WO2007088251A1

WO2007088251A1 - Machine readable code and systems for reading the same

Info

Publication number: WO2007088251A1
Application number: PCT/FI2007/050059
Authority: WO
Inventors: Victor Zhitomirsky
Original assignee: Nokia Corporation
Priority date: 2006-02-02
Filing date: 2007-02-02
Publication date: 2007-08-09
Also published as: GB0602130D0; GB2434904A

Abstract

A machine readable code and systems for reading the code are described. The machine readable code is arranged so that in order to successfully read the code, the user must alter the code structure in such a way that it cannot be read again. In a preferred embodiment, the code structure includes two superimposed codes, with one of the codes being provided on a removable label. In this preferred embodiment, the code structure has to be read twice with the user being required to remove the label between the first and second readings. The code structures and code readers described can be used in a number of different applications, including a system that allows brand owners to reward consumers for brand loyalty.

Description

MACHINE READABLE CODE AND SYSTEMS FOR READING THE SAME

The present invention relates to machine readable codes and to systems and methods for reading such codes .

Barcodes have been used for many years to label products for inventory control and product identification at checkout stations. Barcodes have also recently been used for storing links to remote servers where information relating to a product or service can be obtained. Typically, the barcodes are printed onto the packaging of the product using conventional printing ink and then optically read with an optical barcode scanner. It is also known to use conductive ink to form barcodes and to read such barcodes using a capacitive barcode reader.

However, the inventor has realised that these conventional barcode structures have limited applicability and the aim of the invention is to provide a new machine readable code structure that will allow at least one new use for the codes.

According to one aspect, the present invention provides a use-once machine readable code. The machine readable code is use-once in the sense that the code structure includes means for allowing the disabling or destruction of the code. The means for allowing the disabling or the destruction of the code may be a removable label forming part of the code structure .

Such a use-once machine readable code can be used in a number of systems for which standard machine readable codes are unsuitable. For example, such use-once codes can be used to allow brand owners to provide loyalty rewards to consumers. They can also be used to authenticate products or to identify drugs within sealed syringes that are used in hospitals to ensure that the syringe has not been refilled once it has been used.

These and other aspects of the invention will become apparent from the following detailed description of exemplary embodiments, in which:

Figure 1 is a schematic diagram illustrating the main components of a brand loyalty reward system; Figure 2a schematically illustrates the form of a use- once barcode structure that is used in the system shown in Figure 1 ;

Figure 2b illustrates a removable label which forms part of the barcode structure shown in Figure 2a,-

Figure 3 is a block diagram illustrating the main components of a user' s mobile telephone forming part of the system shown in Figure 1;

Figure 4 is a flowchart illustrating the main processing steps carried out by a brand application module forming part of the user's mobile telephone shown in Figure 3;

Figure 5 are signal plots illustrating the form of signals obtained from an optical code reader and a capacitive code reader forming part of the user's mobile telephone shown in Figure 3 ;

Figure 6a is a block diagram illustrating the main components of a computer server forming part of a brand owner's website of the system shown in Figure 1; Figure 6b illustrates the form of the data stored within a product database forming part of the brand owner's website shown in Figure 1;

Figure 6c illustrates the data stored within a content database forming part of the brand owner's website shown in Figure 1 ;

Figure 7 is a cross-sectional view illustrating the sensing components of the optical code reader and the capacitive code reader forming part of the user's telephone shown in Figure 3;

Figure 8 is a circuit diagram illustrating the main components of excitation and sensing electronics that form part of the capacitive code reader of the user's mobile telephone shown in Figure 3 ;

Figure 9a is a signal diagram illustrating the form of an excitation signal generated by a pulse generator shown in Figure 8 ;

Figure 9b is a signal diagram illustrating the form of a modulation signal generated by a modulation signal generator shown in Figure 8; Figure 10a illustrates the scanning of a set of drive electrodes and a sensor electrode across a conductive bar of a capacitive barcode;

Figure 10b schematically illustrates the polarity of voltage pulses applied to the drive electrodes shown in Figure 10a during a first drive period;

Figure 10c schematically illustrates the polarity of voltage pulses applied to the drive electrodes shown in Figure 10a during a second drive period;

Figure 1Od are signal plots illustrating the way in which the signal obtained from the sensor electrode shown in Figure 10a varies with the relative rotation between the user's mobile telephone and the conductive bars forming the capacitive barcode;

Figure 11a schematically illustrates the form of an alternative arrangement of optical and capacitive code readers ;

Figure lib illustrates the form of a voltage level obtained by scanning the electrode structure shown in Figure 11a across a conductive bar of a capacitive barcode ;

Figure 12 schematically illustrates the form of alternative optical code reader and capacitive code reader;

Figure 13a schematically illustrates the form of another optical code reader and capacitive code reader;

Figure 13b schematically illustrates an alternative form of a capacitive barcode for use with the capacitive code reader illustrated in Figure 13a;

Figure 13c schematically illustrates the way in which the capacitive code reader of Figure 13a detects the conductive bars of the capacitive barcode;

Figure 14 illustrates the form of an alternative duel channel code reader;

Figure 15 schematically illustrates the form of an alternative barcode arrangement in which data is encoded magnetically within the barcode structure,- and Figure 16 schematically illustrates a further barcode structure in which a code is provided under an opaque label .

OVERVIEW

A first embodiment will now be described in which a "use-once" barcode is provided for allowing brand owners to provide loyalty rewards to consumers. As shown in Figure 1, a product 1 usually includes a label 3 identifying the brand that provides the product and a label 5 identifying the name of the product. In this embodiment, the product also includes a novel barcode structure 7 which can be read by scanning a barcode reader 9 (forming part of a consumer's mobile (cellular) telephone 11) over the surface of the barcode structure 7. In this embodiment, in order to read the barcode structure 7 successfully (for the loyalty reward) , the user has to scan the barcode structure 7 twice using the barcode reader 9 and between the first and second scans has to render part of the barcode structure 7 inoperative so that it cannot be read again.

In this embodiment, the barcode structure 7 carries data identifying how many similar products 1 have to be purchased and their barcodes scanned in a similar manner before the brand owner will provide a reward. A software module within the mobile telephone 11 stores this information until the required number of products have had their barcode structures 7 scanned. In this embodiment, the barcode structures 7 also carry data identifying a web address for the brand owner's website 12 and, once the required number of products 1 have been purchased and their barcode structures 7 scanned, the mobile telephone 11 transmits the barcode data identifying the products that have been purchased to the brand owner's website 12 via a mobile telephone base station 13, the telephone network 15 and the Internet 17.

Upon receiving this product information, a computer server 21 running the brand owner's website 12 uses the product information to access a product database 23 which identifies the reward to be given to the user. In this embodiment, the reward is some content, such as a piece of music or a video clip which is retrieved from a content database 25. The server 21 then transmits the retrieved content back to the user's mobile telephone 11 via the Internet 17, the telephone network 15 and the base station 13. Upon receiving the content, a player (not shown) within the mobile telephone 11 plays out the received content to the user, for example, on the display 27.

As those skilled in the art will appreciate, the brand loyalty system described above is only practical because the barcode structure 7 is rendered inoperative once the user has successfully read it using the barcode reader 9. In particular, conventional barcodes and conventional barcode readers cannot be used for such a brand loyalty application because users would be able to scan the same product several times and therefore obtain the reward without having to purchase the required number of products.

A more detailed description will now be given of the particular type of use-once barcode structure 7, the user's mobile telephone 11 and the brand owner's server 21 used in this embodiment.

BARCODE STRUCTURE

Figure 2 illustrates the form of the barcode structure

7 used in this embodiment. As shown, the barcode structure 7 includes an optical barcode 7-1 formed from conventional ink that is printed on a label 7-3. As shown more clearly in Figure 2b, a second capacitive barcode 7-2 is provided (on a substrate 7- 4) underneath the label 7-3. The capacitive barcode 7-2 is formed from conductive ink printed onto the substrate 7-4 and is referred to herein as a "capacitive" barcode as it will be read by a capacitive barcode reader. The label 7-3 is an adhesive label that allows it to be stuck on top of the capacitive barcode 7-2 and subsequently removed by the user pulling on tab 7-5. The adhesive used on the label is preferably chosen so that it loses its tackiness when the label 7-3 is removed by the user, thereby making it difficult for the user to replace the label back over the capacitive barcode 7-2. The types of adhesive that can be used on the label 7-3 are well known and will not be described in further detail here.

