WO2009068836A1

WO2009068836A1 - Method and apparatus for automated card identification and cards for use therein

Info

Publication number: WO2009068836A1
Application number: PCT/GB2007/004585
Authority: WO
Inventors: Kevan Moretti; Nick Bryan; Alan Edward Green; Simon Brown
Original assignee: Iknowledge Ltd
Priority date: 2007-11-29
Filing date: 2007-11-29
Publication date: 2009-06-04

Abstract

One embodiment of the invention provides a card for inclusion in a set of cards. A surface of said card is provided with a marking indicating the identity and/or value of the card. The marking is substantially invisible to the naked eye but detectable using non-visible radiation. The marking is formed using at least first and second inks. The first and second inks are substantially identical to the naked eye, but have contrasting properties for the non- visible radiation.

Description

METHOD AND APPARATUS FOR AUTOMATED CARD IDENTIFICATION AND CARDS FOR USE

THEREIN

Field of the Invention

The present invention relates to a method and apparatus for automatically identifying cards for use in various applications, such as televising a card game, casino security measures, and computer gaming applications. The invention also relates to cards for use in such situations.

Background of the Invention

There has been significant growth in the last few years in the popularity of card and casino games such as poker. A major aspect of this popularity has been a large increase in the number of people participating in on-line games over the Internet. Another aspect is wider television coverage of players participating in such games, often for very substantial stakes. It will also be appreciated that there are very many television channels now available, whether via cable, satellite, or terrestrial broadcast (in analog or digital form), as well as webcast channels supplied over the Internet. These channels are all looking for content to fill their schedules, and casino games provide an opportunity to offer interesting and exciting programming at reasonable production costs.

Most card games involve players receiving at least some of their cards face-down. The value of such a face-down card is known to the recipient of the card (who can look at the card), but not to any of the other participants in the game. However, broadcasters (including webcasters) generally want to be able to identify which cards a particular player is holding at any given time. This information can then be used to drive commentaries, for example in relation to the tactics adopted by a given player. Information about cards received face-down is also of great interest to viewers who are following the game, and helps them to appreciate the differing styles of players in the game.

Current programmes have generally used high-definition cameras to ascertain the values of face-down cards dealt to the players. In many cases, these cameras are positioned looking upwards from underneath a glass table top, so as to be able to see cards dealt face-down onto the table top. Alternatively (or additionally) cameras may be placed adjacent players, so as to acquire the same view of the cards as a player. In other words, when a player raises cards dealt face-down to review his or her hand, the faces of the cards are likewise visible to the camera.

Unfortunately, neither of these approaches is completely unsatisfactory. For example, a glass table-top provides a rather unnatural environment for a casino game, where cards are normally dealt onto a (non-reflective) baize surface. In addition, cards may lie on top of another, so that a camera only has a clear view of the bottom card, but not of the other cards above (behind) this bottom card. The faces of the cards might also be obscured, at least in part, by a player's fingers or hands. (The pyschology of games such as poker is strongly against showing your hand to anyone, even television sponsors). It will also be appreciated that the use of multiple cameras can become quite complicated and expensive, especially if the number of players involved is relatively large.

Once the cards dealt to the players have been identified, this information is normally recorded into a computer system. The stored information about the cards dealt to the various players can then be used for a variety of purposes, such as to inform commentators. However, even after a camera image of a player's hand has been acquired, this still doesnot provide the card information directly for storage into a computer system. Rather, it is necessary to process an image obtained from the camera to deduce the identity of the card or cards shown in the image. Such image processing may be difficult in a casino environment, if the cards are poorly lit or held at various angles. Consequently, most casino programming relies upon a human operator to monitor the camera images in order to identify the various cards held by the players. The human operator is then responsible for entering the identity of the cards into a computer system such described above. However, such human operation may be prone to error, and in addition this approach becomes significantly harder as more players are involved in the game (say rising to 6-10 participants), in which case the operator has to cope with a large number of hands in a short period of time.

US 5259907 discloses a method for invisibly coding the face of a playing card so that it can be read by electro-optic means outside the visible range. US 2005/0051965 discusses various approaches to monitoring card games in a casino. These typically involve using an automatic card reader to identify cards as they are dealt from the shoe, and an overhead imaging system to track progress of the cards during the game. WO 2005/025701 and US 2003/0087696 also disclose a system for tracking and verifying card sequences during a card game. The system again uses an automatic card reader to identify cards as they are dealt from the shoe. The cards may be marked with machine-readable indicia such as a barcode which may be printed with infrared ink so as to be invisible to the human eye. The monitoring may be performed for casino security purposes. EP-A 1547659 discloses a system in which non-visible ink is used in a gaming system comprising multiple terminals, where the cards are entered into the terminals.

Summary of the Invention

One embodiment of the invention provides a card for inclusion in a set of cards. A surface of the card is provided with a marking indicating the identity of the card. The marking is substantially invisible to the naked eye but detectable using non-visible radiation. The marking is formed using at least first and second inks. The first and second inks are substantially identical to the naked eye, but have contrasting properties for the non-visible radiation. Such an approach avoids the use of specialist invisible inks for card marking, but rather allows conventional inks to be used, providing they have appropriate properties. The card may, for example, comprise a playing card, and the identity marking indicates the value of the playing card. Another possibility is that the card is a trading card for use with a computer game system, and the identity marking confirms the authenticity of the trading card as a bona fide card (without necessarily indicating the card value). Multiple cards may be formed into a set, and each card in the set may be provided with a consistent marking to confirm membership of the set and/or with a different marking (compared to the markings on the other cards) to uniquely identify the card within the set.

In one embodiment, the non-visible radiation comprises infrared radiation, for example in the range 780nm-920nm (in one particular embodiment, in the range 800-870nm). Such a range is invisible to the human eye, but can be readily imaged by existing (infrared) cameras. Other ranges for non- visible radiation can be selected as appropriate, whether different ranges of infrared radiation, or other regions of the spectrum, such as ultraviolet light.

