U.S. patent application number 14/364339 was filed with the patent office on 2014-11-06 for window having active transparency control.
The applicant listed for this patent is KiloLambda Technologies Ltd.. Invention is credited to Ariela Donval, Noam Gross, Doron Nevo, Moshe Oron.
Application Number | 20140327949 14/364339 |
Document ID | / |
Family ID | 48698726 |
Filed Date | 2014-11-06 |
United States Patent
Application |
20140327949 |
Kind Code |
A1 |
Gross; Noam ; et
al. |
November 6, 2014 |
Window Having Active Transparency Control
Abstract
An active, transparency-controlled window comprises at least one
layer of a material that is transparent to at least selected
wavelengths of light; at least one layer of photochromic material
having a transparency, to the at least selected wavelengths of
light, that can be controllably altered by an activating light; and
a controllable source of light that activates the photochromic
material to controllably alter the transparency of the photochromic
material to the at least selected wavelengths of light. The
material that is transparent to at least selected wavelengths of
light may be a material selected from the group consisting of glass
and plastic.
Inventors: |
Gross; Noam; (Kiryat Ono,
IL) ; Donval; Ariela; (Rosh Haayin, IL) ;
Nevo; Doron; (Ra'anana, IL) ; Oron; Moshe;
(Rehovot, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KiloLambda Technologies Ltd. |
Tel Aviv |
|
IL |
|
|
Family ID: |
48698726 |
Appl. No.: |
14/364339 |
Filed: |
December 17, 2012 |
PCT Filed: |
December 17, 2012 |
PCT NO: |
PCT/IB2012/057400 |
371 Date: |
June 11, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61581509 |
Dec 29, 2011 |
|
|
|
61654133 |
Jun 1, 2012 |
|
|
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Current U.S.
Class: |
359/244 |
Current CPC
Class: |
G02F 1/0126 20130101;
G02B 5/23 20130101; G02F 1/0121 20130101; E06B 7/28 20130101; E06B
2009/2464 20130101; E06B 9/24 20130101 |
Class at
Publication: |
359/244 |
International
Class: |
G02F 1/01 20060101
G02F001/01; E06B 7/28 20060101 E06B007/28 |
Claims
1. An active, transparency-controlled window comprising at least
one layer of a material that is transparent to at least selected
wavelengths of light, at least one layer of photochromic material
having a transparency, to said at least selected wavelengths of
light, that can be controllably altered by an activating light, and
a controllable source of light that activates said photochromic
material to controllably alter the transparency of said
photochromic material to said at least selected wavelengths of
light.
2. The active, transparency-controlled window of claim 1 in which
said material that is transparent to at least selected wavelengths
of light is made of a material selected from the group consisting
of glass and plastic.
3. The active, transparency-controlled window of claim 1 in which
said controllable light source directs light into said photochromic
material, and alters the transparency of said window by altering
the transparency of said at least one layer of photochromic
material by adjusting the strength of said light directed into said
photochromic material.
4. The active, transparency-controlled window of claim 1 in which
said controllable light source directs light into said photochromic
material through at least one edge of said window.
5. The active, transparency-controlled window of claim 1 in which
said photochromic material is sandwiched between two layers of said
material that is transparent to at least selected wavelengths of
light.
6. The active, transparency-controlled window of claim 5 in which
said two layers of said material that is transparent to at least
selected wavelengths of light include dedicated coatings to provide
a waveguide for said activating light, to protect an observer's
eyes from said activating light.
7. The active, transparency-controlled window of claim 5 in which
said two layers of said material that is transparent to at least
selected wavelengths of light have indices of refraction that are
(1) substantially the same as or lower than the index of refraction
of said photochromic material, and (2) higher than the ambient
environment of said window, to provide a waveguide for said
activating light and efficient penetration of said activating light
into said photochromic material.
8. The active, transparency-controlled window of claim 1 in which
said photochromic material is activatable by light within a
predetermined range of wavelengths, and said controllable light
source produces light having a wavelength within said predetermined
range.
