WO2008048167A1

WO2008048167A1 - Data transfer from multiple electronic pens

Info

Publication number: WO2008048167A1
Application number: PCT/SE2007/000910
Authority: WO
Inventors: Petter Ericson
Original assignee: Anoto Ab
Priority date: 2006-10-17
Filing date: 2007-10-17
Publication date: 2008-04-24

Abstract

A system for collecting pen data comprises a plurality of electronic pens, which are configured to generate pen data by electronically recording pen strokes as they are made on a product surface, a receiving device for collecting pen data from said plurality of electronic pens, and at least one concurrent communication channel for transfer of said pen data from the electronic pens to the receiving device. The number of electronic pens is larger than the number of concurrent communication channels, but the system is set up to allow simultaneous use of all the electronic pens. To this end each electronic pen is configured to intermittently transfer the pen data to the receiving device as it is being generated. The system can for instance be used during examinations for collecting answers in electronic form.

Description

DATA TRANSFER FROM MULTIPLE ELECTRONIC PENS

Cross-reference to related applications

This application claims the benefit of Swedish patent application No. 0602171-1 filed on October 17, 2006, and US provisional patent application No. 60/829,784 filed on October 17, 2006, both of which are hereby incorporated by reference. Field of the Invention

The present invention generally relates to data transfer, and in particular to data transfer between an electronic pen and a receiving device. Background Art

Electronic pens can be used for generation of information that electronically represents handwritten entries on a product surface. One type of electronic pen operates by capturing images of a position code on the product surface. Based upon the images, the pen is capable of electronically recording a sequence of positions (a pen stroke) that corresponds to the pen motion on the product surface. The recorded positions can then be transferred to an external unit for further processing by an application running on the external unit. WO 03/005181 discloses an electronic pen of the above-mentioned type in which the user controls the point of time at which transfer of recorded pen strokes to an external unit should take place. More particularly, the pen buffers all recorded positions until the user marks a specific area on the product surface. Only then is the pen strokes transmitted to the external unit.

WO 00/72230 discloses another electronic pen which more or less in real time transmits every recorded pen stroke to a nearby printer, which relays the pen strokes to a network server for further processing. When the pen is out-of-range of the printer, the pen buffers the pen strokes in internal memory. When the pen once again gets within range of the printer, it transfers any buffered pen strokes to the printer.

In the above-mentioned cases, a single pen communicates with an external unit. However, there could be situations where one would like to collect pen strokes from a large number of pens that are used simultaneously, like in a classroom, a lecture room, or an audience hall, in one common external unit.

The pens could for instance be used during examinations to collect answers from students in electronic form, or during voting for recording votes in electronic form. Neither of the above-mentioned ways of transferring data to the receiving external unit is suitable for this particular situation. In the first case, the pen user may forget to mark the specific area, resulting in that his pen strokes will not be transferred. In the second case, a single receiving external unit may not be sufficient for receiving pen strokes from a large number of simultaneously transmitting pens. If e.g. the Bluetooth standard version 2.0 is used for communication with the external unit, the number of simultaneously transmitting pens would be limited to seven. Summary of the Invention

A first aspect of the invention is a system for collecting pen data, comprising a plurality of electronic pens, which are configured to generate pen data by electronically recording pen strokes as they are made on a product surface, a receiving device for collecting pen data from said plurality of electronic pens, at least one communication channel for transfer of said pen data from the electronic pens to the receiving device, wherein the number of electronic pens are larger than the number of concurrent communication channels and wherein each electronic pen is configured to intermittently transfer the pen data to the receiving device as it is being generated.

By transferring pen data in an intermittent manner to the receiving device a larger number of electronic pens can be used together with a single receiving device. This could be advantageous when information recorded by electronic pens is to be handled in a centralized manner, like electronically recorded examination answers. The user may furthermore use the pen as an ordinary pen without having to take any specific action to transfer the data to the receiving device, because the pen handles the transfer automatically. Also, the intermittent mode of transfer makes it possible to monitor the operational status of the pens.

A second aspect of the invention is a method for generating and transferring an electronic document to a receiving device, comprising generating an electronic document by electronically recording pen strokes while they are being created on a product by an electronic pen, and successively transferring the electronic document from the electronic pen to a receiving device as the electronic document is being generated by intermittently transferring pen data, which comprises pen strokes that have been electronically recorded but not previously transferred, to the receiving unit. A third aspect of the invention is an electronic pen comprising a sensor for electronically recording pen strokes while they are created on a product by the electronic pen, said pen strokes forming an electronic document, and a control unit and a transmitter, which are configured to successively transfer the electronic pen strokes from the electronic pen to a receiving device as the electronic document is being generated by intermittently transferring pen data, which comprises those pen strokes that have been electronically recorded but not previously transferred, to the receiving unit.

A fourth aspect of the invention is a computer program product, directly loadable into the internal memory of an electronic pen, comprising software instructions that, when executed in the electronic pen, perform the method according to the second aspect.

A fifth aspect of the invention is a method for receiving an electronic document from an electronic pen, said method comprising intermittently and successively as the electronic document is generated, receiving file objects in a receiving device, said file objects comprising pen strokes that have been electronically recorded by the electronic pen while they were created on a product surface and that together form the electronic document; and combining the pen strokes of said file objects to form the electronic document by using identifying information that is included in the file objects of said electronic pen.

