Abstract:
A display device including an illumination source disposed behind an at least partially translucent display area, with a diffuser baffle disposed therebetween. The diffuser baffle includes at least one diffuser lens with a gap on at least one side thereof. Light emitted by one or more light devices on the illumination source is dispersed and scattered by the diffuser lens and gap in the diffuser baffle before being projected on the back of the at least partially translucent display area. The dispersed and scattered light from behind more evenly illuminates the at least partially translucent display area.

Description:
PRIOR APPLICATION 
   Pursuant to 37 C.F.R. § 1.78(a)(4) and 35 U.S.C. § 119(e), this application claims the benefit of U.S. Provisional Application Ser. No. 60/430,399, filed Dec. 3, 2002. 

   TECHNICAL FIELD 
   This invention relates generally to display devices and, more particularly, to a display device with a rear-illuminated display area. 
   BACKGROUND ART 
   Various types of display devices are known in the art for advertisements, signs, attractions, and the like. Display devices typically have a display area which displays graphics, pictures, characters, words, etc. of interest. Many display devices have an associated illumination means for illuminating the display area for enhancing its visibility in low lighting conditions or to make it more appealing and attention-catching to observers. Some illuminated display devices have certain portions of the display area illuminated more or differently to highlight or direct more attention to those particular portions. 
   The various types of illumination means known in the art for illuminating display areas of display devices vary in how they illuminate the display area. Some simply comprise a light source, such as a light bulb or a fluorescent light, directing light at the surface of the display area. Others have an at least partially translucent display area with a light source disposed behind it, whereby light from the light source passes through the at least partially translucent display area and illuminates it. Such rear-illuminated display devices, however, have drawbacks. The light source usually projects a strong bright spot, sometimes termed as a hot spot, at the location of the light source behind the display area. Further, there is a gradient of decreasing light in a direction away from the light source on the remainder of the display area. Such inconsistent illumination, particularly the hot spots at the location of the light source, project an unappealing visual impression on an observer and are therefore undesirable. 
   Solutions that have been proposed for this problem have shortcomings. For example, fiberoptic weaves or meshes disposed under the display area provide inconsistent illumination, and are usually unable to provide an adequate amount of illumination because of the limited amount of light they can carry and deliver. Light bulbs and fluorescent lights usually cause hot spots, and can require large amounts of electric power, usually in the form of alternating current. Therefore, they are not always practicable for use in smaller-sized or battery-powered and portable display devices. Electroluminescent lamps provide illumination proportionate to the amount of electric power provided, so although they may work in battery powered and portable devices, the illumination they provide is limited to the amount of electric power available, which may sometimes not be adequate in a battery operated or portable display device. 
   Accordingly, there is a need for a display device with a rear-illumination means for its display area that overcomes such problems. The present invention is directed to overcoming one or more of these problems. 
   SUMMARY OF THE INVENTION 
   In one aspect of the present invention, a display device comprises a display area that is at least partially translucent. An illumination source is disposed behind the display area, and a diffuser baffle is disposed between the illumination source and the display area. The diffuser baffle includes at least one diffuser lens and at least one spacer disposed adjacent to the diffuser lens. The spacer forms a gap between the diffuser lens and one of the display area and the illumination source. 
   These and other objects and advantages of the present invention will be classified in the following description of the preferred embodiment in connection with the drawings, the disclosure and the appended claims, wherein like reference numerals represent like elements throughout. The drawings constitute a part of this application and include exemplary embodiments of the present invention and illustrate various features thereof. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is front view of a display device according to one embodiment of the present invention; 
       FIG. 2  is a schematic illustration of an illumination source for the display device of  FIG. 1 ; 
       FIG. 3  is an exploded view of one embodiment of a diffuser baffle and its components implemented in the display device of claim  1 ; and 
       FIG. 4  is a schematic illustration of an alternate embodiment of an illumination source for the display device of  FIG. 1 . 
   

   Corresponding reference characters indicate corresponding parts throughout the several figures for more convenient understanding and practice of the present invention. 
   DETAILED DESCRIPTION 
   While the present invention may be embodied in many different forms, there is shown in the drawings and discussed herein a few specific embodiments with the understanding that the present disclosure is to be considered only as an exemplification of the principles of the invention and is not intended to limit the invention to the embodiments illustrated. 