In this embodiment, the optical barcode 7-1 is intended to be used as a replacement of the conventional barcode printed on the product 1, so that the optical barcode 7-1 can be scanned multiple times by a conventional barcode scanner for inventory purposes, shopping checkout etc. Therefore, in this embodiment, the optical barcode 7-1 will be the same on all products of the same type. In this embodiment the capacitive barcode 7-2 includes the data identifying the number of similar products to be scanned and the brand owner's website 12.

Additionally, in this embodiment, the same capacitive barcode 7-2 is used on all products of the same type

(although, like the optical barcodes 7-1, different capacitive barcodes 7-2 will be used on different products) . Consequently, in order to try to prevent consumers from being able to abuse the loyalty system, the barcode structures 7 are made so that the software in the mobile telephone 11 can determine whether or not it is likely that it is the same barcode structure 7 that is scanned in the first and second scans mentioned above.

This is achieved, in this embodiment, by designing the manufacturing process used to make the barcode structures 7, so that there is a detectable variation between barcode structures 7 in the relative positioning of the two barcodes 7-1 and 7-2 when they are superimposed on each other. This can be achieved by relaxing the machine tolerances of the machine that sticks the labels 7-3 onto the substrate 7-4 carrying the capacitive barcode 7-2. Consequently, for any- given batch of the same product that is likely to be sold from a retail outlet, it is likely that there will be slight differences in the position (or registration) of the optical barcode 7-1 relative to the capacitive barcode 7-2. Therefore, by measuring the registration of the two barcodes 7-1 and 7-2 in each scan and by comparing the measured registrations obtained from the two scans , the software in the mobile telephone 11 can determine whether or not it is likely that it is the same barcode structure 7 that is scanned in the first and second scans.

As those skilled in the art will appreciate, for the software in the mobile telephone 11 to be able to make this determination, part of the optical barcode 7-1 must remain when the label 7-3 is removed by the user.

As illustrated in Figure 2b, in this embodiment, the label 7-3 includes two cut-out portions 7-3a and 7-3b (carrying respective portions 7 -Ia and 7-Ib of the optical barcode 7-1) which remain covering part of the capacitive barcode 7-3 when the user peels off the label 7-3. As will be described in more detail, leaving two portions of the optical barcode 7-1 (rather than just one) allows the software in the mobile telephone 11 to make the above determination more accurately.

As will be apparent from the above, the barcode structure 7 illustrated in Figure 2 is a "use-once" barcode as once the label 7-3 has been removed, it cannot easily be replaced in a manner that cannot be detected by the code reader software. In particular, if the user tries to replace the label 7-3 over the capacitive barcode 7-2, it will be very difficult for the user to ensure an accurate alignment between the portions 7-Ia and 7 -Ib of the optical barcode 7-1 which were not removed with the portions of the optical barcode 7-1 that were removed with the label 7-3, and such misalignment can be detected by the code reader software. Additionally, the replacement of the label 7-3 over the capacitive barcode 7-2 is also likely to cause variations in the signal levels obtained when reading the capacitive barcode 7-2 due to inhomogeneities in the surface of the replaced label 7-3 itself and/or inhomogeneities between the replaced label 7-3 and the portions 7-Ia and 7 -Ib that were not removed. Therefore, again, such second readings of the same barcode structure 7 can be detected by the code reader software and hence can be discarded.

MOBILE TELEPHONE

Figure 3 is a block diagram illustrating in more detail the main components of the user's mobile telephone 11 used in this embodiment. As shown, the mobile telephone 11 includes a transceiver circuit 31 and an antenna 33 for transmitting signals to and for receiving signals from the mobile telephone base station 13. The mobile telephone 11 also includes a loudspeaker 35 and a microphone 37 which are both connected to the transceiver circuit 31 so that the user can make and receive telephone calls in the usual way.

As shown in Figure 3, the mobile telephone 11 also includes a processor 41 which controls the operation of the mobile telephone 11 under control of various software modules stored within memory 43. In this embodiment, the memory 43 includes a brand application module 45 (which includes an optical code reader module 47 and a capacitive code reader module 49) , a web browser 51 and a working memory area 53. The processor 41 is connected to the transceiver circuit 31 which allows the web browser 51 to transmit information to and receive information from the remote server 21 via the telephone network 15 and the Internet 17.

Figure 3 also shows that in this embodiment, the user' s mobile telephone 11 includes an optical code reader 9-1 and a capacitive code reader 9-2 which together are arranged to read the barcodes carried by the barcode structure 7. In this embodiment, the code readers 9 are normally powered down to save battery power. Therefore, when the user wishes to scan a barcode structure 7, they must press an appropriate button (or sequence of buttons) on a keypad 55 to cause the processor 41 to execute the brand application module 45, which in turn powers up the code readers 9 and controls the reading process of the barcode structure 7 using the optical code reader module 47 and the capacitive code reader module 49. The way in which the brand application module 45 controls the reading process will now be described in detail.

BRAND APPLICATION MODULE

Figure 4 is a flowchart illustrating the main processing steps performed by the brand application module 45 to control the reading of the barcode structure 7. As shown, when the brand application module 45 is initiated, it initiates, in step si, the code readers 9 for the first scan of the barcode structure 7. During step si, the brand application module 45 also initiates the optical code reader module 47 and the capacitive code reader module 49 to process the signal values obtained from the respective code readers 9, until they detect the presence of the barcode structure 7 being scanned.

Figure 5 illustrates the form of the signal (V_o ^opt) obtained from the optical code reader 9-1 and the form of the signal (V_o ^cap) obtained from the capacitive code reader 9-2, when the code readers 9 are scanned over the barcode structure 7. As shown, the signal levels have peaks and troughs corresponding to whether or not the code readers 9 are above one of the bars that form the optical barcode 7-1 or the capacitive barcode 7-2. As those skilled in the art will appreciate, although Figure 5 illustrates continuous signals, the signal values output by the code readers 9 and stored within the working memory 53 are samples of these waveforms at the time instants represented by the vertical dashes through the time axis. In this embodiment, the sampling times of the two code readers 9 are synchronised and each signal sample is time-stamped so that the brand application module 45 can determine the relative position (i.e. the registration) between the optical barcode 7-1 and the capacitive barcode 7-2.

When the barcode structure 7 is detected, the capacitive code reader module 49 analyses the signal values of the sensor signals obtained from the capacitive code reader 9-2 and stores, in step s3, a value representative of those signal levels. This value may, for example, be the peak signal level, the average signal level obtained from the capacitive code reader 9-2 or the average dynamic range of variation of the signal levels obtained from the capacitive code reader 9-2. This representative value is stored for subsequent use during the second scanning of the barcode structure 7.

Although not illustrated in Figure 4, at step s3, the brand application module 45 also analyses the signal values of the sensor signals obtained from the capacitive code reader 9-2 to determine if there has been any evident tampering of the barcode structure 7. This can be done, for example, by determining if there is any significant variation in the dynamic range of the signal values across the scan, which is indicative of the scan being made of a barcode structure 7 whose label 7-3 has been removed and replaced. If the brand application module determines that there has been any tampering, then it rejects the scan and the processing returns to step si.

In step s5, the optical code reader module 47 and the capacitive code reader module 49 process the signal values stored in the working memory 53 from the respective code reader 9, to determine the barcode tag values (i.e. the l's and O's) represented by the optical barcode 7-1 and the capacitive barcode 7-2. In this embodiment, the brand application module 45 then stores, in step s7, these barcode tag values together with the signal values obtained from the two code readers 9 and their associated time-stamps, for use in verifying that the barcode structure 7 that is scanned during the second scan is the same (or is likely to be the same) barcode structure 7 and not one from another product of the same type.

The processing then proceeds to step s9 where the brand application module 45 initiates the capacitive code reader 9-2 and the optical code reader 9-1 for the second scan of the barcode structure 7 (once the label 7-3 has been removed by the user) . In this embodiment, in order to guide the user, the brand application module 45 outputs on the display 27, also in step s9, instructions to the user on how to remove the label 7-3 and how complete the second scan. In this embodiment, the user is given a limited period of time to peel off the label 7-3 and to perform the second scan, in order to make it difficult for a large number of different users to scan the same barcode structure 7 both before and after the label 7-3 has been removed. The brand application module 45 controls this time-out feature in steps sll and sl3. In particular, at step sll, the brand application module 45 starts a timer (not shown) and at step sl3, the brand application module 45 determines whether or not the timer has reached a predetermined time-out value. If it has, then the processing proceeds to step s14 where the signal values and the two barcode tag values are discarded from memory 43 and an error message is output to the user on the display 27.

