Abstract:
An interactive input system comprises at least one imaging device having a field of view looking into a region of interest. At least one radiation source emits radiation into the region of interest. A pliable bezel at least partially surrounds the region of interest. The pliable bezel has a reflective surface in the field of view of said at least one imaging device.

Description:
This application is a continuation of U.S. patent application Ser. No. 12/629,008, filed Dec. 1, 2009, the contents of which are incorporated herein by reference 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to interactive input systems and to a bezel therefor. 
     BACKGROUND OF THE INVENTION 
     Interactive input systems that allow users to inject input (e.g., digital ink, mouse events etc.) 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 suitable object) or other suitable input device such as for example, a mouse, trackball or interactive tablet, are 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 assigned to SMART Technologies ULC of Calgary, Alberta, Canada, assignee of the subject application, the contents of which are incorporated by reference; touch systems comprising touch panels employing electromagnetic, capacitive, acoustic or other technologies to register pointer input; tablet personal computers (PCs); touch-enabled laptop PCs; personal digital assistants (PDAs); and other similar devices. 
     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 cameras at its corners. The digital cameras have overlapping fields of view that encompass and look generally across the touch surface. The digital cameras acquire images looking generally across the touch surface from different vantages and generate image data. Image data acquired by the digital cameras 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. 
     To enhance the ability to detect and recognize passive pointers brought into proximity of a touch surface in touch systems employing machine vision technology, it is known to employ illuminated bezels to illuminate generally evenly the region over the touch surface. For example, U.S. Pat. No. 6,972,401 to Akitt, et al. assigned to SMART Technologies ULC, discloses an illuminated bezel for use in a touch system such as that described in above-incorporated U.S. Pat. No. 6,803,906. The illuminated bezel emits infrared red or other suitable radiation over the touch surface that is visible to the digital cameras. As a result, in the absence of a passive pointer in the fields of view of the digital cameras, the illuminated bezel appears in captured images as a continuous bright or “white” band. When a passive pointer is brought into the fields of view of the digital cameras, the passive pointer occludes emitted radiation and appears as a dark region interrupting the bright or “white” band in captured images allowing the existence of the pointer in the captured images to be readily determined and its position triangulated. Although this illuminated bezel is effective, it is expensive to manufacture and can add significant cost to the overall touch system. It is therefore not surprising that alternative techniques to illuminate the region over touch surfaces have been considered. 
     U.S. Pat. No. 7,283,128 to Sato discloses a coordinate input apparatus including a light-receiving unit arranged in the coordinate input region, a retroreflecting unit arranged at the peripheral portion of the coordinate input region to reflect incident light and a light-emitting unit which illuminates the coordinate input region with light. The retroreflecting unit is a flat tape and includes a plurality of triangular prisms each having an angle determined to be equal to or less than the detection resolution of the light-receiving unit. Angle information corresponding to a point which crosses a predetermined level in a light amount distribution obtained from the light receiving unit is calculated. The coordinates of the pointer position are calculated on the basis of a plurality of pieces of calculated angle information, the angle information corresponding to light emitted by the light-emitting unit that is reflected by the pointer. 
     Although the use of the retroreflecting unit to reflect and direct light into the coordinate input region is less costly than employing illuminated bezels, problems with such a retroreflecting unit exist. The amount of light reflected by the retroreflecting unit is dependent on the incident angle of the light. As a result, the Sato retroreflecting unit works best when the light is normal to its retroreflecting surface. However, when the angle of incident light on the retroreflecting surface becomes larger, the performance of the retroreflecting unit degrades resulting in uneven illumination of the bezel surrounding the coordinate input region. As a result, the possibility of false pointer contacts and/or missed pointer contacts is increased. Furthermore, prior retroreflective systems require relatively rigid bezels typically constructed of an inflexible material. For systems that must be portable, for example, in a military environment, these prior art systems are unsuitable. As will be appreciated, improvements in illumination for machine vision interactive input systems are desired. 
     It is therefore an object of the present invention to provide a novel interactive input system and bezel therefor. 
     SUMMARY OF THE INVENTION 
     Accordingly, in one aspect there is provided an interactive input system comprising at least one imaging device having a field of view looking into a region of interest; at least one radiation source emitting radiation into said region of interest; and a pliable bezel at least partially surrounding said region of interest, said pliable bezel having a surface in the field of view of said at least one imaging device. 