   Referring to  FIG. 1 , a front view of a display device  10  according to one embodiment of the present invention is shown. Display device  10  includes a display area  12 , such as a panel, which may have something of interest displayed thereon. Although display area  12  depicted in the drawings is flat and rectangular, it is recognized and anticipated that the present invention is applicable to display devices with display areas of any shape or size. Display area  12  is preferably at least partially translucent whereby at least some light may pass therethrough. Various materials are known in the art, such as partially transparent plastic or painted glass, that are at least partially translucent and are used for forming display areas in display devices. 
   Display device  10  is electrically coupled to an electric power source  14  by one or more electrical conductors  16 . Electric power source  14  may be an external source of AC or DC electric power, or it may be an internal source of electric power such as a battery held inside or adjacent to display device  10 . Electrical conductors  16  may be any component capable of conducting electric current, such as wires, leads, conductive traces on a circuit board, and the like. 
   Referring to  FIG. 2 , a schematic illustration of an illumination source  18  for display device  10  is shown. Illumination source  18  includes a board or panel  19  that can hold electrical or electronic components. In one embodiment, board or panel  19  is a 5 mil. thick flexible printed circuit board with electrical and electronic components embossed therein and interconnected in a predetermined manner with conductive epoxy. In such embodiment, the embossed electrical and electronic components may be potted with non-conductive UV or thermally cured resin epoxy, which is known in the art. Illumination source  18  is disposed behind display area  12  and is operable to emit light at display area  12  from behind as shown in  FIG. 3  and discussed in more detail below. 
   Illumination source  18  includes one or more light devices  20  that are operable to emit light. In one embodiment, light devices  20  are surface-mount device (SMD) light emitting diodes (LED). In other embodiments, light devices  20  may be light bulbs, fiberoptic channels, fluorescent tubes, electroluminescent lamps, or any other means or device capable of emitting light. The number of light devices  20  in illumination source  18  will typically vary from one embodiment to another, and will usually depend on the light requirements for display area  12  in the particular embodiment of display device  10 , the light output of the particular light devices  20  implemented in that embodiment, and the electrical power available from electric power source  14  in that embodiment. In this regard, it is recognized and anticipated that the types and number of light devices  20  implemented in a particular embodiment of the present invention may be customized in accordance with the particular requirements of an embodiment. In the embodiment shown in  FIG. 2 , illumination source  18  includes sixteen light devices  20 , each of which are commercially available SMD LEDs rated 20 mA at 3.5V. 
   Light devices  20  may be positioned on illumination source  18  in any configuration desired for a particular embodiment of the present invention. The layout may depend on the light output of each respective light device  20  and the amount of illumination desired for the various portions of the corresponding display area  12 . In the embodiment shown in  FIG. 2 , the sixteen light devices  20  are distributed on illumination source  18  as shown to achieve a more even distribution of illumination on display area  12 . 
   Light devices  20  are electrically coupled to electric power source  14  via electrical conductors  16 . In one embodiment, each light device  20  is connected in parallel to electric source  14  via electrical conductors  16  so that operation of a light device  20  is not impacted by the operation of other light devices  20  on that same circuit. However, it is recognized and anticipated that in alternate embodiments light devices  20  may be connected in series, or in a combination of parallel and series, without departing from the spirit and scope of the present invention. 
   Disposed between display area  12  and illumination source  18  is a diffuser baffle  22 . Referring to  FIG. 3 , an exploded view of one embodiment of diffuser baffle  22  is shown implemented between display area  12  and illumination source  18 . A diffuser baffle  22  according to the present invention includes at least one diffuser lens  24  with a spacer  26  on at least one side. Diffuser lenses  24  are essentially a sheet or panel of a translucent material that is preferably substantially translucent but not completely transparent, such as semi-clear plastic, vellum, polyester, paper, elastomer, or the like. The thickness of each diffuser lens  24  may vary, and is 5 mils in one embodiment. Spacers  26  serve the purpose of separating the items disposed on each side thereof and to form a gap  28  between those items. In this regard, spacers  26  may be made of any material such as polycarbonate, polyester, plastic, wood, and the like. In one embodiment, spacers  26  include a pressure-sensitive adhesive for implementation in diffuser baffle  22  by adhering the pressure-sensitive adhesive with an adjoining item. The thickness of spacers  26  may be adjusted in each embodiment to correspond to the thickness of gap  28  desired between the items on each side of the respective spacer  26  in that particular embodiment. In one embodiment, the thickness of spacers  26  is 9 mils. each. 