If at step sl3 the time-out has not been reached, then the processing proceeds to step sl5 where the brand application module 45 again obtains the signal values {and their associated time-stamps) from the two code readers 9. The optical code reader module 47 and the capacitive code reader module 49 then determine whether or not the obtained signal values contain a code. If they do not, then the processing returns to step sl3. Once a code has been detected, the processing proceeds to step si9, where the brand application module 45 compares the signal levels obtained from the capacitive code reader 9-2 during the second scan with the stored signal level data obtained from the capacitive code reader 9-2 during the first scan. If the brand application module determines, at step s21, that the new signal levels are not significantly greater than the stored signal level data, then this indicates that the user has not removed the adhesive label 7-3. Therefore, in this situation, the processing returns to step s3 so that the user still has the opportunity to rescan the barcode structure 7 after removing the label 7-3.

If, at step s21, the brand application module 45 determines that the new signal levels are significantly greater than the stored signal level data, then the processing proceeds to step s23 where the optical code reader module 47 and the capacitive code reader module 49 process the signal values obtained from the second scan to determine the barcode tag values for any detected codes. As those skilled in the art will appreciate, what constitutes "significantly greater" will depend on the nature of the barcode structure (e.g. the conductivity of the capacitive barcode 7-2 and the thickness of the label 7-3) and the characteristics of the capacitive code reader 9-2, and will be defined in advance for a given system. In this embodiment, as parts of the optical barcode 7-1 remain after the user has peeled off the adhesive label 7-3, the optical code reader module 47 will detect parts of the original optical barcode tag value.

As is well known with barcode scanners, the sequence of signal values obtained from the barcode readers 9 depends upon the speed at which the user scans the readers 9 across the barcode structure 7. The processing carried out in steps s5 and s23 will include steps to determine a scanning speed value for the respective scans. This is typically achieved by detecting the presence of a predetermined bar pattern at the beginning and/or at the end of the barcodes 7. In step s25, these speed values are used to speed normalise the signal values obtained from the first and second scans so that the registration between the optical and capacitive barcodes 7-1 and 7-2 of the first scan can be compared with the registration between the optical and the capacitive barcodes 7-1 and 7-2 of the second scan.

As discussed above, only parts of the optical barcode 7-1 will remain in the second scan and therefore, in this embodiment, the brand application module 45 processes the barcode tag value obtained from the optical barcode 7-1 in the first scan to identify the corresponding parts from it that match with the parts of the barcode tag value obtained from the second scan. As those skilled in the art will appreciate, if the two barcode structures 7 that are scanned in the two scans are different, then it is unlikely that the brand application module 45 will be able to identify a match because it is unlikely that a second different optical barcode 7-1 will contain portions that match

(in value and position) with both the remaining portions 7 -Ia and 7 -Ib of the optical barcode 7-1. If the brand application module 45 finds a match between the two optical barcodes 7-1 from the first and second scans, then, also in step s25, it considers for each scan the registration between the matching portions of the optical barcode 7-1 and the underlying capacitive barcode 7-2.

In this embodiment, the brand application module 45 uses the speed values for the respective scans, to determine and compare the actual distance between selected barcode elements of the optical and capacitive barcodes 7-1 and 7-2 from the two scans. In particular, referring to Figure 2b, in this embodiment the brand application module 45 determines, for each scan, a measure of the distance (d) between the start of capacitive barcode element 50 and the start of optical barcode element 52. This distance measure for each scan can be determined by, for example: i) identifying within the time-stamped signal values obtained from the code readers 9 in the scan, where the capacitive barcode element 50 begins and where the optical barcode element 52 begins; ii) subtracting the time-stamps for the identified signal values to determine a time difference for the scan; and iii) multiplying the determined time difference with the corresponding speed value for the scan. In step s26, the brand application module 45 determines if it is likely that the two barcodes structures 7 that have been scanned in the two scanning steps are the same by determining whether or not the respective distances (d) that have been calculated match each other to within a predetermined tolerance. If they do not match, then the processing proceeds to step sl4 where the stored signal values are discarded and an error message is output to the user.

If they do match, then the processing proceeds to step s27, where the brand application module 45 stores the barcode values obtained from the optical barcode 7-1 and the capacitive barcode 7-2 within a non-volatile portion of the memory 43. The brand application module 45 also processes the barcode tag value obtained from the capacitive barcode 7-2, to determine the instructions for how many similar products have to be scanned before seeking the reward from the brand owner and to identify the link to the brand owner's website. The brand application module 45 also stores this information within the non-volatile portion of the memory 43. Finally, also in step s27, the brand application module 45 outputs a message to the user indicating that they have successfully scanned the barcode structure 7. In this embodiment, this success message also displays to the user the number of other similar products that still have to be purchased and scanned before a reward will be given.

When the brand application module 45 determines that the required number of similar products have had their barcode structures 7 scanned, it passes the stored barcode tag value for the associated product and the link to the brand owner's website 12, to the web browser 51. In response, the web browser 51 connects to the brand owner's server 21 and transmits the barcode tag value to the server 21 via the base station 13, the telephone network 15 and the Internet 17. In this embodiment, the brand application module 45 also passes an authentication code, which is unique to the brand application module 45 running on the user's mobile telephone 11, to the web browser 51 for sending to the brand owner's website for authentication purposes. The web browser 51 then waits to receive the content that is downloaded from the brand owner's website 12. Upon receiving this content, the web browser outputs the content to the user via the display 27 and/or the loudspeaker 35, depending on the content type .

BRAND OWNER SERVER

Figure 6a is a block diagram illustrating the main components of the brand owner's server 21. As shown, the server 21 includes an Internet interface 61 which is operable to send data to and to receive data from the Internet 17. As shown, the Internet interface 61 is connected to a processor 63 which operates in accordance with instructions stored within memory 65. In this embodiment, a loyalty software module 67 controls the operation of the processor 63 in order to control the reception of the data from the different user' s mobile telephones 11 and to provide appropriate content rewards back to the user telephones.

In operation, when the server 21 receives the barcode tag value and the authentication code transmitted from a user's mobile telephone 11, the loyalty module 67 uses the received authentication code to verify that the barcode tag value has been received from an authorised (and therefore trustable) source. If the barcode tag value has been received from an authorised source, then the loyalty module 67 assumes that the required number of similar products have been purchased and consequently uses the received barcode tag value to address the product database 23 to identify the reward to return to the user. Figure 6b illustrates the data stored within the product database 23. As shown, the database 23 stores, for each barcode tag value 71, an associated product ID 73 that identifies the product and a content code 77 that identifies content to be returned to the user's mobile telephone 11 in reward for purchasing the required number of products. In this embodiment, the loyalty module 67 uses the received barcode tag value 71 to retrieve the associated content code value 77 from the product database 23. It then uses this content code value 77 to address the content database 25.

Figure 6c illustrates the data stored within the content database 25 in this embodiment. As shown, the content database 25 stores, for each content code value 77, a link to the appropriate content that should be returned to the user. In this embodiment, the content itself may be stored within the content database 25 or it may be stored in another server (not shown) . In either event, the loyalty module 67 uses the content storage location 79, for the content code obtained from the product database 23, to retrieve the appropriate content which it then returns to the user's mobile telephone 11 via the Internet interface 61. As illustrated in Figure 6c, different types of content may be stored within the content database 25, such as MPEG video files, MP3 music files etc.

CODE READERS

In this embodiment, a novel capacitive code reader 9-2 is used in combination with a conventional optical type code reader 9-1. However, a novel physical arrangement of the sensing elements of the optical code reader 9-1 and the capacitive code reader 9-2 is provided that allows the two code readers 9 to be able to sense the respective optical and capacitive characteristics of the same portion of the barcode structure 7 at the same time. Therefore, a more detailed description of the code readers 9-1 and 9-2 that are used in this embodiment will be given.