9. The active, transparency-controlled window of claim 8 in which
said predetermined range of wavelengths is in the ultraviolet
region of the spectrum or in the 400 to 500 nanometer wavelength
region.
10. The active, transparency-controlled window of claim 1 in which
said controllable light source includes at least one light emitting
diode or diode laser.
11. The active, transparency-controlled window of claim 10 in which
said controllable light source includes at least one lens or lens
array to provide the light source with a prescribed divergence
angle.
12. The active, transparency-controlled window of claim 10 in which
said controllable light source includes at least one
single-optical-fiber or multiple-optical-fiber device.
13. The active, transparency-controlled window of claim 1 in which
said photochromic material is coated or glued to a glass layer that
serves as waveguide for said activating light.
14. The active, transparency-controlled window of claim 13 in which
said glass layer is tapered to provide substantially even
illumination of said layer of photochromic material.
15. The active, transparency-controlled window of claim 1 in which
the amount of said photochromic material is graded with a
concentration that increases with the distance from said light
source, to provide a substantially uniform reduction of impinging
light across the window.
16. The active, transparency-controlled window of claim 1 in which
said at least one layer of photochromic material includes multiple
layers of photochromic material having different colors and
separated by glass layers that serve as waveguides to filter out of
part of the spectrum.
17. The active, transparency-controlled window of claim 1 in which
said controllable light source is controlled to produce a
preselected opacity level from the combined activation of said
photochromic material by (1) ambient light and (2) light from said
controllable light source.
18. The active, transparency-controlled window of claim 1 in which
said photochromic material is covered on one side with a layer of a
material that blocks said activating light so that said
photochromic material remains transparent when activating light
arrives from said one side, and changes transparency when
activating light arrives from the opposite side.
19. The active, transparency-controlled window of claim 18 in which
said photochromic material becomes substantially opaque when
activating light arrives from said opposite side.
Description
RELATED APPLICATIONS
[0001] This application is related to U.S. Provisional Application
No. 61/581,509, filed Dec. 29, 2011, and U.S. Provisional
Application No. 61/654,133, filed Jun. 1, 2012, which is hereby
incorporated by reference herein in its entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to active transparency control
of a window, and more particularly, to the control of transparency
using controlled light activation of photochromic materials
embedded in the window material and to a method for controlling the
light activation of photochromic materials embedded in window
materials. The photochromic materials in the window change the
light transmission of the transparent window when exposed to
controlled activating light.
BACKGROUND OF THE INVENTION
[0003] Window panes with adjustable transparency are a known
product. For example, see U.S. Pat. No. 6,674,419, U.S. Pat. No.
6,597,412, U.S. Pat. No. 6,522,446, U.S. Pat. No. 6,606,185, U.S.
Pat. No. 6,301,040, EP 0 608 203 B1, and Document BINE 1/02,
published by the Technical Information Center Karlsruhe,
Gesellschaft fur wissenschaftlich-technische Information mbH, as
well as the Internet site www.smartglass.com. Window panes with an
adjustable transparency can be obtained, for example, from FLABEG
GmbH & Co. KG, Siemenstrasse 3, 90766 Furth, Germany, or
GESIMAT GmbH, Gesellschaft fur intelligente Materialien and
Technologien, Innovationspark Wuhlheide, Kopenicker Strasse 325,
12555 Berlin, Germany.
[0004] Another example is the electrochromic automatic-dimming rear
view mirror of Gentex, http://www.gentex.com/, which detects and
eliminates dangerous rearview mirror glare.
[0005] All the above use either electro-chromic materials or liquid
crystals serving as the active material, and their activation is
carried out by electric voltage, applied across the active material
through transparent electrodes.
[0006] There is a constant need for simpler active transparency
control of windows, mainly for display showcases, vehicle front
windows, sun protectors and regulated sun glasses.
SUMMARY OF THE INVENTION
[0007] It is therefore a broad object of the present invention to
provide active transparency control of a window, and more
particularly, to control the transparency by light activation of
photochromic materials embedded in the window material. The
photochromic materials in the window change the light transmission
of the transparent window, e.g., in the visible and/or infra-red
part of the spectrum, when exposed to controlled activating light.
