Abstract:
A low profile touch display can be provided, namely one including an optical detection system with the bulk of the electronics and optics positioned partially or completely below the detecting plane surface. The light source and optical detection system components can be configured so that the exit and entry apertures for light being directed to and/or received from the detection plane are the only members above the touch surface. For instance, a reflective or refractive member at the edge of the touch surface can direct light to detection optics and/or from illumination sources via a pinhole aperture, with the light moving between the detection optics and illumination sources in one or more detection planes above the touch surface. Consequently, the touch screen can have a thin cross section that is more suitable for devices such as mobile phones, PDAs, and other portable computing devices for which minimal device thickness is a priority.

Description:
PRIORITY CLAIM 
       [0001]    This application claims priority to New Zealand Provisional Patent Application No. 561,038, filed on Aug. 30, 2007 and entitled OPTICAL TOUCHSCREEN ENABLING THIN CROSS SECTION, which is hereby incorporated by reference herein in its entirety. 
       TECHNICAL FIELD 
       [0002]    The present subject matter generally pertains to touch display systems that allow a user to interact with one or more processing devices by touching on or near a surface. 
       BACKGROUND 
       [0003]    Digitizers and tablets can be incorporated as a coordinate input apparatus in processing units. For instance, the digitizer or tablet can be used alongside one or more display devices (e.g. CRT, LCD, or other display technology) in a touch enabled display assembly. Generally speaking, various systems for detecting an angle (direction) or a position of an object relative to the display area can be used, such as pressure sensitive resistance membrane systems, capacitance systems, electromagnetic induction systems, and the like. As another example, optical systems capable of detecting the angle or the position of the object can be used. 
         [0004]    More particularly, touch screen input devices include resistive, surface capacitive, surface acoustic wave (SAW), infrared (IR), Frustrated Total Internal Reflection (FTIR), Projected capacitive, optical and bending wave. Often, the foregoing touch screen devices (aside from some optical and infrared technologies) require use of a touch enabled transparent cover layer that adds height to the display assembly. 
         [0005]    Certain optical and infrared systems rely on detection of light traveling in optical paths that lie in one or more detection planes in an area (“touch area” herein) above the touched surface. For example, optical imaging for touch screens can use a combination of line-scan or area image cameras, digital signal processing, front or back illumination, and algorithms to determine a point or area of touch. Components used to emit and detect light in the detection plane(s) can be positioned along one or more edges of the touch screen area as part of a bezel surrounding the touch screen area. Optical touch technology often uses line-scanning or area cameras orientated along one or more edges of the touch surface to image the bezel and track the movement of any object close to the surface of the touch screen by detecting the interruption of an infrared light source. 
         [0006]    In some systems, the light can be emitted across the surface of the touch screen by IR-LED emitters aligned along the optical axis of the camera to detect the existence or non existence of light reflected by a retro-reflective border. If an object is interrupting light in the detection plane, the object will cast a shadow in the retroreflected light. Based on the direction of the shadow as cast toward multiple detectors and the spatial arrangement of the detectors, the object&#39;s location in the detection area can be triangulated. As another example, light can be emitted across the touch area in a grid pattern, with the object&#39;s location determined based on where the grid is interrupted. 
         [0007]    For instance,  FIG. 1  is a cross-sectional view of an exemplary touch detection system  10  in which an optical detection and illumination system  12  and illuminated bezel  14  both extend above a touch surface  18 . In this particular example, the optical detection system and illumination system are combined into a single unit as is known in the art. The plane of touch surface  18  in this example corresponds to the top of display screen  16  or a protective layer positioned above the display screen. Light is emitted from illumination source  20  and is directed along an outgoing optical path  20 . The light is then retroreflected along return optical path  24 , passing into optics  28  (a lens in this example) and detector  26 . In this example, the profile of the touch detection system is 3.2 mm. 
