Abstract:
An eraser is usable in a display system having a display surface. The eraser includes one or more optical detection elements for determining the coordinates of the eraser relative to the display surface.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This Application is a continuation application claiming priority under 35 U.S.C. §120 to U.S. Non-provisional patent application Ser. No. 12/174,398, filed 16 Jul. 2008, which claims priority under 35 U.S.C. §119 to U.S. Provisional Patent Application No. 61/061,381 filed 13 Jun. 2008. The entire contents and substance of both of these priority applications is incorporated by reference as if fully set out below. 
    
    
     BACKGROUND 
     Embodiments of the present invention relate to an eraser system for use with an a display system having a display surface with optical detection elements. In particular, exemplary embodiments relate to an eraser for use with an electronic whiteboard assembly with two or more optical detection elements for determining the coordinates of the eraser relative to its display surface. 
     Whiteboards are a well-known medium for facilitating the exchange of information by providing a convenient surface upon which notes, drawings, charts, or other notations may be made. As with the traditional chalkboard, whiteboards allow notations to be made in multiple colors and to then be erased. Whiteboards offer several advantages over chalkboards including a clean white surface that provides for greater contrast over the traditional green or black background of chalkboards. In addition, writing on a whiteboard is easier for many than on the traditional chalkboard. For example, the smooth writing surface of the whiteboard allows easy use of the erasable felt tip markers used on whiteboards, whereas the chalkboard surface provides a somewhat scratchy surface to hold the chalk used for writing on such surfaces. In addition, many users prefer a whiteboard to a chalkboard simply because the marker may be gripped easier than chalk and does not mark the user&#39;s hand when gripped. 
     Recently, electronic whiteboards have been developed to allow the user&#39;s writings and notations entered upon the display surface of the whiteboard to be electronically captured and transmitted to a computer for storage, display, and manipulation. Such electronic whiteboards allow the images and notations made upon the whiteboard to be saved in the computer, to be displayed, printed, transmitted, or manipulated. 
     Yet, depending on the methods and devices used in the electronic whiteboard systems for detecting the position of an input device or, for example, an erasing device, some difficulty has been had in accurately detecting the location and orientation of the erasing device. Conventional electronic whiteboard systems provide such erasing devices for erasing digital markings of a pen or stylus, but as noted, erasing devices for such systems come with a number of disadvantages. 
     Various methods and devices for detecting the position of an input device/erasing device relative to the display surface of an electronic whiteboard have been previously developed. For example, position or pressure sensing input devices using tactile sensors have been employed in conventional electronic whiteboard systems. These conventional approaches, however, often are complex, difficult, or expensive to manufacture, and/or have limited performance, especially for large area input device applications. Camera-based systems are also known. Yet, eraser devices useful with camera-based systems are typically circular, to overcome orientation identification issues. 
     Rectangular erasers are traditionally provided for conventional non-electronic whiteboards, and are beneficial because they allow a user to erase either a large swath or a smaller portion with a single stroke, depending on how the eraser is oriented in the plane of the whiteboard surface. On the other hand, electronic whiteboard systems generally implement circular erasers. Rectangular erasers, while beneficial, require the electronic whiteboard system to determine the orientation as well as the placement of the eraser, as the area of erasure depends on both these variables. In contrast, orientation of a circular eraser is irrelevant because a circle covers the same space regardless of orientation. The user of an electronic whiteboard system with a circular eraser, however, may not be able to vary the size of the area erased in a single stroke. These circular erasers are large enough to erase the board easily, but may be unable to erase a single word, or are small enough to erase a word, but take an immense amount of effort to erase a large board. 
     With electronic whiteboard systems with optical detection elements, or camera-based systems, it is difficult to judge the orientation of a conventional rectangular eraser. For example,  FIGS. 1A-1B  illustrate that it is difficult to ascertain if the eraser is horizontally (position A) or vertically (position B) oriented. Such a two-potential-orientation-state eraser, identified herein as “eraser ghosting,” is problematic, as proper erasure cannot be determined with definiteness. Each of the two eraser orientations presents two different user-intended erasure areas. 
     While conventional electronic whiteboard designs increase the versatility and useability of the traditional whiteboard, a need continues to exist for an electronic whiteboard with improved means for detecting input on the display surface from a user, associating the input with an image displayed on the whiteboard, and improved means for detecting an erasing device for accurate erasure of such inputs from the display surface. The embodiments described below are directed to these and other improvements over conventional systems, and namely to a rectangular eraser designed to be used with an optical electronic whiteboard, which can provide the system with accurate orientation information. 
