GB2421617A

GB2421617A - Products with data encoding pattern

Info

Publication number: GB2421617A
Application number: GB0428357A
Authority: GB
Inventors: Manuel Gonzalez
Original assignee: Hewlett Packard Development Co LP
Current assignee: Hewlett Packard Development Co LP
Priority date: 2004-12-24
Filing date: 2004-12-24
Publication date: 2006-06-28
Anticipated expiration: 2024-12-24
Also published as: GB2421617B; GB0428357D0; GB2421618A; GB0508167D0

Abstract

A product has a data encoding pattern on it. The pattern comprises a first set of pattern elements defining a first set 210 of part circles centred on a first reference point 211 and a second set of pattern elements defining a second set 220 of part circles centred on a second reference point 221.

Description

PRODUCTS WITH DATA ENCODING PATTERN

FIELD OF THE INVENTION

The present invention relates to products having data encoding pattern on them.

BACKGROUND TO THE INVENTION

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.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided a product having a data encoding pattern thereon, the pattern comprising a first set of pattern elements defining a first set of part circles centred on a first reference point and a second set of pattern elements defining a second set of part circles centred on a second reference point.

The part circles, or arcs, can be combined to form a whole circle. For example, when a reference point is provided on a product and near the middle of the product, the smaller radius arcs will join to form whole circles. The larger radius arcs, i.e. those near the edge of the document, will not form whole circles since they will be interrupted by edge(s) of the document.

According to a second aspect of the invention, there is provided a method of generating a data encoding pattern for application to a product, the method comprising the steps of: defining a first set of concentric part circles centred on a first reference point; defining a second set of concentric part circles centred on a second reference point, and defining positions of pattern elements relative to the part circles.

According to a third aspect of the invention, there is provided a method of reading data from a pattern on a product comprising: imaging an area of the pattern; defining within the imaged area a part of a line from a first set of part circles centred on a first reference point and a part of a line from a second set of part circles centred on a second reference point; and identifying data associated with the line parts.

According to a fourth aspect of the invention there is provided a system for reading data from a pattern on a product, the system comprising imaging means arranged to image an area of the product, and processing means arranged to: identify within the imaged area a part of a line from a first set of part circles centred on a first reference point and a part of a line from a second set of part circles centred on a second reference point; and identify data associated with the line parts.

According to a fifth aspect of the invention, there is provided the system of the fourth aspect of the invention arranged to carry out the method of the third aspect of the invention.

According to a sixth aspect of the invention, there is provided a data carrier carrying data arranged to cause a computer system to operate as a system according to, or to perform the method of, any of the second to fifth aspects of the invention.

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

Figure 1 shows schematically a document according to an embodiment of the invention and a pen for use with the document; Figures 2a to 2f show line forms that can be used on the document of Figure 1; Figure 3 shows an enlarged portion of a data encoding pattern on the Locument of Figure 1; Figure 4 is a schematic diagram of a system for producing a document according to a second embodiment of the invention; Figure 5 is a diagram of the functional blocks of the system of Figure 4; Figure 6 is a flow diagram illustrating a method according to an embodiment of the invention of producing a document on the system of Figure 4; Figure 7 is a schematic enlarged view of part of a data encoding pattern produced on the system of Figure 4; Figure 8 shows schematically a document according to another embodiment of the invention; Figure 9 shows schematically a document according to a further embodiment of the invention; and Figures lOa to lOe show dot forms used to form pattern elements.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to Figure 1, a document 2 according to the invention for use in a digital pen and paper system comprises a carrier 3 in the form of a single sheet of paper 4 with position identifying markings 5 printed on some parts of it. The markings 5, which are not shown to scale in Figure 1, form a position identifying pattern 6 on the document 2. Also printed on the paper 4 are further markings 7 which are clearly visible to a human user of the document, and which make up the human visible content of the document 2. The content 7 is in the form of a number of lines and text and graphic features which extend over, and are therefore superimposed upon, the pattern 6.

