| US 7,581,862 B2 | ||
| Light guide element and light unit with light guide element | ||
| Emil Stefanov, Esslingen (Germany); and Stephanie Specht, Stuttgart (Germany) | ||
| Assigned to odelo GmbH, Schwaikheim (Germany) | ||
| Filed on Apr. 04, 2008, as Appl. No. 12/98,023. | ||
| Claims priority of application No. 10 2007 016 923 (DE), filed on Apr. 05, 2007. | ||
| Prior Publication US 2008/0273338 A1, Nov. 06, 2008 | ||
| Int. Cl. F21V 8/00 (2006.01) | ||
| U.S. Cl. 362—555 [362/551; 385/146] | 10 Claims |
| 1. Light guide element (31) whose cross-sectional area continuously widens from a light inlet surface (34) to a light outlet surface (36) at least in areas, characterized by the fact that
the light guide element (31) includes at least one area (38) with a curved directrix (37), in which the curvature of the directrix (37) is constant in this area (38) or in which the curvature of the directrix (37) diminishes with increasing cross section of light guide element (31) in this area (38),
that each line that intersects the light inlet surface (34) penetrates an outer surface (33) of the light guide element (31) outside of the light outlet surface (36) and
that the longest surface line (39) bordering the light guide element (31) in the curved area (38) is longer than the difference of pi and double the largest critical angle of total reflection of the material of light guide
element (31) relative to the material or materials of the surroundings (1) adjacent to the light guide element (31) divided by the maximal actual curvature of the mentioned surface line (39) of light guide element (31).
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