Abstract:
A LED symbol signal with LEDs arrayed to correspond to a desired symbol. Light from the LEDs is directed onto corresponding optical segments of a multiple collimating zone element and directed into a forward direction/distribution. A mask defines the desired symbol. The optical segments and or a diffusion surface on the cover or multiple collimating zone element(s) diffuses the display aspect, obscuring the individual LEDs. A diameter of the optical features of the diffusion surface is smaller than a diameter of the optical segments. The LED symbol signal may be configured for retrofitting into an incandescent lamp signal housing.

Description:
[0001]    This application claims the benefit of U.S. provisional application No. 60/283,882, filed Apr. 13, 2001 and U.S. provisional application No. 60/361,140, filed May 1, 2002, both applications hereby incorporated by reference in their entirety. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to light emitting diode (LED) signals, specifically to an LED symbol signal with a uniform display aspect despite having a reduced number of LEDs.  
           [0004]    2. Description of Related Art  
           [0005]    Symbol signals, for example turn signals, pedestrian signals, and walk/don&#39;t walk signals previously have been designed with incandescent point light sources in a housing with a mask covering. The mask defining the symbol desired. Incandescent bulbs suffer from drawbacks of high power consumption and the requirement for frequent maintenance as the bulbs burn out.  
           [0006]    LED symbol signals have reduced maintenance and operating costs due to the extreme life span of LEDs and their low power consumption in comparison to incandescent bulbs. Previously, LEDs were used to form the symbol desired by filing the symbol space with a full matrix of LEDs. As new, improved generations of LEDs become available, they emit more light from each individual LED. Therefore, the full matrix of LEDs is not required to create a suitably bright signal. The LEDs may then be spaced further apart from each other, omitting LEDs thereby saving material costs and lowering the signals operating power consumption. However, as the LEDs spacing increases, an undesirable “pixel effect” appears in which the individual LEDs become increasingly discernable to the viewer.  
           [0007]    An object of the present invention is to provide a high efficiency and cost effective LED symbol with a reduced or eliminated “pixel effect”. A further object of this invention is to provide a LED symbol signal with a design that may be easily modified as new generations of LEDs with increased light output become available, reducing the number of LEDs required to achieve a similar light output level.  
         SUMMARY OF THE INVENTION  
         [0008]    A LED symbol signal with LEDs arrayed to correspond to a desired symbol. Light from the LEDs is directed onto corresponding optical segments of a multiple collimating zone element and directed into a forward direction/distribution. A mask defines the desired symbol. The optical segments and or a diffusion surface on the cover or multiple collimating zone element(s) diffuses the display aspect, obscuring the individual LEDs. A diameter of the optical features of the diffusion surface is smaller than a diameter of the optical segments. The LED symbol signal may be configured for retrofitting into an incandescent lamp signal housing. 
       
    
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0009]    [0009]FIG. 1A is an isometric exploded view of a thick mask embodiment of the invention.  
         [0010]    [0010]FIG. 1B is an isometric exploded view of a thin mask embodiment of the invention.  
         [0011]    [0011]FIG. 2A is an isometric cut-away side view of a thin mask embodiment of the invention, showing light paths through the optical elements (electrical components omitted for clarity).  
         [0012]    [0012]FIG. 2B is an isometric cut-away side view of a thick mask embodiment of the invention.  
         [0013]    [0013]FIG. 3A is a side view of the embodiment shown in FIG. 2A, with increased component details.  
         [0014]    [0014]FIG. 3B is a side view of the embodiment shown in FIG. 2B, with increased component details.  
         [0015]    [0015]FIG. 4A is a schematic view of optical segments showing LED light distribution falling within the associated optical segments.  
         [0016]    [0016]FIG. 4B is a schematic view of optical segments showing LED light distribution falling outside the associated optical segments.  
         [0017]    [0017]FIG. 5A is a schematic view of hexagonal optical segments.  
         [0018]    [0018]FIG. 5B is a schematic view of a human figure composed of hexagonal optical segments.  
         [0019]    [0019]FIG. 6A is a schematic view of a PCB board for an arrow symbol signal.  
         [0020]    [0020]FIG. 6B is a schematic view of a bulk PCB showing the layout thereon of multiple PCB&#39;s according to FIG. 6A thereon.  
         [0021]    [0021]FIG. 7 is a perspective view of the invention inserted in an incandescent signal with the incandescent bulb and lens removed.  
         [0022]    [0022]FIG. 8 is a partial side view of one embodiment of the invention showing the dimensional relationships of the invention elements.  
