IES20110196A2 - Improvements in and relating to a sheet orientation detection system - Google Patents

Abstract

The present invention relates to a sheet orientation detection system. In particular, it relates to a sheet orientation detection system for detecting the orientation of a sheet on a substantially flat surface, the system comprising a sheet-receiving tablet having substantially flat sheet-receiving surface and a sensing means directed to the underside thereof, the sensing means being adapted to provide a sensor output; a complimentary sheet having a working side and an idle side; and processing means for processing the sensor output into an orientation output. The system of the invention allows the user to interact with the sheet while the sheet is present on sheet-receiving surface. Incorporation of a digitizer into the system of the invention allows the invention to capture a user's intended message. The invention further relates to an electronic voting system using the sheet orientation detection system. <Figure 1>

Description

The present invention relates to a sheet orientation detection system. In particular, it relates to a sheet orientation detection system for detecting the orientation of a sheet on a substantially flat surface, the system comprising a sheet-receiving tablet having a substantially flat sheet-receiving surface and a sensing means directed to the underside thereof, the sensing means being adapted to provide a sensor output; a complimentary 10 sheet having a working side and an idle side; and processing means for processing the sensor output into an orientation output.

As technology develops, there Is a significant drive to automate tasks that were previously carried out manually. This automation leads in theory to faster results, more 15 accurate results and reduced costs, as the workforce required Is reduced or eliminated.

One of the main barriers in these developments is the area of user interface and data capture. Users are unwilling to greatly adjust their habits in order to allow a system to work better for that system's provider. Therefore, it is preferable to develop a system where a user’s experience is not greatly altered. An example of a technology developed 20 with this in mind is hand-writing recognition systems. In this way, hand-written data may be gathered automatically and then stored electronically for subsequent processing, analysis and retrieval. Prior to the development of hand-writing recognition systems, such data would need to have been read by a human and then manually entered into a computer.

Currently, there are a multitude of devices on the market for signature capture, handwriting recognition and electronic note taking. These devices are useful for capturing the data inscribed by a user on a sheet of paper or the like. However, that captured data does not always comprise all of the information that that data was intended to convey. For example, if the piece of paper was a form of some sort, then the data entered by the user was likely a set of answers to questions posed on the form. In this case, the information, or intended message of the user, contained on the filled-in piece of paper comprises the sets of questions and the accompanying answers as entered by the user. In most cases, for electronic analysis of the information content, this /£ 110196 -2will boil down to the sets of answers and the locations of those answer, as the questions will be known and It is not necessary to extract this Information.

One way to extract information as to the location of a user’s markings on a sheet of paper or the like is to define the location of the piece of paper and define the locations on the sheet of paper where the user may enter data. In this way, there are only specify areas where data must be collected from and the location of those areas is fixed and known. Defining the locations for marking on the sheet of paper is simply done by providing user-guidance on the form or sheet in question. Defining the location of the sheet of paper involves the use or mechanical registration devices such as pins or the like. However, the user is often unwilling to engage with such a system as it requires extra effort from him, and even if willing, is not guaranteed to not succeed.

Other known systems for capturing user data from defined areas of a sheets include systems where the piece of paper is scanned after is has been completed by the user. Such systems require that the form be placed in the correct general location prior to scanning, either on the screen of a flat-bed scanner unit or in the document feed system of a larger scanner apparatus. Some such systems comprise a mechanism to correct their analysis based on the deviation of the scanned image from the ideal. The mechanism comprises an orientation marker, such as a cross-hair image or bulls eye image printed on the document such that they are included in the scanned image of the document. In this way, the image processing has defined straight-lines or the like in the image to use as a reference mark. Through image processing, the image may then be adjusted so that the alignment of the page is correct, by reference to the orientation markers. However, in general only a small level of corrections are possible, for example less than 45° from the desired alignment. Furthermore, by their very nature, such systems do not allow the user’s data to be captured as it is entered.

Throughout the specification, the term sheet will be understood to refer to any material that may be fashioned into a sheet, may bear printed matter, and may be marked using a writing device. It may include paper, card, cardboard, plastic and other such substances.

IE 1 1 ο 1 g g -3Throughout the specification, the orientation of a sheet will be understood to refer to the degree of rotation of that sheet about an axis extending orthogonally from the main surface of the sheet.

It is an object therefore of the present invention to provide a sheet orientation detection system that overcomes at least some of the above-mentioned problems.

Statements of invention According to the invention there is provided a sheet orientation detection system for detecting the orientation of a sheet on a substantially flat surface, the system comprising a sheet-receiving tablet having a substantially flat sheet-receiving surface and a sensing means directed to the underside thereof, the sensing means being adapted to provide a sensor output; a complimentary sheet having a working side and an idle side; and 15 processing means for processing the sensor output into an orientation output, characterised in that the sheet comprises a 360° orientation marker in a predetermined location on the sheet, the 360° orientation marker being adapted to interact with the sensing means to modify the sensor output; and the working side of the sheet is accessible by the user while the system is in use.

In this way, a user may place a sheet according to the invention on the sheet-receiving surface in a manner that is natural and comfortable to him and proceed to write thereon as required. The sheet orientation detection system calculates the orientation of the sheet regardless of what position the sheet has been placed by the user, and is not 25 limited to correcting minor off-sets. The system sheet orientation detection system calculates the orientation while the user is interacting with the sheet. The system is essentially transparent to the user, as the only change to which he must adapt is using the receiving surface instead of a standard tabletop or the like. This has the further advantage that there is very little scope for user error. The sheet orientation detection 30 system of the invention may be used as part of a game whereby a user scores points for placing a sheet, for example a game card, at the correct orientation on the sheetreceiving surface, either as a measure of skill or by chance. -41 1 ο 19 β In one embodiment of the invention there is provided a sheet orientation detection system in which the sensing means comprises a sensing array. A sensing array is a useful form of sensing means as it is quite robust and can be conveniently accommodated in the sheet-receiving tablet. Ideally, the sensing array will extend substantially fully under the sheet-receiving surface and will be directed upwards at the underside thereof.

In another embodiment of the invention there is provided a sheet orientation detection system in which the sensing array comprises an optical sensing array. Such optical technology is again robust and components may be sourced conveniently and inexpensively.

In a further embodiment of the invention there is provided a sheet orientation detection system in which the optical sensing array comprises an array of Light Emitting Diodes (LEDs) and photodiodes. In this way, light emitted by the LEDs is reflected and sensed by the photodiodes.

In an alternative embodiment of the invention there is provided a sheet orientation detection system in which the optical sensing array comprises a plurality of cells, each cell comprising an LED surrounded by a plurality of photodiodes. In this way, it is ensured that each photodiode is sufficiently close to a light source to ensure that it can receive enough light to allow it to operate successfully as a detector.

In one embodiment of the invention there is provided a sheet orientation detection system in which one or more of the photodiodes are lensed photodiodes. In this way, the accuracy of the photodiode as a detector is increased.

In another embodiment of the invention there is provided a sheet orientation detection system in which the optical sensing array is an Infrared (IR) optical sensing array. The use of IR is safe, invisible to the user and so not distracting, and suitable components are readily obtainable.

In a further embodiment of the invention there is provided a sheet orientation detection system in which the optical sensing array operates at a wavelength of approximately IE 110 196 -5880nm. This is particularly useful as certain printing toners have high absorption at this wavelength, allowing for printed markers. Additionally, suitable components for working at this wavelength are readily available.

