Visual display device

A passive reflective device provides a warning or message visible when the intensity of light incident on the device exceeds a preselected minimum intensity or threshold value. The device includes a display, in the form of statements, pictographs, or images, with an appearance which is altered in color or pattern when impinged upon by light with an intensity greater than the threshold value and viewed by a viewer in front of the device. The device can be used as a sign or stationary display, such as a road sign, or it can be mounted on or in a front vehicle facing behind the vehicle such that the display is visible from behind the vehicle by someone who is within a preselected range of angles. The device can be mounted on the bumper or body of the vehicle, and the display can provide information, such as a visible warning to the driver of the following vehicle that his or her lights are shining so brightly on the front vehicle so as to cause the driver of the front vehicle to become uncomfortable, distracted, and/or temporary blind due to reflections of the following vehicle's headlights in the front vehicle's rear view mirror or mirrors. The device may have several appearances which change as the light intensity progressively exceeds several corresponding threshold intensities.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention is related generally to signs and visual warning
 devices which convey different information at different light intensity
 levels, and more particularly to a device which can be mounted on a motor
 vehicle and which conveys one or more messages when light of one or more
 predetermined intensities is incident upon the device.
 2. Description of Related Art
 When driving a motor vehicle, it is often necessary and/or advisable to
 send a signal to other drivers to warn them of the presence or anticipated
 movements of the first vehicle. Devices commonly used to convey such
 signals include head lights, tail lights, and turn signal indicators.
 These types of signals are all intended to warn the driver of the
 following vehicle of actions of the front vehicle. Another type of signal
 which can be sent by a driver is to simply flash his or her vehicle's
 headlights to warn the driver of a vehicle approaching from the front that
 his or her headlights are too bright and are distracting or temporarily
 blinding the first driver.
 However, there are other common types of situations in which it has been
 virtually impossible to warn other drivers when they are doing something
 which is distracting and/or dangerous to someone else. For example, when
 driving at night, the driver of a front vehicle can also become distracted
 and/or temporarily blinded by headlights from a following vehicle when
 they are reflected in the rear view mirrors of the front vehicle. This
 often occurs when the following vehicle has approached the first vehicle
 too closely with its "high beam" on; when the headlights of the following
 vehicle are mounted high relative to the position of the driver in the
 first vehicle, such as when a truck approaches a passenger vehicle; or
 because the following vehicle's headlights are incorrectly adjusted. In
 any case, the situation is dangerous as well as annoying for the driver of
 the first vehicle because it interferes with his or her ability to see and
 react to road conditions.
 A common solution to this problem is to use rear view mirrors which can be
 adjusted so that the intensity of the reflection is reduced. However,
 these adjustable mirrors have two major shortcomings. First, the intensity
 of all reflected light is reduced, thereby significantly decreasing the
 driver's ability to observe other objects and his or her depth perception
 of the reflected images. Such rear view mirrors are generally adjusted by
 a manually operated switch, so the driver is faced with a choice of (a)
 having to remove his or her hand from the steering wheel to adjust the
 mirror whenever bright lights approach from behind or (b) leaving the
 mirror adjusted for limited reflection and compromising his or her
 awareness of what is happening around his or her automobile. Second, such
 adjustable rear view mirrors are not generally mounted externally to the
 vehicle, and the driver can still be distracted or blinded by light
 reflected from externally mounted mirrors.
 In principle, all vehicles could be required to have properly adjusted
 headlights and the use of headlight high beams could be prohibited,
 partially solving the problem of distraction and blinding by bright
 headlights of a following vehicle. However, it is impractical for all
 vehicles to have properly adjusted headlights at all times. Simply loading
 the trunk of a passenger vehicle for a short trip can significantly
 increase the angle between the ground and the vehicle's headlight beam,
 and it may not always be easy to readjust the headlights properly. Also,
 prohibiting the use of high beams in rural areas, where there is no
 ambient or overhead lighting along the roadway at night, would be
 dangerous, as it also would diminish the driver's ability to see bends and
 obstacles in the road. Further, these requirements would not eliminate the
 situation where the driver of the first vehicle is exposed to intense
 light coming from a following truck or other vehicle with headlights
 mounted relatively high.
