GB2548896A - Dual machine-readable codes with reactive properties - Google Patents

Abstract

A technique for indicating a state of environmental exposure of an article (e.g. a food item) by use of an active substance (such as an ink) which changes appearance with environmental exposure. Dual codes, such as QR codes, are prepared to represent the before- and after-exposure states. Error correction and/or positional information employed in the codes is selectively undermined by altering each code based on whether it is intended to represent the state of the article before or after exposure. Before exposure the undermined code (qr_ad, Fig. 5) fails to read, while the other code (qr_ue, Fig. 5) reads correctly, As a result of exposure to, for example, heat or light, the chemical and colour changes in the ink used to print the codes cause the previously unreadable to become readable, while the other code is now unreadable. In this way, scanning the codes before and after the environmental exposure produces two different messages. The process could function by undermining the error correction in the two distinct codes.

Description

Dus! Machifis-Rsadabls Codes wllh §^eactlve Propariias OCOOOOOOUUUUOOUUUUUUUUUUUUUUUUUUUUUUUUUUUU^JMMMMJUUUUUUUUUUUUUUUUUUUUWJUUUUUUUUUUUUWllWWWW^^MMMMMMMMMMMMMMMMM^Mh^MMMM^Wf·······

Fiaid of the jovenlion

The present invention relates to a technique for indicating a state of environo'ientet exposure of a thing (such as an article) by use of machine-readable codes (e.g. QR codes) uair'ig an “aotive" substance which changes appearance with environmentai exposure.

Background of thg; invention ft/lany kinds of machine-readable codes are known including one-dimensional (1~D) codes including bar codes of various types, and two-dimensional (2-D) codes such as QR codes, Data Matrix and PDF 417,

Figure 1 illustrates these typ®s of code, Fig. 1(a) showing a UPC-A type bar code, Figure 1(b) a QR code, Fig. 1(c) a Data Matrix code and Fig. 1(d) a PDF 417 coda.

The name of tire code type generally indicates a technical standard on which the codes are based and in accordance with whicti the codes are prepared. The technical standard may set rules on the proportions and configuration of the code and on the error-correctiors tecfirsigues if any to be used. 1-D codes generaiiy efnpioy only a simple checksum but in principle more sophisticated error correction techniques are available, particularly but not necessarily exclusively in the case of 2-D codes as explained below. in each case, typical uses of sucti codes Include product marking, tracking of packages, provision of product or serving support, document marmgemeni, ticketing, advertising and couponing. 2-D codes are becoming ificreasingly popular since they can store much more data than a bar code. Whilst a bar code can usually store only one alphanumeric string such as a product number, 2-D codes can be used to store a wide range of data Including alphanumeric strings, Japanese or Chinese characters, control codes and internet URLs.

Recently, QR codes in particular have become popular as a method of Increasing consumer inteiBction with products. With the availablNty of scanning apps or5 smartphones, customers cart read a QR code on a product and obtain some useful information such as a contact address or telephone number. The technique of “hardiiitking" has become especially popular, where the OR code is used to store a URL on die V¥orld Wide Web which, when decoded by e smartphoneo scanner app, brings up Ilia corresponding Web page auiornaticaliy on the smartphone screen. As wiiS be understood by those skilled in the art, a URL cen be stored as part of a QR code in the form of text, in ecco.*’dence with the RFC 39S6 standard.

An article to which a macidne-readabla code is attached Iri some way {for example by priritiiiQ on the article itself, by printing on a label attached to the article, or by printing on packaging thereof) can be said ίο be lagged" with that maohlrie-readabie code. Since an eiobodiment of the invention will be described later with respect to QR codes, some background on this type of code will now be given. in contrast to barcodes, which ere scanned in one dimension by a narrow beam of light, a QR code is first captumd by a 2-d:mansionai digital iniage sensor {such as a smartpfmne canHua chip) and then digitally analysed (scanned, decoded) by a processor running a suitable program (such as a smartphone app). Such an arrangement is referred to below as a “scanner' even though the scanning occurs In software.

Figure 2 shows the main parts of a QR code 10. Figure 2 shows the QR code 10 as a black and white code, and the terms “biedi” and “white” will be used henceforth for convenience to denote bvo states capable of being distinguished by a scanner, it will be understood, however, that it is rmt necessary always for QR codes to be black and white. For scanning purposes, it is generally sufficient If light and dark patterns are present, which may be coloured under certain circumstances.

As can be seen, the QR code 10 has an ovaraii shape of a square, end is built up of smaller square patterns of various kinds. Finder patterns 12 In the fone of concentric square patterns, are located In itvee of the four corners of the QR code 10 as shown in Rg, 2, The processor locates these dnder patterns, and uses Alignment patterns 14 (smaller squares Ιίί Fig, 2) to determine the size and orieritation of the OR code. In this way, the QR code can be read In any direction arid at high speed.

The smallest squares 18 are called "Cells" and contain the Inforniation content of the QR code (In a convoluted way as explained belovr). Timing patterns 16 are dotted lines which, conriect the Finder patterns 12 and help the scanner to detect the poaitiors of each Ceil. Specitic patterns (not stiown) iirdicate the type of data being encoded (such as alpharrumerlc), ttie level of error correction applied (see below) and the mask pattern used (see below). Fineliy, a Quiet zone 20 around the QR code 10 provirjes a miargin to avoid confusion with any other printed symbois or iniages which may be nearby, for example as part of product packaging on Vtihich the QR cede 10 is placed.

