Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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SELECTIVE AND ADAPTIVE ILLUMINATION OF A
TARGET
TECHNICAL FIELD
[0001] The present description generally relates to the illumination of a
target. More
specifically, the present description relates to the selective and adaptive
illumination of a
target.
BACKGROUND OF THE ART
[0002] Various applications exist where the illumination of a target object or
being is
required for its observation to provide easier detection, classification,
recognition,
identification or tracking of the target. Examples for such applications
include perimeter
security and surveillance, police search operation, search and rescue,
firefighting,
industrial inspection, maintenance and road safety. Such illumination of a
target is
generally required, for example, when there is a need to observe or locate the
target in
adverse conditions such as during night, in a cluttered environment or in the
presence
of smoke, fog or dust.
[0003] Some sensors exist which provide the capability to detect targets in
night
conditions. An example of such sensors includes infrared sensors which detect
the heat
emitted by the target instead of visible light reflected by the object.
However, infrared
sensors do not allow for direct observation by human, observation by human via
visible-
waveband observation devices or observation by automatic observation devices
that
operate in other wavebands than infrared.
SUMMARY
[0004] It is an aim of the present application to provide a system and a
method that
address issues associated with the prior art.
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[0005] There are provided a system and a method for selectively and adaptively
illuminating a target. The system and the method use an illumination device
which
selectively illuminates only the target(s) and does not illuminate the
surrounding
environment, to create or amplify an illumination contrast between the target
and the
surrounding environment.
[0006] An image of the scene is first acquired using a sensing device that may
use an
infrared sensor for example. An illumination figure is calculated according to
the shape
and position of the target in the scene, as observed by the sensing device.
The target is
then selectively illuminated with the calculated illumination figure.
[0007] Accordingly, if the illumination figure is updated in time as the
target moves,
the illumination tracks the target in the scene in real-time, to create or
amplify an
illumination contrast between the target and the surrounding environment.
[0008] It is noted that more than one target may be present in the scene and
illuminated simultaneously.
[0009] The illumination device uses a sensor array to acquire an image of the
scene.
The image is then processed to extract a position and a shape of a target or
targets. An
illumination figure corresponding to the shape of the target(s) is calculated
and sent to
an illumination array that illuminates the scene. The illumination array is
coupled to
illumination imaging optics to project an illumination light with the
illumination figure
projected in the far-field, in order to obtain a superposition of the
illumination figure with
the target(s). The image acquired with the sensor array and the projected
illumination
figure are both co-registered so that an area in the scene corresponds to a
pixel in the
image and also corresponds to a corresponding pixel in the illumination
figure. The
device consequently provides selective illumination of the target(s), creating
or
amplifying a visual contrast of the target(s) against its background. Updating
the
illumination figure in time as a target moves allows for tracking of a target
according to
its displacements and the evolution of its shape.
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[0010] There are provided a method and a system for illuminating one or more
target
in a scene. An image of the scene is acquired using a sensing device that may
use an
infrared sensor for example. From the image, an illumination controller
determines an
illumination figure, such that the illumination figure adaptively matches at
least a
position of the target in the image. The target is the selectively illuminated
using an
illumination device, according to the illumination figure.
[0011] In accordance with one aspect, there is provided a system for
illuminating at
least one target in a scene. The system comprises an input for receiving an
image
acquired on the scene, the image comprising the target; an illumination device
having
an illumination field and adapted to illuminate a selected portion only of the
illumination
field according to an illumination figure for selectively illuminating the
target in the
illumination field; and an illumination controller for determining the
illumination figure
from the image such that the portion adaptively matches at least a position of
the target
in the image, the illumination figure being determined according to a known
registration
between the image and the illumination field.
[0012] In accordance with another aspect, there is provided a method for
illuminating
at least one target in a scene. The method comprising: acquiring an image of
the scene,
the image comprising the target; determining, from the image, an illumination
figure
defined on an illumination field, such that the illumination figure adaptively
matches at
least a position of the target in the image, the illumination figure being
determined
according to a known registration between the image and the illumination
field; and
illuminating a selected portion only of the illumination field according to
the illumination
figure for selectively illuminating the target in the illumination field.