 All of the signaling methods discussed above require the use of equipment
 which is placed in essentially all road vehicles during the manufacturing
 process. Headlights, tail lights, turn signals, and rear view mirrors are
 all relatively expensive items. Also, many of the existing signaling
 devices, including some rear view mirrors, utilize light sources and,
 therefore, installation requires the emplacement of wiring and connection
 to the vehicle's electrical system.
 Thus, there is a need for a device which conveys different information with
 different incident light intensities. There is a further need for a device
 which provides a signal to a following driver that his or her vehicle's
 headlights are dangerously bright when reflected into the eyes of the
 driver of the forward vehicle. Preferably, such a signal can be
 transmitted without sending such a signal to other nearby drivers whose
 headlights are not offensive. There is a still further need for a
 signaling device with a signal which is visible only when the reflection
 is sufficiently bright to distract the driver of the forward vehicle.
 There is yet a further need for such a warning device which is inexpensive
 to produce. There is an additional need for a warning device which can be
 easily and inexpensively mounted to a vehicle at some time after the
 vehicle is manufactured. There is also a need for a device which operates
 by passive illumination, without requiring a light source powered by the
 electrical system of the vehicle to which it is mounted.
 SUMMARY OF THE INVENTION
 It is an object of the present invention to provide a signaling device with
 a signal which is visible to a viewer facing the device only when the
 illumination is brighter than a threshold light intensity.
 It is a further object of the present invention to provide a device which
 informs a following driver that his or her vehicle's headlights are
 dangerously bright when reflected into the eyes of the driver of the
 forward vehicle.
 It is also an object of the present invention to inform the driver of a
 following vehicle that his or her vehicle's headlights are dangerously
 bright without sending such a signal to other nearby drivers whose
 headlights are not offensive.
 It is a still further object of the present invention to provide a visual
 warning device which is inexpensive to produce.
 It is yet a further object of the present invention to provide a visual
 warning device which can be installed in or mounted to a vehicle during
 the vehicle manufacturing process.
 It is an additional object of the present invention to provide a visual
 warning device which can be easily and inexpensively mounted to a vehicle
 at some time after the vehicle is manufactured.
 It is also an object of the present invention to provide a signaling device
 which operates by passive illumination, without requiring a light source
 powered by the electrical system of the vehicle to which it is mounted.
 To achieve the foregoing and other objects and in accordance with the
 purpose of the present invention broadly described herein, one embodiment
 of this invention comprises a reflective display device for providing a
 visual message to an observer in front of the device. The device comprises
 a display means having a first appearance when impinged upon by light
 originating in front of the display and having an intensity less than a
 threshold intensity. The display means also has a second appearance, with
 the message visible, when impinged upon by light originating in front of
 the display and having an intensity greater than the threshold intensity.
 The display means may have one or more additional appearances when
 impinged upon by light with an intensity greater than an additional
 threshold intensity. The display appearances differ from one another in
 color and/or pattern. The device also comprises means for reflecting
 incident light to provide the message to the observer. The device may be a
 stationary sign, or it may be mounted on a vehicle. In particular, the
 device may be mounted on the vehicle, such as in the form of a bumper
 sticker or a license plate holders which can be mounted such that the
 displays are visible to the observer when he or she is behind and facing
 the rear of the vehicle. The threshold light intensity may be preselected
 to an intensity which is distracting to a driver who sees the light
 reflected in his or her or her vehicle's rear view mirror, and the message
 may convey a safety warning indicating that the intensity of the incident
 light is too great or that the distance between the first and second
 vehicles is too small, and therefore, that the light is distracting to the
 driver of the vehicle.