The cells 18 are either iigtit or dark, denoting bits of value binary "0" or "Γ respectively, and constitute a data area or data pari of the QR code. However, the cells do not directly represent useful data. Rather, they are encoded using an error-correction algorithm using Reed-SolrjiTicn Ceding, allowing the QR code 10 to be reed even If rt is partially dirty or damaged as illustrated in Figure 3. Different levels of error correction capability are available, depending on ihe use case (such as a dirty factory, where a higher error correction level would be appropriate).

For example, if there are e hundred codewords of QR Code to be encoded, fifty of which need to be corrected, one hundred codewords of Reed-Soiomon Code are required, because Reed~Sr>lomon Code requires twice the amount of codewords to be conected, in this case, there are two hundred codewords in ic-tal, of whlcti fifty can be corrected giving an error correction rate of 25%. 'i'he QR code 10 Indicates the error correction level In use uslr^g a special pattern (not shown in Fig, 2) located next to one of the Finder patterns 12.

In larger QR codes, the message Is broken up into several Reed-Solomon code blocks. The block size is chosen so that at most fifteen errors can be corrected in each block; this limits the complexity οΓ tho decoding algorithm. The code blocks era the:'; ifiterleaved together, making it less likely that localised damage to a QR code will overwhelm the capacity of any single block. A further level of complexity Is provided by masking, Masking Inverts certain cells 1:-= the data part (turning white to black and black ίο white) whilst leaving the other ceils urici iersged. The effect Is to break up patterns In the data area that might confuse a scanner, snch as large blank areas or misleading features that look ilka the Finder patterns 12. The mask patterns are defined on a grid that is repeated as necessary to cover the cells 18 in the data part of the QR code 10. Cells corresponding to the dark areas of the mask are Inverted, Various mask patterns are available: the encoder selects the one that works best (mlnimi;<res undesirable features in the end result), end the selected mask is Indicated by another special pattern (also not shown in Fig, 2) next to that for the erior correction level.

Figure 4 shows ar; example in w.nich a mask pattern consisting of diagonal lines of black cells has been epplied. This pattern has to be subtracted from the as-scanned symbol In order to recover the un-masked code, which is done using an ExdusIve-OR operation. Error correction processing can then be applied to recover the original data.

So-called “active” Inks, which change their properties under some kind of environmental exposure are known, and these can be applied to an article to provide a Visual indication that the article has been affected by some environmental action. For example this principle can be used to indicate to a consumer whether a food article Is still fresh or safe to eat or wfiether conveieely it Is unsafe due to. for example, a prolonged exposure to room temperature.

As one example, the II 21000 thermochromlc ink available from LCR Hallcrest Ins. is a water-based thermochromlc Rexo ink suitable for printing on paper or board. The ink is fully coloured at 3°C below an activation temperature and coiourless above the acllvatioii temperature. Various activation temperatures are available including 15, 31 and 47“C. ϋίΐϋί recenUy, however, it has not been proposed to apply such active inks to machine' readable codes. Doing so would enable information about the environmental exposure of the afnxed article lo be determined by a scanning and iherealter disseminated more widely, lor example to the Internet, This rxincept has potential to extend the tntencet of Things (loT) more widely to everyday objects.

Summary of the Invention

According to s first aspect of the present invention, tfiere is provided a method of Indicating a change of state of an article due to environmentat exposure by use of a pair of machine-readable codes, the method comprlsirio forming first and secofid codes for use on the article, the forming selectively employing ars active substance wtsch ctianges appearance urider the environmental exposure such that wlrether the first and second codas are capeble of being niachine read changes iridependently for each code.

The machine readable codes are associated in sonie way with the thing whose state of envlronmentai exposure is to be indicated. For example where ihe thing is an article they may be printed on the article Itself, on a label attached to the article, or on packaging of the article.

Preferably the codes are arranged so that: the first code Is readable prior to the environmental expos;.fre but Is unreadshte after the environmental exposure: and the second code Is not readable before environmental exposure but is readable after the environmental e.xposijre.

Iri one embodiment the active substance comprises ar; active Ink and the forming is performed by printing. In this case, preferably, the printing comprises first printing tt?e codes with a non-active ink followed by second printing with the active ink to overprint selected parts of the code. \ΐ\ any method as defined above, each code may comprise a data part and a non-data part. The fomting by the active substance tf^en occurs in seiect.ed portioris of eaoi^ code to modify at least one of the data pad and the non-data pad.

As one possibility, the active substance is formed In the data part of ead'! code, to corrupt or repair an error correction coding applied to the data part. Alternatively or in addition, the active substarrce is formed in the norr-data part to corrupt or repair positional information in the non-data pad.

Preferably also, forming (e.g. printing) the active substarsce has no effect on the first code prior to tire environmental exposure and corrupting the first code foilovifing the environmental exposure (due to the resulting change irr the active substance), whilst the same active substance has no effect on the second code prior to the envirofimsntal exposure and corrupts the second code after the environmental exposure.

The environmental exposure can Include exposure to one or more of, high temporaturo low temperature visible light UV light water or moisture gas or volatile ctienscai toxifi bactene virus the elapse of tirree. in embodiments of the present invefilion tt?e machlrie-readable codes are read by optical scanning. Thus, in any method as defined above, the active substance may be one of a substance which darkens under fie environmental exposure; and a substance which lightens ursder the eirvironmental exposure.

The active substance is at least one of: an ink {whidi includes ariy kind of dye, pigment, paint etc. capable of being printed):

a fibre or thread capable of being woven, knitted, embroidered or the like into fabric; arvJ a material such as an environmentaliy-active plastic material suitable for applying to a surface by inlaying, moulding or the like .

