Abstract:
The present invention is directed to a method for determining a position of each of a plurality of gaming chips on a gaming surface. Each of the plurality of gaming chips includes an inductively coupled RFID tag disposed therein. The gaming surface includes a first area and at least one second area disposed adjacent to the first area. The method includes transmitting a near-field inductively coupled interrogation signal to the plurality of gaming chips. A near-field inductively coupled response signal is received from at least a portion of the plurality of gaming chips. A position resolution action is performed in conjunction with either the step of transmitting or the step of receiving. Each of the plurality of gaming chips are associated with either the first area or the at least one second area in accordance with the step of performing a position resolution action.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This is a U.S. National Stage submission under 35 U.S.C. §371 of International Patent Application Serial No. PCT/CA2006/001716 filed on 20 Oct. 2006, International Patent Application Serial No. PCT/CA2006/001716 claims priority under 35 U.S.C. § 119 (e) to U.S. Provisional Patent Application Ser. No. 60/728,761 filed on 21 Oct. 2005, the contents of which are relied upon and incorporated herein by reference in their entirety. 
     
    
     1. FIELD OF THE INVENTION 
       [0002]    The present invention relates to a method and apparatus for the identification and position measurement of chips on a gaming surface. More specifically, the present invention relates to a method and system for improving the spatial resolution of magnetic coupling RFID technology to identify and measure the position of chips on precisely defined betting areas on a gaming table. 
       2. TECHNICAL BACKGROUND 
       [0003]    Casino managers have always been interested in being able to record in real time all the bets occurring within their premises. To do so a precise and reliable means of identifying the various chips (gaming tokens) placed inside and outside the betting zones, as indicated by gaming surface (gaming table) markings, is required. 
         [0004]    Such capability has, up to now, been impossible to achieve, within reasonable budgets and with existing technologies, but it nevertheless still remains extremely high in the list of the casino managers&#39; priorities. For example, such capability, combined with appropriate software, could allow the real-time automatic flagging of unusual events, the continuous tracking of the performance of individual players, as well as the assessment of the short, medium and long-term performance of casino personnel. 
         [0005]    During the past years, several approaches have been proposed to achieve this objective. In particular, approaches specifically based on radio frequency identification (RFID) technology have been patented. However, although promising, this technology presents a major drawback: it is not particularly precise in terms of spatial resolution and, as a result, its potential is limited to gaming surfaces with single betting areas, such as poker tables, or to tables with very spaced out betting areas. 
         [0006]    In fact, a commonly used type of RFID technology is based on radiated fields (far fields) operating at approved frequencies such as 433 MHz, 915 MHz, 2.4 GHz etc. Because of both its operating principle and the frequencies at which it operates, this technology is subject to effects that disturb the local field. For example antennas may be detuned by parasitic capacitance (people and metal objects), signals may be attenuated by the human body, and propagation may be affected by multi-path phenomena. Consequently, it is easy to see why, when dealing with gaming surfaces with multiple, closely spaced, betting areas, such as the ones used in blackjack or baccarat, or, even worse, with gaming surfaces in which chips may legitimately ride on the separation lines between betting areas, such as roulette tables, existing RFID based technology is inadequate. 
         [0007]    Magnetic coupling RFID based technology, operating at approved frequencies in the 125 KHz or 13.56 MHz bands, has been proposed to overcome these spatial resolution limitations. Because of the inherent “near field” characteristics of this technology, the signal dies off very rapidly beyond the intended coverage area and surrounding environment variations have much less of an impact. 
         [0008]    However, even though this technology is clearly superior to other existing RFID technology, it may not be, by itself, used to achieve accurate enough coverage over closely spaced betting zones. In fact, this is due to another requirement imposed by casinos: as chips may be stacked on top of each other, the technology has to allow communication with a chip on top of a stack, which may actually be up to 25 chips high. The magnetic field produced by an embedded loop is roughly spherically shaped and its “drop off” characteristics are determined by physics and may be expressed in dB/mm. To extend itself high enough to read the chips at the top of a stack, the magnetic field inevitably has to extend laterally as well. This implies that when the diagonal of the betting area is smaller than the height of the top of a 25 chip stack, and that an adjacent betting area is situated quite close to the observed betting area, it is generally impossible to achieve the required “drop off” characteristics. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention addresses the needs described above by accurately determining the position of a plurality of gaming chips disposed in closely spaced betting zones on a blackjack gaming table. 
