US20130120315A1 - Systems and Sensors for Tracking Radiation Blocking Objects on a Surface - Google Patents
Systems and Sensors for Tracking Radiation Blocking Objects on a Surface Download PDFInfo
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- US20130120315A1 US20130120315A1 US13/379,476 US201013379476A US2013120315A1 US 20130120315 A1 US20130120315 A1 US 20130120315A1 US 201013379476 A US201013379476 A US 201013379476A US 2013120315 A1 US2013120315 A1 US 2013120315A1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V8/00—Prospecting or detecting by optical means
- G01V8/10—Detecting, e.g. by using light barriers
- G01V8/20—Detecting, e.g. by using light barriers using multiple transmitters or receivers
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
- G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
- G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
- G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
- G06F3/046—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means by electromagnetic means
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
- G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
- G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
- G06F3/033—Pointing devices displaced or positioned by the user, e.g. mice, trackballs, pens or joysticks; Accessories therefor
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
- G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
- G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
- G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
- G06F3/042—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means by opto-electronic means
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
- G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
- G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
- G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
- G06F3/042—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means by opto-electronic means
- G06F3/0428—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means by opto-electronic means by sensing at the edges of the touch surface the interruption of optical paths, e.g. an illumination plane, parallel to the touch surface which may be virtual
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- General Life Sciences & Earth Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Electromagnetism (AREA)
- Measurement Of Radiation (AREA)
- Position Input By Displaying (AREA)
- Length Measuring Devices By Optical Means (AREA)
- Photometry And Measurement Of Optical Pulse Characteristics (AREA)
Abstract
Several systems for tracking one or more radiation blocking objects on a surface are disclosed. A pair of radiation sensors are provided adjacent the surface and a plurality of radiation sources are provided adjacent the surface. Radiation from at least some of the radiation sources travels across the surface to reach each of the radiation sensors. One or more radiation blocking objects on the surface attenuate radiation from one or more radiation sources from reaching each of the sensors. The position of the one or more radiation blocking objects is estimates and may be tracked based on the position of the one or more attenuated radiation sources relative to each radiation sensor.
Description
- The described embodiments relate to systems, methods and sensors for sensing and tracking the position of one or more radiation blocking objects on a surface.
- A variety of computer input and other devices require tracking of one or more objects such as fingers, styluses, pens or other objects as they positioned on or moved across a surface. For example, computer monitors and other display screens may be fitted with a touchscreen that allows a user to provide inputs to a computer using a finger or a stylus, as they are moved across the display surface of the screen. Similarly, a whiteboard may be fitted with a pen positioning sensing system that tracks the position of one or more pens as they are moved across the writing surface of the whiteboard.
- Existing systems suffer from a variety of deficiencies, including excessive complexity and cost, high computational overhead that affects both their accuracy and response time, and other deficiencies.
- The present invention provides various systems for detecting the presence and position of one or more radiation blocking objects as the radiation blocking objects are positioned on or moved across a surface. The surface may be any type of surface such as the display surface of computer monitor or other display device, a writing surface such as a whiteboard, bulletin board, sheet of paper or wall or another surface such as a part of a toy or game.
- Various embodiments according to a first aspect of the invention include a frame or housing with a plurality of radiation sources and radiation sensors mounted on it. The frame will typically, but not necessarily, be mounted to or be combined with a housing, frame or support of an underlying system such as a whiteboard, a display monitor, a bulletin board, a game, toy or other device. In some embodiments, the frame or housing may be combined with a display monitor to form a touchscreen. A controller activates some or all of the radiation sources sequentially. The radiation sources may be activated in a sweep fashion from one side of the frame to the other, or they may be activated in a different order. While each radiation source is activated, the radiation incident on some or all of the radiation sensors is measured.
- A radiation blocking object present within the frame will typically block or attenuate one or more of the paths between some of the radiation sources and some of the radiation sensors. By successively measuring the attenuation of radiation from such blocking, the position of the radiation blocking object is estimated.
- In embodiments according to another aspect of the invention, one or more diffusers are used to diffuse radiation emitted by the radiation sources. The diffusers may allow the position of a radiation blocking object to be estimated more accurately, particularly when the radiation blocking object blocks two or more of the paths between the radiation sources and a radiation sensor.
- In some embodiments, radiation emitted by the radiation sources is modulated at a modulation frequency or with a modulation pattern. The sensors are sensitive to the modulation frequency or pattern and ignore radiation that is not modulated according the frequency or pattern, reducing the effect of ambient and other spurious radiation in estimating the position of a radiation blocking object.
- In one aspect, a system for sensing the position of one or more radiation blocking objects on a surface is provided. The surface is mounted to or within a frame, and in some embodiments, the surface and frame are generally rectangular. Radiation sources are provided on the frame and emit radiation across the surface. Radiation sensors are provided at two or more positions on the frame. Each sensor is positioned such that radiation from a plurality of the radiation sources may be incident on each the sensor. Each sensor provides a radiation intensity level corresponding to the intensity of radiation incident on it to a controller. The controller is coupled to the radiation sources and sequentially activates the radiation sources. As each radiation source is activated, radiation from the radiation source may be incident on some or all of the radiation sensors. The controller samples the radiation intensity level from the radiation sensors. When a radiation blocking object is present on the surface, the radiation blocking object will typically block or attenuate radiation from one or more of the radiation sources. The controller identifies radiation sources for which the radiation intensity signal is attenuated compared to a baseline or threshold intensity level.
- The controller estimates the position of the radiation blocking object based on the position of the attenuated radiation sources (i.e. radiation sources for which the radiation intensity level is attenuated due to the presence of a radiation blocking object) as measured from each radiation sensor. The controller first estimates an angular direction of the radiation blocking object relative to at least two of the radiation sensors. The angular directions are combined to estimate the position of the radiation blocking object on the surface relative to a reference position.
- In some embodiments, the controller combines the radiation intensity levels samples from a radiation source into a radiation intensity signal and identifies ranges of attenuated radiation sources. A center radiation source within the range is identified, and the angular position of the radiation blocking object relative to at least one of the radiation sensors is estimated based on the center radiation source in each radiation intensity signal.
- In other embodiments, the relative attenuation of radiation intensity signals may be combined to estimate the position of the radiation blocking object. For example, if a range of radiation intensity levels corresponding to a range of radiation sources are attenuated by a radiation blocking object, a weighted average based on the relative attenuations and positions of each radiation source is used to refine the estimated angular position of the radiation blocking object relative to each radiation sensor. The refined estimate angular positions are combined to provide an estimated position of the radiation blocking object relative to the reference position.
- In some embodiments, multiple radiation blocking objects on the surface may be sensed. The controller analyzes radiation intensity signals from each of the radiation sensors to identify attenuated radiation intensity levels corresponding to the presence of one or more radiation blocking objects. The maximum number of radiation blocking objects identified in any one radiation intensity signal is assumed to be the minimum number of radiation blocking objects present on the surface. The controller estimates an angular direction for each radiation blocking object apparently visible from each radiation sensor, relative to the sensors. The angular positions are combined to estimate the position of each radiation blocking object. The prior positions of radiation blocking objects, when such prior positions are known, may be used to select likely current positions of radiation blocking objects when the angular directions can lead to different estimates. For example, in some embodiments, two angular directions are identified relative to each of two radiation sensors. The angular directions can be represented as lines originating from each of the sensors. The lines intersect at four points, which may be considered in pairs to be potential positions of two radiation blocking objects. Previously known positions for one or both radiation blocking objects are used by calculating the shortest movement required from the previous positions of the radiation blocking objects to the potential current positions based on the intersections. The radiation blocking objects are deemed to be located at the potential position that requires the shortest movement. In other embodiments, other criteria may be used to resolve between different potential positions. For example, the trajectory of a radiation blocking object over a preceding time period, a distance or number of iterations of a sensing process may be used to estimate the current position of a radiation blocking object.
