Abstract:
A device that enlarges text and images to enable a low vision person to see the text and images includes a hollow structure including a top housing and a bottom housing that are connected to one another. A camera aperture is formed in the bottom housing and a transparent light guide lens is disposed in closing relation to the camera aperture so that all light entering the camera aperture must first pass through the light guide lens. A cavity formed in the light guide lens is bounded by walls that are positioned at a critical angle. Light-emitting diodes are positioned at critical locations about the periphery of the light guide lens to illuminate the object being viewed.

Description:
CROSS-REFERENCE TO RELATED DISCLOSURES 
     This application is a continuation of and claims priority to co-pending Utility Patent Application, Serial No. 11/689,019, filed Mar. 21, 2007, entitled “PDT Camera Magnifier Illumination,” which in turn claims priority to U.S. Provisional Application Serial Number 60/767,353 filed on Mar. 21, 2006. The disclosures of both these applications are fully incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates, generally, to devices that enable people having low vision to read printed documents. More particularly, it relates to a camera in an electronic magnifier requiring symmetrical illumination when used in contact with or near a target object such as a printed document. 
     2. Description of the Prior Art 
     Using a magnifying glass to enlarge print is problematic. The glass must be positioned a specific distance from the paper to obtain optimal magnification, and the paper must be well-illuminated. 
     The art has therefore moved in the direction of using video cameras to view the print and to drive a liquid crystal display (LCD) that displays the camera output in enlarged form. Such systems typically include a magnifier system where magnification is determined by the distance to the object to be viewed, the ratio of sensor to display size, and optical features of the camera. In the future, the optical features of the camera may perform the magnification. 
     Uniform, symmetrical illumination of the object being viewed has remained problematic. Thus, there remains a need for a low vision reader having an LCD display of a well-illuminated object. 
     Conventional low vision readers require a user to either hold the reader above the document or to use clumsy stands to hold the reader above the document. 
     Thus there is a need for a low vision reader that does not require a user to hold the reader in hovering relation to a document, either with or without a stand. 
     However, in view of the prior art taken as a whole at the time the present invention was made, it was not obvious to those of ordinary skill how the identified needs could be fulfilled. 
     SUMMARY OF THE INVENTION 
     The long-standing but heretofore unfulfilled need for a low vision reader including an LCD display of a well-illuminated object is now met by a new, useful, and non-obvious invention. The invention also fulfills the need for a device that need not be held over a document in hovering relation thereto when in use. 
     The novel device enlarges text and images to help a low vision person see such text and images. A hollow structure includes a top housing and a bottom housing that are connected to one another. A camera aperture is formed in the bottom housing and a transparent optical light guide lens is disposed in closing relation to the camera aperture so that all light entering the camera aperture must first pass through the optical light guide lens. 
     Significantly, the device rests atop the document or other object being viewed. Accordingly, no stands or other means for hovering the reader over the document are required. The reader is easily slideable from one part of the document to the next, and the part of the document being viewed is always well-illuminated with symmetrical lighting so that there are no dark spots or other abnormalities in the LCD output display. 
     A first undercut is formed in the bottom housing adjacent a first edge of the camera aperture and a second undercut is formed in the bottom housing adjacent a second end of the camera aperture. The optical light guide lens has a first mounting flange at a first end thereof, a second mounting flange at a second end thereof, and a raised section between the first and second mounting flanges. The first undercut is defined by a first overhang and is adapted to receive the first mounting flange. The second undercut is defined by a second overhang and is adapted to receive the second mounting flange. 
     The first mounting flange has a length in excess of a depth of the first undercut so that a first space is created between the raised section of the light guide lens and the first overhang. The second mounting flange also has a length in excess of a depth of the second undercut so that a second space is created between the raised section of the light guide lens and the second overhang. 
     A printed circuit board is disposed in overlying relation to an interior side of the optical light guide lens. A window or opening is formed in the printed circuit board so that light can pass through the light guide lens. A first pair of light-emitting diodes is secured to a first end of the printed circuit board adjacent a first end of the camera aperture and a second pair of light-emitting diodes is secured to a second end of the printed circuit board adjacent a second end of the camera aperture. The first pair of light-emitting diodes is disposed in the first space on opposite sides of a longitudinal axis of symmetry of the camera aperture and the second pair of light-emitting diodes is disposed in the second space on opposite sides of the longitudinal axis of symmetry of the camera aperture. 