A pen 8, for use with the document 2, comprises a writing nib 10, and a camera 12 made up of an infra red (IR) LED 14 and a CMOS sensor 16.

The camera 12 is arranged to image a circular area adjacent to the tip 11 of the pen nib 10. A processor 18 processes images from the camera 12 taken at a predetermined rapid sample rate. A pressure sensor 20 detects when the nib 10 is in contact with the document 2 and triggers operation of the camera 12. Whenever the pen is being used on an area of the document 2 having the pattern 6 on it, the processor 18 can determine from the pattern 6 the position of the area of pattern imaged by the camera 12 whenever the nib 10 of the pen is in contact with the document 2. From this, and a known offset between the camera 12 and the nib 10, it can determine the position of the nib 10 of the pen, and hence the shape of any marks made on the patterned areas of the document 2. This information is stored in a memory 22 in the pen as it is being used. When the user has finished marking the document 2, this is recorded in a document completion process, for example by making a mark with the pen 8 in a send box 9. The pen is arranged to recognise the pattern in the send box 9 and send the pen stoke data to a pen stroke interpretation system in a suitable manner, for example via a radio transceiver 24 which provides a Bluetooth radio link with an internet connected PC. Suitable pens are available from Logitech under the trade mark Logitech Jo, and from Nokia. Additionally or alternatively a docking station may be provided for docking the pen. In the docking station, the pen stroke data is downloaded before being sent via a cable link or a radio link to a pen stroke interpretation system. If a docking station is used the document does not need to include the send box 9 to trigger sending of the pen stroke data.

Referring to Figure 2a, the markings 5 comprise a plurality of pattern elements 200a each of which is in the form of a solid part-circular line 200.

Referring to Figure 3, the lines 200 are spaced apart on the document 2 in a first concentric set 210 and a second concentric set 220. The centre of each set 210, 220 is at a known location on the page. In this embodiment, the first concentric set 210 centres around a first reference point which is a top left hand corner 211 of the sheet of paper 4 and the second concentric set 220 centres around a second reference point which is a top right hand corner 221 of the sheet of paper 4. Therefore each of the lines 200 comprises a quarter circle or quadrant, and the pattern at any point on the document is unique. In this embodiment the first and second 210, 220 concentric sets of lines are all solid lines as shown in Figure 2a.

Adjacent lines 200 in each set 210, 220 are close enough to each other such that when the camera 12 captures an image, at least part of a line from each set is imaged. In this case the spacing of the lines is 2mm.

In this embodiment a number of identical sheets of paper having the pattern 6 on them are produced by offset printing, and a user then prints the content over the pattern 6 using a printer such as a laser jet printer.

Once the document has been printed, the pen 8 can be used to mark the document and to store electronically details of all marks made. This enables processing of the marks made on the document. As the pen 8 is moved over the document 2, the camera 12 stores an image of an area of 3mm square of the document at regular intervals. The imaged area will therefore always include a part of at least one line 200 from each set 210,220 in a 3x3mm square block. The processor 18 analyses each image and maps three spaced points 215, 216, 217 upon a line 200 of the first set 210. It is a known mathematical principle that given any three points on a circle, the radius of the circle and the direction of the centre of the circle from any one of the points can be calculated. Therefore from the three points 215, 216, 217, the processor 18 is arranged to identify exactly which line 200 of the first set 210 on the document 2 has been imaged. The two most distant points 215,217 are chosen to be spaced apart by as large a distance as possible, within the imaged area, and the third point 216 is approximately equidistant from both 215,217. In this way the accuracy of the determination of the radius of the line 200a of the first set 210 and thus the position of the first reference point is increased.

The accuracy may also be increased by increasing the number of points which are mapped. Similarly, the processor 18 is arranged to identify which line 200 of the second set 220 has been imaged by mapping three points 225,226,227 on a line 200a of the second set 220.