Figure 7 is a cross-section through part of the user's mobile telephone 11 illustrating the main components of the optical code reader 9-1. In this embodiment, the optical code reader 9-1 includes a light source 101 which generates and outputs a beam of light which is guided along a light guide 103 to a spherical lens 105. The spherical lens 105 focuses the light through an opening 107 of the mobile telephone housing 109. Light that is reflected and scattered back from the optical barcode 7-1 enters the opening 107 and passes through the spherical lens 105 to a photodetector 111. When the spot of light falls on a dark area of the optical barcode 7-1, the amount of reflected light will be low and therefore the voltage level output from the photodetector 111 will also be low. In contrast, when the spot of light is incident on a white part of the optical barcode 7-1, more scattered light will be reflected back towards the photodetector 111, resulting in a larger signal level from the photodiode. The signal from the photodiode 111 is then passed to an appropriate amplification and analogue-to-digital conversion circuit (not shown) before being passed to the working memory 53 for processing by the optical code reader module 47 in the manner discussed above.

Figure 7 also illustrates, on the right-hand side of the figure, an arrangement of electrodes 113 which form part of the capacitive code reader 9-2. These electrodes 113 are mounted on the end face 115 of the mobile telephone housing 109. As shown, the electrode arrangement 113 includes a central ring electrode 117 having a central aperture 119 coaxially arranged with the opening 107 that is connected to the sensor electronics and will therefore be referred to as the sensor electrode S₁. In this embodiment, the arrangement of electrodes 113 also includes an outer ring of eight electrodes 121 to 128 that are connected to the drive electronics and will therefore be referred to as the drive electrodes D₁ to D₈.

Figure 8 illustrates in more detail the drive and sensor electronics that are connected to the drive and sensor electrodes shown in Figure 7. As shown, the circuit includes a pulse generator 131 which is arranged to generate a periodic sequence of voltage pulses (illustrated in Figure 9a) having an amplitude of between 0.1 and 1 volt, duration of 10 nanoseconds and a pulse repetition frequency of 100 nanoseconds. The voltage pulses output by the pulse generator 131 are then passed to a mixer 133 where they are amplitude modulated by a modulation signal (illustrated in Figure 9b) generated by a modulation signal generator 135 or by a 90° phase-shifted version

of the modulation signal generated by the 90° phase- shifter 137. A switch 139 is provided for applying the modulation signal during first excitation periods

(labelled A) to the mixer 133 and for applying the 90° phase-shifted version of the modulation signal during second excitation periods (labelled B) to the mixer 133. As shown in Figure 9b, in this embodiment, the modulation signal is a sine wave signal having a frequency of approximately 1 kHz (i.e. having a period of approximately 1 millisecond) and a peak amplitude of between 0.1 and 1 volt.

As shown in Figure 8, the modulated pulses output from the mixer 133 are then passed to a first input terminal 141 of a multiplexer 143. The modulated pulses output from the mixer 133 are also passed to an inverter 145 which inverts the polarity of the modulated pulses and then inputs the inverted pulses to a second input terminal 147 of the multiplexer 143. As shown by the connections within the multiplexer 143, the non- inverted modulated pulses input at input terminal 141 are applied directly to electrodes D₁ and D₅. Similarly, the inverted modulated pulses are directly applied to electrodes D₃ and D₇. During the first excitation periods (A) , the non-inverted modulated voltage pulses are applied to electrodes D₄ and D₈ and the inverted modulated voltage pulses are applied to electrodes D₂ and D₆. During the second excitation periods (B) , the non-inverted modulated voltage pulses are applied to electrodes D₂ and D₆ and the inverted modulated voltage pulses are applied to electrodes D₄ and D₈. As shown in Figure 8, the multiplexer 143 controls the application of the drive signals to the corresponding drive electrodes through switches 149 and 151.

As represented by the dashed arrow 153, the triggering of the switches 139, 149 and 151 is controlled by a controller 153 so that all the switches are either in the position A or in the position B. In this embodiment, the controller 153 continuously switches between the two excitation periods (A and B) at a frequency of 100 Hz.

The modulated voltages that are applied to the drive electrodes D₁ to D₈, create electric fields around the array of electrodes 113. These electric fields couple into the sensor electrode S₁. As a result of the symmetric nature of the electrodes 113 and the symmetric way in which they are driven, when the electrodes 113 are adjacent a substrate of constant conductivity, the electric fields that couple into the sensor electrode S₁ cancel each other out. However, when the electrodes 113 straddle an edge of one of the bars of the capacitive barcode 7-2, the signals generated in the sensor electrode S₁ by these electric fields do not cancel with each other and therefore a signal is obtained from the sensor electrode S₁. This is because the amount of coupling between each drive electrode and the sensor electrode depends upon whether or not there is conductive material (such as the conductive bars that form the capacitive barcode 7-2) adjacent that drive electrode and the sensor electrode. In particular, the coupling between the drive electrodes which are located over the bar of the capacitive barcode 7-2 and the sensor electrode is greater than the coupling between the other drive electrodes that are located over the substrate and the sensor electrode (assuming of course that the substrate has a lower conductivity than the conductivity of the bars of the conductive barcode 7- 2) . Therefore, when the capacitive code reader 9-2 is scanned across the capacitive barcode 7-2, the capacitive code reader 9-2 will detect the bars (or at least the edges of the bars) of the capacitive barcode 7-2, thereby allowing the detection of the capacitive barcode 7-2. As those skilled in the art will appreciate, the amplitude of the signal obtained from the sensor electrode S₁ will vary with the amplitude of the modulated voltages that are applied to the drive electrodes D₁ to D₈. Further, as a result of the arrangement of the drive electrodes D₁ to D₈ and the way in which they are driven, the peak amplitude of the signal generated in the sensor electrode S₁ will also vary with the orientation of the drive electrodes D₁ to D₈ relative to the conductive bars that form the capacitive barcode 7-2, and hence with the direction in which the code readers 9 are swiped over the barcode structure 7. This is illustrated in more detail in Figure 10.

More specifically, Figure 10a shows the eight drive electrodes D₁ to D₈ and the sensor electrode S₁ when it is centrally positioned over one of the conductive bars 161 of the capacitive barcode 7-2. If the code readers 9 are swiped in the direction of the arrow 163, then the bars 161 of the capacitive barcode 7-2

will lie at an angle, Φ, to the scanning direction. Figure 10b illustrates the polarity of the modulated voltage pulses that are applied to the drive electrodes D₁ to D₈ during the first excitation periods (A) and Figure 10c illustrates the polarity of the modulated voltage pulses that are applied to the drive electrodes D₁ to D₈ during the second excitation periods (B) . As shown in Figure 10b, during the first excitation periods (A) , electrodes D₁, D₂, D₅ and D₆ all receive the inverted voltage pulses (represented by the minus sign) while drive electrodes D₃, D₄, D₇ and D₈ receive the non-inverted voltage pulses (represented by the plus sign) . Therefore, as can be seen from Figure 10a, during the first excitation periods (A)

and for this rotation angle Φ, the signal level generated in the sensor electrode S₁ will be at its peak negative value (as all the drive electrodes that are positioned over the conductive bar 161 receive the same inverted voltage pulses) . However, during the second excitation periods (B) and for this rotation

angle Φ, the drive electrodes which overlap with the conductive bar 161 (i.e. electrodes D₁ and D₂ and electrodes D₅ and D₆) are driven with opposite polarity voltage pulses and therefore the signals coupled into the sensor electrode S₁ from those drive electrodes will substantially cancel each other out, leaving substantially no sensor signal. The way in which the peak voltage obtained from the sensor electrode S₁ approximately varies with the relative rotation of the electrodes 113 and the bars 161 of the capacitive barcode 7-2 is illustrated in Figure 1Od. As shown, the variation in the peak amplitudes is approximately sinusoidal. However, note that this is an approximation and that the actual peak voltage level will not vary in an exactly sinusoidal

manner with the rotation angle Φ. The assumption of such a sinusoidal variation does not lead to a significant error in the results.

Consequently, the signal generated in the sensor electrode S₁ during the two excitation periods (A and B) can be represented by.

S₁ (A) = V₀ sin 2φ sin Irfj sin 2τιf_ext

S₁ (B) = V₀ cos 2φ cos 2τrfj sin 2πfJ

where f_m is the frequency of the modulation signal, f_ex is the frequency of the excitation pulses and V₀ is the amplitude term that depends on the presence or absence of a conductive bar 161 adjacent the electrodes 113. Figure 8 also shows the sensor electronics that are used to process the signal generated in the sensor electrode S₁. As shown, the signal from the sensor electrode S₁ is input to a mixer 154 where it is mixed with the excitation pulses generated by the pulse generator 131. This mixing is performed by a switch which is closed during the voltage pulses of the excitation signal and opened between the pulses . The action of the mixer 154 effectively allows the removal of the high frequency excitation pulses and isolates the electrode S₁ from the sensor electronics when there are no voltage pulses. As those skilled in the art will appreciate, the mixing leaves some unwanted higher frequency modulation components and the lower frequency modulation signal whose amplitude will depend upon the presence or absence of a conductive bar of the capacitive barcode 7-2 adjacent the electrodes 113. The output from the mixer 154 is then input to a switch 155, which is controlled by the controller 153 so that the signal output from the mixer 154 is passed to a low pass filter 157 during the first excitation periods (A) and to the low pass filter 159 during the second excitation periods (B) . As shown, the low pass filters 157 and 159 are formed by a standard active RC circuit and act to remove the unwanted high frequency modulation components output from the mixer 154.