In an alternative embodiment of the invention there is provided a sheet orientation detection system in which the sheet-receiving tablet comprises an IR filter membrane. Preferably, the IR filter membrane has a pass band at 880nm. This allows wavelengths around 880nm to pass through and blocks visible light. In this way, the sensitivity of the system to room lighting is reduced, and the visual appearance of the system is improved 10 as the sensing array itself is not visible to the user as he engages with the sheetreceiving surface.

In another embodiment of the invention there is provided a sheet orientation detection system in which the 360° orientation marker comprises a marker printed on the sheet.

This is a particularly convenient way of incorporating the 360° orientation marker into the sheet, and works well with the chosen wavelength of 880nm.

In a further embodiment of the invention there Is provided a sheet orientation detection system in which the 360° orientation marker comprises a marker printed on the idle side 20 of the sheet This is particularly useful as it is the idle side of the sheet that will be in contact with the sheet-receiving surface and thus facing the sensing means. It will be understood that the idle side of the sheet refers to the side not intended for user input In a double sided sheet, each side may be the idle side at some point and the working side at another point, and therefore each side may comprise a 360° orientation marker.

In an alternative embodiment of the invention there is provided a sheet orientation detection system in which the 360° orientation marker is printed in ink having a high absorption of IR radiation. Preferably, the IR radiation has a wavelength of approximately 880nm. In this way, the marker will absorb the IR emitted by the LEDs, and the 30 absence of reflected light in the area of the marker will be detected by the IR photodiodes.

In another embodiment of the invention there is provided a sheet orientation detection system in which the 360° orientation marker comprises a pattern comprising an #£ 110 19 6 -6arrangement of similar elements such that the pattern does not repeat as the pattern is rotated. This facilitates identifying the orientation of the pattern In a further embodiment of the Invention there is provided a sheet orientation detection system in which the 360° orientation marker comprises a pattern comprising an arrangement of similar elements such that the 2D cross-correlation of the pattern and a copy of the pattern rotated by 90°, 180° and 360 thereof is low. Preferably, the 2D crosscorrelation of the pattern and a copy of the pattern rotated by 90°, 180° and 360 thereof is less than or equal to 50% of the 2D auto-correlation of the pattern. The crosscorrelation measures the similarity between the detected pattern and original pattern in a set of orientations.

In one embodiment of the invention there is provided a sheet orientation detection system in which the similar elements are rectangles. Rectangles, preferably in the form of squares, are a particularly convenient element to implement In another embodiment of the invention there is provided a sheet orientation detection system in which the pattern comprises a mark-space matrix. A mark-space matrix is a convenient way to implement the pattern by providing a binary pattern, the analysis therefore is simplified. Furthermore, the mark-space matrix provides a high-contrast pattern facilitating increased accuracy in the analysis of the pattern.

In a further embodiment of the invention there is provided a sheet orientation detection system in which the matrix is an 8x8 matrix. The size of the matrix in the pattern must be chosen such that the computation load is not too high, while still providing a low sensitivity to false positive cross-correlation results.

In an alternative embodiment of the invention there is provided a sheet orientation detection system in which the matrix is a 6x6 matrix. A 6x6 matrix will also provide a low computational load with sufficiently sensitivity in the results. Similarly, a 4x4 matrix may also be used if it is desired to reduce the computational loads, for example for a mobile device. In the case of the 8x8 and 6x6 matrices, the 2D cross-correlation of the pattern and a copy of the pattern rotated by 90°, 180° and 360 thereof is less than 50% of the 2D auto-correlation of the pattern. In the case of the 4x4 matrix, the 2D cross-correlation IE 110 196 -7of the pattern and a copy of the pattern rotated by 90°, 180° and 360 thereof is equal to 50% of the 2D auto-correlation of the pattern.

In one embodiment of the Invention there is provided a sheet orientation detection I system in which the sensing array comprises an inductive sensing array. An inductive sensing array is a robust sensing means that may be efficiently implemented.

In another embodiment of the invention there Is provided a sheet orientation detection system in which the inductive sensing array comprises an oscillator circuit connected to 10 an array of coils by a multiplexor. In this way, the frequency of the oscillator circuit is in I part determined by the inductance of the coil, therefore by providing the complimentary sheet with a marker that affects a change in the inductance of the coil, a change in the frequency of the oscillator circuit is induced, providing a detectable interaction between the marker and sensing means.

I In a further embodiment of the invention there is provided a sheet orientation detection system in which the diameter of the coils is in the range 5.5 mm to 9.5 mm. Preferably the diameter of the coils is In the range 6.5 mm to 8.5 mm, and even more preferably the diameter of the coils is in the range 7.2 mm to 8 mm. Ideally, the diameter of the coils is 7.8 mm. The maximum distance between a coil and the suitable marker that gives a measurable change in oscillator frequency is called the range of sensitivity or read range. Range of sensitivity increases with coil diameter. The choice of coil diameter represents a trade-off between the range of sensitivity and array resolution. Coils of diameter 7.8 mm provide a useful read range.

In another embodiment of the invention there is provided a sheet orientation detection system in which the oscillator circuit is connected to a frequency monitoring device. In this way, the change in frequency due to the presence of the marker on the sheet may be detected and processed to provide the orientation output. The frequency monitoring device may comprise a frequency to voltage converter, frequency counter or other similar device.

In a further embodiment of the invention there is provided a sheet orientation detection system in which the inductance of each coil is in the range 50 μΗ to 150 μΗ. Preferably -8Λ J 10196 the inductance of each coil is in 100 pH. This inductance value provides a diameter suitable to provide a usable range of sensitivity and to provide oscillator frequencies that were conveniently measurable. Furthermore, inductors of this value are readily available.

In one embodiment of the invention there is provided a sheet orientation detection system in which the array comprises an array of 42 x 32 coils. Such an array provides a useful and convenient working area and suitable resolution.

In another embodiment of the invention there is provided a sheet orientation detection system in which the 360° orientation marker comprises a metallic member. Such a metallic member interacts well with inductive sensing array, inducing a suitable change of inductance in the coils of the array.

In a further embodiment of the invention there is provided a sheet orientation detection system in which the maximum relative permeability of the metallic member is in the range 70,000 to 100,000. This is a particularly effective range, allowing efficient and accurate operation of the system of the invention.

In an alternative embodiment of the invention there is provided a sheet orientation detection system in which the metallic member comprises a nanocrystalline magnetic shielding alloy. In this way, the high permeability of the alloy allows for useful deviation results, even when very thin layers of the alloy are used.

In one embodiment of the invention there is provided a sheet orientation detection system in which the metallic member comprises a nanocrystalline magnetic shielding alloy sandwiched between layers of clear Polyethylene terephthalate (PET). This is a particularly effective composition of the marker as it combines high permeability of the alloy with the robustness of the PET.

In another embodiment of the invention there is provided a sheet orientation detection system in which the metallic member comprises mu-metal. Such a metal provides the effective magnetic shielding property required to influence the inductive array.

IE 110196 -9ln a further embodiment of the invention there is provided a sheet orientation detection system in which the 360° orientation marker comprises a pair of strips of high permeability metal arranged in a pattern that does not repeat as the pattern is rotated. Such a metal provides the effective magnetic shielding property required to influence the Inductive array, and the pair of strips and the pattern they form provide for identification of the location of the sheet based on the orientation of the strips on the sheet. The array and associated processing devices can Identify the co-ordinates of least two points on each strip, and from those points identify the slope of each strip and hence the orientation of the sheet.

In an alternative embodiment of the invention there is provided a sheet orientation detection system in which at least one of the strips is parallel to one edge of the sheet This is useful way of providing orientation information for the sheet as the orientation of that strip corresponds substantially exactly to the orientation of the sheet.

In a further embodiment of the invention there is provided a sheet orientation detection system in which the pair of strips are orthogonal to each other and each parallel to an edge of the sheet. Again, this is useful way of providing orientation information.