     SUMMARY 
     Embodiments of the present invention are directed to an eraser useful with an electronic whiteboard system and assembly with optical detection elements. The electronic whiteboard system includes a writing/display surface and a retro-reflective perimeter surrounding the edge of the surface. A user can mark upon the surface or interact with an image displayed on the surface using an input device. The perimeter can reflect light beams emitted from optical detection elements located at the corners of the surface to identify the position of the input device relative to the writing surface and/or projected image. 
     In an exemplary embodiment, the electronic whiteboard system can comprise a writing surface, a first optical detection element in communication with the writing surface, and a second optical detection element in communication with the writing surface. For example, the two optical detection elements can be coupled to the corners of the writing surface and detect an input device by measuring decreases in the intensity of light emitted from the optical detection elements and reflected back by a retro-reflective perimeter surrounding the writing surface. 
     In an exemplary embodiment, an optical electronic whiteboard comprises two cameras located at opposite corners along one edge of the whiteboard surface, and a reflecting means that runs around the three perimeter edges not including the perimeter edge between the two cameras. An illumination source (at each camera in an exemplary embodiment) illuminates the reflectors. 
     Light travels from an illumination source to the reflective edges and back to the camera. When no object is on the board, a camera sees a continuous light pattern encircling the board. When an object (finger, stylus, marker, or eraser) touches the board, it penetrates the light path, interrupting it. The camera can thereby determine the angular position of the object across its field of view. With two or more cameras, an exact (X, Y) location of the object can easily be triangulated. 
     Embodiments of the eraser can comprise an eraser pad and a mounting block, optionally with a separate handle for ease of holding/manipulating. The mounting block can have a plurality, preferably four, faceted interior “windows”. Each interior window can comprise a reflector, such that at any point in time, at least one of the two or more cameras of the system can “see” at least one reflector, wherein eraser ghosting is eliminated. The windows can be located behind an infrared transmissive and visible light-blocking cover when infrared light is used for the coordinate detection. 
     These and other features as well as advantages, which characterize various exemplary embodiments of the present invention, will be apparent from a reading of the following detailed description and a review of the associated drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A and 1B  illustrate a conventional problem of accurately determining the orientation of a conventional rectangular eraser when used with an optically sensing electronic whiteboard system. 
         FIG. 2  illustrates an electronic whiteboard system, in accordance with an exemplary embodiment of the present invention. 
         FIG. 3  illustrates an electronic whiteboard system for use with a projector, in accordance with an exemplary embodiment of the present invention. 
         FIG. 4A  illustrates a bottom of an eraser, in accordance with an exemplary embodiment of the present invention. 
         FIG. 4B  illustrates a perspective view of the eraser, in accordance with an exemplary embodiment of the present invention. 
         FIG. 4C  illustrates a bottom view of the eraser, in accordance with an exemplary embodiment of the present invention. 
         FIG. 5  illustrates a conventional problem of accurately determining the orientation of a conventional rectangular eraser when used with an exemplary embodiment of an electronic whiteboard system. 
         FIGS. 6A and 6B  illustrate how an exemplary embodiment of the present invention properly identifies the orientation of an eraser, in accordance with an exemplary embodiment of the present invention. 
         FIGS. 7A-12C  illustrate exemplary embodiments of an eraser, in accordance with an exemplary embodiment of the present invention. 
         FIG. 13  illustrates a cone of accurate reflection of a retro-reflector, in accordance with an exemplary embodiment the present invention. 
         FIGS. 14A-B  illustrate cones of accurate reflection for various configurations of retro-reflective portions of windows of an eraser, in accordance with exemplary embodiments the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now in detail to the drawing figures, wherein like reference numerals represent like parts throughout the several views,  FIG. 2  illustrates an exemplary embodiment of an electronic whiteboard system  100 . The electronic whiteboard system  100  can comprise a display surface  110 , a perimeter  120 , and one or more optical detection elements. In the exemplary embodiment illustrated, the electronic whiteboard system  100  comprises a first optical detection element  130   a  and a second optical detection element  130   b . For viewing ease, the electronic whiteboard system  100  can be vertically mounted on a surface such as a wall. 
