U.S. patent application number 13/411381 was filed with the patent office on 2012-06-28 for integrated light emitting and light detecting device.
This patent application is currently assigned to QUALCOMM MEMS Technologies, Inc.. Invention is credited to Alok Govil, Jonathan Charles Griffiths, Manish Kothari, Gaurav Sethi, James Randolph Webster.
Application Number | 20120161009 13/411381 |
Document ID | / |
Family ID | 41429473 |
Filed Date | 2012-06-28 |
United States Patent
Application |
20120161009 |
Kind Code |
A1 |
Kothari; Manish ; et
al. |
June 28, 2012 |
INTEGRATED LIGHT EMITTING AND LIGHT DETECTING DEVICE
Abstract
Methods and systems for providing a light device that can emit
light and sense light are disclosed. In one embodiment, a lighting
device includes a light guide having a planar first surface, the
light guide configured such that at least some ambient light enters
the light guide through the first surface and propagates therein,
and at least one light detector disposed along an edge of the light
guide, the at least one detector optically coupled to the light
guide to receive light propagating therein. The light detector can
be configured to produce a control signal. In some embodiments, the
lighting device also includes at least one light turning feature
disposed on the first surface, the at least one light turning
feature configured to direct light incident into the light guide
through the first surface.
Inventors: |
Kothari; Manish; (Cupertino,
CA) ; Webster; James Randolph; (San Jose, CA)
; Sethi; Gaurav; (Dublin, CA) ; Govil; Alok;
(Santa Clara, CA) ; Griffiths; Jonathan Charles;
(Fremont, CA) |
Assignee: |
QUALCOMM MEMS Technologies,
Inc.
San Diego
CA
|
Family ID: |
41429473 |
Appl. No.: |
13/411381 |
Filed: |
March 2, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12559085 |
Sep 14, 2009 |
8138479 |
|
|
13411381 |
|
|
|
|
61147044 |
Jan 23, 2009 |
|
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Current U.S.
Class: |
250/349 ;
250/208.2; 29/825 |
Current CPC
Class: |
Y10T 29/49117 20150115;
H05B 47/105 20200101; H05B 47/115 20200101; G06F 3/0428 20130101;
G06F 2203/04109 20130101; Y02B 20/40 20130101; H05B 47/13
20200101 |
Class at
Publication: |
250/349 ;
250/208.2; 29/825 |
International
Class: |
G01J 5/10 20060101
G01J005/10; H01R 43/00 20060101 H01R043/00; G01J 1/42 20060101
G01J001/42 |
Claims
1. A lighting device, comprising: a light guide having a first
edge, a second edge, and a first surface extending between the
first edge and the second edge, the first surface configured to
receive incident light; a first light detector disposed along the
first edge of the light guide and coupled to the light guide to
receive light propagating therein, the first light detector
configured to produce a first signal based on an amount of light
received from the light guide through the first edge; and a second
light detector disposed along the second edge of the light guide
and coupled to the light guide to receive light propagating
therein, the second light detector configured to produce a second
signal based on an amount of light received from the light guide
through the second edge, wherein the first light detector and the
second light detector are electrically connected and configured to
produce a control signal indicating a direction of movement of an
object relative to the light guide based at least in part on the
first signal and the second signal.
2. The device of claim 1, further comprising a differential
amplifier including the first light detector and the second light
detector, the differential amplifier having an output terminal and
being configured to provide the control signal to the output
terminal for providing to a device electrically connected to the
output terminal.
3. The device of claim 1, wherein the control signal indicates a
direction of movement of the object relative to the first edge and
the second edge.
4. The device of claim 1, wherein the control signal indicates a
direction of movement of the object relative to the first
surface.
5. The device of claim 4, wherein the control signal indicates a
change of distance between the first surface and the object.
6. The device of claim 1, further comprising at least one light
gathering feature disposed on the first surface and configured to
couple light incident on the first surface into the light
guide.
7. The device of claim 1, further comprising: at least one light
source optically coupled to at least one edge of the light guide;
and at least one light turning feature configured to direct light
propagating in the light guide out of the light guide.
8. The device of claim 7, wherein the control signal is configured
to control at least a portion of the output of the at least one
light source.
9. The device of claim 8, wherein the first and second light
detectors are configured to sense IR radiation and the at least one
light source comprises a visible light source.
10. The device of claim 8, wherein the first and second light
detectors are configured to sense visible light and the at least
one light source comprises an IR radiation source.
11. The device of claim 8, wherein the at least first and second
light detectors are configured to sense IR radiation and the at
least one light source comprises an IR radiation source.
12. The device of claim 8, wherein the first and second light
detectors are configured to sense visible light and the at least
one light source comprises a visible light source.
13. The device of claim 1, wherein the first and second light
detectors comprise a photodiode.
14. A method of manufacturing a lighting device, comprising:
providing a light guide having a first edge, a second edge, and a
first surface extending between the first edge and the second edge;
disposing a first light detector along the first edge of the light
guide, the first light detector coupled to the light guide to
receive light propagating therein through the first edge, the first
light detector configured to produce a first signal based on an
amount of light received from the light guide through the first
edge; disposing a second light detector along the second edge of
the light guide, the first light detector coupled to the light
guide to receive light propagating therein through the second edge,
the second light detector configured to produce a second signal
based on an amount of light received from the light guide through
the second edge; and electrically connecting the first light
detector and the second light detector, the first and second light
detectors being configured to produce a control signal indicating a
direction of movement of an object relative to the light guide
based at least in part on the first signal and the second
signal.
15. The method of claim 14, wherein electrically connecting the
first light detector and the second light detector includes forming
a differential amplifier including the first light detector and the
second light detector, the differential amplifier having an output
terminal and being configured to provide the control signal to the
output terminal for providing to a device electrically connected to
the output terminal.
16. The method of claim 14, wherein the control signal indicates a
direction of movement of the object relative to the first edge and
the second edge.
17. The method of claim 14, wherein the control signal indicates a
direction of movement of the object relative to the first
surface.
18. The method of claim 17, wherein the control signal indicates a
change of distance between the first surface and the object.
19. The method of claim 14, further comprising forming at least one
light gathering feature on the first surface, the at least one
light gathering feature configured to direct light incident on the
light guide into the light guide.
20. The method of claim 14, further comprising disposing at least
one light source along one or more edges of the light guide.
21. The method of claim 20, further comprising forming at least one
light turning feature on the light guide, the at least one light
turning feature configured to direct light propagating within the
light guide away from the light guide.
22. A lighting device, comprising: a light guide having a first
edge, a second edge, and a first surface extending between the
first edge and the second edge, the first surface configured to
receive incident light; first means for detecting light disposed
along the first edge of the light guide and coupled to the light
guide to receive light propagating therein, the first light
detecting means configured to produce a first signal based on an
amount of light received from the light guide through the first
edge; second means for detecting light disposed along the second
edge of the light guide and coupled to the light guide to receive
light propagating therein, the second light detecting means
configured to produce a second signal based on an amount of light
received from the light guide through the second edge; and means
for detecting a direction of movement of an object relative to the
light guide, the movement detecting means including the first light
detecting means and the second light detecting means and being
configured to produce a control signal indicating the detected
direction of movement of the object based at least in part on the
first signal and the second signal.