     According to another aspect there is provided a interactive input system comprising at least one imaging device having a field of view looking into a region of interest; and a pliable bezel at least partially surrounding said region of interest, said a bezel having a surface in the field of view of said at least one imaging device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments will now be described more fully with reference to the accompanying drawings in which: 
         FIG. 1  is a schematic diagram of an interactive input system comprising a pliable bezel. 
         FIG. 2  is a perspective view of a corner portion of the interactive input system of  FIG. 1  showing the pliable bezel wrapped partially around a bezel guide that projects from a support frame assembly. 
         FIG. 3  is a schematic block diagram of an imaging assembly forming part of the interactive input system of  FIG. 1 . 
         FIG. 4  is a schematic block diagram of a master controller forming part of the interactive input system of  FIG. 1 . 
         FIG. 5   a  is a perspective view of the corner portion of  FIG. 2  showing the pliable bezel wrapped partially around an alternative bezel guide that projects from the support frame assembly. 
         FIG. 5   b  is a perspective view of the corner portion of  FIG. 2  showing the pliable bezel wrapped partially around yet another alternative bezel guide that projects from the support frame assembly. 
         FIG. 5   c  is a perspective view of the corner portion of  FIG. 2  showing the pliable bezel wrapped partially around yet another alternative bezel guide that projects from the support frame assembly. 
         FIG. 6   a  is a perspective view of the corner portion of  FIG. 2  showing the pliable bezel wrapped partially around a bezel guide arrangement comprising a plurality of bezel guides that project from the support frame assembly. 
         FIG. 6   b  is a perspective view of the corner portion of  FIG. 2  showing the pliable bezel wrapped partially around an alternative bezel guide arrangement comprising a plurality of bezel guides that project from the support frame assembly. 
         FIG. 7  is a schematic diagram of another portion of the interactive input system of  FIG. 1  showing an alternative pliable bezel fastening technique. 
         FIG. 8  is a schematic diagram showing an alternative bezel guide configuration for use in the interactive input system of  FIG. 1 . 
         FIG. 9  is a schematic diagram of an interactive input system comprising a pliable inflatable bezel. 
         FIG. 10  is a schematic diagram of an interactive input system comprising an alternative pliable inflatable bezel. 
         FIG. 11  is a cross-sectional view of  FIG. 10  taken along lines  11 - 11 . 
         FIG. 12  is a schematic diagram of an interactive input system comprising yet another alternative pliable inflatable bezel. 
         FIG. 13  is a cross-sectional view of  FIG. 12  taken along lines  12 - 12 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Turning now to  FIG. 1 , an interactive input system that allows a user to inject input such as digital ink, mouse events etc. into an application program is shown and is generally identified by reference numeral  100 . In this embodiment, interactive input system  100  comprises a support frame assembly  102  that surrounds a touch surface  104 . Imaging devices  106   a  and  106   b  are mounted on the support frame assembly  102  and look generally across the touch surface  104  from different vantages to detect pointers brought into proximity with the touch surface  104 . The imaging devices  106   a  and  106   b  communicate with a master controller  108 , which in turn communicates with a general purpose computing device  110  executing one or more application programs. General purpose computing device  110  processes the output of the master controller  108  and provides display image output to a projection device  112 . Projection device  112  in turn projects an image onto the touch surface  104  that reflects pointer activity. In this manner, the imaging devices  106   a  and  106   b , master controller  108 , general purpose computing device  110  and projection device  112  allow pointer activity proximate to the touch surface  104  to be recorded as writing or drawing or used to the control execution of one or more application programs executed by the general purpose computing device  110 . 
     The support frame assembly  102  in this embodiment comprises four frame sections  130  that are mechanically fastened together adjacent their ends to form a generally rectangular support structure for the touch surface  104 . Each frame section  130  comprises a plurality of frame segments  132  with adjacent frame segments  132  being joined by a lockable hinge  134 . In this manner, when the support frame assembly  102  is disassembled, the frame sections  130  can be collapsed for ease of transport and storage. Legs  136  extend from the bottom frame sections  130  at laterally spaced locations and terminate at feet  138 . The feet  138  extend forwardly and rearwardly of the legs  136  by sufficient lengths so that the support frame assembly  102  is self supporting. Braces (not shown) interconnect the legs  136  and feet  138  to provide additional support. An L-shaped bracket  140  is fastened to each leg  136  intermediate its length. Each bracket  140  supports a respective one of the imaging devices  106   a  and  106   b . In this manner, the imaging devices  106   a  and  106   b  look upwardly across the touch surface  104  generally from opposite bottom corners of the touch surface. Each bracket  140  also supports a bezel retainer  142 . Each bezel retainer  142  comprises a forwardly extending post  144 . The touch surface  104  is a sheet of flexible material that is securely fastened to the back of the support frame assembly  102 . 
