Abstract:
A method of applying content and a data encoding pattern  18  to a product  10  comprises: applying the content  14  to a substrate  12 ; modifying the reflectivity of the content  14  at a predetermined wavelength; and applying the pattern  18  to the product, wherein the method is such that the pattern can be distinguished from the content at the predetermined wavelength.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to products having human readable content and data encoding pattern thereon.  
       BACKGROUND TO THE INVENTION  
       [0002]     It is known to provide data encoding pattern on products, for example documents, so that a hand held device, such as a pen, can read the data encoded in the pattern and use it, for example, to detect its position as it is moved over the document. Where the hand held device is a pen arranged to mark the product, the position of marks made on the documents can be detected by the pen, thereby enabling the position of the marks on the document to be stored electronically as they are made.  
         [0003]     Where the product has human readable content applied to it as well as the position identifying pattern, it can be a problem to ensure that the pattern is not obscured by the content. It is possible to overcome this problem by printing the pattern and the content using different inks. This enables the pen to detect the pattern using light at a wavelength that is absorbed or reflected by the pattern but not the content, or by the content and not the pattern. However, this requires the use of two different inks, which can add to the complexity of the printing process.  
       SUMMARY OF THE INVENTION  
       [0004]     The present invention provides a method of applying content and a data encoding pattern to a product, the method comprising: 
        applying the content to a substrate;     modifying the reflectivity of the content at a predetermined wavelength; and     applying the pattern to the product,     the method being such that the pattern is distinguishable from the content at the predetermined wavelength.        
 
         [0009]     It will be appreciated that modifying the reflectivity of the content will generally also involve modifying the absorption of the content. Therefore the step of modifying the reflectivity is equivalent to modifying the absorption.  
         [0010]     The reflectivity, or the absorption, of the content may be modified in a number of ways. For example filter material may be applied over the content to increase its reflectivity, and reduce its absorption. The reflectivity of the content may be modified by the manner in which it is applied to the substrate. For example the content may be applied to the rear surface of a layer of filter material, and then that rear surface brought into contact with the substrate thereby simultaneously applying the content to the substrate and increasing its reflectivity by covering it with the filter material.  
         [0011]     The data encoding pattern may be a position identifying pattern. Such a pattern may be arranged such that any part of the pattern, provided it is of a large enough area, uniquely defines a position on the product.  
         [0012]     The present invention further provides apparatus for use in producing a document having content and data encoding pattern thereon, the apparatus comprising a printing system arranged to print the content onto a substrate and a reflectivity modifying system arranged to modify the reflectivity of the content at a predetermined wavelength such that the pattern is distinguishable from the content at the predetermined wavelength.  
         [0013]     A corresponding product is also provided.  
         [0014]     In another aspect of the invention, a product having content thereon is provided, the product having a data encoding pattern, and filter material between the data encoding pattern and the content, wherein the filter material overlaps with the content on at least a part of the product. A method of applying a data encoding pattern to a product is also provided, the method comprising: 
        providing a product with a content;     modifying the reflectivity of the content at a predetermined wavelength; and     applying the pattern to the product so as to overlap with the content on at least a part of the product,     the method being such that the pattern is distinguishable from the content at the predetermined wavelength.        