- These and other aspects of the invention are described below in a description of the some example embodiments of the invention.
- Various embodiments of the invention will now be described with reference to the drawings, in which:
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FIG. 1 illustrates a first system according to the present invention; -
FIGS. 2 a and 2 b illustrate radiation intensity signals according to the system ofFIG. 1 ; and -
FIG. 3 illustrates a radiation intensity signal according to another embodiment; -
FIG. 4 illustrates a radiation intensity signal according to yet another embodiment; -
FIGS. 5 a and 5 b illustrate another embodiment; -
FIG. 6 illustrates another embodiment; -
FIG. 7 illustrates yet a further embodiment with several radiation blocking embodiments in a position; -
FIG. 8 illustrates a method of identifying or estimating the positions of radiation blocking objects on a surface using the system ofFIG. 7 . -
FIGS. 9 a and 9 b illustrate radiation intensity signals corresponding to one of the radiation blocking objects ofFIG. 7 ; -
FIGS. 10 a and 10 b illustrate radiation intensity signals corresponding to both of the radiation blocking objects ofFIG. 7 ; -
FIG. 11 illustrates the system ofFIG. 7 with the radiation blocking objects in a different position; -
FIGS. 12 a and 12 b illustrate radiation intensity signals corresponding toFIG. 11 ; -
FIG. 13 illustrates the system ofFIG. 7 with the radiation blocking objects in a different position; and -
FIGS. 14 a and 14 b illustrate radiation intensity signals corresponding toFIG. 13 . - The drawings are illustrative only and are not drawn to scale. Various elements of some embodiments may not be shown for clarity. Similar and corresponding elements of the various embodiments are identified by similar reference numerals.
- Exemplary embodiments described herein provide details relating to systems and methods for determining the position of one or more radiation blocking objects in relation to various radiation sources and radiation sensors. In some embodiment, the radiation sources and sensor may be mounted in a frame. In some embodiments, the systems may include or be used with various underlying devices such as whiteboards, display monitors and other devices. In some embodiments, the systems may include or be used with an underlying surface such as a whiteboard, a wall, the surface of a display screen or any other generally planar surface. The radiation sources may emit radiation in the visible light spectrum or in other spectrums, such as the ultraviolet or infrared spectrums. The embodiments described herein are exemplary only and other implementations and configurations are also possible.
- Reference is first made to
FIG. 1 , which illustrates asystem 100 for sensing or estimating the position of aradiation blocking object 124.System 100 includes a pair ofradiation sensors controller 104 and a plurality ofradiation sources 106 mounted on a frame orhousing 108.Frame 108 has atop side 110,bottom side 112,left side 114 and aright side 116. In this embodiment,radiation sources 106 are mounted on the left, bottom and right sides offrame 108.Radiation sensor 102 a is mounted at the top left corner of theframe 108 andradiation sensor 102 b is mounted at the top right corner of theframe 108. -
Frame 108 surrounds asurface 128. In various embodiments, thesurface 128 may be the surface of a display screen, a writing surface or another surface. In this embodiment,frame 108 provides a bezel at the edges of thesurface 128.Radiation sources 106 and radiation sensors 102 are mounted within the bezel. In some embodiments, the frame may only partially surround or enclose the surface, for example, the frame may not enclose the top edge of the surface if no radiation sensors or sources are mounted adjacent the top edge. In other embodiments, the frame may support but not enclose the surface. For example, the frame may provide a support for the surface, radiation sensors and radiation sources, but may not have a bezel or other element that surrounds the surface. In other embodiments, the frame may itself provide some or all of the surface. For example, the frame may have solid surface between its edges and radiation blocking objects may be positioned on the solid surface whensystem 100 is in use. Typically, as in these examples, the surface will be mounted to the frame. - The top left corner of
frame 108 is cut away inFIG. 1 to revealradiation sensor 102 a andseveral radiation sources 106. The bottom right corner offrame 108 is also cut away to reveal some of the radiation sources 106. Eachradiation source 106, in this embodiment, is a LED that emits radiation in the infra-red spectrum. In other embodiments, the radiation sources may be various types of sources that emit radiation in other spectrums, including the visible light spectrum and the UV spectrum.Radiation sources 106 are mounted onframe 108 such that radiation from the radiation sources reaches one or both of the radiation sensors 102. In this embodiment, radiation sources are equally spaced along the left, bottom and right sides offrame 108. In this embodiment,frame 108 is rectangular with square corners. The sides offrame 108 are parallel to the axes of an x-y plane. In some embodiments, the radiation sources may not be equally spaced. In some embodiments, the frame may have a non-rectangular shape. -
Controller 104 includes aprocessor 120, which may any type of device or component capable of operatingsystem 100, including a hardware component, a software component or a component including both hardware and software or firmware or both. For example,processor 120 may be a microprocessor, microcontroller, gate array or any type of data processing or computing device. The processor can be programmed or configured to operatesystem 100 and its components and to communicate with external devices.Controller 104 may also includes amemory 121, which may be accessed byprocessor 120.Processor 120 controls the operation ofcontroller 104 andsystem 100. Instructions may be recorded in thememory 121, and may be loaded into the processor to configure the processor to perform control, data processing, data transformation and communication operations for controlling the operation of thecontroller 104 and thesystem 100 as described below.Controller 104 is coupled to eachradiation source 106. Only some of these connections are illustrated inFIG. 1 .Controller 104 is capable of activating eachradiation source 106 independently so that when one radiation source is activated or on (i.e. emitting radiation) the remaining radiation sources are not activated or off (i.e. not emitting radiation). - In this embodiment, each radiation sensor 102 is a PIN photodiode that is capable of sensing radiation emitted by the
radiation sources 106 on the two opposing sides offrame 108.Radiation sensor 102 a senses radiation emitted by theradiation sources 106 on the bottom and right sides offrame 108.Radiation sensor 102 b senses radiation emitted by theradiation sources 106 on the bottom and left sides offrame 108. Each radiation sensor 102 is coupled tocontroller 104 and provides a radiation intensity level to the controller corresponding to the intensity of radiation falling on the radiation sensor 102 at any particular time. The radiation intensity level has a relatively high value when the corresponding radiation sensor 102 is receiving radiation from aradiation source 106 and a relatively low value when the corresponding radiation sensor 102 is not receiving radiation from aradiation source 106. A series of radiation intensity levels corresponding to theradiation sources 106 may be combined or assembled into a radiation intensity signal that can be used to estimate the position of theradiation blocking object 124. This is explained below. - In other embodiments each radiation sensor may be any device that is responsive to the radiation emitted by the radiation sources and capable of providing a radiation intensity level corresponding to radiation incident on the sensor. For example, a light sensitive element such as a photosensor, photodiode, photocell, a solar cell or a photovoltaic cell may be used to provide radiation intensity levels. The radiation sensor may provide the output radiation intensity level in any format compatible with the
controller 104, including a digital or analog format. -
Controller 104 is programmed with the dimensions offrame 108, the position of eachradiation source 106 and the positions of each radiation sensor 102. In this example,controller 104 is programmed with the following information: -
-
Sensors Radiation sensor 102 a is at the (0,0) position on the x-y plane andradiation sensor 102 b is at the (d,0) position on the x-plane. - For each radiation source on the bottom or right side of the
frame 108, the angle between the left side of the frame (or a line parallel to the left side of the frame, depending on the position of theradiation sensor 102 a) and the path betweenradiation sensor 102 a and the radiation source, or a value corresponding to the angle. - For each radiation source on the left or bottom side of the
frame 108, the angle between the right side of the frame (or a line parallel to the right side of the frame, depending on the position of theradiation sensor 102 b) and the path betweenradiation sensor 102 b and the radiation source, or a value corresponding to the angle.
