WO2009123932A2

WO2009123932A2 - Traffic signal systems

Info

Publication number: WO2009123932A2
Application number: PCT/US2009/038613
Authority: WO
Inventors: Yufeng Liu
Original assignee: 3M Innovative Properties Company
Priority date: 2008-04-02
Filing date: 2009-03-27
Publication date: 2009-10-08
Also published as: WO2009123932A3

Abstract

The present application relates to a traffic light including a light source from which propagates light rays and at least one layer of a structured brightness enhancement film and at least one layer of a light control film. The structured brightness enhancement film and the light control film are positioned adjacent to the light source such that a light ray emitted by the light source propagates through the brightness enhancement film and the light control film.

Description

TRAFFIC SIGNAL SYSTEMS

TECHNICAL FIELD

[0001] The present application relates generally to traffic signal systems.

BACKGROUND

[0002] Since the first electric traffic light was installed at a street intersection in Detroit, Michigan in 1920, traffic lights have become an essential tool for regulating traffic flow. Not only does a traffic light provide an efficient means of controlling traffic flow, it greatly adds to the safety of drivers and pedestrians.

[0003] Conventional traffic control systems rely on timers or vehicle sensors to control the cycle of the traffic light between its red and green phases, thus allowing different directions of traffic flow to enter into and pass through an intersection. The following background information is presented by way of example with reference to a traffic signal system including one specific type of traffic signal light, but the application is meant to include all traffic signal systems including, but not limited to, those including all types of traffic signal lights and traffic signs.

[0004] A standard traffic signal system 10 as used in the United States is shown in FIGS. IA and IB and includes a traffic light 17 having a housing unit 19 that holds a vertical arrangement of three different round signal lights 11, 13, and 15. The top round signal light 11 is a red signal light which represents "Stop," the middle round signal light 13 is a yellow signal light which represents "Caution," and the bottom round signal light 15 is a green signal light which represents "Go." Light is emitted by a light source (not shown) located behind each round signal light. Commonly used light sources include incandescent or solid state light sources (e.g., LEDs). Where incandescent bulbs are used, colored filters 12, 14, 16 (e.g., a red filter 12 for the red light, a yellow filter 14 for the yellow light, and a green filter 16 for the green light) are also used to give the light signal the desired color. Where LEDs are used, colored filters may not be necessary. Attachment of traffic light 17 to a pole 20 in FIG. IA is one exemplary means of fixing traffic light 17 to the ground or positioning it adjacent to a roadway. Many other methods of fixing a traffic light to the ground or positioning it adjacent to a roadway exist, all of which can be used instead of the specific means shown in FIG. IA.

[0005] While traffic signal systems have been around for over 80 years, traffic signal system improvements continue to be desirable.

SUMMARY

[0006] The present application relates to an improved traffic signal system that has features that enhance the visibility of the traffic signal lights to viewers. At least some of the embodiments of the present application provide improved safety for motorists and pedestrians and may minimize the incidence of traffic accidents.

[0007] Some embodiments of the present application describe an improved traffic signal system in which the viewing angle of a traffic light is narrowed. These embodiments may, for example, ensure that only the drivers in certain designated traffic lanes can see the traffic light.

[0008] Some embodiments of the present application describe an improved traffic signal system exhibiting reduced glare. These embodiments may, for example, facilitate traffic light differentiation for motorists who are driving in sunny conditions when glare from the sun can make detection of the traffic light that is illuminated challenging.

[0009] Some embodiments of the present application describe an improved traffic signal system having higher contrast properties.

[0010] The present application relates to a traffic light including a light source from which propagates a light ray and at least one layer of a brightness enhancement film and at least one layer of a light control film. The brightness enhancement film and the light control film are positioned adjacent to the light source such that a light ray emitted by the light source propagates through the brightness enhancement film and then through the light control film.

BRIEF DESCRIPTION OF DRAWINGS

[0011] FIG. IA is a schematic view of a traffic signal system of the type commonly used in the United States, and FIG. IB is a front view of an enlarged portion of FIG. IA. [0012] FIGS. 2A and 2B are schematic drawings of an intersection with, respectively, prior art traffic lights and improved traffic lights.

[0013] FIGS. 3A and 3B are schematic drawings of an intersection with, respectively, prior art traffic lights and improved traffic lights.

[0014] FIG. 4 is a cross-sectional view of an exemplary light control film.

