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 bezel at least partially surrounds the region of interest. The bezel comprises a multi-angle reflecting structure to reflect emitted radiation from the at least one radiation source towards the at least one imaging device.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to interactive input systems and in particular, to an interactive input system incorporating multi-angle reflecting structure. 
       BACKGROUND OF THE INVENTION 
       [0002]    Interactive input systems that allow users to inject input (eg. digital ink, mouse events etc.) into an application program using an active pointer (eg. a pointer that emits light, sound or other signal), a passive pointer (eg. a finger, cylinder or other suitable object) or other suitable input device such as for example, a mouse or trackball, 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. 
         [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 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 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. 
         [0004]    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 evenly the region over the touch surface. For example, U.S. Pat. No. 6,972,401 to Akitt et al. issued on Dec. 6, 2005 and 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 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. 
         [0005]    For example, U.S. Pat. No. 7,283,128 to Sato discloses a coordinate input apparatus including 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. 
         [0006]    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 coordinate input region. As a result, the possibility of false pointer contacts and/or missed pointer contacts is increased. As will be appreciated, improvements in illumination for machine vision interactive input systems are desired. 
         [0007]    It is therefore an object of the present invention to provide a novel interactive input system incorporating multi-angle reflecting structure. 
       SUMMARY OF THE INVENTION 
       [0008]    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 bezel at least partially surrounding said region of interest, said bezel comprising a multi-angle reflecting structure to reflect emitted radiation from said at least one radiation source towards said at least one imaging device. 
         [0009]    In one embodiment, the multi-angle reflecting structure comprises at least one series of reflective elements extending along the bezel. The reflective elements are configured to reflect emitted radiation from the at least one radiation source towards the at least one imaging device. Each reflective element is of a size smaller than the pixel resolution of the at least one imaging device and presents a reflective surface that is angled to reflect emitted radiation from the at least one radiation source towards the at least one imaging device. The reflecting surface may be generally planar, generally convex, or generally concave. The configuration of the reflective surfaces may also vary over the length of the bezel. 
         [0010]    In one embodiment, the at least one radiation source is positioned adjacent the at least one imaging device and emits non-visible radiation such as for example infrared radiation. In this case, the at least one radiation source comprises one or more infrared light emitting diodes. 
         [0011]    In one embodiment, the bezel comprises a backing and a film on the backing with the film being configured by machining and engraving to form the multi-angle reflecting structure. 
         [0012]    In one embodiment, the interactive input system comprises at least two imaging devices with the imaging devices looking into the region of interest from different vantages and having overlapping fields of view. Each section of the bezel seen by an imaging device comprises a multi-angle reflecting structure to reflect emitted radiation from the at least one radiation source towards that imaging device. Each section of the bezel seen by more than one imaging device comprises a multi-angle reflecting structure for each imaging device. The interactive input system may further comprise processing structure communicating with the imaging devices and processing image data output thereby to determine the location of a pointer within the region of interest. 
         [0013]    According to another aspect there is provided a bezel for an interactive touch surface comprising a multi-angled reflector comprising at least one series of reflective surfaces extending along the bezel, each reflecting surface being oriented to reflect radiation toward at least one imaging device. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    Embodiments will now be described more fully with reference to the accompanying drawings in which: 
           [0015]      FIG. 1  is a schematic diagram of an interactive input system; 
           [0016]      FIG. 2  is a schematic diagram of an imaging assembly forming part of the interactive input system of  FIG. 1 ; 
           [0017]      FIG. 3  is a schematic diagram of a master controller forming part of the interactive input system of  FIG. 1 ; 
           [0018]      FIG. 4  is a front elevational view of an assembly forming part of the interactive input system of  FIG. 1  showing the fields of view of imaging devices across a region of interest; 
           [0019]      FIG. 5A  is a front elevational view of a portion of the assembly of  FIG. 4  showing a bezel segment comprising a multi-angle reflector; 
           [0020]      FIGS. 5B and 5C  are top plan and front elevation views of the multi-angle reflector shown in  FIG. 5A ; 
