Patent Application
20120274765
The present invention relates to an apparatus for determining the location of a pointer within a region of interest.
Interactive input systems are well known in the art and typically comprise an input or touch surface on which contacts are made using a pointer in order to generate user input. Pointer contacts with the touch surface are detected and are used to generate corresponding output depending on areas of the touch surface where the pointer contacts are made. There are basically two general types of interactive input systems available and they can be broadly classified as “active” and “passive” interactive input systems.
Active interactive input systems allow a user to generate user input by contacting the touch surface with a special pointer that usually requires some form of on-board power source, typically batteries. The special pointer emits signals such as infrared light, visible light, ultrasonic frequencies, electromagnetic frequencies, etc. that activate the touch surface.
Passive interactive input systems allow a user to generate user input by contacting the touch surface with a passive pointer and do not require the use of a special pointer in order to activate the touch surface. A passive pointer can be a finger, a cylinder of some material, or any suitable object that can be used to contact some predetermined area of interest on the touch surface.
Passive interactive input systems provide advantages over active interactive input systems in that any suitable pointing device, including a user's finger, can be used as a pointer to contact the touch surface. As a result, user input can easily be generated. Also, since special active pointers are not necessary in passive interactive input systems, battery power levels and/or pointer damage, theft, or misplacement are of little concern to users.
International PCT Application No. PCT/CA01/00980 filed on Jul. 5, 2001 and published under No. WO 02/03316 on Jan. 10, 2002, assigned to SMART Technologies ULC of Calgary, Alberta, Canada, assignee of the subject application, discloses a camera-based interactive input system comprising a touch screen that includes 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 relative to the touch surface using triangulation. The pointer location data is conveyed to a computer executing one or more application programs. The computer uses the pointer location data 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.
Although the above interactive input system works extremely well, the use of four digital cameras and associated digital signal processors to process image data captured by the digital cameras makes the touch system hardware intensive and therefore, increases the costs of manufacture. This of course translates into higher costs to consumers. In some environments where expense is of a primary concern, less expensive interactive input systems are desired.
A camera-based interactive input system having reduced hardware has been considered. For example, U.S. Pat. No. 5,484,966 to Segen discloses an apparatus for determining the location of an object within a generally rectangular active area. The apparatus includes a pair of mirrors extending along different sides of the active area and oriented so that the planes of the mirrors are substantially perpendicular to the plane of the active area. The mirrors are arranged at a 90 degree angle with respect to one another and intersect at a corner of the active area that is diagonally opposite a detecting device. The detecting device includes a mirror and a charge coupled device (CCD) sensor and looks along the plane of the active area. A processor communicates with the detecting device and receives image data from the CCD sensor.
When a stylus is placed in the active area, the detecting device sees the stylus directly as well as images of the stylus reflected by the mirrors. Images including the stylus and stylus reflections are captured by the detecting device and the captured images are processed by the processor to detect the stylus and stylus reflections in the captured images. With the stylus and stylus reflections determined, the location of the stylus within the active area is calculated using triangulation.
Although this apparatus reduces hardware requirements since only one optical sensing device and processor are used, problems exist in that at certain locations within the active area, namely along the side edges and adjacent the corner diagonally opposite the detecting device, resolution is reduced. As will be appreciated, an interactive input system that takes advantage of reduced hardware requirements yet maintains high resolution is desired.
It is therefore an object to provide a novel apparatus for determining the location of a pointer within a region of interest.
Accordingly, in one aspect there is provided an apparatus for detecting a pointer within a region of interest comprising a first reflective element extending along a first side of said region of interest and reflecting light towards said region of interest, said first reflective element comprising at least two generally parallel bands thereon, said bands at least comprising a retro-reflective band and a reflective band, a second reflective element extending along a second side of said region of interest and reflecting light towards said region of interest, said second side being joined to said first side to define a first corner, said second reflecting element comprising at least two generally parallel bands thereon, said bands at least comprising a retro-reflective band and a reflective band, at least one imaging device capturing images of said region of interest including reflections from the reflective and retro-reflective bands of said first and second reflective elements, and at least one illumination source positioned adjacent to said at least one imaging device, said at least one illumination source directing light across said region of interest towards said first and second reflective elements.