 The device may comprise at least one sheet of material including therein a
 first set of indicia visible under normal ambient lighting conditions and
 a second set of indicia visible only when an incident light intensity
 exceeds a preselected threshold value. Each of the sets of indicia may be
 selected from text, pictographs, images, and combinations thereof. The
 device may include at least one element selected from masks, filters,
 holograms, lenses, and prisms to aid in creating the displays. The device
 also may include at least one material which fluoresces or phosphoresces,
 such as to provide all or a part of the second display when the light
 intensity exceeds the threshold. The device includes a reflecting surface,
 which may either be substantially smooth or may form a three-dimensional
 pattern, and the surface may be substantially planar or non-planar. The
 device may also be adapted to reflect light which originates within a
 first preselected range of angles to make the display visible to the
 observer when he or she is within a second preselected range of angles.
 Another embodiment of the present invention comprises a method for
 conveying a warning from a first vehicle to a second driver of a second
 vehicle behind the first vehicle when the headlights of the second vehicle
 shine in a generally forward direction and are intense enough to distract
 the driver of the first vehicle when reflected in a rear view mirror. The
 warning may signal that the headlights of the second vehicle are
 distracting to the driver. The method comprises the step of providing a
 passive display device on the first vehicle which can be viewed by the
 second driver. The display device includes a first display, visible under
 normal ambient lighting conditions, and a second display, visible when an
 incident light intensity exceeds a preselected threshold intensity. The
 second display conveys the warning to the second driver. For example, the
 threshold light intensity may be an intensity which is distracting to a
 driver who sees the light reflected in his or her or her vehicle's rear
 view mirror, and the warning could indicate that the second vehicle is too
 close to the first vehicle and/or that the second vehicle's headlights are
 blinding the driver of the first vehicle. The display device may include
 one or more additional displays which convey additional messages when the
 light exceeds progressively higher threshold intensities.
 The method may also comprise one or more additional steps of masking,
 filtering, and/or diffracting a portion of the incident light. Also, the
 method may further comprise an additional step of selecting light which
 originates within a preselected range of angles relative to a surface of
 the device and reflecting at least some of the light so the displays are
 visible to the observer when he or she is within a second preselected
 range of angles relative to the surface.
 The first and second displays may differ in color and/or pattern. The
 message may have a form selected from text, pictographs, images, and
 combinations thereof.

DESCRIPTION OF THE INVENTION
 The present invention is a passive reflective device which provides a
 warning or message visible when the intensity of light incident on the
 device exceeds a preselected minimum intensity or threshold value. The
 device includes a display, in the form of statements, pictographs, or
 images, with an appearance which is altered in color or pattern when
 impinged upon by light with an intensity greater than the threshold value
 and viewed by a viewer in front of the device.
 The device of the present invention can be used as a sign or stationary
 display, such as a road sign, or it can be mounted on or in a front
 vehicle facing the rear of the vehicle and visible from behind the vehicle
 by someone who is within the preselected range of angles. For example, it
 could be mounted on the bumper or body of the vehicle, and the message
 could provide a visible warning to the driver of the following vehicle
 that his or her lights are shining so brightly on the front vehicle so as
 to cause the driver of the front vehicle to become uncomfortable,
 distracted, and/or temporary blind due to reflections of the following
 vehicle's headlights in the front vehicle's rear view mirror or mirrors.
 This distraction or blinding of the driver of the front vehicle can pose a
 potentially dangerous situation, particularly when there is little ambient
 light and the vehicles are moving at high speed, such as when driving at
 night on highways passing through rural areas. The headlights of the
 following vehicle may appear overly bright to the driver of the front
 vehicle for a variety of reasons, such as headlight misalignment, use of
 the high beam in too close proximity to the front vehicle, or the
 headlights being mounted high relative to the height of the eyes of the
 front vehicle's driver. Until now, it has been difficult or impossible for
 the driver of the front automobile to convey any type of message to the
 driver of the following vehicle regarding the following vehicle.