The active substance referred to above can include any of; an active ink; a fibre; an iniaid matesiai, in each case the active substance is formed so as to coristruct madiine-readabie codes along with a basic, non-active substance, in the preferred embodiment both substances are inks with the active ink printed over the basic ink, but in general neither I'las to be an ink, and the active substance need not necessarily be formed over the basic substance. The oon-active substance ntay be a different type of substance from the active substance. Thus, for exampie an active ink could be printed over a basic substance in the form of an iniaid plastic material

An embodiment of the present invention employs QR codes based on the weli- known QR staridard, such that each machine readable code comprises a QR code.

Acrording to a second aspect of the preserst invention, there is provided an article having applied to It First and second codes prepared in accordance with any method as defir^ed above, the codes indicating a stale of environmental exposure of Ifie artide.

According to a third aspect of the present invention, there is provided an article to which is applied first and second machine-readable codes which are formed by selectively applying an actlw substance which changes appearance under environmental exposure, such that whsifier the first anct second codes are capable of being machine read changes Independently for each code.

In the above article, preferably, the first code Is readable prior to the snvirortmental exposure but is unreadable after the environmental exposure, and the second code is not readable before the environmental exposure but is readable after the erivironmenfel exposure.

In an embodlraent of the present Ir-vefvlion, certain steps of the above method are performed with the assistance of a suitably -programmed processor. Thus, according to a fourth aspect of the present invention, there Is provided corripuler program code for use In preparation of first and second madiine-readablo codes formed using an active substance, the code when executed by a cortipuler performing operations of: (i) on the basis of a desired message for each of the first and second codas preparing enabled and un~actlvaied (gr__ue) and enabled and activated (gr_ae) versions of the codes; (II) using duplicates of die versions prepared in (i), creating disabled versions of each code (qr_ud, qr„ad) in vtihlch selected portions are reversed In their visual appearance; and create templates (qr_um, qr_am) including the portions selected in (li), to be formed using the active substance.

The above computer program code may be stored on a data storage device.

As already mentioned, an embodimerit of the present irivenlion uses active ink as the active substance. Thus, in this embodiment of toe present invention a pair of codes, printed with, riormal ink - that is, non-active ink vtoich does not change deteotably with environmentsi exposure - and active ink, are printed to represent a potentlai change of state of an article with which the codes are associated, based on chemical changes in the active ink used for the selective part of the printing. Each code contains a desired message such as “kept cool” or “not kept cool”, “unexposed” or "exposed”, "unsteriiixed” and “sterilized”, and so forth.

The proposed method uniquely undermines the error correction in two distinct tags to aliov,/ only one type of ink to be used to accomplish the seme effect as one tag using multipie inks. The Reed-Sclomon error correction conventionally applied is undermined by altering each tag based on whether it is intended to represent the before or after activation state of the active ink as a result of environmental conditions. The maif> effect is that snitiaHy (before the environmental exposure) the undermined coda of one tag fails to read* ν</ηΠθ the other reads correctly. The effect is reversed as a result of the chemical (and therefore colour) changes In the active Ink resulting from the environmental exposure. \n this way different messages appropriate to the state of the article can be conveyed by scanrang Itie tags belore and after the environmental exposure.

By use of the present invention, It Is possible to signifissntiy simplify and reduce tlte cost of printing these active tags, Sy being able to use only one active Ink, the chemisiry is significanliy simplified. Tt?e reason for this Is as follows; usirsg two active Inks makes the recoding of the tags simple, since zero and one bits can both be changed If two Inks are used. Hoviever, designlr?g both ‘Irndslble' arid ’disappearing' inks that change under exactly the same envirorirneiital conditions is both difficult and expensive,

Features in embodiments Include the following; A systerri with ntultlple tags tftat cftatige independerrtly based on the same kind of ohernicai arid colour change,

Ttie change in each tag eriables Ofre and disables the ottier (es opposed to other changes)

The use of this technique In any kind of visually presented error corrected code, .Application to a wide range of active substances, not confined to inks.

Application to things other than articles which convenlionaily bear QR codes, including living things.

Detection of a wide range of types of environmental exposure including not only heat, light etc. but also specific toxins, bacterie or viruses.

Use of rtiore than one colour or colours other than black and white.

The possibility to daioage the QR code In Its basic template (e.g. Finder patterns) rather than the data part.

Brief Description of the. Drawings

Reference is made, by way of exarapio only, to the accompanying drawings in which; Figures 1(a) to (d) iHustrate sonie known types of machine-readable codes;

Figure 2 shows some important alemonta of a QR code;

Figure 3 shows s dldy or darnaged QR code;

Figure 4 shows the principle of masking as applied to QR codes;

Figure 5 shows the principle of the inveritiof) applied to dual QR codes; and Figure 6 is a flowchart of steps employed in ari embodiment of the present Invention, Detailed DevScrIptlon

An embodiment of the present invefUiofi will now be described referring to an "active ink” (l.e, an Irik whict? reacts to some environmental exposure of interest) as an example of on active substance.

In the context of the Irdernet of Things, developments In active Inks allow machine-readable codes sucti as QR codas to act as sensors operating at the very edge of the network. These chemically active Inks change based on changes in the environment. By designing codes that can change their state as a result, a type of very simple (cheap) sensor can be created. The state of the sensor can then be 'croe/d-read’ by conventional personal devices, rather than relying on expensive devices such as RFID readers. Provisioning the hmits of the Intomei of Things with very cheap sensors that can be read by ubiquitous devices opens up a wealth οΓ new oppr.rftur?:ties.