A sixth aspect of the invention is a receiving device comprising a control unit and a receiver for receiving an electronic document from an electronic pen, wherein said receiver is capable of intermittently and successively as the electronic document is being created by the electronic pen receiving file objects from the electronic pen via a communication channel from the electronic pen to the receiver, said file objects comprising pen strokes that have been electronically recorded by the electronic pen while they were created on a product surface, the control unit being configured to combine the pen strokes of said file objects to form the electronic document by using identifying information that is included in the file objects of said electronic pen.

A seventh aspect of the invention is a computer program product, directly loadable into the internal memory of a processor in a receiving device, comprising software instructions that, when executed in said processor, perform the method according to the fifth aspect.

Other objectives, features, aspects and advantages of the invention will appear from the following detailed disclosure, from the dependent claims as well as from the drawings. Brief Description of the Drawings

Embodiments of the invention will now be described in more detail with reference to the accompanying schematic drawings.

Fig. 1 shows an embodiment of a system where a plurality of electronic pens communicates with a single receiving device. Fig. 2 is a flow diagram and shows an embodiment of a method for transferring data from an electronic pen to a receiving device.

Fig. 3 is a flow diagram and shows an embodiment of a method for receiving pen data. Fig. 4 is a cross-sectional view of one embodiment of an electronic pen. Fig. 5 is a state transition diagram showing communication states and events in an electronic pen.

Detailed Description of a Preferred Embodiment GENERAL INTRODUCTION

Fig. 1 shows an example of a system where a plurality of electronic pens 100 (here three) communicates with a receiving device 135 over a respective communication channel 132.

Typically there is a limitation on the number of concurrent communication channels that can be handled by the receiving device 135. Thus, if the pens 100 were to use the previously known concept of transferring the recorded information to the receiving device more or less in real time as it is generated, only a limited number of pens could be used in the system of Fig. 1. However, by configuring the pens to buffer recorded information and to transmit buffered information intermittently to the receiver, a larger number of pens can be used simultaneously. The pen handles the information transfer without any input from or interaction with the user, so that the user can use the pen as an ordinary pen. Also, the pens transfer information in a recurrent manner so that the operation of the pens can be checked and any malfunction detected and corrected with minimal delay. The waiting periods between transfer attempts may be varied in a random or pseudo-random manner to reduce the risk that more than the available number of communication channels need be used simultaneously. SYSTEM OVERVIEW

The system of Fig. 1 will now be discussed more in detail. Each electronic pen 100 is used by a user 130 to electronically record information which is to be subsequently processed in a centralized manner. The electronic pen may be used in the same manner as an ordinary pen to write on a surface of a product 131, e.g. a paper or other writing base, and the electronically recorded information may represent one or more pen strokes made by the user on the product, e.g. text, drawings, digits, check-box marks, symbols or "clicks" by the pen on the product, in the form of positional data. A collection of pen strokes which belong together, e.g. because they relate to a specific form or paper document or because they have been generated during a specific time period, may be denoted as an electronic document. The electronic pen 100 may typically comprise one or more sensors, such as an optical sensor and/or an accelerometer, for recording absolute or relative positional data or a combination thereof, a control unit for controlling the function of the pen, memory for short term or long term storage of positional data and a transmission interface. The product 131 may or may not be specially formatted to allow for position determination. In the former case, the product may be provided with a position code which codes positions on the product. In the latter case, the pen may for instance record its position by imaging the whole product and determine its position with respect to a corner and an edge of the product, see e.g. WO 2004/077107. As another alternative the product may be used together with other items, e.g. to allow for position determination by triangulation.

The electronic pen 100 generates pen data for transfer to the receiving device 135. The pen data may comprise positional data relating to the position of the pen, such as position coordinates, time stamps indicating when the position coordinates were recorded, and pressure values indicating the pressure applied by the pen on the product when the position coordinates were recorded. In another embodiment the pen data may, in addition to positional data, comprise operational data relating to the operational status of the pen, such as battery level, hardware status, memory usage and/or RF signal strength. In yet another embodiment, the pen data may also comprise free-standing data, which is non-positional data that is not directly related to pen strokes, and/or pen-resident parameters, which may be pre-stored in the memory of the pen to identify a characteristic of the pen itself or of the owner/user of the pen.

Each electronic pen 100 may transmit information to the receiving device 135 via a communication channel 132, which may allow for one-way or two-way, wireless communication with the receiving device 135. The pens 100 are all supposed to be within the range of the communication channels. Generally, the communication channels 132 may be short-range RF links such as

Bluetooth, WLAN₅ ZigBee or WUSB, or other wireless links using e.g. ultra sound or IR communication protocols. In some cases there may be a limitation on the number of concurrent communication channels. This may for instance be the case when the communication link is connection-oriented, like e.g. Bluetooth, so that a connection has to be established before any data can be sent.

