Abstract:
An input tool for use with an interactive input system comprises a body housing processing circuitry storing input tool operating mode data representing operating modes of the input tool and at least one display on the body and communicating with the processing circuitry. The display is responsive to the processing circuitry to present a selected operating mode of the input tool.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to an interactive input system and to an input tool therefor. 
       BACKGROUND OF THE INVENTION 
       [0002]    Interactive input systems that allow users to input ink into an application program using an active pointer (e.g. a pointer that emits light, sound or other signal), a passive pointer (e.g. a finger, cylinder or other object) or other suitable input device such as for example, a mouse or trackball, are well known. These interactive input systems include but are not limited to: touch systems comprising touch panels employing analog resistive or machine vision technology to register pointer input such as those disclosed in U.S. Pat. Nos. 5,448,263; 6,141,000; 6,337,681; 6,747,636; 6,803,906; 7,232,986; 7,236,162; and 7,274,356 and in U.S. Patent Application Publication No. 2004/0179001 assigned to SMART Technologies ULC of Calgary, Alberta, Canada, assignee of the subject application, the disclosures of which are incorporated by reference in their entireties; touch systems comprising touch panels employing electromagnetic, capacitive, acoustic or other technologies to register pointer input; tablet and laptop personal computers (PCs); smartphones, personal digital assistants (PDAs) and other handheld devices; and other similar devices. 
         [0003]    Above-incorporated U.S. Pat. No. 6,803,906 to Morrison et al. discloses a touch system that employs machine vision to detect pointer interaction with a touch surface on which a computer-generated image is presented. A rectangular bezel or frame surrounds the touch surface and supports digital imaging devices at its corners. The digital imaging devices have overlapping fields of view that encompass and look generally across the touch surface. The digital imaging devices acquire images looking across the touch surface from different vantages and generate image data. Image data acquired by the digital imaging devices is processed by on-board digital signal processors to determine if a pointer exists in the captured image data. When it is determined that a pointer exists in the captured image data, the digital signal processors convey pointer characteristic data to a master controller, which in turn processes the pointer characteristic data to determine the location of the pointer in (x,y) coordinates relative to the touch surface using triangulation. The pointer coordinates are conveyed to a computer executing one or more application programs. The computer uses the pointer coordinates to update the computer-generated image that is presented on the touch surface. Pointer contacts on the touch surface can therefore be recorded as writing or drawing or used to control execution of application programs executed by the computer. 
         [0004]    U.S. Pat. No. 7,532,206 to Morrison et al. discloses a touch system that comprises a touch surface and at least one camera acquiring images of the touch surface. A pointer contact data generator generates pointer position data in response to pointer contact with the touch surface, the pointer position data representing where on the touch surface pointer contact is made. A processor communicates with the at least one camera and the pointer contact data generator. The processor analyzes acquired images to determine the type of pointer used to contact the touch surface, and processes the pointer position data in accordance with the determined type of pointer. In one embodiment, the processor distinguishes between pointer tip touch surface contacts, pointer backend touch surface contacts and finger touch surface contacts. A writing function is invoked in response to pointer tip touch surface contacts. An erase function is invoked in response to pointer backend touch surface contacts. Mouse events are generated in response to finger touch surface contacts. 
         [0005]    U.S. Pat. No. 7,202,860 to Ogawa discloses a coordinate input device that includes a pair of cameras positioned in upper left and upper right positions of a display screen of a monitor lying close to a plane extending from the display screen of the monitor, and views both a side face of an object in contact with a position on the display screen and a predetermined desk-top coordinate detection area to capture an image of the object within the field of view. The coordinate input device also includes a control circuit which calculates a coordinate value of a pointing tool, pointing to a position within a coordinate detection field, based on video signals output from the pair of cameras, and transfers the coordinate value to a program of a computer. 
         [0006]    Although the above-described interactive input systems are satisfactory, improvements are desired. It is therefore an object at least to provide a novel interactive input system, and a novel input tool therefor. 
       SUMMARY OF THE INVENTION 
       [0007]    Accordingly, in one aspect there is provided an input tool for use with an interactive input system, the input tool comprising a body housing processing circuitry storing input tool operating mode data representing operating modes of said input tool; and at least one display on the body and communicating with said processing circuitry, said display being responsive to said processing circuitry to present a selected operating mode of said input tool. 
         [0008]    In one embodiment, the processing circuitry is responsive to user input to select one of the input tool operating modes for presentation on the display. The input tool operating modes may be grouped into categories with the operating modes of a user selected category being selectable for presentation on the display. 
