  500 . 
     The image shown in  FIG. 2  may be printed by a 5, 6 or more color prints by the following process. Image  230   b  is printed on a second side of a transparent substrate  500 . In this case, image  230   b  can consist of 3 or 4 color separations or other similar separations that may use a gray scale, optionally followed by a white separation  232   b , and flat, parallel surface  300  will be immediately adjacent substrate  500 . A clear toner layer  240  is printed on image  230   b  and the second side of transparent substrate  500 . The image is fused and the substrate with the image is passed through the printer a second time. Image  230   a  is printed on the flat, parallel surface  310  of the clear toner layer  240 , optionally with a backing layer of white toner  232   a  applied to image  230   a , and the image is fused. Image  230   a  is primarily viewed along line of sight  400  and image  230   b  is primarily viewed along line of sight  430 . In the illustrated embodiment, the image  230   b  is substantially parallel to the image  230   a . Image  230   a  can significantly overlap image  230   b  and white toner layer  232   a  can overlap both image  230   a  and  230   b . The substrate with the image is passed through the printer a third time, and the lens array  100  is printed in register with the at least one color image  230   a  and  230   b . Optionally, a white or neutral color toner layer  102  is printed between lenses  200 , and the image is fused. A backing layer  380  of clear, white, gray or another neutral color can also be added and fused. 
     In an alternate embodiment, an additional layer of clear toner (not shown) is deposited on the substrate, and the image (e.g.,  230   b  is printed on that additional layer of toner). 
     In another embodiment of the invention, as shown in  FIG. 3 , a layer of clear toner  240  is printed on a second (lower) side of transparent substrate  500 . Layer  240  contains the surfaces  320 ,  330 , and  340  that are tangent to loci of foci  220 . At least one image  230  is printed on these surfaces. For example, image  230   a  is printed on surface  320 , image  230   b  is printed on surface  340 , and so forth. In this example, lens  200  is 26.3 microns in height, as shown in Table 1. To accommodate the full range of viewing angle ±45 degrees from normal, where normal is shown as line of sight  400 , the maximum thickness of the clear toner layer  240  is approximately R 2 −R 2  cos(45)=47.8 microns and the thickness of the transparent substrate is approximately L−26.3−47.8=179.0 microns. The lens array  100  is printed on the first (upper) side of substrate  500 . 
     The image shown in  FIG. 3  may be printed by a 5, 6, or more color printer according to the following process. Clear toner layer  240 , which varies in thickness in this example, as shown in  FIG. 3 , is printed on a second side of a transparent substrate  500 . The at least one color image  230  is printed on the approximately flat tangent surfaces  320 ,  330 , and  340  of clear toner layer  240 . For example, image  230   b  can consist of 3 or 4 color separations, or other similar separations that may use a gray scale, optionally followed by a white separation  232   b  printed on surface  340 , which is tangent to loci of foci  220 . The clear toner layer  240 , image  230   a , image  230   b , and so forth may be printed in one pass through the printer, and can have individual white backing layers or a single white backing layer  232   a , as shown in  FIG. 3 . The image is fused and the substrate with the image is passed through the printer a second time. The lens array  100  is printed in register with the at least one color image  230   a  and  230   b ). Optionally, a white or neutral color toner layer  102  is printed between lenses  200 , and the image is fused. A backing layer  380  of clear, white, gray or another neutral color may also be added and fused. Image  230   a  is primarily viewed along line of sight  400  and image  230   b  is primarily viewed along line of sight  430 . Image  230   a  may abut image  230   b  and white toner layer  232   a  may overlap both image  230   a  and  230   b.    
     In another embodiment of the invention, as shown in  FIG. 4 , a layer of clear toner  240  is printed on a second (lower) side of transparent substrate  500 . Layer  240  contains the surface  350  that is a curved surface essentially congruent to loci of foci  220 . At least one image  230  is printed on surface  350 . For example, image  230   a  is printed on a portion of surface  350  and image  230   b  is printed on an adjacent section of surface  350 , and so forth. In this example, lens  200  is 26.3 microns in height, as shown in Table 1. To accommodate the full range of viewing angle ±45 degrees from normal, where normal is shown as line of sight  400 , the maximum thickness of the clear toner layer  240  is approximately R 2 −R 2  cos(45)=47.8 microns and the thickness of the transparent substrate is approximately L−26.3−47.8=179.0 microns. The lens array  100  is printed on the first (upper) side of substrate  500 . 
