Note: Descriptions are shown in the official language in which they were submitted.
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INFORMATION DISPLAY DEVICE
Meld of Invention
The present invention relates to matrix or array
information display devices such as are used as variable
message signs.
Backgvround
Information display devices from which the
displayed information can be varied, sometimes referred
to ws changeable copy or variable message signs, have
been in use for same time. They have been used for such
applications as advertising media, traffic signs,
information displays in or on sports 'stadiums, mass
transit stations and vehicles, etc.
The information-displaying face of such signs is
usually made up of an array or matrix of individually
activated pixels. The pixels are typically capable of
being set in one of two different states of distinctive
2O appearance, i.e., "activated" and "deactivated" states.
By selectively activating and deactivating pixels, the
information displayed can be changed. The sign may
simply switch to anothex~legend (e.g., switch from a
time indication to a temperature indication) or portions
of the existing legend may be moved across the face of
the sign.
Many different pixel types have been used in
variable message signs. In one type, each pixel is an
individually controlled light bulb and bulbs within the
array are selectively energized or de-energized to
generate the desired legend. Another type of, variable
message signs are electromechanical devices with pixels
comprising elements whose position or orientation is
changed to alter their appearance. For example, U.S.
Patent No. 4,318,098 (McGreevy) discloses variable
message signs wherein pixels comprise members that
selectively rotate about an. axis, presenting at least
two different visual appearances as desired to generate
the desired legend. In one embodiment disclosed in that
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patent, the pixels comprise members which are fluorescent
and reflective in one state and have a different appearance,
e.g., black, in another state. Variable message devices
having certain similarities are disclosed in U.S. Patent
Nos. 3,140,553 (Taylor), 3,295,238 (Winrow), 3,518,664
(Taylor), and 4,779,082 (Salam).
In another electromechanical sign disclosed in
U.S. Patent No. 4,163,332 (Salam), the pixels comprise light
transmissive areas in a backlit opaque sheet and movable
opaque vanes that selectively occlude or expose the light
transmissive areas. The reference teaches that the vanes
are reflective, i.e., specularly reflective, such that when
the light transmissive portion of the pixel is exposed the
vane will reflect light from a second source to an observer.
A problem with previously known variable message
signs is that they did not provide sufficient legibility and
conspicuity under a variety of conditions, e.g., at
twilight, under nighttime darkness, during power failures,
etc.
Summary of Invention
The present invention provides matrix or array
information display devices that provide improved legibility
and conspicuity throughout a variety of conditions. Display
devices of the invention provide high conspicuity and
legibility during daylight conditions, at twilight, under
nighttime darkness, during power failures, etc.
In brief summary, the invention provides an
information display device comprising: (a) a legend face
comprising an opaque sheet with a two-dimensional planar
array of pixels thereon, said sheet having a front side to
be presented to an observer and a back side, each pixel
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comprising an aperture in said opaque sheet and an
associated shutter, said aperture being retroreflective and
partially-light-transmissive, said shutter being opaque and
having first and second faces, said second face being
retroreflective, each shutter being selectively settable to
a first state in which it occludes its associated aperture
such that the first face of said shutter is presented to an
observer, and a second state in which it exposes said
associated aperture such that the second face of said
shutter and said associated aperture are presented to an
observer; (b) means for selectively positioning said
shutters in said first and second states; and (c) at least
one light source disposed on said back side of said opaque
sheet.
In important distinctions from previously known
matrix or array information display devices, the second
faces of the shutters are retroreflective, preferably also
fluorescent, and preferably the apertures are also
retroreflective and more preferably retroreflective and
fluorescent. As a result, devices of the invention, and
especially the preferred embodiments thereof, provide
previously unattained uniformity of appearance during
daytime and nighttime hours as well as previously unattained
brightness of appearance under a variety of viewing
conditions.
Brief Description of Drawing
The invention will be further explained with
reference to the drawing, wherein:
Figure 1 is a perspective view of a portion of an
illustrative embodiment of an information device of the
invention;
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Figure 2 is a cross-sectional view of one pixel of
the device shown in Figure 1 in which the shutter has been
positioned in a first state such that it occludes its
associated aperture; and
Figure 3 is a cross-sectional view of a portion of
the pixel shown in Figure 2 in which the shutter has been
positioned in a second state such that its associated
aperture and the second face of the shutter are presented so
as to be visible to an observer.