That is, the light activation of the photochromic material is
controlled to change the light transmission of the transparent
window. This active transparency control of the window offers the
following advantages and properties: [0008] 1. Since the effect of
the photochromic material is controlled by illuminating the window
with a controllable beam of activating light, there is no need for
electrical electrodes or transparent conducting coatings on the
window pane. [0009] 2. There is no limitation on the geometrical
shape of the window. [0010] 3. A large change of transparency can
be achieved by using photochromic materials rather than
electro-chromic materials. [0011] 4. The activating light can
impinge on the window through light guides and fiber optics,
enabling low-volume, low-weight windows. [0012] 5. The amount of
activating tight can be precisely controlled and adjusted in small
increments to allow for the selection of intermediate states of
light transmittance.
[0013] Some uses for the active transparency control of a window
are in display showcases, vehicle front windows, sun protectors and
regulated sunglasses or sun shields.
[0014] In one embodiment, the active, transparency-controlled
window comprises at least one layer of a material that is
transparent to at least selected wavelengths of light; at least one
layer of photochromic material having a transparency, to the at
least selected wavelengths of light, that can be controllably
altered by an activating light; and a controllable source of light
that activates the photochromic material to controllably alter the
transparency of the photochromic material to the at least selected
wavelengths of light. The material that is transparent to at least
selected wavelengths of light may be a material selected from the
group consisting of glass and plastic.
[0015] In one implementation, the controllable light source directs
light into the photochromic material, and alters the transparency
of the window by altering the transparency of the photochromic
material by adjusting the strength of the light directed into the
photochromic material. The photochromic material is activatable by
light within a predetermined range of wavelengths, and the
controllable light source produces light having a wavelength within
that predetermined range. The predetermined range of wavelengths
may be in the ultraviolet region of the spectrum or in the 400 to
500 nanometer wavelength range. The light source may be controlled
to produce a preselected opacity level from the combined activation
of the photochromic material by (1) ambient light and (2) light
from the controllable light source. The controllable light source
may direct light into the photochromic material through at least
one of the narrow edges of the window.
[0016] In one embodiment, the photochromic material is sandwiched
between two layers of glass or plastic that are coated on their
opposed surfaces to provide a waveguide for the activating light.
This protects an observer's eyes from the activating light. The two
layers of glass or plastic may have indices of refraction that are
(1) substantially the same as or lower than the index of refraction
of the photochromic material, and (2) higher than the index of
refraction of the ambient environment of the window, to provide a
waveguide for the activating light and efficient penetration of the
activating light into the photochromic material.
[0017] In one embodiment, the photochromic material is sandwiched
between two layers of glass or plastic where one glass or plastic
is coated to provide a blocking surface for the activating light.
The activating light and the regular light come from the same
source, e.g. solar light, and the response of the device depends on
the direction of the incoming light. In case the activating light
engages the blocking surface before impinging on the photochromic
material, the window will stay transparent. In case the activating
light engages the photochromic material before impinging on the
blocking surface, the window will turn dark and will transmit only
a small amount of light. This window acts like a light diode for
the impinging light that contains the activating light; fully
transparent for light coming from one direction and nearly opaque
for light coming from the opposite direction.
[0018] The controllable light source may include at least one light
emitting diode or diode laser, at least one lens or lens array to
provide the light source with a prescribed divergence angle, and/or
at least one single-optical-fiber or multiple-optical-fiber
device.
[0019] The photochromic material may be coated or glued to a glass
or plastic layer that serves as waveguide for the activating light.
The glass or plastic layer may be tapered to provide substantially
even illumination of the layer of photochromic material. The amount
of the photochromic material may be graded to provide a
concentration that increases with the distance from the light
source, to provide a substantially uniform reduction of impinging
light across the window. The photochromic material may include
multiple layers having different colors and separated by glass or
plastic layers that serve as waveguides to filter out of part of
the spectrum.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The invention will be better understood from the following
description of preferred embodiments together with reference to the
accompanying drawings, in which:
[0021] In the drawings:
[0022] FIG. 1 is a schematic view of an active transparency
controlled window using a photochromic material layer sandwiched
between two glass layers.