[0015] FIG. 5 is a cross-sectional view of an exemplary BEF.

[0016] FIG. 6 is an exploded view of one exemplary embodiment of an improved traffic light including a layer of light control film and a layer of BEF.

[0017] FIG. 7 is an exploded view of another exemplary embodiment of an improved traffic light including a layer of light control film and a layer of BEF.

[0018] FIG. 8 is an exploded view of another exemplary embodiment of an improved traffic light including a layer of light control film and a layer of BEF.

[0019] FIG. 9 is an exploded view of one exemplary embodiment of an improved traffic light including a layer of BEF.

[0020] FIG. 10 is an exploded view of another exemplary embodiment of an improved traffic light including a layer of BEF.

[0021] FIG. 11 is an exploded view of another exemplary embodiment of an improved traffic light including a layer of light control film and a layer of BEF.

[0022] FIG. 12 is an exploded view of another exemplary embodiment of an improved traffic light including a layer of light control film and a layer of BEF.

DETAILED DESCRIPTION

[0023] The inventor of the present application recognized that conventional traffic signal systems have certain drawbacks that could be improved by narrowing the horizontal viewing angle and/or reducing the glare of the traffic lights in the traffic signal systems. [0024] FIG. 2A pictorially exemplifies one scenario that highlights a drawback of the currently available traffic signal systems. FIG. 2A is a schematic drawing of an intersection 20 where a first road 22 and a second road 24 intersect. First road 22 includes first road drivers 26 and first traffic signal 32, and second road 24 includes second road drivers 28 and second traffic signal 34. In this particular example, the angle (α) at which first road 22 and second road 24 intersect is less than 90°, although the angle may vary. Conventional traffic lights 32 and 34 have wide viewing angles β₂A (typically approximately 120° or greater). Consequently, both first and second drivers 26 and 28 can see both first and second traffic signals 32 and 34. One or both of first and second drivers 26 and 28, respectively, may be confused regarding which traffic signal relates to them and may proceed through the intersection at the wrong time, resulting in an accident. [0025] The inventor of the present application recognized that the risk of an accident occurring in the scenario shown in FIG. 2A could be reduced by narrowing the viewing angle of traffic lights 32 and 34. FIG. 2B is a schematic drawing of the intersection 20 of FIG. 2 A in which traffic signals 32 and 34 have viewing angles β₂β that are narrower than the viewing angles β₂A of FIG. 2A. Viewing angle β₂β are shown as being approximately 30°, but those of skill in the art will appreciate that the viewing angles β₂β may vary. The narrowed viewing angle β₂β of first and second traffic control signals, 32 and 34, respectively, eliminates or diminishes the ability of each of first and second drivers 26 and 28 to see traffic lights 34 and 32, respectively, that do not relate to the driver's road. Consequently, driver confusion about which light relates to him/her is greatly reduced and the incidence of vehicular collision at the intersection decreases.

[0026] A scenario that can result in vehicular collision occurs when a driver stopped at a red light monitors the traffic light controlling the traffic on the intersecting road and proceeds through the intersection immediately after the intersecting road's light turns red rather than waiting for the driver's own light to turn green. If a driver on the intersecting road enters the intersection on a yellow (which is legal) or red light (which is illegal), then the two vehicles will collide. By proceeding through the intersection before the driver's light has turned green, the driver increases the risk of being involved in a vehicular collision. Further, many traffic lights are set on timers such that there is a short time interval during which all traffic lights at the intersection are red. This is in part to reduce the risk of collision in the event of red light running or green light guessing as described above.

