U.S. patent application number 14/636127 was filed with the patent office on 2016-02-04 for two-dimensional position sensing systems and sensors therefor.
The applicant listed for this patent is Baanto International Ltd.. Invention is credited to Jonathan Clarke, Stephen McFadyen, Avanindra Utukuri.
Application Number | 20160034107 14/636127 |
Document ID | / |
Family ID | 43355633 |
Filed Date | 2016-02-04 |
United States Patent
Application |
20160034107 |
Kind Code |
A1 |
Utukuri; Avanindra ; et
al. |
February 4, 2016 |
Two-Dimensional Position Sensing Systems and Sensors Therefor
Abstract
Two dimensional position sensing system and sensors for use in
such systems are disclosed. The sensors incorporate linear array
sensors having sensor elements and an aperture plate. Some
embodiments include a radiation source that directs radiation onto
some of the sensor elements. Other embodiments including radiation
blocking objects that block radiation from reaching some of sensor
elements. The direction or position of the radiation source or
radiation blocking object may be estimated from the radiation
incident on the sensor elements.
Inventors: |
Utukuri; Avanindra;
(Mississauga, CA) ; Clarke; Jonathan; (Toronto,
CA) ; McFadyen; Stephen; (Toronto, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Baanto International Ltd. |
Mississauga |
|
CA |
|
|
Family ID: |
43355633 |
Appl. No.: |
14/636127 |
Filed: |
March 2, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13329192 |
Dec 16, 2011 |
8969769 |
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14636127 |
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PCT/CA2010/000883 |
Jun 16, 2010 |
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13329192 |
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61187651 |
Jun 16, 2009 |
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Current U.S.
Class: |
345/175 |
Current CPC
Class: |
G06F 3/0418 20130101;
G01S 5/16 20130101; G06F 3/0428 20130101; G01D 5/34 20130101; G06F
3/03542 20130101; G01S 3/784 20130101; G06F 3/0421 20130101 |
International
Class: |
G06F 3/042 20060101
G06F003/042; G06F 3/041 20060101 G06F003/041 |
Claims
1. A method of estimating the direction of a radiation source
positioned in a sensing region, the method comprising: providing a
radiation sensor, the radiation sensor comprising: a linear array
sensor having a plurality of sensor elements, the sensor elements
facing the sensing region; an aperture plate positioned between the
linear array sensor and the sensing region to block radiation from
the sensing region from reach the linear array sensor; and an
aperture formed in the aperture plate to allow radiation from the
radiation source to reach some of the sensor elements; receiving an
intensity signal from the linear array sensor, wherein the
intensity signal includes intensity values corresponding to
radiation incident on the sensor elements through the aperture; and
determining the direction based on the intensity signal.
2. The method of claim 1 wherein the radiation intensity signal
includes at least one high intensity value exceeding a threshold
value, and wherein the direction is determined based on the at
least one high intensity value.
3. The method of claim 1 wherein the radiation intensity signal
includes a range of high intensity values exceeding a threshold
value, and wherein determining the direction includes: selecting a
center sensor element based on the range of high intensity values;
and determining a direction based on the center sensor element.
4. The method of claim 1 wherein the radiation intensity signal
includes at least one low intensity value below a threshold value,
and wherein the direction is determined based on the at least one
low intensity value.
5. The method of claim 1 wherein the radiation intensity signal
includes a range of low intensity values below a threshold value,
and wherein determining the direction includes: selecting a center
sensor element based on the range of low intensity values; and
determining a direction based on the center sensor element.
6. The method of claim 1 wherein the radiation intensity signal is
an analog signal and wherein determining the direction includes:
converting the analog radiation intensity signal into a
corresponding final radiation intensity; and determining a
direction based on the final radiation intensity signal.
7. The method of claim 6 wherein the radiation intensity signal is
a digital signal having either a high value or a low value
corresponding to each of the sensor elements and wherein
determining the direction includes: selecting a center sensor
element based on a range of high intensity values; and determining
a direction based on the center sensor element.
8. The method of claim 6 wherein the radiation intensity signal is
a digital signal having either a high value or a low value
corresponding to each of the sensor elements and wherein
determining the direction includes: selecting a center sensor
element based on a range of low intensity values; and determining a
direction based on the center sensor element.
9. The method of claim 1 including filtering the radiation
intensity signal to remove spurious values before determining the
direction.