         [0008]    As is known to those of skill in the art, the triangulation principle can be used to calculate the position at which an object impinges on a detection plane via measurements from two or more detection systems.  FIG. 2  provides a top view of an exemplary touch detection system  29  which can identify coordinates within a detection plane  31 . In this example, two optical detection and illumination systems  30  are provided, with respective exemplary paths  34  and  36  showing the route of light emitted from and returned to the illumination/detection systems  30  via reflective components positioned along edges  32 . For example, retroreflective components can be positioned along edges  32  covered by or included in a bezel. 
         [0009]    When an object interrupts the beams as represented at  33 , the location of the interruption can be triangulated based on the change in optical paths across detection plane  31 . For example, an object may cast shadows which are detected by illumination/detection systems  30 , with location  33  triangulated from the direction of the shadows and the known spatial relationship between illumination/detection systems  30 . 
         [0010]      FIG. 3  shows a side view of another exemplary touch detection system  40 . In this example, illuminated stylus  42  is used to intersect detection plane  44 . Light traveling in detection plane  44  may be collected via optics  46  and directed via reflector  48  to detector  50 . In this example, detector  50  is interfaced with detector electronics  52  mounted above the touch surface. For example, detector  50 , electronics  52 , lenses  46 , and reflector  58  may all be built into a bezel surrounding screen  58 . 
         [0011]    The relative complexity of the optical components used to emit and detect light can lead to a profile height of the bezel that is not suitable for all applications. For example, the bezel height may be too large for use in a handheld computing device, such as a mobile phone, or personal digital assistant (PDA). 
         [0012]    RPO Pty Ltd of Australia, attempts to provide a low profile by having the IR emitters and receivers optically connected by wave guides. In the example of  FIG. 4 , touch-enabled display  60  comprises an LCD display  62  surrounded by a plurality of transmit side waveguides  64  and receive side waveguides  66 . Transmit side waveguides provide an optical path from light source  68 , while receive side waveguides provide an optical path to detection electronics (ASIC)  70 . Light from transmit side waveguides  64  forms a grid pattern across display  62  which can be detected by electronics  70 . An object&#39;s location on the detection plane can be determined based on interruptions or other disruptions in the expected grid pattern. For example, source  68  may emit infrared or other light, and interruption of the grid may result in a shadow that diminishes the light received at one or more receive side waveguides  66 . 
         [0013]    Although waveguides  64  and  66  allow for source  68  and electronics  70  to be positioned below the screen surface, the waveguides add cost and complexity to the touch-enabled display. For example, the waveguides may be fragile and require careful handling. As another example, each of several waveguides must be connected to the touchscreen at one end and to electronics  70  at the other end. In short, use of the waveguides can complicate assembly and repair and may lead to a less durable product 
       SUMMARY 
       [0014]    Objects and advantages of the present subject matter will be apparent to one of ordinary skill in the art upon careful review of the present disclosure and/or practice of one or more embodiments of the claimed subject matter. 
         [0015]    In accordance with one or more aspects of the present subject matter, a low profile touch display can feature a touch surface corresponding to the outer surface of the display or a protective layer over the display. A reflective or refractive member at one or more edges of the touch surface can direct light traveling in one or more detection planes above the touch surface to the detection optics of the touch display via one or more pinhole apertures. The bulk of the electronics and optics of the optical detection system are positioned partially or completely below the plane of the touch surface, with only the refractive or reflective members and the exit and entry apertures for light extending above the touch surface. Consequently, the touch display system can have a thin cross section that is well suited for devices such as mobile phones, PDAs, and other portable computing devices for which minimal device thickness is a priority. 
         [0016]    For example, a touch detection system can include an illuminated bezel positioned at an edge of a touch surface and configured to direct light along one or more optical paths laying in a detection plane (or planes) above the plane of the touch surface. The illuminated bezel may reflect, refract, or otherwise scatter light from one or more sources so that light is directed towards an optical detection system. As mentioned above, the touch surface may, for example, correspond to the surface of a display device or a protective surface (e.g. transparent or semi-transparent glass, plastic, or other material) positioned over the display device. 