         [0009]    In one embodiment, at least one manually actuable element is provided on the housing. The processing circuitry is responsive to actuation of the at least one element to enable user selection of an input tool operating mode. 
         [0010]    In one embodiment, the processing circuitry wirelessly broadcasts the selected input tool operating mode. In one form, the selected input tool operating mode may be used to modulate a signal broadcast by the processing circuitry. The display in one form is configured to display textual and graphical information and may present a graphical image icon of the selected input tool operating mode. The graphical image icon may generally correspond to an appearance of digital ink associated with the selected input tool operating mode. 
         [0011]    According to another aspect there is provided an input tool for use with an interactive input system, the input tool comprising a pair of arms rotatably connected together by a hinge; a sensor providing output representing the angle formed between said arms; and processing circuitry communicating with said sensor and outputting a signal comprising angle information. 
         [0012]    In one embodiment, the sensor comprises a potentiometer. The processing circuitry wirelessly broadcasts the signal and the angle information may be used to modulate the broadcast signal. 
         [0013]    According to another aspect there is provided an input tool for use with an interactive input system, the input tool comprising an elongate body; and a deformable nib at one end of said body configured to contact an interactive surface. 
         [0014]    In one embodiment, the deformable nib is generally conical and wherein the shape of the deformable nib becomes less conical and more cylindrical as pressure applied to the interactive surface by the deformable nib increases. The deformable nib may be fabricated of visco-elastic polyurethane foam that is coated with a polytetrafluoroethylene-based material. 
         [0015]    According to another aspect there is provided an interactive input system comprising at least one imaging assembly capturing image frames of a region of interest; and processing structure communicating with said at least one imaging assembly and processing said captured image frames to determine the shape of an input tool tip appearing therein; and generate tip pressure data based on the determined shape of said input tool tip. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    Embodiments will now be described more fully with reference to the accompanying drawings in which: 
           [0017]      FIG. 1  is a schematic, partial perspective view of an interactive input system; 
           [0018]      FIG. 2  is a block diagram of the interactive input system of  FIG. 1 ; 
           [0019]      FIG. 3  is a block diagram of an imaging assembly forming part of the interactive input system of  FIG. 1 ; 
           [0020]      FIGS. 4A and 4B  are front and rear perspective views, respectively, of a housing assembly forming part of the imaging assembly of  FIG. 3 ; 
           [0021]      FIG. 5  is a block diagram of a master controller forming part of the interactive input system of  FIG. 1 ; 
           [0022]      FIGS. 6A and 6B  are side elevational and top plan views, respectively, of an input tool for use with the interactive input system of  FIG. 1 ; 
           [0023]      FIG. 7  is a block diagram of the input tool of  FIGS. 6A and 6B ; 
           [0024]      FIGS. 8A to 8C  are side elevational views of the input tool of  FIGS. 6A and 6B , showing different operating modes presented on a display thereof; 
           [0025]      FIG. 9  is a side elevational view of an alternative input tool for use with the interactive input system of  FIG. 1 ; 
           [0026]      FIG. 10  is a block diagram of the input tool of  FIG. 9 ; 
           [0027]      FIG. 11  is a side elevational view of another alternative input tool for use with the interactive input system of  FIG. 1 ; 
           [0028]      FIGS. 12A to 12D  are side elevational views of the input tool of  FIG. 11 , showing deformation of the input tool tip in response to applied pressure; and 
           [0029]      FIG. 13  is a front view of an interactive surface of the interactive input system of  FIG. 1 , displaying digital ink input using the input tool of  FIG. 11 . 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0030]    Turning now to  FIGS. 1 and 2 , an interactive input system that allows a user to inject input such as digital ink, mouse events etc. into an executing application program is shown and is generally identified by reference numeral  20 . In this embodiment, interactive input system  20  comprises an interactive board  22  mounted on a vertical support surface such as for example, a wall surface or the like or otherwise supported in a generally upright orientation. Interactive board  22  comprises a generally planar, rectangular interactive surface  24  that is surrounded about its periphery by a bezel  26 . An ultra-short throw projector (not shown) such as that sold by SMART Technologies ULC under the name SMART UX60 is also mounted on the support surface above the interactive board  22  and projects an image, such as for example a computer desktop, onto the interactive surface  24 . 
         [0031]    The interactive board  22  employs machine vision to detect one or more pointers brought into a region of interest in proximity with the interactive surface  24 . The interactive board  22  communicates with a general purpose computing device  28  executing one or more application programs via a universal serial bus (USB) cable  30  or other suitable wired or wireless connection. General purpose computing device  28  processes the output of the interactive board  22  and adjusts image data that is output to the projector, if required, so that the image presented on the interactive surface  24  reflects pointer activity. In this manner, the interactive board  22 , general purpose computing device  28  and projector allow pointer activity proximate to the interactive surface  24  to be recorded as writing or drawing or used to control execution of one or more application programs executed by the general purpose computing device  28 . 