[0027] FIG. 3A is a schematic drawing that exemplifies the scenario described above. In FIG. 3A, a first road 42 and a second road 44 intersect at intersection 40. First road 42 includes northbound first road drivers 46 and first road traffic light 52. Second road 44 includes eastbound second road drivers 48 stopped at eastbound second road traffic light 54 and westbound second road drivers 60 stopped at westbound second road traffic light 62. In this particular example, the angle (α) at which first road 42 and second road 44 intersect is 90°, although the angle may vary. Northbound first road drivers 46 are proceeding along first road 42 through a green traffic light 52. Meanwhile, second road eastbound 48 and westbound 60 drivers are looking at green traffic light 52 controlling northbound traffic on first road 42. Conventional traffic lights have wide viewing angles (between about 90 and about 120 degree viewing angles). Consequently, both second road eastbound 48 and westbound 60 drivers can see traffic light 52. One or both of second road eastbound 48 and westbound 60 drivers may attempt to guess when traffic light 52 will turn red and may immediately progress into intersection 40. If one or both of second road eastbound 48 and westbound 60 drivers guesses wrong, an accident may occur. Further, if a northbound driver 46 on first road 42 runs a red light, there is an increased risk of a vehicular collision occurring at intersection 40. [0028] The inventor of the present application recognized that the risk of an accident occurring in the scenario shown in FIG. 3A could be reduced by narrowing the viewing angle of traffic signal light 52. FIG. 3B is a schematic drawing of intersection 40 including improved traffic lights 52, 54, and 62 having narrowed viewing angles. The narrowed viewing angle of traffic light 52 reduces or eliminates the ability of one or both of second road eastbound 48 and westbound 60 drivers to see the color of traffic light 52. Consequently, each driver at intersection 40 is forced to wait until their designated traffic light turns green. This minimizes or reduces the risk that one or more drivers will try to guess when their light will turn green. Use of the narrowed viewing angle traffic lights of the present application eliminates the ability of a driver stopped at a red light to watch the light that relates to the intersecting road and thereby ensures that each driver waits until his/her designated light turns green before proceeding through the intersection. [0029] A third drawback of conventional traffic lights often occurs during bright, sunny conditions when most traffic lights have reduced contrast due to glare. A result of the reduced contrast and glare is that all traffic control signals (red, yellow, and green) appear to be illuminated, causing driver confusion as to whether the driver should proceed through the intersection or stop. Some drivers, unsure what to do, slam on their brakes, causing the person behind them to rear-end them. Some drivers, believing that their light is green when it is actually red, proceed through the intersection and collide with another vehicle. Alternatively, a driver may proceed through an intersection erroneously believing that his/her light is green and injure a pedestrian who is crossing the intersection. In summary, the risk of many types of vehicular or pedestrian collision and/or accident greatly increase when drivers cannot determine quickly and accurately whether their designated traffic light is green, yellow, or red.

[0030] One attempt to reduce the ambient glare involves including a cone on the traffic light. The cone preferably includes a reflective internal surface to ensure that none of the light emitted by the light source is absorbed by the cone. While the cone may reduce some of the ambient glare during the day, the cone does not minimize glare in the evenings or at night when the light reflected from the cone is pronounced at high viewing angles. Further, in many instances, the cone does not adequately reduce glare during bright and sunny conditions because of the light reflected from the internal surface of the cone.

[0031] The inventor of the present application recognized that some or all of these drawbacks could be improved by narrowing the viewing angle of a traffic light. Further, the inventor of the present application recognized that some or all of these drawbacks could be improved by providing a traffic light with reduced glare properties. [0032] The inventor of the present application also recognized that including a light control film and BEF in a traffic light may provide benefits such as, for example, a narrowed viewing angle and/or reduced glare and/or increased contrast and/or increased brightness. The following examples show exemplary traffic light constructions that may provide one or more of the above-mentioned benefits.

[0033] The inventor of the present application recognized that the inclusion of a light control film in a traffic light may be desirable. Light control films reduce glare, increase contrast, and reduce viewing angle. Light control films can be structured or unstructured, and the use of either is within the present inventor's concept. A cross-sectional view of an exemplary structured light control film is shown in FIG. 4. Light control film 90 includes a substrate layer 92 that is light transmissive and a light angle limiting layer 94 including alternating light transmitting portions 96 and light absorbing portions 98. One exemplary commercially available light control film is 3M Privacy Film™ manufactured by 3M Company of St. Paul, Minnesota. Exemplary light control films are described, for example, in U.S. Patent Nos. 5,993,940; 6,800,378; 6,398,370; and U.S. Patent Application No. 11/621,730. [0034] Light emitted by a light source passes through substrate layer 92 and then through light angle limiting layer 94. A portion of the light passing through light angle limiting layer 94 is absorbed by light absorbing portions 98 and a portion is transmitted by light transmitting portions 96. Consequently, less light exits light control film 90 than was initially incident on substrate layer 92. Light control films having different degrees of light transmittance are commercially available, so the user can select the amount of light transmittance desired for the particular application. The degree of light transmittance shown in FIG. 4 is merely exemplary. Further, the viewing angle can be controlled by the user. For example, altering the aspect ratio and aperture of the light absorbing and light transmitting components of the light control film can change the viewing angle from 10° to 120°.