In one embodiment of the invention there is provided a sheet orientation detection system in which the pair of strips intersect each other. In this way, the detection of the point of intersection, by calculating the intersection of lines representing each strip, from slope and known co-ordinates, provides enough information to accurately identify a known position on the paper form. Using that known position, it is then possible to combine that known position with the identified slope of one of the strips to calculate the position of the four corners of the ballot paper.

In a further embodiment of the invention there is provided a sheet orientation detection system in which the pair of strips form a T-shape. A T-shape is a particularly useful configuration of the pair of strips, providing a non-repeating pattern, an intersection of the strips and allowing for each strip to be parallel to one edge of the sheet.

In one embodiment of the invention there is provided a sheet orientation detection system in which the width of the strip is in the range 10 mm to 20 mm. Preferably the 110196 -ίοwidth of the strip is substantially 15 mm. The width of the strip is chosen relative to the I diameter of the inductive coils. Preferably, the width of the marker strip is twice the diameter of the inductive coils. Strips narrower than this value give a reduced read range.

In one embodiment of the invention there is provided a sheet orientation detection system in which the 360° orientation marker comprises a series of spaced apart metallic strip portions. In this way, different marker portions can be used to identify specific portions of the sheet.

In another embodiment of the invention there is provided a sheet orientation detection I system in which sheet comprises a unique identifier. This is useful in many applications of the sheet orientation detection system for example electronic voting, a lottery slip or the like, allowing control, tracking authentication and/or audit of a particular sheet by way of the unique identifier. Such a unique identifier may only need to be unique with a subset of sheets, allowing for the repetition of unique identifiers, for example, in different I locations or on different days.

In a further embodiment of the invention there is provided a sheet orientation detection 1 system in which the unique identifier comprises an RFID tag. RFID technology is a very convenient method of providing a unique identifier.

In an alternative embodiment of the invention there is provided a sheet orientation detection system in which the unique identifier is comprised within the 360° orientation marker. This is a particularly useful construction of 360° orientation marker.

In one embodiment of the invention there is provided a sheet orientation detection system further comprising an activator and the sheet comprises a complimentary trigger for triggering the activator. In this way, the sheet-receiving tablet may be in a stand-by mode while not required to be in use, but is activated into a fully operative once the activator is triggered. Placing the trigger for the activator in the sheet is extremely efficient and convenient, requiring no external hardware such as switches or the like, and is transparent to the user.

I IE 1 1 0 1 9 6 -11 In another embodiment of the invention there is provided a sheet orientation detection system in which the activator comprises an RFID reader and the trigger comprises an RFID tag. An RFID system of this nature is particularly convenient for use with the system of the invention.

In one embodiment of the invention there is provided a sheet orientation detection system further comprising a digitizer for data capture, wherein the digitizer provides the sheet-receiving surface. In this way, the location and content of the user’s data may be captured as the user is writing. The sheet orientation detection system provides the orientation of the marker; the combination of the marker orientation and the location of the marker on the sheet, provides the location of the sheet; and the digitizer (potentially in combination with a hand-writing recognition system) provides the user’s data. The data and location may then be combined to deduce the user’s intended message. In this way, the sheet orientation detection system has uses in electronic voting and other areas where it is desirable or useful to capture handwritten data from a user quickly and accurately, for example where a user is completing a betting slip, completing a lottery ticket or the like.

In another embodiment of the invention there is provided a sheet orientation detection system further comprising a hand-writing recognition system for data capture. In this way, the system may capture a user’s intended message when the message comprises hand-written text. This is useful if the message to be captured cannot be conveyed as a simple tick or the like and letters and/or numbers are required.

In a further embodiment of the invention there is provided a sheet orientation detection system further comprising message processing means adapted to combine the orientation output with the captured data to form a message. In this way, the sheet orientation detection system can capture the user’s intended message.

In an alternative embodiment of the invention there is provided a sheet orientation detection system adapted to generate an electronic record of the message. In this way, the message can be stored for future reference. This may be useful is many applications such as electronic voting, electronic form filling and the like. -12IE 11 ο 1 ® ® In one embodiment of the Invention there is provided a sheet orientation detection system adapted to transmit the message to a remote device. In this way, the message may be shared with a chosen entity, for example a form issuer or a vote count centre.

In another embodiment of the invention there is provided a sheet orientation detection system further comprising a display adapted to display the message. In this way, the user can verify the captured message as that which they intended to convey or may share it with those around. In an electronic voting example, the display would be in the polling booth so that the voter can check that his vote as recorded by the system is correct. In an alternative situation, the user may wish to display his message publicly using the display.

According to the invention there is further provided an electronic voting system comprising the sheet orientation detection system when adapted to record and/or transmit or display the message, further comprising a ballot box having a ballot receiving slot for receiving ballots and a vote processing computer, the ballot box comprising a ballot pox processor adapted to communicate with the vote processing computer. Such an electronic voting system would overcome many of the disadvantages of known electronic voting systems. Firstly, the user’s voting experience does not change greatly, he still enters a polling booth, places his ballot paper on a writing surface and fills in his voting preferences, and finally places the ballot paper in a ballot box. The voter is not faced with new technology that may appear daunting nor is he expected to learn new skills to complete his vote. Additionally, the voting process does not take significantly longer than the traditional voting process. This greatly encourages voter uptake of the new system. Secondly an electronic record of the voter’s intended message - that is, his vote - may be recorded and/or transmitted to a vote counting unit almost immediately, allowing for fast results from the election in question. Thirdly, the concept of a “Voter Verifiable Paper Audit Trail” (WPAT) has become very important in electronic voting. In the electronic voting system of the invention, the user’s original paper ballot provides a WPAT. This original ballot WPAT is extremely trustworthy for the user as he has generated it himself. Furthermore, the original ballot WPAT is trustworthy from an electronic system point of view as it cannot be altered electronically, unlike some previously proposed WPATs. Finally, a major advantage of the electronic voting system of the invention is that the electronic record of the vote and the paper record are -13generated substantially simultaneously and, as they result from a single set of user actions, are essentially guaranteed to be identical.

In a further embodiment of the invention there is provided an electronic voting system in which the ballot pox processor comprises a RFID reader having an RFID antenna, the RFID antenna forming a loop surrounding the ballot receiving slot, and the sheet is a ballot and comprises an RFID tag. Use of an RFID system within the electronic voting system has a number of advantages associated therewith. Firstly, by combining a ballot having an RFID tag and ballot receiving slot surround by a RFID antenna, a ballot counting apparatus may be provided. A signal will be generated every time a ballot passes through the ballot receiving slot. If the ballot’s RFID tag comprises some form of identifier, the RFID system may provide for discounting e-ballots whose equivalent paper ballot was not deposited in the ballot box. For example, if a voter cast a vote in the polling booth but then left the polling station with the ballot paper, an electronic vote record would have been generated for that ballot paper, but no record of the ballot paper entering the ballot box would have been generated, therefore confirming that the vote was not completed and should not be counted. Furthermore, a final tally of ballots in the ballot box is provided. If the RFID tally does not match the actual tally, this flags a potential error or tampering event. In a situation where the ballot receiving slot is be fitted with further detection means that are simply activated by a sheet passing therethrough, then the RFID system would allow for ballot authentication, as an alert would be generated if a sheet passed through the ballot receiving slot and did not trigger both the further detection means and RFID reader.

