Abstract:
An image display device may include a fiber optic plate. The fiber optic plate may comprise a plurality of parallel optical fibers, the terminal ends of the optical fibers combining to define a light input surface and an at least partially concave light output surface. 
     An apparatus may include: a fiber optic plate; and a mechanism for affixing the fiber optic plate to a display device. 
     A method for manufacturing a fiber optic plate may include: computing one or more viewing angles between one or more elements of an image display and a focal point; and shaping a fiber optic plate output surface according to the one or more viewing angles.

Description:
BACKGROUND 
     Many modern displays seek to maximize the field of view available to users. However, certain situations may require the limiting the field of view of light emitted by such displays. For example, it may be desirable to limit the field of view for privacy reasons or in order to minimize extraneous reflection of the emitted light by a surrounding environment. 
     Particularly, reflections due to avionics displays may be a major hindrance to pilots operating aircraft equipped with wraparound canopies. Various solutions have been proposed to reduce such reflections. Such solutions may include privacy films and optical wedges. However, privacy films may reduce the transmittance of the associated display. Optical wedges may only control reflections in one direction and also reduce the transmittance of the associated display. 
     As such, it may be desirable to provide an apparatus for limiting the field of view of a display while retaining the transmittance of the displayed images. 
     SUMMARY 
     An image display device may include a fiber optic plate. The fiber optic plate may comprise a plurality of parallel optical fibers, the terminal ends of the optical fibers combining to define a light input surface and an at least partially concave light output surface. 
     An apparatus may include: a fiber optic plate; and a mechanism for affixing the fiber optic plate to a display device. 
     A method for manufacturing a fiber optic plate may include: computing one or more viewing angles between one or more elements of an image display and a focal point; and shaping a fiber optic plate output surface according to the one or more viewing angles. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure will become more fully understood from the following detailed description, taken in conjunction with the accompanying drawings, wherein like reference numerals refer to like elements, in which Figure Reference No: 
         FIG. 1  illustrates a field of view for an image display device. 
         FIG. 2  illustrates a field of view for an image display device. 
         FIG. 3  illustrates a perspective view of a fiber optic plate. 
         FIG. 4  illustrates a top view of a fiber optic plate. 
         FIG. 5  illustrates a side view of a fiber optic plate. 
         FIG. 6  illustrates a cross-sectional view of a fiber optic plate. 
         FIG. 7  illustrates a top view of a fiber optic plate. 
         FIG. 8  illustrates a side view of a fiber optic plate. 
         FIG. 9  illustrates a cross-sectional view of a fiber optic plate. 
         FIG. 10  the orientation of the optical axis of light emitted by a bias-cut optical fiber. 
         FIG. 11  the orientation of the optical axis and cone of light emitted by several bias-cut optical fibers. 
         FIG. 12  an operational environment of a fiber optic plate. 
         FIG. 13  an operational environment of a fiber optic plate. 
         FIG. 14A  illustrates an image display device. 
         FIG. 14B  illustrates an image display device. 
     
    
    
     DETAILED DESCRIPTION 
     Before describing in detail the particular improved system and method, it should be observed that the invention may include, but may be not limited to a novel structural combination of conventional data/signal processing components and circuits, and not in the particular detailed configurations thereof. Accordingly, the structure, methods, functions, control and arrangement of conventional components, software, and circuits have, for the most part, been illustrated in the drawings by readily understandable block representations and schematic diagrams, in order not to obscure the disclosure with structural details which will be readily apparent to those skilled in the art, having the benefit of the description herein. Further, the invention may be not limited to the particular embodiments depicted in the exemplary diagrams, but should be construed in accordance with the language in the claims. 
     The field of view of a display device may be correlated to a half cone angle of a display element. For example, as shown in  FIG. 1 , when viewed by a user  100  at a distance of 24 inches, an 11-inch diagonal display  101  will require a half cone angle of approximately 10° so that a user  100  may view image elements near the edge of the display  101 . Such a half cone angle will result in a limited amount of extraneous light being transmitted outside the field of view of a user where it may contact environmental surfaces resulting in reflections. Specifically, if a reflective surface (e.g. a cockpit canopy) is greater than approximately 10 inches from a centerline axis  102  of the display  101  at a distance of more than 24 inches from the display  101 , any reflections will be transmitted behind the user  100 . 