     In an exemplary embodiment, the display surface  110  can be substantially similar to the writing surface of a conventional dry erase whiteboard. A user can provide an input onto the display surface  110  using an input device  140 . The input device can be a felt tip-marker, a pointer, a stylus, the user&#39;s finger, an eraser, or other suitable implements. In an exemplary embodiment, the input device  140  can be a dry erase marker. 
     As the user provides an input or marks in proximity to or upon the display surface  110  using the input device  140 , the first and second optical detection element  130   a  and  130   b  can detect the position of the input device  140  relative to the display surface  110 . The various positions of the input device  140  can be used to determine the input provided by the user. 
     Optical detection element  130   a  can comprise an emitter  131   a  and a receiver  131   b . Similarly, optical detection element  130   b  can comprise an emitter  132   a  and a receiver  132   b . Emitters  131   a  and  132   a  can emit electromagnetic radiation such as an infrared light beam. In an exemplary embodiment, the emitters  131   a  and  132   a  can be an infrared light emitting diode (LED). Correspondingly, receivers  131   b  and  132   b  preferably can detect an infrared light beam. In other embodiments, the emitters  131   a  and  132   a  can be ultrasonic or another suitable form of energy and the receivers  131   b  and  132   b  preferably are capable of detecting said energy. In an exemplary embodiment, the optical receiver elements  131   b  and  132   b  can be coupled charge device (CCD) cameras, or linear CCD camera systems. 
     The optical detection elements  130   a  and  130   b  can be in communication with, disposed on, or coupled to the front or back of the perimeter  120  or the display surface  110 . In other embodiments, the optical detection elements  130   a  and  130   b  can have a mounting assembly enabling attachment to a surface other the display surface  110  or the perimeter  120 , such as a wall. In one embodiment, optical detection elements  130   a  and  130   b  can be coupled or disposed at the upper corners. In other contemplated embodiments, the optical detection elements  130   a  and  130   b  can be coupled to the lower or side corners. 
     The perimeter  120  can extend around edges of the display surface  110 . In addition, the perimeter  120  can extend above the plane of the display surface  110  to define an interior perimeter surface  121  normal to the plane of the display surface  110 . The interior perimeter surface  121  can have retro-reflective characteristics. In one embodiment, the interior perimeter surface  121  can have a retro-reflector along its length. In other embodiments, the retro-reflector need not be disposed along the entire interior perimeter surface  121 . For example, the top side  122  of the interior perimeter surface  121  does not need to be retro-reflective for the system to operate. 
     The interior perimeter surface  121  can reflect an infrared light beam emitted by the emitters  131   a  and  132   b  of optical detection elements  130   a  and  130   b  back along a vector that is parallel to but opposite in direction from the angle of incidence of the beam. Consequently, a beam  131  emitted from first optical detection element  130   a  can be reflected by the interior perimeter surface  121  directly back to the optical detection element  130   a  and detected by a receiver. Retro-reflective materials can be capable of retro-reflecting light beams back within a certain angle of incidence. The portions interior perimeter surface  121  that are at high angle of incidence relative emitters  131   a  and  131   b  of optical detection elements  130   a  and  130   b  can be adapted to facilitate reflection. For example, said portions of the perimeter surface  121  could comprise wide angle retro-reflective material or can be curved, angled, corrugated, or otherwise altered to increase reflection. 
     The optical detection elements  130   a  and  130   b  each can have a field of view that includes a detection area defined by the bottom horizontal portion of the interior perimeter surface  121  and the majority of the vertical portion of the interior perimeter surface  121  opposite said element. In this manner, the field of view of the first optical detection element  130   a  substantially overlaps with the field of view of the second optical detection element  130   b . The detection area is preferably two dimensional, which enables detecting presence of an object in proximity to or in contact with the display surface  110 . This also reduces the flatness requirement of the surface. The pixel dimension of the optical detection elements  130   a  and  130   b  can be selected to achieve the desired field of view. 
     The optical detection elements  130   a  and  130   b  both emit a plurality of infrared beams onto their respective detection areas. The emitted beams are reflected by the interior perimeter surface  121  back to the receivers of the optical detection elements  130   a  and  130   b . The optical detection elements  130   a  and  130   b  can simultaneously emit a plurality of beams onto their entire detection areas. Alternatively, the optical detection elements  130   a  and  130   b  can rapidly scan across their respective detection areas, illuminating a portion of the detection area at one time. 