According to another aspect of the invention there is provided a method for detecting the orientation of a sheet on a substantially flat surface, in a system comprising a sheetreceiving tablet having a sheet-receiving surface and comprising a sensing means directed to the sheet-receiving surface; a sheet comprising a 360° orientation marker in a predetermined location on the sheet, the 360° orientation marker being adapted to interact with the sensing means to produce a sensor output; and processing means, the steps of the method comprising: receiving a sheet on the sheet-receiving surface, the sensing means Interacting with the 360° orientation marker and generating a sensor output; the processing means calculating an orientation output of the sheet based on the sensor output.

IE -j 1 ο 1 96 -14ln this way, the orientation of a sheet on a sheet-receiving surface may be detected automatically and quickly. The user is provided with a very simple way of interact with the system, thereby reducing or eliminating user errors in the system and overcoming the problem of user reluctance to engage with new technology for an existing task.

In another embodiment of the invention there is provided a method in which the step of the sensing means interacting with the 360° orientation marker and generating a sensor output comprises the sensing means emitting a signal; the 360° orientation marker altering the signal in a manner determined by its orientation; the sensing means detecting the altered signal.

According to the invention there is provided a sheet for use in a sheet orientation detection system, the sheet comprising a 360° orientation marker in a predetermined location on the sheet, the 360° orientation marker being adapted to Interact with a complimentary sensing means so as to generate or modify an output of the sensing means, the 360° orientation marker comprising a pattern that does not repeat as it is rotated.

In one embodiment of the invention there is provided a sheet in which the 360° orientation marker comprises a marker printed on the sheet.

In another embodiment of the invention there is provided a sheet in which the 360° orientation marker is printed in ink having a high reflectivity to a specific band of electromagnetic radiation.

In a further embodiment of the invention there is provided a sheet in which the 360° orientation marker is printed in ink having a high reflectivity to Infrared.

In an alternative embodiment of the invention there is provided a sheet in which the 360° orientation marker is printed in ink having a high reflectivity to radiation of approximately 880nm wavelength.

IE 1 1 0 1 9 6 -15In one embodiment of the invention there is provided a sheet in which the 360° orientation marker comprises a pattern comprising an arrangement of similar elements such that the pattern does not repeat as the pattern is rotated.

In another embodiment of the invention there is provided a sheet in which the 360° orientation marker comprises a pattern comprising an arrangement of similar elements such that the 2D cross-correlation of the pattern and a copy of the pattern rotated by 90°, 180° and 360 thereof is low.

In a further embodiment of the invention there is provided a sheet in which the 360° orientation marker comprises a pattern comprising an arrangement of similar elements such that the 2D cross-correlation of the pattern and a copy of the pattern rotated by 90°, 180° and 360 thereof is less than 50% of the 2D auto-correlation of the pattern.

In an alternative embodiment of the invention there is provided a sheet in which the similar elements are rectangles.

In one embodiment of the Invention there is provided a sheet in which the pattern comprises a mark-space matrix.

In another embodiment of the invention there Is provided a sheet in which the matrix is an 8x8 matrix.

In a further embodiment of the invention there is provided a sheet in which the matrix is a 6x6 matrix.

In an alternative embodiment of the invention there is provided a sheet in which the 360° orientation marker comprises a metallic member.

In one embodiment of the invention there is provided a sheet in which the maximum relative permeability of the metallic member is in the range 70,000 to 100,000.

In another embodiment of the invention there is provided a sheet in which the metallic member comprises a nanocrystalline magnetic shielding alloy.

IE 1 1 0 1 9 6 -16In a further embodiment of the invention there is provided a sheet in which the metallic member comprises a nanocrystalline magnetic shielding alloy sandwiched between layers of clear Polyethylene terephthalate (PET).

In an alternative embodiment of the invention there is provided a sheet in which the metallic member comprises mu-metal.

In one embodiment of the invention there is provided a sheet in which the 360° orientation marker comprises a strip of high permeability metal.

In another embodiment of the invention there is provided a sheet in which the strip is parallel to one edge of the sheet.

In a further embodiment of the invention there is provided a sheet in which the width of the strip is in the range 10 mm to 20 mm.

In an alternative embodiment of the invention there is provided a sheet in which the width of the strip is substantially 15 mm.

In one embodiment of the invention there is provided a sheet in which the 360° orientation marker comprises a pair of strips, each orthogonal to each other and each parallel to an edge of the sheet.

In another embodiment of the invention there is provided a sheet in which the pair of strips intersect each other.

In a further embodiment of the invention there is provided a sheet in which the 360° orientation marker comprises a series of spaced apart metallic strip portions.

In an alternative embodiment of the invention there is provided a sheet in which the sheet comprises a unique identifier. -17|£ 11 0 1 9 6 In one embodiment of the invention there is provided a sheet in which the unique identifier comprises an RFID tag.

In another embodiment of the invention there is provided a sheet in which the unique identifier is comprised within the 360° orientation marker.

In a further embodiment of the invention there is provided a sheet in which the sheet comprises a trigger for activating the complimentary sensing means.

In an alternative embodiment of the invention there is provided a sheet in which the trigger comprises an RFID tag.

Detailed description of the Invention The invention will now be more clearly understood from the following description of an embodiment thereof given by way of example only with reference to the accompanying drawings in which:Fig. 1 is a perspective view of the sheet orientation detection system of the invention; Fig. 2 is a side cross-section of the sheet orientation detection system along the line A-A in Fig. 1, with the sheet lying on the sheet-receiving tablet; Fig. 3 is a side cross-section of an alternative embodiment of sheet orientation detection system, with the sheet lying on the sheet-receiving tablet; Fig. 4 is a diagrammatic representation of an electronic voting system according to the invention; Fig. 5(a) is a top view of an inductive sheet orientation detection system according to the invention; IE 110 19 6 -18Fig. 5(b) is a cutaway top view of the inductive sheet orientation detection system shown in Fig. 5(a); Fig. 5(c) is a block diagram of the processing modules used in the inductive sheet orientation detection system; Fig. 6 is a cross-section view of a portion of the inductive sensor array used in the inductive sheet orientation detection system of the invention; Fig. 7 is a top view of a portion of the inductive sensor array; Fig. 8 is a circuit diagram for a portion of the inductive sensor array and its associated multiplexer; Fig. 9 is a circuit diagram of an oscillator used with the inductive sensor array; Fig. 10 is a diagrammatic representation of a sample sheet for use with the system of the invention; Figs. 11(a), (b) and (c) show a number of signal plots from the operation of inductive sheet orientation detection system; Fig. 12 is a graph of percentage deviation in inductance versus marker distance from the inductive sensor array for the inductive sheet orientation detection system; Fig. 13 is a process flow chart of the inductive sheet orientation detection system of the invention; Fig. 14 is a diagrammatic representation of an optical sheet orientation detection system according to the invention; Figs. 15(a), (b), (c), (d), (e), (f), (g), (h) and (i) are sample marker patterns for use with the optical sheet orientation detection system of Fig. 15; IE 1 1 Ο 1 96 -19Fig. 16 is a diagrammatic representation of a side view of a sensing element pattern interacting with an element of the sensor array of Fig. 15; and Fig. 17 is a diagrammatic representation of the sensor array of Fig. 15.

Referring to the drawings, and initially to Fig. 1 thereof, there is shown a sheet orientation detection system indicated generally by the reference numeral 100, comprising a sheet-receiving tablet 102 and a rectangular sheet 104. The sheetreceiving tablet 102 is substantially cuboid in shape, having a height significantly less 10 that its width or breath. This shape allows the sheet-receiving tablet 102 to resemble a board or table-top but is not necessary for operation of the invention. The sheetreceiving tablet 102 comprises a substantially flat sheet-receiving surface 106 forming the top surface of the sheet-receiving tablet 102, and being surrounded by a narrow bezel 108. The sheet-receiving surface is provided by a flat panel 109. The sheet 104 15 comprises a marker 110 at a predetermined location thereon. The sheet orientation detection system 100 further comprises processing means 112. The processing means 112 are shown separately to the sheet-receiving tablet 102, but may be partially or fully incorporated therein. The marker 110 is a 360° orientation marker, whose interaction with the sensing means allows the sheet orientation detection system 100 to detect the 20 orientation of the marker 110 at any orientation on the sheet-receiving surface 106, and hence the orientation of the sheet 104.