         [0017]    The touch detection system can further comprise an optical detection system positioned at an edge of the touch surface and partially or completely below the plane of the touch surface. The term “below” is meant to refer to the vertical positioning of the optical detection system relative to the plane of the touch surface and not necessarily its lateral position relative to the edges of the touch surface. 
         [0018]    At one or more edges of the touch surface, the system can include an optical assembly extending above the plane of the touch surface so as to intersect with the detection plane(s), with the optical assembly configured to direct light from an optical path (or paths) laying in the detection plane into the detection system via a pinhole aperture. 
         [0019]    In some embodiments, the illuminated bezel is illuminated by an illumination source positioned at least partially below the plane of the touch surface. The illumination source can be configured to direct light toward an optical assembly through a pinhole aperture and into an optical path lying in the detection plane. 
         [0020]    The illumination source may be positioned alongside the detection components of the optical detection system in some implementations and provide illumination via the same optical assembly that receives light returned from the touch area, with the same optical assembly relaying light up to the detection plane from the source. In such embodiments, the illuminated bezel can reflect, refract, or otherwise scatter light towards the detection components. 
         [0021]    However, in other embodiments, the illumination source may be located at a different location on an edge of the touch surface and direct light through a pinhole aperture having the same size as the first pinhole aperture. The pinhole aperture can lead to a second optical assembly positioned at an edge of the touch surface and extending above the plane of the touch surface so as to intersect with the detection plane. Light can be directed up into the second optical assembly, across the touch area, into the first optical assembly, and then into the optical detection system. 
         [0022]    In certain embodiments, the optical assembly or assemblies extend above the plane of the touch surface by a height approximately equal to the diameter of the pinhole aperture(s). For example, if the pinhole aperture is circular, the diameter can refer to the diameter of the circle, or if the aperture is square, the diameter can refer to the diagonal of the square. More generally, the diameter can refer to the maximum distance across the opening measured along a line that passes through the opening. In some embodiments, the pinhole aperture diameter(s) can be equal to or approximately 0.5 mm, although other diameters could be used, as appropriate. As used herein, “approximately” is meant to convey that the value is within ±20% of the stated value, thus “approximately” 0.5 mm includes 0.5 mm ±0.1 mm. Pinhole apertures can have other shapes in other embodiments. 
         [0023]    The “plane of the touch surface” is used to refer generally to a plane extending through space that, within the touch area, corresponds to the top of the touch surface. For example, the top of the touch surface can correspond to the top of display screen or a protective layer positioned above the display screen in some embodiments. 
         [0024]    Multiple detection systems can be used in some embodiments. For example, a second detection system can be positioned at an edge of the touch surface and configured to receive light directed toward the second detection system via a second pinhole aperture. Depending on the configuration of the touch detection system, a single optical assembly with appropriate characteristics can be used to route light to the respective detection systems, or each detection system can feature a separate corresponding optical assembly extending above the touch surface. 
         [0025]    Some embodiments can include at least one computing device interfaced with the detection system or systems and configured to determine a location at which an object has intersected the detection plane based on data collected from the detection system(s). For example, location may be determined based on the object&#39;s disturbance of the propagation of light in the detection plane(s), such as by detecting variances in illumination intensity (e.g. illumination intensity increases and/or shadows). As one particular example, the “triangulation principle” may be used to determine an object&#39;s location relative to the touch surface area. 