         [0032]    The bezel  26  in this embodiment is mechanically fastened to the interactive surface  24  and comprises four bezel segments  40 ,  42 ,  44 ,  46 . Bezel segments  40  and  42  extend along opposite side edges of the interactive surface  24  while bezel segments  44  and  46  extend along the top and bottom edges of the interactive surface  24  respectively. In this embodiment, the inwardly facing surface of each bezel segment  40 ,  42 ,  44  and  46  comprises a single, longitudinally extending strip or band of retro-reflective material. To take best advantage of the properties of the retro-reflective material, the bezel segments  40 ,  42 ,  44  and  46  are oriented so that their inwardly facing surfaces extend in a plane generally normal to the plane of the interactive surface  24 . 
         [0033]    A tool tray  48  is affixed to the interactive board  22  adjacent the bezel segment  46  using suitable fasteners such as for example, screws, clips, adhesive etc. As can be seen, the tool tray  48  comprises a housing  48   a  having an upper surface  48   b  configured to define a plurality of receptacles or slots  48   c . The receptacles  48   c  are sized to receive input tools such as pen tools and an eraser tool that can be used to interact with the interactive surface  24 . Control buttons  48   d  are provided on the upper surface  48   b  to enable a user to control operation of the interactive input system  20 . One end of the tool tray  48  is configured to receive a detachable tool tray accessory module  48   e  while the opposite end of the tool tray  48  is configured to receive a detachable communications module  48   f  for remote device communications. The housing  48   a  accommodates a master controller  50  (see  FIG. 5 ) as will be described. Further specifics of the tool tray  48  are described in U.S. Patent Application Publication No. 2011/0169736 to Bolt et al. entitled “Interactive Input System and Pen Tool Tray Therefor” filed on Feb. 19, 2010, the disclosure of which is incorporated herein by reference in its entirety. 
         [0034]    Imaging assemblies  60  are accommodated by the bezel  26 , with each imaging assembly  60  being positioned adjacent a different corner of the bezel. The imaging assemblies  60  are oriented so that their fields of view overlap and look generally across the entire interactive surface  24 . In this manner, any pointer such as for example a user&#39;s finger, a cylinder or other suitable object, or a pen or eraser tool lifted from a receptacle  48   c  of the tool tray  48 , that is brought into proximity with the interactive surface  24  appears in the fields of view of the imaging assemblies  60 . A power adapter  62  provides the necessary operating power to the interactive board  22  when connected to a conventional AC mains power supply. 
         [0035]    Turning now to  FIG. 3 , one of the imaging assemblies  60  is better illustrated. As can be seen, the imaging assembly  60  comprises an image sensor  70  such as that manufactured by Aptina (Micron) MT9V034 having a resolution of 752×480 pixels, fitted with a two element, plastic lens (not shown) that provides the image sensor  70  with a field of view of approximately 104 degrees. In this manner, the other imaging assemblies  60  are within the field of view of the image sensor  70  thereby to ensure that the field of view of the image sensor  70  encompasses the entire interactive surface  24 . 
         [0036]    A digital signal processor (DSP)  72  such as that manufactured by Analog Devices under part number ADSP-BF522 Blackfin or other suitable processing device, communicates with the image sensor  70  over an image data bus  74  via a parallel port interface (PPI). A serial peripheral interface (SPI) flash memory  74  is connected to the DSP  72  via an SPI port and stores the firmware required for image assembly operation. Depending on the size of captured image frames as well as the processing requirements of the DSP  72 , the imaging assembly  60  may optionally comprise synchronous dynamic random access memory (SDRAM)  76  to store additional temporary data as shown by the dotted lines. The image sensor  70  also communicates with the DSP  72  via a a two-wire interface (TWI) and a timer (TMR) interface. The control registers of the image sensor  70  are written from the DSP  72  via the TWI in order to configure parameters of the image sensor  70  such as the integration period for the image sensor  70 . 