     Bezel guides  146  extend forwardly from the support frame assembly  102  adjacent the opposite top corners of the touch surface  104 .  FIG. 2  better illustrates one of the bezel guides  146 . In this embodiment, each bezel guide  146  is in the form of a cylindrical metal rod that is secured to the associated support frame section  130  by one or more suitable fasteners (not shown). The outer surface of each metal rod is coated with a retro-reflective surface. A pliable bezel  150  extends along three sides of the touch surface. The bezel  150  partially wraps around each of the bezel guides  146  and has its opposite ends held by the bezel retainers  142 . In this embodiment, the ends of the bezel  150  terminate in loops into which the posts  144  are inserted. The length of the bezel  150  is chosen so that the bezel  150  remains taut. 
     The bezel  150  in this embodiment is in the form of a strap formed from a synthetic fabric such as for example nylon. The strap has a length that is significantly larger than its width. The bezel  150  has an inwardly facing surface that is also coated with retro-reflective material. To take best advantage of the properties of the retro-reflective material, the bezel  150  is oriented so that its inwardly facing surface extends in a plane generally normal to that of the touch surface  104 . 
     The imaging device  106   a  positioned adjacent the bottom left corner of the touch surface  104  is oriented so that it sees the inwardly facing surface of the portion of the bezel  150  that extends between the two bezel guides  146  and between the bezel guide  150  adjacent the top right corner of the touch surface  104  and the bezel retainer  142  adjacent the bottom right corner of the touch surface  104 . Similarly, the imaging device  106   b  positioned adjacent the bottom right corner of the touch surface  104  is oriented so that it sees the inwardly facing surface of the portion of the bezel  150  that extends between the two bezel guides  146  and between the bezel guide  150  adjacent the top left corner of the touch surface  104  and the bezel retainer  142  adjacent the bottom left corner of the touch surface  104 . In this manner, the fields of view of the imaging devices  106   a  and  106   b  overlap over a region of interest encompassing the entirety of the touch surface  104 . 
     Turning now to  FIG. 3 , one of the imaging assemblies  106   a  and  106   b  is better illustrated. As can be seen, the imaging assembly comprises an image sensor  160  such as that manufactured by Micron Technology, Inc. of Boise, Id. under model no. MT9V022 fitted with an 880 nm lens  162  of the type manufactured by Boowon Optical Co. Ltd. under model no. BW25B. The lens  162  provides the image sensor  160  with a field of view that is sufficiently wide so that pointer contacts at any position on the touch surface  104  are seen by the image sensor  160 . The image sensor  160  communicates with and outputs image frame data to a first-in first-out (FIFO) buffer  164  via a data bus  166 . A digital signal processor (DSP)  168  receives the image frame data from the FIFO buffer  164  via a second data bus  170  and provides pointer data to the master controller  108  via a serial input/output port  172  when a pointer exists in image frames captured by the image sensor  160 . The image sensor  160  and DSP  168  also communicate over a bi-directional control bus  174 . An electronically programmable read only memory (EPROM)  176  which stores image sensor calibration parameters is connected to the DSP  168 . A current control module  178  is also connected to the DSP  168  as well as to an infrared (IR) light source  180  comprising one or more IR light emitting diodes (LEDs). The configuration of the LEDs of the IR light source  180  is selected to generally evenly illuminate the portion of the bezel  150  in field of view of the imaging assembly. The imaging assembly components receive power from a power supply  182 . 
       FIG. 4  better illustrates the master controller  108 . Master controller  108  comprises a DSP  200  having a first serial input/output port  202  and a second serial input/output port  204 . The master controller  108  communicates with the imaging assemblies  106   a  and  106   b  via first serial input/output port  202  over communication lines  206 . Pointer data received by the DSP  200  from the imaging assemblies  106   a  and  106   b  is processed by DSP  200  to generate pointer location data as will be described. DSP  200  communicates with the general purpose computing device  110  via the second serial input/output port  204  and a serial line driver  208  over communication lines  210 . Master controller  108  further comprises an EPROM  212  that stores interactive input system parameters. The master controller components receive power from a power supply  214 . 