23. The lighting device of claim 22, wherein the first light
detecting means includes at least one light detector, wherein the
second light detecting means includes at least one light detector,
and wherein the movement detecting means includes the first light
detecting means and the second light detecting means.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 12/559,085, filed Sep. 14, 2009, titled "INTEGRATED LIGHT
EMITTING AND LIGHT DETECTING DEVICE," which claims the benefit of
U.S. Provisional Application No. 61/147,044 filed on Jan. 23, 2009,
titled "INTEGRATED LIGHT EMITTING AND LIGHT DETECTING DEVICE." Each
of these applications is expressly incorporated by reference in its
entirety.
BACKGROUND
[0002] 1. Field
[0003] This invention relates to the fields of lighting and
sensing, and in particular to light panels configured to emit light
and/or detect light.
[0004] 2. Description of the Related Art
[0005] A variety of architectural lighting configurations are
utilized to provide artificial illumination in a variety of indoor
and/or outdoor locations. Such configurations can include fixed and
portable architectural lighting. Various configurations employ
technologies such as incandescent, fluorescent, and/or light
emitting diode based light sources.
[0006] One configuration of architectural lighting can be referred
to generally as panel lighting. A panel lighting may include, for
example, incandescent or fluorescent lighting in a light box behind
a plastic lenticular panel. Panel lighting can be configured as a
generally planar lighting devices, having width and length
dimensions significantly greater than a thickness dimension. Panel
lighting can use LED's as a light source, thus allowing its use in
applications not suitable for normal incandescent or fluorescent
light sources, including thinner panel configurations. Accordingly,
improvements to panel lighting could allow its use for additional
lighting applications not suitable for normal light sources.
SUMMARY
[0007] The system, method, and devices of the invention each have
several aspects, no single one of which is solely responsible for
its desirable attributes. Without limiting the scope of this
invention, its more prominent features will now be discussed
briefly. After considering this discussion, and particularly after
reading the section entitled "Detailed Description of Certain
Embodiments," one will understand how the features of this
invention provide advantages over other lighting devices.
[0008] At least some embodiments are based at least partially on a
recognition that there exists an unsatisfied need for novel
configurations of architectural lighting that offer improvements.
For example, some embodiments provide a light panel configured to
emit light and to detect a variation of light incident on the light
panel. Some embodiments include a plurality of light turning
features that direct light in one or more selected directions into
or out of a light panel. Light received by a light panel may be
guided within the light guide to one or more detectors.
[0009] According to one embodiment, the invention comprises a
lighting device having a first light guide having a planar first
surface and a planar second surface, at least one light gathering
feature disposed on the first surface and configured to couple
light incident on the first surface of the first light guide into
the first light guide, and at least one light detector disposed
along an edge of the first light guide coupled to the first light
guide to receive light propagating therein, the at least one light
detector configured to produce a control signal. In one aspect, the
at least one light gathering feature comprises at least one of a
diffractive feature, a reflective feature, a refractive feature,
and a holographic film. In another aspect, the at least one light
detector further comprises an output terminal, and wherein the at
least one light detector is configured to provide the control
signal to the output terminal for providing to a device
electrically connected to the output terminal.
[0010] In one embodiment, the lighting device includes at least one
light source optically coupled to at least one edge of the first
light guide and at least one light turning feature configured to
direct light propagating in the first light guide out of the first
light guide. In one aspect, the control signal is configured to
control at least a portion of the output of the at least one light
source. In another aspect, the at least one turning feature
includes more than one turning feature disposed on the front
surface and/or back surface. In one aspect, the at least one light
detector is configured to sense IR radiation and/or visible light
and the at least one light source is configured to emit IR
radiation and/or visible light. The light source can be configured
to emit light having a wavelength within a first range and the at
least one light detector can be configured to detect light having a
wavelength within a second range and the first and second ranges
can overlap or not overlap. In yet another aspect, the at least one
light turning feature comprises a dot, groove, diffractive grating,
hologram, and/or prismatic feature. In one aspect, the at least one
light detector comprises a photodiode.
[0011] In another aspect, the at least one light detector includes
a first detector disposed on a first edge of the first light guide
and a second detector disposed on a second edge of the first light
guide. In one aspect, the first and second detectors are each
configured to provide control signals based on the light they
receive. In another aspect, the first and second detectors can be
coupled to a sensing circuit configured to determine a signal
indicating a variation of light incident on the light guide based
on the control signals. In one aspect the first edge can be
disposed opposite the second edge. In yet another aspect, the
sensing circuit signal can be configured to provide an indication
of a direction of variation of incident light across the light
guide. In one aspect, the first and second detectors are configured
to produce a signal indicative of an object moving across at least
a portion of the first surface that affects the light incident on
the first surface.
[0012] In another aspect, the lighting device also includes a
second light guide disposed parallel to the first light guide and
an isolation layer disposed between the first light guide and the
second light guide. The isolation layer can be configured to
prevent at least some light propagating in the first light guide
from entering the second light guide and/or to prevent at least
some light propagating in the second light guide from entering the
first light guide. In one aspect, the isolation layer comprises a
material having a refractive index lower than the refractive index
of the first and second light guide. In one aspect, the isolation
layer has a refractive index that is between about 1.4 and about
1.6, the first light guide has a refractive index that is between
about 1.4 and about 1.6, and the second light guide has a
refractive index that is between about 1.4 and about 1.6. The
isolation layer can include a material with an index of refraction
between about 1.4 and about 1.6. In one aspect, the at least one
light gathering feature comprises a dot, groove, diffractive
grating, hologram, and/or prismatic feature.
[0013] According to another embodiment, the invention comprises a
lighting system including a first lighting device having a first
light guide having a planar first surface and a planar second
surface, at least one light gathering feature disposed on the first
surface and configured to couple light incident on the first
surface of the first light guide into the first light guide, at
least one light detector disposed along an edge of the first light
guide coupled to the first light guide to receive light propagating
therein, at least one light source optically coupled to at least
one edge of the first light guide, and at least one light turning
feature configured to direct light propagating in the first light
guide out of the first light guide. The lighting system can also
include a second lighting device configured to provide a control
signal to the at least one light detector, wherein the at least one
light detector is configured to control the light output from the
at least one light source. In one aspect, the control signal
comprises light output from the second lighting device. In another
aspect, the light output from the second lighting device is pulse
width modulated.