The outputs from the two low pass filters 157 and 159 are then digitised by a respective analogue-to-digital converter 163 and 165. In this embodiment, the sampling frequency of the ADCs 163 and 165 is 30 kHz so that there are 30 samples of each period of the filtered signal per excitation period (A or B) . The digitised signal values obtained during the first excitation period (A) are then buffered in a buffer 167 until the corresponding signal values are obtained from the second excitation period (B) . At this stage, the corresponding digitised signal values obtained from the two excitation periods are added together in an adder 169 to give:

V_A + V_B = V₀ (sin 2φ sin 2πf_mt + cos 2φ cos 2τfj) = V₀ cos(2tfj - 2φ)

As represented by the dashed arrow 166, the timing at which the digitised signal values are added together is controlled by the controller 153 to obtain the above sum. As those skilled in the art will appreciate, the presence or absence of a bar 161 of the capacitive barcode 7-2 can be determined from the peak value (V₀) of the output from the adder 169 and the direction in which the code readers 9 are swiped across the barcode structure 7 can be determined from the phase of the signal output from the adder 169.

As shown in Figure 8, the value of V₀ and the value Φ during one combined excitation period (A and B) are determined by a peak amplitude detector 171 and a phase detector 173 respectively. In this embodiment, a timer 175 is provided to generate a time stamp for

each measure of V₀ and Φ, which allows the brand application module 45 to be able to compare the registration between the optical barcode 7-1 and the capacitive barcode 7-2 in the manner above. The

determined values of V₀ and Φ and the associated time stamp are then passed to the processor 41 for storage in the working memory 53 for use in determining the barcode tag value represented by the capacitive barcode 7-2. In particular, the individual values determined for V₀ for successive combined excitation periods (A and B) form the digitised signal values of V_o ^cap shown in Figure 5. These values are then processed in the manner described above to determine the barcode tag value. Although not mentioned above,

in this embodiment, the orientation information (Φ) provided by the capacitive code reader 9-2 is used to correct the registration data (i.e. the distances d) that are calculated by the brand application module 45 in order to take into account any differences in the swiping directions between the first and second scans.

MODIFICATIONS AND ALTERNATIVES

A specific example of a use-once barcode structure 7, of a particular combination optical and capacitive code reader 9 and of a particular application has been described above. As those skilled in the art will appreciate, whilst the above embodiment has been described in detail, various modifications and changes can be made and a description of some of these modifications and alternative embodiments will now be given.

In the above embodiment, the capacitive code reader 9- 2 included one sensor electrode and eight separate drive electrodes. As those skilled in the art will appreciate, the electrodes may be connected in the opposite manner, with a drive signal being applied to the electrode 117 and with the signals obtained from the individual electrodes 121 to 128 being processed by the sensor electronics. Alternatively still, the electrodes of the capacitive code reader 9-2 may be simplified to include a single sensor electrode and a single detector electrode. For example, the single drive electrode may be formed as a single ring electrode concentrically arranged with respect to the sensor electrode 117. As those skilled in the art will appreciate, with such a simpler design of electrodes, the capacitive code reader would not be able to determine any orientation information and will be sensitive to homogenous variations of the conductivity of the substrate which carries the capacitive barcode 7-2.

In the above embodiment, the sensing electronics of the capacitive code reader 9-2 was arranged to obtain signal samples during alternate drive periods (A and B) and to buffer the samples from the first drive period until the corresponding samples were available from the second sampling period. In an alternative embodiment, the electronics may be arranged to switch between the two drive periods at a much higher frequency than the frequency of the modulation signal (for example at a frequency of 100 kHz) , so that it is not necessary to buffer the signal samples from the first drive period before adding them with the corresponding samples obtained from the second drive period. Instead consecutive samples can be added together.

In the above embodiment, the optical code reader 9-1 and the capacitive code reader 9-2 were effectively point sensors that sensed the characteristics of a point on the optical barcode 7-1 or the capacitive barcode 7-2 as the reader is scanned over the surface of the barcode structure 7. Figure 11 schematically illustrates an alternative embodiment in which an elongate cylindrical lens 201 is provided for generating a line of light for scanning across the optical barcode 7-1. Two linear arrays of sensor electrodes 203 and 205 are provided on either side of the cylindrical lens 201. Finally, a pair of drive electrodes 207 and 209 are provided adjacent the respective linear arrays of sensor electrodes 203 and 205.

As represented by the plus and minus signs on the drive electrodes 207 and 209, in this embodiment, the electrode 207 is driven with a non- inverted drive signal and electrode 209 is driven with an inverted drive signal. Additionally, in this embodiment, the signal from each sensor electrode within the array 203 is summed with a corresponding one of the sensor electrodes within the array 205. This is illustrated in Figure 11a for the uppermost sensor electrodes within the arrays. As shown, the signals are summed together and then amplified in an amplifier 211 and a voltage level is measured at 213. As those skilled in the art will appreciate, by driving the drive electrodes 207 and 209 with opposite polarity voltage pulses and by summing the signals from adjacent sensor electrodes, any "common mode" signal is removed. This means that variations in the conductivity of, for example, the substrate on which the conductive bars of the capacitive barcode 7-2 are mounted will not effect the measurement .

Figure lib illustrates the voltage level measured by the meter 213 as the electrodes are scanned across the capacitive barcode in the direction represented by the arrow 215. A capacitive barcode aligned parallel with the drive electrode 207 and the arrays 203 and 205 of sensor electrodes results in a positive peak 217 when the drive electrode 207 and the array of sensor electrodes 203 are located over a bar of the capacitive barcode 702 and a negative peak 219 when the bar of the capacitive barcode 702 is located under the drive electrode 209 and the array of sensor electrodes 205. The code reader software can then detect the presence of the bars that form the capacitive barcode 7-2 by processing the voltage levels obtained from each pair of sensor electrodes. Further, the relative rotation between the bars of the capacitive barcode 7-2 and the arrays of sensor electrodes 203 and 205 can be determined from the relative timing of the pulses that are obtained from different pairs of sensor electrodes.

One of the advantages of the code reader illustrated in Figure 11a is that it can be used to read two- dimensional barcodes, which allows more data to be stored within the barcode structure 7.

One of the problems with the code reader illustrated in Figure 11 is that if there are any variations in the amplitudes of the drive voltages applied to the electrodes 207 and 209, this will result in an error in the measured voltage. Figure 12 illustrates an alternative arrangement in which the drive electrodes 207 and 209 are split into two so that a positive and negative drive electrode is provided on each side of the elongate cylindrical lens 201. As shown, the drive electrode 207 has been split into two electrodes - 207a and 207b; and the drive electrode 209 has been split into two electrodes - 209a and 209b. As shown, the signal levels from sensor electrodes 221 and 223 are added together and applied to the positive input of the amplifier 225 and the signals from sensor electrodes 227 and 229 are added together and input to the negative terminal of the amplifier 225. With the electrode arrangement illustrated in Figure 12, the circuit becomes insensitive to variations in the background conductivity and also to variations in the drive signal amplitudes.

Figure 13 illustrates another alternative arrangement of the code readers 9. In particular, Figure 13a illustrates an outer surface of the user's mobile telephone 11 having two optical code readers 9-Ia and 9-lb positioned either side of a capacitive code reader 9-2. Figure 13a also illustrates two rollers 241 and 243 which are designed to roll along the length of the barcode structure 7 being scanned and to provide a grounding point for the capacitive barcode 7-2. Figure 13b illustrates the modified form of the capacitive barcode 7-2 used in this embodiment. As shown, one end of all the conductive bars 161 that form the capacitive barcode 7-2 are connected together by a conductive strip 247. The provision of the conductive strip 247 allows all of the conductive bars 161 that form the capacitive barcode 7-2 to be coupled to ground through the coupling between the strip 247 and the grounded rollers 241 and 243.