Since the distance and direction, from the identified points in the imaged area, of each of the top left 211 and top right 221 corners of the document are known, it is possible to determine the exact location of the imaged area relative to these corners 211, 221 which form the reference points in this case. The processor 18 is arranged to analyse the position of the identified lines 200a within any particular image to identify the exact location and orientation of the imaged area, and hence of the pen, on the document. When the pen position has been identified, a position code is produced, which is then time stamped with the time at which it was recorded and stored in the pen's memory 22. The pen stroke data comprising the sequence of positions recorded can then be used, when transmitted to the PC 400, to reconstruct the strokes made by the pen 8 on the document 2.

Referring to Figures 4 and 5, a very simple system for producing printed documents having the position identifying pattern on them according to a second embodiment of the invention comprises a personal computer (PC) 400 and a printer 402. The PC 400 has a screen 404, a keyboard 406 and a mouse 408 connected to it to provide a user interface 409 as shown generally in Figure 4. As also shown in Figure 5, the PC 400 comprises a processor 410 and a pattern generation module 412 which is a software module stored in memory. The pattern generation module 412 includes details of suitable location details of the first and second reference points for different sizes of printed documents, e.g. top corners for A4 and A3 sheets of paper. The PC 400 further comprises a printer driver 414, which is a further software module, and a memory 416 having electronic documents 418 stored in it. The user interface 409 allows a user to interact with the PC 400.

The printer 402 can be any printer which has sufficient resolution to print the pattern 6 and the content 7. In this case it is a 600 dots per inch (dpi) monochrome laser jet printer. In practice the smoothness of the lines will depend on the printer resolutions, for example a 2400 dpi printer can be used to provide smoother lines. Each line 200 within a set 210, 220 is arranged to be no more than 2mm away from an adjacent line 200.

Referring to Figure 5 and Figure 6 in order to produce the printed document 2 the processor 410 retrieves an electronic document 418, which may be in the form of a PDF file, from the memory 416 at step 702 and sends it to the printer driver at step 704. The electronic document 418 contains a definition of the content 7, and the areas of the document 2 which are to have the pattern 6 printed on it. At step 706 the printer driver 414 requests the required amount of pattern from the pattern generation module 412 which identifies the first and second reference points for the document, selects a suitable pattern from memory and communicates the details of the pattern including the positions of all the required lines back to the printer driver 214, which receives it at step 708. The printer driver 414 then combines the content 7 and the pattern 6 into a single file at step 710, which is typically a post script file or a PCL file, but may be a modified PDF file. This file can then be printed onto paper to produce the document. Where the pattern is applied to the whole document, the pattern 6 is the same for all documents of the same size.

In the second embodiment of this invention, the pattern 6 and content are printed at the same time onto a sheet of paper. The pattern 6 is of such a definition and line density that most conventional printers can easily print the pattern 6. Therefore a user can simply print a document containing the pattern 6 and content 2 when required. This is not always possible with some existing reference systems since they require very high resolution printers to produce more high definition/line density patterns.

The part circular lines 200a are printed in this embodiment using a lower resolution printer, e.g. 600 dpi. Since a low resolution printer can be used to produce the document of this embodiment, the invention is accessible to more users i.e. not just those with high resolution printers.

However the lines 200a produced by the low resolution printer are obviously not as smooth as those of the first embodiment. Referring to Figure 7, the pattern 6 is formed from printer dots 250 which are arranged in as close an approximation as possible to smooth circular lines. In this embodiment, the processor 18 of the pen analyses each image and maps "best fit" part circular lines onto the printer dots making up the pattern. As previously described in relation to the first embodiment, the imaged area always includes a part of a line from each set 210, 220. In this case the processor maps a first best-fit' part circular line 230 using the dots 250 defining the line from the first set 210 and a best-fit' part circular line 270 using the dots 269 defining the line from the second set 220. Then, the processor 18 selects three spaced points 215',216',217' on the imaginary line 230 of the first set 210 and three spaced points 275', 276', 277' on the imaginary line 270 from the second set. Once again, to increase accuracy, the most distant points 215',217', 275', 277' are chosen to be spaced apart as much as possible within the imaged area. The radius of each of the imaginary lines 230, 270, and the direction of the reference points from them, is then determined from these three points. The position of the reference points relative to the imaged area is then determined.