         [0010]    One aspect of the present invention is directed to a method for determining a position of each of a plurality of gaming chips on a gaming surface. Each of the plurality of gaming chips includes an inductively coupled RFID tag disposed therein. The gaming surface includes a first area and at least one second area disposed adjacent to the first area. The method includes transmitting a near-field inductively coupled interrogation signal to the plurality of gaming chips. A near-field inductively coupled response signal is received from at least a portion of the plurality of gaming chips. A position resolution action is performed in conjunction with either the step of transmitting or the step of receiving. Each of the plurality of gaming chips are associated with either the first area or the at least one second area in accordance with the step of performing a position resolution action. 
         [0011]    Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the invention as described herein, including the detailed description which follows, the claims, as well as the appended drawings. 
         [0012]    It is to be understood that both the foregoing general description and the following detailed description are merely exemplary of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate various embodiments of the invention, and together with the description serve to explain the principles and operation of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a schematic illustration of a gaming table; 
           [0014]      FIG. 2  is a diagram of the magnetic flux lines of a coiled inductive coupler; 
           [0015]      FIG. 3  is a diagram of the magnetic flux densities of a coiled inductive coupler; 
           [0016]      FIG. 4  is a schematic representation of the jamming concept; 
           [0017]      FIG. 5  is a schematic representation of a coil set used in the jamming concept of  FIG. 4 ; 
           [0018]      FIG. 6  is a schematic representation of an alternative coil set used in the jamming concept of  FIG. 4 ; 
           [0019]      FIG. 7  is a diagram of the magnetic flux lines of a ferrite solenoid combined with ferrite director material; 
           [0020]      FIG. 8  is a diagram of the magnetic flux lines of a wounded ferrite solenoid combined with a ferrite field flattening plate; 
           [0021]      FIG. 9  is a diagram of the magnetic flux lines of two coiled inductive couplers combined in an active field shaping configuration; 
           [0022]      FIG. 10  is a schematic representation of the placement of ferrite solenoids under a gaming surface; 
           [0023]      FIG. 11  is a schematic representation of the internal circuits of a modified RFID gaming chip; 
           [0024]      FIG. 12  is a schematic representation of the positioning of the coiled inductive couplers of the circuit shown in  FIG. 11 ; 
           [0025]      FIG. 13  is a schematic representation of the internal circuits of another modified RFID gaming chip; 
           [0026]      FIG. 14  is a schematic representation of the flux density profiles of adjacent coiled inductive couplers; and 
           [0027]      FIG. 15  is a schematic representation of the signal envelop received at each coiled inductive coupler. 
       
    
    
     DETAILED DESCRIPTION 
       [0028]    Reference will now be made in detail to the present exemplary embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. An exemplary embodiment of the gaming surface of the present invention is shown in  FIG. 1 , and is designated generally throughout by reference numeral  10 . 
         [0029]    Generally stated, a method and apparatus according to illustrative embodiments of the present invention provide improved spatial resolution of magnetic coupling RFID technology used to identify the position of chips on precisely defined betting areas on a gaming surface, such as, for example, a gaming table. The method and apparatus provide gaming surface modifications which allow the use of magnetically coupled RFID gaming chips where tight spacing is needed and no “cross reading” of chips in other betting zones is desired. The use of “active field control” methods that consist of jamming loops, field shaping loops, ferrite solenoids and enhanced RFID measurements within the chip are described. 
         [0030]    Referring to  FIG. 1 , a common gaming surface which uses magnetic coupling technology is shown in the form of a gaming table  10  having betting areas A and B. The basic components of the gaming table  10  include a coil inductive coupler  12  with corresponding electronic circuitry  14  associated with each betting area (for the sake of clarity only those of betting area A are shown), a protective cover  16  with betting area markings  18  applied thereon and gaming chips  20 , all of which will be further detailed below. As those of ordinary skill in the art will appreciate, the coil inductive coupler  12  with corresponding electronic circuitry  14  may be referred to as the RFID interrogator assembly. 