In one embodiment, the contrasting properties of the first and second inks are that they have different absorption properties for the non-visible radiation. For example, the first ink may absorb the non-visible radiation, while the second ink may reflect (not absorb) the non-visible radiation. The marking therefore becomes apparent (to a suitable detector) when the card is illuminated with the appropriate non-visible radiation. Another option is to use inks that fluoresce in the presence of non-visible radiation, although such inks are generally more expensive.

In one embodiment, the surface of said card with the marking has a design pattern visible to the naked eye. The design pattern is printed using said first and second inks. In other words, the same inks are used for both the (invisible) marking and the (visible) design pattern, thereby simplifying card manufacture. The marking may be formed by printing selected regions of the design pattern with the first ink, and other regions of the design pattern with the second ink. These regions may conform to the structure of said design pattern. In other words, the structure of the marking is integrated into the structure of the design pattern, such that elements of the design pattern are also used to define the marking. This helps to avoid read interference between the design pattern and the markings, and also generally assists with the printing process.

The marking may comprise a barcode. A barcode has the advantage of being directly interpreted by a machine to access the value of the playing card (in contrast for example to an image, of the face of a playing card). In addition, barcodes are also specifically designed for robust and reliable reading. A further advantage of using a barcode is that even if there is any minimal residual visibility of the marking at visual wavelengths, it is still difficult for a human to decipher the barcode. However, any other appropriate form of marking can be used to identify the card instead of a barcode if so desired. For example, the card identity might be written in conventional characters on the card surface, or the marking might comprise a particular symbol to confirm authenticity. One possibility is to use a two-dimensional barcode for the marking. Such a barcode fits well the aspect ratio of a typical card, and also can be better matched to a card design pattern. Using a two-dimensional barcode generally requires an imaging detector to access the barcode. In contrast, a one-dimensional-barcode can be read by scanning with a simple scalar detector.

In one embodiment, the marking is covered by a plastic coating for the card. This protects the card (and also the marking) from damage.

Another embodiment of the invention provides a method for authenticating a playing card for use in a casino game. The method includes providing the back surface of each card with a marking that is substantially invisible to the naked eye, said marking indicating the identity of the card, including the card value; using a detector of non-visible radiation to access the marking on a card, thereby obtaining the card identity; authenticating the card based on the obtained identity; storing the obtained card value to produce a card-play history for the game; and automatically analysing the card-play history to identify any anomalous situation.

Such an approach can detect if an illicit card is used in a casino, in other words, one taken from another pack (whether from within or without the casino). Furthermore, the statistical analysis can detect potential fraudulent play, such as card swapping between participants, as well as system players. The marking may be made with the combination of first and second inks as discussed above, or by overprinting a conventional card with an ink that is invisible to the naked eye, but detectable using said non-visible radiation.

Another embodiment of the invention provides a method for authenticating a card for use with a computer game system providing a game environment. The method includes providing the surface of each card with a first marking that is substantially invisible to the naked eye, said first marking confirming the authenticity of the card, and a second marking visible to the naked eye containing information relevant to said game environment; using a camera sensitive to non-visible radiation to obtain a non-visible image of said card during the game; processing the non-visible image of said card to access the first marking thereon; authenticating the card based on the first marking; and controlling the game environment by the computer game system in accordance with the information from the second marking.

Another embodiment of the invention provides a computer game system for providing a game environment in conjunction with a set of cards, wherein the surface of each card is provided with a first marking that is substantially invisible to the naked eye, said first marking confirming the authenticity of the card, and a second marking visible to the naked eye containing information relevant to said game environment. The computer game system includes a camera sensitive to non-visible radiation to obtain a non-visible image of said card during the game; and a processor for processing the non- visible image of said card to access the first marking thereon and for authenticating the card based on the first marking; wherein the computer game system controls the game environment in accordance with the information from the second marking.

Such an approach can detect if someone is trying to use an illicit card with the game system, for example, a counterfeit or duplicated card. Thus it is much harder for an adversary, e.g. a forger, to copy the first, invisible marking, than the second, visible marking. The first marking may be made with the combination of first and second inks as discussed above, or by overprinting a conventional card with an ink that is invisible to the naked eye, but detectable using said non-visible radiation.

Brief Description of the Drawings

Various embodiments of the invention will now be described in detail by way of example only with reference to the following drawings:

Figure 1 is a high-level schematic diagram of apparatus for televising a card game in accordance with one embodiment of the invention;

Figure 2 is an example screen image as broadcast by the apparatus of Figure 1 in accordance with one embodiment of the invention;

Figures 3 A, 3B, and 3C are schematic diagrams of markings that may be applied to a playing card in accordance with one embodiment of the invention;

Figure 4B represents a visible image of the back surface of a playing card and Figure 4A represents an infrared image of the same surface, which includes an infrared marking, in accordance with one embodiment of the invention;

Figure 5B represents a visible image of the back surface of another playing card and Figure 5 A represents an infrared image of the same surface, which includes an infrared marking, in accordance with one embodiment of the invention;

Figure 6B represents a visible image of the back surface of another playing card and Figure 6 A represents an infrared image of the same surface, which includes an infrared marking, in accordance with one embodiment of the invention;

Figure 7B represents a visible image of the back surface of another playing card and Figure 7A represents an infrared image of the same surface, which includes an infrared marking, in accordance with one embodiment of the invention; and

Figure 8 illustrates the visible image of the back surface of a playing card;

Figure 9 illustrates an example of a two-dimensional barcode;

Figure 10 illustrates the two-dimensional barcode of Figure 9 incorporated onto the back surface of the playing card of Figure 8 in accordance with one embodiment of the invention;

Figure 11 is a flowchart of a method of televising a card game in accordance with one embodiment of the invention; Figure 12 is a flowchart of a method of authenticating casino operations in accordance with one embodiment of the invention; and

Figure 13 is a computer gaming system in accordance with one embodiment of the invention.

