Note: Descriptions are shown in the official language in which they were submitted.
CA 02745504 2011-07-07
Localized Tinting of Switchable Glass for Glare Reduction in Vehicles
FIELD OF THE INVENTION
This invention relates to methods for reducing the glare encountered by the
occupants of
a vehicle as a result of glaring light entering from outside the vehicle-such
as from oncoming
headlights or the sun at dusk or dawn. As well, the solution described herein
relates to and builds
on the field of switchable glass technologies such as electrochromatic
devices, suspended
particle devices, polymer-dispersed liquid crystal devices, and microblinds.
BACKGROUND TO THE INVENTION
The glaring light that enters vehicles through their glass windows poses not
only an
inconvenience to the occupants of the vehicle but, where it affects the sight
of the driver, a safety
hazard. Several methods have been developed and used in an attempt to reduce
the experience of
this glaring light, and yet none of them seem altogether satisfactory. In
general these methods are
of three sorts:
The first sort is use of devices worn on the person of the occupant that
attempt to block or
deflect glaring light once it has already entered the vehicle but before it
reaches the eyes of the
occupant. Examples of this sort are the wearing of sun visor headwear and
sunglasses. However
the devices of this sort do not offer a proper solution to the problem of
glaring light. Either they
reduce glare insufficiently, such as with visor headwear, or they pose the
risk of reducing
visibility to an unacceptable degree throughout the field of vision of the
wearer, such as with
sunglasses. They also have the drawback of not being appropriate or practical
to wear by all
persons at all times.
The second sort is use of devices physically placed inside the vehicle and
that attempt to
prevent glaring light from reaching the occupants once it has already entered
the vehicle. Aside
from the drop-down visors typically attached to the roofs of automobiles,
numerous innovative
devices such as those detailed by Canadian patents CA 1078429, CA 1219618 and
CA 1302457
can be said to be of this sort. As with devices of the first sort mentioned
above, these devices
either block glare insufficiently or reduce visibility to an unacceptable
degree. As they are
physical objects located inside the vehicle they may also pose a safety hazard
either during
normal operation of the vehicle or during an accident.
The third sort is the use of devices positioned on or within the vehicle's
windows and that
attempt to prevent glaring light from entering the vehicle. Examples include
tinting of windows
and use of special films. However it is obvious that in conditions of low
light the reduction in
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visibility can be unacceptable. Recent developments in glass technology have
led to the creation
of what is known as switchable glass. This term refers to glass that can
adjust its properties of
35 light penetration in response to a stimuli. Photochromatic glass, which
changes chemical and
physical properties automatically in response to light encountered by the
glass pane-detected by
absorption-is not typically used in vehicles due to the inability to control
or override the change
in properties when deemed necessary. More potential for vehicular application
is
electrochromatic glass such as the technology assigned to SAGE
Electrochroamtics Inc. in
40 United States patents No. 7,373,610, No. 7,593,154 and others [1]. Glass
that functions as a
suspended particle device or as a polymer-dispersed liquid crystal device may
also have
vehicular applications. Indeed there is evidence in the literature of
experimental use of such
switchable glass technologies in certain glass surfaces of automobiles [2].
While often
sufficiently blocking glaring light and having the benefit of posing no
physical hazard to the
45 occupants of the vehicle it is clear that, without further innovation,
these switchable glass
technologies are not sufficient solutions to the problems of glare: they tint
the entirety of the
window or none of it, as opposed to a selectable, localized section [3].
The innovative step undertaken by the inventors of the method described herein
is the use
of localized tinting in order to sufficiently block the glaring light coming
from any direction and
50 entering from any window while posing little danger of unacceptably
reducing the field of vision
of the driver.
SUMMARY OF THE INVENTION
The inventive method is the use of windows made of glass that can tint one or
more
localized regions to the exclusion of others in order to block glaring light
but not overly reduce
1. Niklasson, G.A. and C.G. Granqvist. Electrochromatics for smart windows:
Thin films
of tungsten oxide and nickel oxide, and devices based on these. Journal of
Materials
Chemistry 2007, 17, 127-156.
2. Lynam, R.L. Smart windows for automobiles. 1990. Presentation at the SAE
International Congress and Exposition, Detroit, MI, February, 1990.
3. Kubo, T., J. Tanimoto, M. Minami, T. Toya, Y. Nishikitani, and H. Watanabe.
Performance and durability of electrochromatic windows with carbon-based
counter
electrode and their application in the architectural and automotive fields.
Solid State
Ionics 2003, 165, 97-104.