10. The method of claim 1 wherein determining the direction
includes looking up an angle in a lookup table.
11. The method of claim 1 wherein determining the direction
includes calculating an angle.
12. A method of estimating the position of a radiation source
relative to a sensing region, the method comprising: positioning a
first position sensor in a first position relative to the sensing
region; positioning a second position sensor in a second position
relative to the plane, wherein the first and second position
sensors are separated by a distance; determining a first ray
relative to first position sensor; determining a second ray
relative to the second position sensor; and estimating the position
of the radiation source to be at the intersection of the first and
second rays.
13. The method of claim 12 wherein the sensing region is a surface
of a display screen.
14. The method of claim 12 wherein the sensing region is a surface
of a writing surface.
15. The method of claim 12 wherein the radiation source is an
active radiation source that emits radiation detectable by the
first and second position sensors.
16. The method of claim 12 wherein the radiation source is a
passive reflective radiation and further including providing one or
more active radiation sources in a fixed position, and wherein the
passive radiation source reflects radiation from the active
radiation sources onto the first and second position sensors.
17. The method of claim 12 wherein the sensing region is a surface
of a display screen.
18. The method of claim 12 wherein the sensing region is a surface
of a writing surface.
19. A method of estimating the position of a radiation source
relative to a sensing region, the method comprising: providing a
plurality of active radiation sources adjacent the sensing region;
positioning a first position sensor in a first position relative to
the sensing region wherein radiation emitted by at least some of
the radiation sources is incident upon the first radiation sensor;
positioning a second position sensor in a second position relative
to the plane wherein radiation emitted by at least some of the
radiation sources is incident upon the second radiation sensor, and
wherein the first and second position sensors are separated by a
distance; determining a first ray relative to first position
sensor; determining a second ray relative to the second position
sensor; and estimating the position of the radiation source to be
at the intersection of the first and second rays.
20. The method of claim 19 wherein radiation from a first group of
active radiation sources is blocked from reaching the first
position sensor and radiation from a second group of radiation
sources is blocked from reaching the second radiation sensor and
wherein the first ray corresponds to the first group and the second
ray corresponds to the second group.
21.-26. (canceled)
Description
FIELD
[0001] The described embodiments relate to systems and methods for
sensing the position of a radiation source or a radiation blocking
object in two dimensions. The embodiments also relate to sensors
for use in such systems and methods.
SUMMARY
[0002] Some embodiments of the invention provide sensors for
estimating the direction of an object relative to the sensor. A
radiation source emits generated or reflected radiation towards a
sensor. The sensor has a linear optical sensor array behind an
aperture plate. The sensor array has a plurality of sensor elements
arranged linearly. The aperture plate has an aperture to allow
radiation from the radiation source to reach only some of the
sensor elements when the system is in use. An intensity signal from
the sensor is coupled to a processor which is configured to
identify sensor elements upon which the radiation is incident. A
center sensor element is chosen from among the illuminated sensor
elements and is used to estimate the direction of the radiation
source relative to the sensor.
[0003] Other embodiments provide a sensor that has a linear array
sensor. A plurality of radiation sources is provided to illuminate
a range of sensor elements in a linear array sensor. The radiation
from each radiation source passes through an aperture in an
aperture plate and illuminates only some of the sensor elements. A
radiation blocking element is used to block radiation from some of
the radiation sources from reaching some of the sensor elements.
The absence of radiation reaching the sensor elements is measured
and is used to estimate the direction of the radiation blocking
element relative to the sensor.
[0004] In another aspect, a pair of sensors is provided. The
sensors are positioned in a known spacing relative to one another.
Each sensor determines the direction of a radiation source (in some
embodiments) or a radiation blocking object (in other embodiments)
relative to the sensor. The position of the radiation source or
radiation blocking object is estimated based on the direction of
the source or object from each sensor and the known relative
positioning of the sensors.
[0005] Another aspect provides a method of estimating the direction
of a radiation source positioned in a sensing region, the method
comprising: providing a radiation sensor, the radiation sensor
comprising: a linear array sensor having a plurality of sensor
elements, the sensor elements facing the sensing region; an
aperture plate positioned between the linear array sensor and the
sensing region to block radiation from the sensing region from
reach the linear array sensor; and an aperture formed in the
aperture plate to allow radiation from the radiation source to
reach some of the sensor elements; receiving an intensity signal
from the linear array sensor, wherein the intensity signal includes
intensity values corresponding to radiation incident on the sensor
elements through the aperture; and determining the direction based
on the intensity signal.