     The optical detection elements  130   a  and  130   b  can detect the input device  140  in contact with or in proximity to the display surface  140 . The surface of input device  140  is not reflective or substantially less reflective than the interior perimeter surface  121 . Consequently, an input device  140  effectively blocks certain beams emitted from optical detection element  130   a  and  130   b  from being reflected back to the optical detection elements  130   a  and  130   b  by the interior perimeter surface  121 . This absence of reflected beams can be detected by the receivers of the optical detection elements  130   a  and  130   b  as a point of lower intensity in the detection area. For example, in  FIG. 2 , input device  140  blocks beams  132  and  133 . Consequently, these beams will only partially be reflected back to the optical detection elements  130   a  and  130   b  and a reduction in intensity will be detected by the receivers in comparison to the beams reflected by the interior perimeter surface  121 . 
     The electronic whiteboard system  100  can be in communication with a computation device  160  via a communication link  150 . The computation device  160  can be a personal computer (PC), laptop, personal digital assistant, tablet PC, room booking system, Smartphone, or another suitable electronic device capable of executing an operating system. The communication link  150  can be a wireless link such as infrared, radio-frequency, or another suitable wireless communication protocol. Alternatively, the communication link  150  can be a hardwire link such as USB, USB 2.0, firewire, serial cable, coaxial cable, or another suitable electronic communication cable. In further embodiments, the electronic whiteboard system  100  and computation device  160  can be part of a local area network (LAN) or connected through a network, such as a LAN. In alternative embodiments, the computation device  160  can be integrated into the electronic whiteboard system  100 . 
     The computation device  160  can comprise software and data relating to the electronic whiteboard system  100  that enables it to record markings made by a user on the display surface  110 . The computation device  160  can have data relating to a baseline reading of light beams detected by the receivers  131   b  and  132   b  of the optical detection elements  130   a  and  130   a  when an input device  140  is not in contact or proximity to the display surface  110 . The computation device  160  can receive actual light beam detection readings from the electronic whiteboard system  100  and compare these readings to the base line readings. A decrease in the intensity of the light readings can indicate the presence of an object, such an input device or eraser. Comparing the readings from the both the first and second optical detection elements  130   a  and  130   b , the computation device  160  can triangulate the position of the input device  140  relative to the display surface  140 . Comparing multiple successive readings, the computation device  160  can determine a marking, such as a letter or scribble, made upon the display surface. It can also record multiple simultaneous touch points to allow gestural interfaces or allow two people to write on the board simultaneously. 
       FIG. 3  illustrates an embodiment of an electronic whiteboard system  200  for use with a projector  270 . The electronic whiteboard system  200 , computation device  260 , and projector  270  can be in communication with each other via a communication link  250 . The communication link  250  can be substantially similar to the communication link described above. The communication link  250  can be a single link between the system  200 , projector  270  and computation device  260 . In other embodiments, the communication link  250  can be two separate links, a first link between the system  200  and the computation device  260  and a second link between the computation device  260  and the projector  270 . In an exemplary embodiment, the projector  270  can manifest a screen or desktop image, for example, a graphical user interface (GUI), from the computation device  260  onto the display surface  210 . The electronic whiteboard system  200  can be calibrated to determine its position relative to the display surface. Further, the computation device  260  can correlate the position of the projected image relative the display surface  210  with the position of an input device  240 . This can enable a user to interact with the projected image through the electronic whiteboard system  200  in a variety of ways. For example, a user can manipulate an image of a projected desktop using an input device  240  that functions as a mouse cursor. The user can open and close programs by pointing and “clicking” on the display surface using the input device  240  as if seated at the computation device  260 . 
       FIGS. 4A-4B  illustrate an eraser device  300  useful with an electronic whiteboard system  200 . The eraser device  300  comprises an orientation identification system  310  that reduces or eliminates eraser ghosting that arises with use of conventional rectangular erasers with camera-based systems. 
     An eraser will block the retro-reflectors of the whiteboard system in the same way that a pen will, in that for a simple rectangular eraser, the system gets a start and end angle for each camera. It would be preferred that there would only be one location and angle of the eraser that could produce these angles, but this is not the case with a conventional rectangular eraser. 