[0023] FIG. 2 is a diagram of an active transparency controlled
window using a photochromic material layer sandwiched between two
glass layers, where dedicated coatings provide a waveguide for the
light.
[0024] FIG. 3 is a diagram of an active transparency controlled
window using a photochromic material layer sandwiched between two
glass layers where one or the two glass layer serves as a waveguide
for light that activates the photochromic material.
[0025] FIG. 4 is a diagram of an active transparency controlled
window using a photochromic material, having two layers of
reflecting coating on its two sides.
[0026] FIG. 5 is a diagram of light source arrangements for an
active transparency controlled window (a) using direct
light-emitting diodes or diode lasers, and (b) using fiber optics
delivery of light-emitting diodes or diode lasers.
[0027] FIG. 6 is a diagram of an active transparency controlled
window using a photochromic material layer coated or glued to a
glass layer, where the glass layer serves as a waveguide.
[0028] FIG. 7 is a diagram of an active transparency controlled
window using a photochromic material layer coated or glued to a
tapered glass layer, where the glass layer serves as waveguide, and
the tapering provides even illumination of the photochromic
material layer.
[0029] FIG. 8 is a diagram of an active transparency controlled
window using multiple photochromic material layers separated by
glass layers, where the glass layers serve as waveguides, enabling
the filtration out of part of the spectrum, using a single or more
than one activated filter.
[0030] FIG. 9 is a diagram of an active transparency controlled
window using a graded photochromic material layer.
[0031] FIG. 10 is a photograph of a photochromic material layer,
sandwiched between two glass layers, and partially activated by a
light source located on one side (similar to FIG. 3).
[0032] FIG. 11 is a diagram of an active transparency controlled
window having a photochromic material layer and a blocker for the
activating light, acting as a "light diode" that is transparent in
one direction and nearly opaque in the opposite direction.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0033] Although the invention will be described in connection with
certain preferred embodiments, it will be understood that the
invention is not limited to those particular embodiments. On the
contrary, the invention is intended to cover all alternatives,
modifications, and equivalent arrangements as may be included
within the spirit and scope of the invention as defined by the
appended claims.
[0034] FIG. 1 is a schematic view of an active transparency
controlled window 2 using a photochromic material layer 10
sandwiched between two layers 8 of a material, e.g., glass or
plastic, that is transparent to at least selected wavelengths of
light. The photochromic material layer 10 is activated by a
controllable light source 12, and the optical transparency of the
window 2 is controlled by the amount of active material in the
layer 10 and the strength of the activating light 12. Regular,
visible or infrared light 4 impinging on the window 2 is reduced in
intensity while transmitted through the window 2 and exits as
reduced light energy 6, where part of the impinging light 4 is
absorbed in the activated photochromic layer 10. The transparency
of the photochromic layer 10 is controllably altered by the
activating light, which permits use of the controllable light
source 12 to alter the transparency of the window by adjusting the
strength of the light directed into the photochroic material. The
activating light 12 may be in the ultra violet region of the
spectrum or in the 400 to 500 nanometer wavelength region, to match
the activation wavelength of photochromic material layer 10.
[0035] FIG. 2 is a schematic view of an active transparency
controlled window 18 using a photochromic material layer 10
sandwiched between two layers 8 of a material, e.g., glass or
plastic, that is transparent to at least selected wavelengths of
light, where dedicated coatings 14 provide a waveguide for the
activating light 12. The coatings 14 have indices of refraction
that are (1) substantially the same as or lower than the index of
refraction of the photochromic material, and (2) higher than the
ambient environment of said window, to provide a waveguide for the
activating light and efficient penetration of the activating light
the said photochromic material.