[0013] In this specification, the term "target" is intended to mean any object
or being
which is to be the subject of an observation, in contrast with any other
object or being
which is considered to be part of a background or surrounding environment and
on
which no special attention is to be drawn.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Fig. 1 is a block diagram illustrating a system for selectively and
adaptively
illuminating a target in a scene, as shown in relation with the scene to be
illuminated;
[0015] Fig. 2A is a schematic view illustrating the input scene as viewed by
the
system of Fig. 1;
[0016] Fig. 2B is a schematic view illustrating an image acquired the system
of Fig. 1;
[0017] Fig. 2C is a schematic view illustrating an illumination figure to be
used by the
system of Fig. 1 to illuminate the scene;
[0018] Fig. 2D is a schematic view illustrating the illumination figure
projected on the
scene;
[0019] Fig. 2E is a schematic view illustrating the final aspect of the scene
as
illuminated by the system of Fig. 1;
[0020] Fig. 3 is a schematic view of an example illumination device to be used
in the
system of Fig. 1, wherein the illumination device comprises an array of light
sources
combined with a lens array;
[0021] Fig. 4 is a schematic view of another example illumination device to be
used in
the system of Fig. 1, wherein the illumination device comprises an array of
light sources
combined with a lens element;
[0022] Fig. 5 is a schematic view of yet another example illumination device
to be
used in the system of Fig. 1, wherein the illumination device comprises an
array of light
sources combined with a lens array and a lens element;
[0023] Fig. 6 is a schematic view of still another example illumination device
to be
used in the system of Fig. 1, wherein the illumination device comprises a
single light
sources combined with a spatial light modulator array; and
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[0024] Fig. 7 is a schematic view illustrating a system which uses a plurality
of the
system of Fig. 1 to illuminate the target from different points.
[0025] It will be noted that throughout the appended drawings, like features
are
identified by like reference numerals.
DETAILED DESCRIPTION
[0026] Now referring to the drawings, Fig. 1 illustrates a system 1 for
selectively and
adaptively illuminating a target 4 in a scene 2, the target 4 being shown in
relation with
the scene 2. The scene 2 typically includes one or more target object or
being, typically
in movement in a surrounding environment 6 (simply illustrated herein as a
pine tree).
The system 1 selectively illuminates the target 4 while limiting its
illumination of the
surrounding environment 6, in order to create or amplify an illumination
contrast
between the target 4 and the surrounding environment 6. Even though reference
to
only one target will be made generally throughout the description, it is noted
that more
than one distinct target 4 may be present in the scene 2 and selectively and
distinctively
illuminated.
[0027] The system 1 comprises a sensing device 10, an illumination device 12,
an
image processor 20 and an illumination controller 22. The sensing device 10
acquires
an image of the scene 2 in order to locate in the scene 2 the target 4 to be
illuminated.
The sensing device 10 has a sensing field of view 14 which defines how the
scene 2
projects onto the sensing device 10 to produce the image. Similarly, the
illumination
device 12 is able to illuminate an illumination field 16 in front of the
illumination device
12. In the embodiment illustrated in Fig. 1, the sensing field of view 14
essentially
corresponds to the illumination field 16 such that the scene 2 appearing on
the image is
in register with the illumination field 16. However, the illumination device
12 is adapted
to illuminate a selected portion only of the illumination field 16 by an
adaptive beam 18
in order to selectively illuminate the target 4. The illuminated target 4 then
acts as a
screen which receives the illumination and all the attention of an observer is
consequently directed to the illuminated target 4.
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[0028] When in operation, images of the scene 2 are first acquired by the
sensing
device 10 in order to locate the target 4 in the scene. The acquired images
are
processed by the image processor 20 in order to extract from the images the
position
and the shape of the target 4 within the scene 2. The extracted position and
shape are
provided to the illumination controller 22 which determines, from the
extracted position
and the shape of the target 4 in the images, an illumination figure that is
used by the
illumination device 12 in forming the adaptive beam 18 to illuminate the scene
2 such
that the portion illuminated substantially matches the shape and the position
of the
target 4. The determination of the illumination figure takes into account a
known
registration between the sensing field of view 14 and the illumination field
16.