Detailed Description

Figure 1 illustrates in high-level form apparatus for televising a card game such as poker in accordance with one embodiment of the invention. As part of the card game, a playing card 10 is placed face-down onto a table surface 20. The playing cards used in casino games normally have a plastic laminate structure, typically based on PVC acetate or cellulose acetate, or a paper laminate structure, frequently with an exterior coating of PVC acetate or cellulose acetate. A typical dimension for playing card 10 is a height of 88mm, and a width of about 60mm (poker cards tend to be about 62 mm wide, but casinos often used narrower cards of about 57mm width for easier handling).

The top surface of playing card 10 (Le. the opposite surface to the face) incorporates an infrared marking that is described in more detail below. An infrared camera 60 is positioned looking down on playing card 10 (although camera or detector 60 may operate at other non-visible wavelengths if appropriate). In addition, a lamp 65 may also be provided to illuminate card 10, although in some embodiments lamp 65 may be omitted. Camera 60 and lamp 65 are discussed in more detail below.

The output of the camera 60 is passed to computer 40 (which may represent one or more separate computer systems). Computer 40 determines the identity (i.e. the suit and number) of playing card 10. This card identity is then stored for subsequent retrieval by editors, producers, and so on. In addition, the card identity is passed to a television graphics and character generator (TVCG) 45, which processes the data into pre-configured graphics layouts and templates to generate visual information indicative of the card identity. This visual information may be presented on-screen to a viewer of the televised card game in textual or graphical form. For example, a camera (not shown in Figure 1) may generate a live image of the 8ard game. This live image is then combined at mixer 70 with the visual information from TVCG 45 to produce the broadcast signal, which can then be transmitted to viewers from aerial 80. It will be appreciated that aerial 80 is schematic only, and may represent transmission over terrestrial, cable or satellite television services (analog or digital), as well as a web-cast over the Internet, some form of video downlink over a mobile or cellphone telephone network, or any other suitable form of distribution network. The television coverage of the card game may be provided simultaneously over multiple different networks. The television coverage may also be provided at a venue local to the card game itself, for example to assist spectators of the event.

The skilled person will be aware of many possible modifications to the embodiment shown in Figure 1. For example, although Figure 1 depicts the card game as being played on table 20, it will be appreciated that any suitable surface may be used. In addition, Figure 1 shows only a single infrared camera 60. In an alternative embodiment, table 20 or other surface is provided with multiple infrared cameras 60, where each camera is associated with a particular slot or bay on table 20. Each player (including the dealer, if appropriate) is then seated or otherwise located at his or her own bay, and cards for a given player are placed onto the table at the corresponding bay for that player (which may be indicated by appropriate markings on the surface of table 20). The cameras are arranged so that they are directed towards cards placed in the associated bay. This then allows computer system 40 to allocate each card to the corresponding player by virtue of which camera 60 detected that particular card. For example, if there are four players denoted A, B, C, and D, and four corresponding cameras 6OA, 6OB, 6OC, 6OD, then any card detected by camera 6OA is known to belong to player A.

In another embodiment, the system may be able to determine the identity of card 10, but not necessarily the player to whom the card has been dealt. In this embodiment, a human operator may provide this additional information to the computer system 40 (such as by using a keypad or other input mechanism, not shown in Figure 1). It will be appreciated that this is a much easier task than having to enter individual card values (as in the prior art), in that firstly the number of players in the game is generally much less than the number of different cards (fifty- two in a conventional pack), and secondly the cards are usually dealt to the players in a predictable order (clockwise round the table). This latter property may allow the system to predict which player will receive the next card, and this can then be provided as the default option for the human operator to confirm or deny.

In another embodiment, rather than having camera 60 directed at the surface 30 of the table, the camera may instead be directed towards the shoe from which the playing cards are dealt. In this embodiment, as a card is removed from the show, it passes the camera, which detects the identity (value) of the card. The allocation of this card to a particular player can then be entered separately into computer system 40 by a human operator (as described above).

The timing of the identification of the playing cards can be controlled in various ways. In one embodiment, each card is specifically placed into or moved across the field of vision of camera 60 before being passed to the relevant player as part of the deal. When the new card is placed in front of the camera, the identity of this new card is determined. Another possibility is for the dealer to trigger the identification process, for example via a floor pedal, which activates camera 60 to make an identification. In another embodiment, the camera may identify the cards on the table surface 20 in a continuous manner, and flag whenever the arrival of a new card is determined (i.e. a new card is identified that has not previously been allocated to a player). Alternatively, if infrared camera 60 is directed at the card shoe, then it can be arranged to identify each new card as it is dealt from the shoe.

Although Figure 1 shows a wired connection between the camera 60 and the computer system 40, it will be appreciated that this might be a wireless connection if appropriate, for example using a "wi-fi" local area network or similar. Likewise, the connections between the computer system 40, TVCG 45, mixer 70 and aerial 80 may of any suitable form, wired or wireless. In addition, although Figure 1 shows only a single table 20, it will be appreciated that computer system 40 may be linked to infrared cameras at multiple different tables 20. Furthermore, in other implementations, the functionality of mixer 70 and/or TVCG 45 may be performed in other systems, for example within computer system 40 itself, or within some other appropriate system.

Figure 2 represents a schematic illustration of the screen 200 broadcast by the apparatus of Figure 1 in accordance with one embodiment of the invention (in other words, screen 200 represents what a viewer would see on their television set or other reception equipment). It is assumed that there are two players participating in the televised card game, denoted player A and player B in Figure 2. A camera image 210 is shown of each player, which may be in the form of a single image of both players, or alternatively a separate camera image may be obtained for each player.