         [0037]    In this embodiment, the image sensor  70  operates in snapshot mode. In the snapshot mode, the image sensor  70 , in response to an external trigger signal received from the DSP  72  via the TMR interface that has a duration set by a timer on the DSP  72 , enters an integration period during which an image frame is captured. Following the integration period after the generation of the trigger signal by the DSP  72  has ended, the image sensor  70  enters a readout period during which time the captured image frame is available. With the image sensor in the readout period, the DSP  72  reads the image frame data acquired by the image sensor  70  over the image data bus  74  via the PPI. The frame rate of the image sensor  70  in this embodiment is between about 900 and about 960 frames per second. The DSP  72  in turn processes image frames received from the image sensor  72  and provides pointer information to the master controller  50  at a reduced rate of approximately 120 points/sec. Those of skill in the art will however appreciate that other frame rates may be employed depending on the desired accuracy of pointer tracking and whether multi-touch and/or active pointer identification is employed. 
         [0038]    Strobe circuits  80  communicate with the DSP  72  via the TWI and via a general purpose input/output (GPIO) interface. The strobe circuits  80  also communicate with the image sensor  70  and receive power provided on power line  82  via the power adapter  52 . Each strobe circuit  80  drives a respective illumination source in the form of a plurality of infrared (IR) light sources such as IR light emitting diodes (LEDs)  84  that provide infrared backlighting over the interactive surface  24  for the imaging assembly  60  during image capture. Further specifics of the strobe circuits are described in U.S. Patent Application Publication No. 2011/0169727 to Akitt filed on Feb. 19, 2010 and entitled “Interactive Input System Therefor”. 
         [0039]    The DSP  72  also communicates with an RS-422 transceiver  86  via a serial port (SPORT) and a non-maskable interrupt (NMI) port. The transceiver  86  communicates with the master controller  50  over a differential synchronous signal (DSS) communication link  88  and a synch line  90 . Power for the components of the imaging assembly  60  is provided on power line  92  by the power adapter  52 . DSP  72  may also optionally be connected to a USB connector  94  via a USB port as indicated by the dotted lines. The USB connector  94  can be used to connect the imaging assembly  60  to diagnostic equipment. 
         [0040]    The image sensor  70  and its associated lens as well as the IR LEDs  84  are mounted on a housing assembly  100  that is best illustrated in  FIGS. 4A and 4B . As can be seen, the housing assembly  100  comprises a polycarbonate housing body  102  having a front portion  104  and a rear portion  106  extending from the front portion. An imaging aperture  108  is centrally formed in the housing body  102  and accommodates an IR-pass/visible light blocking filter  110 . The filter  110  has an IR-pass wavelength range of between about 830 nm and about 880 nm. The image sensor  70  and associated lens are positioned behind the filter  110  and oriented such that the field of view of the image sensor  70  looks through the filter  110  and generally across the interactive surface  24 . The rear portion  106  is shaped to surround the image sensor  70 . Three tubular passages  112   a  to  112   c  are formed through the housing body  102 . Passages  112   a  and  112   b  are positioned on opposite sides of the filter  110  and are in general horizontal alignment with the image sensor  70 . Passage  112   c  is centrally positioned above the filter  110 . Each tubular passage receives a light source socket  114  that is configured to receive a respective one of the IR LEDs  84 . Mounting flanges  116  are provided on opposite sides of the rear portion  106  to facilitate connection of the housing assembly  100  to the bezel  26  via suitable fasteners. A label  118  formed of retro-reflective material overlies the front surface of the front portion  104 . Further specifics concerning the housing assembly and its method of manufacture are described in U.S. Patent Application Publication No. 2011/0170253 to Liu et al. filed on Feb. 19, 2010 entitled “Housing Assembly for Interactive Input System and Fabrication Method”. 
         [0041]    Turning now to  FIG. 5 , the master controller  50  is better illustrated. As can be seen, master controller  50  comprises a DSP  200  such as that manufactured by Analog Devices under part number ADSP-BF522 Blackfin. A serial peripheral interface (SPI) flash memory  202  is connected to the DSP  200  via an SPI port and stores the firmware required for master controller operation. A synchronous dynamic random access memory (SDRAM)  204  that stores temporary data necessary for system operation is connected to the DSP  200  via an SDRAM port. The DSP  200  communicates with the general purpose computing device  28  over the USB cable  30  via a USB port. The DSP  200  communicates with an external antenna  136  via a wireless receiver  138  and through its serial port (SPORT) with the imaging assemblies  60  via an RS-422 transceiver  208  over the differential synchronous signal (DSS) communication link  88 . In this embodiment, as more than one imaging assembly  60  communicates with the DSP  200  of the master controller  50  over the DSS communication link  88 , time division multiplexed (TDM) communications is employed. The DSP  200  also communicates with the imaging assemblies  60  via the RS-422 transceiver  208  over the synch line  90 . DSP  200  communicates with the tool tray accessory module  48   e  over an inter-integrated circuit I 2 C channel and communicates with the communications accessory module  48   f  over universal asynchronous receiver/transmitter (UART), serial peripheral interface (SPI) and I 2 C channels. 
