Abstract:
A backlight for a reel assembly is disclosed comprising a plurality of light emitting diodes (LEDs). An array of red, green, and blue diodes are positioned behind a translucent reel strip to backlight three adjacent symbols on a reel strip. The LEDs are individually controllable to vary the color output of the LED array for a full spectrum of colors including white. Groups of LEDs can be illuminated to optimally illuminate any number of symbols of any size. The LEDs may be controlled to highlight special symbols such as by blinking or changing colors. LEDs are also arranged on both sides of the reel strip in a vertical array so as to outline the edges of the reel strip.

Description:
FIELD OF THE INVENTION 
   This invention relates to reel-type slot machines and, in particular, to an illumination device for backlighting the reel strips in a rotating reel assembly. 
   BACKGROUND 
   Conventional slot machines contain three or more reels, each having a set of symbols around its periphery. The reels are rotated and randomly stopped, and the combination of symbols across one or more paylines determines the award paid to the player. A conventional reel assembly includes a stepper motor that rotates a light plastic circular frame having a replaceable reel strip affixed around the periphery of the frame. Pulses are applied to the stepper motor to cause the stepper motor to rotate through any amount of rotation. The reel strips are translucent and are typically backlit with one or more conventional light bulbs. U.S. Pat. No. 5,839,957, incorporated herein by reference, describes an example of a reel assembly. 
   U.S. Pat. No. 5,388,829, incorporated herein by reference, provides an example of a reel assembly having light bulbs for backlighting the reel strip. If the slot machine is the type where three adjacent symbols on a reel strip are illuminated, three light bulbs may be fixed in a position to optimally illuminate the three symbols. In some cases, each light bulb is surrounded by walls that prevent the light from illuminating symbols other than the one directly in front of the light bulb. If the reel strip were replaced by a different reel strip having larger or smaller symbol positions, the backlight would not be optimum, since the backlights would not be centered behind the symbols on the new reel strip. 
   Additionally, such simple light bulbs used as backlights are constantly on and provide no information to the players. 
   SUMMARY 
   A backlight for a reel assembly is disclosed comprising a plurality of light emitting diodes (LEDs). In one embodiment, an array of red, green, and blue diodes are positioned behind a translucent reel strip to backlight three adjacent symbols on a reel strip. The red, green, and blue LEDs are individually controllable to vary the color output of the LED array for a full spectrum of colors including white. Controlling the LEDs not only enables controlling the color, but groups of LEDs can be illuminated to optimally illuminate any number of symbols of any size. 
   Additionally, the LEDs may be controlled to highlight special symbols such as by blinking or changing colors. 
   In one embodiment, LEDs are also arranged on both sides of the reel strip in a vertical array so as to outline the edges of the reel strip. These vertically arranged LEDs may be used to highlight a particular reel strip, or to show the direction of the reel by sequencing the illumination of the LEDs, or to indicate a left-to-right or right-to-left combination of symbols, or perform other functions. 
   The brightness of the LEDs is also easily controlled to adjust to the ambient light. 
   Other features and advantages of the LED array backlight are disclosed herein. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a front view of one example of a slot machine incorporating reels having the LED backlight of the present invention. 
       FIG. 2  is a perspective view of a reel backlight assembly that may be affixed to the frame of the reel assembly. 
       FIG. 3  is a front view of a printed circuit board with an array of RGB LEDs that forms part of the reel backlight assembly. 
       FIG. 4  illustrates a printed circuit board containing an array of LEDs for outlining the vertical edges of the reel strip, which forms a sidewall of the reel backlight assembly. 
       FIG. 5  is a side view of the reel backlight assembly affixed to the frame of a reel assembly in a slot machine. 
       FIG. 6  is a schematic diagram of certain functional units for controlling the reel backlight assembly using the slot machine&#39;s main CPU. 
   

   DETAILED DESCRIPTION 
     FIG. 1  is a front view of a slot machine that may be comprised of all well known and conventional elements except for the reel backlight assembly described in detail below. Accordingly, there is no need to describe the workings of the slot machine of  FIG. 1  in detail. 
   The slot machine of  FIG. 1  includes a coin slot  1 , a handle  2 , a meter  3  for identifying any necessary information, control buttons  4  for placing bets, spinning the reels, and cashing out, rotatable reels  5 ,  6 , and  7  with reel strips, and a coin tray  11 . 
   In operation, the player generates credits by inserting coins into coin slot  1 . The slot machine may also receive bills, tickets, or any other form of payment. The player makes a bet by pressing the appropriate one of buttons  4  then pulls handle  2  or presses a start button. A CPU in the slot machine initiates the spinning of the three reels  5 - 7  and pseudo-randomly stops the rotation of the reels so that combinations of symbols appear across the paylines A, B, and C. Coins or credits are then awarded to the player based on these combinations. At any time, the player may press the payout button, and a number of coins corresponding to the total accumulated credits are then paid out by a coin hopper into coin tray  11 . 