[0006] In some embodiments, the radiation intensity signal includes
at least one high intensity value exceeding a threshold value, and
wherein the direction is determined based on the at least one high
intensity value.
[0007] In some embodiments, the radiation intensity signal includes
a range of high intensity values exceeding a threshold value, and
wherein determining the direction includes: selecting a center
sensor element based on the range of high intensity values; and
determining a direction based on the center sensor element.
[0008] In some embodiments, the radiation intensity signal includes
at least one low intensity value below a threshold value, and
wherein the direction is determined based on the at least one low
intensity value.
[0009] In some embodiments, the radiation intensity signal includes
a range of low intensity values below a threshold value, and
wherein determining the direction includes: selecting a center
sensor element based on the range of low intensity values; and
determining a direction based on the center sensor element.
[0010] In some embodiments, the radiation intensity signal is an
analog signal and wherein determining the direction includes:
converting the analog radiation intensity signal into a
corresponding final radiation intensity; and determining a
direction based on the final radiation intensity signal.
[0011] In some embodiments, the radiation intensity signal is a
digital signal having either a high value or a low value
corresponding to each of the sensor elements and wherein
determining the direction includes: selecting a center sensor
element based on a range of high intensity values; and determining
a direction based on the center sensor element.
[0012] In some embodiments, the radiation intensity signal is a
digital signal having either a high value or a low value
corresponding to each of the sensor elements and wherein
determining the direction includes: selecting a center sensor
element based on a range of low intensity values; and determining a
direction based on the center sensor element.
[0013] In some embodiments, the radiation intensity signal may be
filtered to remove spurious values before determining the
direction.
[0014] In some embodiments, determining the direction includes
looking up an angle in a lookup table.
[0015] In some embodiments, determining the direction includes
calculating an angle.
[0016] Another aspect provides a method of estimating the position
of a radiation source relative to a sensing region, the method
comprising: positioning a first position sensor in a first position
relative to the sensing region; positioning a second position
sensor in a second position relative to the plane, wherein the
first and second position sensors are separated by a distance;
determining a first ray relative to first position sensor;
determining a second ray relative to the second position sensor;
and estimating the position of the radiation source to be at the
intersection of the first and second rays.
[0017] In some embodiments, the sensing region is a surface of a
display screen.
[0018] In some embodiments, the sensing region is a surface of a
writing surface.
[0019] In some embodiments, the radiation source is an active
radiation source that emits radiation detectable by the first and
second position sensors.
[0020] In some embodiments, the radiation source is a passive
reflective radiation and further including providing one or more
active radiation sources in a fixed position, and wherein the
passive radiation source reflects radiation from the active
radiation sources onto the first and second position sensors.
[0021] In some embodiments, the sensing region is a surface of a
display screen.
[0022] In some embodiments, the sensing region is a surface of a
writing surface.
[0023] Another aspect provides a method of estimating the position
of a radiation source relative to a sensing region, the method
comprising: providing a plurality of active radiation sources
adjacent the sensing region; positioning a first position sensor in
a first position relative to the sensing region wherein radiation
emitted by at least some of the radiation sources is incident upon
the first radiation sensor; positioning a second position sensor in
a second position relative to the plane wherein radiation emitted
by at least some of the radiation sources is incident upon the
second radiation sensor, and wherein the first and second position
sensors are separated by a distance; determining a first ray
relative to first position sensor; determining a second ray
relative to the second position sensor; and estimating the position
of the radiation source to be at the intersection of the first and
second rays.
[0024] In some embodiments, the radiation from a first group of
active radiation sources is blocked from reaching the first
position sensor and radiation from a second group of radiation
sources is blocked from reaching the second radiation sensor and
wherein the first ray corresponds to the first group and the second
ray corresponds to the second group.
[0025] Another aspect provides a position sensor comprising: a
linear array sensor having a plurality of sensor elements arranged
linearly, the sensor elements facing a sensing region; an aperture
plate positioned between the linear array sensor and the sensing
region to block radiation from the sensing region from reaching the
linear array sensor; and an aperture formed in the aperture plate
to allow radiation from the sensing region to reach some of the
sensor elements.