 
         [0019]     Preferred embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]      FIG. 1  shows the component parts of a document according to a first embodiment of the invention;  
         [0021]      FIG. 2  is a graph showing the filter characteristic of a filter layer of the document of  FIG. 1 ;  
         [0022]      FIG. 3  is a schematic diagram of a system for processing the document of  FIG. 1 ;  
         [0023]      FIG. 3A  is a schematic diagram of a system according to an embodiment of the invention for producing the document of  FIG. 1 ;  
         [0024]      FIG. 4  is a schematic diagram of a system according to a further embodiment of the invention for producing a document;  
         [0025]      FIG. 5  is a schematic section through a printer according to a further embodiment of the invention for producing a document;  
         [0026]      FIG. 6  is a schematic section through a printer according to a further embodiment of the invention for producing a document. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0027]     Referring to  FIG. 1 a  document  10  according to an embodiment of the invention comprises a paper substrate  12  having content  14  printed on it, and a filter layer  16  having a machine-readable position identifying pattern  18  on it. The document  10  is a form, and the content  14  comprises text  20  and graphics  22 , which are printed onto the substrate  12  using a carbon-based black ink as a marking material, by means of a monochrome laser jet printer. This marking material is relatively un-reflective of light at visible wavelengths, so that it appears black to the human eye, and un-reflective at infra-red wavelengths also so that IR light will be absorbed by it, and it will appear ‘black’ i.e. non-reflective, to the IR sensor. The substrate  12  has a higher reflectivity at infra red wavelengths then the ink so that the ink can normally be detected by an IR sensing system when applied to the substrate. The filter layer  16  comprises a film of material that is transparent at visible wavelengths, but opaque to, and highly reflective of, infra-red light. The filter layer  16  has the position identifying pattern  18  printed onto its upper surface using the same carbon-based black ink as the content  14  of the document. The position identifying pattern can take a number of forms for example it may comprise a number of dots printed at predetermined positions on an imaginary grid, as described in our copending patent application GB 0321174.5, or as described in WO 01/26032.  
         [0028]     Referring to  FIG. 2 , the filter layer  16  has a transmissivity that is high for visible wavelengths of within a wavelength band from 400 nm to 700 nm, but low for infra-red wavelengths between about 780 nm and 3000 nm. In this IR wavelength range the filter layer  16  has a high reflectivity, and low absorption. In particular the reflectivity of the filter layer  16  is higher in the IR range than the ink that forms the content and pattern, and its absorption is lower in the IR range. The filter layer therefore increases the reflectivity and reduces the absorption of the content over which it extends. The result of this structure of the document is that the reflectivity of the content at IR wavelengths is different from the reflectivity of the pattern at IR wavelengths. Therefore if IR light is directed at the document, the position identifying pattern  18  on the top surface of the filter layer  16  will absorb it, but the incident IR light that does not strike the pattern will be reflected by the filter layer  16 , regardless of whether it strikes an area where there is content, or an area where there is not content or pattern. Therefore an IR sensor held over the document will detect IR light reflected from all areas of the document except those covered by the pattern  18 , but will not detect significant levels of light reflected from the pattern  18 . It will therefore be able to image the pattern but not the content.  
         [0029]     Referring to  FIG. 3 , a pen  350  for reading the pattern areas comprises a writing nib  351 , and a camera  352  made up of an infra red (IR) LED  354  and an IR sensor  356 . The camera  352  is arranged to image a circular area adjacent to the tip of the pen nib  351 . A processor  358  processes images from the camera  352  taken at a predetermined rapid sample rate. A pressure sensor  360  detects when the nib  351  is in contact with the document  10  and triggers operation of the camera  352 . Whenever the pen is being used on a patterned area of the document  10 , the processor  358  can therefore determine from the pattern  18  the position, within the defined pattern area, of the pattern  18  over which the pen  350  is being passed. The sequence of positions is saved in the pen&#39;s memory  362  as pen stroke data, and can be transmitted to the PC  300  via a radio frequency transmitter  364  in the pen  350 . A simple cable connection can also be used. Suitable pens are available from Logitech under the trade mark Logitech Io.  
         [0030]     A very simple system according to an embodiment of the invention for designing and producing printed documents  100  having the position identifying pattern on them comprises a personal computer (PC)  300  and a printer  400 . The PC  30  has a screen  304 , a keyboard  306  and a mouse  308  connected to it. As shown in  FIG. 3A , the PC  301  comprises a processor  410  and a pattern allocation module  412  which is a software module stored in memory. The pattern allocation module  412  includes the definition of the total area of pattern space and a record of which parts of that total area have been allocated to specific documents, for example by means of coordinate references. It also includes a definition of the areas of pattern  18 . The PC  300  further comprises a printer driver  414 , which is a further software module, and a memory  416  having electronic documents  418  stored in it. A user interface allows a user to interact with the PC  301 .  
         [0031]     When a document  418  is to be printed, the electronic document is retrieved from memory  416 . This document includes a definition of the content of the document. The printer driver  414  also requests the required amount of pattern from the pattern allocation module  412 , which allocates an area of pattern to the document. Printing of the content and the pattern can be achieved in a number of different ways, as will be described in more detail below.  