           [0021]      FIG. 6  is an enlarged view of a portion of  FIG. 1  showing a portion of another bezel segment forming part of the assembly of  FIG. 4 ; 
           [0022]      FIG. 7  is an isometric view of the bezel segment portion of  FIG. 6 ; 
           [0023]      FIG. 8  is a top plan view of the bezel segment portion of  FIG. 7 ; 
           [0024]      FIGS. 9A and 9B  are top plan and front elevation views of a multi-angle reflector forming part of the bezel segment portion of  FIG. 7 ; 
           [0025]      FIGS. 9C and 9D  are top plan and front elevation views of another multi-angle reflector forming part of the bezel segment portion of  FIG. 7 ; 
           [0026]      FIG. 10A  is a front elevation view of the bezel segment portion of  FIG. 7 ; 
           [0027]      FIGS. 10B and 10C  are front elevation views of alternative bezel segments; 
           [0028]      FIGS. 10D and 10E  are isometric and top plan views of yet another bezel segment; 
           [0029]      FIG. 11A  is a schematic diagram of an alternative assembly for use in an interactive input system; 
           [0030]      FIG. 11B  is a schematic diagram of an equivalent assembly to that shown in  FIG. 11A ; 
           [0031]      FIG. 12  is a schematic diagram of yet another assembly for use in an interactive input system; 
           [0032]      FIGS. 13A and 13B  are top plan and front elevation views of a multi-angle reflector employed in the assembly of  FIG. 12 ; 
           [0033]      FIGS. 13C and 13D  are top plan and front elevation views of another multi-angle reflector employed in the assembly of  FIG. 12 ; and 
           [0034]      FIG. 14  is an isometric view of a laptop computer embodying a multi-angle reflector. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0035]    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 an assembly  122  that engages 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 display or monitor etc. and surrounds the display surface  124  of the display unit. The assembly  122  employs machine vision to detect pointers brought into proximity with the display surface  124  and communicates with a master controller  126 . The master controller  126  in turn communicates with a general purpose computing device  128  executing one or more application programs. General purpose computing device  128  processes the output of the assembly  122  and provides display output to a display controller  130 . Display controller  130  controls the image data that is fed to the display unit so that the image presented on the display surface  124  reflects pointer activity. In this manner, the assembly  122 , master controller  126 , general purpose computing device  128  and video controller  130  allow pointer activity proximate to the display surface  124  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  128 . 
         [0036]    Assembly  122  comprises a frame assembly that is mechanically attached to the display unit and surrounds the display surface  124 . Frame assembly comprises a bezel having three bezel segments  140 ,  142  and  144 . Bezel segments  140  and  142  extend along opposite side edges of the display surface  124  while bezel segment  144  extends along the bottom edge of the display surface  124 . Imaging assemblies  160  and  162  are positioned adjacent the top left and top right corners of the assembly  122  and are oriented so that their fields of view (FOV) overlap and look generally across the entire display surface  124  as shown in  FIG. 4 . The bezel segments  140 ,  142  and  144  are oriented so that their inwardly facing surfaces are generally normal to the plane of the display surface  124 . In this embodiment, imaging assembly  160  sees bezel segments  142  and  144  and imaging assembly  162  sees bezel segments  140  and  144 . Thus, the bottom bezel segment  144  is seen by both imaging assemblies  160  and  162  while the bezel segments  140  and  142  are only seen by one imaging assembly. 
         [0037]    Turning now to  FIG. 2 , one of the imaging assemblies  160 ,  162  is better illustrated. As can be seen, the imaging assembly comprises an image sensor  170  such as that manufactured by Micron Technology, Inc. of Boise, Id. under model no. MT9V022 fitted with an 880 nm lens  172  of the type manufactured by Boowon Optical Co. Ltd. under model no. BW25B. The lens  172  provides the image sensor  170  with a 98 degree field of view so that the entire display surface  124  is seen by the image sensor. The image sensor  170  communicates with and outputs image frame data to a first-in first-out (FIFO) buffer  174  via a data bus  176 . A digital signal processor (DSP)  178  receives the image frame data from the FIFO buffer  174  via a second data bus  180  and provides pointer data to the master controller  126  via a serial input/output port  182  when a pointer exists in image frames captured by the image sensor  170 . The image sensor  170  and DSP  178  also communicate over a bi-directional control bus  184 . An electronically programmable read only memory (EPROM)  186  which stores image sensor calibration parameters is connected to the DSP  178 . A current control module  188  is also connected to the DSP  178  as well as to an infrared (IR) light source  190  comprising one or more IR light emitting diodes (LEDs). The configuration of the LEDs of the IR light source  190  is selected to generally evenly illuminate the bezel segments in field of view of the imaging assembly. The imaging assembly components receive power from a power supply  192 . 
