Patent Application
20100246203
1. Technical Field
The present disclosure relates to systems and methods for exterior projection lighting of vehicles.
2. Background Art
Conventional vehicle exterior lighting has relied upon light sources that are relatively inefficient, such as incandescent or halogen lamps, for example. While these light sources are suitable for many applications, they often present challenges with respect to managing the significant amount of heat generated relative to the illumination provided. In addition, vehicle lighting has evolved from a purely functional role to a combination of function and aesthetics that is very often an important design feature that defines the style and character of the vehicle. In addition to being inefficient, the physical packaging constraints associated with various types of conventional light sources may constrain designers in providing unique styling features while still meeting the photometric requirements for a given lamp function.
Advances in material technology have afforded the opportunity to incorporate more efficient light sources into vehicle lighting applications. Originally used only in signal automotive lighting due to relatively limited luminous flux, semi-conductor light-emitting elements, such as light-emitting diodes (LEDs), have more recently been used as light sources in both reflector-type and projector-type as illumination devices in exterior vehicle lamps. Use of these light sources can provide greater flexibility in packaging to provide a wider variety of aesthetically pleasing lighting designs. However, multiple light sources may be required to meet the photometric requirements. This imposes different design constraints than traditional incandescent light sources.
A system and method for vehicle exterior lighting include a projection lens having an optical axis and an extended semi-conducting light source transversely disposed on a rear side of a back focal point of the projection lens at an angle relative to the projection lens optical axis and facing a reflector that reflects light from the light source toward the projection lens. A curved shade is disposed between the projection lens and the light source generally below the optical axis of the projection lens.
In one embodiment, a method for forward projection lighting of a vehicle includes directing light from a generally flat emitting surface of a semi-conducting light source disposed near a first focal point of a generally ellipsoidal reflector. The light source, implemented by an LED in one embodiment, is angled such that its axis, which is orthogonal to its emitting surface, forms an acute angle relative to the optical axis. The light source directs light generally rearward toward the generally ellipsoidal reflector. The method includes reflecting light from the generally ellipsoidal reflector toward a second focal point of the reflector and through a projection lens to generate a beam pattern extending generally horizontally in front of the vehicle, wherein the projection lens includes a back focal point positioned generally near the second focal point of the reflector.
Another embodiment of the present disclosure includes a vehicle fog lamp that includes a projection lens having a back focal point and an optical axis passing therethrough. A poly-ellipsoidal reflector having a plurality of juxtaposed ellipsoidal facets is disposed on a back side of the projection lens above a plane containing the optical axis. Each facet of the reflector has a corresponding first and second focal point. The plurality of first focal points defines a first focal region of the faceted reflector and the plurality of second focal points defines a second focal region of the reflector. A semi-conducting light source is disposed on a rear side of the back focal point of the projection lens and faces generally away from the projection lens and toward the reflector. The light source is disposed at an acute angle relative to the optical axis within the first focal region of the plurality of reflector facets. A shade curving away from the projection lens and having an apex with an upper edge of the apex disposed within the second focal region of the reflector is disposed between the projection lens and the light source. The shade blocks a portion of reflected light, thus creating a desired cutline in the beam pattern, and it also conceals the light source supporting structure from exterior view. The shade may also include a generally horizontally disposed reflective surface extending away from the projection lens to further improve light collection efficiency.
The light source may include a plurality of monolithic semi-conducting elements, such as a multi-chip, light emitting diodes (LEDs), juxtaposed in a linear array positioned transverse relative to the optical axis at an angle of between about 10 degrees and about 30 degrees depending on the particular application and implementation. In one embodiment, a fog lamp includes a light source implemented by only a single monolithic rectangular array of light-emitting elements positioned at an angle of about 20 degrees relative to the optical axis.
The present disclosure includes embodiments having various advantages. For example, the systems and methods of the present disclosure provide exterior vehicle lighting with high optical efficiency such that the size/number of light sources needed to achieve a desired photometric performance is reduced, which facilitates a low profile lamp package. Reduced lamp packaging size offers greater flexibility for vehicle designers to provide aesthetically pleasing and unique vehicle lighting solutions, and at the same time meets or exceeds photometric requirements for a given forward lighting function.
The above advantages and other advantages and features will be readily apparent from the following detailed description of the preferred embodiments when taken in connection with the accompanying drawings.
As those of ordinary skill in the art will understand, various features of the embodiments illustrated and described with reference to any one of the Figures may be combined with features illustrated in one or more other Figures to produce alternative embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. However, various combinations and modifications of the features consistent with the teachings of the present disclosure may be desired for particular applications or implementations. The representative embodiments used in the illustrations relate generally to exterior projection, also referred to as forward, lighting for a vehicle using a single or small number of semi-conducting light sources, such as one or more LEDs, to provide a desired beam pattern meeting photometric requirements to function as a fog lamp. However, those of ordinary skill in the art may recognize similar applications or implementations with other engine/vehicle technologies.