     FIG. 2  illustrates a reel backlight assembly  20  that is connected to a reel assembly, such as shown in  FIG. 5 . Backlight assembly  20  is positioned proximate to the back of the reel strip so that the reel may freely rotate while being backlit by assembly  20 . 
   Backlight assembly  20  includes symbol backlight portion  30  and side portions  32  and  33 . Portions  30 ,  32 , and  33  are printed circuit boards on which are mounted LEDs  34  and  35 . Only some of the LEDs are shown for simplicity. Conductive traces lead from the LEDs to standard electrical connectors. The printed circuit boards are affixed to a plastic frame  36 . Frame  36  has appropriate flanges  38  or other mechanisms to allow assembly  20  to be affixed to a reel frame assembly or to any other portion of the slot machine for backlighting the reel strips. 
   A flexible diffuser sheet (not shown) may be affixed to the front of frame  36  if a more uniform backlight is desired. The frame  36  may include channels along the upper edges of the sides to receive the edges of a thin diffuser sheet to keep it in place. 
     FIG. 3  is a front view of a printed circuit board  40  forming the backlight portion  30  in  FIG. 2 . Red, green, and blue LEDs  42  are electrically and mechanically connected to board  40  and form an array. In the embodiment of  FIG. 4 , there are 35 LEDs formed in an array of five columns and seven rows. Each LED  42  is actually a combination of a red, green, and blue LED mounted closely together or formed in a single package. Each LED (a semiconductor chip) is typically encased in epoxy, where the epoxy forms a lens that causes most of the light emitted by the LEDs to escape from the lens in a direction normal to the plane of the board  40 . Each LED  42  has a red lead, a blue lead, a green lead, and a ground lead. The current running through each of the red, green, and blue LEDs determines the brightness of each of the three colors. By controlling the currents, any color can be produced by the combination of the red, green, and blue light, including white light. Such red, green, and blue LEDs (either individually or combined in a package) are widely available. In one embodiment, the LEDs  42  are surface mounted packages, avoiding the need to form holes in board  40 . 
   Conventional conductive traces on board  40  are electrically connected to the various leads of the LEDs  42  and terminate in a standard connector  44  for coupling to control circuitry. The electrical and mechanical connection of RGB LEDs to a printed circuit board and to a connector is well known in the field of color displays and need not be described herein in detail. 
   The leads of the various LEDs in the array can be connected in a variety of configurations depending upon the desired lighting flexibility. For example, if it were desired to individually control the RGB color for each LED  42 , then there must be a separate connector terminal for each red, green, and blue LED. Multiplexers or controllers on the board  40  could be used to reduce the number of connector terminals. If it were only desired to separately control each row of LEDs  42 , then the leads of the LEDs in a row may be coupled together to reduce the number of connector terminals. LEDs  42  may be coupled in series and/or parallel. The connector  44  may comprise an array of sockets, pins, pads, wire bonds, or other types of connectors. 
   Since the LEDs  42  in the array are spaced from the reel strip, the light from each LED  42  spreads out and mixes somewhat with light from nearby LEDs so that the player does not see the individual LED quasi-point sources. The reel strip acts to diffuse light. An additional diffuser film may be affixed to the backlight assembly  20 . 
     FIG. 3  illustrates how the LEDs  42  can be controlled to precisely backlight symbols on a variety of reel strips, even through the reel strips may have different size symbol positions. On the left side of  FIG. 3  is illustrated the symbol positions of a reel strip A. The sizes of the top symbol position, the center symbol position, and the bottom symbol position are shown. For such a reel strip, it may be desirable to only associate the top two rows of the LEDs  42  with the top symbol, the middle three rows of LEDs  42  with the center symbol, and the bottom two rows of the LEDs  42  with the bottom symbol. The brightness of the various LEDs can be controlled so that the combined light output associated with each symbol is the same. 
   On the right side of  FIG. 3  is shown the reel strip B symbol positions for the top symbol, the center symbol, and the bottom symbol. In the case of reel strip B, the top three rows of LEDs  42  would backlight the top symbol, the bottom three rows of LEDs  42  would backlight the bottom symbol, and the middle three rows would backlight the center symbol. Any row can be dimmed to create a desired brightness profile behind a symbol. 
   If the designer of the slot machine wishes to highlight a particular symbol displayed, such as the “7” symbol in  FIG. 1 , the software may be written to blink on and off the LEDs that backlight the center “7” symbol in the middle row. Assuming reel strip B was being used, the software would cause the middle three rows of the LEDs in  FIG. 3  to blink, brighten, change color, or perform any other attention getting routine. If reel strip A were used, the designer may elect to brightly illuminate the middle row of LEDs and only dimly illuminate the rows above and below the middle row so that only the center symbol is highlighted. 