[0029] It is noted that, in some embodiments, the image processing required on
the
image to extract the position and the shape of the target 4 consists of
applying a
threshold on pixel values of the acquired image. This processing may be
included in the
sensing device 10. The images, to which the threshold has been applied, is
then directly
provided to the illumination controller 22 which directly converts it into a
matching
illumination figure. The image processor 20 is therefore considered to be
optional. This
will be readily understood from the description of Figs. 2A-2E.
[0030] In the embodiment of Fig. 1, the sensing device 10 is an infrared
sensor, e.g.
an infrared camera. The body of any being, i.e. a human being or an animal,
generates
heat that is detected by infrared sensors. Other objects such as vehicles in
general also
typically produce heat that can also be detected by infrared sensors.
Accordingly,
detection of this heat using an infrared sensor allows the location of a
target 4 in the
scene 2. The sensing device 10 may also operate in the x-ray spectrum, the
ultra-violet
spectrum, the near-infrared spectrum, the mid-infrared spectrum, the long-
infrared
spectrum or the terahertz spectrum for example.
[0031] The sensing device 10 comprises a sensor array 24, such as a
microbolometer for example, and sensor imaging optics 26 placed in front of
the sensor
array 24 and consisting of one or a plurality of lenses used to adequately
project the
electromagnetic field received onto the sensor array 24. The sensor imaging
optics 26
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defines the sensing field of view 14 for the image acquisition. Other types of
sensor
arrays 24 may also be used such as vanadium oxide (VOX) sensors, mercury
cadmium
telluride (MCT) sensors, indium antimonide (InSb) sensors and resistive
amorphous
silicon sensors. Also, if the sensing device operates in the visible or the
ultra-violet
spectrum, a Charge-Coupled Device (CCD) or a Complementary Metal-Oxide-
Semiconductor (CMOS) may be used. Other sensing devices may also be used as
well.
[0032] The illumination device 12 comprises an illumination array 28 which
comprises
an array of light sources, such as an array of laser diodes or of light-
emitting diodes,
and illumination imaging optics 30 disposed in front of the illumination array
28. Each
light source of the illumination array 28 provides an illumination that is
spatially
separated from the illumination of the adjacent light sources. Accordingly, by
activating
selected light sources, it is possible to create an adaptive illumination
figure or pattern
for the adaptive beam 18 that corresponds to the shape and the position of the
target 4,
such that most of the light is screened by the target 4. The illumination
imaging optics
30 consists of a lens array in this case and is used to adequately reproduce
the
illumination figure produced by the illumination array 28 in the far-field,
i.e. on the scene
2.
[0033] Now referring to Fig. 2, the operation of the system 1 is being
described.
Fig. 2A illustrates the scene 2 as appearing in the sensing field of view 14.
Fig. 2B
illustrates the image 210 of the scene acquired by the sensing device 10,
after
processing by the image processor 20. The image processor 20 may apply any
processing algorithm to the image 210 so as to obtain a clean enough image of
the
scene 2 to allow the locating of the target 4. The image is divided in an
array of pixels
212 defined by the pixels of the sensor array 24. In the illustrated
embodiment, the
sensor device 10 is an infrared sensor. In this case, each pixel is simply
associated with
an infrared intensity value. A high intensity value indicates the presence of
a target 4 on
that pixel. Accordingly, heat emitted by the human and the dog are
preferentially
detected in comparison with the surrounding environment. The intensity values
show
different levels of intensity as a function of the level of electromagnetic
radiation
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received from the scene. In this case, the image processing applied on the
image 210
consists in applying a given threshold to the infrared intensity value of each
pixel, to
determine whether the pixels correspond to the background or to a target to be
illuminated. In Fig. 2B, some pixels with a high intensity level are shown at
214, while
other pixels with a lower intensity level are shown at 214, and pixels with an
intensity
level below the given threshold are shown at 212.
[0034] Fig. 2C illustrates the illumination figure 220 to be used to
illuminate the scene
2 with the adaptive beam 18, as determined by the illumination controller 22
from the
image 210 so as to adapt the illumination to the detected target 4. Each pixel
222 of the
illumination figure 220 typically corresponds to a light source of the
illumination array 28,
such that each pixel 222 is used to illuminate a specific area of the
illumination field 16.