Referring now to Fig. 2, in which like parts have been given the same reference numerals as before, there is shown a cross-section of the sheet-receiving tablet 102 25 along the line A-A in Fig. 1, with the sheet 104 lying on the sheet-receiving surface 106 of the sheet-receiving tablet 102. The sheet 104 is lying on the sheet-receiving surface 106 such that the marker is on the idle side of the sheet 104, facing the sheet-receiving surface 106, leaving the working side of the sheet 104 accessible to the user. A sensing means 200 is located under the sheet-receiving surface 106, directed upwardly so that it 30 is directed towards the underside of the sheet-receiving surface 106. The sensing means 200 forms part of the sheet-receiving tablet 102.

In use, the marker 110 on the sheet 104 will interact with sensing means 200 when the sheet 104 is brought sufficiently close to the sheet-receiving surface 106. The interaction IE 1 10 196 -20between the marker 110 and the sensing means 200 will cause the sensing means to alter an existing output therefrom or to generate a new output That output is then processed by the processing means 112 to calculate the orientation of the sheet 104. As the processing means is aware of the location of the marker 110 on the sheet 104, the location of the sheet 104 on the sheet-receiving surface 106 may then be calculated. This orientation and location information may then be stored on the processing means 112. Optionally, the processing means 112 comprises communication means (not shown) allowing the orientation information to be transmitted to a separate device.

Referring now to Fig. 3, in which like parts have been given the same reference numerals as before, there is shown a further embodiment of the sheet orientation detection system of the invention, indicated generally by the reference numeral 300. This version of the sheet orientation detection system 300 is substantially similar to that shown in Figs 1 and 2, except that sheet orientation detection system 300 comprises a digitizer 302 located over the sensing means 200. The digitizer 302 then provides the sheet-receiving surface 106 of the sheet-receiving tablet. The digitizer may comprise processing means (not shown) that are incorporated with the processing means 112 of the sheet orientation detection system or separate therefrom. Either the processing means 112 of the sheet orientation detection system or of the digitizer may comprise message processing means specifically adapted to combine the orientation and location information from the sheet orientation detection system and the data captured by the digitizer. Typically, the message processing means is a software-implemented module.

Furthermore, the sheet orientation detection system 300 may comprise an activator (not shown) that allows the sheet-receiving tablet to transition from a stand-by state, where the sensing means is not active, to an operational state, where the sensing means is active. The activator is controlled by a trigger which may take the form of a standard switch, a beam switch, a proximity detector or the like. Preferably, the trigger is located in the sheet 104. This arrangement may be implemented using an RFID system wherein the sheet 104 comprises a passive RFID tag (not shown) as a trigger for an RFID reader (not shown) having an antenna (not shown) surrounding the sheet-receiving surface 106. Such an RFID tag may be comprised within the 360° orientation marker, or may be separate therefrom. In use, the RFID tag in the sheet 104 would be detected by the IE 1 1 ο 1 9 6 -21 RFID reader when the sheet was placed on the sheet receiving surface 106. The sensing means could then be deactivated when the sheet was removed.

In use, the digitizer 302 can capture graphical information entered on the surface thereof, that is, the sheet-receiving surface 106. Depending on the chosen digitizer, of which many are commercially available, the graphical information may be entered using a specific stylus or a general stylus such as a pen, pencil of the like. The processing means then combines the information received from the digitizer 302 as to the data entered on the sheet receiving surface 106 with the information of the orientation and location of the sheet 104 on the sheet receiving surface 106 to calculate the user’s intended message, that is the data entered in combination with the context provided by its location on the sheet, for example a form. If the data entered is relatively simple, for example ticks or Xs in boxes, then the combination of the orientation information and digitizer 302 output will be sufficiently to interpret the user’s intended message. However, if a more complex message is to be used, for example a message comprising letters and numbers, then the processing means 112 may include a hand-writing recognition system (not shown). In this way, the hand-writing recognition system (not shown) would analyse the input received via the digitizer so as to generate an electronic text representation of the user’s data. This electronic text is then combined with the location and orientation information to deduce the user’s intended message.

Referring now to Fig. 4, in which like parts have been given the same reference numerals as before, there is shown an electronic voting system, indicated generally by the reference numeral 400. The electronic voting system 400 comprises three polling booths 402, 404, 406. The first two polling booths 402, 404 comprise a sheet orientation detection system 300 including separate processing means 112 and an RFID reader (not shown). The third polling booth comprises a sheet orientation detection system 300 which is also connected to a graphical display 408. A ballot paper 409 comprising a sheet according to the present invention is shown on the sheet-receiving surface of each sheet orientation detection system 300. Each ballot paper comprises an identifier (not shown), which may be unique at least within the set of ballot papers associated with a ballot box. The ballot identifier comprises an RFID tag (not shown). The electronic voting system 400 further comprises a ballot box 410 having a ballot receiving slot 412 In a hinged lid 414 thereof; and a ballot pox processor 416. Finally the electronic voting IE 1 1 ο 1 9 6 -22system comprises a vote processing computer 418 in communication with the processing means 112 of each sheet orientation detection system 300 and the ballot box processor 416.

The ballot box processor 416 comprises an RFID reader (not shown) which is connected to an RFID antenna 420 that forms a loop around the inside of the ballot-receiving slot 412.

In use, a polling location may comprise a number of electronic voting systems 400 as illustrated. A user enters a polling booth 402, 404, 406 and casts her vote on the ballot paper 409 in the traditional way by marking the ballot paper with a pen (not shown). The sheet orientation detection system 300 captures the vote. The RFID reader (not shown) of the sheet orientation detection system 300 reads the identifier on the ballot paper and the sheet orientation detection system 300 includes the identifier in the electronic record of the vote, before transmitting it to the vote processing computer 418 for further processing. The user then places her ballot paper 409 in the ballot box 410. The RFID tag identifier on the ballot paper 409 is detected by the RFID antenna 420 as the ballot is deposited and read by the RFID reader. The identifier is then transmitted to the vote processing computer 418 to confirm that a paper ballot has been received for that identifier. This allows a cross-check between electronic records of votes and paper ballots using the identifier.

Voters who use the third polling booth 406 have the option of having their captured vote displayed on the display 408 for confirmation purposes. The display 408 may comprise a touch-screen device allowing the user to confirm their vote using a simple touch. Alternatively, the display 408 may simply be a screen, and the polling booth 406 may comprise alternative data entry means for the user to confirm that the message display represents her intended vote. The electronic voting system 400 may comprise means for the user to indicate that he believes his electronic vote has been recorded incorrectly. It will be understood that all polling booths of the electronic voting system 400 may be similar to the third polling booth 406.

In an alternative embodiment of electronic voting system, each ballot box may be connected to a single polling booth. In this way, the verification of receipt of ballot paper -23IE 110 19 6 can be carried out within the closed system of the ballot box, polling booth and sheet orientation detection system 300. This allows for a well-defined voting session at the booth - the polling booth will not being to accept the next ballot until the previous ballot has been confirmed received by the ballot box.