     The general purpose computing device  110  in this embodiment is a computer comprising, for example, a processing unit, system memory (volatile and/or non-volatile memory), other non-removable or removable memory (e.g., a hard disk drive, RAM, ROM, EEPROM, CD-ROM, DVD, flash memory, etc.) and a system bus coupling the various computer components to the processing unit. The computer can include a network connection to access shared or remote drives, one or more networked computers, or other networked devices. 
     The interactive input system  100  is able to detect passive pointers P such as for example, a user&#39;s finger, a cylinder or other suitable object as well as active pen tools P that are brought into proximity with the touch surface  104  and within the fields of view of the imaging devices  106   a  and  106   b . For ease of discussion, the operation of the interactive input system  100 , when a passive pointer P is brought into proximity with the touch surface  104 , will be described. 
     During operation, the DSP  168  of each imaging assembly  106   a  and  106   b  generates clock signals so that the image sensor  160  of each imaging assembly captures image frames at the desired frame rate. The DSP  168  also signals the current control module  178  of each imaging assembly  106   a  and  106   b . In response, each current control module  178  connects its associated IR light source  180  to the power supply  182 . When the IR light sources  180  are on, the IR light sources  180  flood the region of interest over the touch surface  104  with infrared illumination. When the infrared illumination emitted by the IR light source  180  of imaging assembly  106   a  impinges on the portion of the bezel  150  and the bezel guides  146  within the field of view of its associated image sensor  160 , the retro-reflective material coating the inwardly facing surface of the bezel  150  and coating the bezel guides  146  reflects the infrared illumination back towards the image sensor  160 . Likewise, when the infrared illumination emitted by the IR light source  180  of imaging assembly  106   b  impinges on the portion of the bezel  150  and the bezel guides  146  within the field of view of its associated image sensor  160 , the retro-reflective material coating the inwardly facing surface of the bezel  150  and coating the bezel guides  146  reflects the infrared illumination back towards the image sensor  160 . As a result, in the absence of a pointer P within the fields of view of the image sensors  160 , the bezel  150  appears as a bright “white” band having a substantially even intensity over its length in image frames captured by the imaging assemblies  106   a  and  106   b.    
     When a pointer P is brought into proximity with the touch surface  104 , the pointer P occludes infrared illumination from impinging on the retro-reflective material coating the inwardly facing surface of the bezel  150  and/or bezel guide  146  and as a result, a dark region interrupting the bright band that represents the pointer P, appears in image frames captured by the imaging assemblies  106   a  and  106   b.    
     Each image frame output by the image sensor  160  of each imaging assembly  106   a  and  106   b  is conveyed to the DSP  168 . When the DSP  168  receives an image frame, the DSP  168  processes the image frame to detect the existence of a pointer therein and if a pointer exists, generates pointer data that identifies the position of the pointer within the image frame. The DSP  168  then conveys the pointer data to the master controller  108  via serial port  172  and communication lines  206 . 
     When the master controller  108  receives pointer data from both imaging assembles  106   a  and  106   b , the master controller  108  calculates the position of the pointer in (x,y) coordinates relative to the touch surface  104  using well known triangulation such as that described in above-incorporated U.S. Pat. No. 6,803,906 to Morrison, et al. The calculated pointer position is then conveyed by the master controller  108  to the general purpose computing device  110 . The general purpose computing device  110  in turn processes the received pointer position and updates the image data output provided to the projection device  112 , if required, so that the image presented on the touch surface  104  can be updated to reflect the pointer activity. In this manner, pointer interaction with the touch surface  104  can be recorded as writing or drawing or used to control execution of one or more application programs running on the general purpose computing device  110 . 
     Although the bezel guides  146  are described above as being in the form of generally cylindrical metal rods coated with retro-reflective material, alternatives are available. For example,  FIG. 5   a  shows an alternative bezel guide  246  extending forwardly from the support frame assembly  102 . In this embodiment, similar to the previous embodiment, the bezel guide  246  is in the form of a generally cylindrical rod secured to the associated frame section  130  by one or more suitable fasteners. The cylindrical rod however is formed of transparent material, such as for example glass or acrylic. In this manner, infrared illumination that is emitted by the IR light sources  180  passes through the bezel guide  246  and impinges on the bezel  150  that is partially wrapped around the bezel guide. The infrared illumination in turn is reflected by the retro-reflective material coating on the inwardly facing surface of the bezel  150 , back through the bezel  246  guide and toward to the imaging devices  106   a  and  106   b.    
