Patent Grant
6850095
This invention relates generally to an efficient light collection assembly for use with a light emitting source and, more specifically to a projector optic assembly that defines and projects a high gradient beam pattern. The assembly according to the present invention will find utility in vehicle lighting systems, as well as in a variety of non-automotive illumination applications.
It is known to use light emitting sources, including light emitting diodes (LEDs), Lambertian emitters, 2π emitters, and fiber optic light guide tips, in a variety of applications, including, but not limited to, vehicular applications. With regard to LED sources, these sources are increasingly finding use in automotive, commercial, and general lighting applications since their light outputs have increased exponentially and their costs have fallen significantly over the past few years. LEDs are attractive due to their small size and the fact that they consume less power relative to incandescent light sources. The popularity of LEDs as light sources is expected to continue and increase as their potential benefits are further developed, particularly with respect to increased light output.
Today's LEDs come in different sizes and different emitting cone angles, ranging from 15 degrees (forward emitting or side emitting) to 180 degrees (hemispherical emitting). An emitting cone angle is typically referred to as 2φ . It is therefore very important to construct efficient light collection assemblies to harness the maximum possible light output from LEDs and to direct it in a predetermined controlled manner.
For particular applications, one such being a low beam headlight, it is important to project a high gradient beam pattern, such as an automotive low beam hot spot or cutoff, but not limited to these. High gradient beam patterns have a defined beam pattern outline with varying degrees of light intensity within the beam pattern outline.
Thus, there is a need in the lighting systems field to provide an improved light collection device that can be used with any type of LED to direct the light dispersion in a high gradient beam pattern. This invention provides such an improved LED light collection device.
The present invention addresses these requirements by providing a projector optic assembly that defines and projects a high gradient beam pattern from a light emitting source, such as a LED. The projector optic assembly includes a light pipe and a projector lens, both of which are positioned along the optical axis defined by the light emitting source. The light pipe includes a reflecting region, a funneling region, and a transition plane or coupling region separating these two regions. Positioned at the first end of the reflecting region is a coupling region. The LED may have its own collecting optics, such as a reflector or lens, in which case, there may be simply a planar or concave hemispherical coupling region without any reflecting region. Positioned at the second end of the funneling region is an emitting aperture. The projector lens is spaced apart from the emitting aperture.
Constructed according to the teachings of the present invention, the projector optic assembly redirects light into a high gradient beam pattern regardless of the type of light emitting source being used.
These and other aspects and advantages of the present invention will become apparent upon reading the following detailed description of the invention in combination with the accompanying drawings.
a and 2b are perspective views, with portions cut away, of alternate embodiments of the image shaping light pipe portion of the projector optic assembly seen in
a, 3b and 3c are longitudinal sectional views of alternate embodiments of the image shaping light pipe seen in
Referring to the drawings, a projector optic assembly according to one embodiment of the present invention is shown in FIG. 1 and generally designated at 20. The projector optic assembly 20 includes as its primary components a light pipe 22 and a projector lens 24.
The projector optic assembly 20 is used with a light emitting source 26. Although represented as LEDs in all the figures, the projector optic assembly 20 can be used with a variety of different classes of light emitting sources 26, including, but not limited to, LEDs, Lambertian emitters, 2π emitters, and fiber optic light guide tips. The projector optic assembly 20 can also be used with different types of light emitting sources within a particular class. The projector optic assembly 20 collects, reflects and refracts the light rays from the source 26 such that they exit the projector optic assembly 20 in a high gradient beam pattern.
As shown in
The reflecting region 30 is generally of a conical shape having a first end 36, located toward the source 26, and a second end located at the transition plane 34. The reflecting region 30, while preferred as a conical shape, could be alternatively of a paraboloid shape or ellipsoid shape. In all instances the first end 38 has a first effective cross-sectional diameter which is less than a second cross-sectional diameter of the second end. The reflecting region 30 may further serve to direct the reflected light in such a way as to create a certain intensity distribution within the subsequent regions of the light pipe, this may result in faceting or segmenting of the collection region, either in radial segments, rings, rectangular patches, but not limited to these shapes.