[0014] According to another embodiment, the invention comprises a
method of manufacturing a lighting device including providing a
light guide having a planar first surface and a planar second
surface, disposing a first light detector along one or more edges
of the light guide, the first light detector coupled to the first
light guide to receive light propagating therein, disposing a
second light detector along one or more edges of the light guide,
the first light detector coupled to the first light guide to
receive light propagating therein, forming a sensing circuit
electronically coupled to the first light detector and the second
light detector, the sensing circuit configured to determine a
signal indicating a variation of light incident on the light guide
based on signals provided by the first and second detector, forming
at least one light gathering feature on at least one of the first
surface and the second surface, the at least one light gathering
feature configured to direct light incident on the light guide into
the light guide, forming at least one light turning feature on at
least one of the first and second surface, the at least one light
turning feature configured to direct light propagating within the
light guide away from the light guide, and disposing at least one
light source along one or more edges of the light guide.
[0015] According to yet another embodiment, the invention comprises
a lighting device including means for guiding light, means for
detecting light, the means for detecting light disposed along one
or more edges of the means for guiding light, the means for
detecting light configured to detect light propagating within the
means for guiding light, the means for detecting light further
configured to produce a control means, and means for gathering
light disposed on the means for guiding light, the means for
gathering light configured to couple light incident on the means
for guiding light into the means for guiding light. In one aspect,
the means for guiding light comprises a light guide having a planar
first surface and a planar second surface. In another aspect, the
means for detecting light comprises at least one light detector
disposed along an edge of the means for guiding light and coupled
to the means for guiding light to receive light propagating
therein. In one aspect, the means for gathering light comprises one
or more light gathering features. In yet another aspect, the
lighting device also includes means for producing light, the means
for producing light coupled to the means for guiding light, and
means for turning light disposed on the means for guiding light,
the means for guiding light configured to direct light propagating
within the means for guiding light away from the means for guiding
light. In one aspect, the means for turning light comprises at
least one light turning feature. In another aspect, the means for
producing light comprises at least one light source.
[0016] According to one embodiment, the invention comprises a
method of sensing movement of an object across a lighting panel
based on the variation of light incident on the lighting panel, the
lighting panel having at least two detectors coupled to the
lighting panel, the method including at a first time, receiving
light propagating within the lighting panel at the first detector
and producing a first signal, the first signal indicating the
amount of light detected by the first light detector at the first
time, and receiving light propagating within the lighting panel at
the second detector and producing a second signal, the second
signal indicating the amount of light detected by the second
detector at the first time, at a second time, receiving light
propagating within the lighting panel at the first detector and
producing a third signal, the third signal indicating the amount of
light detected by the first light detector at the second time, and
receiving light propagating within the lighting panel at the second
detector and producing a fourth signal, the fourth signal
indicating the amount of light detected by the second detector at
the second time, and determining the direction of the movement of
the object based on the first, second, third, and fourth signals.
In one aspect, the method also includes emitting light from the
light panel wherein receiving light propagating within the lighting
panel at the first time and the second time comprises receiving
ambient light that is incident on the lighting panel and light that
was emitted from the light panel and reflected back toward the
lighting panel.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a side view schematically illustrating one
embodiment of a light panel configured to emit light.
[0018] FIG. 2 is an enlarged view of a portion of the light panel
depicted in FIG. 1.
[0019] FIG. 3 is a side view schematically illustrating one
embodiment of a light panel that may be coupled with a reflective
display.
[0020] FIG. 4 is an enlarged view of a portion of the light panel
depicted in FIG. 3 illustrating light turning features.
[0021] FIG. 5 is a side view of a light panel illustrating one
embodiment configured to detect ambient light incident on one or
more surfaces of the light panel.
[0022] FIG. 6 is a side view of a light panel illustrating one
embodiment which is configured to detect light incident on a
surface of the light panel where at least some of the incident
light is provided by a light source.
[0023] FIG. 7 is a top view schematically illustrating one
embodiment of a light panel configured to detect variations in
light incident on a surface of the light panel, including
variations caused by moving an object (e.g., a hand) across a
surface of the light panel.
[0024] FIG. 8 is a diagram schematically illustrating two
photodiodes electrically connected in a configuration to provide a
signal corresponding to the direction a sensed object moves across
a surface of the light panel.
[0025] FIG. 9 is a diagram schematically illustrating signals based
on the output of the two photodiodes depicted in FIG. 7 as a hand
is moved across the light panel.
[0026] FIG. 10 is a side view schematically illustrating one
embodiment of a panel configured to emit light across the panel and
light an object proximate to the panel
[0027] FIG. 11 is a side view schematically illustrating one
embodiment of a panel configured to emit light and detect
variations in light falling incident an object proximate to the
panel.
[0028] FIG. 12 is a top view schematically illustrating one
embodiment of a light panel.
[0029] FIG. 13 is a side view schematically illustrating the light
panel depicted in FIG. 12.
[0030] FIG. 14 is a top view schematically illustrating one
embodiment of a light panel.
[0031] FIG. 15 is a side view schematically illustrating the light
panel depicted in FIG. 14.
[0032] FIG. 16 is a side view schematically illustrating an
embodiment of a light panel configured to emit and detect light
disposed near a reflector.
[0033] FIG. 17 is a side view schematically illustrating an
embodiment of a light panel configured to emit and detect
light.
[0034] FIG. 18 is a side view schematically illustrating an
embodiment of a light panel configured to emit and detect
light.
[0035] FIG. 19 is a side view schematically illustrating an
embodiment of a light panel configured to emit and detect light
having two light guides separated by a low refractive index
layer.
[0036] FIG. 20 is a top view schematically illustrating an
embodiment of a light panel configured to emit and detect
light.
[0037] FIG. 21 is a top view schematically illustrating an
embodiment of a light panel configured to emit and detect
light.
[0038] FIG. 22 is a pulse width modulation diagram.
[0039] FIG. 23 is a pulse width modulation diagram.
DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS
[0040] The following detailed description is directed to certain
specific embodiments of the invention. However, the invention can
be embodied in a multitude of different ways. For example, features
included in a light emitting panel may also be included in a light
sensing panel. In this description, reference is made to the
drawings wherein like parts are designated with like numerals
throughout.
[0041] In various embodiments described herein, a light source
and/or light detector, or sensor, is coupled to a light guide to
form a light panel. The light guide may comprise a plate, sheet or
film with light turning features, for example, light extraction
dots, grooves, diffractive gratings, holograms, or prismatic
features disposed on one or more of its surfaces. Ambient light
that is incident on the light guide may be gathered and turned into
the light guide by the light turning features and guided through
the light guide by total internal reflection. A light detector, for
example, a photodiode, may be disposed along one or more edges of
the light guide and may sense the ambient light gathered and guided
into the light guide by the light turning features. In other
embodiments, a light source, for example, one or more light
emitting diodes (LEDs) may also be disposed along one or more edges
of the light guide. The light emitted by the light source may be
guided through the light guide by total internal reflection and
extracted from the light guide by the light turning features. In
some embodiments, the light detector may be configured to detect
light that has entered the light guide. The detected light may be
ambient light that has entered the light guide, and/or light
emitted by the light source and extracted by the light turning
features that is later reflected back into the light guide. In some
embodiments, two differently configured sets of light turning
features can be disposed on the light panel surfaces (e.g.,
intermingled). One set of light turning features can be configured
to extract light from the panel, the other set to divert incident
(ambient) light into the light panel.