         [0026]    One or more display systems can be included, the display system(s) having a surface positioned parallel to or corresponding the touch surface. For example, an LCD or other type of display can comprise the touch surface. The display systems can, in some embodiments, be interfaced with the at least one computing device. Accordingly, the computing device(s), in conjunction with the touch detection system and displays, can provide a touch-enabled display for use in operating the computing device(s). dr 
       BRIEF DESCRIPTION OF THE DRAWINGS 
       [0027]    A full and enabling disclosure including the best mode of practicing the appended claims and directed to one of ordinary skill in the art is set forth more particularly in the remainder of the specification. The specification makes reference to the following appended figures, in which use of like reference numerals in different features is intended to illustrate like or analogous components: 
         [0028]      FIG. 1  is a diagram illustrating an exemplary prior art illumination and detection system which is positioned above a touch surface; 
         [0029]      FIG. 2  is a diagram generally illustrating the triangulation principle employed in various prior art systems; 
         [0030]      FIG. 3  is a diagram illustrating an optical touch system including detection components above the detection plane in another exemplary prior art system; 
         [0031]      FIG. 4  generally illustrates one prior art solution in which illumination and detection components are positioned behind a touch surface through use of waveguide structures; 
         [0032]      FIG. 5  is a diagram illustrating an exemplary low profile touch detection system according to some aspects of the present subject matter; 
         [0033]      FIG. 6  shows a portion of the exemplary low profile touch detection system shown in  FIG. 5  in closer detail; 
         [0034]      FIG. 7  shows a portion of another exemplary low profile touch detection system according to some aspects of the present subject matter; and 
         [0035]      FIG. 8  is a block diagram illustrating an exemplary touch panel display system as interfaced with an exemplary computing device according to some aspects of the present subject matter. 
     
    
     DETAILED DESCRIPTION 
       [0036]    Reference will now be made in detail to various and alternative exemplary embodiments and to the accompanying drawings, with like numerals representing substantially identical structural elements. Each example is provided by way of explanation, and not as a limitation. It will be apparent to those skilled in the art that modifications and variations can be made without departing from the scope or spirit of the disclosure and claims. For instance, features illustrated or described as part of one embodiment may be used on another embodiment to yield a still further embodiment. Thus, it is intended that the instant disclosure includes modifications and variations as come within the scope of the appended claims and their equivalents. 
         [0037]    Turning now to  FIG. 5 , an exemplary touch detection system  80  configured in accordance with one or more aspects of the present subject matter is shown. In this example, an illuminated bezel  82  directs light from source  86  along optical paths  88  and  90  which lie in detection planes above touch surface  84 . Bezel  82  can be illuminated in any suitable way as will be noted below. As illustrated, touch surface  84  intersects with the surface of display  85 , which is a liquid crystal display (LD) panel. It will be understood that in some embodiments, touch surface  84  may be above the actual surface of a display, such as when a covering is included on the surface of the display. 
         [0038]    Optical detection system  92  is operative to detect light traveling in optical paths such as  88  and  90 . Optical detection system  92  in this example comprises lens  98 , detector  99 , and related electronics. For instance, detector  99  may comprise a CMOS or other suitable light detector interfaced with an ASIC or other suitable circuitry to filter or otherwise process the output of detector  99 . Of course, any suitable detection technology appropriate for detecting light from source  86  can be used. Further, although lens  98  is shown in this example for purposes of clarity, more complex optics may be used, including additional lenses, filters, and/or other suitable components. 
         [0039]    Light traveling along optical paths  88  and  90  is directed into detection system  92  via a pinhole aperture  96  having a diameter d, which may be viewed in closer detail in  FIG. 6 . Although in this example pinhole aperture  96  is round and its size is expressed as a diameter in the traditional sense, it will be understood that pinhole apertures can have other shapes; in such cases, its diameter or size would refer to the length from one side to the other of the aperture, passing through the center. 
         [0040]    Optical assembly  94  is positioned at an edge of touch surface  84  and acts to direct light from one or more detection planes towards pinhole aperture  96 . Optical assembly  94  extends above touch surface  84  to a profile height P equal or approximately equal to the diameter d of pinhole aperture  96 . For instance, diameter d (and thus the profile height of optical assembly  94 ) may be approximately 0.5 mm in some embodiments. 
         [0041]    In example of  FIGS. 5 and 6 , optical assembly  94  is configured to direct light using refraction. Namely, a first facet F 1  of the assembly  94  faces on the outside toward the touch detection area, while a second facet, F 2 , does not. Light entering facet F 2  enters the assembly and is directed out of facet F 1 . Due to refraction the direction of light traveling from facet F 2  to F 1 , and vice versa, is altered. Thus, optical detection system  92  can be positioned at least partially below the plane of touch surface  84 . 