         [0031]    The coiled inductive coupler  12 , referred to as the primary coil, is installed within the gaming table  10  and produces the read zone covering its associated betting area A, B within which gaming chips  20  have to be identified and counted. 
         [0032]    The electronic circuitry  14  produces the current flowing through the primary coil  12  and interprets (reads) the different signals induced by magnetic coupling in the primary coil  12  by gaming chips  20  placed inside an associated betting area A, B. 
         [0033]    The protective cover  16 , which may be, for example, a plastic sheet with felt carpeting, covers the primary coil  12  and its corresponding electronic circuitry  14 , and also provides a surface on which the betting area markings  18  may be applied and the chips  20  placed. 
         [0034]    Each of the gaming chips  20  integrate a coiled inductive coupler, referred to as the secondary coil, through which currents induced by magnetic coupling from the gaming table  10  primary coil  12  and by the other gaming chips  20  secondary coils flow, and an integrated circuit containing the appropriate gaming chip identification data, the circuit being capable of generating signals which may be used to transmit such data by magnetic coupling. 
         [0035]    It is to be understood that although the primary coil  12  and complementary electronic circuitry  14  of betting area A have been discussed, the same apply to any other betting area such as, for example, betting area B. 
         [0036]    Referring to  FIG. 2 , the magnetic flux  120  produced by the primary coil  12  is roughly spherically shaped and its “drop off” characteristics are determined by physics and may be expressed in dB/mm. To extend itself high enough to read chips at the top of a stack, such as the height of a 25 chip stack identified by line  22 , the magnetic field inevitably has to extend laterally as well. This implies that when the diagonal of the betting area is smaller than the height of the top of a 25 chip stack, and that an adjacent betting area is situated quite close to the observed betting area, it is generally impossible to achieve the required “drop off” characteristics. Referring now to  FIG. 3 , it may be seen that the magnetic flux  120  produced by the primary coil  12  of betting area A extends laterally, although with reduced density, into adjacent betting are B. 
         [0037]    In order to achieve improved chip  20  position measurement (0.5 inch or better), especially when the specification calls for stacks of up to 25 chips  20 , magnetic coupling technology may be combined with one or more complementary components and method of use thereof, either based on active field control using jamming coils or ferrite induced field deformation or on additional measurement techniques, such as received signal strength information (RSSI). 
         [0038]    Referring to  FIGS. 4 ,  5  and  6 , coil sets  42  comprising a primary coil  12 , referred to as the “read” coil, and one or more jamming coils  44 , one such set  42  being associated with each betting area A, B, may be used. To identify the gaming chips  20  within a specific betting area, the jamming coils  44  of all or some of the coil sets  42  are activated apart from the set situated in the betting area being observed. By cyclically multiplexing the jamming coils  44 , so as to serially observe each of the betting areas A, B; it is possible to precisely draw the complete picture of the bets on the gaming table  10  (or any other gaming surface). The jamming coils  44  may be “lateral” i.e. adjacent to and in the same plane as the read coil  12 , such as shown in  FIG. 5 , or concentric to and in the same plane as the read coil  12 , such as shown in  FIG. 6 . When concentric jamming coils  44  are used, two “read” operations are required; one when the jamming coils  44  are energized and one when they are not. The gaming chips  20  in the betting area may be found by subtracting the two lists of chips  20  obtained. 
         [0039]    In a first illustrative embodiment, shown in  FIG. 5 , the jamming coil  44  is adjacent and in the same plane as the read coil  12 , and is in the form of circuit loops of various geometries, which may include field canceling crossover patterns referred to as a “jammer loop”. 
         [0040]    In another illustrative embodiment, the coil set  42  may comprise a first circular, oval or square read coil  12  with a second concentric circular, oval or square jamming coil  44 , which is in the same plane and co-axial to the read coil  12 .  FIG. 6  shows an example where both the read coil  12  and jamming coil  44  are concentric circular coils. 
