Abstract:
Disclosed is a display element that includes a display screen and a transparent cover overlying the display screen. The output from the display screen is magnified to occupy at least some of the transparent cover. The display element includes an arrangement of diffractive and refractive elements disposed between the display screen and the transparent cover that provide significant magnification without adding significant thickness to the display element. In some embodiments, the diffractive and refractive elements are embodied in a number of optical microelements, in some cases at least one optical microelement per pixel of the display screen. Some embodiments include microlenses that collimate the light emitted by the display screen. The display element can be “anamorphotic,” that is, the magnification in one direction differs from that in another. Some embodiments provide at least two levels of magnification. Liquid matching switches can be used to control the level of magnification.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention is related generally to electronic hardware and, more particularly, to computer displays. 
       BACKGROUND OF THE INVENTION 
       [0002]    Portable personal electronics devices (e.g., cell phones, personal digital assistants, portable computers) are running increasingly complex applications. These applications often need to display increasingly complex information to their users. Larger display screens can, of course, present complex information more clearly than can small screens. 
         [0003]    However, larger display screens cost more than smaller ones, use more power, and take up more volume in the portable device. Thus, the simple solution of providing larger display screens conflicts with the desire to make these portable devices both smaller and cheaper. 
         [0004]    Many portable devices include, as part of their housing, a transparent cover that overlies and protects the display screen itself. This transparent cover often extends beyond the edges of the display screen. Attempts have been made to magnify the size of the display produced by the display screen until the display occupies some of the larger area provided by the transparent cover. However, these attempts have only been able to provide a useful amount of magnification when there is a significant distance between the surface of the display screen and the inner surface of the transparent cover. Providing that distance runs counter to another important desire among users, that is, the desire for these devices to be ever thinner as well as smaller. 
       BRIEF SUMMARY 
       [0005]    The above considerations, and others, are addressed by the present invention, which can be understood by referring to the specification, drawings, and claims. According to aspects of the present invention, a display element includes a display screen and a transparent cover overlying the display screen. The output from the display screen is magnified to occupy at least some of the transparent cover. The display element includes an arrangement of diffractive and refractive elements disposed between the display screen and the transparent cover that provide significant magnification without adding significant thickness to the display element. The display element can be used in personal electronic devices such as cellular telephones, personal digital assistants, and personal computers. 
         [0006]    In some embodiments, the diffractive and refractive elements are embodied in a number of optical microelements, in some cases at least one optical microelement per pixel of the display screen. These optical microelements can be formed by known microlithographic techniques. 
         [0007]    Some embodiments include microlenses among the optical microelements. Each microlens collimates the light emitted by one pixel of the display screen. 
         [0008]    In some embodiments, the degree of magnification produced by the display element is the same in all directions. In other embodiments, the display element is built to be “anamorphotic,” that is, the magnification in one direction differs from that in another. 
         [0009]    Some embodiments provide at least two levels of magnification (e.g., one level of no magnification and one level of positive magnification). Liquid matching switches can be used to control the level of magnification. Switching between magnification levels can be put under the direct control of a user. In some cases, software running on the user&#39;s electronic device (e.g., an operating system utility or a user application) can set the level of magnification as appropriate for the information currently being displayed. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0010]    While the appended claims set forth the features of the present invention with particularity, the invention, together with its objects and advantages, may be best understood from the following detailed description taken in conjunction with the accompanying drawings of which: 
           [0011]      FIGS. 1   a  and  1   b  are schematics of a personal electronics device in which the present invention may be embodied; 
           [0012]      FIGS. 2   a  and  2   b  are cross-sections of a display element showing a normal (non-magnified) display and a magnified display; 
           [0013]      FIG. 3  is a cross-section of a magnifying display element that uses diffractive and refractive elements according to an embodiment of the present invention; 
           [0014]      FIG. 4  is a cross-section of a magnifying display element with collimating microlenses; and 
           [0015]      FIG. 5  is a cross-section of a magnifying display element that includes liquid matching switches in order to switch among states of magnification (or among one state of non-magnification and one or more states of varying levels of magnification). 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    Turning to the drawings, wherein like reference numerals refer to like elements, the invention is illustrated as being implemented in a suitable environment. The following description is based on embodiments of the invention and should not be taken as limiting the invention with regard to alternative embodiments that are not explicitly described herein. 