Referring now to
In the embodiment illustrated in
In one embodiment, light source 38 is implemented by at least one semi-conducting element, such as a light emitting diode (LED). Depending on the particular application and implementation, a plurality of light emitting diodes may be used to meet the photometric criteria of lamp 18. However, embodiments of the present invention may use only a single semi-conducting light emitting source, which may be implemented by a plurality of juxtaposed light emitting elements formed on a monolithic substrate or common die as known in the art. The light emitting elements may be implemented by LEDs, which may or may not have domes, protective transparent coatings, or protective lenses as long as their radiation pattern does not substantially deviate from a Lambertian profile and the LED chip effective lit image is not substantially enlarged by the dome, coating, or lens. However, the LEDs may include a generally rectangular parallelepiped output surface (best illustrated in
With continuing reference to
As also illustrated in
The method may also include blocking a portion of light reflected from reflector 36 using a shade 50 that curves away from projection lens 30 and has an upper edge 52 with at least a portion near the second focal point F2 of reflector 36. Blocking light from reflector 36 may also include blocking light with a curved surface of shade 50 that extends below a horizontal plane containing optical axis 32 and has an upper edge 52 having an apex positioned rearward relative to back focal point 34 of projection lens 30. Various embodiments of the method may include directing light from a light source implemented by a horizontally positioned light emitting diode array, or directing light from a light source implemented by a horizontally positioned diode array having a plurality of monolithic light emitting elements disposed in a linear array on a common die. Depending on the particular desired photometric criteria, the method may include directing light from only a single light emitting diode through each projection lens 30 of a vehicle to provide a desired illumination pattern for vehicle fog lamps.
Light source 138 is positioned near a first focal point of reflector 136 and has an axis 166 normal to the generally flat primary light emitting surface 162 of light source 138 disposed at an acute angle 142 relative to optical axis 132. The value of acute angle 132 may vary by application and implementation, but may preferably be in the range of between about ten (10) degrees and about thirty (30) degrees. In one embodiment of a vehicle fog lamp, angle 142 has a value of about twenty (20) degrees. In another embodiment of a vehicle fog lamp, angle 142 has a value of about twelve (12) degrees. Values may be determined by computer simulation and may vary depending on the desired photometric criteria and the design of the ellipsoidal reflector 136.
As also shown in
A perspective assembly drawing illustrating various components of a vehicle projection lamp according to one embodiment of the present disclosure is illustrated in
Shade 250 may include reflective or non-reflective surfaces 270 and 272. Upper edge 252 of shade 250 curves away from projection lens 230 and has an apex disposed near a second focal point of reflector 236. Shade 250 also extends generally below an optical axis of lens 230. Upper surface 254, generally reflective, extends from upper edge 252 away from lens 230 generally horizontally in a plane parallel to, or coincident with, the optical axis of lens 230.
Generally ellipsoidal reflector 236 may include a reflective surface 244 and a non-reflective surface 246. An opening 248 accommodates light source 238 such that light source 238 is positioned near the first focal point of reflector 236 when lamp 218 is assembled. In one embodiment, light source 238 is centered about the first focal point of reflector 236 and the apex of upper edge 252 along the optical axis of lens 230 is positioned near the second focal point of reflector 236.
Light source 238, which is mounted on a substrate 258, includes a visibly transparent and generally rectangular parallelepiped output coupler having a primary light emitting surface 262 disposed at an acute angle by means of supporting structure 260.
In embodiments having a poly-ellipsoidal reflector, the curvature of shade 350 and 450, in
A computer model representing a lamp having an aspheric projection lens 330, 430 with a diameter of about 45 mm, and a reflector 336, 436 of about 64 mm wide, 23 mm high and about 37 mm deep was used to determine estimated system efficiency. Each reflector 336, 436 was formed by (24) juxtaposed facets or segments of varying size. A transversely positioned LED light source comprised of only a single LED was positioned facing the reflector 336, 436 at an angle of about twenty (20) degrees relative to the optical axis. Computer simulation determined a system optical efficiency of about 52% using a reflective or mirrored upper surface 354 as shown in
Referring now to
As such, the systems and methods of the present disclosure provide exterior vehicle lighting with high optical efficiency such that the size/number of light sources needed to achieve a desired photometric performance is generally reduced, which facilitates a low profile lamp package. Reduced lamp packaging size offers greater flexibility for vehicle designers to provide aesthetically pleasing and unique vehicle lighting solutions that meet or exceed the photometric requirements for a given lamp function.
While the best mode has been described in detail, those familiar with the art will recognize various alternative designs and embodiments within the scope of the following claims. While various embodiments may have been described as providing advantages or being preferred over other embodiments with respect to one or more desired characteristics, as one skilled in the art is aware, one or more characteristics may be compromised to achieve desired system attributes, which depend on the specific application and implementation. These attributes include, but are not limited to: cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. The embodiments discussed herein that are described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics are not outside the scope of the disclosure and may be desirable for particular applications.
