Patent Application
20180202630
The present disclosure relates generally to lighting systems and, more particularly, to outdoor lighting systems incorporating a light diffuser to reduce glare.
The use of light emitting diode (LED) based lighting systems has become more commonplace due to their energy savings and significant lifespan. LEDs generate an intense point of light which is generally anisotropic and has a narrow incident beam. The directionality of the light emitted by the LEDs causes excessive glare which can make LEDs very bright and harsh to look at. In some cases, the glare created by LEDs temporarily impairs a person's vision, which makes the use of LEDs for parking lot lamps and street lamps problematic unless proper glare-reducing measures are taken.
An ideal design of an LED lighting system provides sufficient illumination levels on the ground while creating the effect of minimal light at the LED. To help achieve this objective, many LED manufacturers place a primary optic or lens over the semi-conductor element of the LED to create a lambertian light distribution pattern. While this light distribution pattern reduces glare to some degree, some applications, such as roadway lighting, require an even greater amount of glare reduction. In these cases, a secondary optic or lens is placed over each of the LEDs to further distribute the light. Adding the secondary optic, as opposed to modifying the primary optic itself, is preferred because the primary optic is typically installed by the manufacturer and closely integrated with the semi-conductor element of the LED.
The secondary optic typically employs a bubble refraction design that creates a batwing-shaped light distribution pattern in which light rays of greatest intensity extend from a central axis of the secondary optic at a relatively high angle. These high angle light rays, while effective at more evenly illuminating the ground surfaces beneath the luminaire, nevertheless create a significant glare for an individual approaching the luminaire.
To address the high angle brightness of the secondary optic, a tertiary optic or lens is added to diffuse the directional light emitted from the secondary optic. The diffusing characteristic of the tertiary optic disperses light over a larger surface area and thus reduces glare. Known tertiary optics are substantially curved and cover the entire array of the LEDs. As light rays pass through the curved upper ends of the tertiary optic, the light rays are diffracted in the horizontal and upward directions. This results in an undesirable light distribution if the luminaire is to be used outdoors, for example, to illuminate a parking lot or road. It is generally preferred that outdoor luminaries do not emit light in the upward direction because such light tends to exacerbate the problem of light pollution (i.e., the haze of wasted light that envelops many large cities and towns). If the luminaire is configured as a parking lot lamp or street lamp, emitting light in the horizontal direction is also undesirable because doing so may illuminate adjoining properties instead of the intended parking lot surface or road.
Another issue with known curved tertiary optics is that a local minimum or maximum of light intensity is created as the light rays pass through the curvature of the lens. This phenomenon is commonly referred to as pixilation. Pixilation casts shows that can change the look of an illuminated object and potentially create optical illusions.
A need therefore exists for a lighting system incorporating a tertiary optic that reduces glare, and additionally, minimizes light pollution and pixilation.
One aspect of the present disclosure includes a luminaire that includes a plurality of LEDs disposed on a mount surface. The luminaire further includes a light diffuser spaced apart from the plurality of LEDs and including a planar surface facing the plurality of LEDs. The luminaire further includes a reflector surrounding a cavity formed between the light diffuser and the plurality of LEDs. The plurality of LEDs may emit light away from the mount surface toward the planar surface of the light diffuser, whereat a first portion of the emitted light transmits through the light diffuser and a second portion reflects off of the planar surface of the light diffuser to the reflector.
Another aspect of the present disclosure involves a method of distributing light. The method includes emitting light from a first light source towards a planar surface of a light diffuser in a first light distribution pattern such that the emitted light is directly incident upon the planar surface. Additionally, the method includes emitting light from a second light source towards the planar surface of the light diffuser in a second light distribution pattern different than the first light distribution pattern such that the emitted light is directly incident upon the planar surface. The planar surface may have a reflective material coating, such that the emitted light from the first light source and second light source that is directly incident upon the planar surface is directly incident upon the reflective material coating of the planar surface. The method additionally includes scattering a first portion of the light from the first light source and the second light source with the light diffuser, and reflecting a second portion of the light from the first light source and the second light source with the light diffuser. Still additionally, the method includes reflecting the second portion of the light from the first light source and the second light source with a first reflective surface back towards the light diffuser. Furthermore, the method includes scattering the second portion of the light from the first light source and the second light source with the light diffuser.