The vote processing computers 418 within a polling location may be networked together to collect the polling data for the polling location centrally. Each vote processing computer 418 may, additionally or alternatively, be connected to a remote central polling computer. A wide number of secure data collection and transmission systems suitable for use with the electronic voting system of the present invention will be apparent to the person skilled in the art and are outside the scope of this disclosure.

It will be apparent to the person skilled in the art that the above-mentioned electronic voting system will operate successfully without the RFID system for verification and confirmation.

Referring now to Fig. 5(a), in which like parts have been given the same reference numerals as before, there is shown an inductive sheet orientation detection system indicated generally by the reference numeral 500. The inductive sheet orientation detection system 500 comprises a sheet-receiving tablet 502 and a substantially rectangular sheet 504. The sheet-receiving tablet 502 comprises a digitizer which provides a sheet-receiving surface 506. The digitizer is adapted to work with an electronic pen 508. The electronic pen 108 is adapted to visibly mark the sheet 102 as well as interact with the digitizer, and is connected in a wired manner to the sheetreceiving tablet 502. The sheet-receiving tablet 502 further comprises an RFID antenna 510 running around the outer edge thereof. The RFID antenna 510 may be used to detect a passive RFID tag (not shown) on the sheet 504.

The sheet 504 comprises a 360° orientation marker in the form of a metallic member comprising a pair of metal strips 512, 512b. The first metal strip 512a runs adjacent one edge of the sheet 504, while the second metal strip 512b is runs orthogonally to the first metal strip 512a substantially in the middle of the sheet 504. The first metal strip 512a and second metal strip 512b do not intersect. The metal strips 512 comprise a IE 110 19 6 -24nanocrystalline magnetic shielding alloy sandwiched between layers of clear Polyethylene terephthalate (PET) The sheet-receiving tablet 502 further comprises an Inductive sensor array (not shown) located beneath the digitizer. The inductive sheet orientation detection system 500 further comprises a processing means (not shown), which may be located within the sheet-receiving tablet 502 or external thereto.

The detection of the passive RFID tag (not shown) may be used to activate the sensor array to begin identifying the marker on the sheet 504. Additionally, the RFID tag may comprise a unique identifier for the sheet in question, wherein the RFID reader can read and record the unique identifier.

Referring now to Fig. 5(b), in which like parts have been given the same reference numerals as before, there is shown a sheet-receiving tablet 502 wherein a portion of the top surface thereof is not shown so as to illustrate the sensor array 520 thereunder. The sensor array 520 comprises a plurality of sensing elements arranged in an array connected by longitudinal and transverse connections.

Referring now to Fig. 5(c), in which like parts have been given the same reference numerals as before, there is shown a block diagram of the processing means 530 of the sheet-receiving tablet 102. These processing units comprise a Power Supply Unit (PSU) 532; an RFID reader 534; a main processing section 536 comprising a CPU, RAM and a Data Storage Unit; Sensor Array Controlling Logic 538, including multiplexors; and the digitizer control 540.

Referring now to Fig. 6 in which like parts have been given the same reference numerals as before, there is shown a side cross-section view of a portion of the inductive sheet orientation detection system 500, showing a sensing element of the inductive sensor array 520. The sensing elements each comprise an inductor, indicated generally by the reference numeral 602 comprising a coil 604 located between an upper plate 606 and a lower plate 608. The digitizer 610 is located over the inductive sensor array 520. The sheet 504 including one of its metal strips 512a, 512b is shown placed on top of the digitizer 610. The magnetic field 612 generated by the inductor is shown to extend IE 110 19 6 -25through the digitizer 610 and the sheet 504 and its marker 512. In a preferred embodiment, the inductive sensor array 520 comprises 1344 coils arranged in a 42 x 32 array, however other array sizes are possible. The inductors 602 each have an inductance value of 100 μΗ. A Bournes SRD0805 Ferrite DR core is a suitable inductor for use.

Referring now to Fig. 7 in which like parts have been given the same reference numerals as before, there is shown a top view of a portion of the inductive sensor array 520 comprising a plurality of spaced-apart inductors 602 arranged in rows and columns. Each inductor 602 has a radius r, that is the radius of the coil 604 therein, and a read radius R. The spacing between the inductors 602 depends on the diameter of the coils 604. In the current embodiment, the coils 608 are of a maximum diameter of 7.8 mm, and the spacing between the centres of adjacent coils 604 is 9 mm. In this way, each inductor coil corresponds to a pixel in the inductive sensor array 520. The read radius of each inductor 602 extends laterally to cover the distance between each coil and its neighbouring coils, such that the spaces between inductors on the horizontal and vertical axes will be within the read radius of two inductors 602.

Referring to Graph 1 below, there is shown the Frequency to Voltage Output in volts versus the distance of the marker from the coil in millimetres. This graph illustrates the deviation in the frequency caused by the presence of the marker at various distances from the inductive coil. This provides an indication of the read range of the coil. The fiat portion of the graph for the greater distances indicates that at this distance, the deviation caused by the marker is minimal. Therefore the read range in this case is around 4-5 mm.

IE 110 196 Graph 1.

Referring to Graph 2 below, there is shown a plot of percentage inductance deviation versus the distance between the metallic strip and the inductor. From this graph, it can be seen that the percentage deviation begins to be noticeable at a read range of 4mm, that is, when sheet 504 including the marker is 4 mm from the inductive sensor array 520.

Graph 2 Referring now to Fig. 8 in which like parts have been given the same reference numerals as before, there is shown a circuit diagram of a portion of the inductive sensor array 520, comprising twenty eight inductors 602 each connected to an analog multiplexor IC 802.

IE 1 1 0 1 9 6 -27The inductors 602 are connected together and to the multiplexor IC 802 so as to allow each inductor 602 to be accessed individually. The portion of the array has a connection point 804 for connection to be made to an oscillator circuit. The analog multiplexor IC 802 illustrated here is the Analog Devices (RTM) ADG 732.

Referring now to Fig. 9 in which like parts have been given the same reference numerals as before, there is shown a circuit diagram of an oscillator circuit indicated generally by the reference numeral 900. The oscillator circuit 900 comprises a first connection point 902, for engagement with the connection point 804 shown in Fig. 8; and a second connection point 904 for connection to a frequency monitoring device (not shown). The first and second connection points 902, 904 allow the oscillator circuit 900 to be connected to the inductors 602. The oscillator circuit 900 comprises three quad 2-input NAND Schmitt triggers 906 and a pair of capacitors 908 to from a standard LC oscillator, when linked to an inductor 602 in the inductive sensor array 520. It will be understood that the oscillator used within the system of the invention may comprise any standard oscillator and is not limited to that shown here. The oscillator circuit 900 operates within the range of 250 kHz to 350 kHz. Frequencies in this range provide a greater read range. Furthermore, frequency to voltage converters also operate accurately In this range of frequencies.

Referring now to Fig. 10 in which like parts have been given the same reference numerals as before, there is shown a sample sheet 1000 for use with the inductive sensor array 520. The sheet 1000 comprises a passive RFID tag 1002 in the top left corner. The RFID tag comprises a square spiral antenna 1004. The RFID tag 1002 may be affixed to the sheet 1000 or it may be printed thereon in a suitable material. The sheet 1000 further comprises a plurality of preference boxes 1006a, 1006b, 1006c. Each preference box 1006a, 1006b, 1006c has a marker located beside it. Each marker comprises a series of spaced apart metallic strip portions and it is unique within the sheet 1000. The marker 1008 for the first preference box 1006a comprises three metal strips 1008a, 1008b, 1008c. The first strip 1008a is located to the right of the preference box 1006a, and spaced apart therefrom. The second and third strips 1008b, 1008c are located to the left of the preference box 1006a, spaced apart therefrom and from each other. The other preference boxes 1006b, 1006c have similar marker arrangements, with varying strip thickness and relative spacing. The marker area, which may extend from IE 1 10 196 -28one of more sides of the preference box, may be viewed as being divided into equalsized panels 1010, each representing a bit in an identification word for that preference box. In this way, if the panel comprises a metal strip, it can be viewed as representing a 1, while an empty panel represent as 0. Therefore, the marker for preference box 1006a reads 100101 from left to right, the marker for preference box 1006b reads 100111 and the marker for preference box 1006c reads 101101. The system of the invention wiil detect each panel 1010 comprising a metal strip, calculate the location of that strip, and thus be provided with sufficient information to uniquely identify the preference box associated with that strip.