According to another aspect there is provided an apparatus for detecting a pointer within a region of interest comprising a first reflective element extending along a first side of said region of interest and reflecting light towards said region of interest, said first reflective element comprising at least two generally parallel bands thereon, said bands at least comprising a retro-reflective band and a reflective band, a second reflective element extending along a second side of said region of interest and reflecting light towards said region of interest, said second side being joined to said first side to define a first corner, said second reflecting element comprising at least two generally parallel bands thereon, said bands at least comprising a retro-reflective band and a reflective band, at least one imaging device capturing images of said region of interest and reflections from said first and second reflective elements, said at least one imaging device having an active pixel sub-array and said first and second reflective elements being configured to aim reflected light towards said active pixel sub-array, and at least one illumination source positioned adjacent to said at least one imaging device, said at least one illumination source directing light across said region of interest and towards said first and second reflective elements.
According to yet another aspect there is provided an apparatus for detecting a pointer within a region of interest comprising a generally rectangular touch surface defining said region of interest, a first reflective element extending along a first side of said region of interest and reflecting light towards said region of interest, said first reflective element comprising at least two generally parallel bands thereon, said bands at least comprising a retro-reflective band and a reflective band, a second reflective element extending along a second side of said region of interest and reflecting light towards said region of interest, said second side being joined to said first side to define a first corner, said second reflecting element comprising at least two generally parallel bands thereon, said bands at least comprising a retro-reflective band and a reflective band, a detecting device detecting said pointer within said region of interest contrasting with a background provided by the retro-reflective bands of said first and second reflective elements, the detecting device also detecting said pointer and reflections of said pointer contrasting with a background provided by the reflective bands of said first and second reflective elements, and determining the location of said pointer within said region of interest, and at least one illumination source positioned adjacent said to said detecting device, said at least one illumination source directing light across said region of interest and towards said first and second reflective elements.
According to still yet another aspect there is provided an apparatus for detecting a pointer within a region of interest comprising a first reflective element extending along a first side of said region of interest and reflecting light towards said region of interest, said first reflective element comprising at least two generally parallel bands thereon, said bands at least comprising a retro-reflective band and a reflective band, at least two imaging devices positioned adjacent to opposing corners of a second side of said region of interest, said second side opposite said first side, said at least two imaging devices capturing images of said region of interest including reflections from the reflective and retro-reflective bands of said first reflective element, and at least two illumination sources directing light across said region of interest towards said first reflective element.
Embodiments will now be described more fully with reference to the accompanying drawings in which:
a to 8d are plan views showing a pointer within the region of interest at locations resulting in pointer image merging.
a to 9d are illustrations showing determination of the margins within the region of interest.
a is a side view of an alternative embodiment of an illuminated bezel.
b is a top plan view of the illuminated bezel of
Turning now to
Assembly 12 comprises a frame 20 supporting an imaging device 22 adjacent one corner of the touch surface 14. The imaging device 22 has a field of view that looks generally across the plane of the touch surface 14 and is oriented so that its optical axis generally forms a 45 degree angle with adjacent sides of the touch surface 14. A pair of mirrors 24 and 26 is also supported by the frame 20. Each mirror 24, 26 extends along a different side of the touch surface 14 and is oriented so that the plane of its reflecting surface 28, 30 is generally perpendicular to the plane of the touch surface 14. The mirrors 24 and 26 are thus arranged at generally a 90 degree angle with respect to one another and intersect at a corner 32 of the touch surface 14 that is diagonally opposite the imaging device 22. A gap 40 is provided between the two mirrors 24 and 26 at the corner 32 to define a non-reflecting area or region.
The frame 20 also supports illuminated bezels 42 that extend along the remaining two sides of the touch surface 14. The illuminated bezels 42 direct light such as for example infrared light towards the reflecting surfaces of the mirrors 24 and 26. The light is in turn reflected back towards the imaging device 22 so that the imaging device 22 effectively sees bright bands of infrared backlighting. A band of infrared illumination is also directed towards the imaging device 22 by an illuminated bezel 42 disposed within the gap 40. The imaging device 22 therefore observes a generally continuous bright band of infrared illumination when no pointer is located within the region of interest ROI. However, when the imaging device 22 acquires an image and a pointer P is located within the region of interest ROI, the pointer P occludes reflected illumination and appears to the imaging device 22 as a black or dark object against a white or bright background. The infrared illuminated bezels 42 are similar to those described in U.S. Pat. No. 6,792,401 entitled “Illuminated Bezel And Touch System Incorporating the Same” to Akitt, et al., issued on Dec. 6, 2005 and assigned to SMART Technologies ULC, the content of which is incorporated herein by reference in its entirety. Accordingly, specifics of the illuminated bezels 42 will not be described further herein.