One conceivabie approach would be to sintpiy trave two versions of Ute code, orte for the un-activated state and on tor the activated state, artd print them using three different inks: one that doesn’t change, one that turns from black to white and one that changes from 'white to btaok. This three ink approach, however, would require the development of two different chemical processes that change in different ways under exactly the same target environmental condlliorrs. This would be a significant challenge giverr that there are a nunrber of differer^t environmental conditions that can be considered, each of 'which need significant development for each t'wo ink colour change design. Here Is a partial list of the Ink types under corrslderation.

Active Ink Environmental action

Therntoohrornic reversible temperature

Thermochromic irreversible temperature

Photochromic reversible visible ligftt

Photochromic Irreversible visible light UV Florescent reversible UV light

Phospliorescent irreversible vis«bte/UV light

Hydro chromic re'>rersihie ‘water/molsture

Hydro chromic irreversible 'water/molsture

Touch seftsitive temperature and rnoisture

Sterilization irravemible temperature (at least 1Q0°C)

Oxygen irreversible air or oxygen C02 irreversible air or C02

Volatile chemicals Irreversible 'volatile chemical

Timedemperature irreversible time and temperature

Radiosensitive radiation

Toxin-sensitive toxins

Bacterlaliy-sensstive bacteria

VifuS'SensIlive viruses

Time elapse irreversible time k wiH be noted that time is a special case. The other types οΓ envlfonmefttai action wiN involve the elapse ol a stiorter or longer period of time together with erivironmental actloii oorscerned, in the finai case, elapse ol time alone is suffsciant.

Thus, it would be desirable to echleve the same effect vyith only one active Ink (that is, using a conkiination of one active inK with a basic, non-active Ink which Is essentially stable under the environrfientai exposure o? interest).

An embodiment of the present invention v/hich lulhls this aim will now be described by referring to QR codes by way of example.

Dual codes (also called tags herein) are prepared to represent a potential change based on cherrhcal dranges In the Ink used for printing the codes. The Invention undermines tfie Reed-Solomon error correction erriployed in OR by altering each code based on whether it Is Intended to represent the before or after activation of the chemioei ink as a fesuit of envlronrnentai conditions. The nrain effect is that the undermined message of rirre cr,)de fails to read, while ti-ie other reads correctly. The effect is opposite between the two codes as a result of the chemical (end tiierefore colour) changes In the ink used to print the codes.

Before descrlblirg the err.bodlment, it may be helpful to define some terms as follows. Tag (or Code)

An area on an article, on a label on the article, or on Its packaging 'which is printed with et ieest one ink (see below) to visually represent madrine-readable code. Not all embodiments of the present invention require use of tags, but the term is used below for convenience.

Active Ink

Inks, used in printing codes, ttiai react (change colour) based on environmental conditions, e,g, heat, humidity, light, haserdous chemicals, etc, InciderHaliy, the term “ink" is used for convenience and indudes any Kind of dye, coadng or pigment capable of being printed. Different inks may be used depending on the type and/or degree of environmental exposure to be detected. As already mentioned, the present invention is not confined to the use of active inks: other types of active substance are possible,

Non-Aclive (or Basic) Ink inks which are stabis (as far as possibie) under environmental conditions such that they do not become appreciably lighter or darker under the action of heat, humidity, light, hazardous chemicals, etc, invisible ink A kind of active ink wfeich is not easily visible prior to the envlronmenia! exposure (in other words, which when printed iniiialiy looks white to the scanner) but which darkens or deepens in coiour under environmental action.

Disappearing Ink A kind of active ink which is dark as printed prior to the environmental exposure (in other words, which looks black initially) but which lightens or even vanishes under envirornnervtai action to form a transparent/white area.

Active Tag A tag which la printed at least partly using an Active ink, such toat it reacts to its envi.'onnient by changing Its visual appearance and therefore its readable content. ktachine-Reedable Code A code whidi in principle is readable by a machine (usually but not necessarily exclusively optically readable), "in principle" refers to the fact that in accordance with the present invention a given teg may be modified (corrupted) such that either prior to or following environmental exposure it is not in fad readable. yachlns-readable Code Standard A specification of a machine'-readabie code, such as QR (Quick Response), Data Matrix. PDF 417, etc. QR Code A machine-readable cede produced in accordance witfi the QR standard for digital encoding of data u.sing printed media and intended for scanning by camera enabled devices (e.g. ftiobile phones), as employed In the embodiment to be described.

Data Part A part of a QR code which encodes useful data.

Nofi-data part

Af^y part of a OR code which does not encode data but rather is used for location, etc. Undermined 'Undermined' means that a number of bits have been changed in the encoded data (represented as black or white squares irt the printed QR Code), and/or that positional Information (such as Finder patterns in QR) are missing or obscured.

Readabie/Unreadable ‘Readable" denotes a tag which is capable of being scanned and decoded by a regular scanrser (In ether words a scanner compliant with the mactvne-readabie code standard In use). As noted earlier, QR codes are generally captured In their entirety end scanned arsd decoded in soibware, Unreadabie mearts a tag which cannot be scanned and decoded using a regular scanner, either because the data part or the non-data pari is damaged, it shouid be rmted that both scanning and decoding are r?eeded to recover deia from a lag, if the lag cannot be scanned (e,g. because the scanner cannot find posiiionai niarks which it r?eeda) the data part cannot ba read; whilst even if the tag can be scanned, if the data part is so cornjpted that the error correction coding taiia, decoding wiii not succeed.

Enabled 'Enabled' tags are in their normal state and can be reed.

Disabled

Tags that have their error correction and/or positioivsi infonrsation undermined are said to be 'disabled’.

