US Patent 11442213 Film-based lightguide with extended coupling lightguide region

In one aspect, a film-based lightguide includes a film with a light emitting region, a plurality of coupling lightguides in a form of an array of strips extended from the body of the film and folded along a fold line, a light mixing region of the film positioned along the film between the plurality of coupling lightguides and the light emitting region, and an extended coupling lightguide region of the coupling lightguides between the fold line and the light mixing region where the plurality of coupling lightguides are not folded. For one or more of the plurality of coupling lightguides, a length along a coupling lightguide between the fold line and a light input end of the coupling lightguide is less than a length of the coupling lightguide in the extended coupling lightguide region.