Beneath the camera image 210 of the players is a graphic region 220 that contains the visual information generated by TVCG 45. In the particular example shown, card graphic 220 provides a depiction of the three cards held by each player. The value of each card has been determined by using infrared camera 60. The card value is then shown in Figure 2 by appropriate lettering (e.g. 9H represents the nine of hearts, while KS represents the king of spades). However, it will be appreciated that the card graphic 220 may instead represent some visual image or animation of the corresponding card itself, rather than simply a textual indication of the card value.

In some implementations, especially for digital television, the display of card graphic 220 may be optional, and under the control of the viewer. For example, in such implementations, the user can decide whether they want to be able to view all the hands (via graphic 220), or perhaps none of the hands (whereby graphic 220 is removed from the screen). Another possibility would be for a viewer to select to see only certain hands in graphic 220. For example, viewer might opt to see the cards for player A, but not for player B. This would then allow the viewer to experience the game from the perspective of player A, and hence to compare how the viewer would play a hand against the way that player A actually plays the hand.

The information about the identity of the cards in the game can be used for a wide range of purposes, apart from just displaying an on-screen image or representation of the relevant cards such as shown in Figure 2. For example, data about card identities can be used to provide previews and forecasts as well as tournament statistics. Such additional facilities may be accessed via any suitable platform, for example a mobile telephone, a web client, a digital television set, and so on. The stored data in computer system 40 may also be used to support debate and analysis relating to previous games. Accordingly, it will be appreciated that the ability to provide rapid and reliable identification of cards as described herein can be used for entertainment, gaming or betting purposes, and helps to enhance production quality and/or to deliver additional revenue opportunities. In order for infrared camera 60 to be able to identify playing card 10, playing card 10 is provided with an infrared marking on the top or back surface of the card (i.e. opposite to the face). This marking can be based either on emission or absorption of infrared light; the former is accomplished with infrared fluorescent dyes, while the latter is accomplished with infrared absorbing dyes. Note that it is generally important that the markings are not visible to the naked eye (i.e. in visible light), so that the players cannot determine which cards the other players have been dealt.

Infrared fluorescent dyes absorb light in the visible spectrum and re-emit the light energy in the infrared spectrum. As a result, such dyes can utilise existing ambient (visible) light energy. Accordingly, lamp 65 may be omitted from the embodiment of Figure 1 if the ambient visible light level is sufficient for the infrared fluorescent dyes to produce an output that is bright enough in the infrared to allow camera 60 to read the relevant markings. Alternatively, lamp 65 may be retained to augment the visible light incident on the playing card 10, which in turn increases the output of the infrared fluorescence.

Because infrared fluorescent dyes absorb some light from the visible spectrum, they tend to be, to some extent, visible to the naked eye; in particular, they have the complementary colour to the light which they absorb. In practise, this effect tends to be small and the dyes appear quite covert.

There are relatively few infrared fluorescent dyes commercially available at present. In general, the absorption ("pump") and emission wavelengths are quite close together. This makes detection more difficult, as relatively sharp optical filtering is required to remove the pump wavelength in order to permit detection of the emitted wavelength (otherwise the light used to trigger the fluorescence may swamp the emissions). In addition, the fluorescence may be non-linear, so that the florescent intensity does not scale linearly with the pump intensity. As a result, relatively high pump levels are required to excite sufficient fluorescence for good detection. A further concern is that the efficiency of fluorescent dyes tends to degrade with time (in other words they produce less fluorescent emission for a given pump intensity).

In view of the above circumstances, the embodiment of Figure 1 has generally been developed and tested using infrared absorbing dyes, which are dyes that have little or no absorption in the visible spectrum, but absorb strongly in the infrared. Because such dyes do not make use of visible light (as do fluorescent dyes), they require illumination at infrared wavelengths. Thus in the context of the embodiment of Figure 1, if playing card 10 is marked with an infrared absorbing dye, then lamp 65 is an infrared lamp to provide infrared illumination.

There is a wide range of commercially available infrared absorbing dyes. Factors involved in selecting a dye for use in the context of the present invention include the strength of absorption in the infrared, residual absorption in the visible, solubility of the dye in various organic solvents, and wavelength of the absorption peak. High absorption in the infrared leads to easily detected features (Le. they will look "blacker" to the infrared camera). However, because the absorption of the dyes tends not to be very narrow in wavelength, there is normally an absorption tail that extends into the visible. Moving the absorption peak of the dye further into the infrared (i.e. towards longer wavelengths) therefore generally lowers the tail in the visible spectrum. On the other hand, the absorption peak does need to lie within the detection range of available cameras. Furthermore, because lamp 65 is used to supply infrared illumination, it is helpful if the peak absorption lies at a wavelength at which infrared LEDs are available. Taking into consideration the above criteria, the following two dyes were selected for testing: SDA6567 875nm dye and SDA7780 901nm dye, both supplied by H W Sands Corporation (see http://www.hwsands.com/) of Florida, USA.

Considering now the camera 60 from the embodiment of Figure 1 in more detail, cameras based on silicon detectors (either CCD or CMOS) are, in principle, sensitive into the near infrared spectral region, up to approximately lμm wavelength. However, such cameras often incorporate an infrared blocking filter, which is normally essential in colour cameras to prevent infrared radiation from causing unwanted colour effects. Monochrome cameras also generally have such an infrared filter to allow correct grey-scale representations hi visible light. The sensors in such cameras also vary in their infrared sensitivity to longer wavelengths.

In one particular implementation, the camera selected was the IDS uEyeUI-1220-M (from IDS Imaging Development Systems GmbH, of Obersulm, Germany, see http://www.ids-imaging.de/). This is a monochrome pVGA resolution (752 x 480 pixels) CMOS camera, with a USB2.0 interface. The camera has a global electronic shutter, which can be synchronised to external strobe illumination. The camera has excellent infrared response, which extends out to at least 900nτn. The camera incorporates an infrared blocking filter, which was replaced for the embodiment of Figure 1 by a piece of anti-reflection coated glass of equal thickness (this allows the camera to focus to infinity properly). A narrow band infrared filter (70nm bandwidth, centred at 880nm) on the camera lens provides rejection of ambient visible light.