Un-activaled

Tags that have not yet been e.xposed to the environmental conditions that affect a change in the ctiOfriistry of the ink are said to be In an 'Un-activatad’ state,

Activatad

Tags that have been exposed to the targeted environmental conditions are said to be in an ‘Activated' state.

Using some of tiie above terminology, the present invention involves the preparation of dual tags in accordance with a machine'teadabie code standard, but 'which include acti've ink so that as printed, one tag is not readabia (and not necessaril'/ compliant with the standard). An effect ot environmental exposure {also called environmental action) Influences the active ink to change Its colour, so that a tag which was not initially readable becomes readable, and vice-versa. T he procedure to be followed in the embodiment will nov^ be described with reference to Figures 5 and 5, and to the example code below.

Rgure δ shows duai tags before environmenfa! exposiire {left) and after environmental exposure (right). The patterns In the middle represent the squares (sells) that need to be printed using active ink. The arrows labelled "Heat, Light".,represe.nt an environmental action of some kind (of vi^ilch Heat and Light are only examples). Figure 0 is e simple flowchart of steps Invol^^d in producing the dual tags in Figure 5, and has the following steps.

Step S100: First prepare enabled versions un~actlvated (qr_ue) and activated iqrjae) QR Codes, with the desired message in eech case. In the code below 'Un-activoted’ and 'Activated...' are used. These QR codes should be prepared in the conventional manner according to the QR standard, including error correction coding and masking as outlined in the iniroduclion.

Step Si02: Using duplicates of the QR codes prepared in S10D, create disabled versions of each (qr_yd, qr_ad) using the ‘disable’ function.

The disable function either changes certain modules (or ceils) (black or wfilte squares representirtg bits in the message or error correction coding) from black to white or white to black depending on the ' tumOstols” flag (see Python code below), it is highly preferable that these changing bits be eveniy distributed across the message and error correction bits to enable the image processing software in the scanners to process the code.

Step S104: Create templates (qr_um, qr..3m) to inciude only those squares that need to be printed In Invisible ink (qr__um, qrjsm). These tempiates are a kind of mask applied to the codes qr_ue and qr_ad as indicated by the signs In Figure 5. They are referred to here as “teniplates'' to distinguish them from the conventional mask patterns already referred to in the introduction (and that wili continue to be used in accordance with the QR standard).

Step S106: Print the un~activated, enabled QR code (qr..ue) along with the activated, disabled OR code (qr„ad) using a "basic” (non-active) ink. The precise way In which this is done is not Important: however It vsii be convenient to print the QR codes side by side (including one above the other) In the same region of the article to which ttiey are to be affixed, to this way it is poasibia tor a carnet to capture images of both OR codes in one operation.

EspeoiaHy for articles having non-fiat surfaces, it may be preferable to print the OR codes onto a seli-adi^esive label or similar for later application to the article.

As s further step at tftis polrU. it may be desirable to cover the as-printed basic ink with a protective layer such as varnish or ciesr film; this vvili inirrimiso any possible effect of environmental exposure upon the basic ink.

Step S108: Over print pas1s of the QR codes (tags) obtained in S106 using invisible ifik {Itiat ‘vVili appear erhen activated by the environmental conditions). Clearly It Is important here to ensure registratlcn between ttse earlier printing and the over-printing, v.'hich is another reason to print on a label rather than directly onto the article. The active ink is selected to be responsive to an environmental exposure of interest, such as heat, light and so on as outlined In the introduction. Different irsks may need to be used depending on the type and/or degree of environmental exposure to be detected. The purpose of the over-printing is for one tag !e be completed (repaired) by the addition of the active ink, whilst the other is corrupted (damaged) by fhe addition of Ihe active irrk.

Step S110: Scan the codes with a scanner (e.g, smartphone camera plus OR scan software). Since ihe Un-actlvated, enabled OR cods qr. ue is readable and the other QR code qr_ad is not during scannii^g prior to activation by the environment, qr ,ue is the only valid code discovered by the scerxier. Scar?nars should be compliant (i.e. without spedalized extensions) to the QR Code (or other tag standard).

Step SI Expose the tags to the envirofirrieni, as irtoicated by the arrows in Figure 5. This can be as simple as placing a product on a sheif, exposing an article to sunlight, allowing time to elapse, and so forth. The exposure may be intentional or uniriterstlonal; however, it Is to be expected that any given active ink will react only to particular types and degrees of environmental action. As the acsva ink changes with envlronmentai conditions, the template bits change from light to dark and the activated, disabled code qr_ad is repaired.

Step S114: Once the environmental actlors la sufficient (for example, after the tags have been exposed to heat of a sufficient temperature), the activated, disabled code qr_ad beconies the activated, enabled code qr .aa as shov,in In Fig. 5, and can now be read. Cosraspondingly, the υπ-activated, enabled code qr_ue Is damaged by the appearance of additional black squares (1 bits) In Its code, to become lt?e un-acllvated, disabled cade qr_ud which can no longer be read.

The data content will differ between the two codes. For example the activated, enabled code contains a message (or equivalently, a hardlink to a message) to the effect that the product is new, irOsSh, unused, or the like. Tt5e activated, disabled code Includes a message that the article Is old, stale, has been left in the sun, or the like.

From the above, it can be seen that the embodiment provides one readable tag both before and after the environmental exposure. In this way, a user can positively verify whether or not. the article affixed to the tag has been exposed to the environmental action of Interest, by reading the message provided in each case. OR codes are generally created using a software application running or^ a PC or smartphone, and likewise, whilst the above procedure can be performed manually, some of the steps showvs \n Figure 6 are likewise conveniently performed by a processor executing computer program code.