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CA 02745504 2011-07-07
55 visibility. There are many technologies and devices that can be utilized in
the use of this
method-several will be discussed in this section and it is possible that some
of them are novel
conceptions of the inventors. Deciding on which embodiment to select for
manufacture may
depend on both practical considerations and the legal requirements of
different jurisdictions.
Nevertheless it is clear that the inventive step of the inventors is not
limited to any one possible
60 embodiment.
Fundamentally, embodiments of this method will require three parts: (i) at
least one
switchable glass window divided into sections that can be individually tinted,
(ii) a device which
applies the appropriate stimuli or current to the sections of the glass that
darken, (iii) a device
that determines what current or other stimuli is to be applied and therefore
what areas of the
65 glass are tinted.
The (i) glass window may utilize any number of technologies to render it
tintable in
localized areas. For the purposes of the inventive method glass functioning as
electrochromatic
devices, suspended particle devices or polymer-dispersed liquid crystal
devices would be
appropriate. This likely requires the partitioning of the glass window into
several smaller
70 sections--of a size that balances both the ability for one or two such
sections being tinted to
sufficiently block out glaring light without creating an unacceptable loss of
visibility. It must be
possible for these sections to be tinted individually through
electrochromaticism, suspended
particle technology, or other means. This can be accomplished in numerous
ways: A very simple
method would be to be for a window functioning as a suspended particle device
to have different
75 chemical laminates in different areas of the glass, each requiring a
different current to retain
transparency. A more practical embodiment, in that it does not require several
different chemical
laminates, would be to route different current to different parts of the glass
of a window
functioning as an electrchromatic device. Again, various means exist for
accomplishing this.
The (ii) device that directs current or other stimuli relevant to switching
between tinted
80 and transparent glass in switchable glass windows must presumably be
located in close
proximity to the window and connected to it. Depending on the positioning of
the glass it may be
possible for one such part to control stimuli routed to more than one window
in the vehicle.
The (iii) control device offers the most interesting possibilities for diverse
embodiments
of the method. Essentially there are three possible forms of control: First,
it is possible for the
85 tinting to be controlled manually by the driver or potentially passenger of
the vehicle: from the
default transparent state, the person selects which section or sections of the
window they desire
to be tinted, and can manually select tinted panels to be returned to a
transparent state. A
practical form of such manual control would be a touchscreen interface which
shows a diagram
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or other schematic of the tintable windows in the vehicle gridded into
sections that can be tinted.
90 In many cases such an interface would not require a separate device: it can
be a function of
touchscreen devices already a part of a vehicle such as Global Positioning
System interfaces that
are equipment on many automobiles. A program could also be written to enable a
portable
Global Positioning System or even various forms of portable electronic devices
persons may
already posses to act as such an interface. With the proper technology
emerging for tracking of
95 the position of a person's limbs-in common use in the entertainment console
industry as of this
application-it may be possible for an interface which is based on, or allows
the option to, select
which panels are to be tinted by the driver pointing at those panels. However
especially in this
case it may be important to incorporate a series of safeguards to ensure that
there is not an
accidental selection of a glass panel that may unacceptably reduce visibility.
100 Second, it is possible, with the development of specialized technology to
enable it, for the
controller to function automatically. Locating the direction of glaring light
and the position of the
eyes of drivers and possibly other occupants of a vehicle-through the use of
cameras akin to
those used to track positioning of limbs-and tint those sections of glass
which would reduce or
eliminate glare to the eyes of the person or persons.
105 Third, a practical method of control would be one that incorporates both
automatic and
manual selection.
DESCRIPTION OF AN EMBODIMENT
FIG. 1 illustrates an example embodiment of the invention: polymer-dispersed
liquid
crystal device front window of an automobile, capable of manual control. Parts
labeled are
110 explained in the example usage given in the next paragraph. Although as
previously described
the invention can be used with any glass window of a vehicle, the front window
of an automobile
has been selected as this is an application that may be of most interest to
consumers and
manufacturers. It should also be noted that polymer-dispersed liquid crystal
technology and the
described manual controls are chosen as a readily comprehensible example; as
mentioned
115 previously various switchable glass technologies and controllers can be
used.
An example use of this embodiment is as such: the driver of the automobile 1
is
experiencing glaring light 2 impeding their vision. They then use the
touchscreen user-interface 3
located on the dash of the automobile to select which areas of the window they
desire tinting.
The current-controller then sends the appropriate current to the switchable
glass window 4. The
120 regions selected 5 darken to impede the transmission of glare. The rest of
the window remains
transparent 6.
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