As best shown in
Each mirror 24, 26 is supported on the frame 20 by a right angle extruded bracket 50 as shown in
The reflective surfaces 28 and 30 of the mirrors 24 and 26 are generally planar and are oriented so that the bands of backlight illumination provided by the illuminated bezels 42, when reflected by the mirrors, are directed towards an active pixel sub-array of the imaging device 22. Orienting the mirrors 24 and 26 so that the reflective surfaces achieve this desired function maintains the resolution of the apparatus 10 allowing pointer hover above and pointer contact with the touch surface 14 to be accurately determined. To align the mirrors, during assembly, adhesive 56 is placed along the leg 50b of each bracket 50 and the mirrors are set in place. While the adhesive 56 is setting, the tilt of each mirror is adjusted until the backlighting reflected by the reflective surface is directed toward the active pixel sub-array of the imaging device 22. Once the adhesive 56 sets, the mirrors 24 and 26 are securely held by the adhesive 56 thereby to maintain their orientation.
The imaging device 22 is best seen in
During use, when a pointer P is brought into the active area 34 of the region of interest ROI and therefore, into the field of view of the digital camera 60, the pointer P occludes the backlight illumination emitted by the illuminated bezel 42 in the gap 40 and the backlight illumination reflected by the mirrors 24 and 26. When the digital camera 60 captures an image and a pointer P is in the image, depending on the position of the pointer P, the captured image includes dark areas representing the pointer P and images or reflections of the pointer. Depending on the location of the pointer relative to the active area 34 different scenarios may occur. For example, the captured image may include dark areas representing the true pointer PT, and three images of the pointer resulting from right, left and double pointer reflections PR, PL, PD respectively or may include dark areas representing the true pointer PT, and two pointer images.
Although the interactive input system 10 includes only a single digital camera 60, the use of the mirrors 24 and 26 to reflect images of the pointer P towards the digital camera 60 effectively creates an interactive input system that is four (4) times as large with virtual cameras at each of its corners as shown in
In order to determine the position of the pointer P relative to the touch surface 14, it is necessary to distinguish between the true pointer and the various pointer reflections in the captured image. Relying on the geometry of the interactive input system 10, the following relationships between the angles Ø1 to Ø3 hold true. Ø2 is less than or equal to Ø1, which is less than or equal to Ø0. Ø2 is less than or equal to Ø3, which is less than or equal to Ø0. As a result, the outer two pointers in the captured image always correspond to angles Ø2 and Ø0 and the two inner pointers in the captured image always correspond to angles Ø1 and Ø3.
When the captured image includes four dark areas representing the true pointer PT, the right pointer reflection PR, the left pointer reflection PL and the double pointer reflection PD, distinguishing between the true pointer and the pointer reflections is a straightforward process. The dark area to the extreme left is the left pointer reflection PL and the dark area to the extreme right is the right pointer reflection PR. To distinguish between the true pointer PT and the double pointer reflection PD, i.e., the two intermediate dark areas, the column of the active pixel sub-array that contains the diagonal vertex, i.e., the midpoint of the illuminated bezel 42 within the gap 40, is determined. Once the column location of the diagonal vertex is determined, the columns of the active pixel sub-array that contain the two intermediate dark areas are determined. The distances between the columns that contain the two intermediate dark areas and the column containing the diagonal vertex are compared. Since the double pointer reflection PD is always further away from the imaging device 22, the column separation between the double pointer reflection PD and the diagonal vertex is always smaller than the column separation between the true pointer PT and the diagonal vertex. As a result by comparing the column separation between the intermediate dark areas and the diagonal vertex, the true pointer PT can be easily distinguished from the double pointer reflection PD.
When the captured image includes three dark areas, the column location of the diagonal vertex is again determined and the number of dark areas on each side of the diagonal vertex area are determined. If two dark areas are to the left of the diagonal vertex and one dark area is to the right of the diagonal vertex, two scenarios are possible. In one scenario, the true pointer PT is merging with the right pointer reflection PR. In this case, the left dark area is the left pointer reflection PL and the middle dark area is the double pointer reflection PD. The right dark area includes both the true pointer PT and the right pointer reflection PR. The other scenario is that the double pointer reflection PD is missing as a result of the non-reflective region associated with the gap 40. To determine which scenario exists, again the pointer data is processed for both scenarios and the scenario that yields a correctly triangulated location is determined to be correct. If both scenarios yield a correctly triangulated location, the position of the middle dark area relative to the diagonal vertex is determined. If the double pointer reflection Pp is missing, the true pointer PT will be very close to the diagonal vertex.