Tine Python code reproduced below by vray of example w?as used to create the Images in Figure 5. The library used for the basic QR code generation is from an open source repository (Python QR). The disable function is of particular relevar?ce to the present invention. In the code below, the term ‘’mask” refers to the templates (qf__um, qr_am) shown in Figure 5, itaport qrcaae fsroa qrcods, image .pure iniport Pyniaginqisjsge def .save png (fnsHie, qr) ; iif.g qr.ifsaiie itsage iiraaga factorywpyiKag.ingliisags;·: f (inaKie, ‘w‘) inig, save (i) f 0 def d.lsis&amp;ie iqs,. : ior Γ.·ο« i;; rijssqdii^r sdSJWfkOUis Γ;οίί·5ϊ. j : i'OX' ί,χ·>Χ ί ί·: i,X>SiXX ) ! x^r, Kxxwdiiies iX'ixs·?· ic'»ll Sislss; «ttiijxpts '> 0 CSX*i5««SS “ <! ϊ·θί.>· “ 0 •sol » 0 f.srget ® 7 iitfip “ 5 § ijiHYd Ϊ.Χ7 PS ."«.lax'iviii.ly ρχ'ίχχχ ts qi',s'.cs«is.l«s «h.Us: ichss'ices < t.isrg-st; iji’.ci iU'.tdsxpf.s x qr .sxixixlxvs cGXifiikx'.i.xsxXvSxil'SS CiSisni.} ,i ir rovi <»: S; XX>S,J 7 S' :SK-«;q ,i .¾ ι·;··,·>1 s's g; xxei ss st.s'p ii {xxu'S'.Os'Txx.ls xXfiXS u'sot qs,»sxiu,l{sstri«xnf:’7X! H : i Ί'ιη·ϊ·ϊ ;rik;« 0'';5 tts X’i! χ·5ί.',Κ',ί>«',.ίΧ«;ΐ8 · ro«J i.CsSi-l 7'γ««: qx: jf;,.s!-x1sil>-is : i'owj |cx>iV » Txxxa Ρίί!77·95·<.7 ί·« 5, xx-lsss; i f XJ.V, «KSdxi X e ;'S i ίχ·5«) IC: s I; xxr,svsdxi.Uxfi i ix>;.i J ί | s pqlsa qx‘ ia,sodiS.li!Skx'<>»] -- f.'hfi's.gii's -isv 1 xxol ss g-iiip i-f x'.ixl I's qs: .iXi'iiXisJsiS ci-d!-!!:.: CO.l -s tqj·,, SiX'RXiXpS ro'd S ··' ;ίΐ«ρ if x'fs« fpx'..ifttJxksisq ccRtdC; row -s-^ xqr.ox-ido.Uxi! jrous'.i;

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® cs!· '· q rc χχΧρ > ccsn ;st is®t x <. SJBSOR CGKRECT K qsj.ip s χμ,'ΡίχΧίϊ, ORCod« («qi:cRy_yxcqxrqcf.is>r.s:®s;,55 ^ s.B-i-af.-fi-jiitfR';,. S.oijbXxxci » x-ircRxcis,Qs'Cexioίχ>ΐ'ί-·»«„«Ρί;χχ>Ρ'ί,ίθ8”®ϊ:!ΐ5; f 'd«'"js«txvst«d, bisoElSvi qr x;i« qr;;;xx;t·! ,QRC-dd;H'sirrx>-x\^Cx'!iX’e<:Kiis55-^«'Cfii5 f tis’S'-aciK.i'vXiSfids S-kss !; foi: .ipwisidifi inf

xix_®-s -- xpxvXfxia.-SRCodsisi.'ssi· cor.tssctJ.sso^i·!!",®,! X Rvxsixxqxod, SsifibidcS i|r__sci » qrcxxq«,crpc:o«iouxrrx>s___ctxrrtxctx!>f>s>«cj-;} 5.; ,χχΟχ'ν-®Χχ·ίχΧ< SSisobifiXi qxy^ad " qrsxxx;ek(ECxxX®iqi'ri>iy^_dx'irsscKioj'.'‘Sx»t;Ki5 f Jictiwatsfi, Mijs-b ix>s.' xqoisi.dl>s i«k qr ρ.ίδ, add^^diSKs C' Bn-'SKtivafaxi ‘ j qr^^uxk-axifijxU'iXa i'' do-'-ax'txvstftiS') xxr_ _uix.,,aqx5__d»tf; ·;'' yn-oC.';iAS5t«cj' S qs jse. aiXtS_q.std i ’ Rpti v;st«d.,, ‘) qr__afi.iRls'i__xUxKxi; 'Rctixfstxxd, ,, '} , i · At-XtiVcif Sid >. ) !'jisabl>3 iqr__scS, qs -trijs ; xUsabx® Iqry^ack qx\„f:sa,. Bdid®; iisvdjpfsg < kxiy u«,pqg', xpq^.ik·;; save_ png (’ qx.^xxl.png ’ ,. ; S«v»_pnq {’ qr. j.iai,pog', qi- panp Sixx'd^pao {' .-.P79' t -s-'-'^'Wi f sax'P^png ί' q.v psd, png ’,. xpr/iii j s;svis_j5«q ;' qr^atp, ppq * , qs^^ssp)