Pixels 222 of the illumination figure 220 that are activated, i.e. pixels 224
and pixels
226, define the portion of the illumination field 16 that is illuminated. The
pixels 224 and
226 of the illumination figure 220 correspond to a pixel 214 and 216 of the
image where
heat is detected. Pixels 224 and 226 are therefore activated. All pixels 222
corresponding to pixels 212 where no heat is detected are deactivated. It is
noted that
the illumination figure 220 may also include intensity levels for the
illumination. For
pixels 214 showing a high intensity level on the image 210, a high intensity
illumination
is also used (shown as by pixels 224 in Fig. 2C), and for pixels 216 showing a
low
intensity level on the image 210, a low intensity illumination is also used
(shown by
pixels 226 in Fig. 2C).
[0035] In the illustrated case, each pixel of the image 210 directly
corresponds to a
pixel of the illumination figure 220 such that the mapping between the image
210 and
the illumination figure 220 is directly obtained. The image 210 and the
illumination figure
220 are then impliedly co-registered such that a same pixel in the image 210
and the
illumination figure 220 matches to correspond to the same area on the scene.
There is a
correspondence, pixel-by-pixel, between the topology of the sensor array 24,
the
topology of the illumination array 28 and the topology of the scene 2.
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[0036] In other cases, the image 210 and the illumination figure 220 may have
different numbers of pixels, i.e. different resolutions, and may cover
slightly different
field of views. In this case, the registration, i.e. the mapping, referencing
the image 210
and the illumination figure 220 from one another is not direct and is known
and used by
the illumination controller 22 to map pixels of the image 210 to pixels of the
illumination
figure 220.
[0037] Fig. 2D illustrates the illumination figure 220 as projected on the
scene 2. Only
the selected portion of the illumination field 16 corresponding to the
detected target 4 is
illuminated. Fig. 2E illustrates the final aspect of the scene 2 as
illuminated by the
adaptive beam 18. The target 4 is selectively illuminated in the scene 2 and
therefore
better contrasts against its surrounding environment 6.
[0038] As the shape and the position of the target 4 change, i.e. as the
target 4
moves in the scene, the system 1 updates the illumination figure 220 in real-
time, so
that it continues to illuminate the target 4. Accordingly, the system 1
continues to
illuminate the target 4 when its position, scale or aspect changes. The
illumination
tracks the target 4 in the scene 2.
[0039] In the embodiment described with reference to Figs. 2A-2E, the
illumination
figure 220 is adapted to match the shape and the position of the target 4 from
information provided by the image 210. In another embodiment, the illumination
figure is
such that only the central portion, or any other portion, of the target 4 is
illuminated with
a predetermined shape that is not necessarily matching the one of the target
4. A solid
circle or square is simply used no matter the shape of the target 4. It is
noted that the
dimensions of such a shape non-matching illumination figure may still be
adapted to the
dimensions of the target 4 such that a portion of the target 4 is illuminated
while limiting
the illumination of the surrounding environment 6.
[0040] In the case illustrated in Fig. 2, the sensing device 10 operates in
the infrared
spectrum and the infrared intensity as appearing on the image 210, which is
representative of the shape and position of the target 4 in the scene 2, is
simply
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converted into an illumination figure 220. The optional image processor 20 may
then be
considered as omitted since the sensing device 10 intrinsically extracts the
shape and
the position of the target. It is noted that in the case of a sensing device
10 not
operating in the infrared spectrum but rather in a different electromagnetic
spectrum,
conversion of the acquired image into an illumination figure may be more
complex. The
image processor 20 is then used to extract the shape and the position of the
target 4 in
the image 210. The target 4 should be first extracted in the image 210 from
different
parameters. For example, extraction of a target 4 in the image 210 may be
based on
movement such that the part of the image that changes in time may be
identified as a
target 4. A predetermined shape or color of a target may also be looked for in
the
image. A recognition algorithm may then be used.
[0041] Furthermore, it is noted that if the scene 2 includes more than one
target 4, the
illumination figure 220 simply adapts to illuminate more than one distinct
portion of the
illumination field corresponding to the different targets 4.
[0042] Figs. 3 to 6 show different example embodiments of the illumination
device 12.
It is noted that the cross-section views of Figs. 3 to 5 only show one-
dimension arrays of
light sources for simplicity purposes. It should be understood that the arrays
are
actually two-dimensional.
