Illuminator Utilizing Multiple Light Guides

1. Field of the Invention

The present invention relates generally to a lighting system for use in vehicle lighting systems, and specifically to, an illuminator, receiving light from a plurality of light guides such as fiber optic light pipes, for use as a high mount stoplight.

2. Description of the Related Art

Typically lighting systems utilize a bulb and parabolic reflector combination. In a bulb and reflector combination, energy supplied to a bulb filament radiates light which is collected by the reflector and reflected in a desired direction to illuminate a specific area. Bulb and reflector systems have several disadvantages including size and space limitations and thermal design properties; i.e., dissipating the heat generated during bulb operation is a concern with a bulb and reflector.

With the advent of light guides such as fiber optics, the ability to use a remote light source and a light guide to transfer light generated at the remote light source to a distant location became available. Several different lighting systems have been developed which utilize a remote light source and plurality of light guides, U.S. Pat. No. 4,811,172 shows such a system. The patent discloses a remote light source transmitting light through a plurality of light guides to a plurality of lenses. The ends of the light guides are positioned adjacent or near a respective reflective element. Additionally, each light guide/reflective element combination requires a respective lens element.

While this approach may have some limited use, it is desirable to reduce the number of lenses and provide a simple, efficient and secure mounting structure for positioning the light guides adjacent or at predetermined position in close proximity to the reflective elements.

Accordingly, the present invention is an illuminator for a lighting system preferably suited for use on a vehicle, such as exterior or interior illumination. The illuminator includes a remote light source providing light through a plurality of light guides to an illuminator block. The light guides terminate in the illuminator block adjacent a plurality of shaped openings. The openings form reflective surfaces which reflect and direct the light emanating from the light guides outward in a predetermined pattern. The present invention may also include forming the external or outer surface of the illuminator block such that the surface acts as a lens to further shape and direct the light beam into the desired or predetermined pattern.

One advantage of the present invention is that an illuminator is provided free of individually air spaced optical elements which are dependant upon precise optical alignment. Once the illuminator profile is developed for a particular use, the present invention results in long term stability in optical alignment, removal of heat and reduced use of costly mechanical fittings. A further advantage of the present invention is that it provides an illuminator which may be shaped to control beam direction or spread.

FIG. 1 is a perspective view of an illuminator according to the present invention illustrated as a high mount stoplight on the rear end of a vehicle.

FIG. 2 is a top view of the illuminator of FIG. 1.

FIG. 3 is a side view of the illuminator of FIG. 1.

FIG. 4 is a side view of the illuminator of FIG. 1 having an alternative surface or lens construction.

FIG. 5 is a side view of the illuminator of FIG. 1 having a complex reflective surface.

FIG. 6 is a side view of the illuminator of FIG. 1 having a second alternative surface or lens construction.

FIG. 7 is a side view of the embodiment of FIG. 6.

Referring now to the drawings and more particularly to FIGS. 1 through 4, an illuminator 10, according to the present invention, is illustrated on a motor vehicle 12. The illuminator 10 is configured as a high mount stoplight mounted adjacent the rear window 13 on the motor vehicle 12. It should be appreciated that the illuminator 10 can also be used for motor vehicle taillights 22 and headlights (not shown).

Referring now to FIG. 2, the illuminator 10 includes a transparent optical block 16 having a plurality of shaped openings 18a-18e. A plurality of equally spaced light guides 14a-14e terminate inside the optical block 16. Typically, the illuminator 10 is of integral construction wherein the block 16 is molded about the light guides 14a-14e. The light guides 14a-14e terminate at determined spaced positions from the shaped openings 18a-18e in the block 16. The shaped openings 18a-18e provide reflective surfaces 24a-24e at the block/opening interfaces which reflect the light rays 26 emanating from the light guides 14a-14e. The light rays 26 are reflected and directed out of the optical block 16 as useable light.