In an alternative embodiment, the LED may have its own collecting optics, such as a reflector or lens. In that situation, the reflecting region may be omitted in favor of a planar or outwardly convex, reflective, coupling region, or transition plane or couping region. Such embodiments are seen in
Referring back to
A transition plane 34 is defined as the area between the reflecting region 30 and the funneling region 32 by the second end of the reflecting region 30 and the first end of the funneling region 32. Preferably, the transition plane 34 has approximately a 15-40 millimeter diameter. Therefore, the reflecting region's second cross-sectional diameter and the funneling region's first cross-sectional diameter are the same and the transition plane 34 is the widest portion of the light pipe 22.
As detailed in both
The coupling region 46 includes two sections: a central concentrating section 48, which is radially centered on the optical axis defined by the light emitting source 26, and an outer section 50, which is radially spaced from the optical axis 28 and which circumferentially surrounds the central concentrating section 48. Preferably, the central concentrating section 48 is generally hyperbolic or hemispherical in shape and outwardly convex. The outer section 50 defines an inwardly concave hemispherical wall that extends radially outward from an outer circumference 52 of the central concentrating section 48.
Further, an emitting aperture 54 is defined in the second end 42 of the funneling region 32. In general, a goal in designing the emitting aperture 54 is to have as small a surface area as possible for the aperture 54. The smaller the surface area of the aperture 54, the more intense the light will be in the projected beam pattern. However, a decreased size of this aperture will normally come at the cost of a wider spread of light from the aperture, causing more light to miss the lens 24; therefore there is a practical limit to the size of the aperture 54.
The shape of the emitting aperture 54 will vary depending on the desired beam pattern. However, for low beam headlights the shape is preferably a rectangular shape having a modified upper edge. One such shape is illustrated in FIG. 4. The outer perimeter of the emitting aperture 54 includes four edges: an upper edge 56; a lower edge 58; a left edge 60; and a right edge 62 (directional references to be used solely as a clarity aid with reference to the orientation of FIG. 4). In this particular embodiment, the upper edge 56 is stepped and includes first and second parallel surfaces 64 and 66, and an angled surface 68 extending between the first and second surfaces 64, 66. It is important to note that surface 68 could be angled at other than 90° relative to surfaces 64 and 66 and that other potential cross sectional shapes for the emitting aperture 54, such as circles, ovals, and squares, could be used, depending on what type beam is to be formed. Further the aperture 54 may be planar or may have a curved surface in order to further shape the intensity distribution to be projected from it.
The projector lens 24 receives the rays of light exiting from the emitting aperture 54 in the desired beam pattern and projects the rays without altering the outline or gradient of the beam pattern. The projector lens 24 could be any type of lens, including but not limited to, a Fresnel lens as shown in
As the rays of light are emitted from the light emitting source 26, they are collected and refracted by the coupling region 46. The coupling region 46 is designed to refract the rays by generally directing them toward the emitting aperture 54. A majority of the rays are refracted directly toward the emitting aperture 54. The other rays are reflected off of the outer walls 70, 72 of either the reflecting region 30, the funneling region 32 or both and are directed toward the emitting aperture 54. The emitting aperture 54 is designed so that all of the, rays that travel through it are refracted into the desired high gradient beam pattern. The high gradient beam pattern travels through the projector lens 24 and is projected over a broader area while retaining its high gradient beam pattern.
Preferably, numerous projector optic assemblies will be used in combination to achieve a desired intensity level and illumination area for a particular application. For example, twenty such assemblies 20 may be collectively used to define all or a portion of an automotive headlamp assembly.
As any person skilled in the art of optics will recognize from the previous detailed description and from the figures and claims, modifications and changes can be made to the preferred embodiments of the invention without departing from the scope of this invention defined in the following claims.
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| Number | Date | Country | |
|---|---|---|---|
| 20040213001 A1 | Oct 2004 | US |