     The image shown in  FIG. 4  may be printed by a 5, 6, or more color printer according to the following process. Clear toner layer  240 , which varies in thickness in this example, as shown in  FIG. 4 , is printed on a second side of a transparent substrate  500 . The at least one color image  230  is printed on the curved surface  350  of clear toner layer  240 . For example, image  230   b  may consist of 3 or 4 color separations, or other similar separations that may use a gray scale, optionally followed by a white separation  232   b  (not shown) printed on surface  350 , which is congruent to loci of foci  220 . The clear toner layer  240 , image  230   a , image  230   b , and so forth may be printed in one pass through the printer, and may have individual white backing layers (not shown) or a single white backing layer  232   a , as shown in  FIG. 4 . The image is fused and the substrate with the image is passed through the printer a second time. The lens array  100  is printed in register with the at least one color image  230 , or  230   a  and  230   b . Optionally, a white or neutral color toner layer  102  is printed between lenses  200 , and the image is fused. A backing layer  380  of clear, white, gray or another neutral color may also be added and fused. Image  230   a  is primarily viewed along line of sight  400  and image  230   b  is primarily viewed along line of sight  430 . Image  230   a  may abut image  230   b  or be a continuation of image  230   b  to make a single image, and white toner layer  232   a  may overlap both image  230   a  and  230   b.    
     In  FIG. 2 ,  FIG. 3 , and  FIG. 4  the at least one color image  230  may consist of two or more separate images that are each observable when viewed from distinct viewing angles, two or more related images that form a motion image that appears to move when viewed from different, distinct viewing angles, and portions of an image that makes a single 3-D image when viewed through lens array  100 . The separate images may be an image and its magnification, text in two or more different languages, two or more different scenic views on a postcard, two different frames of a cartoon, or any two or more related or unrelated images that are desired. The separate images can also be similar images that produce an image with a 3-D effect when viewed. 
     The embodiments of the invention described above may be used with a preformed lens array, or a pre-formed backing layer onto which a lens array is printed. Although the embodiments of the invention discussed above are described in connection with printing on a single transparent substrate, it is to be understood that other embodiments including multiple sheets of transparent substrate laminated together are also contemplated. 
     For example, for  FIG. 2 , second image(s)  230   b  and  232   b  (if desired) are printed on a second (lower) side of a first transparent substrate  500  which contains lens array  100  on its first (upper) side. First image(s)  230   a  and  232   a  (if desired) are printed on the second (lower) side of a second transparent substrate that is used instead of clear toner layer  240 . The first transparent substrate and the second transparent substrate are co-joined and laminated. Although good registration is required for the lens array and the second image, requirements for registration of the first image and the second image on the opposite side of the first transparent substrate are significantly less stringent. In particular, the second image  230   b  and first image  230   a  may overlap. This method enables the use of small lenses in the lens array that are only a few pixels wide. 
     In one embodiment, a method of producing a lens array image includes applying a first image on a second side of a substrate (at least a portion the first image is on a first plane), applying a second image on the second side of the substrate (at least a portion the second image is on a second plane, which is different than the first plane), applying a first lens to a first side of the substrate, and applying a second lens to the first side of the substrate. The first image is in focus when viewed from a first viewing angle through a respective one of the first and second lenses. The second image is in focus when viewed from a second viewing angle through a respective one of the first and second lenses. In one embodiment, the first plane intersects a first location of a plurality of loci of foci, and the second plane intersects or is tangent to a second location of the plurality of loci of foci. 
     A first toner (e.g., a clear toner) layer is applied on the second image and the substrate. The first image is applied to the first toner layer. In the illustrated embodiment, applying the first image includes applying four color separations on the clear first toner layer, and applying the second image includes applying four color separations on the second side of the substrate. A separation layer is applied on a side opposite of a side of the second image applied to the substrate. A backing layer is applied on a side opposite of a side of the first image applied to the clear first toner layer. A second toner layer is applied on the first side of the substrate between lenses of the array. A backing layer is applied on one of the images. 
     In another embodiment, a clear toner layer is applied to the second side of the substrate. A toner layer may also be applied on the first image, the second image, and the substrate. Respective separation layers are also applied to at least one of the first image and the second image. 
     While the present invention has been illustrated by the description of embodiments thereof, and while the embodiments have been described in considerable detail, it is not the intention of the applicants to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention, in its broader aspects, is not limited to the specific details, the representative apparatus, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of the applicant&#39;s general inventive concept. 
     The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.