-
- Under the control of
controller 104,system 100 is operable to estimate the physical position P124a(x124a, y124 a) ofradiation blocking object 124. InFIG. 1 ,radiation blocking object 124 is illustrated as a stylus. The tip of the stylus is in contact with thesurface 128, at point P124, which corresponds to the physical position P124a discussed here and the pixel position P124d discussed below. - In operation,
controller 104 sequentially activates the radiation sources 106. While aradiation source 106 is activated,controller 104 samples the output from one or both of the radiation sensors 102 to obtain a radiation intensity level corresponding to the intensity of radiation incident on each radiation sensor 102. Typically, the path between the radiation source and each radiation sensor will be blocked, partially blocked (ie. partially attenuated) or clear. In some embodiments, while aradiation source 106 is activated, the controller may only check the radiation intensity level for a radiation sensor 102 if there is a direct path between theradiation source 106 and the radiation sensor 102. For example, there is a direct path betweenradiation sensor 102 a and theradiation sources 106 on thebottom side 112 and theright side 116 offrame 108. Similarly, there is a direct path betweenradiation sources 106 on theleft side 114 and thebottom side 112 of theframe 108 andradiation source 102 b. In other embodiments, thecontroller 104 may check the radiation intensity level at a radiation sensor 102 even when the activatedradiation source 106 does not have a direct path to the radiation sensor. - Instructions for performing this process are recorded in
memory 121.Processor 120 accesses the instructions inmemory 121 an executes the instructions to perform the process described above and those described below.Processor 120 may also record data inmemory 121 during the performance of this process. - In other embodiments, the specific placement of the radiation sources and radiation sensors and the shape of the frame (which need not be rectangular and may have another shape) will effect which radiation sources have a direct path to which radiation sensors.
- Returning to the present embodiment, when
radiation source 106 a is activated,controller 104 need not sampleradiation sensor 102 a to obtain a radiation intensity level because there is no direct path betweenradiation source 106 a andradiation sensor 102 a that is not obstructed byother radiation sources 106.Controller 104 does sample the radiation intensity level provided byradiation sensor 102 b, which will have a relatively high value indicating that the path betweenradiation source 106 a andradiation sensor 102 b is clear, or not blocked. - When
radiation source 106 c is activated,controller 104 samples bothradiation sensors radiation sensor 102 a is relatively high, indicating that the path betweenradiation source 106 c andradiation sensor 102 a is clear. The radiation intensity level fromradiation sensor 102 b is relatively low, indicating that the path betweenradiation source 106 c andradiation sensor 102 b is blocked, in this example, byradiation blocking object 124. - When
radiation source 106 e is activated, the radiation intensity levels fromradiation sensors radiation source 106 e andradiation sensors - When
radiation source 106 f is activated,controller 104 samples the radiation intensity level fromradiation source 102 a which indicates that the path betweenradiation source 106 f andradiation sensor 102 a is blocked byradiation blocking object 124.Controller 104 samples the radiation intensity level fromradiation sensor 102 b, which indicates that the path betweenradiation source 106 f andradiation sensor 102 a is clear. - As
controller 104 sequentially activates the radiation sources and samples the radiation intensity levels corresponding to eachradiation source 106,controller 104 records the outcomes as follows: -
Radiation Path to Radiation Path to Radiation source Sensor 102aSensor 102b . . . — . . . 106a — Clear . . . . . . . . . 106c Clear Blocked . . . . . . . . . 106e Clear Clear . . . . . . . . . 106f Blocked — . . . . . . — - Reference is made to
FIGS. 2 a and 2 b.FIG. 2 a illustrates aradiation intensity signal 122 a corresponding to the radiation intensity levels obtained bycontroller 104 fromradiation sensor 102 a.FIG. 2 b illustrates aradiation intensity signal 122 b corresponding to the radiation intensity levels obtained bycontroller 104 fromradiation sensor 102 b. Each radiation intensity signal comprises the output ofradiation sensor 102 b as the radiation sources, includingradiations sources - Using the radiation intensity signals 122 a and 122 b,
controller 104 can estimate the physical position ofradiation blocking object 124.Controller 104 assumes that theradiation block object 124 is located in the blocked path for each radiation sensor. In this example, the position P124a(x124a, y124a) for theradiation blocking object 124 can be estimated: -
- In the embodiment of
FIG. 1 , the resolution with which the position ofradiation blocking object 124 can be estimated depends on a number of factors, including the spacing between the radiation sources 106. By placing the radiation sources close to one another, a greater resolution may be achieved. - In equations (1) and (2) above, the tan of angles θf and φc are used to calculate the position of point P124. In
system 100, the tan of the angles θ between theleft side 114 and the path to theradiation sources 106 visible toradiation detector 102 a, and the tan of the angles φ between theright side 116 and path to theradiation sources 106 visible toradiation sensor 102 b are recorded in a data storage location accessible to thecontroller 104. This allows equations (1) and (2) to be calculated without requiring the tan of each angle θf and φc to be calculated, thereby allowing the position of P124 to be calculated more rapidly. In other embodiments, the angles themselves may be recorded or another value corresponding to the angles may be recorded. In some embodiments multiple values corresponding to the angular relationship between each of the radiation sources, the radiation sensors and reference lines (such as lines parallel to the right and left edges of the frame) may be recorded. -
System 100 may be operated in different manners, depending on the programming ofcontroller 104. - In another embodiment,
system 100 may be operated to refine the estimated positions P124a of a radiation blocking object on thesurface 128. Reference is made toFIGS. 1 and 3 . Depending on the distance between the radiation sources, the dimensions of the radiation blocking object and the distance between the radiation blocking object and a radiation sensor, the path between several radiation sources and the radiation sensor may be blocked by the radiation blocking object. For example, ifradiation sources radiation blocking object 124 may at least partially block the path between two or all three of the radiation sources andradiation sensor 102 b, thereby attenuating the radiation intensity level for all three radiation sources, particularly if the radiation blocking object is close toradiation sensor 102 b. In some embodiments,controller 104 determines the center radiation source in a range of radiation sources whose path to a particular radiation sensor is blocked. Optionally, thecontroller 104 may treat a radiation source as blocked only if its radiation intensity level is below some threshold level, providing a mechanism for including or excluding slightly attenuated radiation sources at the edges of a range of attenuated radiation sources. In this example, the center radiation source would beradiation source 106 c. The controller then estimates the position of the radiation blocking object based on the angle θ or φ between the center radiation source and the relevant side of the frame 108 (in this case, angle φ, relative to the right side 116). In other embodiments, the controller may use the middle angle θ or φ (depending on the relevant radiation sensor) among the range of angles for the radiation sources that are blocked. If a different value corresponding to each angle relating the radiation sources to the radiation sensors is recorded in thecontroller 104, such as the tan of each angle, then the recorded value may be used after determining the center radiation source or angle. - The estimated position P124a(x124a, y124a) is a physical position, measured in the same units as dimension d that separates
radiation sensors - In some embodiments, the controller may assemble the radiation intensity signal 122 for each of the radiation sensors 102 sequentially rather than contemporaneously, as described above. For example, radiation sources visible to
radiation sensor 102 a may be sequentially activated andradiation intensity signal 122 a may be assembled. Then radiation sources visible tosensor 102 b may be sequentially activated andradiation intensity signal 122 a may be assembled. This process of assembling the radiation intensity signals 122 sequentially rather than contemporaneously allows the intensity of some or all of theradiation sources 106 to be varied for the different radiation sensor 102. Referring toFIG. 1 ,radiation sensor 106 e is closer toradiation sensor 102 b than toradiation sensor 102 a. It may be desirable to activateradiation source 106 e with a higher intensity when assembling a radiation intensity signal forradiation sensor 102 a than when assembling a radiation intensity signal forradiation sensor 102 b. - In other embodiments, the radiation intensity signal may be assembled contemporaneously but at least some of the radiation sources may be activated at different intensities for sampling at different radiation sensors. For example, some radiation sources may be activated two or more times and different radiation sensors may be sampled during each activation. Various other combinations are possible. For example, radiation sources on the