       FIG. 5   b  show yet another alternative bezel guide  346  extending forwardly from the support frame assembly  102 . In this embodiment, the bezel guide  246  is in the form of a curved member secured to the associated frame section  130  by one or more suitable fasteners. Similar to the bezel guide  146 , the inwardly facing surface of the curved member is coated with retro-reflective material. In this manner, infrared illumination that is emitted by the IR light sources  180  and impinges on the bezel guide  346  is reflected by the retro-reflective material coating back toward to the imaging devices  106   a  and  106   b.    
       FIG. 5   c  show still yet another alternative bezel guide  446  extending forwardly from the support frame assembly  102 . In this embodiment, the bezel guide  446  is in the form of a thin, generally rectangular projection secured to the associated frame section  130  by one or more suitable fasteners. The configuration of the bezel guide  446  is such that its presence does not significantly occlude the bezel  150  during infrared illumination. As a result, the bezel guide  446  does not create a dark line in the white band normally seen by the image sensors  160  in the absence of a pointer P. 
     Rather than using a single bezel guide adjacent each top corner of the touch surface  104 , bezel guide arrangements comprising a plurality of bezel guides may be employed. For example,  FIG. 6   a  shows a bezel guide arrangement  500  comprising a plurality of bezel guides  546   a  to  546   c , in this case three (3) bezel guides extending forwardly from the support frame assembly  102 . In this embodiment, each of the bezel guides is in the form of a cylindrical metal rod that is secured to the associated frame section  130  by one or more suitable fasteners. The outer surface of the central bezel guide  546   b  is coated with a retro-reflective material. The bezel guides  546   a  to  546   c  are arranged in a row and are slightly spaced to provide gaps between adjacent bezel guides. The bezel  150  is interleaved between the bezel guides  546   a  to  546   c . As a result, the bezel  150  is held securely to the support frame assembly  102 . Interleaving the bezel  150  through the bezel guides  546   a  to  546   c  also helps to reduce slack formation in the bezel  150  and thus, inhibit sagging. 
       FIG. 6   b  shows another bezel guide arrangement  600  comprising a plurality of bezel guides  646   a  to  646   c , in this case three (3) bezel guides extending forwardly from the support frame assembly  102 . In this embodiment, each of the bezel guides  646   a  to  646   c  is also in the form of a cylindrical metal rod that is secured to the associated frame section  130  by one or more suitable fasteners. The bezel guides  646   a  to  646   c  are arranged in a triangle and are slightly spaced to provide gaps between adjacent bezel guides. The pliable bezel  150  is interleaved between the bezel guides  646   a  to  646   c  in a manner which obviates the need to coat any of the bezel guides with retro-reflective material while still holding the bezel securely to the support frame assembly  102  thereby to inhibit slack formation and sagging. 
     In the embodiment of  FIG. 1 , the bezel  150  is described as having ends that terminate in loops through which the posts  144  of the bezel retainers  142  pass. Alternative bezel configurations are however possible. For example, as shown in  FIG. 7 , rather than terminating in loops, in this embodiment, hook and loop fabric is provided adjacent one or both ends of the bezel. Each end of the bezel  150  carrying hook and loop fabric is wrapped around the post  144  of the bezel retainer and brought back into contact with itself to engage the hook and loop fabric. The releasable hook and loop fabric allows the tension of the bezel  150  to be adjusted to remove slack and inhibit sagging. 
     Turning now to  FIG. 8 , an alternative bezel guide configuration for the interactive input system  100  is shown. In this embodiment, rather than only using bezel guides adjacent the top corners of the touch surface  104 , bezel guides  746  extending forwardly from the support frame assembly  102  are also employed at spaced locations along the top of the touch surface as well as adjacent the bottom corners of the touch surface  104  to further inhibit slack formation in the bezel  150 . Similar to the embodiment of  FIG. 1 , each bezel guide  746  is in the form of a cylindrical metal rod that is secured to the associated frame section  130  by one or more suitable fasteners. The outer surface of each metal rod is coated with retro-reflective material. 