[0026] In some embodiments, the sensor includes a processor coupled
to the linear array sensor to receive a radiation intensity signal
from the linear array sensor, wherein the radiation intensity
signal corresponds to the intensity of radiation incident on a
range of sensor elements through the aperture.
[0027] In some embodiments, the sensor includes an optical filter
to filter radiation reaching the sensor elements.
[0028] In some embodiments, the sensor elements are sensitive to
radiation emitted by a radiation source in the sensing region and
wherein the optical filter is selected to allow radiation emitted
by the radiation source to reach the sensor elements.
[0029] In some embodiments, the sensing region is generally planar
and wherein the sensor elements are linearly arranged generally
parallel to the sensing region.
[0030] In some embodiments, the processor is configured to estimate
a direction relative to the position sensor in response to the
radiation intensity signal.
[0031] These and other aspects of the invention are described below
in a description of the some example embodiments of the
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] Various embodiments of the invention will now be described
with reference to the drawings, in which:
[0033] FIG. 1 illustrates a sensor according to the present
invention;
[0034] FIG. 2 is a partial cut-away front view of the sensor of
FIG. 1;
[0035] FIG. 3 is a cross-sectional top-view of the sensor of FIG.
1;
[0036] FIG. 4 illustrates an intensity signal from the sensor of
FIG. 1;
[0037] FIGS. 5 and 6 illustrate other example intensity
signals;
[0038] FIG. 7 illustrates a final intensity signal based on the
signal of FIG. 4;
[0039] FIG. 8 illustrates a system for estimating the position of a
radiation source;
[0040] FIG. 9 illustrates a first whiteboard system according to
the present invention;
[0041] FIG. 10 illustrates a radiation source for use with the
whiteboard system of FIG. 9;
[0042] FIG. 11 illustrates a second whiteboard system according to
the present invention;
[0043] FIG. 12 illustrates a reflective radiation source for use
with the present invention;
[0044] FIG. 13 illustrates a third whiteboard system according to
the present invention;
[0045] FIG. 14 illustrates an intensity signal from a sensor of the
whiteboard system of FIG. 13;
[0046] FIG. 15 illustrates a final intensity signal based on the
signal of FIG. 14; and
[0047] FIG. 16 illustrates intensity signals in another embodiment
of the present invention.
[0048] The drawings are illustrative only and are not drawn to
scale.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0049] Exemplary embodiments described herein provide details
relating to optical sensor systems and methods for determining the
position of a radiation source or radiation blocking object. Other
exemplary embodiments describe details of whiteboard systems for
tracking the movement of a pen or other object on a whiteboard
surface. The radiating source may radiate radiation generated by
the radiation source or may reflect radiation from other sources.
The radiation may be in the visible light spectrum or in other
radiation spectrums, such as the ultraviolet or infrared spectrums.
The embodiments described herein are exemplary only and other
implementations and configurations of optical sensors are also
possible.
[0050] Reference is first made to FIGS. 1, 2 and 3, which
illustrate a position sensor 100 and a radiation source 110.
Radiation source 110 emits radiation 112 that is incident on the
sensor 100. A radiation source is described herein as emitting
radiation regardless of whether the radiation source simply
reflects radiation produced by another radiation source or the
radiation source generates radiation which then propagates away
from the radiation source. In some embodiments, radiation source
110 may be a passive source which reflects radiation initially
produce by another radiation source. For example, radiation source
may be a reflective source that simply reflects radiation towards
sensor 100. In some embodiments, radiation source 110 may be an
active radiation source such as a LED, a light bulb or other
source.
[0051] Sensor 100 includes a linear sensor array 114, an aperture
plate 118 and a processor 120. Linear sensor array 114 is mounted
on a sensor support 128, which is in turn mounted on a base plate
126. The aperture plate 118 is also mounted on base plate 126.
[0052] Sensor array 114 has a plurality of sensor elements 116 that
are arranged linearly. Each of the sensor elements 116 is sensitive
to radiation emitted by radiation source 110. For example, sensor
array 114 may be a linear CMOS sensor that is sensitive to visible
or infra-red radiation emitted by radiation source 110. Sensor
array 114 is coupled to processor 120. Sensor array 114 provides a
intensity signal 122 to the processor 120.