     In many areas of the board, and at many angles, there are two angles of the erasers that will produce the same view as seen from the cameras. This makes it hard for the system to choose between the two possible states of the eraser (duplicative states), for the system to identify which is the “real” location/orientation of the eraser, and which is a “ghost”. Thus, with a conventional eraser, there are times when a camera-based system can identify the location of the eraser within which the eraser can occupy one of two orientations. For example, as shown in  FIG. 5 , this particular arrangement of cameras and eraser, two possible orientations for the captured eraser exist, and thus the system cannot accurately determine the indicia to be erased. 
     As the user moves the eraser about the board, there are indeed clues as to which is the real eraser and which is the ghost, which upon a state of a future event of moving the eraser, the system could conceivably move back in time and accurately identify the previously correct state (orientation) of the eraser when it was in its previous duplicative state, but such a solution is mainly software driven, whereas providing an eraser device with a orientation identification system  310  is not as processor intensive. 
     It also is possible to limit the ghosting problem not just with a software solution, but by, for example, changing the aspect ratio of the eraser, to a long thin eraser, which will have much fewer cases of eraser ghosting than a short fat eraser, but even with a long thin eraser, ghosting is not eliminated. By adding an orientation identification system  310  to the eraser, the ghosting problem is effectively eliminated. 
     An exemplary embodiment of an orientation identification system  310  is a system provided to an eraser that provides eraser position/orientation data to the whiteboard system that eliminates eraser ghosting, such that when an eraser is used upon the surface, at all times the eraser with an orientation identification system  310  informs the system of its location and orientation. 
     An exemplary embodiment of an orientation identification system  310  is the provision of retro-reflectors on the eraser  300 , which provide the camera-based system with data sufficient to eliminate areas on the whiteboard where the eraser can be in a one of two orientations. In this embodiment, the orientation identification system  310  provides the system with reflection (light areas) useful in cooperation of the typically dark areas of the remainder of the non-reflective portions of the eraser. The location of the eraser  300  thus can be triangulated by the location of the dark areas in the view of each camera. The orientation of the eraser can be determined by the pattern received from each camera. 
     The retro-reflectors should be in a length(s) and location(s) in order to overcome the loss of retro-reflective properties at certain angles of incidence. That is, eraser ghosting will not be eliminated if an eraser  300  is provided with retro-reflective materials, but in a way that there remain certain orientations of the eraser that effectively eliminate the usefulness of the retro-reflectors used, because they are not capable of reflecting the light beams back outside the cone of accurate retro-reflection. 
       FIG. 13  illustrates a cone of accurate reflection  350  of a retro-reflector  390 , in accordance with an exemplary embodiment the present invention. As shown in  FIG. 13 , a light beam originating from a point  360  within a cone of accurate retro-reflection  350  of the retro-reflector  390  can be reflected back to that point by the retro-reflector  390 . A light beam originating from a point  370  outside the cone of accurate reflection  350  of the retro-reflector  390  will not be reflected back to that point. 
     Referring back to  FIGS. 4A-4B , an exemplary embodiment of an orientation identification system  310  is the provision of one or more windows  320  in the eraser  300 , each window formed of one or more angled surfaces  330 , at least a portion of which are retro-reflecting. Each window is shown located in proximity to the short end of the eraser, but the spacing is variable. In this embodiment, the issues of loss of retro-reflection properties are effectively negated, as there is always presented a surface  330  that remains retro-reflective. As shown in  FIG. 4C , In another embodiment, the orientation identification system  310  can include an outwardly extending member  315 , which incorporates the retro-reflector. 
       FIGS. 14A-B  illustrate cones of accurate reflection  350  for various configurations of retro-reflective portions  390  of windows  320  of an eraser  300 , in accordance with exemplary embodiments the present invention. As shown in  FIG. 14B , an angled surface  330  of a window  320  with a retro-reflective portion  390  can partially occlude  395  a cone of accurate reflection  350  of the retro-reflective portion  390 . 
     As shown in example form in  FIGS. 6A-6B , the pattern of the light tells the system that it sees an eraser, as well as the location of the reflectors in the eraser windows. The size of the image of the reflectors in the eraser window tells the system which of the two possible orientations the eraser is in. In particular, the charts of  FIG. 6B  illustrate the amount of light detected by the optical detection elements, which for simplicity are labeled as CAMERA  1  (in the lower left hand corner of the whiteboard) and CAMERA  2  (in the lower right hand corner of the whiteboard). 