         [0042]    As will be appreciated, the architectures of the imaging assemblies  60  and the master controller  50  are similar. By employing a similar architecture for both the imaging assemblies  60  and the master controller  50 , the same circuit board assembly and common components may be used for both thus reducing the part count and cost of the interactive input system. Differing components are added to the circuit board assemblies during manufacture dependent upon whether the circuit board assembly is intending for use in an imaging assembly  60  or in the master controller  50 . For example, the master controller  50  may require a SRAM  76  whereas the imaging assembly  60  may not. 
         [0043]    The general purpose computing device  28  in this embodiment is a personal computer or other suitable processing device comprising, for example, a processing unit, system memory (volatile and/or non-volatile memory), other non-removable or removable memory (eg. a hard disk drive, RAM, ROM, EEPROM, CD-ROM, DVD, flash memory, etc.) and a system bus coupling the various computing device components to the processing unit. The general purpose computing device  28  may also comprise a network connection to access shared or remote drives, one or more networked computers, or other networked devices. 
         [0044]    During operation, the DSP  200  of the master controller  50  outputs synchronization signals that are applied to the synch line  90  via the transceiver  208 . Each synchronization signal applied to the synch line  90  is received by the DSP  72  of each imaging assembly  60  via transceiver  86  and triggers a non-maskable interrupt (NMI) on the DSP  72 . In response to the non-maskable interrupt triggered by the synchronization signal, the DSP  72  of each imaging assembly  60  ensures that its local timers are within system tolerances and if not, corrects its local timers to match the master controller  50 . Using one local timer, the DSP  72  initiates a pulse sequence via the snapshot line that is used to condition the image sensor to the snapshot mode and to control the integration period and frame rate of the image sensor  70  in the snapshot mode. The DSP  72  also initiates a second local timer that is used to provide output on the LED control line  174  so that the IR LEDs  84  are properly powered during the image frame capture cycle. 
         [0045]    In response to the pulse sequence output on the snapshot line, the image sensor  70  of each imaging assembly  60  acquires image frames at the desired image frame rate. In this manner, image frames captured by the image sensor  70  of each imaging assembly  60  can be referenced to the same point of time allowing the position of pointers brought into the fields of view of the image sensors  70  to be accurately triangulated. Each imaging assembly  60  has its own local oscillator (not shown) and synchronization signals are distributed so that a lower frequency synchronization signal (e.g. the point rate, 120 Hz) for each imaging assembly is used to keep image frame capture synchronized. By distributing the synchronization signals for the imaging assemblies  60  rather than transmitting a fast clock signal to each imaging assembly from a central location, electromagnetic interference is reduced. 
         [0046]    During image frame capture, the DSP  72  of each imaging assembly  60  also provides output to the strobe circuits  80  to control the switching of the IR LEDs  84 . When the IR LEDs  84  are on, the IR LEDs flood the region of interest over the interactive surface  24  with infrared illumination. Infrared illumination that impinges on the retro-reflective bands of bezel segments  40 ,  42 ,  44  and  46  and on the retro-reflective labels  118  of the housing assemblies  100  is returned to the imaging assemblies  60 . As a result, in the absence of a pointer, the image sensor  70  of each imaging assembly  60  sees a bright band having a substantially even intensity over its length together with any ambient light artifacts. When a pointer is brought into proximity with the interactive surface  24 , the pointer occludes infrared illumination reflected by the retro-reflective bands of bezel segments  40 ,  42 ,  44  and  46  and/or the retro-reflective labels  118 . As a result, the image sensor  70  of each imaging assembly  60  sees a dark region that interrupts the bright band in captured image frames. The reflections of the illuminated retro-reflective bands of bezel segments  40 ,  42 ,  44  and  46  and the illuminated retro-reflective labels  118  appearing on the interactive surface  24  are also visible to the image sensor  70 . 
         [0047]    The sequence of image frames captured by the image sensor  70  of each imaging assembly  60  is processed by the associated DSP  72  to remove ambient light artifacts and to identify each pointer in each image frame. The DSP  72  of each imaging assembly  60  in turn conveys the pointer data to the DSP  200  of the master controller  50 . The DSP  200  uses the pointer data received from the DSPs  72  to calculate the position of each pointer relative to the interactive surface  24  in (x,y) coordinates using well known triangulation as described in above-incorporated U.S. Pat. No. 6,803,906 to Morrison. This pointer coordinate data together with pen tool operating mode information received by the DSP  200  from one or more pen tools via the external antenna  136  and wireless receiver  138 , if any, are conveyed to the general purpose computing device  28  allowing the image data presented on the interactive surface  24  to be updated. 