Infrared LEDs used for remote control purposes emit infrared radiation at 880nm and are extremely cheap. They can be pulsed to high power (ten times their rated power) for short pulses (~100μs). In the embodiment of Figure 1, lamp 65 comprises an illumination system built from 50 such LEDs, which is synchronised to the electronic shutter of the camera 60. The illumination system gains its power from the USB interface via the camera.

Although lamp 65 provides customised illumination, it will be appreciated that many conventional (Le. visible) lights also produce a significant amount of infrared radiation, which may provide sufficient infrared illumination of playing card 10 to allow the infrared markings thereon to be detected. For example, the infrared illumination from standard television studio lighting may be sufficient for such purposes.

Various types of playing card 10 were studied using the imaging system of lamp 65 and camera 60. Those playing cards printed with red ink appear almost blank under the infrared illumination (i.e. little infrared absorption), and so allow easy detection of printed infrared absorption features. In contrast, playing cards printed with blue or dark colours are less suitable for use in the embodiment of Figure 1, as these colours are visible to the imaging system (Le. they tend to absorb infrared radiation) and hence tend to obscure any markings made with infrared absorbing ink.

The two selected dyes are soluble in a number of organic solvents, e.g. methanol, acetone, Methyl Ethyl Ketone (MEK), etc. As previously mentioned, most playing cards have a plastic coating, which is applied after the cards are printed. It was found that MEK temporarily softens the plastic surface. Consequently, dye carried in the solvent may be absorbed into the surface of the main layer of the card (rather than just remaining on the surface of the plastic coating), thereby making the dye markings resistant to damage by subsequent handling. Solutions of both dyes were prepared in concentrations from O.lmg/ml to a saturated solution of 30mg/ml. In one implementation, the printing onto the playing cards was performed by an ink jet printer in which a printer cartridge had been emptied and refilled with the infrared dye.

Many infrared dyes are not stable under ultraviolet illumination and tend to bleach in such circumstances. This can lead to a deterioration in the visibility of printed infrared absorption features over a few days under normal lighting. In addition, infrared printing may be slightly visible under glancing illumination where the surface has been softened by the MEK or a similar solvent. To assist with both of these effects, a clear UV absorbing coating (Lyson Print Guard) was applied by aerosol over the playing card 10. This coating helps to disguise any surface effects, as well as providing filtering of any incident UV radiation to increase the longevity of the infrared markings.

Two barcodes were generated for test printing. The first barcode, illustrated in Figure 3A, is a Code 128 barcode that encodes the text "Ace of Spades". This is a relatively high density code requiring small bar widths. Although this allows high density data storage, it also requires high realisation imaging for decoding. Since the embodiment of Figure 1 generally only involves encoding 52 different states (corresponding to the number of different playing cards), a much simpler code can be used.

Figure 3B illustrates a Code 2-5 interleaved barcode. To increase the bar width, thereby better matching the aspect ratio of playing card 10, this code was stretched horizontally, as shown in Figure 3 C. The stretched barcode as applied to a playing card of conventional size has a minimum feature width of ~2.5mm. Barcode scanners can typically decode with a resolution equivalent to just over 1 pixel per minimum feature, although in the embodiment of Figure 1 it is prudent to provide higher resolution, since the image of the card may need to be manipulated (e.g. rotated, scaled etc) before decoding. Assuming 2 pixels per minimum feature, camera 60 can cover an area of approximately 940mm x 600mm.

The 875nm dye SDA6567 was found to give higher contrast than the 901nm dye SDA7780, and so further experiments concentrated on this first dye. A concentration of 25 mg/ml for the dye in the solvent was found to give good contrast, with lower concentrations producing lower contrast. On the other hand, with increased concentration above 25 mg/ml the dye started to become visible to the naked eye.

Figures 4-7 illustrate results obtained using the 875nm dye SDA6567 at a concentration of 25 mg/ml for four different types of playing card. Thus Figures 4 and 5 involve red playing cards (Le. cards with a red backing pattern), Figure 6 involves a blue playing card, and Figure 7 involves a black playing card. The IR images have been processed to increase contrast, but have had no further manipulation. Results are shown for cards coated with a UV absorption layer (the results for such cards did not differ significantly from the results for cards without such coating).

The discontinuity seen in the printed barcodes in Figures 4-7 is due to a lack of calibration for the printer (such calibration is difficult with infrared inks, as the calibration patterns cannot be directly observed). This artefact does not prevent reading of the barcodes, and can be resolved with further calibration work. The best results in terms of infrared visbility of the barcode were obtained with the red-printed cards (Figures 4 and 5). The playing card shown in Figure 4 was particularly good, as the red ink used to print the backing of this card has very high reflectivity at 880nm, and hence the visible pattern on the back of this card (see Figure 4A) does not appear in the infrared image of Figure 4B. The playing card of Figure 5 A was not quite as good as the card of Figure 4A, in that some of the visible pattern (see Figure 5B) is still apparent in the infrared image of Figure 5 A. Nevertheless, the bar code of Figure 5A is still easily readable. On the other hand, the bar code of Figure 6A, which is encoded onto the back of the blue playing card of Figure 6B, is rather obscured, lacks contrast, and is difficult to read. Finally, the bar code of Figure 7 A, which is encoded onto the back of the black playing card of Figure 7B, is intermediate in outcome. Note that in all cases the printed barcode is substantially invisible in visible light (i.e. as per Figures 4B, 5B, 6B, and 7B).

The barcodes discussed so far have involved printing an invisible (in normal light) infrared ink onto the back surface of a conventional playing card. In another embodiment of the invention, the barcode or other marking is formed by printing two or more visible (in normal light) inks onto the back surface of a card. These inks are chosen to have substantially identical properties in visible light, such that for the human eye they appear to be the same colour. However, the inks have contrasting infrared properties. Accordingly, after printing different portions of the card surface with different inks, the cards have a uniform visual appearance (to the human eye), but a nonuniform appearance in the infrared, which can then be used to encode information.