   In the embodiment shown in  FIG. 3 , diffuser baffle  22  includes three diffuser lenses  24  separated by spacers  26  with gaps  28  formed by spacers  28 . In one embodiment, gaps  28  consist of ambient air disposed between the items on each side of the respective spacer  26 . In alternate embodiments, gaps  28  may consist of an inert gas, such as Nitrogen, held in the gap by an airtight laminating material that laminates the spacer and at least one of its adjoining items. Many types of airtight transparent laminating materials are known in the art. 
   In this configuration, display area  12  on display device  10  is illuminated from behind when electric power source  14  provides electric power to light devices  20 . Light emitted by light devices  20  passes through each of the gaps  28  and diffuser lenses  24  between illumination source  18  and display area  12 . During such travel, the light is dispersed by each diffuser lens  24 . The dispersed light from a diffuser lens  24  is scattered over a wider area because of the gap  28  following that diffuser lens  24 . This dispersed and scattered light is further dispersed and scattered by each successive diffuser lens  24  and gap  28 . As a result, when the light reaches display area  12 , it is considerably dispersed and scattered from its origin which was at one or more specific source points. This dispersed and scattered light travels through the at least partially translucent display area  12  and gives the aesthetic impression of an illuminated display area  12  with comparatively more even illumination and considerably reduced or no hot spots. 
   In this regard, those skilled in the art will appreciate that increasing the number of diffuser lenses  24  and gaps  28  in an embodiment of the present invention will directly correlate to more even scattering and dispersion of light emitted by light devices  20  on display area  12  and, therefore, minimizing the appearance of hot spots. 
   In the embodiment shown in  FIG. 3 , display device  10  also includes a holding means  30  and  32  for holding illumination source  18  more securely in display device  10 . Holding means  30  and  32  may be constructed of any material known in the art, and it is recognized that they are optional and not critical for practicing the present invention. 
   In alternate embodiments of the present invention, diffuser lenses  24  and the placement of light devices  20  may be altered to control the illumination of display area  12 . For example, if a certain portion of display area  12  needs to be highlighted more than other areas, such as to highlight a logo or trademark, a light device  20  may be placed directly behind such area and the portions of the diffuser lenses  24  directly between that light device  20  and the portion to be highlighted may be made thinner, or more transparent, or removed altogether, to increase the amount of light delivered to that portion of the display area  12 . Referring to  FIG. 4 , a schematic illustration of an alternate embodiment of an illumination source  118  for a display device  10  is shown wherein four light devices  120  are strategically placed in a certain concentrated circular pattern to deliver comparatively more light to the middle portion of the left half of the corresponding display area  12 . In alternate embodiments, the strength and types of light devices  20  and their respective placement or pattern on illumination source  18  behind display area  12  may be customized to suit the particular requirements of the respective embodiment. Such patterns may include, for example, light devices  18  implemented in a square pattern, a triangular pattern, an uneven zigzag pattern, or the like. Accordingly, all such modifications and alterations are recognized and anticipated, and it is intended that the claims shall cover all such embodiments that do not depart from the spirit and scope of the present invention. 
   It is further recognized and anticipated that electronic controls and other features may be implemented in the electric circuitry associated with illumination source  18  of display device  10 . For example, a switch (not shown in the drawings) may be added to the electric circuit formed by electric power source  14 , electrical conductors  16 , and light devices  20  to selectively switch light devices  20 , and consequently the illumination on display area  12 , on and off. The switch may be any type of electric switch, and is a membrane switch in one embodiment. Membrane switches are known in the art. 
   In one embodiment, electronic control means may be added to the circuit formed by electric power source  14 , electrical conductors  16 , and light devices  20  to control the operation of light devices  20  in a predetermined manner. For example, various light devices  20  may be programmed to turn on and off or blink in a predetermined manner or pattern to enhance the aesthetic appeal of the contents displayed on display area  12  or to make them more attention-catching for observers. Or, light devices  20  of different colors may be implemented in certain patterns and their operation may be controlled to enhance the message or appeal of the contents of display area  12 . Various electronic control means to perform such operations with light devices, particularly with LEDs, are well known in the art and many are commonly available commercially. 
   As is evident from the foregoing description, certain aspects of the present invention are not limited by the particular details of the embodiments illustrated herein, and it is therefore contemplated that other modifications and applications, or equivalents thereof, will occur to those skilled in the art. It is accordingly intended that the claims shall cover all such modifications and applications that do not depart from the spirit and scope of the present invention. 
   Other aspects, objects and advantages of the present invention can be obtained from studying the drawings, the disclosure, and the appended claims.