         [0032]     Referring to  FIG. 4 , the printer  400  is a monochrome laser-jet printer  400  arranged to print the content  14  and the position identifying pattern  18  of the document  10 . The printer  400  comprises a paper tray  402  in which paper  404  can be stored ready for printing, a photoreceptor drum  406  arranged to apply ink to the paper  404 , an ink reservoir  408  and ink transfer roller  410  arranged to transfer ink  411  from the reservoir  408  to the drum  406 . A scanning laser source  412  and reflector  413  are arranged to direct laser light at parts of the drum  406  to charge them electrostatically, whilst leaving other parts of the drum  406  uncharged. The charged areas of the drum  406  collect ink from the reservoir  408  via the transfer roller  410 , and the uncharged areas of the drum  406  collect no ink. A controller  416  is arranged to control the scanning laser source  412 , which is turned on and off as it scans across the surface of the drum  406 , thereby to control which areas of the drum  406  transfer ink to the paper, and hence which areas of the paper  404  have ink  411  applied to them and which do not. The paper is transferred from the paper tray  402 , past the drum  406 , and out of the printer  400  by means of a number of rollers  414 , also under control of the controller  416 .  
         [0033]     In a simple process for producing the document  10 , the substrate  12  comprises a sheet of paper  404  from the paper tray  402  of the printer  400 , which is printed on its top surface with content  14  in conventional manner from black carbon based ink  411  using the printer  400 . A sheet of filter material  16  is then loaded into the paper tray  402  and printed on its top surface with position identifying pattern  18  using the same ink  411 . The sheet of filter material  16  is then placed over the top surface of the paper  404 , with its top surface away from the paper  404  and its under surface towards the paper  404 , and attached to the paper  404 , for example by adhesive. The content  14  is therefore covered by the filter layer  16 , and the position identifying pattern  18  carried on the outer surface of the filter layer  16 . The pattern covers the whole surface of the document and therefore overlaps with the content.  
         [0034]     When the pen  350  is used to write on the document  10 , the camera  352  detects the pattern  18  using light from the IR source  354  that is reflected from all areas of the document except the pattern  18  on the top surface of the filter layer  16 . Therefore the reflectivity of the content at IR wavelengths is increased so that the same levels of IR light, from the source  354 , are reflected by the content  14  as by the areas of the document having no content or pattern on them. The pattern  10  can therefore be detected by the detector  356 . The IR camera  352  in the pen  350  will therefore form an image that includes the pattern  18  but does not include the content  14 . Therefore in areas of the document where the pattern  18  and the content  14  are superimposed on each other, the camera  352  in the pen  350  will still be able to form an image of the pattern that is not obscured by the content  14 . This enables the pen to determine its position on the document  10  over the whole of the area of the document  10  including areas of overlap of the pattern  18  and content  14 . To the human eye the pattern  18  may be obscured by the content in such areas of overlap, because the filter layer  16  is not effective at visible wavelengths. However this means that the content  14  remains visible to through the filter layer  16 , and since the pattern  18  is made up of a number of small dots it appears to the human eye as a light grey shading and generally does not obscure the content  14 .  
         [0035]     It will be understood that the document  10  may comprise other layers. For example the paper  12  could have other coatings applied to it before the content  14  is printed onto it. Also other coatings could be applied over the content  14  either before or after the filter material  16 , provided they do not adversely affect the optical properties of the document. Furthermore additional layers of material can be applied over the pattern  18 , for example to provide further protection, provided of course that they allow the IR light to be transmitted through them.  
         [0036]     In a further modification to this method, the content may be printed onto the rear side of the filter layer  16 , and the pattern  18  printed onto the front side of the filter layer  16 . The filter layer is then applied to the paper substrate with its rear side downwards. This simultaneously applies the content to the paper, and covers the content with the filter layer thereby increasing its reflectivity. It also results in the content being between the filter layer  16  and the paper substrate  12 , and the pattern  18  being on top of the filter layer  16 .  