         [0038]      FIG. 3  better illustrates the master controller  126 . Master controller  126  comprises a DSP  200  having a first serial input/output port  202  and a second serial input/output port  204 . The master controller  126  communicates with imaging assemblies  160  and  162  via first serial input/output port  20  over communication lines  206 . Pointer data received by the DSP  200  from the imaging assemblies  160  and  162  is processed by DSP  200  to generate pointer location data as will be described. DSP  200  communicates with the general purpose computing device  128  via the second serial input/output port  204  and a serial line driver  208  over communication lines  210 . Master controller  126  further comprises an EPROM  212  that stores interactive input system parameters. The master controller components receive power from a power supply  214 . 
         [0039]    The general purpose computing device  128  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 (eg. 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. 
         [0040]      FIG. 5A  shows the bezel segment  142  that is seen by the imaging assembly  160 . In this embodiment as best illustrated in  FIGS. 4 ,  5 A,  5 B and  5 C, bezel segment  142  comprises a backing  142   a  having an inwardly directed surface on which a plastic film  142   b  is disposed. The plastic film  142   b  is machined and engraved to form a faceted multi-angle reflector. The facets of the multi-angle reflector define a series of highly reflective, generally planar mirror elements  142   c  extending along the length of the plastic film. The angle of each minor element  142   c  is selected so that light emitted by the IR light source  190  of imaging assembly  160  indicated by dotted lines  250  is reflected back towards the image sensor  170  of imaging assembly  160  as indicated by dotted lines  252 . The size of each mirror element  142   c  is also selected so that it is smaller than the pixel resolution of the image sensor  170  of the imaging assembly  160 . In this embodiment, the mirror elements  142   c  are in the sub-micrometer range. In this manner, the mirror elements  142   c  do not reflect discrete images of the IR light source  190  back to the image sensor  170 . Forming microstructures, such as the mirror elements  142   c , on plastic film  142   b  is a well known technology. As a result, the multi-angle reflector can be formed with a very high degree of accuracy and at a reasonably low cost. 
         [0041]    The bezel segment  140  is a mirror image of bezel segment  142  and similarly comprises a backing  140   a  having a machined and engraved plastic film  140   b  on its inwardly directed surface that forms a faceted multi-angle reflector. The facets of the multi-angle reflector define a series of highly reflective, generally planar mirror elements extending along the length of the plastic film. In this case however, the angle of each mirror element is selected so that light emitted by the IR light source  190  of imaging assembly  162  is reflected back towards the image sensor  170  of imaging assembly  162 . 
         [0042]    Bezel segment  144  that is seen by both imaging assemblies  160  and  162  has a different configuration than bezel segments  140  and  142 . Turning now to  FIGS. 4 and 6  to  10 A, the bezel segment  144  is better illustrated. As can be seen, bezel segment  144  comprises a backing  144   a  having an inwardly directed surface that is generally normal to the plane of the display surface  124 . Plastic film bands  144   b  positioned one above the other are disposed on the backing  144   a . The bands may be formed on a single plastic strip disposed on the backing  144   a  or may be formed on individual strips disposed on the backing. In this embodiment, the plastic film band positioned closest to the display surface  124  is machined and engraved to form a faceted multi-angle reflector  300  that is associated with the imaging assembly  162 . The other plastic film band is machined and engraved to form a faceted multi-angle reflector  302  that is associated with the imaging assembly  160 . 
         [0043]    The facets of the multi-angle reflector  300  define a series of highly reflective, generally planar mirror elements  300   a  that are angled to reflect lighted emitted by the IR light source  190  of the imaging assembly  162  towards the image sensor  170  of the imaging assembly  162  as indicated by dotted lines  310 . The faces  300   b  of the multi-angle reflector  300  that are seen by the imaging assembly  160  are configured to reduce the amount of light that is reflected by the faces  300   b  back towards the imaging assembly  160 . For example, the faces  300   b  may be coated with a non-reflective coating such as paint, textured to reduce their reflectivity etc. Similar to bezel segments  140  and  142 , the size of each mirror element  300   a  is selected so that it is smaller than the pixel resolution of the image sensor  170  of the imaging assembly  162 . 
         [0044]    The facets of the multi-angle reflector  302  also define a series of highly reflective, generally planar mirror elements  302   a  that are angled to reflect lighted emitted by the IR light source  190  of the imaging assembly  160  towards the image sensor  170  of the imaging assembly  160  as indicated by dotted lines  312 . The faces  302   b  of the multi-angle reflector  302  that are seen by the imaging assembly  162  are similarly configured to reduce the amount of light that is reflected by the faces  302   b  back towards the imaging assembly  162 . For example, the faces  302   b  may be coated with a non-reflective coating such as paint, textured to reduce their reflectivity etc. The size of each minor element  302   a  is selected so that it is smaller than the pixel resolution of the image sensor  170  of the imaging assembly  162 . 