Similarly if two dark areas are to the right of the diagonal vertex and one dark area is to the left of the diagonal vertex, two scenarios are possible. In one scenario, the true pointer PT is merging with the left pointer reflection PL. In this case, the right dark area is the right pointer reflection PR and the middle dark area is the double pointer reflection PD. The left dark area includes both the true pointer PT and the left pointer reflection PL. The other scenario is that the double pointer reflection PD is missing as a result of the non-reflective region associated with the gap 40. To determine which scenario exists, again the pointer data is processed for both scenarios and the scenario that yields a correctly triangulated location is determined to be correct. If both scenarios yield a correctly triangulated location, the position of the middle dark area relative to the diagonal vertex is determined. If the double pointer reflection Pp is missing, the true pointer PT will be very close to the diagonal vertex.
Knowing the true pointer PT and two or more of the pointer reflections PR, PL and Pp as well as the angles Ø0 to Ø3, the pointer position relative to the touch surface is calculated using well known triangulation such as described in U.S. Pat. No. 6,954,197 issued on Oct. 11, 2005 for an invention entitled “Size/Scale And Orientation Determination Of A Pointer In A Camera-Based Touch System” to Morrison, et al., assigned to SMART Technologies ULC, the content of which is incorporated herein by reference in its entirety. In this example, a bounding area representing the pointer location relative to the touch surface 14 is determined and conveyed to the general purpose computing device 16.
The margins are provided about the periphery of the active area 34 to avoid pointer identification ambiguity that may occur if the pointer P gets too close to the mirrors 24 and 26, too close to the imaging device 22 or too close to the diagonal vertex, i.e., corner 32. When the pointer P gets too close to the mirror 24 adjacent the illuminated bezel 42, the true pointer PT and left pointer reflection PL will merge and the right pointer reflection PR and double pointer reflection PD will merge as shown in
The widths of the margins Mbot and Mright are determined based on the situation where the pointer P gets too close to the imaging device 22 and are calculated as follows with reference to
When θ2 is less than θ1, the true pointer PT and the left pointer reflection PL will merge. Thus, in order to prevent merging, θ2 must be larger than θ1. To calculate margin Mbot, the smallest Mbot is desired while ensuring θ2 is bigger than θ1.
The calculation of margin Mbot depends on the values chosen for margins Mleft and Mright. In order to simplify the calculations, assume margins Mleft and Mright both have widths equal to one inch. Using standard trigonometry, it can be deduced that:
tan(θ1)≅(Mbot+(pointer diameter/2))/(2×4×72/5+Mright+2×Mleft)
θ1≅arctan((Mbot+0.375)/118.2)<1°.
Substituting the measurements given above for the apparatus 10, it can be seen that θ1<1°. Similarly, it can be shown that:
θ2≅90°−arctan(Mright/Mbot)−arcsin((pointer diameter/2)/sqrt((Mright)2+(Mbot)2)).
While it is possible to solve for margin Mbot using analytic techniques, it is also possible to use a trial and error technique. The trial and error technique involves selecting a potential value for margin Mbot and computing θ2 using the above equation. If θ2 is larger than θ1, then the selected margin Mbot is acceptable and will inhibit pointer merging. By way of example, if margin Mbot has a width equal to ½ inch and margin Mright has a width equal to 1 inch, θ2 is 7°, which is larger than θ1.
A similar technique can be applied to margin Mright and a value can be computed for a given margin Mbot. Consider the example shown in
In order to inhibit pointer merging when the pointer P is too close to the mirrors 24 and 26 near the illuminated bezels or too close to the diagonal vertex, a margin is introduced along the left and top sides of the active area 34. The worst case generally happens at the corner 32 diagonally opposite the imaging device 22 if the mirrors intersect at that corner. As will be appreciated, if the mirrors 24 and 26 extended along the entire lengths of the touch surface sides and intersected at the corner 32, when a pointer P is positioned near the corner 32, in a captured image the true pointer PT and the double pointer reflection PD will merge as shown in
Using the same dimensions as above, the angles that bound the true pointer PT are 36.65° and 37.25° as shown in
M
left≧pointer radius/sin(36.65°)≧0.63″
M
top≧pointer radius/cos(37.25°)≧0.47″.