[0035] Because light control films include a light absorbing portion, a traffic light including a light control film will have decreased brightness. This is because less light exits the light control film than is initially incident upon the light control film. The inclusion of a single layer of light control film results in an effective transmission of 64.9% (the light intensity without the light control film present has assumed to be 100% at a viewing angle normal to the light control film). Consequently, the brightness is reduced by approximately 35%.

[0036] One method of maintaining the original brightness of the traffic light involves adding one or more layers of brightness enhancement film (BEF) to the traffic light. Structured BEFs narrow viewing angles and increase brightness by recycling light. A cross-sectional view of an exemplary structured BEF is shown in FIG. 5. BEF 80 includes a substrate layer 82 and a corrugation layer 84 including multiple prismatic elements 86. Substrate layer 82 and corrugation layer 84 should be light transmissive, as light emitted by a light source passes through substrate layer 82 and then through corrugation layer 84. Unlike other BEF applications where the horizontal viewing angle is critical for an image to be viewed, it may be preferable in the applications described herein to align the BEF such that the horizontal viewing angle is significantly restricted while maintaining a large vertical viewing angle. This is achieved by placing BEF in an unconventional orientation to obtain a large vertical viewing angle. This is preferred to ensure that drivers close to or far from the traffic light can see the traffic light as long as they are in the designated traffic lanes defined by the viewing angle. Exemplary commercially available BEFs include those made by 3M Company of St. Paul, Minnesota, such as the BEF sold under the trade name Vikuiti™. Exemplary BEFs are described, for example, in U.S. Patent Nos. 6,760,157; 7,220,026; 5,175,030; and 5,183,597.

[0037] Some examples of a traffic light including a light control film and a BEF are provided below.

[0038] EXAMPLE 1

[0039] An exploded view of one exemplary embodiment of an improved traffic light 200 is shown in FIG. 6. A light source 202 includes multiple lights, here shown, for example, as LEDs 204, that are positioned on a reflective surface 206. Fitted onto, into, around, or adjacent to light source 202 is a cone 210 having a first annulus 212 positioned directly adjacent to light source 202 and a second annulus 214 positioned a distance d from light source 202. The inner surface of cone 210 may include a reflective material. Cone 210 is shown as having first and second annuluses 212 and 214 that are about 90° to the normal. A layer of BEF 220 is positioned between light source 202 and a layer of light control film 230. A light ray emitted by LEDs 204 is incident upon a first major surface 222 of BEF 220, propagates through the thickness of BEF 220, and exits a second major surface 224 of BEF 220 before being incident upon a first major surface 232 of light control film 230, propagating through the thickness of light control film 230, and exiting a second major surface 234 of light control film 230.

[0040] The arrangement and details shown in FIG. 6 are merely exemplary. For example, one or both of BEF 220 and light control film 230 may be positioned closely adjacent to light source 202, may be positioned anywhere within cone 210, or may be positioned adjacent second annulus 214 of cone 210 such that light control film 230 is spaced a distance d from light source 202. Also, light control film 230 may be structured or unstructured. Additionally, light source 202 may include more or fewer LEDs 204 or may include alternative sources of light such as, for example, one or more halogen bulbs, anbaric bulbs, incandescent bulbs, or solid state light sources other than LEDs. Further, cone 210 is shown as having first and second annuluses 212 and 214 at angles of approximately 90° to the normal; these angles may vary. Cone 210 may, alternatively, be absent. Also, traffic light 200 may include a diffuser or a Fresnel lens to homogenize and collimate the light, and may include multiple layers of one or both of BEF 220 and light control film 230.

[0041] EXAMPLE 2

[0042] An exploded view of another exemplary embodiment of an improved traffic light 250 is shown in FIG. 7. A light source 252 includes multiple lights, here shown, for example, as LEDs 254, that are positioned on a reflective surface 256. Fitted onto, into, around, or adjacent to light source 252 is a cone 260 having a first annulus 262 positioned directly adjacent to light source 252 and a second annulus 264 positioned a distance d from light source 252. The inner surface of cone 260 may include a reflective material. Cone 260 is shown as having first annulus 262 approximately 90° to the normal and second annulus 264 approximately 120° to the normal. A layer of cross-BEF 270 is positioned between light source 252 and a layer of a light control film 280. A light ray emitted by LEDs 254 is incident upon a first major surface 272 of cross-BEF 270, propagates through the thickness of cross-BEF 270, and exits a second major surface 274 of cross-BEF 270 before being incident upon a first major surface 282 of light control film 280, propagating through the thickness of light control film 280, and exiting a second major surface 284 of light control film 280.