     However, as shown in  FIG. 2 , when viewed by a user  100  at a distance of 24 inches, a 22-inch diagonal display  103  will require a half cone angle of approximately 20° in order for the user  100  to view image elements near the edge of the display  103 . Such a half cone angle will result in a greater amount of extraneous light being transmitted outside the field of view of a user where it may contact environmental surfaces resulting in reflections. Specifically, a reflective surface (e.g. a cockpit canopy) may need to be greater than approximately 20 inches from a centerline axis  104  of the display  103  to avoid reflections being transmitted to the user  100 . Such distances may be impractical due to spatial constraints of the environment in which the display is to be employed (e.g. a cockpit canopy). 
     Referring to  FIGS. 3-9 , various representations of a fiber optic plate  200  is shown. The fiber optic plate  200  may serve to reduce the amount of extraneous light produced by an image display device transmitted outside the field of view of a user in order to minimize the potential for reflections from the surrounding environment. 
     Referring to  FIGS. 4-5  the fiber optic plate  200  may be a directionalizing fiber optic plate  200  including a plurality of optical fibers  205 . The optical fibers  205  may be constructed from silica, plastics, and the like. The optical fibers  205  may be aligned in a parallel manner so as to form an input surface  206  and an output surface  207 . The optical fibers  205  may be configured such that the output surface  207  of the fiber optic plate  200  forms an at least partially concave shape. The perimeter of the shape of the concave portion of the output surface  207  may be circular (as in  FIGS. 3-6 ) or square (as in  FIGS. 7-9 ). However, it will be recognized that the perimeter of the shape of the concave portion of the output surface  207  may be sized so as to correspond to the shape of any image display device. 
     Referring to  FIG. 10 , the concave shape of the output surface  207  may be created by shaping the optical fibers  205  at a particular bias angle so as to bias the optical axis of the output light. As shown in  FIG. 6 , an optical fiber  205 - 1  cut at a bias angle (β) may result in an optical axis bias angle (δ) for the output light. The relation between the bias angle (β) of optical fiber  205 - 1  and the optical axis bias angle (δ) is as follows: 
                   δ   =       sin     -   1       ⁡     (         n   1     ⁢   βπ       180   ·     n   0         )               Equation   ⁢           ⁢     (   1   )                 
where n 1  is the refractive index of the optical fiber  205 - 1  (typically ˜1.52) and n 0  is the refractive index of air (typically ˜1.0). For example, an optical fiber  205 - 1  cut at a bias angle (β) of 20° will have an optical axis bias angle (δ) of 32°. As such, the optical axes  208  light emitted by the optical fiber  205 - 1  will be directed inward towards a user and away from external reflective surfaces.
 
     The bias angle shaping may be accomplished via various machining mechanisms include cutting, grinding, laser etching, and the like. 
     The particular curvature of the output surface  207  may be defined according to a particular application of an image display device  201 . Specifically, the output surface  207  may be designed to minimize reflections resulting from portions of an aircraft canopy within a field of view of a user. 
     For example, in such avionics applications the image display device  201  may be a given distance from a pilot&#39;s head as defined by the seating configuration of the aircraft (e.g. 24 inches). The viewing angle from each portion of the image display device  201  to the pilot&#39;s head may be computed based various factors including the distance from the image display device  201  to the pilot&#39;s seat, the pilot&#39;s approximate height, and the like. 
     The bias angles of the optical fibers  205  forming the output surface  207  may be shaped to direct light from the various portions of the image display device  201  toward the pilot according to the computed viewing angles when the fiber optic plate  200  is disposed substantially adjacent (e.g. in front of or behind) the transmissive display panel  203 . 
     Referring to  FIG. 11 , representative optical axes  208  of various portions of the output surface  207  are shown. The width of the cone of light produced an optical fiber  205 - 1  is a function if the numerical aperture of that optical fiber  205 - 1 . It should be noted that the light emitted from the various optical fibers  205  becomes asymmetrical about their optical axes  208  when moving towards the perimeter of the output surface  207 . Due to the asymmetrical nature of the light distribution, it is possible to design the fiber optic plate such that no light is transmitted outside the pilots head box and any extraneous light is eliminated from reaching the canopy further controlling canopy reflections. 
     As presented above, the concave shape of the output surface  207  may be employed to direct light output from an image display device  201  towards a viewer. However, it will be recognized that the angle of the bias cuts are greater towards the perimeter of the fiber optic plate  200  than in the middle of the fiber optic plate  200 . As such, the portions of the middle of the fiber optic plate  200  may be substantially planar. 