         [0023]    [0023]FIG. 9 is an isometric cut-away view of a thick mask embodiment of the invention using a reflector. 
     
    
     KEY TO FIGURE ELEMENTS  
       [0024]    [0024] 1 —Cover  
         [0025]    [0025] 2 —Mask  
         [0026]    [0026] 3 —MCZE  
         [0027]    [0027] 4 —Housing  
         [0028]    [0028] 5 —PCB  
         [0029]    [0029] 6 —Nut  
         [0030]    [0030] 7 —Lock washer  
         [0031]    [0031] 8 —LED(s)  
         [0032]    [0032] 9 —Electrical components  
         [0033]    [0033] 10 —Power connection  
         [0034]    [0034] 11 —Post  
         [0035]    [0035] 12 —PCB screw  
         [0036]    [0036] 13 —Power supply wires  
         [0037]    [0037] 14 —Screw  
         [0038]    [0038] 15 —Electrical connection cover  
         [0039]    [0039] 16 —Electrical connection screw  
         [0040]    [0040] 17 —Incandescent socket power connector  
         [0041]    [0041] 18 —Optical segment  
         [0042]    [0042] 19 —Diffusion pattern  
         [0043]    [0043] 20 —LED light emission pattern  
         [0044]    [0044] 21 —O-ring  
         [0045]    [0045] 22 —Bulk PCB panel  
         [0046]    [0046] 23 —Reflector  
       DETAILED DESCRIPTION  
       [0047]    LED signals are disclosed in detail in U.S. patent application Ser. No. 09/756,670, filed Jan. 9, 2001 and further in U.S. patent application Ser. No. 09/827,429, filed Apr. 6, 2001, both applications assigned to Applicant, GELcore LLC, and hereby incorporated by reference in their entirety.  
         [0048]    One embodiment of the present invention is shown in FIG. 1A. A printed circuit board (PCB)  5  includes power supply circuitry and LEDs  8  grouped in clusters of at least one LED  8  each, arranged in the form of a desired symbol, here a directional arrow. The PCB  5  is mounted in a housing  4  with integral power connection  10 . As shown in FIG. 7, the housing  4  may be dimensioned to permit retrofitting of the invention into existing incandescent light signal housings upon removal of the original incandescent light bulb and lens(es). Power connection to existing signal housings may be via an incandescent socket power connector  17 . Use of the socket power connector  17  removes the need for electricians to be involved in signal retrofitting activities. Mounted in/on the housing  4  spaced away from the PCB  5  is an optical element in the form of a multiple collimating zone element (MCZE)  3 . Portions of the MCZE  3 , not desired as part of the symbol are covered by a mask  2 . The housing is closed by a cover  1 .  
         [0049]    MCZE  3  has optical segments  18  (collimating zones) matching the distribution of the LED  8  and/or LED  8  clusters on the PCB  5 . As shown in FIG. 2A, each optical segment  18  collimates the light emitted from its respective LED  8  or LED  8  cluster. Also, each optical segment  18  may spread the light output into a desired distribution pattern. The effect of the MCZE  3  being to collect light from multiple point sources, each LED  8  cluster, and distribute it evenly so that the pixel effect of the individual LEDs  8  is minimized or removed from the display aspect observed by a viewer. As shown in FIG. 4A, it is preferred that rather than overlapping with a neighboring segment as shown in FIG. 4B, that the light pattern  20  from each LED/LED cluster fall within a single optical segment  18 . As shown in FIG. 8, tuning of the LED light emission pattern  20  to fall within an optical segment  18  is achieved by combining the LED  8  light spread angle A°, the optical segment  18  diameter 0 and the distance H between the PCB  5  and the MCZE  3 . For large symbol areas, for example in a walk/don&#39;t walk symbol, the MCZE  3  optical segments  18  may be formed in a hexagonal shape, as shown in FIGS. 5A and 5B. The hexagonal shape minimizing shadows or dark areas as it approximates the circular light emission pattern  20  of the LED(s)  8 . Where the optical segments  18  are on an outside edge, rather than forming the outer edge in the hexagonal form, a circular outside edge maximizes coverage.  
         [0050]    A diffusion pattern  19  on the inner or outer surface of the MCZE  3  or on an inner or outer surface of the cover  1  may be used to further obscure discernability of individual LEDs  8  in the display aspect. The diffusion pattern may be composed of circular, rectilinear or other geometric forms. Also, the diffusion pattern  19  may be formed on the desired surface via abrasion, impact and/or sandblasting. The diffusion pattern  19  preferably has individual diffusion element diameters D in a less than 1 to 1 ratio to the diameter O of the associated optical segments  18 .  