[0036] The optical transparency of the window 18 is controlled by
the amount of active material in the layer 10 and the strength of
the activating light 12. Regular, visible or infrared light 4
impinging on the window 18 is reduced in intensity while
transmitted through window 18 and exits as reduced light energy 6,
where part of the impinging light 4 is absorbed in the activated
layer 10. The transparency of the photochromic layer 10 is
controllably altered by the activating light, which permits use of
the controllable light source 12 to alter the transparency of the
window by adjusting the strength of the light directed into the
photochromic material. The photochromic material is activatable by
light within a predetermined range of wavelengths, and the
controllable light source produces light having a wavelength within
that predetermined range. The two layers 14 are transparent for
light 4, but reflective for activating light 12, e.g., when
impinging at small grazing angles, as shown by light beam 16. The
light 12 may be in the ultra violet region of the spectrum or in
the 400 to 500 nanometer wavelength region, to match the activation
wavelength of photochromic material layer 10. The inclusion of
material 10 between the two reflecting layers 14 for the activating
light 12 serves as a shield to the eyes of a person looking through
the window 18 against the possible irritation or damage by ultra
violet light.
[0037] FIG. 3 is a schematic view of an active transparency
controlled window 22 using a photochromic material layer 10
sandwiched between two layers 8 and 9 of a material, e.g., glass or
plastic, that is transparent to at least selected wavelengths of
light, where either one or both of the layers 8 and 9 serve as
waveguides. In FIG. 3, the glass layer 9 provides a waveguide for
the activating light 12 where part of the light 13 penetrates the
photochromic material layer 10 from the layer 9. The optical
transparency of the window 22 is controlled by the amount of active
material in the layer 10 and the strength of the activating light
12. Regular, visible or infrared light 4 impinging on the window 22
is reduced in intensity while transmitted through the window 22 and
exits as reduced light energy 6, where part of the impinging light
4 is absorbed in the activated layer 10. The transparency of the
photochromic layer 10 is controllably altered by the activating
light, which permits use of the controllable light source 12 to
alter the transparency of the window by adjusting the strength of
the light directed into the photochromic material. The photochromic
material is activatable by light within a predetermined range of
wavelengths, and the controllable light source produces light
having a wavelength within that predetermined range. The two layers
8 and 9 are transparent for the light 4, but reflective for the
activating light 12, e.g., when impinging at small grazing angles,
as shown by light beam 17. The light 12 may be in the ultra violet
region of the spectrum or in the 400 to 500 nanometer wavelength
region, to match the activation wavelength of photochromic material
layer 10.
[0038] FIG. 4 is a schematic view of an active transparency
controlled window 24 using a photochromic material 10 for the whole
device, having two layers of reflecting coating 20 on its two
faces. The combination of the photochromic material 10 and the two
coatings 20 serves as a waveguide for the activating light 12. The
optical transparency of the window 24 is controlled by the amount
of active material in the material 10 and the strength of the
activating light 12. Regular, visible or infrared light 4 impinging
on the window 24 is reduced in intensity while transmitted through
the window 24 and exits as reduced light energy 6, where part of
the impinging light 4 is absorbed in the activated layer 10. The
transparency of the photochromic layer 10 is controllably altered
by the activating light, which permits use of the controllable
light source 12 to alter the transparency of the window by
adjusting the strength of the light directed into the photochromic
material. The photochromic material is activatable by light within
a predetermined range of wavelengths, and the controllable light
source produces light having a wavelength within that predetermined
range. The two coatings 20 are transparent for the impinging light
4, but reflective for the activating light 12, e.g., when impinging
at small grazing angles, as shown by light beam 26. The light 12
may be in the ultra violet region of the spectrum or in the 400 to
500 nanometer wavelength region, to match the activation wavelength
of photochromic material layer 10. Confining the material 10
between two reflecting layers 20, for the activating light 12,
serves as a shield to the eyes of a person looking through window
24 against the possible irritation or damage by ultra violet
light.
[0039] FIG. 5 is a schematic view of the light source 12
arrangements for an active transparency controlled window 34 (a)
using a direct light emitting diode array or diode lasers 28, and
(b) using fiber optics delivery 30 of light emitting diodes or
diode lasers 32. The light 12 may be in the ultra violet region of
the spectrum or in the 400 to 500 nanometer wavelength region, to
match the activation wavelength of the photochromic material layer
in the layer 10. The light can be delivered through a lens or lens
array 36 to control the collimation of light source 12.