Referring now to Fig. 11, there is shown three plots of signals obtained during operation of the sheet-receiving tablet 502. In plot (a), there is shown the regular oscillation 1202 detected in an inductor 602 while the sheet-receiving tablet 502 is in use. In plot (b), there is shown a modified plot 1204, wherein the frequency of the oscillation has increased in a portion of the plot corresponding to the presence of a marker for that period of time. Plot (c) shows the output 1206 of a frequency to voltage converter (F/V) with plot (b) as an input. The F/V plot 1206 increases in amplitude to correspond to the increase in frequency caused by the presence of the marker.

Referring now to Fig. 12, there is shown a graph of percentage deviation versus distance in millimetres. The graph represents the percentage deviation from the normalised/idle level of the output of the frequency to voltage converter versus distance of the marker from the inductor. From analysis of the inductive sensor array in this manner it is possible to determine the read range above the inductive sensor array at which the presence of a marker will provide a suitable percentage deviation.

Referring now to Fig. 13, there is shown process flow chart for the system of the invention. The inductor array 1402 is connected via the multiplexing stages 1404 to the oscillator 1406, with each inductor 602 in the array connected sequentially. The frequency of oscillation is measured via a frequency to voltage converter 1408 which detects any changes in frequency. Then data acquisition 1010 and analysis 1012 is carried out to determine the orientation and location of the sheet on the inductor array.

IE 110 19 6 -29ln use, when the oscillator circuit 900 is connected sequentially to each of the inductors 602 in turn through the analog multiplexor IC 400, an LC oscillator is formed and an oscillating signal 1202 is generated. The Sensor Array Controlling Logic 538 is responsible for sequencing the coil scan, creating synchronisation pulses and controlling the array scan timing. For an array of 42 x 32 inductors, the time to scan through all the inductors 602 is approximately 200 ms, with the time to scan a single inductor being approximately 1.5 ps. As each inductor 602 effectively forms part of an LC oscillator circuit when connected via the multiplexor to the oscillator circuit 900, the frequency of the oscillation will vary if the magnetic field 612 of the inductor 602 is altered by the presence of a marker 512. The effect of such an alteration in the oscillation frequency is illustrated in Fig. 12(b). The oscillating signal is connected to a frequency monitoring device 1408 which will identify a change in frequency of the oscillation, and preferably convert it to a voltage which may then be converted in a digital value for that pixel, and processed accordingly. In this way, the data provided by the frequency monitoring device 1408 can be used to identify the location of markers 512 in relation to the inductive sensor array 520. Any coil 604 that provides for an alteration in the oscillation frequency is identified to have a marker 512 nearby. The changes in frequency are processed such that a value is recorded for every pixel in the inductive sensor array 520 to allow further processing.

A wide number of marker patterns are suitable for use with the inductive sheet orientation detection system 500 including a simple strip parallel to one side, a pair of parallel strips adjacent the edges of the sheet, a series of broken strips, a pair of intersecting strips, an arrangement of strips providing location information by their position and so on.

The embodiment of the inductive sheet orientation detection system described above uses an absolute frequency measurement relative to zero. In an alternative embodiment, it is possible to use a superheterodyne system. Superheterodyning involves taking an accurately controlled reference frequency and measuring the difference or beat between it and the LC oscillator frequency. This allows small frequency shifts to be measured more accurately. Such an embodiment provides increased sensitivity in the system. Ο11@ 1 96 30 In an alternative embodiment of the inductive sheet orientation detection system, the sensor array comprises a single large inductive coil and an array of pick-up coils. The large coil induces eddy currents in the markers on the sheet and those eddy currents are detected by the array of pick-up coils. Alternatively, each pixel may comprise separate energising and pick-up coils to operate in a similar manner to above In a further embodiment of the inductive sheet orientation detection system, an induction balance system or pulse decay approach may be used to detect the markers..

Referring now to Fig. 14, in which like parts have been given the same reference numerals as before, there is shown a side view of a portion of optical sheet orientation detection system. The optical sheet orientation detection system 1500 comprises a sheet-receiving tablet (not shown) having an optical sensor array indicated generally by the reference numeral 1502. The optical sensor array 1502 is located below a digitizer 109 providing a sheet-receiving surface 106. A sheet 1504 lies on the digitizer 109. The optical sensor array 1502 comprises an arrangement of a plurality of LEDs 1506 and lensed photodiodes 1508.

Referring now to Fig. 15(a), (b), (c), (d), (e), (f), (g), (h) and (i), there are shown a selection of patterns 1602, 1604, 1606, 1606, 1608, 1610, 1612, 1614, 1616, 1618 for use as a 360° orientation marker with the optical sensor array 1200. For references purposes, reference number 1600 will be used to refer to a marker that may comprise any of the patterns shown in Fig. 15, or other patterns according to the invention. The first set of three patterns 1602, 1604, 1606 comprise 8x8 arrays of rectangles. The second set of three patterns 1608, 1610, 1612 comprise 6x6 arrays of rectangles. The third set of three patterns 1614, 1616,1618 comprise 4x4 arrays of rectangles. An 8 x 8 array for the pattern was chosen as a trade-off between the computational power needed and a sensitivity to false positive correlations during processing. The larger the array, the less sensitive the system will be to false positive correlations, however, a larger array also increases the processing power. An 8 x 8 array provides very low false positive rates at a reasonable computational requirement. A6x6or4x4 array may also be used.

IE 110 19® -31Certain rectangles within the pattern are shaded to provide a mark-space matrix in the pattern. In this way, elements within the pattern will have of dissimilar reflectivity. The arrangement of shaded rectangles 1620 to non-shaded rectangles 1622 within the pattern is chosen such that the arrangement does not repeat when it is rotated through 90°, 180° or 270°. Furthermore the 2D cross correlation between the pattern and a copy of the pattern rotated through 90,180 and 270 degrees is low. The low cross correlation was designed heuristically with the goal that the peak in the cross correlation of a pattern and the pattern rotated at 90,180 and 270 degrees should be less than 50% of the peak in the 2D autocorrelation for the 8x8 and 6x6 patterns; and equal to 50% for the 4x4 patterns..

Additionally, the pattern will comprise approximately equal numbers of shaded to nonshaded rectangles. Ideally large areas of shaded or non-shaded rectangles are avoided as this minimises the likelihood of false positive correlation with other arrangements in the image. An exemplary system uses a rectangle size of 4 x 4 pixels = 16 x 16 mm, giving an overall pattern size of 1024 pixels corresponding to 128mm x 128mm.

It will be understood that the optical marker for use with the optical sensor array 1502 may comprise one or more of the patterns of Fig. 16, or a pattern having similar nonrepeating and 2D cross-correlation properties as outlined above.

In use, the marker is printed on the back of the sheet 1504 using standard printer toner. Such ink absorbs Infrared Radiation (IR) of wavelength 880nm. Black rectangles in a pattern printed onto white paper in this manner have a reflectivity at 880nm that is less than 20% of the reflectivity of white, non-printed rectangles. The system does not require such a large difference between the reflectivity of the white and black rectangles in the pattern, however, a large difference does improve the performance of the image processing.