         [0037]     Referring to  FIG. 5 , a printer according to a second embodiment of the invention is similar to that of  FIG. 4  with corresponding components indicated by the same reference numerals increased by  100 . In this case the printer includes a further reservoir  520  for liquid filter material and a filter layer application roller  522  arranged to apply a layer of the filter material  524  over the whole of the top surface of the document  504  after the content has been printed onto it. The filter material  524  in this case is and cures after application to form a continuous filter layer over the surface of the document, covering the content that has been printed onto the paper  504 . The paper  504  with the content and filter layer applied to it is then passed through the printer again, which is this time arranged to print the pattern onto the filter layer using the carbon based ink from the reservoir  508 . When the pattern is being printed the filter layer application roller  522  is retracted so that filter material  524  is not applied over the pattern. Once the pattern has been printed the document is essentially the same as that produced on the system of  FIG. 4  as described above, with the position identifying pattern visible to the IR camera and the content invisible to the IR camera because it is obscured by the layer of filter material  524 .  
         [0038]     It will be appreciated that, rather than the filter material being applied as a continuous layer over the whole surface of the paper  504 , it can be applied only on those areas that have content applied to them, provided the whole of the content is covered by the filter material.  
         [0039]     In a modification to the system of  FIG. 5 , the printer can be arranged to apply the filter material to both sides of the document. This forms a protective coating over the whole document that can be used either to strengthen the document or to render it waterproof. The same effect can be obtained by applying the pre-prepared layers of filter material  16  of  FIG. 1  to both sides of the document, or different types of material to the front and rear of the document. Clearly if the content is only applied to one side of the document then the filter material only needs to be applied to that side, and a non-filtering material can be used as a coating on the rear, but if content and pattern are applied to both surfaces then the filter material needs to be used on both surfaces.  
         [0040]     It will be appreciated that the production of the documents as described with reference to  FIGS. 4 and 5  can be automated to a greater or lesser extent. For example, referring to  FIG. 6 , an automated document producing system comprises a printer  600  which is similar to that shown in  FIG. 4 , with two paper trays  602 ,  603 , one of which  602  is loaded with paper  12  and the other of which  603  is loaded with sheets of filter material  16 . The system is arranged to pick up a sheet of paper from the paper tray  602  and print the content onto the paper. It is then arranged to pick up a sheet of filter material  16  from the filter material tray  603  and transfer it to a laminating station  617  where the filter layer  16  is applied to the top surface of the paper  12  over the printed content, and affixed to it, for example my means of adhesive. It then passes the laminated paper and filter layer back through the printer and prints the pattern  18  onto the top surface of the filter layer  16 .  
         [0041]     In a particular embodiment, the invention is used in the medical field with a substrate such as an X-Ray print. In this particular embodiment, the filter may overlap at least part of the content and may comprise a visible grid in addition to the pattern. The grid may assist a practitioner to take measurements on the print. The grid may be a linear Cartesian grid or may be a non-linear grid suited for specific measurements. Measurements and comments written by the practitioner may be recorded using a pen as in  FIG. 3 .  
         [0042]     While the examples described above use IR light and modification in reflectivity of the content at IR wavelengths, the system can work equally well with other wavelengths or ranges of wavelengths. For example visible or UV wavelengths could be used.  
         [0043]     Also the wavelength of light used, and at which the sensor can detect, can be one at which the pattern and the content are both reflective, or at least more reflective than filter layer. The filter layer will then absorb more of the light at that wavelength than the pattern. The pattern will therefore still be visible to the sensor because it still has a different reflectivity at the relevant wavelength to the filter layer. However, it will reflect more light than the filter layer, rather than less.  
         [0044]     In the other aspect of the invention, the filter overlaps at lest part of the content as for example in  FIG. 1 . In an embodiment,  10  is not a document but a screen such as a TV, printer, tablet PC, vending machine, cash machine, mobile phone, camera or computer screen for example. In the same manner as described for a document, the filter of the invention overlaps at least partially the screen. In an embodiment of this aspect, the pattern is a position identifying pattern allowing interaction with a screen using a pen as described in  FIG. 3 . This provides a simple way of creating an equivalent of touch screen. In a particular embodiment, this aspect is put into practice for voting on screen or passing examinations on screens. In a particular embodiment, the filter is transparent for at least some of the wavelengths of the human visible spectrum.