         [0042]    In  FIG. 5 , optical detection system  92  is positioned outside the edges of touch surface  84  and partially below the plane of touch surface  84 , while in  FIG. 6  detection system  92  is depicted as entirely below the plane of touch surface  84 . The relative distance between pinhole aperture  96  and optical assembly  94  can vary; in some embodiments, the aperture is minimally spaced from optical assembly  94 . 
         [0043]      FIG. 7  is an illustration of another exemplary touch detection system  180  as viewed in cross section. In this example, optical detection system  192  is positioned completely below touch surface  184 . Similarly to system  92  in the examples of  FIGS. 5-6 , optical detection system  192  comprises a lens ( 198 ) and detector ( 199 ). In this example, optical assembly  194  comprises a first facet F 1  facing toward the detection area and a second facet F 2  partially facing away from the detection area. In this example, facet F 2  is configured to reflect rays traveling in optical paths  88  and  90  downward through pinhole aperture  196 . This facilitates placement of optical detector assembly  192  completely below touch surface  184 . Optical assembly  194  extends above touch surface  184  to a profile height P equal or approximately equal to the diameter d of pinhole aperture  196 . As noted above, in some embodiments, d is equal or approximately equal to 0.5 mm. 
         [0044]    In any event, an optical assembly  82 ,  94 ,  194  can comprise any suitable material or materials. For instance, in some embodiments, polycarbonate or acrylic plastics can have suitable cost, durability, and clarity characteristics. 
         [0045]      FIG. 8  is a block diagram illustrating an exemplary touch detection system  280  as interfaced to an exemplary display  250  and a computing device  201  in accordance with certain aspects of the present subject matter. Computing device  201  may be functionally coupled to touch screen system  200 , by hardwire and/or wireless connections. Computing device  201  may be any suitable computing device, including, but not limited to a processor-driven device such as a personal computer, a laptop computer, a handheld computer, a personal digital assistant (PDA), a digital and/or cellular telephone, a pager, a video game device, etc. These and other types of processor-driven devices will be apparent to those of skill in the art. As used in this discussion, the term “processor” can refer to any type of programmable logic device, including a microprocessor or any other type of similar device. 
         [0046]    Computing device  201  may include, for example, a processor  202 , a system memory  204 , and various system interface components  206 . The processor  202 , system memory  204 , a digital signal processing (DSP) unit  205  and system interface components  206  may be functionally connected via a system bus  208 . The system interface components  206  may enable the processor  202  to communicate with peripheral devices. For example, a storage device interface  210  can provide an interface between the processor  202  and a storage device  211  (removable and/or non-removable), such as a disk drive. A network interface  212  may also be provided as an interface between the processor  202  and a network communications device (not shown), so that the computing device  201  can be connected to a network. 
         [0047]    A display screen interface  214  can provide an interface between the processor  202  and display device  250 . For instance, interface  214  may provide data in a suitable format for rendering by display device  250 . Although not illustrated, computing device  201  may include additional components dictated by its intended function. For example, if computing device  201  comprises a cellular telephone, appropriate transmission and reception components may be included. As another example, computing device  201  may include networking components as noted above, such as a radio transmitter/receiver for communication using one or more wireless standards such as those governed by IEEE 802.11. 
         [0048]    In this example, touch screen  250  is bounded by edges  251 ,  252 ,  253 , and  254 . For instance, a bezel may be used to protect the edges of screen  250 . Further, the edges of touch surface  284  correspond to edges  251 ,  252 ,  253 , and  254 . As was noted above, touch surface  284  may correspond to the outer surface of display  250  or may correspond to the outer surface of a protective material positioned on display  250 . Although in this example the touch screen is enabled to detect an object&#39;s position relative to the entire display area, in other embodiments, the system may be operative to detect an object&#39;s position relative to only a part of the display area. 