     An important advantage of the invention is that the object being viewed is illuminated in an optimal way by the light emitting diodes (LEDs) that are strategically positioned about the perimeter of the optical light guide lens. The optical light guide lens has a specific structure that bends light rays emitted by the LEDs into the object being scanned without any reflections of the LEDs on the camera. 
     Another major advantage is that the novel structure minimizes light leakage about the periphery of the optical light guide lens. 
     These and other advantages will become apparent as this disclosure proceeds. The invention includes the features of construction, arrangement of parts, and combination of elements set forth herein, and the scope of the invention is set forth in the claims appended hereto. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a fuller understanding of the nature and objects of the invention, reference should be made to the following detailed description, taken in connection with the accompanying drawings, in which: 
         FIG. 1  is an exploded perspective view of a bottom housing; 
         FIG. 2  is a perspective view of the interior side of the novel light guide lens; 
         FIG. 3  is a perspective view of the exterior side of the novel light guide lens; 
         FIG. 4  is a cross-sectional view taken along line  4 - 4  in  FIG. 1  and along line  4 - 4  in  FIG. 2 ; 
         FIG. 5  is a cross-sectional view depicting the light guide lens and the bottom housing when connected to one another, including an LED, the PCB, and the stiffener; and 
         FIG. 6A  is a simple ray trace diagram indicating how light rays are affected by the mirror of the incorporated disclosure; 
         FIG. 6B  is a raytrace diagram indicating the effectiveness of the angle α; and 
         FIG. 6C  is a raytrace diagram indicating how the novel positioning of LEDs relative to the novel structure of the optical light guide lens accomplishes the even illumination of the object being viewed. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     U.S. patent application Ser. No. 11/308,298, entitled “Magnifier Having Slideably Mounted Camera,” filed by the same inventors on Mar. 15, 2006, which application claims priority to U.S. provisional patent application No. 60/595,003, entitled: “Portable Electronic Magnifier,” filed by the same inventors on May 26, 2005, is hereby incorporated by reference into this disclosure. 
       FIG. 1  of the present disclosure depicts bottom housing  12  that is engaged at its periphery by sidewalls  14   a ,  14   b ,  14   c , and  14   d  of top housing  10  depicted in  FIGS. 2 ,  3  and  4  of the incorporated disclosure. Generally rectangular opening  12   a  is formed in said bottom housing  12  at a first end thereof so that when bottom housing  12  is attached to top housing  10  of the incorporated structure, opening  12   a  is in registration with mirror  26  of the structure depicted in the incorporated disclosure. Thus, rectangular opening  12   a  is understood to be a camera aperture. The user of the device slides opening  12   a  over the text or other image to be enlarged and the enlarged text or image appears on LCD screen  14 , depicted in  FIG. 2  of the incorporated disclosure. 
     Light guide lens  14  of this disclosure is positioned in registration with camera aperture  12   a  when the novel device is fully assembled. Light guide lens  14  is made of a clear plastic, preferably Plexiglas® acrylic resin. 
     Upstanding pegs  16 ,  17 , and  18  are formed integrally with light guide lens  14  and are adapted to engage openings denoted  16   a ,  17   a , and  18   a , respectively, fowled in bottom housing  12  about the periphery of aperture  12   a . More particularly, prior to attaching bottom housing  12  to top housing  10  of the incorporated disclosure, printed circuit board (PCB)  15 , as depicted in  FIG. 1 , is placed in closing relation to camera aperture  12   a  on the interior side thereof. Opaque stiffener  19  is then placed in overlying relation to said PCB, and novel light guide lens  14  is positioned in underlying relation to said PCB by inserting pegs  16 ,  17 , and  18  into peg bores  16   a ,  17   a , and  18   a , respectively. The interior side of light guide lens  14  is depicted in  FIG. 1  and said PCB overlies said interior side. 
     Opening or window  15   a  is formed in the center of PCB  15  and opening or window  19   a  is formed in the center of stiffener  19  so that light rays can enter light guide lens  14 . Exterior surface  15   b  of PCB  15  is preferably black in color to provide a mask around camera aperture  12   a  and to reduce stray light effects that may propagate towards the camera. 