Figure 13c illustrates the principle of operation of the capacitive barcode reader 9-2 used in this embodiment. In particular, Figure 13c illustrates the spherical ball 251 of conductive material which protrudes from the surface of the mobile telephone housing and which is arranged for rotation along the surface 253 of the barcode structure 7 being scanned. Figure 13c also illustrates a drive electrode 255 which receives a drive voltage V_DRIVE. This voltage creates an electric field between the drive electrode 255 and the conductive ball 251. Additionally, as a result of the grounding of the conductive bars 161 that form the capacitive barcode 7-2, the voltage developed on the ball (V_BALL) depends on the level of the drive voltage, the separation (Δ_o) between the drive electrode 255 and the spherical ball 251 and the separation (A₁) between the spherical ball 251 and the conductive bar 161, as follows:

V - ^Δi V ^^~Δ,+Δ₀ ^DNVE

As those skilled in the art will appreciate, this voltage level will vary depending on whether or not the spherical ball 251 is adjacent a conductive bar 161 of the capacitive barcode 7-2. Figure 13c also shows a sensor electrode 259 that is positioned adjacent the spherical ball 251. The voltage level (^V _SEN) generated on the sensor electrode 259 will depend upon the voltage acquired by the spherical ball 251 and will therefore depend upon whether or not the spherical ball 251 is adjacent a conductive bar 161.

In this embodiment, two optical code readers 9-Ia and 9-Ib are provided which are separated apart from each other along the scanning direction. This allows the code reader software to be able to detect the scanning speed of the code readers 9 by correlating the signals obtained from the two optical code readers 9-Ia and 9- Ib given the known separation between the two.

In all of the above embodiments, at least two code readers were provided, one for sensing optical characteristics of an optical barcode and one for sensing capacitive characteristics of a capacitive barcode. As those skilled in the art will appreciate, the systems described above can operate using a combination of other types of sensors. For example, the capacitive code reader 9-2 may be replaced by an inductive code reader which is arranged to sense the magnetic field pattern of a magnetic code. Similarly, a system may be provided which employs a capacitive code and a magnetic code and which employs a magnetic code reader and a capacitive code reader.

Further still, the above embodiment may be modified so that two optical codes are used. In this case, the optical codes are preferably printed on the code structure in different colours (or one infrared and the other visible) so that each of the codes can be differentiated by the code readers. Figure 14 illustrates one way in which the code readers of such an embodiment could operate. In particular, Figure 14 shows a code reader 270 having an optical lens 271 for capturing light reflected from the optical codes. The light may be generated by light sources (not shown) provided adjacent to the lens 271. As shown, the light enters the lens 271 and is passed to a beam splitter 273. The beam splitter 273 acts to allow part of the incident light through to an optical filter 275 and to reflect the remaining part of the incident light to a filter 277. In this embodiment, the filter 275 is arranged to filter out all frequencies of light except for blue light so that only the blue light within the reflected light passes to a first photodetector 279. Similarly, in this embodiment, the filter 277 is arranged to filter out all frequencies of light except for red light so that only red light within the reflected light passes through to a second photodetector 281. In this way, by arranging the barcode structure 7 to have two barcodes superimposed on top of each other, with one barcode being formed from blue material and the other barcode being formed from red material, the two optical barcodes can be separated through the action of the filters 275 and 277. It is therefore possible, through the processing of the signals output from the photodetectors 279 and 281, to determine the barcode values for each of the two optical barcodes through suitable processing by the code detectors 283 and 285. As those skilled in the art will appreciate, in such an embodiment, where a similar two layer barcode structure 7 is to be used, the adhesive label 7-3 would have to be made from transparent material (or thin paper material) so that the two barcodes can be read both before and after removing the label 7-3.

In the above embodiments, a barcode structure 7 and a code reader 9 were provided which required the user to scan the barcode structure twice and which required the user to render one of the barcodes inoperative before the barcode structure could be scanned successfully. The purpose of this was to provide a barcode structure 7 that could be read a limited number of times (preferably once) for the loyalty scheme. Other types of barcode structures and code readers can be used to achieve the same result.

Figure 15 illustrates an alternative code arrangement where a film of magnetic material 301 is provided having machine readable data recorded in the film 301 by varying the magnetisation state of the film 301. This variation in the magnetisation state is represented in Figure 15 by the different directions of the arrows 303. In such an embodiment, the code reader would have a magnetic head for sensing the magnetic state of the film 301 as the code reader is scanned across the film 301. This magnetic code may^¬ be combined with a second code, such as a capacitive code or an optical code as in the first embodiment.

In the above embodiments, a barcode structure 7 was provided having two superimposed barcodes. As those skilled in the art will appreciate, it is not essential to use this kind of barcode structure. Figure 16 illustrates an alternative arrangement of barcode structure 7 in which an optical barcode (not shown) is provided under an opaque label 311. In this embodiment, the optical barcode provided under the label 311 is formed from ink which reacts with light and/or the atmosphere and becomes transparent after a few seconds of the label 311 being removed. Therefore, in this embodiment, when the user peels the label 311 to reveal the optical barcode (not shown) they have a limited period of time (typically a few seconds) to scan the barcode using an appropriate barcode reader. In this way, the barcode structure 7 used in this embodiment is a "self-destruct" barcode. As those skilled in the art will appreciate, in this embodiment, a conventional barcode reader can be used to read the barcode before it becomes transparent . In a variation of this alternative embodiment, instead of the barcode oxidising and becoming transparent, the background of the substrate carrying the barcode may be arranged to oxidise and change colour so that it hides the barcode or at least changes the contrast between the barcode and the background so that the change in contrast can be detected by the reader which can then confirm that the label has been removed. Suitable inks and dyes that can be used in this embodiment are described in EP-A-1263599, the contents of which are incorporated herein by reference .

In all of the embodiments and modifications described above, the code readers were designed to read barcodes. As those skilled in the art will appreciate, it is not essential that the code or codes that each product carries are barcodes. Other machine readable codes or symbols may be used.

In the first embodiment described above, an adhesive label was provided carrying an optical barcode. The purpose of the adhesive label was to allow the user to be able to remove at least part of the optical barcode from the barcode structure so that it can not be read again. As those skilled in the art will appreciate, other techniques can be used to provide this functionality. For example, part of one of the codes may be provided on a layer of material which is designed to be scraped off by the user, for example using a coin.

In the above embodiments, a brand loyalty scheme was described which relied on the use of "use-once" barcodes. As those skilled in the art will appreciate, the above-described barcode structures and code readers can be used in other systems either separately or together. For example, they can be used to authenticate products. For example, in medical applications, the use-once barcode structure may be provided on a medical device filled with predetermined drugs. In order to dispense the drugs, the medical device would be such as to require the user to destroy the barcode structure before the drug can be administered. In this way, users would be able to verify that the medical device carries the specified drug and has not been refilled with another drug. Various other uses will be apparent to those skilled in the art .

In the first embodiment described above, the brand application module 45 (stored in the user's mobile telephone 11) monitored the number of barcode structures 7 the user has scanned and only connects to the brand owner' s website 12 once the required number of barcodes have been scanned. As those skilled in the art will appreciate, some of this functionality may be moved to the brand owner's server 21. For example, in an alternative embodiment, the brand application module 45 may be arranged to transmit the barcode tag values together with ID data for the user each time the user scans a barcode structure. The brand owner's server 21 would then be responsible to monitor the barcode tag values received for all the different users and to provide the content reward as soon as the required number of barcodes have been read by each user. However, such an embodiment is not preferred especially where the barcode structures are carried on consumer products , in view of the significant processing burden that would be placed on the brand owner's server 21 to manage the details of all the different users. Further, instead of the barcodes containing the information defining the number of similar products to be scanned and identifying the brand owner's website, this information may be pre-programmed in the brand application module 45 or in the brand owner's server 21.

In the above embodiments, the barcode structure carried two superimposed barcodes on two separate layers. As those skilled in the art will appreciate, it is not essential that the barcodes have to be superimposed on top of each other. The barcodes could be arranged side by side either on two layers or on a single layer of the code structure. In such a case, the code readers would have to be arranged to be able to detect the separated codes . This may be achieved by arranging the code readers also in a side by side arrangement. However, such an embodiment is not preferred because of the added complexity. It is therefore preferred that where two or more barcodes are provided, they at least partly overlap each other so that they can be read at the same time by the code readers .