         [0049]    In any event,  FIG. 8  further illustrates a plurality of light sources  282 A and  282 B positioned at edge  252  and optical detection assemblies  292 A and  292 B positioned along edge  254 . Since sources  282  and assemblies  292  are at least partially below touch surface  284 , sources  282  and assemblies  292  are illustrated in phantom. In this example, optical assemblies  286 A and  286 B are shown along edge  252  for relaying light from sources  282  to optical paths in one or more detection planes above touch surface  284 , while optical assemblies  294 A and  294 B are shown along edge  254  for relaying light from the detection plane(s) to detection assemblies  292 . 
         [0050]    One or more input/output (“I/O”) port interfaces  216  may be provided as an interface between the processor  202  and various input and/or output devices. For example, the detection assemblies  292  or other suitable components of the touch screen system may be connected to the computing device  201  via an input port and may provide input signals to the processor  202  via an input port interface  216 . Similarly, the light sources  282  of the touch screen system may be connected to the computing device  201  by way of an output port and may receive output signals (e.g. illumination timing and level controls) from the processor  202  via an output port interface  216 . 
         [0051]    A number of program modules may be stored in the system memory  204  and/or any other computer-readable media associated with the storage device  211  (e.g., a hard disk drive) or otherwise accessible by computing device  201 . The program modules may include an operating system  217 . The program modules may also include an information display program module  219  comprising computer-executable instructions for displaying images or other information on a display screen  250 . Other aspects of the exemplary embodiments of the invention may be embodied in a touch screen control program module  221  for controlling the energy sources  282  and/or detector assemblies  292  and/or for calculating touch locations and discerning interaction states relative to the touch screen  250  based on signals received from the detector assemblies. 
         [0052]    In some embodiments, a DSP unit is included for performing some or all of the functionality ascribed to the Touch Panel Control program module  221 . As is known in the art, a DSP unit  205  may be configured to perform many types of calculations including filtering, data sampling, and triangulation and other calculations and to control the modulation and/or other characteristics of light sources  282 . The DSP unit  205  may include a series of scanning imagers, digital filters, and comparators implemented in software. The DSP unit  205  may therefore be programmed for calculating touch locations and discerning other interaction characteristics as known in the art. 
         [0053]    The processor  202 , which may be controlled by the operating system  217 , can be configured to execute the computer-executable instructions of the various program modules. Methods in accordance with one or more aspects of the present subject matter may be carried out due to execution of such instructions. Furthermore, the images or other information displayed by the information display program module  219  may be stored in one or more information data files  223 , which may be stored on any computer readable medium associated with the computing device  201 . 
         [0054]    As discussed above, when a user touches on or near the touch screen  250 , a variation will occur in the intensity of the energy beams that are directed across the surface of the touch screen in one or more detection planes. The detector assemblies  292  are configured to detect the intensity of the energy beams reflected or otherwise scattered across the surface of the touch screen  250  and should be sensitive enough to detect variations in such intensity. Information signals produced by the detector assemblies  292  and/or other components of the touch screen display system may be used by the computing device  201  to determine the location of the touch relative to the touch screen  250 . Computing device  201  may also determine the appropriate response to a touch on or near touch screen  250 . 
         [0055]    In accordance with some implementations, data from the detector assemblies may be periodically processed by the computing device  201  to monitor the typical intensity level of the energy beams directed along the detection plane(s) when no touch is present. This allows the system to account for, and thereby reduce the effects of, changes in ambient light levels and other ambient conditions. Computing device  201  may optionally increase or decrease the intensity of the energy beams emitted by the light sources  282 , as needed. Subsequently, if a variation in the intensity of the energy beams is detected by the detector assemblies, the computing device  201  can process this information to determine that a touch has occurred on or near the touch screen  250 . 
         [0056]    The location of a touch relative to the area of touch screen  250  may be determined, for example, by processing information received from each detector assembly  292  and performing one or more well-known triangulation calculations. By way of illustration, the computing device  201  may receive information from each detector assembly  292  that can be used to identify the position of an area of increased or decreased energy beam intensity relative to each detector assembly. The location of the area of decreased energy beam intensity relative to each detector assembly may be determined in relation to the coordinates of one or more pixels, or virtual pixels, of screen  250 . The location of the area of increased or decreased energy beam intensity relative to each detector may then be triangulated, based on the geometry between the detector assemblies  292  to determine the actual location of the touch relative to the touch screen  250 . 