Figure 8 illustrates a typical pattern on the reverse of a playing card. The pattern is shown as black and white, but might also be coloured, for example so that the dark squares are blue or red. (N.B. the very fine lines visible in Figure 8 are an artefact of the process for image generation, and do not appear on the actual card surface). Figure 9 illustrates a two-dimensional bar code pattern. Such two-dimensional barcode patterns are well- known to the person skilled in the art (see for example en.wikipedia.org/wiki/Barcode for links to a variety of coding schemes). A two-dimensional barcode pattern can be used for applying information to the back of the card, for example the card identity, in an analogous manner to the one-dimensional barcodes shown in Figures 3-7.

The barcode illustrated in Figure 9 can be applied to the reverse surface of a card by using two inks, which for ease of reference will be referred to as INKl and INK2. As discussed above, INKl and INK2 are substantially identical to the naked eye, but- have contrasting properties in the infrared. INKl is used to print the black parts of the barcode pattern shown in Figure 9, whileTNK2 is used to print the white parts (i.e. remainder) of the card. This is illustrated schematically in Figure 10, which shows the barcode of Figure 9 superimposed on the card pattern of Figure 8. Note that Figure 10 is indicative of how the card appears at infrared wavelengths; at visible wavelengths, the card still has a uniform appearance, such as shown in Figure 8.

It will be appreciated that for the particular card pattern of Figure 8, each block in the barcode pattern is split into four sub-blocks. The skilled person will be aware of a variety of techniques that can be used to compensate for this splitting, such as: limiting the resolution of the infrared imaging system; performing low-pass filtering of the infrared image of card (this removes high frequency variation), either in software or in hardware; and/or setting the feature size parameter in a barcode decoding algorithm to match the full-size blocks on the card. (N.B. image processing of the infrared image is discussed in more detail below).

The use of a two-dimensional barcode pattern such as in Figures 9 and 10 has certain advantages over the use of a one-dimensional barcode such as shown in Figures 3-7. Firstly, a two-dimensional barcode is better suited to the aspect ratio of a standard playing card, thereby allowing an increased amount of information to be stored more easily within the available card surface area. Furthermore, a two-dimensional barcode pattern generally conforms better to the design patterns that are typically used to mark the reverse of playing cards. In other words, such design patterns are generally two-dimensional in structure, and can therefore be adapted more readily to accommodate a two-dimensional barcode. This helps to avoid or reduce any interference between the barcode pattern and the underlying card design (such as is visible for example in Figure 6A), thereby making it easier to read the barcode pattern.

The use of two inks that are substantially identical in the visible but contrasting in the infrared, such as described in relation to Figures 8-10, has certain advantages over the approach set out in Figures 3-7, which uses a specialised infrared ink that is invisible to the naked eye for printing a barcode over the top of a standard card pattern. Thus specialised infrared inks (which are invisible to the naked eye) tend to be rather expensive, and may not have such good processing properties (e.g. drying) as standard inks. In contrast, the approach of Figures 8-10 is based on using more standard visible inks, albeit selected to be substantially identical in the visible but contrasting in the infrared. These standard visible inks are generally cheaper than specialised infrared inks, and may also have better processing properties.

Furthermore, the use of standard visible inks allows the barcode to be encoded into the underlying card design pattern, as described in relation to Figures 8-10. As noted above, this helps to avoid or reduce any interference between the barcode pattern and the underlying card design, which makes it easier to read the barcode pattern. (In contrast, if the barcode is printed with a specialised infrared ink that is invisible to the naked eye, this cannot contribute to the visual design pattern on the card).

The Table below lists example combinations of inks with contrasting properties to provide markings as described above - such inks as can be supplied by Intercolor Ltd of Essex, United Kingdom (see http://www.intercolor-ink.com/). For each pair of inks, the first ink appears relatively dark in infrared radiation (i.e. tends to absorb infrared radiation), while the second ink appears relatively light in infrared radiation (i.e. tends to reflect infrared radiation). The contrast rating is a visual assessment of the output from an infrared detector on a scale 1-5 (l=poor contrast, 5=excellent contrast). It will be noted that suitable ink pairs are available in a range of visible colours, such as black, blue, red, etc. (It will be appreciated that other embodiments may use other inks and ink combinations as appropriate).

Irrespective of the particular ink(s) and barcode structure used, once camera 60 has obtained an image of a card, such as shown in Figures 4A, 5 A, 6 A, 7 A, and 10, the image must be processed to access the barcode. The skilled person will be aware of various image processing algorithms that can be used for this purpose. Note that the exact image processing to be performed depends on the particular configuration of the system. Thus in some embodiments the orientation and location of the playing card may be known in advance, for example if newly dealt cards are always put onto table surface 20 in a predetermined position. In this case a section through the longitudinal centre of card image can be used to read the bar code. In other embodiments, the location and/or the orientation of the card image on table surface 20 may be uncertain e.g. the cards may be rotated at various angles on table surface 20. In this case the image processing algorithm first locates the cards (including their orientation), and then extracts the barcode. Further initial processing may be required if the cards are not necessarily flat on the table surface 20 (i.e. not necessarily perpendicular to the line of sight from camera 60).

In some embodiments, a visual camera may be provided in alignment with infrared camera 60. The visual camera may provide a better image for locating the positions and orientations of a card; once this has been done, the image from the infrared camera 60 can then be used to read the barcode for a card at a location and orientation as determined by the visual camera.

It will be appreciated that using a barcode on the back surface of the card to encode the value of a card permits a more robust identification of a card than image processing from the face of the card. In particular, barcodes have been especially designed for reliable machine processing, whereas the face sides of playing cards are often designed with regard to aesthetics and human interest. Accordingly, the embodiment shown in Figure 1 provides a more dependable machine-based identification of cards than prior art television systems, which often rely upon a human operator to input card values from a camera image.