[0053] Aperture plate 118 has an aperture 124 formed in it such
that radiation emitted by radiation source 110 is incident on only
some of the sensor elements 116. In this embodiment, aperture 124
is a slit, allowing the radiation source 110 to be moved in the z
dimension and still emit radiation onto sensor 100 through aperture
124. In other embodiments, the aperture may be a hole or may have
another shape. In some embodiments, the shape (including the size)
of the aperture may be selected based on the sensitivity, shape and
spacing of the sensor elements 116.
[0054] The sensing region 111 is the range of space in which a
radiation source 110 can emit radiation that will be incident on a
sensing element 116 through the aperture 124. The sensor elements
116 are arranged generally parallel to the plane of the sensing
region 111. As radiation source 110 moves in the x or y dimensions
relative to sensor 100, radiation emitted by the radiation source
110 passes through aperture 124 and is incident on different sensor
elements 116.
[0055] In some embodiments, an optical filter may be used to limit
the frequency band of radiation incident on the sensor array 114.
Referring to FIGS. 2 and 3, an optical filter may be positioned in
front of aperture 124 (as shown in FIG. 2), or between aperture 124
and the sensor array 114 to reduce the amount of extraneous
radiation reaching sensor element 116. For example, a filter may
allow only radiation in a frequency range corresponding to
radiation emitted by the radiation source 110 to reach the sensor
elements 116. In some embodiments, an optical notch filter may be
used to block undesirable radiation from reaching the sensor
elements 116. Using an optical filter can improve the operation of
sensor 100, for example, by increasing the signal-to-noise ratio in
an intensity signal.
[0056] FIG. 4 illustrates an example intensity signal 122.
Intensity signal 122 is an analog signal provided by sensor array
114. Intensity signal 122 generally has a low intensity level
corresponding to most sensor elements 116 on which little or no
radiation from radiation source 110 is incident. Intensity signal
122 has a relatively high intensity level corresponding to sensor
elements 116 upon which radiation from radiation source 110 is
incident.
[0057] In various embodiments, the dimensions and spacing of the
sensor elements 116 and the aperture 124 may be such that only one
or a few sensor elements 116 may have radiation from radiation
source 110 incident upon them. In other embodiments, the aperture
124 may be shaped to allow radiation from radiation source 110 to
be incident on a larger number of sensor elements.
[0058] In various embodiments, the intensity signal 122 may be an
analog signal or a digital signal (or a combination of both). In
embodiments in which the intensity signal is a digital signal,
intensity levels corresponding to specific array elements may have
two or more values. For example, FIG. 5 illustrates an intensity
signal 122 in which intensity levels are at either a high level or
a low level depending on whether the radiation incident on each
sensor element is below or above a threshold. In other embodiments,
the intensity of the radiation incident on each sensor element may
be reported as an intensity level within a range of values. For
example, FIG. 6 illustrates an intensity signal in which an
intensity level between a low value and a high value is provided
for each sensor element. The low value may be 0 and the high value
may be 255, if eight bits are provided for reporting the intensity
level for each sensor element.
[0059] Referring again to FIG. 4, in this embodiment, intensity
signal 122 is a raw intensity signal that is converted into a final
intensity signal 136 by processor 120. In this embodiment,
processor 120 is configured to do so in the following manner.
Processor 120 first estimates a threshold value for distinguishing
between background levels of radiation and higher levels of
radiation emitted by radiation source 110. This may be done for
example, by identifying the most common intensity level (a modal
value) and setting the threshold at a level between than the modal
intensity level and the peak levels of the raw intensity signal.
The raw intensity signal 122 may be a bi-modal signal and the
threshold may be set at a level between the two modal values. In
other embodiments, this may be done by calculating the average
intensity level (a mean value, which will typically be between the
background radiation level and the level of radiation emitted by
the radiation source 110. In other embodiments, the threshold level
may be selected in another manner. A threshold level 134 is
calculated in this example as follows:
Threshold Level 134=(Peak Intensity Level-Average Intensity
Level)*30%+Average Intensity Level
[0060] Referring to FIGS. 4 and 7, the final intensity signal 136
has a high intensity for sensor elements that had an intensity
level exceeding the threshold 134 in the raw intensity signal and a
low intensity level for sensor element that had an intensity level
at or below the threshold in the raw intensity signal.