A further aspect of the present disclosure involves another method of distributing light. The method includes emitting light from a plurality of light sources toward a plurality of lenses, each of the light sources being aligned with a respective one of the plurality of lenses. Additionally, the method converting a first portion of the emitted light into a first light distribution pattern via a first portion of the plurality of lenses, the first light distribution pattern directed toward a light diffuser spaced apart from the plurality of lenses. Additionally, the method includes converting a second portion of the emitted light into a second light distribution pattern via a second portion of the plurality of lenses, the second light distribution pattern having a steep first portion directed toward the light diffuser and a shallow second portion directed toward a reflector surrounding a cavity formed between the light diffuser and the plurality of lenses. Still additionally, the method includes reflecting the light from the shallow second portion with the reflector, the reflected light from the shallow second portion reflected toward the light diffuser. Furthermore, the method includes scattering, with the light diffuser, at least a portion of each of (i) the light from the first light distribution pattern, (ii) the light from the first steep portion of the second light distribution pattern, and (iii) the reflected light from the shallow second portion of the second light distribution pattern.
So configured, the luminaire 10 of the present disclosure advantageously provides sufficient illumination at the ground level while creating the effect of minimal light at the luminaire 10. The luminaire 10 thus minimizes the glare perceived by an individual looking at the luminaire 10. Additionally, the generally planar upper surface of the light diffuser 24 helps evenly distribute the light and thus reduces the effects of pixilation. In addition, the reflector 28 redirects high angle light rays at a more optimal angle so that the light rays exit the luminaire 10 in a generally downward direction. Accordingly, the luminaire 10 prevents the emission of upwardly directed light rays, which tend to cause light pollution, and also prevents light rays from exiting the sides of the luminaire 10 and illuminating objects outside an intended zone of illumination.
Each of the foregoing components of the luminaire 10 and the methods of operating the luminaire 10 will now be described in more detail.
The luminaire 10 is suitable for outdoor use, for example, as a parking lot lamp and/or a street lamp. The housing 12 may be constructed from a durable plastic and/or metal capable of withstanding weather elements such as rain, snow, ice, etc. An arm-like structure 30, which extends from the side of the housing 12, may be used to cantilever the housing from the top of a light pole (not shown). In one embodiment, the housing 12 is arranged approximately (e.g., ±10%) 15-30 feet above the ground. The housing 12 may be pivotally attached to the arm-like structure 30 so that the housing 12 can be easily opened to replace the LEDs 14 or to perform other maintenance-related tasks. As illustrated in
Referring back to
Still referring to
Many of the light rays emitted from the LEDs 14 strike the upwardly facing surface 36 of the light diffuser 24 at a substantial angle. As a result, the upwardly facing surface 36 reflects a portion of the light rays back up into the luminaire 10. In some cases, the upwardly facing surface 36 reflects approximately (e.g., ±10%) 20% of the incident light and transmits about (e.g., ±10%) 80% of the incident light. While there may be some energy losses associated with the reflection, it is generally desirable to reflect the light back up into the luminaire so that the reflector 28 can re-direct the light rays at a more optimal angle, and in a different location, so as to minimize pixilation. The reflection of high angle light rays also helps control the size of the illuminated ground area by limiting the number of light rays that exit the luminaire 10 in the horizontal, or substantially horizontal, direction.
The upwardly facing surface 36 of the light diffuser 24 can be made from a variety of semi-transparent and/or semi-reflective surfaces such as plastic (e.g., acrylic or polycarbonate) or glass. Additionally, the upwardly facing surface 36 may be coated with a material that increases its reflectivity. In some embodiments, the light diffuser 24 is made of material that does not polarize the light.
A downwardly facing surface 38 of the light diffuser 24 is textured so that it scatters the light rays exiting the light diffuser 24. The texture can be formed by a mold having a mild acid etch that is used in an injection molding process to create the light diffuser 24. The scattering effect of the downwardly facing surface 38 substantially reduces glare, and also, creates the effect of a uniformly luminous surface, which is generally considered more aesthetically pleasing than the distinct points of light created by the LEDs 14.