         [0041]    In a further illustrative embodiment (not shown), the coil set  42  may comprise an auxiliary coil associated with the read coil  12 , actively energized and phase coherent with the read coil  12  excitation, to shape the magnetic field of the read coil  12 . 
         [0042]    Read coils  12  in the gaming table  10  (or other gaming surface) are used to sense chips  20  in the betting areas A, B associated with each read coil  12  and are scanned in turn by a multiplexer. Associated with each read coil  12  are jamming coils  44  disposed as described above. The jamming coils  44  are activated to help restrict the reading zone of the read coil  12  by either splitting the signal and shaping the resulting field pattern or by generating a separate independent jamming signal. Referring back to  FIG. 4 , there is shown the read coil flux  120 A associated with betting area A and the read coil flux  120 B associated with betting area B. As it may be seen, when activated the read coil  12  of betting area A generates a flux  120 A that extends into betting area B delimited by betting area markings  18 B. When activated, the jamming coil  44  of betting area B generates a jamming flux  144  that prevents the read coil  12  from betting area A to read chips  20  located in betting area B. The jamming signal  144  may only be, for example, an in-band 13.56 MHz continuous wave (CW) signal at a level or 10 dB below the normal reader coil  12  received level. It is to be understood that other jamming modulations are possible depending on the RFID chip technology used. 
         [0043]    A further method is to use jamming coils  44  of various shapes to produce local area jamming signals that prevent chips  20  outside of the betting area being read from hearing and responding to the interrogation signals of the reader coil  12 . 
         [0044]    Using multiple active coils or specially shaped ferrite solenoids modifies the gaming surface  16  magnetic field so as to increase the drop-off slope around each betting area, A, B. By doing so the magnetic field around each betting area A, B may actually assume a more “rectangular shape” rather than “quasi-spherical”. Moreover, by combining this technique with the multiplexing of the active coils or the solenoids it may also be possible to further enhance the position accuracy of this improvement. 
         [0045]    In a first illustrative embodiment, shown in  FIG. 7 , a horizontal ferrite solenoid rod  12 ′ is used, instead of a coiled inductive coupler, below the plane of the gaming surface  16  and is placed in between two betting areas, here betting areas A and B. This construction produces a magnetic flux pattern  120  such that it passes perpendicularly up through one read zone (for example betting area B) and down through a second laterally adjacent read zone (for example betting area A). A ferrite director material  13  may be placed horizontally beneath the gaming surface  16  under each betting area A, B to widen the magnetic flux  120 . 
         [0046]    In another illustrative embodiment, shown in  FIG. 8 , a specially shaped ferrite solenoid  12 ′ with an excitation winding  15  is used, instead of a coiled inductive coupler  12 , below the plane of the gaming surface  16  and is placed in between two betting areas, here betting areas A and B. This construction produces a magnetic flux pattern  120  such that it passes perpendicularly up through one read zone (for example betting area B) and down through a second laterally adjacent read zone (for example betting area A). A ferrite director material  13  may be placed between the adjacent read zones, here betting areas A and B, to help ensure that the lines of magnetic flux  120  are more horizontal in the region where chips are not to be read. Flux  120  crossing through chips not in the read zones is minimized and consequently these chips may not be excited and read. 
         [0047]    In a further illustrative embodiment, shown in  FIG. 9 , an active inductive coupler coils  12 ″A,  12 ″B are used under respective betting area A, B in order to shape the magnetic field. For example, suppose betting area A is being read, then active inductive coupler coil  12 ″A generates flux  120 A. In order to shape flux  120 A so that it does not extend into the adjacent betting area, here betting area B, active inductive coupler coil  12 ″B is used to generate a small signal in phase, and at the same frequency, as that of active inductive coupler coil  12 ″A, thus producing flux  120 B which “pushes” flux  120 A back towards betting area A. 