   Numerous other functions may be performed by the ability to selectively control the color and brightness of the various LEDs in the array. For example, a symbol or combination of symbols across the three or more reels may be highlighted by controlling the color, pattern, brightness, or any other attribute of the backlight. The LEDs may even be controlled to provide a star bursting pattern by, for example, illuminating the LEDs from the middle and then outward, to highlight special symbols. 
     FIG. 4  is a side view of a printed circuit board  50  forming a side portion  32  ( FIG. 2 ) of the assembly  20 . In  FIG. 4 , a single line of LEDs  54  is mechanically and electrically connected to board  50 . Each LED  54  has its leads electrically coupled to a connector  58  so that the brightness of each LED may be individually controlled or controlled as a group. When board  50  is affixed to frame  36 , the array of LEDs  54  forms a vertical strip of lights bordering the symbols on a single reel strip. LEDs  54  may be white light LEDs or may be RGB LEDs. A white light LED only has the ability to output white light. A white light LED is typically either a blue or ultraviolet LED with a phosphor coating that emits white light or emits a light that when combined with blue light appears to be white light. In one embodiment, all LEDs in the backlight assembly  20  are white light LEDs; however, the flexibility of the lighting display is reduced. 
   The effect of selectively illuminating the LEDs  54  on board  50  can create an attractive border light for each reel strip or can give the illusion of upward rotation or downward rotation by sequencing the lights from bottom to top or top to bottom to coincide with the rotation of the reels. Further, these lights may be used to identify a reel by only illuminating the lights for one reel. Additionally, in some slot machines, an award is only paid for combinations from the left to the right or from the right to the left. The LEDs  54  in board  50  may be illuminated so that the sequence of illumination across the whole front of the slot machine indicates that the winning symbol combination is from left to right or right to left. Such indication of the direction and the winning payline may also be made by controlling LEDs  42 . 
   For the LEDs  54  on board  50 , a side emitting LED lens may be appropriate such that the light is directed toward the player rather than across the front of the assembly. 
     FIG. 5  is a side view of a conventional plastic reel  60  being rotatably connected inside the slot machine. A support  62  connects the stationary part of the reel to the body  64  of the slot machine. A stepper motor (not shown) turns the plastic reel in either direction. The backlight assembly  20  is shown directly behind the periphery of the reel  60 , over which a reel strip is mounted, so the reel and reel strip do not contact the backlight assembly. The reel strip typically has 18, 20, or 24 symbol positions. 
   In front of the reel  60  is the transparent opening of the slot machine. In one embodiment, the transparent opening of the slot machine includes an edge lit sheet of plexiglass  66  and a touch screen  68 . The touch screen allows the player to make selections by touching areas of the touch screen displaying an image. The touch screen may display images in front of the reels or only display images around the periphery of the reels. The touch screen may include a liquid crystal layer and a thin film transistor array, forming a liquid crystal display (LCD), as well as a touch sensitive sheet over the LCD. The touch screen is backlit by the edge lit plexiglass, where the plexiglass has small ridges or other deformities that allow the light from the edge-feed to leak out the front of the plexiglass. Additional layers may be used in front of the reel. 
     FIG. 6  is a schematic diagram of various basic functional blocks in the slot machine related to the reel backlight assembly  20 . 
   In  FIG. 6 , a conventional CPU  70  in the slot machine that controls various functions of the game is programmed by software stored in a memory  72 . To control the reel backlight assembly  20 , the CPU generates a digital code which is then received and decoded by a driver board  74 . Driver board  74  contains various current controllers for selectively controlling the various LEDs in assembly  20 . The digital code, which may be a series of digital codes, identifies the various LEDs to illuminate at any brightness level. Alternatively, there may be a microprocessor (or other type of controller such as a programmable gate array) on driver  74  which receives a high level command code from the CPU  70  and associates that code with detailed instructions for controlling the LED assembly. Various current controllers  78  are then controlled to provide power to selected red, green, blue, or white LEDs to illuminate those LEDs with any brightness and any pattern. Power to the various LEDs may be controlled by pulsewidth modulation or any other technique. A multiplexer may be contained on driver board  74  for addressing the various LEDs to limit the number of current controllers. Techniques to selectively control LEDs are well known and need not be described in detail herein. The various power signals are applied to the connectors  80  on assembly  20  for energizing the various LEDs shown in  FIGS. 3 and 4 . Any of the circuitry described above may be located on assembly  20 . 
   The various reel assemblies  84  are also controlled by CPU  70  via driver  86  to begin rotation and stop rotation based upon the particular software program. The reel rotation and stopped positions may be coordinated with the light control signals for assembly  20  to highlight winning symbol combinations, special symbols, or other functions as previously described. 
   Having described the invention in detail, those skilled in the art will appreciate that given the present disclosure, modifications may be made to the invention without departing from the spirit and inventive concepts described herein. Therefore, it is not intended that the scope of the invention be limited to the specific embodiments illustrated and described.