The angle at which the light rays initially strike the upwardly facing surface 36 of the light diffuser 24 is controlled by the shape of the secondary lenses 18a, 18b. As mentioned above, each of the secondary lenses 18a, 18b transforms the light emitted from one of the LEDs 14 into a batwing-shaped light distribution pattern. Generally speaking, a batwing-shaped light distribution pattern possesses at least one peak of light intensity arranged along a conical plane centered about a central axis of the lens. For reasons described below, the secondary lenses 18a associated with the inner cluster 20 of LEDs create a batwing-shaped light distribution pattern that differs from the one created by the secondary lenses 18b associated with the outer cluster 20 of LEDs.
As seen in
As described below in more detail, the double batwing-shaped light distribution pattern 70 of the secondary lens 18b advantageously directs the high angle light rays (i.e., the light rays 66) directly at the circumferential reflective surface 34 of the reflector 28 instead of at the light diffuser 24. Accordingly, the high angle light rays do not first bounce off the light diffuser 24, and then strike the reflector 28, which tends to cause energy losses. Furthermore, the high angle light rays are prevented from exiting the light diffuser 24 in the horizontal direction which might otherwise occur if these light rays were to strike the outer edge of the light diffuser 24 at a shallow angle and then exit the outer edge of the light diffuser 24 in a scattered manner.
Referring to
As illustrated in
A portion of the first incident beam 90 is reflected by the upwardly facing surface 36 of the light diffuser 28 and becomes the first reflected beam 96. Relatively speaking, only a small portion of the first incident beam 90 may be reflected by the upwardly facing surface 36 since the first incident beam 90 strikes the upwardly facing surface 36 of the light diffuser 28 at a relatively steep angle (e.g., 62 may be within the range of 30-40 degree). The remainder of the first incident beam 90 is transmitted through the light diffuser 28 and scattered by the texture of the downwardly facing surface 38 as the first incident beam 90 exits the light diffuser 28. The first reflected beam 96 meanwhile bounces off the circumferential reflective surface 34 of the reflector 28 and then reflects off of the downwardly facing reflective surface 32 of the reflector 28. The first reflected beam 96 is thus redirected back at the light diffuser 28, and exits the light diffuser 28 in a generally downward direction.
With regard to the second incident beam 92, this beam initially reflects off the circumferential reflective surface 34 of the reflector 28 in the downward direction, and then passes through downwardly facing surface 38 of the light diffuser 24 which causes scattering of the beam. One benefit of aiming the second incident beam 92 directly at the circumferential reflective surface 34 of the reflector 28 is that the first incident beam 90 experiences a single reflection prior to exiting the luminaire, and thus is more likely to retain its original intensity. This improves the efficiency of the luminaire 10. Also, aiming the second incident beam 92 at the circumferential reflective surface 34 of the reflector 28 prevents the second incident beam 92 from passing through the outer portion of the diffuser 24 at a shallow angle, which helps prevent unintended illumination of an adjoining property next to the intended area of illumination.
While the present embodiment of the luminaire utilizes LEDs as the light sources, as mentioned above, other embodiments of the luminaire can utilize other light sources such as, e.g., incandescent bulbs, fluorescent bulbs, high-intensity discharge bulbs, etc.
The luminaire of the present disclosure advantageously reduces glare while providing a significant degree of control over the direction of the emitted light, and also, minimizing pixilation and energy losses due to internal reflections. These aspects of the luminaire make it particularly suitable for lighting outdoor areas such as a parking lot or a street, and anywhere else where light pollution is a concern. Additionally, by reducing the effects of pixilation and glare, the luminaire can sufficiently illuminate an area without impairing an individual's vision.
While the present disclosure has been described with respect to certain embodiments, it will be understood that variations may be made thereto that are still within the scope of the appended claims.
This application is a continuation of and claims priority to U.S. application Ser. No. 14/215,853, filed Mar. 17, 2014, which claims priority to and the benefit of U.S. Application No. 61/798,411, filed Mar. 15, 2013. The entirety of each of the foregoing applications is incorporated by reference herein.
| Number | Date | Country | |
|---|---|---|---|
| 61798411 | Mar 2013 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 14215853 | Mar 2014 | US |
| Child | 15922316 | US |