[0061] Typically, the final intensity signal 136 will have a range
of intensity levels at the high level corresponding to sensor
elements on which radiation from radiation source 110 is incident
through aperture plate 118. In this embodiment, the processor then
identifies a center sensor element in the middle of the range of
sensor elements for which the final intensity signal 136 has a high
level. In the example of FIGS. 4 and 7, sensor array has 4096
sensor elements and the intensity levels for sensor elements 2883
to 2905 are high in the final intensity signal 136. Sensor element
2894 is the center element, as is shown in FIG. 3.
[0062] In some embodiments, the center element may be calculated
directly from the raw intensity signal. The process for selecting
the center element from the final intensity signal 136 may also be
used to calculate a center element directly from digital intensity
signal that has only two values, as illustrated in FIG. 5. In other
embodiments, the center element may be calculated in other ways.
For example, if the sensor provides a range of intensity level, as
shown in FIGS. 4 and 6, the processor may be configured to select
the sensor element with the highest sensor intensity level. In some
embodiments, the processor may filter the raw or final intensity
signal to remove spurious values. For example, an intensity signal
may be filtered to remove high intensity levels for one or a small
number of sensor elements that are surrounded by low intensity
levels. The aperture plate and the geometry of the sensor array 118
may be arranged such that radiation from the radiation source 110
will illuminate a group of sensor elements. If a small group of
elements, fewer than should be illuminated by the radiation source,
have a high intensity level and are surrounded by sensor elements
with a low intensity level, the group of elements may be treated as
having a low intensity level.
[0063] Referring again to FIG. 1, sensor 100 is positioned at a
predetermined angle relative to the x-y plane. In this embodiment,
sensor 100 is positioned at a 45.degree. angle to the x and y
dimensions. Processor 120 receives the intensity signal 122 and
determines an angle .theta. (FIG. 1) at which radiation from
radiation source 110 is incident on the sensor 100.
[0064] Processor 120 determines angle .theta. based on the center
sensor element. This may be done using a variety of geometric or
computing techniques or a combination of techniques.
[0065] A geometric technique is illustrated on FIG. 3. Processor
120 determines angle .theta. relative to a reference point, which
will typically be within the dimensions of sensor 100. In some
embodiments, the reference point may be outside the dimensions of
sensor 100. In the present embodiment, angle .theta. is determine
relative to reference point 130, which is at the centre of aperture
124. The sensor array is positioned a distance h from the aperture
plate with the centre 140 of the sensor array directly behind
reference point 130. Center sensor element 2894 is spaced a
distance d from the centre 140 of the sensor array. Angle .theta.
may be calculated as follows:
.angle..theta. = .angle..alpha. + .angle..beta. = tan - 1 ( d / h )
+ 45 .degree. ##EQU00001##
[0066] In some embodiments, a lookup table may be used to determine
angle .theta.. Angle .theta. may be calculated in advance for every
sensor element 116 in the sensor array 114 and the result may be
stored in a lookup table that is accessible to processor 120.
Processor 120 may then lookup angle .theta. after the center
element has been identified.
[0067] Collectively reference point 130 and angle .theta. define a
ray 132 along which radiation source 110 is located relative to
sensor 100.
[0068] Reference is next made to FIG. 8, which illustrates a system
200 for estimating the position of a radiation source 210 relative
to an x-y plane. System 200 includes a pair of sensors 202 and 204,
which are similar to sensor 100. Sensor 202 has a reference point
230. Ray 232 passes through reference point 230 and is at an angle
.theta. from the y-dimension. Sensor 204 has a reference point 236.
Ray 246 passes through reference point 236 and is at an angle .phi.
relative to the y dimension. Radiation source 210 lies at the
intersection of rays 232 and 246. Sensors 202 and 204 may share a
processor 220 such that their respective sensor arrays 214 and 248
provide an intensity signal to the processor 220. Processor 220
calculates rays 232 and 246 in the manner described above in
relation to ray 132 and FIG. 3. Processor 220 may calculate the
rays in any manner, including the lookup table technique described
above.
[0069] Rays 232 and 246 lies on the x-y plane. Processor 220
calculates the intersection point 250 at which rays 232 and 246
intersect. The intersection point 250 is an estimate of the
position of the radiation source 210.