In practice, the separation between the true pointer and a pointer reflection should be large enough such that the imaging device 22 can resolve the difference between the true pointer and the pointer reflection. Generally, the widths of the margins are selected to be greater than the minimum widths to take into account limitations in the resolving power of the imaging device 22 as well as the fact that the pointer P may be held at an angle relative to the touch surface.
When a pointer is positioned adjacent a corner of the touch surface 14 where one of the illuminated bezels 42 and mirrors 24 and 26 meet, the true pointer and the pointer reflection from the nearest mirror merge. In this case, whenever a pointer image includes two pointer tips, the actual locations of the true pointer PT and the pointer reflection are ascertained using the shape of the bounding box surrounding the merged images.
The optical axis of the digital camera 60 is also at an oblique angle with respect to the plane of the touch surface 14 so that when a pointer P is in the active area 34 of the region of interest ROI, the digital camera 60 sees the true pointer and the pointer reflections as well as reflections of the true pointer and the pointer reflections off of the touch surface 14. Pointer contacts with the touch surface 14 are determined when the true pointer and pointer reflections and their reflections off of the touch surface 14 are in contact. Pointer hover is determined when the true pointer and pointer reflections and their reflections off of the touch surface 14 are spaced apart. Further specifics of this contact detect determination are described in U.S. Pat. No. 6,947,032 to Morrison, et al., issued on Sep. 20, 2005 for an invention entitled “Touch System And Method For Determining Pointer Contacts On A Touch Surface”, assigned to SMART Technologies ULC, the content of which is incorporated herein by reference in its entirety.
Due to optical and mechanical limitations, in some instances even when a pointer is hovering over the touch surface 14, one or more of the true pointer and pointer reflections may appear to be in contact with their reflections off of the touch surface 14. To enhance contact detect, difference images are generated by subtracting current images of the true pointer and pointer reflections from the corresponding locations in a background image captured upon initialization of the apparatus 10. Then, horizontal intensity profiles (HIPs) of the difference images are combined with the captured images.
In some instances, an HIP and associated binary image may be inconsistent. For example, in
for at least two pointers, there is a gap of the pointer in the binary image; or
for at least one pointer, the associated HIP extends below its threshold line and there is a gap of the pointer in the binary image and for at least two pointers their associated HIPs extend below their threshold lines.
It is possible that pointers may satisfy both conditions as illustrated in
Turning now to
When the pointer P′ is in contact with the touch surface 214 and the pointer emits infrared light, light rays are emitted by the IR LED as shown in
Turning now to
Although the apparatuses have been described as including generally planar mirrors that are affixed to brackets by adhesive to maintain their desired orientations, other designs to reflect backlight illumination towards the active pixel sub-array of the imaging device are of course possible. For example, if desired, each mirror 401 may be connected to one side of the frame 402 via a pair of piano-type hinges 400 as shown in
In a further embodiment, rather than using planar mirrors, curved mirrors can be used. In this case, the reflective surfaces of the mirrors are generally convex so that the bands of backlight illumination provided by the illuminated bezels when reflected by the mirrors are directed towards the active pixel sub-array of the imaging device. Curving the mirrors increases the fields of view of the mirrors and hence, reduces mounting tolerances. In this embodiment, the mirrors have a radius of curvature equal to approximately 100 inches. The radius of curvature of the mirrors and the height of the infrared illuminated bezels are selected so that at least ½ inch of the pointer tip is illuminated by reflected infrared backlighting when the pointer is in the region of interest and is in contact with the touch surface.
In yet another embodiment, the mirrors may include a pair of reflective surfaces 502 and 504 arranged 90 degrees with respect to one another to form a V-configuration as shown in
In still yet another embodiment, the mirrors may include corrugated reflective surfaces 602 defined by stacked pairs of reflective surfaces arranged 90 degrees with respect to one another as shown schematically in
Although the gap has been shown and described as extending along two sides of the region of interest, those of skill in the art will appreciate that the non-reflective region associated with the gap need only extend along one side of the region of interest to inhibit the double pointer reflection from occurring when the pointer is adjacent the corner 32. Also, although the non-reflective region is shown as a gap between the mirrors 24 and 26, if the mirrors join at the corner 32, the mirrors can be rendered non-reflective at the corner 32 using a suitable coating or covering to define the non-reflective region.
