Patent Application
20190242550
The present invention generally pertains to lighting devices for use on a motor vehicle, and more specifically, interior and exterior lighting devices having light emitting diodes.
Light emitting diodes (LEDs) are known to provide improved optical efficiency over conventional forms of lighting, and are widely used in automotive applications. Despite their advantages, however, LEDs provide low uniformity in the output of light. In particular, individual LEDs provide a Lambertian distribution of light, such that the intensity of light is greatest immediately above the LED but diminishes when viewed from an angle.
Many automotive lighting manufacturers attempt to achieve a homogenous lit appearance using Fresnel lenses alone or in combination with a scattering element, such as a scattering film or a textured lens. However, conventional solutions provide a segmented lit appearance due to a variety of factors. For example, a segmented lit appearance is often attributed to the difference in luminance between the bull's eye, the dioptric, and the catadioptric regions of a Fresnel lens, which drives the need of a very deep device to allow the maximum light to mix, and/or the use of expensive scattering films.
It would therefore be beneficial to provide an improved lighting device which generates a homogenous light distribution across an illuminated area. In particular, it would be beneficial to provide improved control of light uniformity without unduly adding expense or complexity to a lighting device having one or more LED light sources.
A vehicle lighting device for providing a homogenous lit appearance is provided. In one embodiment, the vehicle lighting device includes an array of LED light sources, a lens assembly having a collimator lens, an inner lens, and an outer lens, and a housing to maintain the lens assembly in fixed relation relative to the array of LED light sources. The collimator lens includes two sections, a light incoupling section and a light outcoupling section, to redistribute light with generally uniform intensity. In addition, the collimator lens includes a central geometry to manage high intensity light from directly above the LEDs and a lateral geometry to manage low intensity light that is offset from the LEDs, such that the light output from the LEDs exits the lens assembly with a homogeneous lit appearance.
In another embodiment of the vehicle lighting device, the collimator lens is formed of a light transmissive material and includes an upper lens section, a lower lens section, and a central lens section. The upper lens section is integrally formed with the central lens section and emits incident light from the array of LED light sources by internally reflecting the incident light at an upper reflection surface. The lower lens section is integrally formed with the central lens section and emits incident light from the array of LED light sources by internally reflecting the incident light at a lower reflection surface. The central lens section includes a planar light receiving surface and a light emitting surface that defines a Fresnel lens. The collimator lens in this embodiment is symmetrical about a horizontal plane of symmetry that is perpendicular to the planar light receiving surface of the central lens section. Light emitted by the array of light sources emerges through the collimator lens as collimated light and is projected through the outer lens.
In these and other embodiments of the vehicle lighting device, the array of LED light sources are powered by an on-board power supply and include monochromatic or RGB LEDs. The inner lens directs light toward the outer lens, which is optionally a color filter. The inner lens and the outer lens optionally include a textured surface comprising reflex pins. The lighting device can be manufactured as a head lamp or a rear combination lamp, among other applications, to generating a lighting function forward or rearward of the vehicle. The lighting device is also well suited for other applications, such as interior lighting for heavy duty trucks, without requiring expensive scattering films and is achieved with a housing of reasonable depth.
These and other advantages and features of the invention will be more fully understood and appreciated by reference to the drawings and the description of the current embodiments.
A lighting device in accordance with the current embodiments is depicted in
The array of light sources 12 includes a plurality of LEDs disposed on a substrate, for example a printed circuit board (PCB) 24. In the illustrated embodiment, the plurality of LEDs 12 include five LEDs that are spaced apart from each other along a longitudinal axis of the PCB 24. The plurality of LEDs 12 are arranged in a line along the longitudinal axis of the PCB 24 and are set back from the collimator lens 18 such that no portion of the collimator lens 18 overlies the plurality of LEDs 12. The plurality of LEDs can include monochromatic LEDs in some embodiments, while in other embodiments the plurality of LEDs can be RGB LEDs. The plurality of LEDs receive power from a DC power supply, optionally an onboard DC power supply, while in other embodiments the DC power supply is external to the lighting device 10.
As noted above, the lens assembly 14 includes a collimator lens 18, an inner lens 20, and an outer lens 22. As shown in
More specifically, the plurality of LEDs 12 radiate light according to a Lambertian light distribution, such that the intensity of LED light varies in proportion to the cosine of the angle between the normal direction and the direction of incident light. The collimator lens 18 is positioned relative to the PCB 24 such that it collimates the Lambertian light distribution from the plurality of LEDs 12. Referring to
The outcoupling section 30 of the collimator lens 18 is further depicted in
Collectively, the incoupling section 28 and the outcoupling section 30 cooperate to define a collimator lens 18 having an upper lens section 60, a lower lens section 62, and a central lens section 64, each being shown in
As noted above in connection with
These and other embodiments of the invention provide a low-cost, highly efficient lighting device 10 for generating a homogenous lit appearance with reasonable depth and low cost for exterior lighting applications and interior lighting applications, such as ambient lighting. The collimator lens 18 and the inner lens 20 distribute light uniformly across a wide area, and the outer lens 20 functions as an enclosure while also providing a color filter. The collimator lens 18 can be manufactured with optical grade materials according to low cost extrusion techniques, without requiring expensive scattering films or greater depth for further Fresnel elements.
The above description is that of current embodiment of the invention. Various alterations and changes can be made without departing from the spirit and broader aspects of the invention. This disclosure is presented for illustrative purposes and should not be interpreted as an exhaustive description of all embodiments of the invention or to limit the scope of the claims to the specific elements illustrated or described in connection with these embodiments. Any reference to elements in the singular, for example, using the articles “a,” “an,” “the,” or “said,” is not to be construed as limiting the element to the singular.
This application claims the benefit of U.S. Provisional Application 62/626,775, filed Feb. 6, 2018, the disclosure of which is hereby incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62626775 | Feb 2018 | US |
