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Automotive signalling lamp consisting of two light guides Disclosure Number: IPCOM000016859D
Publication Date: 2003-Jul-21
Document File: 3 page(s) / 140K

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Automotive signalling lamp consisting of two light guides

In automotive signalling lamp configurations (e.g. stop lamp, direction indicator) there are in principal two types known:

• an incandescent lamp in a reflector to form the required beam, and

• LEDs and a light guide with appropriate outcoupling structure.

The drawback of the reflector signalling lamp is that the unit must have a certain size in order to have sufficient intensity in the required angles. The drawback of the known light guide signalling lamp is that the light that enters the light guide will generally be distributed over a larger angle than the angular distribution where a high intensity is required by the legal regulations.

An improved light configuration is possible by a light guide that consists of a collimating part and a light outcoupling part. The difference between the parts is only the geometry; it is simply one piece of plastic (e.g. PMMA, Polycarbonate) It is convenient, but not necessary that both parts have equal size. The part on the light source side is tapered, as given in figure 1 (two possibilities). The half of the light guide remote from the light source has appropriate outcoupling structure as given in figure 1. This outcoupling structure can also be such that the light guide becomes thinner, as given in figure 2. (Figure 2 is represents the configuration in a ray tracing program, so rays are shown too).

Collimation of the light is necessary since usually the light source has a wider light distribution than the legal requirements. The automotive signalling applications require a narrower light distribution than convenient light sources generally have. A typically light distribution of a convenient light source is given in figure 3. For the reason stated above the light guide is also tapered in a direction p...