         [0017]      FIGS. 1   a  and  1   b  show a personal electronics device  100  (e.g., a cellular telephone, personal digital assistant, or personal computer) that incorporates an embodiment of the present invention.  FIGS. 1   a  and  1   b  show the device  100  as a cellular telephone with its cover open. When open, the cover presents a display element  102  to a user of the device  100 . The display element  102  includes a main display screen  104  and a substantially transparent cover  106  that overlays and protects the main display screen  104 . Importantly for the present invention, the transparent cover  106  extends beyond the edges of the main display screen  104 . 
         [0018]    Typically, the main display screen  104  is used for most high-fidelity interactions with the user of the personal electronics device  100 . For example, the main display screen  104  is used to show video or still images, is part of a user interface for changing configuration settings, and is used for viewing call logs and contact lists. To support these interactions, the main display screen  104  is of high resolution and is as large as can be comfortably accommodated in the device  100 . In some embodiments, the device  100  may have a second and possibly a third display screen for presenting status messages. These screens are generally smaller than the main display screen  104 . They can be safely ignored for the remainder of the present discussion. 
         [0019]    The typical user interface of the personal electronics device  100  includes, in addition to the main display screen  104 , a keypad  108  or other user-input devices. (If the main display screen  104  is a touch screen, then it is both an output device and a user-input device.) 
         [0020]      FIG. 1   b  illustrates some of the more important internal components of the personal electronics device  100 . Most devices  100  include a communications transceiver  110 , a processor  112 , and a memory  114 . Other necessary or useful components (e.g., a battery or other power supply) are well known in the art but are not important to the present discussion and are therefore not depicted in the figures. 
         [0021]      FIG. 2   a  is a simplified cross-sectional view of a display screen  104  and its overlaying transparent cover  106  as known in the prior art. The display screen  104  includes light-emitting pixels  200 . (For purposes of clarity,  FIG. 2   a  only shows a one-dimensional array of five pixels  200 . As is well known, actual display screens  104  can have two-dimensional arrays of pixels  200  with each dimension measuring several hundred pixels in extent.) The light emitted from each pixel  200  in the display screen  104  goes directly “up” to and through the transparent cover  106  where it is perceived by a user of the personal electronics device  100 . The result is that the image seen by the user looking at the transparent cover  106  is of the same size as the array of pixels  200  of the display screen  104 . 
         [0022]    In comparison with  FIG. 2   a ,  FIG. 2   b  shows a result achieved by embodiments of the present invention. In  FIG. 2   b , the image produced by the light emitted from the pixels  200  of the display screen  104  is magnified when viewed through the transparent cover  106 . This is accomplished by angularly shifting the light emitted by each pixel  200  in the display screen  104  before the light reaches the transparent cover  106 . Note the regular spacing of the pixel light on the transparent cover  106 . This regularity allows the image to be magnified without being distorted. To achieve this regularity, the angles of the light shift from the display screen  104  to the transparent cover  106  are not all the same. For example, light from the middle pixel  200  goes straight “up” as before, while light from pixels  200  farther and farther from the center goes through greater and greater angular shifts. 
         [0023]    (As noted above in reference to  FIG. 2   a , the array of pixels  200  in  FIG. 2   b  is actually two-dimensional. Thus, the angular shift required for each pixel  200  in the array is determined by the pixel&#39;s position in both the X- and Y-dimensions of the array. This is simple geometry.) 
         [0024]    Several possible ways of achieving the angular shifts of  FIG. 2   b  are contemplated. For example, an optical fiber can be run from each pixel  200  in the display screen  104  to the desired position of that pixel&#39;s light on the transparent cover  106 . Alternatively, an array of micro-lenses or micro-mirrors (one per pixel  200 ) can be positioned between the display screen  104  and the transparent cover  106  to shift the light. For each pixel  200 , the micro-lens or micro-mirror is configured to provide just the right amount of angular shift for that pixel  200 . These approaches have shortcomings, however. In particular, they can only achieve a significant amount of magnification if the separation between the “top” of the display screen  104  and the “bottom” of the transparent cover  106  is also significant. In the interests of clarity,  FIGS. 2   a ,  2   b , and the following figures are not drawn to scale. In actuality, to achieve a desired thinness in the personal electronics device  100 , this separation is kept very small in comparison with the width of the display screen  104 . Therefore, embodiments using the approaches listed in this paragraph usually cannot achieve significant magnification given the constraint of maintaining a small separation between the display screen  104  and the transparent cover  106 . 