left side 108 may be activated sequentially andradiation sensor 102 b may be sampled while each radiation source is active. Then radiation sources on thebottom side 112 may each be activated twice and each of theradiation sensors right side 116 may be activated andradiation sensor 102 a may be sampled. The radiation intensity levels sampled from each radiation source may be assembled into a radiation intensity signal for that radiation sensor. In another embodiment, some radiation sensors visible to both of the radiation sensors may be about equally distant from each of the radiation sensors and the radiation sensors may be sampled during the same activation of such radiation sources. For example,radiation source 106 b and some nearby radiation sources are sufficiently equally spaced fromradiation sensors - Returning to the present embodiment,
controller 104 is coupled to aninterface 148, which in this embodiment is a universal serial bus port. - In other embodiments, the interface may be any type of communication interface. For example,
interface 148 may be an analog interface or a digital data interface such as a serial data port or a parallel data port. In embodiments where the interface is an analog interface, the controller may provide analog signals (such as a current signal or a voltage signal) corresponding to the value of x124a and y124a. In an embodiment where the interface is a digital interface, the controller may be configured to convert the physical positions x124a and y124a into corresponding digital positions x124d and y124d relative to thesensors - In the present embodiment, the
surface 128 is the surface of a LCD display screen. The LCD display screen has a resolution of X horizontal pixels by Y vertical pixels. For example, in some embodiments, the screen may have a resolution of 1280×1024 pixels or 1920×1080 pixels. In other embodiments a display screen may have any other standard or non-standard pixel resolution.Controller 104 converts the physical position a corresponding pixel position P124d(x124d, y124d).Controller 104 may be configured to do so using a variety of techniques, including the use of lookup tables that provide the horizontal and vertical pixel positions corresponding the horizontal and vertical physical positions, using a formula to convert between the physical and pixel positions or using any other method.Controller 104 provides the digital position P124d at theinterface 148. - Reference is made to
FIGS. 1 and 4 . In another embodiment, thecontroller 104 is configured or programmed differently to estimate the position P124a of theradiation blocking object 124 in a different manner. In this embodiment, the intensity signals 122 are used to more precisely estimate the angular position of theradiation blocking object 124 relative to each radiation sensor 102 and a side of theframe 108. -
FIG. 4 illustrates a portion of aradiation intensity signal 122 b whencontroller 104 is configured according to this embodiment. In this embodiment, thecontroller 104 establishes a baseline intensity level for each radiation source in combination with each radiation sensor. For each radiation source,controller 104 samples the radiation intensity level fromradiation sensor 102 b while the radiation source is on, and in the absence of a radiation blocking object to generate a baseline intensity level 126. The baseline intensity levels forradiation source - In this embodiment, during startup of system, the baseline intensity level is initially determined for each radiation source, with respect to each radiation sensor from which the radiation source is visible (i.e. if there is a direct path between the radiation source and the radiation sensor). An initial set of samples of the intensity signal are discarded while the system is starting up. For a selected time period following this initial start-up period, the radiation intensity level is sampled while the radiation source is on. The radiation intensity level is recorded and an average intensity level is determined for the radiation source at each radiation sensor. For example, if each radiation source is activated 50 times per second, the baseline intensity level may be calculated using the first 25 samples for each radiation source, at each radiation sensor, representing half of a second. In other embodiments, the baseline intensity level may be calculated over more or fewer samples, or for a longer period or shorter period. The baseline intensity level for each radiation sensor inherently takes into account ambient and other conditions affecting the amount of radiation that reaches the radiation sensor when a particular radiation source is switched on. Such other conditions include the amount of radiation emitted by each radiation source, the physical distance between the radiation source and the radiation sensor and may also include the manner in which
system 100 is used. - The baseline intensity level calculated for each
radiation source 106, with respect to each radiation sensor 102, may be updated over time. For example, a moving average of some of the radiation intensity readings over a recent time period may be calculated to refine the baseline level as ambient and other conditions change. Some radiation intensity readings may not be used to calculate the updated baseline intensity level. For example, every tenth or twentieth radiation intensity reading may be used to calculate the moving average for each baseline intensity level. This reduces the amount of data that must be stored to calculate a baseline intensity level corresponding to a longer time period and also reduces the computation time required in the controller to address this task. Typically, the baseline intensity level will be calculated for a recent period from a part of a second to a few seconds or tens of seconds. When the path between aradiation source 106 and a radiation sensor 102 is blocked the radiation intensity level for that source at that sensor will be significantly reduced, although ambient radiation and some radiation may still reach the radiation sensor around the radiation blocking object. The controller may exclude radiation intensity levels below a certain threshold compared to the current baseline intensity level when refining the baseline intensity as is further described below. Various other methods for calculating a baseline intensity level for each radiation source at each radiation sensor may also be used. In some embodiments, one baseline intensity level may be calculated for a group or all of the radiation sensors. In other embodiments a pre-determined intensity level may be used as the baseline intensity level for some or all of the radiation sources. - In this embodiment, each time a
radiation source 106 is activated, the radiation intensity level from each radiation sensor 102 from which the radiation source is visible is sampled and compared to the existing baseline intensity level for that radiation source at that radiation sensor. If the current intensity level is more than some threshold below the baseline intensity level, the percentage difference from the baseline level is calculated. For example, the threshold may be 90% of the baseline intensity level. If the current intensity level is greater than 90% of the baseline level, the current intensity level may be used to further refine the baseline level, or it may be discarded. If it is less than 90% of the baseline level, the processor assumes that the path between theradiation source 106 and the radiation sensor 102 is at least partially blocked. In other embodiments, other threshold levels may be used. - The controller successively activates the radiation sources in a cyclic process. After each cycle of switching on the radiation sources 106 and measuring the radiation intensity level from each radiation sensor for the radiation sources, the controller estimates the position of the radiation blocking object. As noted above,
-
FIG. 4 illustrates the attenuation ofseveral radiation sources 106 relative to its baseline level 126. The current intensity level forradiation source 106 a, as measured at radiation sensor 102 is greater than 90% of thebaseline intensity level 126 a, so it is ignored for the purpose of estimating the position of theradiation blocking object 124, although the current intensity level may be used to refine the baseline level forradiation source 106 a as measured atradiation sensor 102 b. Similarly, the current intensity level forradiation source 106 b is greater than 90% ofbaseline intensity level 126 b, so it is ignored for the purpose of estimating the position of the radiation blocking element, but may be used to refine the baseline level, which would then be slightly higher. - The current intensity levels for radiation sources a 106 c and 160 d are below 90% of their
respective baseline levels radiation source 106 c is at 53% ofbaseline intensity level 126 c. The current intensity level forradiation source 106 d is at 31% of thebaseline intensity level 126 d.Controller 104 normalizes these deviations to a total of 100%: the relative attenuation of radiation fromradiation source 106 c represents 63% of the total attenuation (31%/84%=63%); and the relative attenuation of radiation fromradiation source 106 d represents 37% of the total attenuation. - The angle φ between the
right side 116 and a line 132 betweenradiation source 102 b andradiation blocking object 124 is then estimated as follows. The angle φc forradiation source 106 c is 44°. The angle φd (not shown) corresponding toradiation source 106 d is 42°. In this embodiment, rather than recording the angles themselves, the tan of each angle is recorded. The tan of the angle φ124 between the left side of theframe 108 and the path betweenradiation sensor 102 b andradiation blocking object 124 can then be estimated as follows: -
- In an embodiment in which the angles themselves are recorded, angle φ124 may be estimated as follows:
-
- The estimates of angle φ124 differ due to the non-linearity between an angle and its tangent.