To summariss 11¾¾ above, an embodiment of the present irweotbo provkies a iec-hnique lor iorf cabng a state of enviroiimentat exposore of rei artioie by use of an ac-live substance (e.g. “active" which changes appearance with some iorrri of environmental exposure which is of interest. Dual codes such as QR codes are prepared to represerst tfse “before” and 'after” state respectively. Error ccrrectior> and/or positional information employed in the codes is selectively undermined by-altering each code based on whether it is intended to represent the state of the ariicie before or after activation of the active substance as a result of the environmental exposure. Before environrrrenlal exposure die undermirred code of one code (qr_ad) fails to read, while the other code (qr„ue) reads correctly. As a result of environmental action such as heat or light, the chemical (and therefore colour) changes in the active substance used to print U-se codes cause the opposite effect such that the previously unreadable code can now be read (qr„ae) and the other code (qr„uo) is now unreadable. In this way, scanning the codes before and after the environmental exposure produces two different messages. I herefore, the preparation process undermines the error correction In two distinct codes to aiiow only one type of active substance to be used to accomplish the same effect as one code using multiple ective substances.

Various modincatlons are possible within the scope of the invention.

Reference has bean made above to an ''article” to which the codes are affixed in some way. However, the present invention is not restricted to articles as such, but may also be applied to other things, including living things. For example the present Invention could be applied in the form of (temporary) tattoos applied to the skin of a human (such as a medicai patient) or to the fur or coal of an animal.

Although reference is made above to a “tag”, the tag as such is not essential. The codes can be associated in other ways with a thing whose environmental exposure Is to be indicated. For example where Ihe subject of interest is an article of doihing (or a human wearing the clothing) the machine readable codes can be incorporated Into ihe fabric of the clothing by being woven or knitted with special reactive fibres. In this case the fibres act as the active substance referred to above. As another example, the codes may be formed by moulding or iniaying applied to the surface of an article, using for example smai! pieces of a plastic materia! which reacts to the environmental exposure.

Thus, printing is not esseretiai to the invention, in cases iMiere ink is printed, as in the described embodiment, Uie term “ink” is to be interpreted broadiy, For exampie same thermochromic inks ir^ciude thermochromatic liquid crystals.

The present invention is not limited with respect to the type of environmental exposure. In addition to exposure to ambient air, iight and humidity etc., the environmental exposure can indude, for axemple, immersion in a liquid, breathing on the active-substance, or wiping with a medium capable of activating the nclive substance. Thus, the term “efivironmerif is to be construed broadly.

Tt?e present Invention may have appiications in the field of hesithcare, A specific exampie is a code card, printed with multiple pairs of codes each identifying the presence of a specifsc toxin, bacteria, virus or other pathogen. I bis couid ba attached to a patient or simply i^ng up in a hospital room or the like. Another example is a stick-on tattoo incorporating an active substance capable of reacting to a patient’s temperature or perspiraiion. As a related possibility, an active substance applied to forming a pair of codes in the fur of an animal (or on a collar, leg ring or the like) could be used to indicate exposure to a specific pathogen affecting that species of animal.

In the above embodiment, templates are applied to the ceils which provide the data content of the QR code. However, this is not essential. In an aiternalive errsbodiment, vdiere a friactiine-readable code includes non-data parts {such as the Finder patterns in Fig. 2) It is possible to appiy the principle of the Invention to these patterres instead of (or as well as) to the date pari of the code. In this way the readability of the code itseif is undermined rather than Just the error correction applied to the data pari. The two embodiments can be combined.

As already mentioned, the terms “biack" and "white” in this specification are labels for two distinguishable states. In practice they may be substituted by iight and dark shades of the grey or of one colour, or even by different colours so long as these are capable of being distinguished by a scanner.

Moreover, the two states are reversible; references above to "black" and "whltsr respectively can be reversed so that the template bits cl'fange froai dark to light rattier than the other way round. In this case, the active ink is a "disappearing” ink rather than an "invisible" ink.

Above, it was assumed that a “white" cell represents binary "O’' and that a “biack” cell represents binary "1”; of course, this convention could be reversed If preferred, as long as the Finder (12)^ Timing (16), Alignment (14) and Quiet (20) patterns as well as the other size, mask Indicator, error correction fnrjde and so tortti remain as defined by the specification, A combination of more than two codes may br-j used if desired to provide multiple messages. This can Include providing respective pairs of codes in which different active inks are used, in prder to reveal more than one possible type of environmental exposure. For example it may be desired to sho’w whether or not ait artlde has been sterilized in addition to whether or not the article has been exposed to air for a predetermined period, and different active inks may be required for this.

The article to which the codes are affixed may have ether loT-reiated capabilities such an RFID tag or GPS device, multiplying the possible uses of the Invention.

The OR codes used In ttie above embodiment are just an example. The present Invention can be applied to other forma of machlne-readable codes, at least 2~D codes and possibly also 1“D codes. tn fact the same strategy, selectively enabiing and disabling multiple Instances of an error correction encode message, could be applied In any situaticn wfiere multiple messages mlgtU be sent In parallel where changes might occur.

Incidentally, although Reed-Solomon Code is part of the OR standard, it Is not essential to the Invention. Reed~Solomon Code is a subset of BCH codes, and there are other types of coding which could be applied to machine-readable codes end with which the present invention could therefore he applied.

As indicated above, at ieast some features of the invention may be performed by a processor executing correpuier program code. As referred hereire, a processor may indisde one or more generai-purpose processing devices such as a microprocessor, centra! processirig uriit, or the like. The processor may include a complex instruction set coniputifig (CiSC) micropf ocessor, reduced iristruction set compuUng {RISC) microprocessor, very iong instruction word {VUW) microprocessor, or a processor impiementing other instruction sets or processors implementing a combination of irsstruction sets. The processor may also inciude one or more special-purpose processing devices such as an application specific integrated circuit (ASIC), a field programmable gale amay (FPGA), a digital signal processor (DSP), network processor, or the like. In one or more embodiments, a processor is configured to execute instructions for performing the operations and steps discussed herein.