[0040] FIG. 6 is a schematic view of an active transparency
controlled window 38 using a photochromic material layer 10 coated
or glued to a layer 9 of a material, e.g., glass or plastic, that
is transparent to at least selected wavelengths of light, where the
layer 9 serves as waveguide. The layer 9 provides a waveguide for
the activating light 12 where part of the light 13 penetrates the
photochromic material layer 10 from the layer 9. The optical
transparency of window 38 is controlled by the amount of active
material in the layer 10 and the strength of the activating light
12. Regular, visible or infrared light 4 impinging on the window 38
is reduced in intensity while transmitted through the window 38 and
exits as reduced light energy 6, where part of the impinging light
4 is absorbed in the activated layer 10. The transparency of the
photochromic layer 10 is controllably altered by the activating
light, which permits use of the controllable light source 12 to
alter the transparency of the window by adjusting the strength of
the light directed into the photochromic material. The photochromic
material is activatable by light within a predetermined range of
wavelengths, and the controllable light source produces light
having a wavelength within that predetermined range. The layer 9 is
transparent for the light 4, but reflective for the activating
light 12, e.g., when impinging at small grazing angles, as shown by
light beam 17. The light 12 may be in the ultra violet region of
the spectrum or in the 400 to 500 nanometer wavelength region, to
match the activation wavelength of the photochromic material in the
layer 10. In FIG. 6, the light 4 enters the window 38 from the side
of the layer 9 and exits as light 6 from the side of the
photochromic material layer 10. Light traveling in the opposite
direction will experience similar attenuation.
[0041] FIG. 7 is a schematic view of an active transparency
controlled window 40 using a photochromic material layer 10 coated
or glued to a tapered layer 42 of a material, e.g., glass or
plastic, that is transparent to at least selected wavelengths of
light. The layer 42 serves as a waveguide, where part of the light
13 penetrates the photochromic material layer 10 from the layer 42.
The tapering of the layer 42 provides even illumination of the
photochromic material layer 10. The optical transparency of the
window 40 is controlled by the amount of active material in the
layer 10 and the strength of the activating light 12. Regular,
visible or infrared light 4 impinging on the window 40 is reduced
in intensity while transmitted through window 40 and exits as
reduced light energy 6, where part of the impinging light 4 is
absorbed in the activated layer 10. The transparency of the
photochromic layer 10 is controllably altered by the activating
light, which permits use of the controllable light source 12 to
alter the transparency of the window by adjusting the strength of
the light directed into the photochromic material. The photochromic
material is activatable by light within a predetermined range of
wavelengths, and the controllable light source produces light
having a wavelength within that predetermined range. The layer 42
is transparent for the light 4, but reflective for the activating
light 12, e.g., when impinging at small grazing angles, as shown by
light beam 17. The light 12 may be in the ultra violet region of
the spectrum or in the 400 to 500 nanometer wavelength region, to
match the activation wavelength of the photochromic material in the
layer 10. In FIG. 7, the light 4 enters window 40 from the side of
the layer 42 and exits as light 6 from the side of the photochromic
material layer 10. Light traveling in the opposite direction
experiences similar attenuation.
[0042] FIG. 8 is a schematic view of an active transparency
controlled window 44 using multiple photochromic material layers
52, 54 and 56 separated by layers 58, 60 and 62 of a material,
e.g., glass or plastic, that is transparent to at least selected
wavelengths of light. The glass layers 58, 60 and 62 serve as
waveguides. The optical transparency of the window 44 is controlled
by the amount of active material in the photochromic layers 52, 54
and 56 and the strength of the activating beams 46, 48 and 50,
where each of the activating light beams 46, 48 and 50 controls one
photochromic filter 52 or 54 or 56. In case the photochromic layers
52, 54 and 56 are absorbing, e.g., layer 52 is red-absorbing, layer
54 is green-absorbing and layer 56 is blue-absorbing. Thus, the
window 44 filters out part of the spectrum, using one or more
activated filters 52, 54 and/or 56. Regular, visible or infrared
light 4 impinging on the window 44 is reduced in intensity while
transmitted through the window 44 and exits as reduced light energy
6, where part of the impinging light 4 is absorbed in the activated
layers 52, 54 and 56. The filter 44 is transparent to the light 4,
but the layers 52, 54 and 56 absorb parts of the optical spectrum.