- An angle θ124 is calculated for the angle between
left side 114 and the line betweenradiation sensor 102 a and theradiation blocking object 124. The two calculated angles φ124 and θ124 are used to estimate the position (xb, yb) of theradiation blocking object 124. - In this manner,
controller 104 may use the attenuation of two or more radiation sources as measured at one of the radiation sensors to estimate the angular position of radiation blocking object relative to the left or right side of theframe 108 and one of the radiation sensors 102 by normalizing the relative attenuations of the different radiation sources and then calculating a weighted average of the angle of those sources from the relevant side of the frame and the radiation sensor. - This embodiment may allow the position of the
radiation blocking object 124 to be estimated more accurately than the first embodiment by allowing angles θ and φ to be estimated between the specific angles at which theradiation sources 106 are positioned. -
System 100 may be used in various configurations to identify the position of various types of radiation blocking objects 124. For example,system 100 may be used with a whiteboard or other display surface.Frame 108 may be attached to the edge or frame of the whiteboard, or may also be the frame of the whiteboard. Theradiation blocking object 124 may be a pen used to write on the whiteboard and as the pen is moved about the surface of the whiteboard, its position is estimated bycontroller 104.Controller 104 may be coupled to (or may be part of) a whiteboard system for recording estimates of the pen's position. By recording successive estimates of the pen's position, information on the whiteboard may be recreated in an electronic form and may be recorded for subsequent use, and it may be displayed or printed. The whiteboard system may include software to calculate the path of movement of the pen between estimated positions and to smooth the calculated path. - As the pen is used to write on the whiteboard, the ink on the whiteboard may change the amount of ambient light reflected on to a radiation sensor 102 and could also change the amount of radiation propagating from a
radiation source 106 to a radiation sensor 102, thereby affecting the level of the radiation intensity measured for some or all of the radiation sources 106. In such embodiments, periodically updating the baseline intensity level for some or all of the radiation sources may improve the accuracy of estimates of the position of a radiation blocking object. - In other embodiments,
system 100 may be used with a display monitor or screen to form a touchscreen.Frame 108 may be mounted to the display monitor or may be part of the display monitor's housing. Theradiation blocking object 124 in this case may be a finger, and as a person moves their finger onto or off of the display monitor, the presence of the finger is detected and its position on the display screen is estimated bycontroller 104.Controller 104 may be coupled to (or may be part of) a touch screen system (which would also include the display monitor) and may provide estimates of the finger's position to the touch screen system. As a finger is moved about on the display screen, successive estimates of the finger's position can be recorded in the touch screen system to provide an electronic record of the finger's movement and the estimated positions can be displayed on the display monitor. The touch screen system may include software or other components to calculate the path of movement of the finger between its successive estimated positions and to smooth the calculated path. Such a touch screen system, in combination withsystem 100, would effectively allow a user to write or draw on the display monitor, or to manipulate objects displayed on the display monitor, using the person's finger. - In a touch screen system, the
radiation sources 106 and radiation sensors 102 may be located relatively close to the display screen and the amount of radiation incident on the radiation sensors may vary as the information displayed on the display screen changes. In such embodiments, it may also be beneficial to update the baseline intensity level for some or all of the radiation sources. - Reference is next made to
FIGS. 5 a and 5 b.FIG. 5 a illustrates anothersystem 500 for estimating the position of aradiation blocking object 524.FIG. 5 b illustrates the bottom right corner ofsystem 500 in greater detail.System 500 is largely similar tosystem 100 and corresponding elements are identified with corresponding reference numerals.System 500 includes diffusers 530 mounted adjacent to the radiation sources 506. Diffusers 530 diffuse radiation emitted by the radiation sources, thereby smoothing the amount of radiation apparently emitted along the left, bottom and right sides of theframe 508 by the radiation sources, as viewed from the radiation sensor 502. In this embodiment, the angular position of theradiation blocking object 524 relative to the left and right sides of the frame and the radiation sensors is estimated as described above in relation tosystem 100. The inventors have found that diffusing the radiation emitted byradiation sources 506 can provide a more accurate estimate of the radiation blocking object's position. - Various materials are suitable for use as diffusers 530, including slightly clouded or translucent plastics or other materials that diffuse but do not excessively scatter radiation from the radiation sources such that it cannot accurately be measured by the radiation sensors 102. In some embodiments, optical grade diffusers which diffuse, but do not substantially block the radiation passing through the diffuser, may be used effectively, including diffraction gratings, lenticular diffusers and lenticular diffraction gratings may be used for the diffusers 530.
FIG. 5 b illustrates a continuouslenticular diffuser 530 b installed on thebottom side 512 offrame 508 and a continuouslenticular diffuser 530 r installed on theright side 516 offrame 508. -
FIG. 6 illustrates a portion of anotherembodiment 600, corresponding to the portion ofsystem 500 illustrated inFIG. 5 b. Insystem 600,individual diffusers 630 are installed adjacent eachradiation source 506. - In some embodiments of the invention, the controller may vary the intensity of radiation emitted by some or all of the radiation sources. This may be done to vary the measured intensity level for a radiation source at the radiation sensors, to overcome the effect of ambient light, to reduce power consumption by the system, or for other reasons.
- In the embodiments described above the frame is rectangular and the radiation sensors are mounted in two corners of the frame. In other embodiments, the frame may have a different shape. For example, the present invention may be used with a bulletin board or other object that has any regular or irregular shape and the frame may be shaped and sized to fit on or over the underlying object. Sensors may be positioned at various places on the frame, including along the sides (which may be straight or curved) of the frame. In each case, the position of each sensor and of the radiation sources visible from the sensor are used geometrically to identify the presence and position of a radiation blocking object.
- In some embodiments with rectangular or other frame shapes, additional sensors may be used. For example, additional sensors could be added at the bottom left and right corners of system 100 (
FIGS. 1) and 500 (FIG. 5 a). In some embodiments, additional radiation sources could be added along thetop side 110 of the frame. In some embodiments, additional information about the position of theradiation blocking object - In some embodiments, with rectangular or other frame shapes, sensors may be placed along the sides of the frame. The positioning of radiation sensor and radiation sources may depend on the portion of an underlying system (such as a whiteboard, display monitor or other system) in which a radiation blocking object is to be detected.
- In various embodiments, a system according to the present invention may include a bezel (which may be part of the frame) that conceals some or all of the components of the system including the radiation sources, the radiation sensors and diffusers. In some embodiments, the bezel or the frame or both may be painted with radiation absorbing paint or otherwise adapted to reduce the amount of radiation that is reflected toward the radiation sensors from the bezel or the frame or both.
- In some embodiments, an optical filter may be placed between some or all of the radiation sensors and some or all of the radiation sources. For example, an optical filter could be installed around the radiation sensors to reduce the amount of ambient and other undesirable radiation that is incident on the radiation sensors.