These figures, which are idealized, are not to
scale and are intended to be merely illustrative and
non-limiting.
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Detailed Description of Illustrative Embodiments
As shown in Figure 1, in a typical embodiment,
information display device 10 of the invention comprises
opaque sheet 12 comprising a two-dimensional planar
array of pixels 14 arranged in horizontal and vertical
rows, sheet 12 having front side 16 and back side 18,
front side 16 being presented so as to be visible to an
observer. As shown schematically, at least one light
source 20 is disposed~..on back side 18 of opaque sheet
12. Opaque sheet 12.,_and array of pixels 14 is referred
to herein as a lege~id face of device 10. By
selectively setting each pixel in one of two visually
distinguishable states; the array of pixels generates a
legend: A device of the invention may have one or more
i5 legend faces.
Each pixel 14 comprises aperture 22 in opaque
sheet l2:and associated shutter 24. As used herein, a
shutter which, in its first state, occludes an aperture
is said to be that aperture's "associated shutter".
Similarly, an aperture which is occluded by a shutter in
the shutter's first state is said to be that shutter's
"associated aperture". Aperture 22 is partially-light-
transmissive such that it will transmit light when
backlit by light source 20. Aperture 22 is preferably
retroreflective on its front side and more preferably is
also fluorescent. Illustrative examples of commercially
available materials that may be used for aperture 22
include SCOTCHLITE Brand Reflective Sheeting Diamond
Grade Series 3923 G and 3924 G, which are yellow and
orange, respectively, retroreflective sheetings sold
commercially by the Minnesota Mining and Manufacturing
Company ("3M"). Such sheetings are sometimes called
cube-corner or prismatic reflectors. Preferred
embodiments of devices of the invention wherein
apertures 22 are retroreflective, and particularly where
they are also fluorescent, provide exceptional and
unexpected levels of visibility and legibility.
Shutter 24 is opaque and has first face 26 and
second face 28. First face 26 has an appearance that is
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visually distinguishable from second face 28, e.g., has
a different color, and is preferably of low reflectance.
For example, it may have a matte black finish. It is
' typically preferred that first face 26 of shutters 24
and the portions of front side 16 of sheet 12 between
' apertures 22 have similar appearances. If first faces
26 and front side 16 are similar in appearance.and of
low reflectance, e.g., matte black, better contrast with
activated pixels is provided and non-activated pixels
appear indistinguishable from the background. The
resultant device can generate a more readily visible,
'crisper" looking legend.
Each shutter 24 is selectively settable to or
positionable in a first state and a second state, e.g.,
by operation of means for positioning 30. As shown in
Figure 2, in the first state, shutter 24 occludes its
associated aperture 22 with first face 26 of shutter 24
being presented so as to be visible to an observer (not
shown). As shown in Figure 3, in the second state,
shutter 24 exposes associated aperture 22 such that
second face 28 of shutter 24 and associated aperture 22
are both visible to an observer (not shown).
Second face 28 is made of a retroreflective
material. Illustrative examples of materials which may
be used for second face 28 include such sheetings as 3M
SGOTCHLITE Brand Reflective Sheeting Diamond Grade
Series and High Intensity Series sold commercially by
the 3M. If desired, second face 28 can be made of the
same material as aperture 22 if another layer within
shutter 24 is opaque. Preferably, aperture 22 and
second face 28 are of substantially similar color and
retroreflective performance such that under
retroref~'ective viewing conditions the pixel has a
uniform appearance. At relatively longer viewing
distances, nonuniformities within individual pixels
~ become less apparent.