Preferably, the light guides 14a-14e take the form of a ribbon or cable. The light enters the light guides 14a-14e through one of several types of conventional remote light sources. The light rays 26 travel through the plurality of light guides 14a-14e to each respective end. The exit or cone angle of the light exiting the light guides 14a-14e is determined by the entrance angle; i.e., the greater the angle at which light may enter the light guide the greater the exit angle. The size or surface area of the reflective surfaces 24a-24e which the reflect light rays 26 exiting the light guides 14a-14e is determined by the cone angle of the light guides 14a-14e and the position of the reflective surfaces 24a-24e with respect to the ends of the light guides 14a-14e. As illustrated in FIG. 2, the light rays 26 do not exit the end of the light guides 14a- 14e parallel with the axes of the light guides 14a-14e, the rays 26 are reflected off of the reflective surface 24a-24e at varying degrees up to the specified cone angle for the light guides 14a-14e. As shown in FIG. 2, the reflective surfaces 24a-24e are inclined at a 45.degree. angle with respect to the longitudinal axes of the light guides 14a-14e.

It should be appreciated that the reflective surfaces 24a-24e of the shaped openings 18a-18e do not require a mirrorized surface. The light rays 26 emanating from the light guides 14a-14e are reflected at the block/opening interfaces through the principle of total internal reflection. Total internal reflection of the light rays 26 occurs when the incidence angle .THETA. exceeds the critical angle .THETA..sub.c given by the equation .THETA..sub.c =sin.sup.-1 (n.sub.1 /n.sub.2) wherein n.sub.1 is the index of refraction of the surrounding medium, and n.sub.2 is the index of refraction of the coupler medium. As shown in FIG. 2, the shaped openings 18a-18e are simply openings in the block which are filled with air. Therefore, if n.sub.1 =1 and the block is made from a plastic material having an n.sub.2 =1.5 then the critical angle for total internal reflection .THETA..sub.c =42.degree..

If, a polycarbonate material having an n.sub.2 value of 1.59, is used as the material for the block 16, then .THETA..sub.c =39.degree.. Therefore, any light rays 26 having an incident angle .THETA. with respect to the reflective surfaces 24a-24c greater than the critical angle .THETA..sub.c would be totally reflected. While in the present embodiment total internal reflection is used to reflect the light rays 26, it should be appreciated that other known methods for creating a reflective surface may be used, such as an aluminized reflective surface.

It should be appreciated that the shaped openings 18a-18e and corresponding reflective surfaces 24a-24e are spaced in the block at regular intervals such that the reflected light is directed out through the outer surface 28 of the block 16. While the reflective surfaces 24a-24e are disclosed as planar surfaces, many other shapes, see FIG. 5, such as compound or complex surfaces, including paraboloidal or ellipsoidal surfaces can be used to reflect the light rays 26 emanating from the light guides 14a-14e.

As illustrated in FIGS. 4-7, the outer surface 28 of the block 16 may be shaped so as to focus or spread the light rays 26. The outer surface 28 may comprise pillow type optics, fresnel lenses, or simple or compound curvatures. The thickness (t) of the block is also variable depending on the requirement or application. Increasing either the distance from the end of the light guides 14a-14e to the reflective surfaces 24a-24e, or the cone angle of the light guides 14a-14e increases the surface area covered by the light exiting the light guides 14a-14e. Increasing the surface area covered by the light guides 14a-14e correspondingly increases the thickness (t) of the block resulting in a wider light beam.

It should also be appreciated that the light guides 14a-14e may be inclined or positioned adjacent the reflective surface at an angle.

The illuminator 10 may be used for various applications in styling and lighting of a vehicle. The illuminator 10 may be designed to emit light in a specified pattern and at a particular level of intensity and is suitable to provide for illumination of a vehicle such as a stop light, taillight, license plate light and back up light applications. The illuminator may also be used to light the interior of the vehicle whereby a single remote light source provides light to a plurality of light guides each terminating at a different illuminator.