         [0045]    During operation, the DSP  178  of each imaging assembly  160 ,  162  generates clock signals so that the image sensor  170  of each imaging assembly captures image frames at the desired frame rate. The DSP  178  also signals the current control module  188  of each imaging assembly  160 ,  162 . In response, each current control module  188  connects its associated IR light source  190  to the power supply  192 . When the IR light sources  190  are on, each LED of the IR light sources  190  floods the region of interest over the display surface  124  with infrared illumination. For imaging assembly  160 , infrared illumination emitted by its IR light source  190  that impinges on the minor elements  142   c  of the bezel segment  142  and on the mirror elements  302   a  of bezel segment  144  is returned to the image sensor  170  of the imaging assembly  160 . As a result, in the absence of a pointer P within the field of view of the image sensor  170 , the bezel segments  142  and  144  appear as a bright “white” band having a substantially even intensity over its length in image frames captured by the imaging assembly  160 . Similarly, for imaging assembly  162 , infrared illumination emitted by its IR light source  190  that impinges on the minor elements  140   c  of the bezel segment  140  and on the minor elements  300   a  of bezel segment  144  is returned to the image sensor  170  of the imaging assembly  162 . As a result, in the absence of a pointer P within the field of view of the image sensor  170 , the bezel segments  140  and  144  appear as a bright “white” band having a substantially even intensity over its length in image frames captured by the imaging assembly  162 . 
         [0046]    When a pointer is brought into proximity with the display surface  124 , the pointer occludes infrared illumination and as a result, a dark region interrupting the bright band that represents the pointer, appears in image frames captured by the imaging assemblies  160 ,  162 . 
         [0047]    Each image frame output by the image sensor  170  of each imaging assembly  160 ,  162  is conveyed to the DSP  178 . When the DSP  178  receives an image frame, the DSP  178  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  178  then conveys the pointer data to the master controller  126  via serial port  182  and communication lines  206 . 
         [0048]    When the master controller  126  receives pointer data from both imaging assembles  160  and  162 , the master controller calculates the position of the pointer in (x,y) coordinates relative to the display surface  124  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  126  to the general purpose computing device  128 . The general purpose computing device  128  in turn processes the received pointer position and updates the image output provided to the video controller  130 , if required, so that the image presented on the display surface  124  can be updated to reflect the pointer activity. In this manner, pointer interaction with the display surface  124  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  128 . 
         [0049]    Although the bezel segment  144  is described above as including two bands positioned one above the other, alternatives are available. For example,  FIG. 10B  shows an alternative bezel segment  444  comprising a backing having an inwardly directed surface that is generally normal to the plane of the display surface  124 . Four plastic film bands  444   b  positioned one above the other are disposed on the backing. The bands may be formed on a single plastic strip disposed on the backing or may be formed on individual strips disposed on the backing. In this embodiment, the odd plastic film bands, when starting with the plastic band positioned closest to the display surface  124 , are machined and engraved to form faceted multi-angle reflectors  500  that are associated with the imaging assembly  162 . The even plastic film bands, when starting with the plastic band positioned closest to the display surface  124 , are machined and engraved to form faceted multi-angle reflectors  502  that are associated with the imaging assembly  160 . The multi-angle reflectors  500  define a series of highly reflective, generally planar mirror elements  500   a  that are angled to reflect light emitted by the IR light source  190  of imaging assembly  162  back towards the image sensor  170  of imaging assembly  162 . Similarly, the multi-angle reflectors  502  define a series of highly reflective, generally planar mirror elements  502   a  that are angled to reflect light emitted by the IR light source  190  of imaging assembly  160  back towards the image sensor  170  of imaging assembly  160 . By using an increased number of bands configured as multi-angle reflectors, the bezel segment  444  appears more evenly illuminated when viewed by the imaging devices  160  and  162 . 