In a third embodiment, the part circular lines are formed by dots 260 (as shown in Figure 2b). Other features are identical to the first embodiment.

The dots 260 have a sufficient density such that the imaged area contains at least three dots from a part of a line from each set 210,220. The processor 18 is able to use the real positions of the imaged dots 260 to determine the positions of the first and second reference points and thus the position of the pen on the page. This embodiment uses offset printing for the pattern to ensure that the positions of the dots are accurate enough to allow accurate calculation of the radius of the circle they are part of.

It will be appreciated that, in the embodiments described, the position identifying markings define a coordinate system which is local to a page or document. Therefore all documents of the same size will have the same position identifying markings on them such that the markings serve to identify the location relative to a page and not also to identify which page the markings are on. Such embodiments are particularly useful when a user prints a document as and when it is required, and with lower resolution printers as previously described.

In a modification to the embodiment of Figure 3, the same pattern on the same scale is used on a smaller document which is narrower than that of Figure 3. In this case the reference points 211, 221 are not both at the top corners of the document but at least one of them is beyond the edge of the document. For example one reference point can be at the top left hand corner of the document and the other level with the top of the document but beyond the right hand side. Provided the pen knows where the reference points are in relation to the document, positions on the document can be determined from the pattern.

In a further modification where pattern is only required on the lower half of the document, the reference points can be located half way down the sides of the document. They are then still at the top corners of the pattern area.

Referring to Figure 8, in a further embodiment, the whole of a page or document 800 is not covered in data encoding pattern. Instead only some areas 802 of the document have pattern in them. However the pattern in those areas corresponds to the pattern in the same area of the document of Figure 2. The position of the pen is therefore determined in the same way as the embodiment of Figure 3, but this is only possible within the patterned areas 802. This allows areas of the document where a user is not expected to write to be kept free of pattern.

In other embodiments, different discrete pattern elements may be used.

Some of these are shown in Figures 2c to 2f and include dashed lines, combinations of dots, dashes and solid lines. Lines within a set may have different forms. Different parts of the same line may have different forms. Figure 2c shows an embodiment in which the part circular lines are defined by dashed lines. Figure 2d shows an embodiment in which the circular lines are defined by a dot-dash' line. Figure 2e shows an embodiment in which the part circular lines are defined by crosses.

Figure 2f shows an embodiment in which adjacent part circular lines are defined by different types of pattern elements - solid line, dashed line, dotted line. In this embodiment, the fact that the adjacent lines are formed from different pattern elements helps to distinguish between the lines. Each set of lines is therefore made up of sub-sets, each sub-set comprising the lines of the same pattern elements. The difference in radius between the nearest lines on one sub-set is clearly greater than the differences in radius between adjacent lines.

When the pattern is analysed by the pen, the pen analyses the imaged area of the pattern to identify which sub-set of lines each imaged line is part of and to measure the radius of each line. It then use a table of line radii, which identifies nominal radii for all the lines in each sub- set, to identify possible radii for lines within that sub-set and selects the radius closest to the measured radius. This selected radius is then used for position determination. This can be useful when the lines are very close together or when their radii are very similar e.g. near the lower corners of a document furthest from the reference points.

Figure 10 shows further alternative types of pattern element. Figures lOa to lOe show pattern elements which can be formed on a low resolution, dot type' printer. The different shapes 1001, 1002, 1003, 1004, 1005 can be used to identify and distinguish between different lines or line parts.

In a further embodiment, referring to Figure 9, a document 900 has a first concentric set 902 of lines and a second concentric set 904 centred on first 906 and second 908 reference points respectively. Both the first 906 and second 908 reference points are on the document 900 at positions spaced from its edges and corners.

The resulting pattern of lines does not uniquely identify each position on the document because the line pattern is repeated in diagonally opposite quarters 910, 912, 914, 916 of the document. For example, if there is no means for distinguishing between quadrants, the captured images A (Figure 9) and B will be indistinguishable - as will images C and D, since the pen could simply be turned through 1800 to provide the corresponding image.