The receiving device 135 may comprise at least one receiver for receiving data from the communication channels 132 and a processing unit for processing the received data. In the embodiment of Fig. 1, the receiving device 135 comprises an RF transceiver 134 connected to, or integrated in, a computer 136 with an associated storage device 138. The computer 136 can be any type of computer, such as a server, a desktop computer, a laptop computer or even a palmtop computer, running any suitable operating system, such as Microsoft Windows, Linux, Unix, Mac OS₅ Novell Netware, Windows Pocket PC, Palm OS, etc. Furthermore, the computer 136 may comprise a control unit (not shown), formed by a commercially available microprocessor such as a CPU ("Central Processing Unit"), by a DSP ("Digital Signal Processor") or by some other programmable logical device, such as an FPGA ("Field Programmable Gate Array") or alternatively an ASIC ("Application-Specific Integrated Circuit"), discrete analog and digital components, or some combination of the above. The storage device 138 can be any digital storage with write access, for example hard disk drive, optical storage, flash memory, Random Access Memory (RAM), etc., or a combination of two or more of these memory types. The storage device 138 may be external or internal to the computer 136. In other embodiments, the receiving device may be or may comprise a mobile phone, a

PDA, a network server or other similar device. Also the receiving device may include a plurality of receivers, e.g. a plurality of Bluetooth nodes connected in a network. The receiving device 135 may perform no processing, some processing or all processing of the received data. If the receiving device does not perform all processing, data may be forwarded to or retrieved by another unit 140, e.g. a workstation, for further processing. For that purpose, the receiving device may also be connected to a network 139, which may be a local area network (LAN) such as an Ethernet or Token Ring network, or a wide area network (WAN) such as the Internet. Several systems comprising electronic pens 100, communication channels 132 and a receiving unit 135 may be connected to the work station 140. A system as discussed in connection with Fig. 1 may for instance be used for collecting answers during examinations. Each examinee is provided with an electronic pen. The answers to the examination questions are electronically recorded and transmitted to the receiving device for centralized processing either in the receiving device itself or in another unit to which the answers are forwarded. There are a number of advantages with using electronic pens during examinations.

Answers may for instance be collected electronically and yet examinees may write their answers in the same way as when using an ordinary pen. Electronically recorded answers are easily distributed to examiners. Also, valuable statistics can be gathered from how the examinees answer their questions.

The above-described system may also be used during conferences or lectures to receive input from an audience, allowing for more interactive or audience customized lectures. For example, the system can be used for gathering results from audience polls or votes. It goes without saying that there are a number of other situations in which it would be beneficial to use a plurality of electronic pens for capturing data for subsequent transmission to a central receiving unit.

PEN PROCESS Fig. 2 shows an embodiment of a method for transferring data from an electronic pen to a receiving device. The method is suitable for use in a system where a plurality of electronic pens needs to transmit data to a single receiver over a limited number of concurrent communication channels, like in the system described in connection with Fig. 1 when e.g. Bluetooth is used as the communication link. The illustrated method comprises two processes which are executed essentially concurrently. Essentially concurrently denotes that the processes are executed in parallel (or differently put, in an asynchronous and/or independent manner). They may for example be implemented as being executed in different tasks, processes or threads in a control unit (e.g. control unit 410, see Fig. 4 below) of the pen, where the control unit is thus capable of multi- tasking of some sort.

In one of the processes, pen data is generated and buffered in the pen, step 271. Positional data is generated successively as the user uses the pen. Any free-standing data may also be generated successively during use of the pen. Any pen-resident data and operational data to be transferred may typically be retrieved when pen data is to be transferred. The other process, which is a pen data transfer process, may start as soon as the pen is turned on. If there is no positional data to transfer at that time, dummy positional data may be transferred, for instance together with operational data. This would make possible testing of the pen before the user starts to write. As an alternative the start of the pen data transfer process may be triggered by the generation of positional data. The pen data transfer process of Fig. 2 starts with a "request transfer of pen data" step

272, in which the electronic pen attempts to acquire a communication channel 132 to send pen data to the receiving device 135. This step may involve sending a message to the receiving device to allocate resources for the transfer.

If, in a conditional "failure detected due to insufficient communication channel capacity" step 274, it is detected that the transfer medium, such as Bluetooth, has insufficient capacity under the current load to transfer the pen data to the receiving device, the process continues to a "wait" step 276. Otherwise, the process continues to a "send data" step 278.

The failure detection step may involve receiving a message from the receiving device to the effect that capacity is unavailable or detecting a failure to receive, within a time-out period, a response from the receiving device to the transfer request. In the "wait" step 276 the pen waits a certain time before returning to the "request transfer of pen data" step 272 to request to transfer the pen data once again. The waiting period is selected so as to reduce the risk of collision with pen data transfer from other electronic pens in the system. It may be different depending on whether the wait step is carried out next to the "send data" step 278 or next to the "failure detected due to insufficient communication channel capacity" step 274. It may also be different each time the "wait" step 276 is performed. In one embodiment the waiting period is always the same after a successful transfer of pen data, whereas the length of the waiting period is varied after a failed transfer attempt. The latter waiting period may for instance be randomly selected within certain limits so that it is ensured that attempts are carried out with a certain frequency. In another embodiment, the length of all waiting periods is varied within certain limits. Statistical methods can be used to optimize the waiting periods. In one embodiment the receiving device sets configurations values in the pens, e.g. the length of a basic waiting period which could, when needed, be modified using random algorithms.