- Reference is next made to
FIG. 7 , which illustrates asystem 700 for simultaneously tracking the position of two or more radiation blocking objects.System 700 is a touchscreen that operates as both an input device and an output device for a connected computer or other external system. -
System 700 is similar in construction tosystems System 700 may be used as an electronic whiteboard system or an LCD touch screen. -
System 700 includes a pair ofradiation sensors controller 704, a plurality ofradiation sources 706 mounted on aframe 708 and an LCD display screen.Sources 706 are mounted on theleft side 714,bottom side 712 andright side 716 of theframe 708.Frame 708 also has atop side 710.Radiation sensor 702 a is mounted at the top left corner offrame 708 andradiation sensor 702 b is mounted at the top right corner of theframe 708.Radiation sensors Controller 704 is coupled to radiation sensors 702 andradiation sources 706.Controller 704 controls the radiation sources and receives radiation intensity levels from the radiation sensors as described above in relation tosystem 100. - The sides of
frame 708 are parallel to the axes of an x-y plane. A pair ofradiation blocking objects radiation sources 706 and the radiation sensors 702. - The LCD display screen is mounted within
frame 708 and has adisplay surface 728. The line of sight paths along which radiation from theradiation sources 706 to the radiation sensors 702 pass above the display surface, and are generally parallel to the display surface. The LCD display screen has a resolution of X horizontal pixels by Y vertical pixels. For example, in some embodiments the LCD display screen may have a resolution of 1280×1024 pixels or 1920×1080 pixels. Many other pixel resolutions are possible for various display panels. In various embodiments, any type of display panel may be used in place of an LCD panel. Typically,frame 708 will be mounted to the display panel, or will also form part of the housing of the display panel. -
System 700 may optionally include diffusers, such as thediffusers 530 and 630 illustrated inFIGS. 5 and 6 . -
System 700 will typically include several input/output interfaces. In the present embodiment,controller 704 is coupled to a computing device through aninterface 748 to transmit the position of radiation blocking objects to the computing device. For example,interface 748 may be a serial interface such as a USB interface or a parallel interface. The LCD display is coupled to the computing device to receive video signals, which are displayed on thedisplay 728, through a video signal interface (not shown). - Reference is next made to
FIG. 8 , which illustrates amethod 800 for identifying or estimating the positions ofradiation blocking objects method 800 is performed bycontroller 704. Prior to the start ofmethod 800, no radiation blocking object is positioned on thedisplay surface 728. -
Method 800 begins instep 802, in which a firstradiation blocking object 724 a is initially positioned on thedisplay surface 728. Instructions for performingmethod 800 are recorded inmemory 721.Controller 720 accesses the stored instructions and executes the instructions to perform the method. -
Method 800 will be explained by way of example and the for purposes of the example, the first radiation blocking object is initially placed on the display surface in the position shown inFIG. 7 . In this step,radiation blocking object 724 b is not placed on thedisplay surface 728. - Reference is made to
FIGS. 9 a and 9 b, which illustrate radiation intensity signals 722 a and 722 b afterradiation blocking object 724 a has been placed on thedisplay surface 728. - Radiation intensity signal 722 a illustrates that radiation intensity levels from
radiation sources 706 i-706 k are attenuated atradiation sensor 702 a. Radiation intensity signal 722 b illustrates that radiation intensity levels fromradiation source 706 a-406 c are attenuated atradiation sensor 702 b. -
Controller 704 usesradiation intensity signal system 100 to estimate the physical position P724a(xaa, yaa) ofradiation blocking object 724 a. Position P724a(xaa, yaa) is a physical (or analog) position calculated relative to positions of the sensors 702 and based on angles (θa, φa). -
Controller 704 maintains a touch table, in which the last known position of each radiation blocked object that has been detected on thesurface 728 is recorded. Typically, the touch table may be a set of variables or part of a database that is stored inmemory 721. In the present embodiment, the touch table includes two slots, A and B, for recording the last known positions of up to two radiation blocking objects. In other embodiments, the touch table may include more than two slots, or may include a variable number of slots. -
Controller 704 records the physical position P724a of the firstradiation blocking object 724 a in slot A in the touch table: -
Slot X Position Y Position A xaa yaa B — — - Physical position P724a(xaa, yaa) corresponds to a pixel (or digital) position P724d(xad, Yad) on the
LCD display 728.Controller 704 converts the physical position P724a to the corresponding pixel position P724d, and provides the pixel position P724d atinterface 748. -
Method 800 then proceeds to step 804. Instep 804,Controller 704 operatesradiation sources 706 and sensors 702 to sequentially obtain radiation intensity levels associated withradiation sources 706 from each radiation sensor 702. The radiation intensity levels from each radiation sensor are combined into a radiation intensity signal 722.Controller 704 analyzes each radiation intensity signal 722 to determine the number of radiation blocking objects that are represented in each of the radiation intensity signals. - In this embodiment, up to two radiation blocking objects may be placed on
surface 728. - Reference is made to
FIGS. 10 a and 10 b, which illustrate example radiation intensity signals 722 a and 722 b when tworadiation blocking objects surface 728. Each of the radiation intensity signals 722 a and 722 b has two distinct ranges of radiation intensity levels that are attenuated at each of the radiation source 702. (A radiation source for which the radiation intensity level is attenuated may be referred to as an attenuated radiation source.) Each range of attenuated radiation intensity levels corresponds to a separate radiation blocking object 724. The ranges of attenuated radiation intensity levels are separated by at least one radiation source that is not attenuated. For example, and referring also toFIG. 7 , inradiation intensity signal 722 a, radiation intensity levels forradiation sources 706 i-706 k and 706 p-706 r are attenuated atradiation sensor 702 a. The attenuation ofradiation sources 706 i-706 k corresponds toradiation blocking object 724 a. The attenuation ofradiation sources 706 p-706 r corresponds toradiation blocking object 724 b.Controller 704 is configured to identify the two distinct ranges of attenuated radiation sources by identifying at least one radiation source between the ranges that is not attenuated. In some situations, a range of attenuated radiation sources may consist of a single attenuated radiation source. - Reference is made to
FIGS. 11 , 12 a and 12 b, which illustrate another condition in which two radiation blocks have been placed onsurface 728. InFIG. 11 ,radiation blocking objects -
FIG. 12 a is aradiation intensity signal 722 a which illustrates that theradiation blocking objects Radiation blocking object 724 a appears to attenuate radiation fromradiation sources 706 i-706 t.Radiation blocking object 724 b appears to attenuate radiation from radiation sources 706 l-706 o.Controller 704 is configured to distinguish the two ranges of attenuated radiation signals by identifying two distinct minima in the radiation intensity signal, separated by at least one radiation intensity value that is higher than either of the minima. For example, inFIG. 12 a, radiation intensity levels forradiation sources controller 704 may be configured to identify two distinct ranges in various ways. In some cases, a range of attenuation radiation intensity levels may have only a single attenuated radiation source. For example, in some embodiments, thecontroller 104 may be configured to identify at least one radiation intensity level between local minima radiation intensity levels that exceed the minima by some predetermined about or ratio. In some embodiments, the controller may be configured to require at least two (or a high number) of radiation intensity values between local minima. -
FIG. 12 b illustrates aradiation intensity signal 722 b corresponding to the positions ofradiation blocking object FIG. 11 . Radiation intensity signal 722 b includes two distinct regions of the attenuated radiation intensity levels atradiation sources 706 a-706 c and 706 g to 706 i. The two ranges are separated by one or more radiation intensity levels that are not attenuated.Controller 704 is configured to distinguish the two ranges of attenuated radiation intensity levels as described above in relation toFIGS. 10 a and 10 b. -
Controller 704 is thus configured to identify to ranges of attenuated radiation sources in each of the radiation intensity signals illustrated inFIGS. 10 a, 10 b, 12 a and 12 b. - Reference is next made to
FIGS. 13 , 14 a and 14 b, which illustrate another condition in which tworadiation blocking objects surface 728. - In
FIG. 13 , the tworadiation blocking objects radiation sensor 702 a. Radiation emitted byradiation source 706 j, which is also generally collinear with the radiation blocking objects, is at least partially blocked byradiation blocking object 724 b from reachingradiation sensor 702 a.Radiation blocking object 724 a may block additional radiation fromradiation source 706 j from reachingradiation source 702 a, butradiation blocking object 724 a is at least partially in the shadow ofradiation blocking object 724 b. -