         [0048]    Turning now to  FIGS. 6A ,  6 B and  7 , a pen tool P for use with the interactive input system  20  is shown. In this embodiment, the pen tool P can be conditioned to one of a plurality of selectable operating modes as will be described. The pen tool P comprises a body  300  formed by interconnected half shells that has conical tips  302   a  and  302   b  at its opposite ends. A display  304 , which in this embodiment is a color liquid crystal display (LCD) that is capable of displaying textual and graphical information in a range of colors, is provided on the body  300  intermediate its ends. The display  304  is configured to display information associated with the currently active operating mode of the pen tool P. The selectable operating modes of the pen tool P are grouped into operating mode categories. A plurality of buttons are also provided on the body  300 . In this embodiment, the buttons include a pair of buttons  306  and  308 , which may be depressed to allow a user to select an operating mode category and an operating mode within the selected operating mode category as well as a power on/off button  310 , which may be depressed to allow the user to power the pen tool P on and off. 
         [0049]    The interior of the body  300  houses processing circuitry mounted on a printed circuit board. In this embodiment, the processing circuitry comprises a controller  312  that communicates with a wireless unit  316 . Wireless unit  316  is conditioned by the controller  312  to broadcast a modulated signal via a wireless transmitter  318 , such as for example, a radio frequency (RF) antennae or one or more illumination sources, such as IR LEDs, when the pen tool P is powered on through actuation of button  310 . The signal broadcast by the pen tool P is modulated by operating mode information that identifies the currently selected operating mode of the pen tool P. The controller  312  also communicates with memory  314  that stores information associated with the pen tool operating modes. In this embodiment, the memory  314  stores, for each selectable pen tool operating mode, its operating mode category, a graphical image icon of the pen tool operating mode, and the operating mode information that is used to modulate the signal broadcast by the pen tool P. The graphical image icon generally corresponds to an appearance of digital ink associated with the pen tool operating mode. A battery  320  supplies power to the processing circuitry. 
         [0050]    With the pen tool P powered on, when a user depresses button  306 , the controller  312  cycles through the operating mode categories stored in the memory  314 , and in turn displays the name of each operating mode category on the display  304  in succession. In this manner, the user can press the button  306  until the desired pen tool operating mode category appears on the display  304  thereby to select that pen tool operating mode category. Once a pen tool operating mode category has been selected, when the user depresses button  308 , the controller  312  cycles through the pen tool operating modes of the selected operating mode category, and in turn displays a graphical image representation of those pen tool operating modes on the display  304  in succession. 
         [0051]      FIGS. 8A to 8C  show examples of pen tool operating mode information displayed on the display  304  of the pen tool P. In the example shown in  FIG. 8A , the selected pen tool operating mode is a marker-line operating mode forming part of a marker operating mode category. As a result, the name “Marker” is displayed on the display  304  in a text field, and a graphical image representative of the selected pen tool operating mode is displayed on the display  304  as a line icon  332 . In the example shown in  FIG. 8B , the selected pen tool operating mode is a music-treble clef operating mode forming part of a music operating mode category. As a result, the name “Music” is displayed on the display  304  in the text field, and a graphical image representative of the selected pen tool operating mode is displayed on the display  304  as a treble clef icon  334 . In the example shown in  FIG. 8C , the selected pen tool operating mode is a marker-happy face operating mode also forming part of the marker operating mode category. As a result, the name “Marker” is displayed on the display  304  in the text field, and a graphical image representative of the selected pen tool operating mode is displayed on the display  304  as a happy face chain icon  336 . 
         [0052]    Once a threshold time period has passed after button  306  and/or button  308  has been depressed resulting in an operating mode category and a pen tool operating mode thereof being selected, in this embodiment one (1) second, the controller  312  conditions the wireless unit  316  to continuously broadcast a signal modulated with the operating mode information associated with the selected pen tool operating mode. Of course, a different threshold time period may be employed or the wireless unit may be configured to broadcast automatically a modulated signal upon powering up of the pen tool P. In this latter case, the signal may be broadcast with the last selected pen tool operating mode or a default pen tool operating mode being used to modulate the broadcast signal. 