[0042] Turning now to FIG. 1, a light panel 101 is shown including
a light guide 105 and a light source 109. The light panel 101 is
configured to generate and emit light in one or more directions.
The light guide 105 is configured to receive light 103 generated
and emitted by the light source 109, propagate the light within the
light guide 105, and redirect the light 103 such that at least a
portion of the light 103 is emitted from the light panel 101 along
the one or more selected emission directions. The light guide 105
can utilize the property of total internal reflection ("TIR") and
optical characteristics of light turning features that are disposed
on a surface of the light guide 105 to direct and redirect light
from the light source 109 through the light guide 105 and to emit
light in the desired direction.
[0043] Still referring to FIG. 1, the light guide 105 may comprise
optically transmissive material that is substantially optically
transmissive to radiation at one or more wavelengths. For example,
in one embodiment, the light guide 105 may be substantially
optically transmissive to wavelengths in the visible and near
infra-red region. In other embodiments, the light guide 105 may be
transparent to certain wavelengths, for example, in the in the
ultra-violet or infra-red regions.
[0044] The light guide 105 may comprise a substantially optically
transmissive plate, sheet or film. The light guide 105 may be
planar or curved. The light guide 105 may be formed from rigid or
semi-rigid material such as glass or acrylic so as to provide
structural stability to the embodiment. In other embodiments, the
light guide 105 may be formed of flexible material such as a
flexible polymer. Other materials for example, PMMA, polycarbonate,
polyester, PET, cyclo-olefin polymer, or Zeonor may be used to form
the light guide 105 in several other embodiments. In other
embodiments, the light guide 105 may be formed of any material with
an index of refraction greater than 1.0. The thickness may, in some
embodiments, determine whether the light guide 105 is rigid or
flexible. The optical transmissive properties, and the materials,
of the light guide 105 can also be embodied on other light guides
described herein.
[0045] Still referring to the embodiment shown in FIG. 1, the light
guide 105 comprises two larger area surfaces and four smaller edge
surfaces. In some embodiments, an upper surface 109 may be
configured to emit light extracted by the light panel 101 or to
receive ambient light. In some embodiments, a bottom surface 111 of
the light guide may be connected to a substrate 107 and/or be
configured to emit light extracted from the light guide 105. In
various embodiments, the substrate 107 may be opaque, partially or
substantially completely optically transmissive, or transparent.
The substrate 107 may be rigid or flexible. The light guide 105 may
be connected to the substrate 105 using a low refractive index
adhesive layer (e.g., a pressure sensitive adhesive). Substrate 107
may comprise a diffuser. In certain embodiments, the substrate 107
may comprise a diffuser comprising an adhesive with particulates
therein for scattering, for example, a pressure-sensitive adhesive
with diffusing features. In some embodiments, the diffuser may also
be formed using holographic recording techniques. The light guide
105 may be bounded by a plurality of edges all around. In some
embodiments, the length and width of the light guide 105 is
substantially greater than the thickness of the light guide 105.
The thickness of the light guide 105 may be between 0.1 mm to 10
mm. The area of the light guide 105 may be between 1.0 cm.sup.2 to
10,000 cm.sup.2. However, dimensions outside these ranges are
possible. In other embodiments, the light panel 101 may comprise a
luminaire or a privacy screen.
[0046] Still referring to FIG. 1, the light guide 105 may be
coupled with a light source 109. In some embodiments, the light
guide 105 can be coupled with a light sensor (not shown). The light
source 109 may be disposed along one or more edges of the light
guide 105. The light source 109 may comprise any of a variety of
light source technologies including fluorescent lamps, incandescent
bulbs and/or LEDS. In some embodiments, the light source 109 may
comprise one or more of a plurality of localized light sources, for
example, one or more incandescent bulbs and/or LEDs and/or an array
of LEDs. In some embodiments, an optional reflector 113 will be
disposed near the light source 109 to direct the light emitted from
the light source in one or more desired directions. It will be
understood that depending on the particular implantation, an
appropriate source of power will be included to provide operating
power to the light source 109. Such power sources can include but
are not limited to batteries, photovoltaic cells, fuel cells,
generators, and/or an electrical power grid. It will also be
understood that the light panel 101 will generally be provided with
appropriate control circuitry which can include but need not
require switches, voltage control circuitry, current control
circuitry, ballast circuits, and the like. The power and control
components of the light panel 101 are not illustrated for clarity
and ease of understanding, however, appropriate power supply and
control circuitry components will be understood by one of ordinary
skill As shown in the embodiment of FIG. 1, light 103 may propagate
from the light source 109 through the light guide 105 and be
directed from the light guide 105 towards one or more
directions.
[0047] Turning now to FIG. 2, an enlarged side view of the light
panel 101 shown in FIG. 1 depicts a portion of the upper surface
201a of the light guide 105 and the bottom surface 201b of the
light guide 105. As shown in this embodiment, light 103 propagating
through the light guide 105 may be trapped within the light guide
105 by total internal reflection until it encounters light turning
features 203 formed in the upper surface 201a of the light guide
105. When the light 103 encounters a light turning feature 203,
some of the light 103 may be extracted from the light guide 105 and
turned towards the bottom surface 201b of the light guide 105. The
light turning features 203 may comprise any feature configured to
turn or extract light, for example, refractive features, dots,
grooves, pits, prismatic features, holograms, or diffractive
gratings. The light turning features 203 may be formed by a variety
of techniques such as embossing or etching. Other techniques of
forming the turning features may also be used. In some embodiments,
the turning features 203 may be formed or disposed on a film that
forms a part of the light guide 105 and is adhered to a surface of
the light guide 105 (e.g., by lamination). In certain embodiments,
the turning features 203 may also be disposed in or on the light
guide 105. In one embodiment, the light turning features 203
comprise a plurality of elongate ridge or prism structures
extending substantially across the upper surface 201a of the light
guide 105. In another embodiment, a light guide 105 may comprise
light turning features 203 on both sides and extract light from
within the light guide in both directions. In one embodiment, the
upper surface 201 comprises a plurality of microprisms extending
along the width of the light guide 105. The microprisms may be
configured to receive light propagating through the light guide 105
and turn light 103 through a large angle, for example, between
about 70-90.degree..
[0048] Turning now to FIG. 3, an embodiment of a light panel 101 is
shown. In this figure, light rays 103 may be extracted by light
extracting features (not shown) in the light guide 105 and then
reflected back through the light guide 105 by a reflective surface
111, for example, an interferometric modulator. As shown in FIG. 4,
some of the light 103b propagating through the light guide 105 may
"leak" through the upper surface 201a of the light guide 105 when
incident at certain grazing angles while another portion of the
light 103a propagating through the light guide 105 may be turned by
light turning features 203 formed on the upper surface 201a. Thus,
a portion of light 103a emitted by the light source may be directed
out of one side of the light guide 105 while another portion of
light 103b may be directed out of the other side of the light guide
105.