 As illustrated in FIG. 1a, the present invention 10 comprises a display 12
 that has one appearance under light conditions such as might be found
 during normal daylight or nighttime situations. As shown, the display is a
 regular geometric pattern 12, although the display could be a field of a
 uniform solid color, a text message, or any other pattern. In FIG. 1b, the
 same device shown in FIG. 1a comprises an altered display 14 that is
 visible when the light intensity exceeds the threshold value, such as when
 a vehicle headlight beam is incident upon it. The display can be in the
 form of a stationary sign, or it can be mounted to the exterior or
 interior of a vehicle, such as an automobile or truck. As shown in FIG. 1,
 the display can be a bumper sticker. As shown in FIG. 2, the display 20
 can be incorporated into a frame 22 for a license plate 24 which can
 attached to the back of a vehicle, such as with screws or bolts 26. For
 example, when the light intensity is less than the threshold value, the
 display may show one type of indicia, such as a geometric pattern 28, and
 when the light intensity exceeds the threshold value, the display may
 become highly reflective and/or show different indicia in the form of a
 color change, a text, or a pictorial message 29, such as a notice to a
 following driver that his headlights are so bright they are annoying the
 driver of the vehicle on which the frame 22 is mounted. The threshold
 light intensity can be an intensity which is distracting to a driver who
 sees the light reflected in his or her or her vehicle's rear view mirror.
 Referring to FIG. 3, it can be seen in a general way how the present
 invention works. A display device 10 is mounted on the rear of front
 vehicle 30, with display device 10 mounted so that its front surface 31
 faces away from and behind front vehicle 30. Front vehicle 30 is driven by
 a front driver 32 (whose head is shown as a circle) and is also equipped
 with a rear view mirror 34. Following vehicle 36 with driver 38 is
 directly behind front vehicle 30, with a headlight directed generally
 forward toward front vehicle 30. Light beam 40 is reflected by rear view
 mirror 34 into the eyes of driver 32, potentially distracting and/or
 temporarily blinding driver 32. Light beam 42 is reflected by display
 device 10 and reaches the eyes of following driver 38. By incorporating a
 suitable pictorial or text message into device 10, following driver 38 can
 be informed that his lights are distracting to front driver 32. If display
 device 10 reflects only a fraction of the incident light, the reflected
 light will not blind the following driver 38. Display device 10 can be
 adapted so that the reflected light intensity allows the message to be
 visible to following driver 38 only when the incident light intensity
 exceeds the threshold intensity which will cause discomfort and/or
 distraction to front driver 32. The threshold intensity may be selected
 according to the needs or comfort of a particular driver.
 As shown in FIG. 4, one embodiment of the present invention is a display
 device 50 having a substantially smooth and planar surface 52. Device 50
 also includes a display pattern 54 and a background 56 which is
 incorporated into the material on which surface 52 is formed. Pattern 54
 and/or background 56 are formed, for example, with one or more materials
 which fluoresce visibly when exposed to light which exceeds the threshold
 intensity. The fluorescent material or materials can be arranged to form a
 message which is visible to a person in front of device 50 when the
 intensity of light incident on device 50 exceeds the threshold value.
 Alternatively, one or more phosphorescent materials can be utilized in
 place of the fluorescent material or materials. The fluorescent and/or
 phosphorescent materials can be selected and arranged to provide a
 multicolored display.
 Another embodiment 60 of the present invention is shown in FIG. 5. A mask
 62, having a pattern 64 and a background 66, and light filter 68 are
 sandwiched between a reflecting element 70, having a substantially smooth
 reflecting surface 72, and substantially transparent cover element 74.
 Mask 62 can be painted or printed onto surface 72, or it can be secured in
 contact with surface 72, or it can be secured in a spaced apart position
 relative to surface 72. Mask 62 can be formed from a combination of
 substantially opaque and substantially transparent materials arranged in
 pattern 64 and background 66. Alternatively, mask 62 can include a
 hologram, or it can include fluorescent or phosphorescent materials.