     Referring to the chart identifying the light detected by CAMERA  1 , starting from the left side of the perimeter of the whiteboard, CAMERA  1  views the light emitted by the emitter and reflected back to the receiver. As the CAMERA  1  view spans to the right, it ultimately reaches point A, which as depicted in  FIG. 6A  is a corner of the eraser. From point A to point B, CAMERA  1  sees an absence of light, as a portion of the eraser blocks the light emitted by the emitter, and hence little to no light is reflected back to the receiver. Continuing along CAMERA  1 &#39;s view, from point B to point C light emitted by the emitter is reflected back to the receiver by the eraser&#39;s reflector, and hence in the chart of CAMERA  1  in  FIG. 6B , the light received by the receiver is illustrated with the spike. From point C to point D, there is again an absence of light being reflected back to the receiver, which in  FIG. 6B  is shown by the dip in the chart. After point D and through the remaining 90 degrees of viewing area of CAMERA  1 , the most, if not all, the light emitted by the emitter is reflected back to the receiver. 
     As for CAMERA  2  of  FIGS. 6A-6B , starting from the bottom side of the perimeter of the whiteboard, CAMERA  2  views the light emitted by the emitter and reflected back to the receiver. As the CAMERA  2  view spans to the right, it ultimately reaches point E, which as depicted in  FIG. 6A  is a corner of the eraser. From point E to point F, CAMERA  2  sees an absence of light, as a portion of the eraser blocks the light emitted by the emitter, and hence little to no light is reflected back to the receiver. Continuing along CAMERA  2 &#39;s view, from point F to point G light emitted by the emitter is reflected back to the receiver by the eraser&#39;s reflector, and hence in the chart of CAMERA  2  in  FIG. 6B , the light received by the receiver is illustrated with the spike. From point G to point H, there is again an absence of light being reflected back to the receiver, which in  FIG. 6B  is shown by the dip in the chart. After point H, which is another corner of the eraser, and through the remaining 90 degrees of viewing area of CAMERA  2 , most, if not all, the light emitted by the emitter is reflected back to the receiver. 
       FIGS. 7A-12  illustrate various exemplary embodiments of the present eraser. 
     An exemplary embodiment of an orientation identification system  310  is the provision of four windows  320  in the eraser  300 , two located on each long side of the eraser, each window formed of two, 90° angled surfaces  330 , at least a portion of which are retro-reflecting. 
     The result of the windows  320  is that each camera used in the system will only see one window, and by where the cameras see the reflectors, the system can tell with precision which is the real eraser and which is the ghost. 
     An exemplary embodiment of the eraser  300  comprises an eraser pad  302  and a mounting block  304 , optionally with a separate handle  306  for holding. The mounting block  304  incorporates the orientation identification system  310 , being four faceted inside windows  320 . Each inside window  320  contains a reflector  330 , such that at any point in time, one of the at least two cameras can see at least one reflector  330 . 
     Other arrangements of the windows  320  can be provided. These windows  320  can also be located behind an infrared transmissive and visible light-blocking cover  308  when infrared light is used for the coordinate detection. 
     It has been found that in an exemplary four window  320  embodiment, an optimum placement of each of the four windows (two on each side) about the eraser is between 17-21% of the length of the eraser  300  from each end. As shown in  FIG. 11  to scale, in an exemplary embodiment, the windows  320  are centered about a line approximately 18% of the length of the eraser  300  from each end. As shown in  FIG. 12  to scale, in an exemplary embodiment, the windows  320  are centered about a line approximately 20% of the length of the eraser  300  from each end. 
     The size and number of windows can vary. There could also be different colors for the reflectors in the windows, and a means to detect the color. The windows could be covered with a cover that only transmits light at the frequency of the illumination source (e.g. infrared). The windows also could be made thinner (closer to the board surface). The windows could also be “holes” through which the reflector on the perimeter whiteboard is viewed. The windows could also comprise mirrors that reflected the light from a different part of the board. 
     While the various embodiments of this invention have been described in detail with particular reference to exemplary embodiments, those skilled in the art will understand that variations and modifications can be effected within the scope of the invention as defined in the appended claims. Accordingly, the scope of the various embodiments of the present invention should not be limited to the above discussed embodiments, and should only be defined by the following claims and all applicable equivalents.