FIG. 14 a illustrates aradiation intensity signal 722 a corresponding to the positions of theradiation blocking object FIG. 13 . The radiation intensity levels forradiation sources 706 i-706 k are attenuated byradiation blocking objects surface 728.Controller 704 analyzesradiation intensity signal 722 a and is able to identify only one apparent radiation blocking object. -
FIG. 14 b illustrates aradiation intensity signal 722 b corresponding to the positions ofradiation blocking object FIG. 13 . Radiation intensity signal 722 b includes two distinct regions of the attenuated radiation intensity levels atradiation sources 706 a-706 c and 706 d to 706 f. The two ranges are separated by one or more radiation intensity levels that are not attenuated.Controller 704 is configured to distinguish the two ranges of attenuated radiation intensity levels as described above. -
Controller 704 thus determines whether each of radiation intensity signals 722 a and 722 b obtained in thisstep 804 appears to contain zero, one or two ranges of attenuated radiation sources. -
Method 800 continues fromstep 804 depending on the number of radiation blocking objects identified in the radiation intensity signals as follows: -
- if each of the radiation intensity signals 722 contains one range of attenuated radiation sources (as illustrated in
FIGS. 9 a and 9 b), thenmethod 800 proceeds to step 806; - if both of the radiation intensity signals 722 contains two ranges of attenuated radiation sources (as illustrated in
FIGS. 10 a and 10 b and inFIGS. 12 a and 12 b), thenmethod 800 proceeds to step 808; - if either one of the radiation intensity signals 722 contains two ranges of attenuated radiation sources and the other radiation intensity signal contains one range of attenuated radiation sources (as illustrated in
FIGS. 14 a and 14 b), thenmethod 800 proceeds to step 810; and - if both of the radiation intensity signals 722 contains zero ranges of attenuated radiation sources,
method 800 proceeds to step 820; and - otherwise,
method 800 returns to step 804;
- if each of the radiation intensity signals 722 contains one range of attenuated radiation sources (as illustrated in
- In
step 806,controller 704 determines the position of a radiation blocking object 724 on thedisplay surface 728.Controller 704 calculates an angle θ and an angle φ corresponding to the weighted average attenuation in the respective ranges of attenuated intensity levels in each of the radiation intensity signals 722 a and 722 b. A radiation blocking object 724 is deemed to be located at the intersection point of a pair of lines 746 and 732 corresponding to the angles θ and φ and the positions of theradiation sensors - If only one position corresponding to one radiation blocking object is recorded in the touch table, the intersection point is deemed to be the new physical position of the radiation blocking object. The new position is recorded in the touch table in place of the previously recorded position. The controller converts the physical position of the radiation blocking object into a corresponding pixel position, which is then provided at the
interface 748. - If two positions corresponding to two radiation blocking objects are recorded in the touch table, the controller determines which of the previously recorded positions is closest to the intersection point. The intersection point is deemed to be the new position of the radiation blocking object corresponding to the closest previously recorded position, which is replaced in the touch table with the position of the intersection point. The controller converts the physical position of the radiation blocking object into a corresponding pixel position, which is then provided at the
interface 748. - The further previously recorded position is deleted from the touch table.
-
Method 800 then returns to step 804. - Reference is additionally made to
FIGS. 7 , 10 a and 10 b. - In
step 808,controller 704 determines various points at which the radiation blocking objects 724 may be positioned based on the two ranges of attenuated radiation sources identified in each of the radiation intensity signals 722 a and 722 b instep 804. - For example, In
radiation intensity signal 722 a,radiation sources 706 i-406 k and 706 p-406 r are attenuated atradiation sensor 702 a. The two ranges of attenuated radiation sources are separated by at least one radiation source that is not attenuated. -
Controller 704 analyzes each group of attenuated sensors independently and calculates an angle θa based on a weighted averaging of the attenuation ofsources 706 i-706 k, as described in relation to angle θ124 above. Angle θa defines aline 746 a that extends through the position ofradiation sensor 702 a. -
Controller 704 also calculates an angle θb based on the attenuation ofsources 706 p-706 r. Angle θb defines aline 746 b that extends through the position ofsensor 702 a. - In
radiation intensity signal 722 b,radiation sources 706 a-706 c and 706 g-706 i are attenuated atradiation sensor 702 b.Controller 704 calculates an angle φa based on the attenuation ofsources 706 a-706 c and an angle φb based on the attenuation ofsource 706 g-706 i. Angle φa defines aline 732 a that passes through the position ofsensor 702 b. Angle φb defines aline 732 b that passes through the position ofsensor 702 b. -
Line 746 a intersects withlines points Line 746 b intersects withline -
Line 732aLine 732b Line 746a 734 736 Line 746b738 740 - The four points 734-740 may be considered in two pairs. The radiation blocking objects 724 a and 724 b may be either at
points points -
Method 800 then proceeds todecision step 812. - In
step 810,controller 704 identifies various points at which theradiation blocking objects - Reference is additionally to made to
FIGS. 13 , 14 a and 14 b. - For the radiation intensity signal 722 having two attenuated ranges of radiation sources, each range is analyzed separately to determine two angles θa and θb or φa and φb, as described in relation to step 808. For example,
radiation intensity signal 722 b inFIG. 14 b has two distinct ranges of attenuated radiation sources and the two angles φa and φb illustrated inFIG. 13 are calculated as described above. Two corresponding lines extending from the corresponding radiation sensor 702 are also calculated. In this example,lines - For the radiation intensity signal having only one range of
attenuated radiation sources 706, only one corresponding angle θ or φ can be calculated. In this example,radiation intensity signal 722 a (FIG. 14 a) has only one range ofattenuated radiation sources 706 i-706 k. A corresponding angle θa andline 746 a are calculated. - Angle θa is duplicated as angle θb, and
line 746 a is duplicated asline 746 b. -
Controller 704 then calculates points 734-740 based on the intersections oflines lines step 808. -
Method 800 then proceeds to step 812. - In
step 812,controller 704 determines the number of position recorded in the touch table. If only one position is recorded in the touch table, thenmethod 800 proceeds to step 812. If two positions are recorded in the touch table, thenmethod 800 proceeds to step 814. - Step 814 is performed if the position of one radiation blocking is recorded in the touch table, and one additional radiation blocking object is newly identified, based on at least one of the radiation intensity signals 722 a or 722 b or both having two ranges of attenuated radiation sources.
-
Controller 704 determines which points 734 and 740 or 736 and 738 correspond to the tworadiation blocking objects -
Controller 704 determines which point 734-440 is closest to the position recorded in the touch table. In this example, the physical position P1 a ofradiation blocking object 724 a was recorded in slot A of the touch table instep 806. The closest point (among points 734-740) to the previously known position P1 a is deemed to be the current position P1 a of the firstradiation blocking object 724 a. Position P1 a will correspond to one point in one of the pairs of points (734 and 740 or 736 and 738). The other point in the same pair is deemed to be the position P2 a(xba, yba) of the secondradiation blocking object 724 b. For example, in the example illustrated inFIG. 7 , the last known position P1 a forradiation blocking object 724 a is closest to position 734.Radiation blocking object 724 a is deemed to be positioned atpoint 734, and the position P2 a of the secondradiation blocking object 724 b is deemed to bepoint 740. -
Controller 704 updates the touch table with the position P1 a of the firstradiation blocking object 724 a in slot A of the touch table and records the position P2 a of the secondradiation blocking object 724 b in slot B of the touch table: -
Slot X Position Y Position A xaa yaa B xba yba -
Controller 704 converts the physical positions P1 a and P1 a of theradiation blocking objects interface 748 to a coupled computing device. -
Method 800 then returns to step 804. - In
step 816, the positions of the first and second radiation blocking object 724 are tracked as they are moved on thedisplay surface 728. -
Method 800 reaches step 816 when the touch table has previously been updated with the positions of two radiation blocking object 724 (in either step 814 or 816). The positions of the two radiation blocking objects is updated in the touch table and their respective positions are reported atinterface 748. -
Controller 704 analyzes each possible combination of movements from the last recorded positions P1 a and P2 a in the touch table. In this embodiment, the four possible combinations are as follows: - Combination 1:
Radiation blocking object 724 a moved toposition 734; and -
-
Radiation blocking object 724 b moved toposition 740.