[0049] Referring to FIG. 3 again, the light panel 101 may also
include one or more light detectors (or sensors) 509. In various
embodiments, sensor 509 may be disposed along one or more edges of
the light guide 105. The sensor 509 is configured to detect light
103 that travels within the light guide 105 to the light detector
509. The sensor 509 may detect light 103a that is input into the
light guide 105 by the light source 109 and/or the sensor 509 may
detect light 103b that is incident on the top surface of the light
guide 105. Light 103b that is incident on the light guide 105 may
be ambient light and/or light emitted by the light source 109 that
is reflected back into the panel 101. The sensor 509 may be
configured to sense, for example, visible light waves or infra-red
waves. In one embodiment, the sensor 509 may comprise a
photodiode.
[0050] Turning now to FIG. 5, a light panel 101 configured to
detect light is shown including a light guide 105 and at least one
light detector (or sensor) 509. The light guide 105 may comprise
optically transmissive material that is substantially optically
transmissive to radiation at one or more wavelengths. The light
guide 105 may comprise two surfaces. In some embodiments, one of
the surfaces may be adhered to a substrate 107. The light guide 105
may include one or more light gathering features (not shown)
configured to receive light incident on the light guide 105 and
direct the light through the light guide 105. The light gathering
features can turn the angle of incident rays of light inside the
light guide 105 such that the ray of light 103 can be guided within
the light guide 105 by total internal reflection. In some
embodiments, the light gathering features may be embodied in a
microstructured thin film. In some embodiments, light gathering
features can be volume or surface diffractive features, or
holograms disposed on one or more surfaces of the light guide
105.
[0051] The thickness of the light gathering features may range from
approximately 1 .mu.m to approximately 100 .mu.m in some
embodiments but may be larger or smaller. In some embodiments, the
thickness of the light gathering features or layer may be between 5
.mu.m and 50 .mu.m. In some other embodiments, the thickness of the
light gathering features or layer may be between 1 .mu.m and 10
.mu.m. The light turning gathering feature may be attached to
surfaces of the light guide 105 by an adhesive. The adhesive may be
index matched with the material comprising the light guide 105. In
some embodiments, the adhesive may be index matched with the
material comprising the light gathering feature. In certain other
embodiments, light gathering features may be formed on the upper or
lower surfaces of the light guide 105 by embossing, molding, or
other process. Thus, the light guide 105 can be configured to
receive light incident on one or more surfaces of the light guide
from one or more directions, and direct the light through the light
guide to the sensor 509.
[0052] Still referring to FIG. 5, the volume or surface diffractive
elements or holograms can operate in transmission or reflection
mode. The transmission diffractive elements or holograms generally
comprise optically transmissive material and diffract light passing
there through. Reflection diffractive elements and holograms
generally comprise a reflective material and diffract light
reflected therefrom. In certain embodiments, the volume or surface
diffractive elements/holograms can be a hybrid of transmission and
reflection structures. The diffractive elements/holograms may
include rainbow holograms, computer-generated diffractive elements
or holograms, or other types of holograms or diffractive optical
elements. In some embodiments, reflection holograms may be
preferred over transmission holograms because reflection holograms
may be able to collect and guide white light better than
transmission holograms. In those embodiments, where a certain
degree of transparency is required, transmission holograms may be
used. Transmissive layers may also be useful in embodiments that
are designed to permit some light to pass through the light guide
to spatial regions beneath the light guide. The diffractive
elements or holograms may also reflect or transmit colors for
design or aesthetic purpose. In embodiments, wherein the light
guide is configured to transmit one or more colors for design or
aesthetic purposes, transmission holograms or rainbow holograms may
be used. In embodiments, wherein the light guide may be configured
to reflect one or more colors for design or aesthetic purposes,
reflection holograms or rainbow holograms may be used.
[0053] Still referring to FIG. 5, in some embodiments, the amount
of light collected and guided by a light guide 105 can be referred
to as the light collection efficiency of the light guide.
Therefore, light turning features disposed on the light guide 105
can increase the light collection efficiency of the light guide
105. At least a portion of the light collected by the light guide
105 propagates to one or more sensors 509 disposed at one or more
edges of the light guide. The sensors 509 may comprise detectors
capable of sensing light waves, for example, visible light waves or
infra-red waves. In one embodiment, the sensor 509 may comprise a
photodiode capable of converting light into electrical energy
(e.g., current or voltage) depending on the mode of operation of
the photodiode. The electrical output from the sensor 509 can
indicate a change in light falling onto the light guide 105, for
example, from a change in ambient light conditions, or from an
object positioned close enough to the light panel 101 to block
ambient light from its surface. In some embodiments, the electrical
output is a control signal used to trigger certain events,
including to turn on or increase the light panel output due to low
ambient light conditions, or to trigger another control event (for
example, closing or opening a switch). In other embodiments, the
sensor 509 can comprise control circuitry and the control circuitry
can use the electrical output to create one or more control
signals.
[0054] The embodiment illustrated in FIG. 5 also comprises a light
source 109. Some embodiments do not include such a light source and
instead sense only ambient light. The light source 109 may be
disposed along one or more edges of the light guide 105 and may be
configured to input light into the light guide 105. The light
source 109 may comprise any of a variety of light source
technologies including fluorescent lamps, incandescent bulbs and/or
LEDS. In some embodiments, the light source 109 may comprise one or
more of a plurality of localized light sources, for example, one or
more incandescent bulbs and/or LEDs and/or an array of LEDs.
[0055] Turning now to FIG. 6, the light panel 101 shown in FIG. 5
is depicted with an external light source 603 that may illuminate
the light panel 101. Light emitted from the external light source
603 may be gathered by light gathering features (not shown)
disposed on the surface of the panel 101 proximate to the light
source 603 and propagate through the light guide 105 to one or more
sensors 509. The external light source 603 may comprise ambient
light or another source of light, for example, an incandescent
light. A portion of the light emitted by the external light source
603 may be blocked by one or more objects 601 that lie between the
external light source 603 and the light sensing light panel 101.
For example, a hand, or similar object, may intercept light 103a
emitted by the external light source 603 and prevent the sensor 509
from detecting the light 103a while another portion of light 103b
emitted from the external light source 603 may be guided into the
light guide 105 and detected by the sensor 509. In such
embodiments, the light sensing light panel 101 may be used as a
control for a light source to determine how much light should be
emitted by the light source based on the amount of ambient light
received by the sensor 509. In other embodiments, a light sensing
light panel 101 may be used as a proximity sensor, a lighting
fixture, or an occupancy sensor. For example, a light sensing panel
101 may be used to turn on, turn off, or dim a light emitting panel
as the motion of an object, for example, a hand, across the light
sensing panel 101 leads to specific electrical signatures. In one
embodiment, the sensor 509 may be used to detect the amount of
light incident on the light panel 101 and control the amount of
light emitted by the light panel by the optional light source
109.