In the "send data" step 278, a communication channel has already been established between the pen and the receiving device, whereby the pen here transfers available pen data, i.e. pen data that has been recorded but not previously successfully transferred to the receiving device. After the pen data has been transferred, the process proceeds to the "wait" step 276. The successfully transferred pen data may be deleted from the memory of the pen when the transfer has been completed. In another embodiment, the pen transfers available pen data when it determines that it is time to make a transfer attempt. The pen then waits for an acknowledge^ment from the receiving device that the pen data has been successfully received. If the acknowledgement is not received within a predetermined time period, the attempt is considered as a failure. The pen then waits a waiting period before it makes a next transfer attempt by sending the then available pen data. If the acknowledgement is received the pen makes the next transfer attempt after a waiting period.

It should be understood that the pen data transfer process that implements the intermittent transfer of pen data may be controlled by an application which is built on top of an existing communication protocol. When for instance Bluetooth is used as the communication protocol, the application may communicate with the Bluetooth communication protocol stack to implement the pen data transfer process. ELECTRONIC PEN

Below follows a description with reference to Fig. 4 of an embodiment of an electronic pen 400 that can be used in a system of the above-described type. The pen has a pen-shaped casing or shell 402 that defines a window or opening 404, through which images are recorded. The casing contains a camera system 406, an electronics system and a power supply.

The camera system 406 may comprise at least one illuminating light source, a lens arrangement and an optical image reader (not shown in the drawing). The light source, suitably a light-emitting diode (LED) or laser diode, illuminates a part of the area on the product surface that can be viewed through the window 404, by means of infrared radiation. An image of the viewed area is projected on the image reader by means of the lens arrangement. The image reader may be a two-dimensional CCD or CMOS detector which is triggered to capture images at a fixed or variable rate, typically at about 70-100 Hz. The power supply of the pen 400 is advantageously at least one battery 408, which alternatively can be replaced by or supplemented by mains power (not shown).

The electronics system comprises a control unit 410 which is connected to a memory block 412. The control unit 410 is responsible for the different functions in the electronic pen and can advantageously be implemented by a commercially available microprocessor such as a CPU ("Central Processing Unit"), by a DSP ("Digital Signal Processor") or by some other programmable logical device, such as an FPGA ("Field Programmable Gate Array") or alternatively an ASIC ("Application-Specific Integrated Circuit"), discrete analog and digital components, or some combination of the above. The memory block 412 may comprise different types of memory, such as a working memory (e.g. a RAM) and a program code and persistent storage memory (a non- volatile memory, e.g. flash memory). Associated software is stored in the memory block 412 and is executed by the control unit 410 in order to provide a pen control system for the operation of the electronic pen. The software may for instance include an application which implements the above-mentioned pen data transfer process. One embodiment of a pen control system for this kind of electronic pen is described in WO06/049573, which is hereby incorporated by reference. One function provided by the control unit 410 is a clock, allowing relative and optionally absolute time to be retrieved by software executing in the control unit 410. The clock can be implemented in the control unit 410 itself or using an auxiliary unit (not shown).

The casing 402 also carries a pen point 414 which allows the user to write or draw physically on the product surface by a pigment-based marking ink being deposited thereon. The marking ink in the pen point 414 is suitably transparent to the illuminating radiation in order to avoid interference with the opto-electronic detection in the electronic pen. A contact sensor 416 is operatively connected to the pen point 414 to detect when the pen is applied to (pen down) and/or lifted from (pen up) the product surface, and optionally to allow for determination of the application pressure. Based on the output of the contact sensor 416, the camera system 406 is controlled to capture one or more images between a pen down and a pen up. These images are processed by the control unit 410 to generate above-mentioned positional data, defining a sequence of positions that represent the absolute or relative locations and movements of the pen on the surface.

The generated pen data can be output by the pen, via a built-in transceiver 418 functioning as a communica^tions interface, to a nearby or remote apparatus such as the receiving device 135. To this end, the transceiver 418 may provide components for wireless short-range communication,e.g. Bluetooth, WUSB, radio transmission, infrared transmission, ultrasound transmission, inductive coupling, etc), and/or components for wireless remote communication, typically via a computer, telephone or satellite communications network, for example utilizing TCP/IP.

The pen may also include an MMI (Man Machine Interface) 420 which is selectively activated for user feedback. The MMI may include a display, an indicator lamp, a vibrator, a speaker, etc.

Still further, the pen may include one or more buttons 422 by means of which it can be activated and/or controlled.

The pen may also include hardware and/or software for generating free-standing data, e.g. audio data, image data, video data, barcode data, data relating to a pen user's operation of buttons on the pen and/or character-coded data. The pen may for instance include a microphone for recording audio data, an optical sensor and software for recording and processing of barcode data and/or hand-writing recognition (HWR) software for converting positional data representing handwriting to character-coded data.