 Filter 68 can be a gray filter, transmitting a fraction of the light
 incident upon it over all visible wavelengths, or it can selectively
 transmit light over a range of visible wavelengths. Filter 68 can also
 include a diffraction grating. The device may include more than one
 filter, and the filters may be identical or have distinct filtering
 capabilities. Cover element 74 is sealed against frame or holder 76 to
 prevent water and dirt from entering the assembly 60.
 In the embodiment 80 shown in FIG. 6, two masks 82 and 84 are sandwiched
 between reflecting element 86 and cover element 88. Masks 82 and 84 each
 have a pattern portion 90 and 92, respectively, and a background portion
 94 and 96, respectively. The pattern and background portions may be
 arranged in identical or different geometric relationships to each other.
 The respective patterns and backgrounds may be of the same color or
 different colors, and the patterns may be formed using materials of
 different transmissibility to visible light. The patterns and backgrounds
 may be formed with combinations of opaque, transparent, fluorescent,
 phosphorescent, and diffracting materials. The visibility of the patterns
 90 and 92 and/or backgrounds 94 and 96 may depend upon the intensity of
 light incident on device 80; the materials used to form masks 82 and 84
 can be selected such that a viewer at position 99 can observe images
 having different patterns and/or brightnesses, depending upon the
 intensity of the light which is incident on device 80. As shown in FIG. 6,
 cover element 88 includes a lens 98 to focus transmitted light.
 As shown in FIG. 7, device 100 includes a reflecting element 102, including
 a pattern and a background, and filtering elements 104 and 106. Light ray
 108 from source 110 is attenuated as it passes through elements 104 and
 106, with the relative intensity of ray 108 shown by the line width. The
 reflectivity of reflecting element 102 and the transmissiveness of
 filtering elements 104 and 106 can be selected such that the intensity of
 ray 108 is great enough for an observer at 112 to recognize the pattern
 only when the intensity of the light incident from sources such as 110 is
 greater than the threshold value.
 If desired, the device may be constructed so that only light incident from
 a selected range of angles relative to the reflecting surface will be
 reflected and/or so that reflected light will be visible within another
 selected range of angles relative to the reflecting surface. This can be
 accomplished by using diffraction gratings or holograms, known in the art,
 as masks and/or filters. Alternatively, as shown in FIGS. 8 and 9, a
 reflecting element 120 having a reflecting surface 122 formed in a
 3-dimensional array of surface elements may be used. As shown, surface
 elements including 124, 126, 128, and 130 form a cubic reflector. A light
 beam 132 originating at source 134 is reflected by element 124 and then by
 element 126 and observable at point 136. Obliquely incident light beam
 138, such as might come from a source at point 140, is reflected by
 elements 128 and 130 toward point 142. The addition of an absorbing rim
 144, extending at least partially around the edges of surface 122,
 prevents obliquely incident light beams, such as 146 originating from
 point 148, from reaching surface 122 and obliquely reflected light from
 reaching observers at points such as 142.
 It should be noted that one or more other refracting devices, such as a
 prism, could be utilized instead of or in addition to a lens, such as 98
 in FIG. 6. The arrangement of filters, masks, lenses, and other refracting
 devices relative to each other can be selected to achieve the desired
 results.
 It is contemplated that some embodiments of the present invention can be
 fabricated inexpensively from inexpensive materials. Thus, the invention
 could be mounted to the rear bumper, rear windshield, or body of a
 vehicle. It is also contemplated that the present invention could be
 fabricated into a form which can be incorporated into a vehicle during the
 manufacturing process, or it could be easily mounted after assembly of a
 motor vehicle, such as with adhesive, magnets, bolts, or other fasteners.
 It is also contemplated that the message or messages visible under higher
 intensity light could contain information other than safety-related
 messages.
 The foregoing description is considered as illustrative only of the
 principles of the invention. Further, since numerous modifications and
 changes will readily occur to those skilled in the art, it is not desired
 to limit the invention to the exact construction and process shown as
 described above. Accordingly, all suitable modifications and equivalents
 may be resorted to falling within the scope of the invention.