[0056] Turning now to FIG. 7, an embodiment of a light panel 701 is
depicted. The light panel 701 is configured to detect light and
includes a light guide 105 and two photodiodes 703a,b disposed
along two opposite edges of the light guide 105. The light guide
105 may comprise light gathering features (not shown) configured to
gather light received by the light guide 105 and turn the light
such that the light propagates through the light panel 105 to the
photodiodes 703a,b. For example, the light guide 105 may comprise
acrylic with light gathering dots printed upon the piece of
acrylic. The light gathering dots may comprise diffusive particles
configured to scatter light and turn the light into the light guide
105. The photodiodes 703a,b may be electrically connected such that
they may detect the motion, or location, of an object that is moved
across the light guide 105. Such embodiments are further described
in reference to FIGS. 8 and 9. For example, the photodiodes 703a,b
may be connected to form a differential amplifier. In one
embodiment, an object, for example, a hand, may move across the
light guide 105 from left to right in five positions 707a, 707b,
707c, 707d, and 707e with each position changing the amount of
light detected by each photodiode 703a,b.
[0057] Turning to FIG. 8, a diagram shows one example of an
electrical connection between two photodiodes 703a,b illustrated in
FIG. 7. The photodiodes 703a,b form a differential amplifier that
outputs an electrical signal indicating the difference in light
sensed by the two photodiodes 703a,b. The electrical signal output
by the differential amplifier can be received by another device
within a light panel and/or received by a device outside of the
light panel. For example, the photodiodes may be electrically
connected with a light source within a light panel and/or another
electrical device housed outside of the light panel. In some
embodiments, the photodiodes may be electrically connected with an
output terminal configured to electrically connect a light panel
with another device.
[0058] Turning now to FIG. 9, the output of the photodiodes 703a,b
shown in FIG. 7 is shown as an object is moved from position 707a
to 707e. Line 903a depicts the output of light sensed by photodiode
703a and line 903b depicts the output light sensed by photodiode
703b. When the object (e.g., the hand shown in FIG. 7) is in
position 707a, the light panel 701 is unobstructed by the object.
When the object is in position 707b, the object obstructs light
near photodiode 703a and photodiode 707a detects less light than
the other photodiode 703b. When the object is in position 707c, it
is equidistant from both of the photodiodes 703a,b and each
photodiode 703a,b detects the same amount of light. When the object
is in position 707d, it is closer to photodiode 703b and photodiode
703b detects less light than the other photodiode 703a. Lastly,
when the object is in position 707e, it does not obstruct the light
panel 701 and each photodiode 703a,b detects the same amount of
light. By connecting the photodiodes as shown in FIG. 8, the
sequencing of positive and negative voltage pulses output by the
photodiodes may indicate the direction of motion and can be used as
a control mechanism. For example, an object moving from left to
right over panel 101 may be used as a signal to turn a light
emitting panel off or dim the panel. In another example, an object
moving from right to left over a panel 101 may be used as a signal
to turn a light emitting panel on or increase the amount of light
emitted. In other embodiments, a constant obstruction over a
particular part of the panel may trigger an event. For example,
holding a hand over panel 101 in position 707a may turn something
on or off. Additionally, the distance of an object, for example, a
hand, from the panel 101 may further affect the outputs of the
photodiodes 703a,b and be used as a control mechanism. The
photodiodes 703a,b may be configured to detect various wavelengths
of light. For example, in one embodiment the photodiodes 703a,b may
be configured to detect visible light and in another embodiment the
photodiodes may be configured to detect waves in the infra-red. In
other embodiments, more photodiodes may be disposed along the light
guide in order to increase the sensitivity of the light panel.
[0059] Turning now to FIG. 10, a light panel 1010 configured to
emit and/or detect light is shown. The light emitting and light
sensing panel 1010 includes a light guide 105. The light guide 105
may comprise optically transmissive material that is substantially
optically transmissive to radiation at one or more wavelengths. A
light source 109 is disposed along at least one edge of the light
guide 105 and is configured to input light 103 into the light guide
105. The light 103 travelling within the light guide 105 may be
trapped by total internal reflection until it reaches a turning
feature 1012. Turning feature 1012 may be formed on the light guide
105 and may be configured to turn and direct light 103 out of the
light guide 105 in one or more particular directions. The light
panel 101 may also include a light detector 509 disposed along at
least one edge of the light guide 105. The light detector 509 may
be configured to detect light travelling in one or more directions
towards the light detector. In one embodiment, the light detector
509 is configured to detect light 103 directed by turning feature
1012. The light detector 509 may be configured to act as a control
mechanism to control something based on the amount of light
detected. For example, the light detector 509 may be configured to
act as a switch that turns a device off or on depending on whether
light is detected. In one example, an object 601, for example, a
hand, may be used to obstruct light 103 directed toward the light
detector 509 by light turning feature 1012. When the object 601
obstructs the light directed to the light detector 509, the light
detector 509 may detect less light and perform some control
function.
[0060] Turning now to FIG. 11, a light panel 1111 configured to
emit and/or detect light is shown. The light panel 1111 includes an
optically transparent light guide 105. The light guide 105 may
comprise optically transmissive material that is substantially
optically transmissive to radiation at one or more wavelengths. A
light source 109 is disposed along at least one edge of the light
guide 105 and is configured to input light 103b into the light
guide 105. A light detector (or sensor) 509 is also disposed along
at least one edge of the light guide and is configured to detect
light 103a that travels within the light guide 105 to the light
detector 509. The light guide 105 may include a plurality of light
turning features (not shown) and light gathering features (not
shown). The light turning features may be configured to extract
light 103b from within the light guide 105 and direct the light
towards one or more particular directions. The light guide 105 may
comprise light turning features on one or more sides and the light
turning features may comprise any feature configured to turn or
extract light, for example, refractive features, dots, grooves,
pits, prismatic features, holograms, or diffractive gratings. The
light guide 105 may also include one or more light gathering
features (not shown) configured to receive light 103a incident on
the light guide 105 and direct the light 105a through the light
guide 105 toward the light detector 509. The light gathering
features can turn the angle of incident rays of light 103a inside
the light guide 105 such that the light can be bound within the
light guide 105 by total internal reflection. In some embodiments,
the light gathering features may be a micro structured thin film,
volume or surface diffractive features, or holograms.