[0043] The arrangement and details shown in FIG. 7 are merely exemplary. For example, cross-BEF 270 and light control film 280 may be positioned closely adjacent to light source 252, may be positioned anywhere within cone 260, or may be positioned adjacent second annulus 264 of cone 260. Also, light control film 280 may be structured or unstructured. Additionally, light source 252 may include more or fewer LEDs 254 or may include alternative sources of light such as, for example, one or more halogen bulbs, anbaric bulbs, incandescent bulbs, or solid state light sources other than LEDs. Further, cone 260 is shown as having first annulus at an angle of approximately 90° to the normal and second annulus 264 at an angle of approximately 120° to the normal; these angles may vary. Alternatively, cone 260 may be absent. Also, traffic light 250 may include a diffuser or a Fresnel lens to homogenize and collimate the light, and may include multiple layers of one or both of cross-BEF 270 and light control film 280.

[0044] EXAMPLE 3 [0045] An exploded view of another exemplary embodiment of an improved traffic light 300 is shown in FIG. 8. A light source 302 includes a single incandescent bulb 304 positioned on a reflective surface 306. Fitted onto, into, or around light source 302 is a cone 310 having a first annulus 312 positioned directly adjacent to light source 302 and a second annulus 314 positioned a distance from light source 302. The inner surface of cone 310 may include a reflective material. Cone 310 is shown as having second annulus 314 approximately 120° to the normal. A color filter 320 is positioned between light source 302 and a layer of BEF 330. BEF 330 is adjacent to a layer of light control film 340. A light ray emitted by LEDs 304 is incident upon a first major surface 322 of color filter 320, propagates through the thickness of color filter 320, and exits a second major surface 324 of color filter 320 before being incident upon a first major surface 332 of BEF, propagating through the thickness of BEF 330, and exiting a second major surface 334 of BEF before being incident on a first major surface 342 of light control film 340, propagating through the thickness of light control film 340, and exiting a second major surface 344 of light control film 340.

[0046] The arrangement and details shown in FIG. 8 are merely exemplary. For example, color filter 320, BEF 330, and light control film 340 may be positioned closely adjacent to light source 302, may be positioned anywhere within cone 310, or may be positioned adjacent second annulus 314 of cone 310 such that light control film 340 is spaced a distance from light source 302. Also, light control film 340 may be structured or unstructured. Additionally, light source 302 may include more incandescent bulbs 304 or may include alternative sources of light such as, for example, one or more halogen bulbs, anbaric bulbs, incandescent bulbs, or solid state light sources such as, for example, LEDs. Further, cone 310 is shown as having second annulus 314 at an angle of 120° to the normal; this angle may vary. Alternatively, cone 310 may be absent. Also, traffic light 300 may include a diffuser or a Fresnel lens to homogenize and collimate the light, and may include multiple layers of one or both of BEF 320 and light control film 340. [0047] The inclusion of a single layer of light control film and a single layer of BEF narrows the horizontal viewing angle to approximately 60° (or a ±30° viewing cone) while maintaining a large vertical viewing angle of about 175° (or a ±87.5° viewing cone). [0048] At an angle normal to the light control film, the inclusion of a single layer of light control film and a single layer of cross-BEF results in an effective transmission of 136.5%. This represents a 36.5% increase in brightness.

[0049] The inclusion of a single layer of light control film and a single layer of BEF results in an effective transmission of 99.8% at an angle normal to the light control film. In summary, the inclusion of a single layer of BEF and a single layer of light control film narrowed the horizontal viewing angle from greater than 120° to about 60° (or a ±30° viewing cone) and effectively maintained the brightness (99.8% of the original intensity). Also, the construction maintains a wide vertical viewing angle of about 175°. These results show that the use of a light control film and BEF effectively narrows the horizontal viewing angle without sacrificing significant traffic light brightness or the vertical viewing angle.

[0050] The inventor of the present invention also realized that the brightness of a traffic light could be enhanced by including one or more layers of BEF in a traffic light. The following examples describe some exemplary embodiments of these improved traffic lights.