The present invention provides great utility and
unexpected performance because second faces 28 of
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shutters 24 are retroreflective, and preferably fluorescent,
and apertures 22 are partially-light-transmissive, and
preferably retroreflective. As a result, devices of the
invention provide exceptional visibility under a variety of
conditions, including during bright daylight illumination at
twilight, and at dark nighttime. Signs of the invention
also provide high visibility in the event of internal light
source 20 failure as well. ,
Shutter 24 is moved from its first state shown in
Figure 2 to its second state shown in Figure 3 by operation
of means for positioning 30. Various suitable means for
selectively moving shutters 24 will be apparent to those
skilled in the art. Shutters 24 may be switched between
their first and second states by hand or by operation of
individual motors, mechanical drive systems, etc. In a
simple embodiment, means for positioning 30 is simply a
pivot or axle about which shutter 24 is moved between its
first and second states by hand. Preferably, means for
positioning 30 is a mechanism that positions shutter 24 as
desired without manual labor. U.S. Patent No. 4,819,357
(Salam) discloses a display device having an array of vanes
(i.e., shutters) that are rotated between closed and opened
positions (i.e., first and second states) by selectively
actuated electromagnets. Each pixel may be operated under
individual manual control or the entire array may be
operated by a computer programmed to selectively position
individual pixels as appropriate for the desired legend
which the device is to display. Such systems may be used to
great advantage in the present invention.
Typically, a device of the invention is fully
enclosed, with provision for ventilation if desired,
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encasing the light sources) and certain components of the
means for positioning the pixels, etc. As mentioned above,
a device of the invention may comprise more than one legend
face. The pixel arrays of different legend
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faces may be operated independently or in concert as
desired.
As shown in Figure 1, in some embodiments, each
pixel 14, whether in its first state or second state, is
separated from adjacent pixels by a portion of front
side 16, referred to herein as a buffer zone.
Typically, it is preferred that front side 16 have a
similar appearance to first face 26 of shutter 24 so as
to maximize the contrast between pixels in their second
state from those in their first state and from front
side 16. If desired, the pixels may be arranged on the
opaque sheet 12 in very close proximity so that adjacent
pixels are separated by only a small buffer zone or even
abut directly together.
Pixels l4 shown in Figure l have substantially
square apertures 22 and shutters 24. It will be .
understood, however, that the apertures and associated
.shutters may be made in other shapes (not shown) as
desired, e.g., other polygons (such as rectangles or
octagons), circles, semicircles, etc. A shutter is
preferably large enough and positioned properly so as to
be capable of occluding the entirety of its associated
aperture. Accordingly, apertures will typically be of
similar shape and of similar or slightly smaller size
than their associated shutters. It is not required,
however, that apertures and their associated shutters be
of similar shape or similar size. It is also not
necessary for pixels within an array to be of similar
size.
The number of pixels in an array and their size
will depend upon the resolution performance desired of
the device which in turn will depend in part upon its
intended.~location with respect to intended viewers.
. ,
Information display devices which are intended to be
seen from relatively great distances will usually be
made with relatively larger pixels and greater spacing
between pixels than are those which are intended to be
seen From shorter distances. In typical embodiments,
the array is likely to be between about 2 feet by about
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2 feet (about 120 centimeters by about 120 centimeters) and
about 20 feet by about 40 feet (about 12 meters by about 24
meters) in dimension. Arrays having dimensions outside
these ranges may be used if desired.
As shown in Figure 1, device 10 may comprise an
array of pixels arranged in horizontal and vertical rows.
It will be understood, however, that the pixels of devices
of the invention may be arranged in an array of any desired
configuration. For instance, U.S. Patent No. 755,272
(Burnham et al.) discloses a changeable sign wherein pixels
are arranged in an array designed to permit display of an
alpha-numeric character. The legend face of a device of the
present invention might be made up of pixels as described
herein arranged in one or more, typically several, such
arrays with individual pixels being of different sizes and
shapes. Thus, the pixels in an array may be of at least two
different sizes and/or of at least two different shapes.
Light source 20 will typically emit visible light.
A portion of the light emitted by source 20 will be
transmitted through partially-light-transmissive aperture
22, so as to be, in the case of pixels 14 which are in their
second states (Figure 3), visible to one viewing the device.