[0061] Still referring to FIG. 11, the light emitting and light
sensing panel 1111 can be configured to simultaneously emit light
from one or more sides of light guide 105 and detect light received
by one or more sides of light guide 105. The light detector may be
configured as a control mechanism to control the amount of light
103b emitted from the light source 109. For example, if the light
detector 509 detects a threshold amount of ambient light, the light
detector may turn the light source 109 off or dim the light source
109. In another example, if the light detector 509 does not detect
a threshold amount of ambient light, the light detector 509 may
increase the amount of light emitted by the light source 109. In
another example, the light detector 509 may be configured to detect
infra-red light and be configured as an occupancy sensor. In this
example, the light detector 509 may turn the light source 109 on
when infra-red light is detected and may turn the light source 109
off when infra-red light is not detected. As previously discussed
with respect to FIGS. 7-9, a light sensing panel may be configured
to detect a certain motion or location of an obstruction. The light
emitting and light sensing panel 1111 depicted in FIG. 11 can also
be configured to detect the location of a source of light gathered
by the light guide 105 and/or to detect a certain motion of an
object that comes between the light guide 105 and an external light
source. In one embodiment, the light panel 1111 may be configured
to emit light and detect ambient light or emitted light that is
reflected back towards the light guide 105. For example, the light
panel may be configured to emit a certain amount of light and the
light detector may be configured to detect when an object 601 is
placed near the light guide 105 based on the amount of emitted
light that is reflected by the object 601 back towards the light
guide 105. Additionally, in other embodiments, the light emitting
and light sensing panel 1111 can detect light received on either
side of the light guide 105 while simultaneously emitting light
from one or both of these sides.
[0062] FIG. 12 illustrates a top schematic view of an embodiment of
a light panel 1212 showing one type of light turning or gathering
feature. In this example, the light panel 1212 may be configured to
emit and/or gather light. The light panel 1212 includes features
1201. Features 1201 may be configured to extract light from within
the light guide 105 or to gather light incident upon the light
guide 105 and direct the light into the light guide 105. The
features 1201 may be embossed or machines into light guide 105. The
light sources 109 may comprise LEDs or any other suitable light
source including linear light sources. Additionally, optional light
detectors 509 may be disposed along one or more edges of the light
guide 105. The light detectors 509 may be configured to detect the
light that travels within the light guide 105 to the light
detectors 509 and may be used to control the amount of light
emitted by the light sources 109, among other things. For example,
the light detectors 509 may be used to detect the amount of light
that is incident on the light panel 1212 and trigger an event if
the amount of light detected is more or less than certain threshold
values. As shown in the embodiment of FIG. 13, light may propagate
from the light sources 109 through the light guide 105 by total
internal reflection until it encounters light a light turning
feature 1212. When the light encounters light turning features
1212, some of the light may be extracted from the light guide 105
and be turned towards the front (or back) planar side making the
light panel 1212 appear bright to a viewer. The light panel 1212
may also include light gathering features (not shown) configured to
direct light incident on the light guide 105 towards the light
detector 509.
[0063] Turning now to FIG. 14, a light panel 1414 is depicted. In
this example, the light panel 1414 may be configured to emit and/or
gather light. The light panel 1414 includes printed light
extraction dots. Dots 1401 may be printed upon the front, back, or
both front and back surfaces of the light guide 105 to extract
light input into the light guide 105 by light source 109 or to
gather light incident on the light guide. Printed dots 1401 can be
used to tailor the transparency and diffusion of the panel when in
ambient light, un-illuminated by a light source 109. Additionally,
dots 1401 can be used to create uniform or non-uniform light
extraction, with light output on the front, back, or both sides of
the light guide 105. When the light guide 105 is illuminated by
light sources 109, the dots 1401 can be used to direct light toward
a viewer. In some embodiments, the dots 1401 may comprise, for
example, diffusive particles or opaque materials, and be configured
thicker or with higher density to limit light transmission through
the panel. In one embodiment, some dots 1401 may be configured to
emit light input into the light guide 105 by the light sources 109
while other dots 1401 may be configured to gather light incident on
the light guide 105 and direct the light through the light guide
towards one or more light detectors 509. Thus, the light panel 1414
may be used as a light emitting and/or light sensing panel.
[0064] Turning now to FIG. 15, printed dots 1401 used as an
alternative to machined/embossed features offer a low cost,
flexible design (e.g., controllable efficiency and uniformity), and
flexibility of light guide 105 material (e.g., dots can be used on
many substrates including glass and plastic). Additionally, the
dots 1401 can be simple to manufacture, may require a relatively
low capital expenditure to manufacture, and are highly
configurable. For example, the dots 1401 may be printed onto the
light guide 105 by an ink jet printer, screen printing techniques,
or any other ink printer. The dots may also be rolled, splattered,
or sprayed onto the light guide 105.
[0065] Turning now to FIG. 16, one embodiment of a large area light
panel is depicted. Large area light panels can be optimized for the
required lighting performance. For example, certain light
extracting features can be selected to be disposed on either a
front surface, a back surface, or both. Also, light sources of
different wavelengths can be used. Such optimized configurations
can also include light detectors having different sensitivities
(e.g., to different light of wavelengths, or intensity). Light
turning features may be used to extract light that was injected
into the panel edges, out of the panel for illumination. The light
turning features can naturally operate in a reciprocal mode to turn
light incident on the panel into the panel where it can propagate
by total internal reflection (TIR) toward sensors coupled to the
light guide such that they receive a portion of the light
propagating within the light guide, allowing the panel to operate
as a dual mode device (emitter/sensor), or if a light source is
omitted, as a sensor only. Some applications of a large area light
panel may require the sensing performance to be optimized in a
different way than the lighting functionality. For example, a panel
may be configured to sense infra-red waves and emit visible light.
In another example, a light panel may be configured as a broad,
uniform light panel with infra-red occupancy sensing in one or more
directions only. In another example, a light panel may be
configured to provide uniform lighting while sensing may be limited
to a small area of the panel, for example, for control purposes. In
such examples, light detectors and sensors can be selected that are
operable for different wavelengths (or frequencies) of light, such
that the light emitting functionality has a minimal (or no) impact
on the sensing functionality.
[0066] Still referring to FIG. 16, one embodiment of a large area
light panel includes a light guide 105. Disposed along one or more
edges of the light guide 105 may be one or more light detector (or
sensor) 509 and one or more light source 109. The light gathering
features may be configured to direct light incident on the light
guide 105 into the light guide 105 and towards the light detector
509. The light gathering features 2002 may be optimized for light
detecting or sensing. Also, light turning features 2001 may be
disposed on more or more surface of the light guide 105. The light
turning features may be configured to extract light that is input
into the light guide 105 by the light source 109 from the light
guide 109 towards one or more directions. The light turning
features 2001 can comprise prismatic facets, printed dots,
diffractive (e.g., holographic features), etc. The light turning
features 2001 can have wavelength spectrum selectivity. For
example, some infra-red light used for sensing may be scattered at
the surface of the light guide 105, but at least some of the light
will enter the light guide and propagate via TIR to the light
detector 509. For improved detecting, in some embodiments, light
turning features can be made less sensitive to the wavelengths used
for sensing. In some embodiments, light gathering features 2002 are
configured to not interact with visible light wavelengths and may
be optimized for sensing particular wavelengths (e.g., infra-red).
For example, a holographic film may be laminated to the panel. A
holographic film may be customized to turn incident light into the
panel, selecting only certain wavelengths or with specific
directionality. In one example, a film could be bonded to the panel
using a pressure sensitive adhesive of higher or equal index to the
film. An optional substrate 107, for example a reflector, may be
disposed near the light panel and configured to obstruct light
emitted from the light panel or reflect light emitted from the
light panel back towards the light guide 105.