In the first embodiment described above, the barcode structure included a capacitive barcode and an optical barcode. Preferably, the two barcodes are formed on the barcode structure using an appropriate printing technique. For example, the optical barcode 7-1 can be printed on the label using conventional printing ink or toner. Similarly, the capacitive barcode 7-2 can be formed by printing conductive ink or toner onto the substrate 7-4. In such an embodiment, the substrate 7-4 and the label 7-3 are preferably formed from paper or other cellulosic material. As those skilled in the art will appreciate, various different printing techniques can be used such as inkjet printing, laser printing, gravure printing, flexography, screen-printing, etc.

In the above embodiments, the code readers 9 were mounted within a user's mobile telephone 11. As those skilled in the art will appreciate, the above described systems can be used where the code readers are mounted in any appropriate computer device, such as a personal computer, a personal digital assistant or in a dedicated hand-held code reader. In the latter case, if the code reader does not have the ability to communicate with a remote Internet server, it may be connected to an appropriate communication device such as a mobile telephone through an appropriate wire or wireless connection.

In the above embodiment, the user's mobile telephone included various software modules. As those skilled in the art will appreciate, these software modules may be pre- installed in the mobile telephone before being sold to the user. Alternatively, these software modules may be downloaded on a carrier signal from the network. Alternatively, the software may be provided on an appropriate computer readable medium, such as a CD-ROM or the like. In such a case, the software can be loaded into a computer device and then downloaded into the user's mobile telephone through an appropriate interface. The software modules may be provided in any appropriate computer language and in any format such as in compiled or decompiled form. In an alternative embodiment, the functionality of the software modules may be provided by dedicated hardware circuits.

In the first embodiment described above, the same barcode was provided on the same type of product . In order to determine that the same barcode structure was read in the first and second readings, the code reader determined the registration between the two barcodes from the two readings and compared the results. In an alternative embodiment, one or both of the barcodes may be unique to each product, thereby allowing the reader to be able to confirm that it is the same barcode structure that is read in the two readings, without having to determine the registration of the two barcodes. Alternatively still, both barcodes (or only the bottom barcode) for each product may be randomly chosen from a large number of different barcodes. With such an arrangement there will only be a small chance that two products that are sold next to each other (or by the same retail outlet) will have the same two barcodes. Therefore, the readers can be programmed to assume that the combination of the two barcodes for each product will be unique and, therefore, there is no need to determine the registration between the two barcodes. Further, in these alternative embodiments, the barcode provided under the removable label does not have to be read by the code reader in the first reading. Instead, the barcode structure can be arranged so that the user reads the first barcode in the first scan, removes the label and then reads the second barcode in the second scan.

Claims

CLAIMS :

1. A system comprising: a code structure carrying a machine readable code ; and a code reader operable to read the machine readable code carried by said code structure; wherein the code structure includes means, actuable by a user, for altering the machine readable code so that said code reader is unable to read the machine readable code or is able to detect that the machine readable code has been altered.

2. A system according to claim 1, wherein said machine readable code is printed on said code structure.

3. A system according to claim 1 or 2 , wherein said altering means comprises a user removable portion of the code structure.

4. A system according to claim 3, wherein said machine readable code is formed from a material whose properties change when said user removable portion is removed, thereby altering the machine readable code.

5. A system according to claim 4, wherein said material is visible to the human eye, wherein said code reader is operable to read said machine readable code by optically detecting the material and wherein the material is operable to react with the atmosphere or light when said portion is removed, to become transparent so that said code reader is unable to read the machine readable code .

6. A system according to claim 3, wherein said code structure carries first and second machine readable codes, the first machine readable code being carried by a substrate of said code structure that is provided under said user removable portion and the second machine readable code being carried at least partly by said user removable portion.

7. A system according to claim 6, wherein said first and second machine readable codes have different physical characteristics and wherein said code reader includes a first detector operable to detect the physical characteristics of the first code and a second detector operable to detect the physical characteristics of the second code.

8. A system according to claim 7, wherein said code structure and said code reader are arranged so that said code reader is able to read the first and second codes at the same time whilst said user removable portion is attached to the code structure.

9. The system of claim 8, wherein said code reader is operable: (i) to receive signals from said first and second detectors from two separate readings of the code structure; and (ii) to compare the detector signals obtained from the two readings to determine if said user removable portion has been removed between the first and second readings.

10. A system according to claim 9, wherein said code reader is operable to accept the reading of the code structure as a valid reading if the code reader determines that the user removable portion has been removed between the first and second readings and is operable to reject the reading of the code structure as an invalid reading if the code reader determines that the user removable portion has not been removed between the first and second readings.

11. A system according to claim 9 or 10, wherein said code reader is operable to compare the detector signals obtained from the first and second readings to determine if it is the same code structure that is read in the first and second readings.

12. A system according to claim 11, wherein said code reader is operable to determine a first registration between the first and second machine readable codes obtained from the first reading and to determine a second registration between the first and second machine readable codes obtained from the second reading and is operable to determine if it is the same code structure that is being read in the first and second readings by comparing said first and second registrations .

13. A system according to any of claims 9 to 12, wherein said code reader includes a timer operable to define a period of time in which the second reading is to be completed after the first reading and wherein the code reader is operable to reject a reading as being an invalid reading if the second reading is performed after said period of time has elapsed.

14. A system according to any of claims 9 to 13, wherein said code reader is operable to process the signals obtained from said first reading to determine whether or not said user removable portion has been previously removed and replaced prior to said first reading .

15. A system according to claim 14, wherein said code reader is operable to determine whether or not the user removable portion has been replaced from a variation in the signal levels obtained from at least one of said detectors during the first reading.

16. A system according to any of claims 7 to 15, wherein said first machine readable code is formed from a geometrical array of conductive code elements and wherein said second machine readable code is formed from a geometrical array of optically detectable code elements, wherein said first detector of said code reader comprises a capacitive code reader that is operable to detect the conductive code elements of said first machine readable code and wherein said second detector comprises an optical code reader that is operable to detect the optical characteristics of said second machine readable code.

17. A system according to any of claims 7 to 15, wherein said first machine readable code is formed from a material that is operable to reflect light of a first wavelength, wherein said first detector is operable to detect light of said first wavelength, wherein said second machine readable code is formed of a material which is operable to reflect light of a second wavelength different from said first wavelength and wherein said second detector is operable to detect light of said second wavelength.

18. A system according to claim 17, wherein one of said wavelengths lies within the infrared region of the electromagnetic spectrum and wherein the other wavelength lies within the visible region of the electromagnetic spectrum.

19. A system according to any of claims 7 to 18, wherein said user removable portion comprises an adhesive label.

20. A system according to claim 19, wherein said adhesive label comprises at least one cut-out portion carrying a portion of said second machine readable code and wherein said label is arranged so that when removed by said user, said at least one cut-out portion remains attached to a substrate of said code structure.

21. A system according to any of claims 7 to 20, wherein said first and second machine readable codes are superimposed on top of each other.

22. A system according to any preceding claim, wherein said code structure comprises a cellulosic substrate which carries said machine readable code.

23. A system according to any preceding claim, wherein said machine readable code comprises a geometrical array of code elements that defines encoded data and wherein said code reader is operable to detect the position of the code elements within the array to recover the encoded data.

24. A system according to claim 23, wherein said machine readable code comprises a one dimensional or a two dimensional barcode.

25. A system according to claim 23 or 24, wherein said encoded data includes data identifying a number of similar code structures to be read, wherein said code reader is operable to monitor the number of similar code structures that are read and is operable to perform an action when it determines that the identified number of similar code structures have been read.

26. A system according to any preceding claim, further comprising means for transmitting data identifying a valid reading of the machine readable code from said code structure, to a remote computer server and means for receiving a reward from the remote computer server.

27. A system according to claim 26, wherein said reward comprises content data and wherein the system further comprises means for outputting the received content data to a user.

28. A system according to any preceding claim, wherein said code reader forms part of a user computer device .

29. A system according to claim 28, wherein said code reader forms part of a mobile telephone.

30. A code structure for use in the system of any- preceding claim, comprising: a substrate carrying a machine readable code; and means, actuable by a user, for altering the machine readable code to prevent the machine readable code from being read by a code reader or to allow a code reader to detect that the machine readable code has been altered.

31. A structure according to claim 30, wherein said machine readable code is printed on a substrate of said code structure .

32. A structure according to claim 30 or 31, wherein said altering means comprises a user removable portion of the code structure .