         [0025]    Preferred embodiments of the present invention overcome these limitations and thus achieve a significant magnification without a significant increase in the separation distance.  FIGS. 3 through 5  illustrate these preferred embodiments. 
         [0026]    In  FIG. 3 , arrays  300 ,  302  of optical microelements  304 ,  306  are disposed between the display screen  104  and the transparent cover  106 . Rather than the micro-lenses or micro-mirrors discussed above, the optical microelements  304 ,  306  comprise diffractive and refractive elements to provide the appropriate angular shift for each pixel  200 . The path of the light emitted by the left-most pixel  200  in  FIG. 3  shows how this embodiment combines diffraction, total internal reflection, and refraction to move the light from its originating pixel  200  in the display screen  104  to the position on the transparent cover  106  appropriate to create a clear, magnified image. 
         [0027]    The arrays  300 ,  302  of optical microelements  304 ,  306  can be manufactured by known techniques such as microlithography or micromachining. The arrays  300 ,  302  can be instantiated as diffractive gratings. While  FIG. 3  shows four distinct “layers” (i.e., the display screen  104 , the two arrays  300 ,  302  of optical microelements  304 ,  306 , and the transparent cover  106 ), in some embodiments the manufacturing can be simplified by combining two or more of these “layers” into a single layer. The separation shown between the arrays  300 ,  302  can be an air gap in some embodiments and need not exist at all in other embodiments. 
         [0028]    As discussed above with reference to micro-lenses and micro-mirrors, the diffractive and refractive microelements  304 ,  306  are configured for each specific pixel  200  to generate the magnified image. Because each set of microelements  304 ,  306  is specially configured for one pixel  200 , it is an easy matter to create the arrays  300 ,  302  to accommodate a specific disposition of the transparent cover  106 . For example, the arrays  300 ,  302  can be created for a transparent cover  106  with a curved rather than a flat surface. 
         [0029]    The regular spacing of the light positions on the transparent cover  106  is discussed above. In some embodiments, the spacing along one axis of the transparent cover  106  differs from the spacing along the other axis. When this spacing difference is created by the magnification apparatus  300 ,  302 , the magnification is termed “anamorphotic.” 
         [0030]      FIG. 4  shows an optional refinement useful in some embodiments of the present invention. As is well known, diffraction and refraction angles depend upon the wavelengths and incident angles of incoming of light. Thus, light emitted by one pixel  200  may end up at slightly different places, or at slightly different angles, on the transparent cover  106 . To compensate for this, an array of microlenses  400  is added to collimate the light. These microlenses can be manufactured in a separate layer or combined with other elements into a unified layer and may be formed by known micro-manufacturing techniques. 
         [0031]    Another option is shown in  FIG. 5 . An array  500  of liquid matching switches  502  is added. These switches  500  have at least two states, and the states are distinguished from one another by how much they angularly shift the light coming through them. In the illustrative, but probably unrealistic, view of  FIG. 5 , the two liquid matching switches  502  on the right are set for no magnification (as in  FIG. 2   a ), while the two liquid matching switches  502  on the left are set for a normal level of magnification (as in  FIG. 3 ). Usually, of course, all of the liquid matching switches  502  are set to the same state. Because the liquid matching switches  502  are under the control of the processor  112  of the personal electronics device  100 , the device  100  can switch among its states of magnification, typically one state being of no magnification at all, and the other states being of varying amounts of magnification up to the greatest amount of magnification compatible with the configuration of the transparent cover  106 . 
         [0032]    In some embodiments, the switching between magnification states is under the direct control of a user of the personal electronics device  100 . The processor  112  can also choose the magnification state based on, for example, the particular information being displayed on the display element  102 . Some user applications or operating system utilities may have preferences for whether or not their information is magnified. 
         [0033]    In view of the many possible embodiments to which the principles of the present invention may be applied, it should be recognized that the embodiments described herein with respect to the drawing figures are meant to be illustrative only and should not be taken as limiting the scope of the invention. For example, various elements shown separately may be combined for ease of manufacturing. Therefore, the invention as described herein contemplates all such embodiments as may come within the scope of the following claims and equivalents thereof.