The activating lights 46, 48 and 50, when impinging at small
grazing angles, as shown by light beam 17, are guided by the layers
58, 60 and 62 and the activated layers 52, 54 and 56 in a
controlled way. The lights 46, 48 and 50 may be in the ultra violet
region of the spectrum or in the 400 to 500 nanometer wavelength
region, to match the activation wavelength of the photochromic
material in layers 52, 54 and 56. The transparency-controlled
window 44 controls the optical spectral range and the intensity of
the transmitted light 6.
[0043] FIG. 9 is a schematic view of an active transparency
controlled window 66 using a graded photochromic material layer 64
and a glass or plastic layer 68 that serves as a waveguide. The
optical transparency of the window 66 is controlled by the amount
of active material in the photochromic layer 64 and the strength of
the activating light. Light 4, impinging on the window 66 is
reduced in intensity while transmitted through window 66 and exits
as reduced light energy 6, where part of the impinging light 4 is
absorbed in the activated layer 64. The activating light, when
impinging at small grazing angles as shown by light beam 17, is
guided by the glass layer 68 and the activated layer 64 in a
controlled way. The activating light may be in the ultra violet
region of the spectrum or in the 400 to 500 nanometer wavelength
region, to match the activation wavelength of the photochromic
material layer. The transparency-controlled window 66 controls the
optical intensity of the transmitted light 6. The amount of
activated material in the layer 64 is graded as shown in graph 68,
with the amount of photochromic material increasing with the
distance from said light source, to provide a substantially uniform
reduction of impinging light across the window. This provides a
spatially even reduction of light 4 across the active transparency
controlled window 66, even when the activating light 46 impinges
only from one side of the window 66.
[0044] FIG. 10 is a photograph of an experiment in which a window
is partially activated by a light source (black flashlight) located
on one narrow edge of the window (similar to FIG. 3). In this
window, the photochromic material layer, composed of naphthopyrans
type photochromic molecules at around 4% concentration within a
plastic matrix of acrylic type, is sandwiched between two glass
layers. The right half of the window sample is not activated and
remains highly transparent, while the left side, which is subjected
to light from the black flashlight emitting at .about.400 nm, shows
a dramatic reduction in its transparency. A more evenly distributed
illumination, e.g., by multiple light sources, will result in a
uniform appearance with regard to the light transmittance of the
window.
[0045] FIG. 11 is a diagram of an active transparency controlled
window 70 having a photochromic material layer 76 and a layer 74 of
a material that blocks the activating light. The photochromic
material 76 is sandwiched between two layers 72 of glass or plastic
where one glass or plastic layer is coated to provide the blocking
layer 74 for the activating light. The blocking layer 74 is
transparent to all other wavelengths of light. The activating light
and the regular light come from the same source, e.g., solar light,
in direction 78 or 80, and the response of the device depends on
the direction of the incoming light. Specifically, when the
activating light arrives in direction 80 and engages the blocking
layer 74 before impinging on the photochromic material 76, the
window will stay transparent. When the activating light arrives in
direction 78 and engages the photochromic material 76 before
impinging on the blocking layer 74, the window will change its
transparency and transmit only a fraction of light. The
photochromic material can be designed to turn substantially opaque
when activating light arrives in direction 78, so that this window
acts like a light diode for the impinging light 78 or 80 that
contains the activating light, e.g., fully transparent for light
coming from direction 80 and nearly opaque for light coming from
the opposite direction 78.
[0046] While particular embodiments and applications of the present
invention have been illustrated and described, it is to be
understood that the invention is not limited to the precise
construction and compositions disclosed herein and that various
modifications, changes, and variations may be apparent from the
foregoing descriptions without departing from the spirit and scope
of the invention as defined in the appended claims
* * * * *
References