         [0050]      FIG. 10C  yet another bezel segment  544  comprising a backing having an inwardly directed surface that is generally normal to the plane of the display surface  124 . Twelve plastic film bands positioned one above the other are disposed on the backing. The bands may be formed on a single plastic strip disposed on the backing or may be formed on individual strips disposed on the backing. In this embodiment, the odd plastic film bands, when starting with the plastic band positioned closest to the display surface  124 , are machined and engraved to form faceted multi-angle reflectors  600  that are associated with the imaging assembly  162 . The even plastic film bands, when starting with the plastic band positioned closest to the display surface  124 , are machined and engraved to form faceted multi-angle reflectors  602  that are associated with the imaging assembly  160 . The multi-angle reflectors  600  define a series of highly reflective, generally planar mirror elements  600   a  that are angled to reflect light emitted by the IR light source  190  of imaging assembly  162  back towards the image sensor  170  of imaging assembly  162 . Similarly, the multi-angle reflectors  602  define a series of highly reflective, generally planar mirror elements  602   a  that are angled to reflect light emitted by the IR light source  190  of imaging assembly  160  back towards the image sensor  170  of imaging assembly  160 . 
         [0051]      FIGS. 10D and 10E  show yet another bezel segment  644  comprising a backing having an inwardly directed surface that is generally normal to the plane of the display surface. In this embodiment, the bezel segment  644  comprises a single plastic band that is machined and engraved to provide two sets of generally planar mirror elements, with the mirror elements of the sets being alternately arranged along the length of the bezel segment  644 . The mirror elements  650  of one set are angled to reflect light back towards the image sensor  170  of imaging assembly  160  and the mirror elements  652  of the other set are angled to reflect light back towards the image sensor  170  of imaging assembly  162 . 
         [0052]      FIG. 11A  shows an alternative assembly  722  for the interactive input system  100 . Similar to the previous embodiment, the assembly comprises a frame assembly that is mechanically attached to the display unit and surrounds the display surface  124 . Frame assembly comprises a bezel having two bezel segments  742  and  744 . Bezel segment  742  extends along one side edge of the display surface  124  while bezel segment  744  extends along the bottom edge of the display surface  124 . A single imaging assembly  760  is positioned adjacent the top left corner of the assembly  722  and is oriented so that its field of view looks generally across the entire display surface  124 . The bezel segments  742  and  744  are oriented so that their inwardly facing surfaces are generally normal to the plane of the display surface  124 . In this embodiment, the imaging assembly  160  sees both bezel segments  742  and  744 . 
         [0053]    Each bezel segment comprises a backing having an inwardly directed surface that is generally normal to the plane of the display surface  124 . A machined and engraved plastic film is provided on the inwardly directed surface of each backing so that the plastic films define a highly reflective surface that mimics a curved mirror similar to that shown in  FIG. 11B  so that light emitted by the IR light source  790  of the imaging assembly  760  is reflected back towards the image sensor  770  of the imaging assembly  760  as indicated by the dotted lines  800 . The profiles of the machined and engraved plastic films are based on the same principle as creating a Fresnel lens from a conventional plano-convex lens. Each plastic film can be thought of as a curved lens surface that has been divided into discrete, an offset lens element. The highly reflective surface is configured so that light emitted by the IR light source of the imaging assembly is reflected back towards the image sensor of the imaging assembly. 
         [0054]      FIG. 12  shows yet another assembly  822  for the interactive input system  100 . Similar to the first embodiment, the assembly comprises a frame assembly that is mechanically attached to the display unit and surrounds the display surface  124 . Frame assembly comprises a bezel having three bezel segments  840 ,  842  and  844 . Bezel segments  840  and  842  extend along opposite side edges of the display surface  124  while bezel segment  844  extends along the bottom edge of the display surface  124 . Imaging assemblies  860  and  862  are positioned adjacent the top left and top right corners of the assembly  822  and are oriented so that their fields of view overlap and look generally across the entire display surface  124 . The bezel segments  840 ,  842  and  844  are oriented so that their inwardly facing surfaces are generally normal to the plane of the display surface  124 . In this embodiment, imaging assembly  860  sees bezel segments  842  and  844  and imaging assembly  862  sees bezel segments  840  and  844 . Thus, the bottom bezel segment  844  is seen by both imaging assemblies  860  and  862  while the bezel segments  840  and  842  are only seen by one imaging assembly. 
         [0055]    In this embodiment, the construction of the bezel segments  840  and  842  is the same as the first embodiment. The bezel segment  840  is a mirror image of bezel segment  842 . As a result, the bezel segment  840  reflects light emitted by the IR light source  890  of the imaging assembly  862  back towards the image sensor  870  of the imaging assembly  862  and the bezel segment  842  reflects light emitted by the IR light source  890  of the imaging assembly  860  back towards the image sensor  870  of the imaging assembly  860 . The plastic films of the bezel segments are similarly machined and engraved to form faceted multi-angle reflectors, each defining a series of highly reflective mirror elements extending the length of the bezel segment. The mirror elements in this embodiment however have a different configuration than in the previous embodiments. In particular, the sizes of the highly reflective mirror elements defined by the multi-angle reflectors vary over the length of the bezel segment, in this case decrease in a direction away from the imaging assembly that is proximate to the bezel segment. 