[0070] Reference is next made to FIG. 9, which illustrates a
whiteboard system 300. Whiteboard system 300 includes a whiteboard
352 with a pair of sensors 302 and 304. Sensors 302 and 304 are
similar to sensors 202 and 204 of system 200 and operate in the
same manner. Sensor 302 is mounted behind a radiation shield 354
which reduces the amount of ambient radiation that is incident on
sensor 302. Similarly, sensor 304 is mounted behind a radiation
shield 356. Sensing region 311 is on the surface of the whiteboard
352. Radiation source 310 is positioned in the sensing region 311.
The embodiment of FIG. 9 may equally be used with a display screen
to form a touchscreen or an electronic whiteboard. The sensing
region 311 would be on the surface of the display screen with the
sensors 302 and 304 mounted adjacent corners of the display screen.
In other embodiments, the sensing region may be on the surface of
another writing or display surface.
[0071] Reference is made to FIG. 10. Radiation source 310 generates
and emits radiation in all directions from the radiation source.
Radiation source 310 is a ring 370 mounted to a dry erase pen 358
that is used to write on whiteboard 352. Ring 370 includes a
plurality of LEDs 372 that are powered by a battery (not shown).
Ring 370 may optionally be removable for mounting on a different
dry erase pen. LEDs 372 emit radiation that is detected by sensors
302 and 304.
[0072] Referring again to FIG. 9, sensors 302 and 304 have
reference points 330 and 336. Sensors 302 and 304 are separate by a
distance d in the x-dimension. Reference point 336 is located at
the origin of the x-y plane (that is at point (0,0)). Reference
point 330 is located at point (d,0). Radiation source 310 is
located at point (x.sub.p, y.sub.p).
[0073] A processor 320 is coupled to sensors 302 and 304. Processor
320 calculates angles .theta. and .phi. as described above. The
position of the radiation source 310 is calculated as follows:
x p = d tan .PHI. tan .PHI. + tan .theta. ##EQU00002## y p = x p
tan .PHI. ##EQU00002.2##
[0074] Processor 320 is configured to estimate to the position of
radiation source 310 repetitively. As a user writes on whiteboard
352 with pen 358, the radiation source 310 moves in conjunction
with the pen. Processor 320 tracks the movement of the radiation
source in the x-y plane. Each calculated position is recorded,
providing a record of the information written by the user on the
whiteboard.
[0075] Radiation source 310 is an active radiation source, which
generates and emits its own radiation. The emitted radiation may be
visible light or it may be outside of the visible spectrum, so long
as the sensors 302 and 304 are sensitive to the emitted
radiation.
[0076] Reference is next made to FIG. 11, which illustrates a
whiteboard system 400, which is similar to whiteboard system 300 in
structure and operation. Corresponding components are identified by
similar reference numerals. Whiteboard system 400 differs from
whiteboard system 300 in the nature of the radiation source 410.
Radiation source 410 is a passive reflective radiation source. A
pair of active fixed position radiation sources 462 and 464 are
mounted in a bezel 466 of the whiteboard 452. Each radiation source
emits radiation across all or most of the writing surface 468 of
the whiteboard.
[0077] Reference is made to FIG. 12. Radiation source 410 is a
reflective ring 470 mounted on a dry erase pen 458. Reflective ring
470 may be removable for mounting on a different dry-erase pen. In
some embodiments, reflective ring 470 may have an outer surface
covered with a reflective tape. In other embodiments, the outer
surface may be a polished metal surface.
[0078] Referring again to FIG. 10, radiation emitted by active
radiation source 462 is is incident on radiation source 410 along
line 474 and is reflected to sensor 402 along line 432. Radiation
emitted by active radiation source 464 is incident on radiation
source 410 along line 478 and is reflected to sensor 404 along line
446. Processor 420 is coupled to sensors 402 and 404 and estimates
the position of radiation source 410 as described above in relation
to whiteboard system 300. Whiteboard system 400 is able to track
the movement of pen 458 without providing an active radiation
source mounted to the pen. Optionally, the bezel 466 may be colored
to reduce reflection of radiation from the active radiation sources
462 and 464 onto sensors 402 and 404, thereby reducing the base
level of radiation that is measured by sensor elements in the
sensors, and increasing the difference in intensity of radiation
reflected by the radiation source 410 onto the sensors compared to
background or base level radiation from other sources.
[0079] Reference is next made to FIG. 13, which illustrates another
whiteboard system 500. Whiteboard system 500 is similar in
structure and operation to whiteboard systems 300 and 400 and
corresponding components are identified by corresponding reference
numerals.