The memory block 412 of the pen may store pen-resHdent parameters, e.g. a pen-ID, which uniquely identifies the pen, a language identifier, a name, a street address, an electronic mail address, a phone number, a pager number, a fax number, a credit card number, etc. The pen- resident parameters may be stored in the pen in connection with the manufacturing of the pen and/or down-loaded in the memory block during use of the pen. PRODUCT AND POSITION CODING PATTERN

In one embodiment, the product 131 of Fig. 1 is provided with a position-coding pattern which makes it possible for the pen to determine its position on the product. There are different types of position-coding pattern. One type comprises cells or complex symbols, which are arranged side-by-side on the product and each of which codes a position. Another type of position-coding pattern has a window property, which means that each part area of a predetermined size, is unique within the position-coding pattern and thus codes an unambiguous position in the position-coding pattern. Each position may be coded by a plurality of simple symbols, like dots, and at least some of a plurality of symbols which are used for coding a first position also contribute to the coding of a second adjacent position. Examples of position-coding patterns of this latter type are found in e.g. US 6,570,104; US 6,663,008 and US 6,667,695, which are herewith incorporated by reference. These position-coding patterns are suitable for recording handwriting. Under other circumstances, e.g. when the electronic pen is to be used exclusively as a point and click pen, the position-coding pattern can be simpler and have lower position resolution. The pattern may for instance code the same position or position identifier in a whole field on the product if the specific position within the field is unimportant.

A large position-coding pattern can be subdivided into page units. The subdivision may e.g. be made directly in the position-coding pattern in that a unique page identifier is coded into the position-coding pattern of each page unit together with local position indications. As an alternative, a control unit in the pen or elsewhere may have knowledge of the logical subdivision of the pattern so that it can calculate a page address and local position indications from the position data recorded from the position-coding pattern, see e.g. WO01/48685, which is hereby incorporated by reference.

When a sufficiently large position-coding pattern is used, each product surface may be provided with a subset of the position-coding pattern representing a different page unit. In a system of the kind described in connec-tion with Fig. I₅ all products may e.g. be provided with the same subset(s) of a position-coding pattern, i.e. the products are identical with respect to the positions coded thereon. If the product is a multi-page document the position-coding pattern may be the same on all pages or different from page to page. Alternatively, the position-coding pattern may be different from product to product, so that the individual product is uniquely identified by the positions coded by the position-coding pattern. In the same way as in the first case the position-coding pattern may then be the same on all pages within a document or different from page to page if the product is a multi-page document.

The product 131 may also have embedded functionality in that one or more part areas of the position code on the product is associated with one or more functions that selectively operate on electronic pen strokes. Such areas which are known by the pen, are called pidgets. Each pidget may have a pidget ID to identify it. The functions may involve e.g. a qualification of the pen strokes, such as an association of a line width or a color with the pen strokes, or a specific processing of the pen strokes, such as subjecting the pen strokes to character recognition or trans^ferring the pen strokes in a selected manner to a receiver. When used on the product, the electronic pen records positional data which represents its position on the product. Depending on the type of position-coding pattern on the product, the positional data may be recorded in the form of a page address and local coordinates on the page or as a global position in the position-coding pattern, which may or may not be converted to a logical page address and local coordinates by the pen before transfer to the receiving unit. RECEIVING DEVICE PROCESS

Fig. 3 shows an embodiment of a method in a receiving device 135 for receiving pen data from an electronic pen 100.

In a "receive pen data" step 380, the receiving device receives pen data from the electronic pen 100. The receiving device 135 may receive pen data concurrently from a plurality of pens. The pen data is received intermittently from each pen while the pen is used on a product to make pen strokes which are electronically recorded and included in the pen data. As already mentioned, the pen data may comprise positional data, operational data, free-standing data and/or pen-resident data.

In this embodiment, operational data is first extracted from the received pen data in an "extract operational data from pen data" step 382.

In a conditional "action needed due to operational data" step 384, it is determined whether the operational data is such that it is determined to be of potential use for an operator, such as a user of the computer 136 or the workstation 140. For example, if the operational data indicates that batteries of the pen associated with the pen data are about to run out, it is useful to communi^cate this condition to the operator. If it is determined that the operational data requires an action, the process continues to a "perform appropriate action" step 386. On the other hand, if it is determined that the operational data does not give rise to any action, the process continues to a "store pen data" step 388.

In the "perform appropriate action" step 386, an appropriate action is performed. For example, if it has been determined that batteries of the pen associated with the pen data are about to run out, this condition is suitably communicated to the operator, e.g. by triggering an alarm and/or displaying a message on computer 136 or workstation 140. The operator can thus solve the battery problem of the pen in question, e.g. by replacing the pen with a new pen or replacing batteries in the pen, which prevents the batteries from unexpectedly running out completely and disrupting usage of the pen for a longer time. The appropriate action may also involve a communrxation from the receiving device to the relevant pen. The pen may e.g. be instructed to vibrate to indicate to the user that the pen is faulty and needs to be replaced. Once the appropriate action has been performed, the process continues to the "store pen data" step 388.

In the "store pen data" step 388, the received pen data is stored in a storage device, such as storage device 138.

Software at the receiving end of the system may also supervise the electronic pen in other ways than by using the operational data. It may for instance check that each pen in the system transfers data as expected. If data has not been received from a certain pen during a predetermined time, an alarm can be triggered, so that an operator can check the pen in question.