     Light guide lens  14  includes a flange  20  at its opposite ends. Center part  22  of light guide lens  14  is raised with respect to said flanges, thereby creating cavity  24  ( FIG. 3-5 ). Angle α is one hundred thirty five degrees (135°). 
     As best depicted in  FIG. 2 , peg  16  is positioned within arcuate recess  26  formed in a transverse edge  28   a  of raised part  22 . Edge  28   a  is bounded by longitudinally-extending edges  28   b ,  28   b . Second transverse edge  30   a , on the opposite side of raised section  22 , is bounded by longitudinal edges  30   b ,  30   b .  FIG. 2  also indicates the positions of four (4) light emitting diodes (LEDs), collectively denoted  34 . 
     Significantly, a first pair of said LEDs are positioned at a first end of light guide lens  14  on opposite sides of longitudinal axis of symmetry  14   a  of said light guide lens in symmetrical relation to one another, and a second pair of said LEDs are positioned at a second end of light guide lens  14  on opposite sides of said longitudinal axis of symmetry in symmetrical relation to one another. 
     Although PCB  15  is not depicted in  FIG. 2 , it should be understood that LEDs  34  are secured to said PCB. The height difference between mounting flanges  20 ,  20  and raised section  22  is sufficient to accommodate said LEDs. 
       FIG. 3  depicts the exterior side of light guide lens  14 . Each wall  24   a  is angled relative to the plane of raised section  22  at an angle α that is equal to one hundred thirty five degrees (135°) as aforesaid. 
       FIG. 4  provides a cross-sectional view of optical light guide lens  14 . All of the parts indicated by reference numerals in said  FIG. 4  have been identified above. 
       FIG. 5  depicts bottom housing  12  having undercut  32  formed therein, defined by overhang  33 . Each flange  20  of light guide lens  14  has an extent that exceeds the depth of its associated undercut  32  so that space  36  is created between raised center part  22  and overhang  33 . There is a space  36  on each end of aperture  12   a  and each of said spaces accommodates two (2) LEDs. 
     Light rays entering the center of light guide lens  14  travel straight through raised section  22  but the light rays that encounter angled walls  24   a  are reflected therefrom in a way perhaps best explained by  FIGS. 6A ,  6 B, and  6 C. 
     More particularly,  FIG. 6A  depicts a simple raytrace modeling the scattered light from the land in front of the LEDs. This shows the path of the light up onto the mirror, where it is projected downwardly into the field of view. 
     By increasing the bevel angle to forty five degrees (45°), as depicted in  FIG. 6B , the scattered light from this area is kept inside the window to contribute to the general illumination. 
       FIG. 6C  depicts a simple model of the LED position. It shows that only a small pencil of light will strike the mirror at a low angle, outside of the field of view of the camera and any reflected light will be directed onto the back of PCB  15 . 
     The relative positioning of each LED  34  relative to cavity  24 , bounded by sidewalls  24   a  that are disposed at said angle α, is an important part of this invention. Each LED  34  is positioned in a space created by the step between raised section  22  and mounting flange  20  of optical light guide lens  14 , said space being further created by the structuring of each mounting flange to exceed the depth of its associated undercut  32  as explained above. As best understood in connection with  FIG. 5 , this positions each LED  34  at a substantially forty five degree (45°) angle relative to its associated sidewall  24   a . Each LED is thus positioned outside of cavity  24  and the light from each LED must pass through optical light guide lens  14  to illuminate the object being sensed by the camera of the incorporated disclosure. This novel structure eliminates the poor illumination characteristics of prior art devices. 
     The slideability of the novel structure over the document or other object being viewed is another important feature of the invention. The contact between the device and the object eliminates the need for stands or manual holding of the device in hovering relation to the object. The flat, low friction bottom of the device is understood from all of the figures but is perhaps best understood in connection with  FIGS. 4 and 5 . 
     It will thus be seen that the objects set forth above, and those made apparent from the foregoing description, are efficiently attained and since certain changes may be made in the above construction without departing from the scope of the invention, it is intended that all matters contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. 
     It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall there between. 
     Now that the invention has been described,