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Backlight system with reduced colour mixing length Disclosure Number: IPCOM000008602D
Publication Date: 2002-Jun-26
Document File: 1 page(s) / 36K

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Backlight system with reduced colour mixing length

With use of LEDs as light source for a backlight system separate LEDs for emitting light with red, green and blue colour are used, of which the emitted light must be mixed to get a uniform white coloured backlight. This so-called colour mixing requires a certain mixing length, whether it is done in a wave-guide or some other medium.

By providing a structure on an entrance edge of the wave-guide the optical beam is widened inside the wave-guide. Because the optical beam is widened, there is a better colour mixing over a same mixing length.

In fig 1 light beam divergence in a light mixing wave-guide without (left) and with a structure (right) is illustrated. The detailed structure is shown in fig 2. Other structures as shown in fig 3 can be the result of a further optimisation.

The structure can for instance be applied by the use of a prismatic optical foil (BEF), which is attached to the wave-guide with an optical transparent adhesive.

In a different embodiment, the structure is integrated in the wave-guide by a process of injection moulding.

Preferably the structure when applied on the mixing wave-guide, is accompanied by another structure on the exit edge or plane of mixing wave-guide and reflective surface on the side edges of the wave-guide. This is to prevent at the one hand to trap the mixed light inside the mixing wave-guide and at the other hand to prevent loss of light via the side edges.

                                                Fig. 1                                                                                                                                      Fig. 2

                        Fig 3