Other data than operational data may also be extracted from the pen data in connection with the receipt of the pen data in the receiving device. Identifying information, e.g. a pen- resident pen identifier, may be extracted and used for storing pen data from a specific pen separately from pen data from other pens. Likewise, a page address or other document identifier can be extract^ed to enable separate storage of pen data relating to a specific document. Other information which is included in all file objects from a specific pen or generated from a specific document, so that it is common to all relevant file objects, can also be used for this purpose. Alternatively a hardware communication address assigned to the pen, such as a MAC address (Media Access Control address) or a DLC address (Data Link Control address) may be used as identifying information for sorting up pen data and storing pen data from a specific pen separately from pen data from other pens. The receiving device or another device to which the pen data is sent may combine pen strokes which together make up an electronic document which was created by means of a specific electronic pen and/or on a specific document. The time stamps included in the file objects may be used to time synchronize pen strokes and pidgets. It should be mentioned that it could be useful to include operational data in the pen data also when other transfer modes are used, such as when using a streaming mode, in order to be able to monitor pen status at the receiving end. COMMUNICATION STATES

With reference to Fig. 5, now follows a description of an example of states and transitions in the pen 100 which may occur in relation to communication of pen data from the pen 100 to the receiving device 135. The example relates to the pen process embodiment shown in Fig. 2.

An initial state for the pen 100 is a "communication idle" state 750. In this state, no payload communication is occurring from the pen 100 to the receiving device 135. Regardless of state, the "generate pen data" step 271 may execute to generate pen data representing the movements of the pen 100 on the product surface, and to store the pen data in memory such as memory block 412 (Fig. 4). The pen data may be sent in file objects to the receiving device. These file objects can either be created when the pen data is generated or just before the data transfer. Periodically, the control unit 410 determines that it is time to attempt to send the hitherto stored, or buffered, pen data to the receiving device. The basic rule may be to wait and send any unsent pen data every n seconds, where n can be any suitable number. In one embodiment, n is set to 60. In another embodiment, the control unit 410 determines that it is time to make a transfer attempt, when a certain amount of pen data has been generated, e.g. when a pen data buffer has been filled to a predetermined extent.

When it is determined that it is time to send the file objects, a TIMER event 760 is triggered and the pen 100 changes state to a "requesting channel" state 752.

In the "requesting channel" state 752, the trans-'ceiver 418 of the pen 100 is attempting to acquire a communication channel. If there are a large number of pens 100, in the same area, which all typically use the same transfer technology, all communication channels may be used. In such case the request for the communication channel will fail, leading to a FAILURE event 762 being generated and the pen 600 returning to the "communication idle" state 750. The detection of a communication channel not being available can for instance be performed by receiving a message from the receiving device indicating that a channel is unavailable, or by not succeeding with setting up a channel within a time-out period (e.g. by failing to receive a response to the request for the communication channel from the receiving device) or by collision detection. Once back in the "communication idle" state 750, after a FAILURE event 762, the pen waits again to send the pen data. In one embodiment, this period of wait after a communication request failure is different from the original wait time. The pen may for instance wait a base period, which could be the period of the last wait, randomly adding or subtracting a random number of seconds. In a situation where it is difficult to acquire a communication channel, an aggregate use of this algorithm by all pens 100, will yield less RF usage and more efficient use of a limited number of communication channels.

If, on the other hand, the request for a communi^cation channel is a success, a CONNECTED event 764 is generated and the pen transitions to a "performing communication" state 754. The success of the request for a communication channel can, for example, be indicated by receiving a message from the receiving device 135 indicating that it has been capable of allocating the required resources, such as establishing a Bluetooth communication channel, and that it is prepared to receive pen data.

In the "performing communication" state 754, active communication is possible, allowing the pen 100 to trans-mit data to the receiving device 135. As an example, in one embodiment, when Bluetooth is used as a transmission technology and a user is actively writing, only a few seconds of connection time is required to send the relevant data generated every 60 seconds. Once all file objects have been sent to the transceiver 134, a COMPLETED event 766 is generated, the file objects may be deleted from the local storage (e.g. memory block 412 of Fig 4) in the pen 100, and the pen 100 returns to the "communication idle" state 750. The next triggering of the TIMER event 760 will occur after the basic waiting period, i.e. 60 seconds in the present example.

While in the "requesting channel" state 752 or "performing communication" state 754, any new positional data or other captured data, is not lost. This data is stored temporarily and will be sent the next time the pen 100 is in the "performing communication" state 754.

Consequently, with a planned intermittent communrxation method illustrated by the state machine in Fig. 7, data loss may be avoided even if channel requests occasionally fail. It is more resource efficient and secure in transfer compared to online communication where data is sent as it becomes available, e.g. in a streaming manner. Below follows an example of how a file object may be structured when used in an above- described system:

File Header (File object generator ID, Page Address, Number of pages, Number of additional data items)

Page data header (Page Address, Number of pidgets) Page data (Stroke data) Pidget data (Pidget ID(s), Timestamp(s))

Additional data (Operational data, Pen-resident parameter value(s), Data items resulting from pidgets, Freestanding data)

This file object is intended to include all pen data generated since the previous successful pen data trans-fer. The pen data may refer to different pages having different page addresses. The file object may include one page data header and page data and pidget data for each page on which pen strokes have been created since the previous successful pen data transfer. In another embodiment one file object per page may be created.