         [0048]    Referring to  FIG. 10 , several multiplexed horizontally placed ferrite solenoids, L 1  though L 8 , are used, each interrogating only one or two betting areas at a time. For example, ferrite solenoid L 2  interrogates betting areas A and B. Since the end zones contain only one betting area each, namely betting areas A and G, the exact count of chips in each of the zones may be found by logical deduction. For example, ferrite solenoid L 1  reads the chips contained in betting area A, creating list A, while ferrite solenoid L 2  reads the chips contained in betting areas A and B, creating list AB. To obtain the list of chips contained solely in betting area B, that is list B, it suffice to subtract list A from list AB. Similarly, list C is obtained by subtracting list B from list BC obtained when ferrite solenoid L 3  reads the chips contained in betting areas Band C. This is repeated until the list of chips in each betting area is determined. It is to be understood that this method may be used with a lesser number of ferrite solenoids, for example using only ferrite solenoids L 1 , L 2 , L 4 , L 5 , L 6  and L 8 , but ferrite solenoid L 3  and L 7  may be used for redundancy purposes in this case. 
         [0049]    By introducing field measurement capability using received signal strength indication (RSSI) within the gaming chips and by knowing the exact field intensity level at each gaming chip, it is possible to calculate its distance from the device producing the magnetic field. By triangulation, i.e. by calculating the intersection of the circles situated at the distance corresponding to the measured field strength in three different field cases the exact position of the token may be determined. The three different field cases contemplated above may actually be produced, for example, by using three different devices situated in different locations or by a central device and additional devices that modify the magnetic field gradient. 
         [0050]    In a first illustrative embodiment, shown in  FIG. 11 , a gaming chip  20 ′ contains two side by side overlapping inductive coupler coils  52 ,  54 , and an RFID integrated circuit  56  capable of measuring the RSSI and communicating this measure as data along with its usual unique internal  10 . The inductive coupler coils  52 ,  54  are overlapped, as shown in  FIG. 12 , in such a way as to reduce mutual inductance. 
         [0051]    In another illustrative embodiment, shown in  FIG. 13 , a gaming chip  20 ″ contains a single coupler coil  53  and an RFID integrated circuit  58  capable of measuring the RSSI and communicating this measure as data along with its usual unique internal identification number ( 10 ), is used. 
         [0052]    To determine the position of a chip  20 ′ containing two side by side overlapping inductive coupler coils  52 ,  54 , the gradient of the magnetic induction field of the reader coil  12  is sensed by differencing the levels measured from each inductive coupler coil  52 ,  54  and dividing by their known separation distance. This gradient is then compared to calibrated radial measurements. Hence distance from the center of the betting area, which is usually circular in shape, may be determined. 
         [0053]    The method to determine the position of a chip  20 ″ containing a single inductive coupler coil  53  is to use the difference in RSSI as a measure of the values of the magnetic field produced by a single reader coil, which may be calibrated to the position of the gaming chip  20 ″ on the gaming surface  16 . 
         [0054]    Furthermore, signals from two or more interrogating read coils  12  may be used to measure the position of a chip  20 . Referring to  FIG. 14 , chip  20  senses the relative levels of the fields  120 A,  120 B and  120 C generated by read coils  12 A,  12 B and  12 C, respectively, as they are sequentially energized. This data, shown in  FIG. 15 , may then be used to form a distance measurement from the intersection of the field patterns and may be calibrated to a position on the gaming surface  16 . 
         [0055]    Although the present invention has been described by way of illustrative embodiments and examples thereof, it should be noted that it will be apparent to persons skilled in the art that modifications may be applied to the present illustrative embodiments without departing from the scope of the present invention. Furthermore, it is to be understood that the approaches described above may find applications other than gaming or betting surfaces and tables. In particular, they may be used in various “smart shelf” type applications to find and locate small closely spaced RFID tagged items such as, for example, test tubes; pill bottles; biological or forensic sample holders; stacks of documents, gem stone sample bags, etc. 
         [0056]    All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein. 
         [0057]    The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. The term “connected” is to be construed as partly or wholly contained within, attached to, or joined together, even if there is something intervening. 
         [0058]    The recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. 
         [0059]    All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate embodiments of the invention and does not impose a limitation on the scope of the invention unless otherwise claimed. 
         [0060]    No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention. 
         [0061]    It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit and scope of the invention. There is no intention to limit the invention to the specific form or forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the invention, as defined in the appended claims. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.