Turning now to
a and 22b show an alternative illuminated bezel generally identified by reference numeral 800. As can be seen, in this embodiment the illuminated bezel 800 comprises a parabolic collimator 804 formed on an internal bezel surface that reflects light from an LED 808 back across the touch surface 814 on paths generally parallel to the touch surface 814. A lenticular array 820 positioned between the touch surface 814 and the collimator 804 disperses the light reflected by the collimator 804 across the touch surface 814. The lenticular array 820 can, for example, have a number of facets that redirect light within a horizontal plane above the touch surface 814, while preserving its vertical component to ensure that the light travels generally across the touch surface 814 and not away from or towards it. By redirecting a significant portion of the light from the LED 808 across the touch surface 814, a greater intensity of light is viewed by the imaging device, thus providing better resolution in the images captured. As seen in
Turning now to
Assembly 912 comprises a frame 920 supporting an imaging device 922 adjacent one corner of the touch surface 914. The imaging device 922 has a field of view that looks generally across the plane of the touch surface 914 and is oriented so that its optical axis generally forms a 45 degree angle with adjacent sides of the touch surface 914.
A pair of reflective elements 924 and 926 is also supported by the frame 920. Each reflective element 924 and 926 extends along a different side of the touch surface 914 and is oriented such that the plane of its reflecting surface is generally perpendicular to the plane of the touch surface 914. The reflective elements 924 and 926 are thus arranged at generally a 90 degree angle with respect to one another and intersect at a corner 936 of the touch surface 914 diagonally opposite from imaging device 922.
In this embodiment, the reflecting surface of reflective element 924 comprises a pair of generally parallel bands or strips that extend the length of the reflective element 924. In particular, the reflective surface of reflective element 924 comprises a retro-reflective band 928 that is positioned furthest from the touch surface 914 and a reflective band 930 below the retro-reflective band 928 nearest the touch surface. Similarly, the reflecting surface of reflective element 926 comprises a pair of generally parallel bands or strips that extend the length of the reflective element. In particular, the reflective surface of reflective element 926 comprises a retro-reflective band 932 that is positioned furthest from the touch surface 914 and a reflective band 934 below the retro-reflective band 932 nearest the touch surface.
The frame 920 also supports retro-reflective bezels 942 extending along the remaining two sides of the touch surface 914, one on either side of the imaging device 922. The retro-reflective bezels 942 reflect incident light back substantially in the impingent direction and thus, effectively act as illuminated bezels similar to those shown in
Positioned adjacent to the imaging device 922 is an infrared illumination source 923 such as, for example, one or more infrared LEDs, that direct infrared (IR) light towards the reflective elements 924 and 926. The retro-reflective bands 928 and 932 of the reflective elements 924 and 926 re-direct the IR light back towards the imaging device 922 while the reflective bands 930 and 934 of the reflective elements 924 and 926 scatter the IR light. Some of the scattered IR light impinges on the retro-reflective bezels 942 where it is returned to the reflective bands 930 and 934 and reflected back towards the imaging device 922.
Each reflective element 924, 926 is supported on the frame 920 by a right angle extruded bracket, similar to that described above with reference to
The imaging device 922 is similar to imaging device 22 described above. Accordingly, specifics will not be described further.
During use, infrared light emitted by the illumination source 923 is redirected by the retro-reflective bands 928 and 932 of the reflective elements 924 and 926, back towards the imaging device 922. Infrared light emitted by the illumination source 923 is also scattered by the reflective bands 930 and 934 of the reflective elements 924 and 926. As mentioned above, some of the scattered infrared light is returned to the imaging device while some of the scattered infrared light impinges on the retro-reflective bezels 942. The scattered infrared light that impinges on the retro-reflective bezels 942 is returned to the reflective bands 930 and 934 where it is reflected back towards the imaging device 922. Thus, in the event no pointer P is positioned within the region of interest ROI, the imaging device 922 observes a generally continuous white or bright band of infrared illumination. The white or bright band is comprised of two components, one component representing infrared light re-directed by the retro-reflective bands 928 and 932 directly back to the imaging device 922 and one component representing infrared light scattered by the reflective bands 930 and 934, whether directly impinging thereon or returning from the retro-reflective bezels 942.