Thus, in this file object structure, the positional data included in the aforementioned pen data is referred to as "Page data" and "Pidget data", whereas the operational data included in the aforementioned pen data is referred to as "Additional data". The stroke data may for instance comprise local positions on a specified page, time stamps and pressure values. Pidget IDs may identify a pidget which has been marked by the pen. The File object generator ID identifies the generator of the file object. It may indicate e.g. which software or what action triggered the creation of the file object.

Which data the pen shall include in a file object may be e.g. predetermined or determined by the position information, such as the page address, coded on the product on which the pen is used.

The file object may be either character-encoded or non-character-encoded (e.g. binary), and may be in any suitable format. The file format may be proprietary or standardized, for example XML (Extensible Markup Language), HTML (Hypertext Markup Language), XForms, PDF (Portable Document Format), etc.

The file object allows a software at the receiving end of the system, to identify and extract all or selected parts thereof. EXAMPLE OF USE AT EXAMINATION

As already mentioned, the above-described system of Fig. 1 can for instance be used in connection with examinations to electronically collect answers for centralized handling. Each examinee is provided with an electronic pen and a position-coded examination form. The examinees are instructed to turn on the electronic pens before the examination is started. The pens then start to send pen data intermittently to the receiving device, which uses the operational data to check the operational status of the pens. This makes it possible to rectify any problem before start of the examination.

When the examination has started, each examinee 130 uses his/her pen 100 like an ordinary pen to answer questions on the examination form. The pens deposit ink on the examination form like an ordinary pen. At the same time, the pen 100 repeatedly records positions of itself on the product so that all pen strokes are electronically recorded. If the examinee wants to take notes that should not be electronically recorded, he or she could use an ordinary paper without position-coding. Essentially periodically, the pens 100 transfer examination data in one or more file objects, over the RF links 132 to the RF transceiver 134. In addition to pen stroke data (positional data) the file objects may e.g. include pen-ID and free-standing data recorded by the pen. The data transfer may be carried out as described above. The computer 136 receives the file objects via the RF transceiver 134 and stores them in the storage device 138. The operational status of the pens is continuously monitored. When the examination is over, the computer 136 may instruct the pens to give feed-back to the examinees that they should stop writing. The pens may also stop transferring data. At the end of the examina^~tion, all answers of all examinees 130, are electronic-'ally stored in the storage device 138. The data sent from the pens to the computer 136 is self-supporting or autonomous, i.e. the receiving computer 136 is able to access and process the data without any need for the computer 136 to initiate any communication with the pens that created the data. All received pen data is combined in the computer into combined pen data for each pen, either incrementally as each file object with pen data is received or once, when all the pen data has been receiv^ed. Consequently, each file object can be seen as a file itself, but also as part of one combined file for the pen in question. A person authorized to mark examinations has access to the workstation 140. As the workstation is connected to the computer 136 and its storage device 138, the workstation can have access to all the examination data. The examination data is stored such that data related to each pen 100 can be independently retrieved. This is implemented by storing data for each pen 100, in a, logically or physically, separate portion of the storage device 138. For example, the different portions for the different pens 100, can be separate memory units or separate memory areas within the storage device 138. Alternatively the pen data for the different pens 100 is logically separated and is retrievable using a key, for example pen ID's. Consequently, when a requester (marking person) requests pen data for an examinee 130 having used a particular pen 100, this data is separately retrievable, independently of other pen data stored in the same storage device 138.

The marking of the examinations can be manual, automatic or a combination thereof. If automatic marking is used, such as for multiple choice questions, the computer 136 or the workstation 140 can perform the marking by executing appropriate software. For manual marking, software running on the computer 136 or workstation 140 allows a marker person to mark answers by examinees 130. The marking may be performed by several marking people, each having access to a workstation 140. When several marking people are used, the examinations may be divided such that each marking person marks only a subset, e.g. one or two particular questions of the examinations, or each marking person may mark entire examinations for a number of examinees 130.

The computer 136 and/or workstation 140 can be provided with different access levels, where a supervisor is allowed access to all operational data, and a marking person has access to pen data, i.e. to what each examinee has written. A significant amount of useful information can be retrieved from the data made available in the storage device 138. For example, based on position data and time^stamps, it is possible to determine how long time on average an examinee 130 has spent writing an answer to a particular question, indicating a level of difficulty for that question. It is also possible to see if a particular question is often skipped initially and returned to at the end of the time available for the examinee 130. Additionally, it is possible to see how much time has been spent writing on ordinary paper versus on examination form. Only some examples of what information can be derived from the data stored in the storage device 138 have been mentioned here; the available data can be used in a multitude of ways, for example using data mining software. SYSTEM DIMENSIONING To be able to dimension a system appropriately, it is useful to know the probability that all communication channels are busy in a communication system with a limited number of channels. This is given by the probability P in the following formula:

where N is a number of users, k is the number of communication channels, λ is an individual arrival rate of a user (modeled by an exponential distribution with mean 1/λ), and s is the service time modeled with a general distribution E[s] = 1/μ, where μ is average time each connection is used. Total arrival rate is approximated by Nλ.

Consequently, a system can be chosen where λ can be affected by configuring a normal wait time between transmissions, thereby affecting P. The invention has mainly been described above with reference to a few embodiments.

However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope and spirit of the invention, which is defined and limited only by the appended patent claims.