         [0057]    Any such calculations to determine touch location and/or interaction state can include algorithms to compensate for discrepancies (e.g., lens distortions, ambient conditions, damage to or impediments on the touch screen  100  or other touched surface, etc.), as applicable. 
         [0058]    The locations and number of illumination sources  282 , optical assemblies  286  and  294 , and detector assemblies  292  in  FIG. 8  are for purposes of example only. For instance, more or fewer illumination sources  282  and corresponding optical assemblies  286  could be used. Similarly more or fewer detector assemblies  292  and corresponding optical assemblies  294  could be used. 
         [0059]    For example, rather than using triangulation, the system may establish a grid across the display surface using a plurality of illumination pinhole apertures and corresponding receiving pinhole apertures configured to direct light down to optical detection assemblies. For good resolution, several illumination sources and corresponding detection assemblies could be used. 
         [0060]    In some embodiments, rather than discrete optical assemblies  294 A and  294 B, a continuous optical assembly can be provided along an edge, with the detector assemblies  292  and corresponding pinhole apertures located along the edge at different locations. Similarly, a continuous optical assembly  286  could be used in conjunction with multiple sources  282 . 
         [0061]    In certain embodiments, optical units comprising both detector assemblies and illumination sources are used. For instance, a detector assembly can include illumination sources that illuminate a retroreflector that returns the light to its point of origin. See, for instance, U.S. Pat. No. 6,362,468. In such embodiments, the same optical assembly and pinhole aperture could be used to route light from the illumination sources and across the detection plane and also return retroreflected light. 
         [0062]    The above examples referred to various illumination sources and it should be understood that any suitable radiation source can be used. For instance, light emitting diodes (LEDs) may be used to generate infrared (IR) radiation that is directed over one or more optical paths in the detection plane. However, other portions of the EM spectrum or even other types of energy may be used as applicable with appropriate sources, detection systems, and optical (or other) units that redirect the energy to and from the detection plane. 
         [0063]    Several of the above examples were presented in the context of a touch-enabled display. However, it will be understood that the principles disclosed herein could be applied even in the absence of a display screen when the position of an object relative to an area is to be tracked. 
         [0064]    The various systems discussed herein are not limited to any particular hardware architecture or configuration. As was noted above, a computing device can include any suitable arrangement of components that provide a result conditioned on one or more inputs. Suitable computing devices include multipurpose microprocessor-based computer systems accessing stored software, but also application-specific integrated circuits and other programmable logic, and combinations thereof. Any suitable programming, scripting, or other type of language or combinations of languages may be used to implement the teachings contained herein in software. 
         [0065]    Embodiments of the methods disclosed herein may be executed by one or more suitable computing devices. Such system(s) may comprise one or more computing devices adapted to perform one or more embodiments of the methods disclosed herein. As noted above, such devices may access one or more computer-readable media that embody computer-readable instructions which, when executed by at least one computer, cause the at least one computer to implement one or more embodiments of the methods of the present subject matter. When software is utilized, the software may comprise one or more components, processes, and/or applications. Additionally or alternatively to software, the computing device(s) may comprise circuitry that renders the device(s) operative to implement one or more of the methods of the present subject matter. 
         [0066]    Any suitable computer-readable medium or media may be used to implement or practice the presently-disclosed subject matter, including, but not limited to, diskettes, drives, magnetic-based storage media, optical storage media, including disks (including CD-ROMS, DVD-ROMS, and variants thereof), flash, RAM, ROM, and other memory devices, and the like. 
         [0067]    While the present subject matter has been described in detail with respect to specific embodiments thereof, it will be appreciated that those skilled in the art, upon attaining an understanding of the foregoing may readily produce alterations to, variations of, and equivalents to such embodiments. Accordingly, it should be understood that the present disclosure has been presented for purposes of example rather than limitation, and does not preclude inclusion of such modifications, variations and/or additions to the present subject matter as would be readily apparent to one of ordinary skill in the art