Light extractor for a light guide lamp

DETAILED DESCRIPTION In a first aspect thereof, the invention provides a light extractor for a light guide lamp, characterised in that its useful surface comprises a predetermined distribution of diffusing points and a complementary distribution of reflecting points.
In the present description and attached claims, the expression "useful surface" indicates the surface that, in the use of the light extractor, faces the emission surface of the light guide lamp.
Since the light incident on the reflecting points propagates through reflection, whereas the light incident on the diffusing points is deviated at such angles as to partly exit from the lamp, by controlling the distribution of diffusing points—and thus the complementary distribution of reflecting points—it is possible to control, point by point, the light diffusion properties, on the basis of the desired result when the light extractor is used in the light guide lamp.
Advantageously, the useful surface comprises a reflecting base layer and the predetermined distribution of diffusing points on the reflecting base layer.
In this way, the manufacture of the light extractor is simplified.
Even more preferably, the reflecting base layer comprises the side without micro-prisms of a TIR film.
In particular, the reflecting base layer can consist of the above cited OLF films or optical multilayer films.
In an embodiment, adjacent diffusing points of the predetermined distribution are at a decreasing distance along a main propagation direction from a light inlet end to an opposed end.
Such an extractor, used in a light guide lamp having a single illumination system, provides an uniform illumination along the main propagation direction.
In another embodiment, the distribution of diffusing points is symmetrical with respect to a median axis perpendicular to the main propagation direction.
Such an extractor is particularly useful in light guide lamps having two symmetrical illumination systems at the two ends.
In this case, in a particularly preferred way, adjacent diffusing points of the distribution of points are at a decreasing distance from each end of the extractor to the median axis perpendicular to the main propagation direction