The embodiment of Figure 1 is therefore based on using a camera 60 to obtain an image of the back surface of a playing card 10, with the resulting image then being processed to determine the barcode that identifies the playing card. In other embodiments however, rather than using a camera 60 to read the barcode, a barcode scanning system might be used instead. Such barcode scanning systems are well-known from supermarkets and other shops, and involve the barcode being scanned by a laser. The timing of the output from a point detector such as a photodiode is then used to determine the contents of the barcode being read (or the absence of any such barcode). Such a barcode scanning system can readily be applied to the embodiment of Figure 1. In particular, lamp 65 then comprises a laser (optical or infrared, depending on the properties of the relevant dye used for marking the cards - e.g. whether fluorescent or absorbing), while camera 60 comprises a photodiode sensitive to infrared radiation.

Figure 11 provides a flowchart that shows the televising of a tournament card game in accordance with one embodiment of the invention. The method begins by marking the backs of the playing cards to allow the cards to be identified (410). The markings may directly specify the value of the card, or may represent some identifier, such a barcode, that can be mapped or converted to the card value. The markings may be made at the time of manufacture of the playing cards or may be applied subsequently.

The card game commences, and is assumed to involve the dealing or distribution of one or more cards (420). An infrared detector such as a camera or photodiode is now used to access the markings on the playing cards (430). As described above, the timing or trigger conditions for performing such an operation can be configured according to the details of the embodiment and the particular television coverage (for example, as each new card is dealt, the markings on the card may be read). The data read from the playing cards is passed to computer system 40, which identifies the card value based on the data from the infrared detector (440) (unless this value is directly contained in the data itself). This may identification may involve (for example) processing an image from an infrared camera and/or performing some form of mapping or lookup based on a barcode value. The computer system 40 or TVCG 45 now generates a graphic based on the value of the card (450). This graphic may, for example, comprise text information, some form of image, some form of animation, or any combination of such elements as appropriate. The graphic is then incorporated into a broadcast signal (460) to provide viewers with an indication of the card that has just been dealt at operation 420. The digital information about the cards involved in the hand can also be used to drive programme analysis and comment, viewer input, betting, and so on.

Figure 12 illustrates another use of the card markings discussed above, in particular for casino security operations. The method commences substantially as described above in relation to Figure 11, whereby the cards are provided with a marking that is substantially invisible to the naked eye (510), such as illustrated in Figures 3-10. A card is then dealt (520) and imaged or scanned at a non-visible wavelength, such as in the infrared, to access the marking on the card (530). The marking is processed to confirm the card value and/or authenticity (540, 550). For example, regarding card authenticity, cards used in a casino may be provided with predetermined symbols (invisible to the human eye). These symbols can then be used to confirm that the cards in play are legitimate. The card values dealt are stored into a database (560), and are then available for analysis (570) to detect any statistical or other anomalies. For example, a card must normally be played by the person who received it from the dealer (players cannot exchange cards with one another). Also, it might be suspicious if a particular play received an unusually high proportion of favourable cards.

Such an approach can therefore validate the integrity of cards being used on the table as belonging to the casino, so that each card is confirmed as being an authenticated card belonging to the house, and taken from the card deck(s) currently in play. Secondly it can recognise individual card values for use in a computer application designed to identify unexpected card patterns dealt or in-play. The system can perform statistical analysis and judgments on expected playing occurrences, and in the case of exceptions or emerging trends, alert a floor manager or security to monitor and check what might be fraudulent play (rather than just a set of hands dealt and expected by chance). For example, the system can calculate expected odds and occurrences for normal "random" play in accordance with the number of packs currently in play. The system can then use standard statistical models and tests as well as self-learning artificial intelligence techniques (e.g. if >3 three of a kind cards are dealt in 20 hands for same play then alert) as the basis for a computation engine to signal exceptional card behaviour or an emerging exceptional run of winning occurrences. The system can re-run such play history remotely for security use and monitoring. Used in this way the system provides an effective tool to help combat fraudulent card play in a casino environment, whether by customers, casino staff, such as the dealers, or collusion between the two. It will be appreciated that although the flowchart of Figure 12 involves multiple levels of checking, based on both card authenticity and also card value, some systems may only implement a subset of these checks. For example some systems may just confirm card authenticity, without monitoring and analysing individual card values within a game.

Figure 13 illustrates a computer game system 600, such as a Sony Playstation3® system, which is linked to a television 645 or other visual console. (It will be appreciated that in other implementations, the computer game system may comprise a suitably programmed personal computer or workstation). Attached to the computer game system is a camera 660, for example a Sony Eyetoy® camera. The camera can image playing or trading card 610, which might for example depict a particular character, such as an animal or person. The computer game system processes the image received from the camera to identify the character(s) depicted on the card, which can then be imported into the game.

In existing implementations of a system such as shown in Figure 13, it is intended that consumers purchase additional cards 610 in order to be able to incorporate more characters (e.g. more powerful characters) into the game environment. However, there is a risk that the cards 610 are duplicated, such as by photocopying, thereby avoiding making any further card purchases, or that counterfeit cards become available.

Therefore, in accordance with one embodiment of the present invention, card 610 is provided with markings such as illustrated in Figures 3 to 10. These markings can confirm the authenticity of the card, and also, if so desired, the identity of the character depicted thereon. Note that the markings may be provided on the face of the card (or on the reverse of the card).

The system of Figure 13 is generally favourable to automatic image processing of the cards, since the way these games are played usually provides a clear and unobscured view of one side of the card. Such an approach allows the system illustrated in Figure 13 to automatically recognise card values and/or check the integrity of cards being used in a game as an authenticated card valid for game use. Information from the card can then be incorporated into the gaming environment, such as a character, playing attributes, and so on. Note that this information for incorporation into the gaming environment may be based on the visual appearance of the card (as for existing systems). Alternatively, the information may be encoded into the non-visible markings, along with the authentication marking. In this latter approach, the visual markings on the card might then just be used be humans, with the system instead relying on the information obtained at non-visual wavelengths.