While Fig. 1, for illustrational purposes, only illustrates three concurrent pen users, the invention is not limited to any particular number of pen users and can be used with any suitable number of pens. Specifically, the present invention provides a way for a greater number of pens to be used concurrently, than if the present invention were not used.

Claims

1. A system for collecting pen data, comprising a plurality of electronic pens, which are configured to generate pen data by electronically recording pen strokes as they are made on a product surface, a receiving device for collecting pen data from said plurality of electronic pens, at least one communication channel for transfer of said pen data from the electronic pens to the receiving device, wherein the number of electronic pens are larger than the number of concurrent communication channels and wherein each electronic pen is configured to intermittently transfer the pen data to the receiving device as it is being generated.

2. A system as claimed in claim 1, wherein the electronic pens are configured to essentially periodically make an attempt to transfer pen data to the receiving unit.

3. A system as claimed in claim 2, wherein the electronic pens are configured to vary a length of a waiting period from a failed transfer attempt to a following transfer attempt in a randomized manner.

4. A system as claimed in any one of claims 1-3, wherein the receiving device is configured to combine pen data received from a specific electronic pen by using identifying information included in all pen data received from said specific electronic pen.

5. A method for generating and transferring an electronic document to a receiving device, comprising generating an electronic document by electronically recording pen strokes while they are being created on a product by an electronic pen, and successively transferring the electronic document from the electronic pen to a receiving device as the electronic document is being generated by intermittently transferring pen data, which comprises pen strokes that have been electronically recorded but not previously transferred, to the receiving unit.

6. The method as claimed in claim 5, wherein intermittently transferring pen data comprises essentially periodically making an attempt to transfer pen data.

7. The method as claimed in claim 6, comprising detecting a failed attempt to transfer pen data and waiting a waiting period before carrying out the next attempt to transfer pen data.

8. The method as claimed in claim 6, wherein each attempt to transfer pen data comprises requesting transfer of said pen data over a communication channel to said receiving device; determining whether said communication channel has capacity to transfer said pen data, and, if so, transferring said pen data to said receiving device; and, otherwise, waiting a waiting period before carrying out the next attempt to transfer pen data.

9. The method as claimed in claim 7 or 8, wherein the length of the waiting period is different from the length of a most recent previous waiting period.

10. The method as claimed in claim 7 or 8, comprising randomly selecting the length of the waiting period.

11. The method as claimed in any one of claims 5-10, comprising retrieving operational data relating to the operational status of the electronic pen and including said operational data in the pen data.

12. The method as claimed in any one of claims 5-11, comprising retrieving pen-resident data permanently stored in the pen and including said pen-resident data in the pen data.

13. The method as claimed in any one of claims 5-12, wherein electronically recording pen strokes comprises recording positional data representing positions of the electronic pen on a product surface.

14. The method as claimed in any one of claims 5-13, wherein said at least one communication channel complies with a short-range wireless communication technology selected from the group consisting of Bluetooth, wireless local area network, and wireless universal serial bus.

15. An electronic pen comprising a sensor for electronically recording pen strokes while they are created on a product by the electronic pen, said pen strokes forming an electronic document, and a control unit and a transmitter, which are configured to successively transfer the electronic pen strokes from the electronic pen to a receiving device as the electronic document is being generated by intermittently transferring pen data, which comprises those pen strokes that have been electronically recorded but not previously transferred, to the receiving unit.

16. A computer program product, directly loadable into the internal memory of an electronic pen, comprising software instructions that, when executed in said electronic pen, perform the method according to any one of claims 5-14.

17. A method for receiving an electronic document from an electronic pen, said method comprising intermittently and successively as the electronic document is generated, receiving file objects in a receiving device, said file objects comprising pen strokes that have been electronically recorded by the electronic pen while they were created on a product surface and that together form the electronic document; and combining the pen strokes of said file objects to form the electronic document by using identifying information that is included in the file objects of said electronic pen.

18. The method as claimed in claim 17, wherein the identifying information is a pen identifier which uniquely identifies said electronic pen to the receiving device.

19. The method as claimed in claim 17, wherein the identifying information is positional data which uniquely identifies said product surface to the receiving device.

20. The method as claimed in any one of claims 17-19, wherein at least one of the file objects furthermore comprises operational data, said method comprises determining an operational status of said electronic pen by evaluating said operational data.

21. The method according to claim 20, wherein said operational data comprises at least one piece of data selected from the group consisting of a battery level of said electronic pen, a hardware status of said electronic pen, a memory usage of said electronic pen and a signal strength of an RF link used for communication between said electronic pen and said receiving device.

22. A receiving device comprising a control unit and a receiver for receiving an electronic document from an electronic pen, wherein: said receiver is capable of intermittently and successively as the electronic document is being created by the electronic pen receiving file objects from the electronic pen via a communication channel from the electronic pen to the receiver, said file objects comprising pen strokes that have been electronically recorded by the electronic pen while they were created on a product surface, the control unit being configured to combine the pen strokes of said file objects to form the electronic document by using identifying information that is included in the file objects of said electronic pen.

23. A computer program product, directly loadable into the internal memory of a processor in a receiving device, comprising software instructions that, when executed in said processor, perform the method according to any one of claims 17-21.