[0067] Turning now to FIG. 17, the large area light panel depicted
in FIG. 16 is shown without the optional reflector. Arrows show the
relative sensitivity of film designed to turn light into the light
guide 105 and toward the light detector (or sensor) 509 from one
particular direction.
[0068] Turning now to FIG. 18, an embodiment of a light panel is
depicted. The light panel includes a light guide 105. Light turning
features 2001 can be disposed on a portion of a planar surface on
one side to the light guide 105 (e.g., a small portion), and light
gathering features 2002 can be disposed on a portion of the
opposite planar surface of the light guide 105 (e.g., a small
portion). The light turning features 2001 (behind the sensor film)
can be modified to indicate where this area is by extracting a
light having a certain color or brightness.
[0069] Turning now to FIG. 19, an embodiment of a light panel is
shown. The light panel includes two light guides 105 separated by a
low refractive index (N) layer 2301. Each light guide 105 may have
a higher refractive index than the low refractive index layer 2301.
A light source 109 may be disposed along one or more edges of one
or both of the light guides 105 and a light detector 509 may be
disposed along one or more edges of one or both of the light guides
105. Thus, a dual sided panel can be designed with features
optimized for light emitting on one surface and light detecting on
the other. Some interaction may occur between the light detecting
and light emitting features of the light panel depicted in FIG. 16.
However, it may be desirable to limit the interaction of the
detecting and light emitting turning features, especially with
simple techniques where reciprocal behavior is likely, for example,
with printed dots.
[0070] The light guide material may comprise a substrate, for
example, acrylic, glass, polyethylene terephthalate (PET), or
PET-G. In one example, a large area light guide (such as
4.times.8') may be approximately 0.25'' thick. Two such light
guides could be bonded together with a lower refractive index
isolation later between the two. In this example, light may
propagate from TIR within each light guide 105 but light trapped in
either light guide by TIR cannot cross into the other light guide
105. Light collected and gathered for detecting will be less
subject to scattering by lighting turning features and vice versa.
In one embodiment, a low index isolation layer 2301 is a low index
adhesive. In other embodiment, light turning features 2001 and
light gathering features 2002 do not cover identical areas (e.g.,
sensing panel where turning features could be limited to a small
area, or areas, of a light guide 105). In one example, the
materials of each light guide 105 and thicknesses could be
different with each light guide 105 having a higher refractive
index than the low index isolation layer 2301.
[0071] Turning now to FIG. 20, an embodiment of a light panel
configured to emit and detect light is shown. The light panel
includes a light guide 105 with printed ink dots 1401 printed on
one or more surfaces of the light guide 105. Light sensors 109 and
light detectors 509 may be disposed along one or more edges of the
light guide 105. A light panel, for example, the light panel
depicted in FIG. 20, can be used to sense the presence of or
variations in ambient radiation (e.g., ambient visible light coming
from natural or other illumination sources incident on the light
guide 105). In one example, a light panel may be configured to
sense natural solar or body heat infra-red waves, or variations in
infra-red waves from other sources of heat in a room that may be
caused by movement of objects or people (passive infra-red
sensing). In another embodiment, a light panel may be designed to
emit light in one set of wavelengths while detecting light in
another set of wavelengths to avoid swamping the detectors 509
coupled to the same light guide 105 as the light sources 109.
Visible or near infra-red wavelength detectors 509 may be made from
silicon. Material commonly used in passive infra-red sensing
include gallium nitride, caesium nitrate, polyvinyl fluorides,
derivatives of phenylprazine, cobalt phthalocyanine, and lithium
tantalite. In one example, the panel may be designed to sense light
emitted by the panel and reflected back to the light guide. In one
example, detectors 509 may be designed with sufficient dynamic
range so they are not swamped by light directly coupled from the
light sources 109. In another example, detectors 509 may be placed
to minimize coupling, or light extraction features designed for
minimum direct sensor illumination. The printed dots 1401 may be
designed to avoid back scatter of illumination light directly back
toward a detector 509. Prismatic features or other light turning
features may also be used. The detectors 509 may be placed on the
same edge(s) as the light sources 109 so the light cone of the
light sources 109 does not directly illuminate the detectors
509.
[0072] Turning now to FIG. 21, an embodiment of a light panel
configured to emit and detect light is shown. In some examples,
ambient light sensing may be desired but detectors 509 may be
potentially swamped by light source 109 output. This may be
important where the sensing is being used to sense the room
lighting state for automatic control of the light (e.g., sensing
the onset of darkness).
[0073] Turning now to FIG. 22, pulse width modulation (PWM) may be
used to provide "breaks" in light output that can be used for
sensing or detecting light (e.g., with LED light sources which have
a steep electrical input to light output response curve). PWM can
be used for LED light dimming where a high frequency pulsed light
output is integrated by the eye to create the impression of a
steady illumination level defined by the LED duty cycle. Pulse
repetition rates of greater than approximately 60 Hz or breaks in
illumination of about less than 20 ms may not be detectable by the
human eye.
[0074] Turning now to FIG. 23, PWM of LED light sources can be used
for light dimming, or to provide breaks in light output for ambient
light sensing. The same system can be used for the remote control
of light panels. The light output of one panel can be PW or
amplitude modulated at high frequency (10s to 1000s of Hz) which is
undetectable by the eye, but detectable by a detector in a light
panel to carry control information. Some advantages are daisy
chaining of light control without the need for dedicated control
circuits, common light source for lighting and remote control is
possible (though not essential), and reuse of control sensor for
remote control.
[0075] In one example, in a room, one panel may be designated as a
master and the others as slaves, set to receive some form of serial
data from the master, which could be used to set, for example,
on/off state, brightness, and color. With an appropriate code,
slave devices ("slaves") could also be addressable as groups or
individually. In the master/slave control example depicted in FIG.
23, the master can include a periodic PWM data burst in LED output.
In one mode, the slave synchronizes an LED off period with the data
burst to allow for data (and ambient) sensing. Initial slave signal
acquisition is possible by known techniques including: 1) start
master first, slaves LEDs initially in off state, until data
detected; 2) slave unsynchronized periodic LED off period
repetition rate is set to be higher than synchronized rate, so
slave will eventually detect and sync to master data bursts. In
other examples, asynchronous slave operation is also possible by
providing regular slave LED off/sensing periods where the sensor
can listen for a random data burst.
[0076] The foregoing description details certain embodiments of the
invention. It will be appreciated, however, that no matter how
detailed the foregoing appears in text, the invention can be
practiced in many ways. As is also stated above, it should be noted
that the use of particular terminology when describing certain
features or aspects of the invention should not be taken to imply
that the terminology is being re-defined herein to be restricted to
including any specific characteristics of the features or aspects
of the invention with which that terminology is associated. The
scope of the invention should therefore be construed in accordance
with the appended claims and any equivalents thereof.
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