[0051] EXAMPLE 4

[0052] An exploded view of another exemplary embodiment of an improved traffic light 400 is shown in FIG. 9. A light source 402 includes multiple lights, here shown, for example, as LEDs 404, that are positioned on a reflective surface 406. Fitted onto, into, around, or adjacent to light source 402 is a cone 410 having a first annulus 412 positioned directly adjacent to light source 402 and a second annulus 414 positioned a distance d from light source 402. The inner surface of cone 410 may include a reflective material. Cone 410 is shown as having first and second annuluses 412 and 414 that are 90° to the normal. At least one layer of a BEF 420 is positioned within or adjacent to cone 410 such that light rays emitted by LEDs 404 are incident upon a first major surface 422 of BEF 420, propagate through the thickness of BEF 420, and exit a second major surface 424 of BEF 420.

[0053] The arrangement and details shown in FIG. 9 are merely exemplary. For example, BEF 420 may be positioned closely adjacent to light source 402, may be positioned anywhere within cone 410, or may be positioned adjacent second annulus 414 of cone 410. Additionally, light source 402 may include more or fewer LEDs 404 or may include alternative sources of light such as, for example, a halogen bulb, an incandescent bulb, an anbaric bulb, or another type of solid state light source. Further, cone 410 is shown as having first and second annuluses 412 and 414 that are 90° to the normal; these angles may vary. Also, if light source 402 an incandescent bulb, the traffic light 400 may include a colored filter (not shown). Also, traffic light 400 may include a diffuser or a Fresnel lens to homogenize and collimate the light. Multiple layers of BEF may be used.

[0054] EXAMPLE 5

[0055] An exploded view of another embodiment of an improved traffic signal light 450 is shown in FIG. 10. A light source 452 includes a single incandescent bulb 454 that is positioned on a reflective surface 456. Fitted onto, into, or around light source 452 is a cone 460 having a first annulus 462 positioned directly adjacent to light source 452 and a second annulus. The inner surface of cone 460 may include a reflective material. Second annulus 464 of cone 460 is shown as being 120° to the normal. A color filter 470 is positioned between light source 452 and a layer of BEF 480. Light rays emitted by incandescent bulb 454 are incident upon a first major surface 472 of color filter 470, propagate through the thickness of color filter 470, and exit a second major surface 474 of color filter 470 before being incident on a first major surface 482 of BEF 480 propagating through the thickness of BEF 480, and exiting a second major surface 484 of BEF 480. [0056] The arrangement and details shown in FIG. 10 are merely exemplary. For example, one or both of color filter 470 and BEF 480 may be positioned closely adjacent to light source 452, may be positioned anywhere within cone 460, or may be positioned adjacent to second annulus 464 of cone 460. Additionally, light source 452 may include multiple incandescent bulbs 454 or may include alternative sources of light such as, for example, one or more halogen bulbs, anbaric bulbs, or solid state light sources including, but not limited to, LEDs. Further, cone 460 is shown as having second annulus 464 at an angle of 120° to the normal; this angle may vary. Also, traffic light 450 may include a diffuser or a Fresnel lens to homogenize and collimate the light. Multiple layers of BEF may be used.

[0057] The inclusion of a single layer of BEF results in an effective transmission of 163% at angles close to the normal of the traffic control film. These results show that the use of BEF in a traffic light can increase the brightness by approximately 63%. The inclusion of a single layer of BEF narrows the horizontal viewing angle from greater than 120° to about 80° (or about ± 40° horizontal viewing cone), while maintaining a wide vertical viewing angle of about 175°.

[0058] It is not obvious or intuitive to include light control films in a traffic light because light control films undesirably decrease the brightness. Further, it is not obvious or intuitive to include light control films or BEF in a traffic light because these films can add expense to the traffic light. However, the present inventor discovered that the presence of one or both of these films may decrease the total cost of the traffic light, since their presence may obviate the need for other components, such as, for example, the cone, a traffic light grid, or the Fresnel lens. The following examples show that certain traffic signal components can be omitted from traffic signals when a light control film and a BEF are present. The following examples also show that the term traffic lights or traffic signal systems as used in the present application may include traffic signals that, for example, include indicia, such as, for example, patterns, graphics, designs, or alphanumeric letters and numbers.