33. A structure according to claim 32, wherein said machine readable code is formed from a material whose properties change when said user removable portion is removed, thereby altering the machine readable code.

34. A structure according to claim 33, wherein said material is visible to the human eye, wherein said code reader is operable to read said machine readable code by optically detecting the material and wherein the material is operable to react with the atmosphere or light when said portion is removed, to become transparent so that said code reader is unable to read the machine readable code .

35. A structure according to claim 32, which carries first and second machine readable codes, the first machine readable code being carried by a substrate of said code structure that is provided under said user removable portion and the second machine readable code being carried at least partly by said user removable portion.

36. A structure according to claim 35, wherein said first and second machine readable codes have different physical characteristics so that they can be detected by separate code detectors.

37. A structure according to claim 35 or 36, wherein said first machine readable code is formed from a geometrical array of conductive code elements and wherein said second machine readable code is formed from a geometrical array of optically detectable code elements .

38. A structure according to claim 35 or 36, wherein said first machine readable code is formed from a material that is operable to reflect light of a first wavelength and wherein said second machine readable code is formed of a material which is operable to reflect light of a second wavelength different from said first wavelength.

39. A structure according to claim 38, wherein one of said wavelengths lies within the infrared region of the electromagnetic spectrum and wherein the other wavelength lies within the visible region of the electromagnetic spectrum.

40. A structure according to any of claims 35 to 39, wherein said user removable portion comprises an adhesive label.

41. A structure according to claim 40, wherein said adhesive label comprises at least one cut-out portion carrying a portion of said second machine readable code and wherein said label is arranged so that when removed by said user, said at least one cut-out portion remains attached to the substrate of said code structure.

42. A structure according to any of claims 35 to 41, wherein said first and second machine readable codes are superimposed on top of each other.

43. A structure according to any of claims 30 to 42, comprising a cellulosic substrate which carries said machine readable code .

44. A structure according to any of claims 30 to 43, wherein said machine readable code comprises a geometrical array of code elements that defines encoded data.

45. A structure according to claim 44, wherein said machine readable code comprises a one dimensional or a two dimensional barcode.

46. A code reader for use in the system of any of claims 1 to 29, comprising: first and second detectors operable to detect the physical characteristics of first and second machine readable codes carried by the code structure; and wherein said code reader is operable: (i) to receive signals from said detectors from two separate readings of said machine readable codes; and (ii) to compare the signals obtained from the two readings to determine if the code structure carrying the first and second machine readable codes has been altered.

47. A code reader according to claim 46, operable to read the first and second codes at the same time whilst said user removable portion is attached to the code structure.

48. A code reader according to claim 46 or 47, operable to accept the reading of the code structure as a valid reading if the code reader determines that the user removable portion has been removed between the first and second readings and operable to reject the reading of the code structure as an invalid reading if the code reader determines that the user removable portion has not been removed between the first and second readings.

49. A code reader according to any of claims 46 to 48, operable to compare the detector signals obtained from the first and second readings to determine if it is the same code structure that is read in the first and second readings .

50. A code reader according to claim 49, operable to determine a first registration between the first and second machine readable codes obtained from the first reading and to determine a second registration between the first and second machine readable codes obtained from the second reading and operable to determine if it is the same code structure that is being read in the first and second readings by comparing said first and second registrations .

51. A code reader according to any of claims 46 to

50, comprising a timer operable to define a period of time in which the second reading is to be completed after the first reading and wherein the code reader is operable to reject a reading as being an invalid reading if the second reading is performed after said period of time has elapsed.

52. A code reader according to any of claims 46 to

51, operable to process the signals obtained from said first reading to determine whether or not said user removable portion has been previously removed and replaced prior to said first reading.

53. A code reader according to claim 52, operable to determine whether or not the user removable portion has been replaced from a variation in the signal levels obtained from at least one of said detectors during the first reading.

54. A code reader according to any of claims 46 to 53, wherein said first detector of said code reader comprises a capacitive code reader that is operable to detect conductive code elements of a machine readable code and wherein said second detector comprises an optical code reader that is operable to detect optical characteristics of a machine readable code.

55. A code reader according to any of claims 46 to 53, wherein said first detector is operable to detect light of a first wavelength and wherein said second detector is operable to detect light of a second wavelength.

56. A code reader according to claim 55, wherein said one of said detectors is operable to detect light which lies within the infrared region of the electromagnetic spectrum and wherein the other one of said detectors is operable to detect light which lies within the visible region of the electromagnetic spectrum .

57. A code reader according to any of claims 46 to 56, wherein said machine readable code comprises a geometrical array of code elements that defines encoded data and wherein said code reader is operable to detect the position of the code elements within the array to recover the encoded data.

58. A code reader according to any of claims 46 to 57, operable to monitor the number of similar code structures that are read and operable to perform an action when it determines that a predetermined number of similar code structures have been read.

59. A code reader according to any of claims 46 to 58, further comprising means for transmitting data identifying a valid reading of the machine readable code from said code structure, to a remote computer server and means for receiving a reward from the remote computer server.

60. A code reader according to claim 59, wherein said reward comprises content data and wherein the code reader further comprises means for outputting the received content data to a user.

61. A code reader according to any preceding claim, which forms part of a user computer device .

62. A code reader according to claim 61, which forms part of a mobile telephone.

63. A computer instructions product comprising computer implementable instruction for causing a programmable computer device to become configured as a code reader comprising: means for receiving signals from first and second detectors operable to detect the physical characteristics of first and second machine readable codes carried by a code structure; and means operable (i) to receive signals from said detectors from two separate readings of said machine readable codes,- and (ii) to compare the signals obtained from the two readings to determine if the code structure carrying the first and second machine readable codes has been altered.

64. A method of reading a machine readable code comprising the steps of: providing a code structure carrying a machine readable code, the code structure including means, actuable by a user, for altering the machine readable code so that said code reader is unable to read the machine readable code ; using a code reader to read the machine readable code carried by said code structure; and altering the machine readable code so that said code reader is unable to read the machine readable code or is able to detect that the machine readable code has been altered.

65. A method of reading a machine readable code comprising the steps of: providing a code structure carrying first and second machine readable codes, the first machine readable code being provided on a substrate of said code structure and at least part of the second machine readable code being provided on a removable portion of said code structure; using a code reader to perform a first reading of the machine readable codes carried by said code structure; using the code reader to perform a second reading of the machine readable codes carried by said code structure; processing signals obtained from said first and second readings to determine if said removable portion has been removed between said first and second readings ; accepting the reading of the code structure if said processing step determines that said removable portion has been removed between said first and second readings ; and rejecting the reading of the code structure if said processing step determines that said removable portion has not been removed between said first and second readings .

66. A method of reading a machine readable code comprising the steps of: providing a code structure carrying a machine readable code, the code structure including a removable portion which covers said machine readable code, the machine readable code being formed from a material which reacts with the atmosphere or light so that it becomes unreadable by a code reader a predetermined period of time after said removable portion has been removed; causing a user to remove said removable portion; and using a code reader to read the machine readable code carried by said code structure after said portion has been removed and before said predetermined period of time has elapsed.

67. A brand loyalty method, comprising: associating a code structure carrying a machine readable code with a product or service provided by a brand owner; using a code reader to read the machine readable code carried by said code structure,- wherein the code structure and the code reader are arranged so that the step of reading the code structure renders at least part of the machine readable code inoperative, so that further readings of the machine readable code can not be made; and providing a reward to a user from the brand owner in response to the reading of the machine readable code.

68. A code reader for reading machine readable codes, the code reader comprising: a first detector operable to detect optical codes ; a second detector operable to detect conductive codes ; and a housing carrying the first and second detectors; wherein said housing includes an aperture through which light can pass and wherein said first detector is positioned within said housing to receive light which passes through said aperture; and wherein said second detector includes an electrode mounted on said housing and surrounding said aperture.

69. A capacitive code reader for reading conductive machine readable codes, the code reader comprising: a first electrode; a plurality of second electrodes disposed to surround said first electrode; and excitation and sensing circuitry coupled to said electrodes and operable to generate and to apply an excitation signal to one or more of said electrodes and to receive and process a signal obtained from one or more of said electrodes to read said machine readable code .

70. A method of manufacturing a code structure comprising: forming a first machine readable code on a first layer of the code structure; forming a second machine readable code on a second layer of the code structure; and attaching the second layer to the first layer in such a manner that a user can remove at least part of said second layer from the code structure .