     Referring to  FIG. 12 , it may be the case that large optical fiber diameters (i.e. fibers with large numerical apertures) may result in extraneous light being transmitted outside a desired field of view when incorporated into the substantially planar portion of the output surface  207  of the fiber optic plate  200 . For example, an optical fiber  205 - 1  having a large numerical aperture may have a resultant cone angle whereby light  209  projected against a reflective surface  210  (e.g. a cockpit canopy) having a given surface angle will be reflected into the field of view of a user  100  (e.g. a pilot). 
     In order to avoid such reflections due to the substantially planar portion of the fiber optic plate  200  the angle of the reflective surface  210 , the line of sight vector of the user  100  associated with that reflective surface  210  and the relative positions of the image display device  201 , the reflective surface  210  and the user  100  may be measured to determine a threshold angle  211  where light transmitted by the optical fiber  205 - 1  will be reflected into the field of view of the user  100 . 
     Referring to  FIG. 13 , the dimensions of the optical fibers  205  within the substantially planar portion of the output surface  207  of the fiber optic plate  200  may be specified so that their emitted light is projected at an angle  212  less than the threshold angle  211 . 
     While the specification of the dimensions of the optical fibers  205  described above is with respect to those optical fibers  205  located within the substantially planar portion of the output surface  207  of the fiber optic plate  200 , similar methodologies may be employed with respect to the more arcuate portions of the output surface  207  of the fiber optic plate  200  to enable further customization of the fiber optic plate  200 . For example, the optical fibers  205  located within the substantially planar portion of the output surface  207  may have a first numerical aperture value while the optical fibers  205  forming the more arcuate portions of the output surface  207  of the fiber optic plate  200  may have a second numerical aperture value. 
     Referring to  FIG. 14A , the fiber optic plate  200  may be incorporated within an image display device  201  between the light source  202  and the transmissive display panel  203 . In addition to the fiber optic plate  200 , the image display device  201  may include a light source  202 , a transmissive display panel  203 , and a diffuser  204 . The light source  202  may include a light-emitting diode (LED), organic LED, cold cathode fluorescent lamp (CCFL), and the like. The transmissive display panel  203  may include a transmissive electro-optical device such as a liquid crystal display, an electrophoretic display, a suspended particle display, electrochromic display, and the like. The light source  202  may emit light which may be directed through the transmissive display panel  203  towards a given focal point (e.g. a pilot) by the fiber optic plate  200 . 
     Referring to  FIG. 14B , the fiber optic plate  200  may be affixed to the front surface of an image display device  201  by a temporary or permanent coupling mechanism  214 . For example, the coupling mechanism  214  may include a pressure sensitive adhesive layer  214  disposed between the fiber optic plate  200  and a front surface of the image display device  201 . Alternately, the coupling mechanism  214  may include clips, bolts and the like (not shown) which may engage cooperating structures (e.g. clip tabs, threaded apertures and the like) on the fiber optic plate  200  and/or the image display device  201  so as to affix the fiber optic plate  200  to the image display device  201 . Such a configuration may allow for aftermarket application of the fiber optic plate  200  to existing transmissive display devices or the use of the fiber optic plate  200  with a light-emitting display panel  213  (e.g. a plasma display, an LED display, an OLED, a CRT display and the like). The light-emitting display panel  213  may emit light which may be directed through the fiber optic plate  200  towards a given focal point (e.g. a pilot). 
     Further, as shown in  FIGS. 14A and 14B , the fiber optic plate  200  may be sized such that the arcuate portion  207 - 1  of its output surface  207  aligns with the perimeter of the light source  202  or the light-emitting display panel  213  while the substantially planar portions of the periphery of its output surface  207 - 2  are outside the perimeter of the light source  202  or the light-emitting display panel  213 . Such a configuration may limit the transmission of light by the optical fibers  205  composing any substantially planar portions of the periphery of the output surface  207  from transmitting the in order to avoid the transmission of light outside the field of view defined only by the arcuate portion  207 - 1 . 
     It is believed that the present disclosure and many of its attendant advantages will be understood by the foregoing description, and it will be apparent that various changes may be made in the form, construction and arrangement of the components without departing from the disclosed subject matter or without sacrificing all of its material advantages. The form described is merely explanatory, and it is the intention of the following claims to encompass and include such changes.