         [0053]    The DSP  200  stores a modulated signal-to-pen tool operating mode mapping table in the memory  202 . When the pen tool P is brought into proximity with the interactive surface  24  and a broadcast modulated signal is received by the DSP  200  via the antenna  136  and wireless receiver  138 , the DSP  200  compares the received modulated signal to the mapping table to determine the pen tool operating mode. The DSP  200  in turn uses this information to assign mode information to the generated pointer coordinates, and conveys the mode information along with the pointer coordinates to the general purpose computing device  28  so that the pointer coordinates are processed by the general purpose computing device  28  in the desired manner. The general purpose computing device  28  treats the pointer coordinates as either marker (i.e. ink) events, eraser events, mouse events, or other events, in accordance with the mode information. 
         [0054]    Although in the embodiment described above, the pen tool P comprises a color LCD that is capable of displaying textual and graphical information in a range of colors, in other embodiments, the pen tool may alternatively comprise another type of display. For example, in other embodiments, the pen tool may comprise a monochromatic LCD, a single-line or multi-line display that is capable of displaying only alphanumeric information, and/or other types of displays that are capable of displaying alphanumeric information and/or graphical information. 
         [0055]    Although in the embodiment described above, the pen tool comprises buttons which may be depressed for selecting the operating mode category and the operating mode of the pen tool, in other embodiments, the pen tool may comprise other configurations. For example, the pen tool may comprise one or more switches capable of being toggled through multiple positions, one or more rotating switches, one or more scroll wheels, and/or one or more pressure or orientation sensitive switches etc., actuable to allow the operating mode category and operating mode of the pen tool P to be selected. In other embodiments, the pen tool may further comprise a microphone and the controller may be configured to execute voice recognition software to enable the operating mode category and pen tool operating mode to be selected by the user by voice command input into the microphone. In still other embodiments, the operating mode category and operating mode of the pen tool may also be selected through haptic commands, such as through pointer input on the interactive surface  24 . In a related embodiment, the display of the pen tool may be touch sensitive, and may be configured to receive touch input for selection of the operating mode category and operating mode of the pen tool. 
         [0056]      FIGS. 9 and 10  show another embodiment of an input tool in the form of a compass for use with the interactive input system  20 , and which is generally indicated using reference numeral  440 . Compass  440  comprises a first arm  442  and a second arm  444  that are pivotally connected to each other by a hinge  446 . The first and second arms  442  and  444  may be rotated relative to each other about the hinge  446  to vary the angle θ formed by the arms  442  and  444 . In this embodiment, the value of the angle θ may range from 0 degrees to 180 degrees. 
         [0057]    The compass  440  comprises processing circuitry mounted on a printed circuit board (not shown) that is housed within the first arm  442 . The processing circuitry comprises a controller  452  that communicates with a sensor in the form of a potentiometer  454  housed within the hinge  446 . The potentiometer  454  is configured to provide output proportional to the angle θ formed by the arms  442  and  444  to the controller  452 . The controller  452  also communicates with a wireless unit  456 . Wireless unit  456  is conditioned by the controller  452  to broadcast a modulated signal via wireless transmitter  458  when the compass  440  is powered on via power on/off switch  460  located on arm  442  and battery  462 . The broadcast signal is modulated by angle information that identifies the relative orientation of the arms  442  and  444 . 
         [0058]    In this embodiment, the DSP  200  stores a modulated signal-to-compass operating mode mapping table in the memory  202 . When the compass  440  is brought into proximity with the interactive surface  24  and a broadcast modulated signal is received by the DSP  200  via the antenna  136  and wireless receiver  138 , the DSP  200  compares the received modulated signal to the mapping table to determine the compass operating mode. The DSP  200  in turn uses this information to assign mode information to the generated pointer coordinates and conveys the mode information along with the pointer coordinates to the general purpose computing device  28  so that the pointer coordinates are processed by the general purpose computing device  28  in the desired manner. 
         [0059]    In this embodiment, when the compass  440  is fully closed and the angle θ between first and second arms  442  and  444  is substantially equal to zero (0) degrees, the DSP  200  assigns geometric correction mode information to the generated pointer coordinates. In this mode, the general purpose computing device  28  geometrically corrects digital ink displayed at locations corresponding to the pointer coordinates. The geometrical corrections may comprise, for example, straightening lines that are not straight, and rendering non-true geometric objects (e.g. triangles, rectangles, pentagons, etc.) true. When the compass  440  is fully open and the angle θ between first and second arms  442  and  444  is equal to approximately 180 degrees, the DSP  200  assigns orthogonal ink mode information to the generated pointer coordinates. In this mode, the general purpose computing device  28  generates digital ink in the form of either vertical or horizontal lines, only, at the generated pointer coordinates. When the compass  440  is partially open and the angle θ between first and second arms  442  and  444  is between zero and 180 degrees, the DSP  200  assigns compass ink mode information to the generated pointer coordinates. In this mode, the general purpose computing device  28  generates digital ink in the form of generally perfect arcs or circular lines at the generated pointer coordinates. 