     Although the bezel is described as being formed from synthetic material such as for example nylon, other structurally suitable bezel materials such as for example, ductile metals, plastics, fabrics etc. may be employed. Also, the bezel need not be in the form of a single continuous strap. Rather, the bezel may comprise a plurality of bezel segments arranged end-to-end about the touch surface  104  and/or arranged side-to-side. 
     If desired, the bezel guides may carry retaining structure to cooperate with and retain the bezel. For example, one or more of the bezel guides may carry hook or loop fabric that cooperates with complimentary fabric on the bezel. Alternatively, one or more of the bezel guides may comprise a clamp or other suitable mechanical fastener to retain the bezel. Also, if desired, the bezel guides may be integrally formed with the frame sections  130  or secured to the frame sections  130  by other suitable means. 
     Although examples of bezel guide configurations are described above and illustrated, alternative configurations may be employed. For example, each bezel guide may comprise a plurality of flattened prongs extending forwardly from the support frame assembly with the bezel woven through the prongs. Typically, three prongs would be employed. Similar to previous embodiments, the prongs are coated with retroreflective material and are flat to mitigate shadows. 
     Different bezel retainer configurations are also possible. For example, one or both bezel retainers may comprise a ratchet or lever mechanism that receives a free end of the bezel and allows the tension applied to the bezel to be adjusted. Alternatively, one or both ends of the bezel  150  may be weighted to maintain tension in the bezel. In yet another embodiment, one or both bezel retainers may comprise a buckle and a clasp arrangement such as those commonly employed on knapsacks and other carrying cases. In this case, one of the buckle and clasp is attached to one end of the bezel and the other one of the buckle and clasp is attached to the bracket  140 . When the buckle and clasp are engaged, the bezel can be adjusted through a slider loop to allow the tension of the bezel to be adjusted. The bezel may also be formed of elasticized material to assist in maintaining tension in the bezel. 
     Turning now to  FIG. 9 , an alternative pliable bezel configuration for the interactive input system  100  is shown. In this embodiment, similar to the previous embodiment, the bezel  850  extends along three sides of the touch surface  104 . Unlike the previous embodiment however, the bezel  850  is in the form of an inflatable C-shaped element formed of two sheets of an air impermeable plastic coated fabric bonded together. The inwardly facing surface of the bezel  850  is coated with retro-reflective material. The bezel  850  is releasably fastened to the frame sections by suitable means such as for example, cooperating hook and loop fabric carried by the frame sections  130  and the bezel  850  obviating the need for the bezel retainers  142  on the brackets  140 . In this manner, the bezel  850  can be easily removed from the frame sections  130  and deflated by opening a valve member (not shown) when not in use. Alternatively, the bezel  850  may be filled with foam as described in U.S. Pat. No. 4,624,877 and U.S. Pat. No. 5,705,252 and be of similar composition to self-inflating mattresses such as the Therm-a-rest™ brand produced by Cascade Designs. 
       FIGS. 10 and 11  show an inflatable bezel and imaging device assembly  900  that is suitable for mounting on virtually any substantially flat surface. In this embodiment, the inflatable bezel and imaging device assembly  900  is secured to the frame  902  of a mobile projection screen by cooperating hook and loop fabric on the assembly  900  and frame  902 . The inflatable bezel  950  extends along all four sides of the portion of the frame surface that defines the touch surface  104 . Imaging devices  106  are positioned adjacent and accommodated by each corner of the bezel  950 . Cables extend from the imaging devices through the assembly to allow the imaging devices to be connected to the master controller  108 . The inwardly facing surface of the bezel  950  is coated with retro-reflective material  952 . In this embodiment, as the inflatable bezel and imaging device assembly  900  comprises four (4) imaging devices, pointer position coordinates are determined in the manner disclosed in above-incorporated U.S. Pat. No. 6,803,906 to Morrison, et al. 