[0043] Fig. 3 shows an example embodiment of the illumination device 12. In
the
embodiment of Fig. 3, the light sources 328 are generally disposed side-by-
side on a
concave surface. A lens 330 is placed in front of each light source 328 so as
to define a
lens array 332. The hatching on Fig. 3 represents the illumination angle of
each light
source-lens combination. Generally speaking, the rotation angle between
consecutive
light sources 328 is equal to the illumination angle (the divergence of light
source-lens
combination). The summation of all the illumination angles defines the
illumination field
16. The lenses 330 are chosen so that the shape of the illumination figure
generated by
the illumination device is preserved in the far-field, i.e. at the position of
the target 4. It is
noted that each lens 330 may consist of a single lens element or of a multiple
lens
element, i.e. a compound lens.
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[0044] Fig. 4 shows another example embodiment of the illumination device 12.
In the
embodiment of Fig. 4, the light sources 428 are disposed side-by-side on a
substantially
planar surface. The illumination imaging optics consist of a focusing lens 430
and is
disposed in front of the light sources 428 such that the light sources 428 are
located at
or near the front focal point of the lens 430. The focusing lens 430 preserves
the
illumination figure 220 in the far-field such that the adaptive beam 18 is
similar to the
target 4 in terms of shape and position. It is noted that the focusing lens
430 may
consist of a single or a multiple lens element.
[0045] Fig. 5 shows still another example embodiment of the illumination
device 12.
In the embodiment of Fig. 5, the light sources 528 are also disposed side-by-
side on a
substantially planar surface. A lens 530 is placed in front of each light
source 528 so as
to define a lens array 532. A focusing lens 534 is additionally disposed in
front of the
lens array 532 such that the lens array 532 is located at or near the front
focal point of
the lens 534. The illumination imaging optics, which consist of the lens array
532 and
the focusing lens 534, is designed to preserve the illumination figure 220 in
the far-field.
Again, the lenses 530 and the focusing lens 534 may each consist of a single
or a
multiple lens element.
[0046] Fig. 6 shows another example embodiment of the illumination device 12.
In
this embodiment, the illumination device 12 comprises a single light source
628 with a
wide angular spread and a spatial light modulator array 630 coupled to the
light source
628 so as to define an array of illumination zones 632 individually
corresponding to
points in the illumination figure.
[0047] In the configurations presented in Figs. 3, 4, 5 and 6 the registration
between
the illumination field 16 and the sensing field of view 14 is generally
obtained by
designing the illuminating imaging optics and the sensor imaging optics so
that the field
of view of the illumination imaging optics match the field of view of the
sensor imaging
optics 26.
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[0048] Fig. 7 shows a system 700 which uses a plurality of the systems 1 as
described herein, to illuminate the target 4 from different directions. The
system 700
comprises a plurality of systems 1 positioned at different view points
relative to the
scene 2. Each system 1 extracts the positions and shapes of the target 4 from
a
different direction. The target 4 is then illuminated from different points.
The systems 1
are thus intrinsically collaborative since the illumination adds up only on
the target 4,
producing an illumination contrast of the target 4 that is more intense and
that covers
larger proportions of the surface of the target 4, while the surrounding
environment 6
still receives minimal illumination. The contrast between the target 4 and the
surrounding environment 6 is thus increased. Moreover, the eventual lack of
illumination
from one system 1 is compensated by the illumination provided by the other
systems 1.
[0049] It is noted that, while throughout the description the sensor array 24
and the
illumination array 28 are considered to be two-dimensional arrays, one-
dimensional
arrays, i.e. lines, may also be used.
[0050] It is also noted that the sensing device 10 may consist of a three-
dimensional
scanner such as a stereoscopic sensor, acquiring three-dimensional images of
the
scene 2. In this case, the acquired three-dimensional information, i.e. the
depth of the
image, is used to extract the target 4 within the scene 2. In an example
embodiment,
anything appearing on the three-dimensional image closer than a given depth
relative to
the sensing device 10 is extracted as a target 4. The illumination device 12
then
illuminates the target 4 which, in fact, consist of anything in the scene 2
that is closer
than a depth threshold relative to the sensing device 10.