There are various mechanisms for enabling camera 660 to read an infrared marking on card 610. Note that many existing digital cameras (based on charge-coupled devices, CCDs) are already generally sensitive to near- infrared radiation. Accordingly, one method to distinguish the infrared signal from the visual appearance of the card is for a user to place an infrared filter over camera; this filter would pass infrared radiation but block visible radiation. Some cameras may be able to switch such a filter automatically in and out of the optical path within the camera. Another option might be to rely just on the standard pixels, but only accept readings for the red pixels (this would be particularly suited to cards which produced relatively little visible red light, such as black inks). A further option would be to have two separate cameras, one for detecting the infrared marking on the cards, and another for detecting the visible markings on the cards. (In some cases these two cameras might be combined into a single device). On the other hand, some implementations may just involve an infrared camera (if the card identities can also be obtained this way, without using the visual information on the card).

Although the embodiments described above have primarily used infrared absorbing dyes to mark cards, other embodiments may use infrared fluorescent dyes instead. Note that infrared fluorescent dyes can give very good visibility since they are shifting energy from a shorter wavelength into a region that can be made spectrally quiet by suitable filtering of the ambient lighting. This can lead to a good signal to noise ratio, especially if the efficiency of such infrared fluorescent dyes improves in the future. In addition, although the embodiments described above have used barcodes for marking the playing cards, any other suitable form of markings might be used, such as lettering (e.g. 9S for 9 of spades). On the other hand, barcodes have the advantage of being robust in terms of identification, while at the same time difficult for humans to decipher (just in case there is any residual visibility of the marking on the backs of the playing cards in visible light). Furthermore, while the embodiments described above have used an infrared detector for accessing the markings on the playing cards, a detector at some other (non-visible) wavelength might be used instead, for example to detect ultraviolet radiation. Note that in this case, the markings could again be provided via emission (UV fluorescence) or absorption, and any illumination by lamp 65 would be at an appropriate wavelength (e.g. UV for UV absorbing ink).

In conclusion therefore, although a range of embodiments of the' invention has been described above by way of example, the skilled person will be aware of further possible variations and modifications. In addition, the various features described herein may be utilised in combinations other than those specifically set out above. Accordingly, the presented embodiments are not intended to be limiting, but rather the invention is defined by the appended claims and their equivalents.

Claims

1. A card for inclusion in a set of cards, wherein a surface of said card is provided with a marking indicating the identity of the card, said marking being substantially invisible to the naked eye but detectable using non-visible radiation, said marking being formed using at least first and second inks, wherein said first and second inks are substantially identical to the naked eye, but have contrasting properties for said non-visible radiation.

2. The card of claim 1, wherein said non-visible radiation comprises infrared radiation.

3. The card of claim 2, wherein said non- visible radiation comprises radiation in the range 800-920nm.

4. The card of claim 3, wherein said non- visible radiation comprises radiation in the range 875-905nm.

5. The card of any preceding claim, wherein the contrasting properties are that the first and second inks have different absorption properties for said non-visible radiation.

6. The card of any preceding claim, wherein the surface of said card with the marking has a design pattern visible to the naked eye, and said design pattern is printed using said first and second inks.

7. The card of claim 6, wherein said marking is formed by printing selected regions of said design pattern with said first ink, and other regions of said design pattern with said second ink.

8. The card of claim 7, wherein said selected regions and said other regions conform to the structure of said design pattern.

9. The card of any preceding claim, wherein said marking comprises a barcode.

10. The card of claim 9, wherein said marking comprises a two-dimensional barcode.

11. The card of any preceding claim, wherein the marking is covered by a plastic coating for the card.

12. The card of any preceding claim, wherein the card is a playing card, and the marking indicates the value of the playing card.

13. The card of any preceding claim, wherein the card is a trading card for use with a computer game system, and the marking confirms the authenticity of the trading card.

14. A set of cards comprising multiple cards according to any preceding claim, wherein each card in the set is provided with a different marking to uniquely identify the card within the set.

15. A method for authenticating a playing card for use in a casino game, said method including: providing the back surface of each card with a marking that is substantially invisible to the naked eye, said marking indicating the identity of the card, including its value; using a detector of non-visible radiation to access the marking on a card, thereby obtaining the card identity; authenticating the card based on the obtained identity; storing the obtained card value to produce a card-play history for the game; and automatically analysing the card-play history to identify any anomalous situation.

16. The method of claim 15, wherein said detector comprises a camera for obtaining an image of the card, said image being automatically processed to access the marking on the card.

17. A method for authenticating a card for use with a computer game system providing a game environment, said method including: providing the surface of each card with a first marking that is substantially invisible to the naked eye, said first marking confirming the authenticity of the card, and a second marking visible to the naked eye containing information relevant to said game environment; using a camera sensitive to non-visible radiation to obtain a non-visible image of said card during the game; processing the non-visible image of said card to access the first marking thereon; authenticating the card based on the first marking; and controlling the game environment by the computer game system in accordance with the information from the second marking.

18. The method of claim 17, wherein the first marking also includes the information relevant to said game environment from the second marking, and wherein said information is acquired by the computer game system for controlling the game environment by processing the non-visible image of said card.

19. A computer game system for providing a game environment in conjunction with a set of cards, wherein the surface of each card is provided with a first marking that is substantially invisible to the naked eye, said first marking confirming the authenticity of the card, and a second marking visible to the naked eye containing information relevant to said game environment, the computer game system including: a camera sensitive to non-visible radiation to obtain a non- visible image of said card during the game; a processor for processing the non- visible image of said card to access the first marking thereon and for authenticating the card based on the first marking; wherein the computer game system is operable to control the game environment in accordance with the information from the second marking.