         [0056]    The construction of the bezel segment  844  is also the same as the first embodiment. As a result, the plastic band of the bezel segment  844  nearest the display surface reflects light emitted by the IR light source  890  of the imaging assembly  862  back towards the image sensor  870  of the imaging assembly  862  and the other plastic band of the bezel segment  844  reflects light emitted by the IR light source  890  of the imaging assembly  860  back towards the image sensor  870  of the imaging assembly  860 . The plastic bands of the bezel segment  844  are similarly machined and engraved to form faceted multi-angle reflectors, each defining a series of highly reflective mirror elements extending the length of the bezel segment. The mirror elements in this embodiment however have a different configuration than in the previous embodiments. In particular, the sizes of the highly reflective mirror elements defined by the multi-angle reflectors decrease in a direction away from the imaging assembly to which the mirror elements reflect light as shown in  FIGS. 13A to 13D . 
         [0057]    Turning now to  FIG. 14 , a laptop computer employing a faceted multi-angle reflector  902  is shown and is generally identified by reference numeral  900 . As can be seen, the laptop computer  900  comprises a base component  904  that supports a keyboard  906  and a mouse pad  908  and that accommodates the laptop computer electronics and power supply. A lid component  910  that accommodates a liquid crystal display  912  is hingedly connected to the base component  904 . The faceted multi-angle reflector  902  is supported by the lid component  910  and extends along the bottom edge of the display  912 . A camera  922  having an associated light source is supported by the lid component  910  and is positioned adjacent the top center of the display  912 . A prism  924  is positioned in front of the camera  922  to re-direct the field of view of the camera towards the multi-angle reflector  902 . The field of view of the camera  922  is selected to encompass generally the entire display  912 . Similar to the previous embodiments, the facets of the multi-angle reflector  902  define a series of highly reflective mirror elements that are angled to direct light emitted by the light source back towards the camera  922 . In this manner, pointer contacts on the display  912  can be captured in image frames acquired by the camera  922  and processed by the laptop computer electronics allowing the display  912  to function as an interactive input surface. Of course those of skill in the art will appreciate that the multi-angle reflector may be used with the display of other computing devices such as for example, notebook computers, desktop computers, personal digital assistants (PDAs), tablet PCs, cellular telephones etc. 
         [0058]    To reduce the amount of data to be processed, only the area of the image frames occupied by the bezel segments need be processed. A bezel finding procedure similar to that described in U.S. patent application Ser. No. 12/118,545 to Hansen et al. entitled “Interactive Input System and Bezel Therefor” filed on May 9, 2008 and assigned to SMART Technologies ULC of Calgary, Alberta, the content of which is incorporated herein by reference, may be employed to locate the bezel segments 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 segments in captured image frames. 
         [0059]    Although the frame assembly is described as being attached to the display unit, those of skill in the art will appreciate that the frame assembly may take other configurations. For example, the frame assembly may be integral with the bezel  38 . If desired, the assemblies may comprise their own panels to overlie the display surface  124 . In this case, it is preferred that the panel be formed of substantially transparent material so that the image presented on the display surface  124  is clearly visible through the panel. The assemblies can of course be used with a front or rear projection device and surround a substrate on which the computer-generated image is projected or can be used separate from a display device as an input device. 
         [0060]    In the embodiments described above, the mirror elements of the faceted multi-angle reflectors are described as being generally planar. Those of skill in the art will appreciate that the mirror elements may take alternative configurations and the configuration of the mirror elements may vary along the length of the bezel segment. For example, rather than planar mirror elements, the mirror elements may present convex or concave surfaces towards the imaging assemblies. 
         [0061]    Although the light sources of the imaging assemblies 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 display surface  124 . Also, although the light sources are shown as being located adjacent the imaging devices, alternative arrangements are possible. The light sources and imaging devices do not need to be positioned proximate one another. For example, a single light source positioned between the imaging devices may be used to illuminate the bezel segments. 
         [0062]    Those of skill in the art will appreciate that although the imaging assemblies are described being positioned adjacent the top corners of the display surface and oriented to look generally across the display surface, the imaging assemblies may be located at other positions relative to the display surface  124 . 
         [0063]    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. Although the imaging assemblies 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. 
         [0064]    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.