[0051] The sensing device 10 may also consist of a gas sensor, such as a LIDAR
sensor, detecting the presence of a gas in the scene 2. In this case, when a
gas other
than normal atmosphere is detected in the scene 2 or when a specific gas is
detected in
the scene 2, the detected gas is extracted as a target 4. The illumination
device 12
illuminates the target 4, consisting of a gas, which then shows as an
illuminated cloud.
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[0052] Both the sensor device 10 and the illumination device 12 may operate at
various electromagnetic spectral wavebands. In the embodiments described
herein, the
sensor device 10 and the illumination device 12 operate in different
electromagnetic
wavebands. The system 1 uses information acquired in a first waveband in order
to
enhance the illumination contrast of the target 4 relative to the surrounding
environment
6 in another waveband. It is however noted that the sensor device 10 and the
illumination device 12 may rather operate in the same electromagnetic
waveband. For
example, the sensor device 10 may acquire color images in the visual spectrum
while
the illumination device 12 illuminates using white light sources.
[0053] It is noted that, in the embodiments described herein, the resolution
of both the
sensing device 10 and the illumination device 12 may be quite low while still
achieving
good target illumination accuracy. Both the sensor array 24 and the
illumination array 28
can typically have a low pixel count. The purpose of the system 1 is to
illuminate a
target 4, with its shape, in order to enhance its visibility against the
surrounding
environment 6. As such, the whole target 4 to be illuminated may ultimately
correspond
to only a few pixels of the illumination array 28, as long as the target shape
is generally
preserved. In turn, the few pixels of the illumination array 28 may correspond
to only few
pixels of the sensor array 24. The resolution required is thus relatively low
for both the
illumination array 28 and the sensor array 24.
[0054] Even though the target 4 is fully illuminated with only a few activated
pixels of
the illumination array 28, i.e. a few light source elements, all details of
the target 4 are
still visible and the whole spatial resolution of the target 4 is fully
available for the final
observation, whether it is made by a human eye or an observation instrument.
The
resolutions of the sensor array 24 and of the illumination array 28, even if
very low, do
not have an impact on the final spatial resolution of the scene as observed.
Consequently, with a suitable illumination intensity, the sensor array 24 and
the
illumination array 28 may have a low resolution without compromising the
quality of the
observation.
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[0055] It is noted that while the use of a low resolution sensor array and of
a low
resolution illumination array has an important impact on size and cost of the
system 1,
high resolutions may also be used.
[0056] Using a low resolution for the sensor array 24 generates a reduced
amount of
data. The acquisition rate of the sensor array 24 can thus be increased
without
generating a too large amount of data. It also allows the use of an averaging
technique
on the acquired images such that acquired images are added over time to reduce
the
noise or to increase the sensitivity of the averaged image.
[0057] It will be understood that the sensing device 10 and the image
processor may
be provided separately from the system 1, the system 1 then comprising an
illumination
device 12, an illumination controller 22 and an input for receiving the image
as acquired
and processed.
[0058] The applications of the system 1 are various. The system 1 may be used
in
perimeter security and surveillance, for use in the open areas and at the
outside of a
prison for example. The system 1 may continuously look for a being, which will
be
considered as a target. The system then automatically tracks the target by
illuminating it
as it moves. Similarly, the system 1 may also be used on a private outdoor
property to
surprise a person who may be trespassing on the property. The system 1 may
also be
used in police pursuits, police search operations and search and rescues.
[0059] In another example application, the system 1 may be mounted to a car in
replacement of or in addition to the car's headlights, in order to improve
visibility in
adverse conditions. It may also be added to or integrated in a fire fighting
equipment to
improve visibility in adverse visibility conditions.
[0060] While illustrated in the block diagrams as groups of discrete
components
communicating with each other via distinct data signal connections, it will be
understood
by those skilled in the art that the illustrated embodiments may be provided
by a
combination of hardware and software components, with some components being
implemented by a given function or operation of a hardware or software system,
and the
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data paths illustrated being implemented by data communication within a
computer
application or operating system. The structure illustrated is thus provided
for efficiency
of teaching the described embodiment.
[0061] The embodiments described above are intended to be exemplary only. The
scope of the invention is therefore intended to be limited solely by the
appended claims.
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