Therefore the pattern lines are printing using different pattern elements in each of the four quarters 910, 912, 914, 916, in this case using different elements from Figure 10.

When the pen is moved over the document it is arranged to analyse the shape of the pattern elements making up the lines to determine which quarter of the document it is in, and then to determine its position within that quarter by determining its distance from the two reference points 906, 908. It will be appreciated that there are other ways of distinguishing between different areas of the document in which the part circles would not uniquely identify position if they are all formed from similar pattern elements. For example the two sets of lines could be defined using a different type of pattern element for each set.

Alternatively, different pattern elements would be used to define different quadrants or halves of each set of part circles. The only requirement is that no two areas of the pattern, equal in size to the area imaged by the pen or larger, are identical or rotationally symmetrical.

Other methods of distinguishing between different lines or different parts of each line include using different thicknesses of solid line, or different colours of ink.

Claims

1. A product having a data encoding pattern thereon, the pattern comprising a first set of pattern elements defining a first set of part circles centred on a first reference point and a second set of pattern elements defining a second set of part circles centred on a second reference point.

2. A product according to Claim 1 wherein different types of pattern element are used in different parts of the document.

3. A product according to Claim 1 or Claim 2, wherein different types of pattern elements are used to define different portions of one of the part circles.

4. A product according to Claim 1 or Claim 2 wherein different types of pattern elements are used to define different part circles within the set.

5. A product according to Claim 4 wherein the different part circles are adjacent part circles in the same set.

6. A product according to Claim 4 wherein the different part circles are in different sets.

7. A product according to Claim 1 wherein at least some of the part circles are each defined by a plurality of discrete pattern elements.

8. A product according to any preceding claim, wherein the or each part circle comprises a quadrant or less than a quadrant.

9. A product according to any preceding claim which has corners, in which each reference point is provided at a respective one of the corners.

10. A method of generating a data encoding pattern for application to a product, the method comprising the steps of: defining a first set of concentric part circles centred on a first reference point; defining a second set of concentric part circles centred on a second reference point, and defining positions of pattern elements relative to the part circles.

11. A method according to Claim 10, wherein a part circle is defined by its centre and radius.

12. A method according to Claim 10 or Claim 11, wherein the position of each pattern element is defined on its respective part circle.

13. A method according to any of Claims 10 to 12 further comprising defining the shape of each pattern element.

14. A method according to any of Claims 10 to 13, wherein different types of pattern element are used to distinguish between different areas of the document.

15. A method of reading data from a pattern on a product comprising: imaging an area of the pattern; defining within the imaged area a part of a line from a first set of part circles centred on a first reference point and a part of a line from a second set of part circles centred on a second reference point; and identifying data associated with the line parts.

16. A method according to Claim 15, wherein the data is positional data indicating a position on the product.

17. A method according to Claim 16 wherein data associated with each line part is identified by mapping at least three points thereon, determining the radius of the line part and thereby determining a distance from the reference point associated with each line part and determining the location of the imaged area on the product.

18. A method according to any of Claims 15 to 17, wherein one of the lines is made up of different types of pattern elements and identification of these different types is used to distinguish between different portions of the line.

19. A method according to any of Claims 15 to 18 wherein adjacent lines in one set are defined by different types of pattern element, and identification of the element type is used to distinguish between the adjacent lines.

20. A system for reading data from a pattern on a product, the system comprising imaging means arranged to image an area of the product, and processing means arranged to: identify within the imaged area a part of a line from a first set of part circles centred on a first reference point and a part of a line from a second set of part circles centred on a second reference point; and identify data associated with the line parts.

21. A system according to Claim 20 arranged to carry out the method of any of Claims 15 to 19.

22. A data carrier carrying data arranged to cause a computer system to operate as a system according to, or to perform the method of, any of Claims 10 to 21.

23. A product, method, system or data carrier data substantially as hereinbefore described with reference to any one or more of the accompanying drawings.