-
- Combination 2:
Radiation blocking object 724 a moved toposition 740; and -
-
Radiation blocking object 724 b moved toposition 734.
-
- Combination 3:
Radiation blocking object 724 a moved toposition 736; and -
-
Radiation blocking object 724 b moved toposition 738.
-
- Combination 4:
Radiation blocking object 724 a moved toposition 738; and -
-
Radiation blocking object 724 b moved toposition 736.
For each combination,controller 704 is configured to calculate the total distance that the two radiation blocking objects 724 would move. For example, for combination 3, the firstradiation blocking object 724 a would move from position P1 a to position 736 and the secondradiation blocking object 724 b would move from position P2 a toposition 738. The distance that each radiation blocking object may be calculated using standard geometric techniques.
-
- For each combination, the distances that each radiation blocking object would move are summed together. In this example, each combination results in the following total distances:
- Combination 1: 0.2 mm
- Combination 2: 82.4 mm
- Combination 3: 46.5 mm
- Combination 4: 85.3 mm
-
Controller 704 is configured to deem the radiation blocking objects to have moved in accordance with the combination that requires the shortest total movement of the two radiation blocking objects. In the present example, this is combination 1.Radiation blocking object 724 a is deemed to have moved topoint 734.Radiation blocking object 724 b is deemed to have moved topoint 740.Controller 704 updates the touch table with the new position of each radiation blocking object.Controller 704 converts the new physical positions P1 a and P2 a of theradiation blocking objects interface 748 to a coupled computing device. -
Method 800 then returns to step 804. -
Method 800 reaches step 820 if both radiation blocking objects have been removed from thedisplay surface 728. The controller deletes all recorded positions in the touch table and may optionally provide an indication atinterface 748 that no radiation blocking objects have been detected on thedisplay surface 728. - Using
method 800,controller 704 provides successive positions of one or two radiation blocking objects as they are positioned on thedisplay surface 728 and moved about thedisplay surface 728. The method terminates when no radiation blocking object is identified on the display surface. - In
system 700 andmethod 800, the positions of radiation blocking objects are recorded in the touch table as physical positions and the distances between various points are calculated in physical dimensions. In other embodiments, the positions may be recorded and distances may be calculated in pixel dimensions. - The present invention has been described here by way of example only. Various modification and variations may be made to these exemplary embodiments without departing from the spirit and scope of the invention.
Claims (23)
1. A system for sensing the position of a radiation blocking object, the system comprising:
a frame;
a first radiation sensor mounted to the frame;
a second radiation sensor mounted to the frame, wherein the first and second radiation sensors are spaced by a distance;
a plurality of radiation sources mounted to the frame, wherein at least some of the radiation sources are visible to each of the radiation sensors;
a controller coupled to radiation sources and the radiation sensors.
2. The system of claim 1 wherein each of the radiation sensors is sensitive to radiation emitted by the radiation sources and provides a radiation intensity level to the controller corresponding to the intensity of radiation incident on the sensor.
3. The system of claim 1 wherein each of the radiation sensors is selected from the group consisting of:
a photosensor;
a photodiode;
a photocell,
a solar cell; and
a photovoltaic cell.
4. The system of claim 1 wherein the frame at least partially surrounds a surface.
5. The system of claim 1 wherein the surface is selected from the group consisting of: a writing surface; and the surface of a display screen.
6. (canceled)
7. The system of claim 1 further including a bezel and wherein the radiation sources and radiation sensors are mounted within the bezel.
8. (canceled)
9. The system of claim 1 further including one or more diffusers for diffusing radiation emitted by at least some of the radiation sources.
10. The system of claim 9 wherein the diffusers are selected from the group consisting of:
translucent sheet material;
translucent plastic;
translucent glass;
lenticular diffusers;
diffraction gratings; and
lenticular diffraction gratings.
11. The system of claim 1 wherein:
the frame has first, second, third and fourth sides;
the first radiation sensor is mounted between the first and second sides;
the second radiation sensor is mounted between the first and fourth sides;
radiation sources are mounted on second, third and fourth sides.
12. The system of claim 1 further including an interface coupled to the controller for providing a position of the radiation blocking object to an external device.
13. A method of estimating the position of a radiation blocking object on a surface, the method comprising:
providing a first sensor and a second sensor;
providing a plurality of radiation sources, wherein:
radiation emitted by at least some of the radiation sources passes across the surface and is incident on the first sensor; and
radiation emitted by at least some of the radiation sources passes across the surface and is incident on the second sensor;
assembling a first radiation intensity signal corresponding to the first radiation sensor;
assembling a second radiation intensity signal corresponding to the second radiation sensor; and
estimating the position of the radiation blocking object based on the radiation intensity signals.
14. The method of claim 13 wherein each radiation intensity signal corresponding to a radiation sensor is assembled by sequentially sampling a radiation intensity level from the radiation sensor while at least some of the radiation sources are sequentially activated.
15. The method of claim 14 wherein the radiation intensity signals are assembled contemporaneously.
16. The method of claim 15 wherein at least one of the radiation sources is activated separately at different intensities to generate a radiation intensity signal corresponding to a first radiation sensor and a radiation intensity signal corresponding to the second radiation sensor.
17. The method of claim 14 wherein the radiation intensity signals are assembled sequentially.
18. The method of claim 17 wherein a first radiation intensity signal corresponding to the first radiation sensor is assembled and then a second radiation intensity signal corresponding to the second radiation sensor.
19. The method of claim 13 wherein estimating the position of the radiation blocking object includes:
identifying a first group of one or more attenuated radiation sources in the first radiation intensity signal;
identifying a second group of one or more attenuated radiation sources in the second radiation intensity signal;
estimating the position of the radiation blocking object based on the position of the first group of attenuated radiation sources relative to first radiation sensor and the position of the second group of attenuated radiation sources relative to the second radiation sensor.
20. The method of claim 19 wherein:
identifying a first group of one or more attenuated radiation sources includes, for at least some of the radiation sources, comparing a radiation intensity level in the radiation intensity signal to a baseline level for the radiation source at the first radiation sensor; and
identifying a second group of one or more attenuated radiation sources includes, for at least some of the radiation sources, comparing a radiation intensity level in the radiation intensity signal to a baseline level for the radiation source at the second radiation sensor.
21. The method of claim 20 wherein:
a radiation source is only included in the first group if the radiation intensity level for the radiation source is below the baseline level for the radiation source at the first radiation sensor by a threshold; and
a radiation source is only included in the second group if the radiation intensity level for the radiation source is below the baseline level for the radiation source at the second radiation sensor by a threshold.
22. The method of claim 19 wherein the estimating the position of the radiation blocking object includes:
identifying a first center radiation source based on the first group;
identifying a second center radiation source based on the second group; and
estimating the position of the radiation blocking object based on the first center radiation source, the second center radiation source.
23.-35. (canceled)
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JP2015195058A (en) | 2015-11-05 |
CN102597813B (en) | 2017-11-14 |
US10627973B2 (en) | 2020-04-21 |
EP2443481A1 (en) | 2012-04-25 |
KR20170103987A (en) | 2017-09-13 |
KR101814515B1 (en) | 2018-01-04 |
CA2763173A1 (en) | 2010-12-23 |
JP2012530303A (en) | 2012-11-29 |
WO2010145038A1 (en) | 2010-12-23 |
CN102597813A (en) | 2012-07-18 |
US20180164926A1 (en) | 2018-06-14 |
EP2443481B1 (en) | 2021-05-19 |
KR20120037945A (en) | 2012-04-20 |
JP6086952B2 (en) | 2017-03-01 |
EP2443481A4 (en) | 2017-11-01 |
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