         [0051]    Cover  1  provides an environmental seal for the signal. A flat or a large radius outer surface on cover  1  prevents dirt build-up on the MCZE  3 . Sealing means, for example an o-ring  21 , between the cover  1  and housing  4  seals the signal from the environment.  
         [0052]    Mask  2  may be integrated with the MCZE  3  and/or with the cover  1 . The mask  2  may be in the form of a dark or opaque material, created via insert film molding, tape, paint coating or other means for blocking the LED  8  light not passing through the optical segments  18 .  
         [0053]    To increase the symbol definition and minimize spurious light emissions, the mask  2  may be designed with a depth M that substantially fills the space between the MCZE  3  and the cover  1  (FIGS. 1A, 2B,  3 B).  
         [0054]    MCZE  3  may be a full disk or other shape dimensioned to cover the open end of the housing, with optical segments formed thereon or there may be discrete elements snap-fitting for example, into openings in the mask  2 . For highest economy of materials, the cover  1 , mask  2  and MCZE  3  may be integrated into a single component.  
         [0055]    To combat sun phantom effect, the cover  1  may include an angled outer surface. Also, the diffusion pattern may be limited to only those areas in alignment within apertures in the mask  2  which define the desired symbol.  
         [0056]    To allow directional signals to be used in any orientation, without requiring changes to the internal components, the cover  1  may be optically neutral allowing the assembled housing to be turned in any direction to orient, for example, a signal arrow as desired. A symmetrical optical design focusing the light output along the axis beam of the housing with minimal spreading allows the housing to be turned in any direction without losing the correct display aspect. An asymmetrical optical design may be used to minimize sun phantom effect and or meet Institute of Transport Engineers (ITE) specifications for the display aspect of traffic signals.  
         [0057]    The distance H between the MCZE  3  and the PCB  5  is approximately 1 inches in a standard twelve-inch signal (FIG. 1). For designs where the symbol may be fully illuminated by a shorter distance between the LEDs  8  and MCZE  3 , standoffs or shallower housings may be used. The proper distance allows the LEDs  8  to fully illuminate each optical segment  18  without creating overlap, noticeable shadows or dark areas. The resulting light beam from the signal may be changed by moving the PCB  5  with respect to existing optical components (changing H) thereby changing the light output distribution. This spacing also allows use of light degradation sensor circuitry as described in applicant&#39;s Ser. No. 09/827,429 application incorporated herein.  
         [0058]    As shown in FIG. 9, reflectors  23  may be used to further decrease the number of LEDs  8  required to create a desired LED signal light output level. The reflector  23 , lowers the amount of light emitted outside of the intended light emission pattern  20  by redirecting light normally escaping through the side of an LED  8 . The reflector may also be configured to redirect light which reflects under total internal reflection conditions within the LED housing. A second reflection surface of the reflector may be aligned with the increased exit angle of the total internal reflection light component. Because the angle is higher than that of light escaping sideways from the LED housing, the second reflector surface appears as a step back in the first reflection surface and does not degrade the first surface&#39;s ability to redirect the sideways escaping light component. The extra materials cost of the reflector  23  is recouped be the lowered number of LEDs  8  required and the lower operating costs due to reduced energy consumption. The reflector(s) may be configured around individual LEDs or clusters of LEDs. A channel shaped reflector  23  allows a limited cross-over of the light emitted between nearby LEDs, lessening the change to the display aspect if one or more of the individual LEDs fails.  
         [0059]    The size of the PCB  5  may be determined by the smallest circle, rectangle or other shape that will encompass the desired LED pattern, thus saving material costs by minimizing the size of the PCB  5 . Where arrow symbols are being displayed, the arrow form may be cut from a bulk PCB panel  22  cut out as shown in FIGS. 6A and 6B, minimizing PCB material cost. Power supply and light degradation sensor circuitry may be located on the single PCB  5  in the area B.  
         [0060]    Other embodiments of the present invention include but are not limited to pedestrian signals, pedestrian signals with countdown displays, informational signals including emergency exit signs, and any other form of LED symbol signal which would otherwise suffer from the “pixel effect”. In the case of pedestrian signals or other large graphical symbols the cover may be omitted and or integrated with the mask, the diffusion surface located, for example on an inner surface of the optical elements  18  or on the signal&#39;s external surface.  
         [0061]    This invention is entitled to a range of different embodiments and their equivalents, and is to be limited only by the scope of the following claims.