The computer program code referred to above may be stored on a data storage device. Ttie data storage device nsay irsciude a computer readable medium, whose term may refer to a single medium or muitipSe media (e.g,, a centrailMd or distributed database and/or associated caches and servers) configured to cany computer-executable Instrudloris or have data structures stored thereon. Computer-executable instructions may indude, for example, instrucdons and data accessibie by and causing a general purpose computer, spedai purpose computer, or special purpose processing device (e.g., one or more processors) to pe:form one or more functions or operations. Thus, the term “coniputer-readable storage medium” may also inciude any medium that is capable of storing, encoding or carrying a set of iiistructions for execution by the machine and that cause the machine to perform any one or more of the methods of the present disclosure. The term "computer-readable storage medium” may accordingly be taken to indude, but not be limited to, solid-state memories, optical media and niagnetic .nisdia. By way of exairspie, and not limitation, such computer-readeble .media may inciude non-transitory computer-readable storage media, indudlno Random .Access Memory (RAM), Read-Only Memory (ROM), Eiectriceiiy Erasable F’rogrammabie Read-Only Memory (EEPRDM), Compact Disc Reed-Only Meniory (CD-ROM) or othr^r optical disk storage, magnetic disk storage or other magnetic storage devices, flash memory devises (e,g., solid state rnenmry devices).

This invention will significaritly sirfipiify and raduce the cost of forming active codes capable of reacting to environmental exposure, 8y ailowinQ the use of a single active-substance, the chemistry is significantly sinipliOed, allowing active codes to be ernpioyed more widely and adding a potentially large number of items to Itie internet of Things. More generaiiy, the present invention allows environmental exposure to be indicated for a wide variety of things, including iivlng things, allowing their condition to be niaohiine-read both before and after the environmental exposure.

Claims (14)

1. Claims

   1, A method of indicating a change of stats of an article due to efivironmentai exposure by use of a pair of machirssmeadabie codeS; the method comprising formlrig first afrd secorsd cods for use on the artiole, the forming ssioctlvely employing an active substance which changes appearance under the envirorunerrial exposure such that whether the first and second code are capable of being maohme read changes Indepersdentiy for each code.
2. 2, The method according to claim 1 wherein: the first tag is readable prior to the environmental exposure but Is unreadable after tt?e envlronmenisl exposure; and the second tag is not readable before the erivlronmentai exposure but is readable after the environmental exposure. •3, The method accordirig to claim 1 or 2 wherein the active substance comprises an active ink and flm forming is performed by printing.
3. 4. The method according to oiaifri 3 srhereln the printing comprises first printing the codes with a non-active ink foliowed by second printing with the active ink to overprint selected parts of the code.
4. 5. The methr>d according to any preceding claim wtiereiri each code cornprises a data part and a non-date part, and forming by the active substance occurs In selected podions of each code to niodify at least one of the data part and the non-data part.
5. 6. The method according to claim 5 wherein the active substance is formed in in the data part of each code, fo corrupt or repair error correction coding applied to the data part.
6. 7. Tho method accordlrtg to claim 6 or 6 wherein the active substance Is formed in the non-data part to corrupt or repair positional information In the non-data part. S. The method according to ciaim 6 or 7 wherein forming the active snbslaiice fias no effeci on first code prior to the onvironmentai exposure and corrupts the first code following the environmental exposure, whilst having no effect the second code prior to the environmental exposure and repairing the second cods after the environmental exposure.
7. 9, The method according to any preceding claim wherein the envlronmenlai exposure includes exposure to orre or nrore of; high temperature low temperature visible light UV light water or moisture gas or volatile chemical toxin bacteria virus the elapse of time.
8. 10. The oiettred aocofding to any preceding claim wherein the active substance Is one of; a substance wfiioh darkens under l\\e envifonmentai exposure; arid a substance which lightens under the environmentsi exposure.
9. 11, The method according to any preceding cialm wherein the active substance coniprises at least one of: an active ink; a fibre; an inlaid material.
10. 12. The nrettrod according to any precediiKi claim wtierein each code is a QR code.
11. 13. An ariide having applied to it first and second codes prepared in accordance with the fnethod according ίο any preceding daim, the codes indicatirig a state of envirorimerdat exposure of the articte.
12. 14. An articie to which is applied firs- and second machine-readabte codes which are formed by .seiecliveiy applying an active substance which ctianges appearance under environmentai exposure, such that whether ihe first and second codes are capable of being niactiine read cl'sanges independently for each code.
13. 15, The articie according to ctaini 14 wherein the first code Is readable prior to the erivironmentai exposure but Is unreadable after the environmental exposure, and the second code is not readable before the environmeritai exposure but is readable after the environmental exposure.
14. 16, Computer program code for isse ΙίΊ preparation of first and second machine» readable codes iormed using an active substance, the code when executed by a computer performing operations of; 0) an the basis of e desired nmssage for each of the first and second codes preparing enabled and un"activated {qr...us) and enabled and activated (qr_ae) versions of the codes; (ii; using duplicates of the versions prepared in (I), creating disabled versions of each code (qr_ud, qr..ad) in which selected portions are reversed in tf^eir visual appearance; and (ill) create templates (qr„um, qr„am) Incturling the portions selected in (II), to be formed using the active substance,