       FIGS. 12 and 13  show yet another inflatable bezel and imaging device assembly  1000 . In this embodiment, the bezel  1050  is integrally formed with and surrounds an inflatable sheet  1052  having a surface  1054  bounded by the bezel that defines the touch surface. Imaging devices  106  are positioned adjacent and accommodated by each corner of the bezel. Cables extend from the imaging devices through the assembly to allow the imaging devices to be connected to the master controller  108 . The inwardly facing surface of the bezel  1050  is coated with retro-reflective material  1056 . In this embodiment, the bezel  1050  and inflatable sheet  1052  are filled with foam as described in U.S. Pat. No. 4,624,877 and U.S. Pat. No. 5,705,252 and are of similar composition to self-inflating mattresses such as the Therm-a-rest™ brand produced by Cascade Designs. When not in use, the inflatable sheet and bezel can be rolled into a deflated state. 
     In the embodiments described above, the inwardly facing surface of the bezel is described as being coated by retro-reflective material. If desired, rather than including a continuous retro-reflecting coating, one or more distinct bands of retro-reflective material may be provided on the inwardly facing surface of the bezel as described in U.S. Patent Application Publication No. 2009/0277694 to Hansen, et al. filed on May 9, 2008 and assigned to SMART Technologies ULC of Calgary, Alberta, the content of which is incorporated herein by reference. Alternatively, rather than using retro-reflective material, highly reflective material may be employed. The inwardly facing surface of the bezel may also be coated with material different than the retro-reflective material and highly reflective material referred to above. These coatings may comprise for example, a black coating, a light absorbing coating; a white coating, an energy reflecting coating; a film of electroluminescent or fluorescent material; a polarizing filter; an IR filter; or a combination or two or more of the aforementioned coatings. As long as the bezel provides a relatively constant background in relation to pointers brought into proximity of the touch surface  104 , it will be suitable for use. As will be appreciated by those of skill in the art, depending on the coating(s) selected for the bezel, the IR light sources  180  of the imaging devices may or may not be required. To facilitate assembly of the interactive input system  100 , regardless of the coating(s) selected for the bezel, opposite sides of the bezel may be coated in a substantially identical manner so that the bezel does not need to be oriented in any specific manner during assembly of the interactive input system  100 . 
     To reduce the effects of ambient light, the light emitted by the light sources  180  may be modulated as described in U.S. Patent Application Publication No. 2009/0278794 to McReynolds, et al. filed on May 9, 2008 and assigned to SMART Technologies ULC of Calgary, Alberta, the content of which is incorporated herein by reference. To reduce the amount of data to be processed, only the area of the image frames occupied by the bezel need be processed. A bezel finding procedure similar to that described in the above-incorporated Hansen, et al. published U.S. patent application, may be employed to locate the bezel in captured image frames. Of course, those of skill in the art will appreciate that other suitable techniques may be employed to locate the bezel in captured image frames. 
     Although the support frame assembly  102  is described as being self-supporting, if desired, the support frame assembly can be configured to be attached to a display unit (not shown) such as for example, a plasma television, a liquid crystal display (LCD) device, a flat panel display device, a cathode ray tube monitor etc. and surrounds the display surface  124  of the display unit. In this case, the image data output by the general purpose computing device  110  is fed to the display unit obviating the need for the touch surface sheet or the projection device  112 . 
     Alternatively, the support frame assembly may be configured to be attached to a support surface such as for example, a wall surface or the side of an emergency service or military vehicle. As will be appreciated in this case, the feet are removed from the legs and the length of the legs can be shortened. 
     Although the light sources of the imaging assemblies  180  are described as comprising IR LEDs, those of skill in the art will appreciate that the imaging devices may include different IR light sources. The light sources of the imaging assemblies alternatively may comprise light sources that emit light at a frequency different than infrared. As will be appreciated using light sources that emit non-visible light is preferred to avoid the light emitted by the light sources from interfering with the images presented on the touch surface  104 . 
     Those of skill in the art will also appreciate that other processing structures could be used in place of the master controller and general purpose computing device. For example, the master controller could be eliminated and its processing functions could be performed by the general purpose computing device. Alternatively, the master controller could be configured to process the image frame data output by the image sensors both to detect the existence of a pointer in captured image frames and to triangulate the position of the pointer. Rather than using a separate master controller  108 , the functionality of the master controller  108  may be embodied in the DSP  168  of one of the imaging devices. Although the imaging devices and master controller are described as employing DSPs, other processors such as microcontrollers, central processing units (CPUs), graphics processing units (GPUs), or cell-processors could be used. 
     Although embodiments have been described, those of skill in the art will appreciate that other variations and modifications may be made without departing from the spirit and scope thereof as defined by the appended claims.