If desired, light source 20 can be tuned to also emit
radiation of a wavelength that causes aperture 22 to
fluoresce more brightly, thereby enhancing the visibility of
the non-occluded pixels. In such embodiments, selection of
the material used in aperture 22 and of light source 20 will
thus be interdependent.
Figures 1 and 3 show schematically a single light
source 20, e.g., an incandescent or neon light bulb.
Devices of the invention may have a single light source, a
plurality of light sources each of which is intended to
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provide light to a number of apertures 22, or even a single
light source for each aperture 22. For reasons of cost and
complexity, it is typically preferred to construct a device
having fewer light sources. It is typically preferred that
the pixels be substantially uniform when activated (i.e.,
when their shutters are in their second states leaving their
associated apertures unoccluded), Thus, a diffuser will
often be used to make the brightness of each pixel in the
array more uniform. In a preferred embodiment, light may be
introduced into the device so as to illuminate the back side
of the pixels using so called "optical light pipes" or
"light guides" such as are disclosed in U.S. Patent
Nos. 3,691,332 (Reick et al.), 4,260,220 (Whitehead),
4,422,719 (Orcutt), 4,466,697 (Daniel), and 4,805,984
(Cobb). U.S. Patent No. 4,952,023 (Bradshaw et al.)
discloses an internally illuminated sign that employs light
pipe and remote light sources in some embodiments, see,
e.g., Figure 4. Such light introduction techniques may be
used in devices of the invention. An illustrative example
of a commercially available light pipe which may be used
herein is SCOTCH Brand Optical Lighting Film from 3M.
Many retroreflective sheetings, such as 3M's
SCOTCHLITE Brand Reflective Sheeting Diamond Grade Series
cube-corner sheetings, are encapsulated-lens sheetings with
cover films, sometimes called seal films, sealed over the
cube-corners to protect same and maintain the desired air
interface necessary to maintain high retroreflective
brightness. U.S. Patent No. 4,025,159 (McGrath) discloses
one type of such sheeting. When used as an aperture in
devices of the present invention, if the apertures are made
with a sheeting having such a seal film, the seal film may
be clear or translucent. Translucent seal films may provide
a diffusing effect and may be preferred where a separate
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diffuser is not being used. Typically, nonuniformity of the
intensity of light incident to the back side of, and
transmitted by, the apertures tends to be more apparent when
the legend being displayed is made up of a large proportion
of the pixels in their second state than in
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the case of legends made up of more varied patterns of
pixels in their first and second states.
Devices of the invention require power to operate
light source 20 and, unless the shutters are switched
manually, to selectively switch shutters between their
first and second states. In some instances, e.g., when
the means for positioning the shutters employs
electromagnets, external power to maintain shutters in a
particular state may be required. Devices are typically
powered by outside electrical sources, e.g.,
conventional AC electrical service. Other power sources
such as batteries and solar cells may be used to provide
greater utility. For instance, battery power may be
used as a backup, ensuring continued operation in case
l5 of disruptions in commercial electrical service.
Batteries and solar power may be used to permit location
of a device of the invention in remote and/or temporary
locations where commercial electrical service or mobile
generators are unavailable or considered too expensive.
20, One of the advantages of devices of the present
invention is the high visibility provided because the
second faces of the shutters are retroreflective,
preferably fluorescent, and the apertures are preferably
retroreflective and more preferably fluorescent in
25 addition to being partially-light-transmissive. As a
result, the device can still generate a highly visible
legend even if light source 20 is deactivated or left
without power backup in times of disruption of power
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supply from the primary power source while backup Bower
30 is conserved for operation of the means for positioning
the shutters.
If desired, devices of the invention may be built
such thafi, 'in the case of an interruption of power
supply, the pixels (1) remain in their last selected
35 settings, such that the device continues to display the
last legend, or (2) switch to another selected group of
settings, such that the device switches to another
legend. For instance, a sign which displays speed limit
' and other traffic-related information during routine
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operation may, upon failure of power, switch to a group
of shutter settings that generates a preselected
message, e.g., a warning that traffic signals are
inoperative.
Various modifications and alterations of this
invention will become apparent to those skilled in the
art without departing from the scope and spirit of this
invention.
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