Referring now to Fig. 16, in which like parts have been given the same reference numerals as before, there is shown a diagrammatic representation of the interaction between a lensed photodiode 1508 of the optical sensor array 1502 with the shaded rectangles 1620 and non-shaded rectangles 1622 of the pattern 1600 on a sheet 1504. The lensed photodiode 1508 comprises a lens 1700 to create an acceptance cone 1702 IE 110 196 -32having a half angle of 15°. The diameter of the acceptance cone 1720 where it meets the digitiser 109 is approximately equal to one quarter the width of the pattern elements 1620,1622 in the marker Referring now to Fig. 17, In which like parts have been given the same reference numerals as before, there is shown a diagrammatic representation of the top view of a sheet-receiving tablet, Indicated generally by the reference numeral 1800. The sheetreceiving tablet 1800comprising a sheer-receiving surface. The sheet-receiving tablet 1800 comprises the optical sensor array 1502. The optical sensor array 1502 comprises 94 x 72 components, totalling 6768 positions. This total comprises 768 IR LEDs 1506 and 6000 IR photodiodes 1508 arranged such that each IR LED 1506 is surrounded by eight IR photodiodes 1508. The pattern is interrupted at the edges resulting in the non integer multiple of 768. This layout, in combination with the wide emission half-angle of greater than 150s of the IR LEDs 1506 allows each IR LED 1506 to provide electromagnetic radiation for the eight adjacent IR photodiodes 1508. In an exemplary system, each component is spaced 4mm apart given a total working area of 376mm x 288mm.

For best spatial resolution the acceptance cones on the photodiodes should not overlap. Overlapping would cause blurring of the pattern image. To avoid overlapping the acceptance cones, the distance between the LED integrated lens 1700 and the pattern 1600 should be minimised. In an exemplary system, a distance of 4mm is used.

Each element, either photodiode 1506 or LED 1508, in the optical sensor array 1502 corresponds to a pixel in a bitmap image of the reverse of the sheet placed on the sheetreceiving tablet 1800. However, as the LEDs 1506 do not actually sense light, they are dead pixels. Actual values for these dead pixels are interpolated from neighbouring pixels.

Each rectangle in the pattern 1600 is sized such that it can be spatially resolved by acceptance cone 1702 of a plurality of photodiodes 1508. In an exemplary system, each rectangle is sized such that it is imaged by 14 to 15 photodiodes 1508. -33The sheet-receiving tablet 1800 further comprises an infrared filter sheet 1506 which passes wavelengths around 880nm therethrough and absorbs visible light. This reduces the sensitivity of the system to room lighting as well as improving the visual appearance of the system.

Additionally, the sheet-receiving tablet 1800 comprises a bezel 1804 which encourages the user of the optical sheet orientation detection system 1500 to place the sheet 1504 on the sheet-receiving surface thereof.

In use, the following steps are carried out to identify the pattern and its orientation. Prior to normal operation an initial calibration is performed for each pixel. This comprises placing an all white sheet on the optical sensor array 1502 to record the white value for each pixel and then placing an all black sheet on the optical sensor array 1502 to record the black value. Thereby, a black value and a white value are recorded for each pixel.

During normal operation, a sheet is placed on the sheet-receiving surface of the digitizer 109 above the optical sensor array 1502 such that the pattern 1600 on the reverse of the sheet 1504 is facing the optical sensor array 1502. The individual pixel values, that is, the values for the Intensity of the 880hm light detected by each photodiode are returned 20 from the optical sensor array 1502. Next, the value of each pixel is compared to the calibration values for that pixel and a resulting greyscale value is assigned to the pixel.

Values for missing pixels resulting from the LEDs are interpolated from neighbouring pixels using simple neighbour averaging. The resulting greyscale image is 2D cross correlated with a pattern array where the pattern array consists of copies of the pattern 25 1600 rotated at 10 degree intervals. The maximum gradient of the correlations indicates the location and orientation of the pattern 1600 in the image of the back of the sheet.

Throughout the specification, the term 360° orientation marker will be understood to refer to a marker capable of providing information on the orientation of the marker on its 30 degree of rotation, up to 360°.

While the sensing means of the invention have been described herein as comprising sensing arrays, it will be apparent to the person skilled in the art, the sensing means may comprise a scanning sensing means, for example a laser scanning mean adapted to IE 110 19 6 -34interact the optical markers described herein. Such scanning sensing means necessarily comprise moving parts, that must be maintained in careful alignment and therefore lack the robustness of the scanning array embodiments. Such robustness is felt to be particularly advantageous for the sheet orientation detection system of the invention 5 since the system is designed to be used by untrained users. Robustness of the sheet orientation detection system is particularly important in the sheet orientation detection system when it is to be used in an electronic voting requirement.

It will be understood by the person skilled in the art that the term “digitizer” may refer to 10 an electronic device for automatically capturing handwritten data. The digitizer may require a special pen or it may function using a standard writing implement.

It will be understood by the person skilled in the art that the term metal marker may refer to any marker formed using a substance that provides suitable magnetic properties to 15 ensure its presence interferes with the magnetic field of the inductor in a detectable manner. Example substances include mu-metal, nanocrystalline magnetic shielding alloys and similar such materials.

It will be understood that the read range for an inductive coil sensing element depends 20 on the radius, core type, wire characteristics, wind accuracy, operating parameters and other factors.

It will be understood that the pair of the strips forming the 360° orientation marker for use in the inductive sheet orientation detection system may be formed as a single body 25 comprising at least a pair of strip-like elements.

Throughout the specification, the term-handwriting recognition will be understood to refer to both on-line and off-line hand-writing recognition and Optical Character Recognition. On-line hand-writing recognition would be carried out in conjunction with the digitiser of 30 the system.

Suitable digitizers and accompanying combination digital pens suitable for use with the invention may be obtained from Scriptel Corporation™, Ohio, USA.

IF 1 1 Ο 1 96 _35.

In the specification the terms ‘comprise’, ‘comprises’, ‘comprised’ and ‘comprising’ or any variation thereof and the terms ‘include’, ‘includes’, ‘included’ or ‘including’ or any variation thereof are considered to be totally interchangeable and they should all be afforded the widest possible interpretation.

The invention is not limited to the embodiment herein described, but may be varied in both construction and detail within the terms of the claims.

Claims (5)

Claims

1. A sheet orientation detection system for detecting the orientation of a sheet on a substantially flat surface, the system comprising a sheet-receiving tablet having a substantially flat sheet-receiving surface and a sensing means directed to the underside thereof, the sensing means being adapted to provide a sensor output; a complimentary sheet having a working side and an idle side; and processing means for processing the sensor output into an orientation output, characterised in that the sheet comprises a 360° orientation marker in a predetermined location on the sheet, the 360° orientation marker being adapted to interact with the sensing means to modify the sensor output; and the working side of the sheet is accessible by the user while the system is in use.

2. A sheet orientation detection system as claimed in claim 1 in which the sensing means comprises an optical sensing array.

3. A sheet orientation detection system as claimed in claim 1 in which the sensing means comprises an inductive sensing array.

4. A sheet orientation detection system as claimed In any previous claim further comprising a digitizer for data capture, wherein the digitizer provides the sheetreceiving surface.

5. An electronic voting system comprising the sheet orientation detection system as claimed in any of claims 49 to 54 further comprising a ballot box having a ballot receiving slot for receiving ballots; and a vote processing computer; the ballot box comprising a ballot pox processor adapted to communicate with the vote processing computer.