[0059] EXAMPLE 6

[0060] FIG. 11 is an exploded view of another exemplary embodiment of an improved traffic light 500. A light source 502 includes multiple lights, here shown, for example, as LEDs 504 that are positioned on a reflective surface 506. At least one layer of BEF 520 is positioned such that a light ray emitted by LEDs 504 is incident upon a first major surface 522 of BEF 520, propagate through a thickness of BEF 520, and exit a second major surface 524 of BEF 520 before being incident upon a first major surface 542 of a light control film 540, propagating through a thickness of light control film 540, and exiting a second major surface 544 of light control film 540. Traffic signal 500 includes a indicia 548. Indicia 548 may be formed in any way known to those having skill in the art. For example, LEDs may be arranged or colored to form an indicia 548 in traffic signal 500. Alternatively, the pattern may be a separate patterned film or layer 600, as is shown in FIG. 12. The presence of BEF 520 and light control film 540 eliminates the need for a steel light control grid, which is heavy and subject to degradation based on weather and time. [0061] The arrangement and details shown in FIGS. 11 and 12 are merely exemplary. Light control film 540 may be structured or unstructured, and multiple layers of the light control film 540 or BEF 520 may be used. Additionally, light source 502 may include more or fewer LEDs 504 or may include alternative sources of light such as, for example, a halogen bulb, an incandescent bulb, an anbaric bulb, or another type of solid state light source. If light source 502 is an incandescent bulb, traffic light 500 may include a colored filter. Also, traffic light 500 may include a diffuser or a Fresnel lens to homogenize and collimate the light.

[0062] Existing traffic lights may be retrofit with the one or more layers of the films described above. New traffic lights may be made including these films. [0063] One or more embodiments of the improved traffic control system of the present application reduce the risk of an accident occurring by narrowing the viewing angle, reducing the glare, increasing the contrast, and combinations thereof. These embodiments may, for example, facilitate signal differentiation for motorists who are driving in sunny conditions when glare from the sun can make detection of the traffic control signal that is illuminated challenging.

[0064] Those having skill in the art will appreciate that many changes may be made to the details of the above-described embodiments without departing from the underlying principles thereof. The scope of the present application should, therefore, be determined only by the following claims.

Claims

What is claimed is:

1. A traffic light, comprising: a light source that emits a light ray; and at least one layer of a brightness enhancement film and at least one layer of a light control film positioned such that the light ray propagates through the brightness enhancement film and the light control film.

2. The traffic light of claim 1, in which the brightness enhancement film is positioned between the light source and the light control film.

3. The traffic light of claim 1, further including a cone having a reflective inner surface and positioned such that a first annulus is adjacent to the light source and the second annulus is positioned a distance from the light source.

4. The traffic light of claim 3, in which the at least one layer of brightness enhancement and the at least one layer of light control film are positioned within the cone.

5. The traffic light of claim 3, in which the at least one layer of light control film is positioned adjacent to the second annulus.

6. The traffic light of claim 1, including multiple layers of the brightness enhancement film.

7. The traffic light of claim 1, including multiple layers of the light control film.

8. The traffic light of claim 1, in which the viewing angle is less than about 90°.

9. The traffic light of claim 1, in which the viewing angle is less than about 60°.

10. The traffic light of claim 1, in which the viewing angle is less than about 30°.

11. The traffic light of claim 1 , further including a diffuser.

12. The traffic light of claim 1 , in which the light source is one of an incandescent light, a solid state light source, an anbaric bulb, or a halogen bulb.

13. The traffic light of claim 1, in which the light source includes multiple LEDs.

14. The traffic light of claim 1 , further including a color filter and in which the light source is an incandescent bulb.

15. The traffic light of claim 1, in which the brightness enhancement film is a structured brightness enhancement film.

16. The traffic light of claim 1, in which the brightness enhancement film has a one- dimensional prism structure.

17. The traffic light of claim 15, in which the one-dimensional prism structure is aligned in a vertical plane of the traffic light.

18. The traffic light of claim 1, in which the at least one layer of the light control film includes a one-dimensional light absorbing structure.

19. The traffic light of claim 17, in which the one-dimensional light absorbing structure of the light control film is aligned in a vertical plane of the traffic light.

20. A traffic light, comprising: a light source that emits a light ray; at least one layer of a brightness enhancement film; and at least one layer of a light control film; wherein the brightness enhancement film is positioned between the light source and the light control film.