[0080] Whiteboard system 500 has a plurality of active radiation
emitters 562 mounted in fixed positions in the bezel 566 of the
whiteboard 552. The radiation emitters 562 emit radiation that is
incident on sensors 502 and 504. Sensor 502 has a plurality of
sensor elements, like sensor (FIG. 3), and an aperture plate such
that radiation from each of radiation emitters 562 is incident on
only one or some of the sensor elements. In this embodiment, (i)
the shape of an aperture 524 (not shown) in the aperture plate 518
and (ii) the spacing and intensity of the active radiation sources
562 and the divergence (or collimation) of radiation emitted by the
active radiation sources may be selected such that the radiation
incident upon the sensor elements is approximately equal. The
spacing, intensity and divergence or collimation of the radiation
sources may differ around the bezel 566. In other embodiments, the
spacing, intensity or divergence or collimation, or some of these
aspects may be the same for some or all of the radiation
sources.
[0081] A pen (or other radiation blocking object) 510 is moved
about on the writing surface 568 of the whiteboard 552. The pen
blocks radiation from some of the radiation sources 562 from
reaching some of the sensor elements. Radiation blocking object 510
blocks radiation from active radiation source 562a from reaching
sensor 502 and radiation from active radiation source 562b from
reaching sensor 504.
[0082] Reference is made to FIG. 14, which illustrates a raw
intensity signal 522 from the sensor array 514 (not shown) of the
sensor 502. Raw intensity signal 522 has a relatively high
intensity level for sensor elements upon which radiation from the
radiation sources 562 and has a relatively low intensity level for
sensor elements upon which radiation from the radiation is blocked
by pen 558. Sensors 502 and 504 are coupled to a processor 520.
Referring to FIG. 15, sensor 502 determines a threshold level 534
and generates a final intensity signal 536 by comparing the raw
intensity signal 522 to the threshold level 534. In FIG. 15, sensor
elements that received less radiation than the threshold level have
a high intensity value in the final intensity signal. The processor
520 then identifies a center sensor element based on the range of
sensor elements for which final intensity signal has a high value,
in the manner described above in relation to final intensity signal
136 and FIG. 7. The processor 520 then determines angle .theta.
based on the center sensor element. Similarly, processor 520
determines angle .phi. and estimates the location of pen 558 based
on the distance d between the sensors 502, 504, and the angles 8
and cp.
[0083] Referring to FIGS. 1 to 3, sensor 100 relies on transitions
from high to low radiation levels falling on different sensor
elements 116. Similarly, sensors 502 and 504 (FIG. 13) rely on
transitions from high to low radiation levels falling on different
sensor elements 516 (not shown). The baseline or background
radiation intensity level in sensor 100 is low, while in sensor 502
it is high, but both sensors operate using similar principles to
determine a ray along which a radiation source or radiation blocker
is located.
[0084] Whiteboard system 500 can be used with a pen or other device
that blocks radiation from radiation sources 562 from reaching
sensors 502 and 504, allowing the position and movement of a
standard pen, a finger or other object on the whiteboard surface
568 to be estimated and tracked.
[0085] Referring again to FIGS. 13 and 14, whiteboard system 500 is
configured such that the radiation intensity on each of the sensor
elements in sensors 502 and 504 is approximately equal in the
absence of any radiation blocking device.
[0086] In other embodiments, the intensity of radiation reaching
the sensor elements 516 from radiation sources 562 may vary more
significantly. FIG. 16 illustrates several raw intensity signals
from a sensor in an embodiment where the radiation intensity level
across the sensor elements has not been balanced. Intensity signal
622a illustrates the relatively high variability of radiation that
is incident on different sensor elements in the absence of any
radiation blocking object such as a pen. Intensity signal 622b
illustrates the effect of using a radiation block object to block
radiation from radiation sources 562 from reaching some of the
sensor elements. In this embodiment, the processor records the
intensity signal 622a during a start-up phase of the whiteboard
system and uses the recorded intensity signal as a baseline. During
ongoing operation, the intensity signal, such as intensity signal
622b, received from the sensor array is compared to the recorded
baseline intensity signal to identify changes in the intensity
signal. The difference between the baseline intensity signal 622a
and intensity signal 622b is shown as differential intensity signal
622c. Differential intensity signal 622c is used as a raw intensity
signal to determine a threshold level and to identify a center
sensor element.
[0087] 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.
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