When a pointer P is brought into the region of interest ROI and therefore, into the field of view of the imaging device 922, the pointer P occludes infrared illumination. Thus, when the imaging device captures an image, the pointer P appears as a dark spot against a white background representing the true pointer in the component representing infrared light re-directed by the retro-reflective bands 928 and 932. The pointer P also appears as multiple dark spots representing the true pointer location and the pointer reflections in the component representing infrared light scattered by the reflective bands 930 and 934, whether directly impinging thereon or returning from the retro-reflective bezels 942. The true pointer location can be distinguished from the pointer reflections since only the true pointer location is captured against the retro-reflective bands 928 and 932. The pointer location can then be calculated using triangulation as described above.
Because the true pointer location can always be distinguished from the image of the pointer on the retro-reflective bands 928 and 932, there is no requirement for a gap between the reflective elements 924 and 926 in order to resolve the double pointer reflection PD when the pointer P is near the corner 936. Further, there is no requirement for a margin surrounding the touch surface 914 in order to resolve merged pointers if the pointer gets too close to the reflective bands 930 and 934, imaging device 922 or diagonal vertex. As will be appreciated, this simplifies the calculation to determine the location of the pointer P relative to the touch surface 914.
As will be appreciated, the bands of the reflective elements 924 and 926 could be arranged such that the reflective bands 930 and 934 are positioned farthest from the touch surface 914, and the retro-reflective bands 928 and 932 are positioned closest to the touch surface 914.
Although the reflective elements 924 and 926 are described as having two separate reflective and retro-reflective bands separately adhered to a bracket, those skilled in the art will appreciate that the reflective elements may be made of a single reflective band. In this embodiment, the single reflective band may be a mirror and the mirror could be partially coated by a retro-reflective covering thus defining a retro-reflective band on part of the reflective band.
In another embodiment, the reflective bands 924 and 926 may be covered with polarizers and the infrared illuminated bezels may be polarized such that double pointer reflections could be attenuated allowing image processing to be further simplified.
In another embodiment the retro-reflective bezels 942 may be infrared illuminated bezels, thereby eliminating the need for an illumination source positioned adjacent to the imaging device. Further, the illuminated bezels could be modulated differently from one another such that the direct reflections could be separated from the double reflections.
In yet another embodiment, two imaging devices may be used and mounted on adjacent corners of a first side of the frame. In this embodiment, a first reflective element, similar to reflective element 924 described above, extends along a second side of the frame opposite the two imaging devices. Retro-reflective bezels, similar to retro-reflective bezels 942 described above, extend along the first side, a third side, and a fourth side of the frame. An infrared light source is positioned adjacent to each one of the imaging devices, providing infrared illumination to the region of interest. This creates an interactive input system that is two (2) times as large with virtual cameras at each of its corners. The combination of retro-reflective bezels with the reflective element reflecting the illumination emitted by each light source provides a generally continuous bright band of infrared illumination observed by the imaging devices when no pointer is within the field of view of the imaging devices. When a pointer is brought into the region of interest, and therefore, into the field of view of each of the imaging devices, the pointer occludes the continuous bright band of light observed by each imaging device. As such, the pointer appears as a dark spot against a white background representing the true pointer location. Since two imaging devices are used, the location of the pointer can be calculated using triangulation. In another embodiment, rather than emitting infrared illumination, it will be appreciated that the light sources may emit any spectrum of light such as for example visible light. In yet another embodiment, the retro-reflective bezels may be replaced by illuminated bezels, thereby eliminating the need for a light source positioned adjacent each imaging device.
The digital camera is described as being mounted on a circuit board and positioned so that its field of view looks generally across the plane of the touch surface. As will be appreciated, the circuit board can of course be located at different locations. In this case, folding optics are used to aim the field of view of the digital camera across the plane of the touch surface. As will also be appreciated a variety of different types of imaging devices can be used to capture images such as for example CCD sensors and line arrays. If desired, the surface of the display unit may be used as the touch surface.
Although embodiments have been described with particular reference to the figures, those of skill in the art will appreciate that variations and modifications may be made without departing from the scope thereof as defined by the appended claims.
This application is a continuation-in-part of U.S. patent application Ser. No. 11/762,198 filed on Jun. 13, 2007, which is a divisional of U.S. patent application Ser. No. 10/681,330 filed on Oct. 9, 2003, now issued as U.S. Pat. No. 7,274,356, the entire contents of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10681330 | Oct 2003 | US |
| Child | 11762198 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11762198 | Jun 2007 | US |
| Child | 13407285 | US |
