Patent ID: 11879600
Assignee: SIGNIFY HOLDING B.V.
Field: Electrical machinery, apparatus, energy (Electrical engineering)
Classification: CPC F | IPC F

Claim 14:
15. A method of providing a transparent optical structure to a transparent envelope of a LED filament lamp comprising at least one LED filament enclosed by the transparent envelope, wherein the method comprises:
coating an outer surface and/or an inner surface of the transparent envelope, by means of imprinting, etching or photolithography, with a plurality of individually spaced prismatic grooves and/or ridges that are at least partly aligned along a projection of the at least one LED filament on the transparent envelope;
wherein each prismatic groove and/or ridge of the plurality of individually spaced prismatic grooves and/or ridges comprises a refractive facet oriented at a wedge angle between 5 and 50 degrees with a tangent of the envelope at the location of the respective prismatic groove and/or ridge.