         [0060]    If desired, a display may be provided on one or both of the arms for displaying the current compass operating mode. Similar to the previous embodiment, the display may be a colour or monochromatic LCD, a single or multi-line display or other suitable display. 
         [0061]    Although specific input tool operating modes and operating mode categories have been described, those of skill in the art will appreciate that many other input tool operating modes and categories may be assigned. 
         [0062]    Although in embodiments described above, the DSP  200  is shown as comprising an antenna and a wireless receiver for receiving the modulated signal output by the input tool, in other embodiments, each imaging assembly may alternatively be provided with an antenna and a wireless receiver for receiving the modulated signal output by the input tool. In other embodiments, the input tool may alternatively be tethered to the interactive board or to the DSP of the master controller for allowing the modulated signal output by the input tool to be conveyed by a wired connection. 
         [0063]    In other embodiments, the input tool may alternatively comprise one or more tip switch assemblies, each of which is actuable when brought into contact with the interactive surface. In these embodiments, the controller conditions the wireless unit and transmitter to broadcast the modulated signal upon actuation of a tip switch assembly. 
         [0064]    In other embodiments, the modulated signal that is broadcast by the input tool may also comprise a unique identifier of the input tool that allows the input tool to be distinguished from other input tools and/or other pointers by the interactive input system. 
         [0065]    It will also be appreciated that other forms of input tools may be used with the interactive input system  20 . For example,  FIG. 11  shows a pen tool or stylus for use with the interactive input system  20 , and which is generally indicated by reference numeral  540 . Stylus  540  comprises an elongate cylindrical body  542  having a generally conical, deformable nib  544  at one end thereof. The deformable nib  544  is fabricated of a resilient, compressible material, such that the profile of nib  544  compresses in response to pressure applied to the stylus  540  during use. The deformable nib  544  has a low-friction surface, which allows the stylus  540  to be easily moved across the interactive surface  24  during use at different amounts of applied pressure without damaging the interactive surface  24  and without causing offensive noise. In this embodiment, the deformable nib  544  is fabricated of visco-elastic polyurethane foam that is coated with a polytetrafluoroethylene (PTFE)-based material. 
         [0066]      FIGS. 12A to 12D  show the deformable nib  544  of the stylus  540  deforming in response to different amounts of applied pressure to the interactive surface  24 . When very light or no pressure is applied to the interactive surface by the stylus  540 , the deformable nib  544  maintains its original conical shape, as shown in  FIG. 12A . As the pressure applied by the stylus  540  to the interactive surface  24  is increased to light pressure, to medium pressure and to heavy pressure, as shown in  FIGS. 12B to 12D  respectively, the deformable nib  544  responds by compressing proportionately. As a result, the contact area between the deformable nib  544  and the interactive surface  24  increases. Also, the shape of the deformable nib  544  when viewed from the side becomes less conical and more cylindrical as the applied pressure increases. 
         [0067]    During operation, the DSP  200  uses the pointer tip shape, received from the DSPs  72  with the pointer data, to determine the tip pressure applied to the interactive surface  24  by the stylus  540 . The calculated pointer coordinates and the tip pressure are then conveyed by the DSP  200  to the general purpose computing device  28  via the USB cable  30 . The general purpose computing device  28  in turn processes the received pointer coordinates and tip pressure data, and updates the image output provided to the display unit, if required, so that the image presented on the interactive surface  24  reflects the pointer activity. 
         [0068]      FIG. 13  schematically shows digital ink displayed on the interactive surface  24  resulting from movement of the stylus  540  across the interactive surface  24 . During the movement, the pressure applied to the interactive surface  24  by the stylus  540  varies from very light pressure, to light pressure, to medium pressure and to heavy pressure. In response, the thickness of the digital ink appearing on the interactive surface  24  varies from very fine digital ink  562 , to fine digital ink  564 , to medium digital ink  56  and to thick digital ink  568 , respectively. 
         [0069]    Although in the embodiments described above, the imaging assemblies  60  are described as being positioned adjacent corners of the bezel, those of skill in the art will appreciate that the imaging assemblies may be placed at different locations relative to the bezel. 
         [0070]    Those of skill in the art will also appreciate that, although the operation of the interactive input system  20  has been generally described with reference to a single input tool being positioned in proximity with the interactive surface, the interactive input system  20  is capable of detecting multiple input tools that are positioned in proximity with the interactive surface. 
         [0071]    Although preferred embodiments have been described, those of skill in the art will appreciate that variations and modifications may be made with departing from the scope thereof as defined by the appended claims.