LIGHTING DEVICE WITH LENS, AND MANUFACTURING PROCESS FOR MAKING THE SAME
A lens is disclosed for lighting purposes suited in particular as a lens for a poly-ellipsoid reflector headlamp for imaging the light emitted by a light source and reflected by a poly-ellipsoid reflector for the purpose of producing a predetermined lighting pattern. At least one of the two lens surfaces comprises areas having different optical scattering effects which areas are configured as zones that are transferred from a mold to the surface by a hot-pressing process.
1 . A method of manufacturing a lens having first and second opposite optical surfaces with the first optical surface having a convex shape, comprising the steps of:
melting a glass;
portioning a gob from the melt;
adjusting the temperature of the gob to a viscosity suited for hot-pressing of the gob;
providing a hold having a first generally concave mold surface and a second mold surface for forming said first and second optical surfaces, respectively, of the lens;
feeding the gob into the open mold;
hot-pressing the gob in said mold for generating said lens; and
cooling the lens down to room temperature;
wherein said first mold surface includes areas exhibiting different surface roughness values comprising a central region having a higher mean surface roughness of maximally 10 micrometers and a marginal region having a lower mean surface roughness of maximally 1 micrometer, such that the lens produced by said hot-pressing mold step results in a refractive lens having a corresponding central region on said first optical surface that is configured to provide broader scattering of light emerging therefrom than light emerging from a corresponding marginal region of said first optical surface.
2 . The method of claim 1 , wherein said first optical surface of said lens comprises surface roughness characteristics in said central and marginal regions thereof that are transferred directly from the corresponding regions of said first mold surface during said hot-press molding step without further processing of the lens.
3 . The method of claim 2 , wherein the lens is cooled down in the mold to a temperature below the glass transformation temperature at least at one of its surfaces.
4 . The method of claim 3 , wherein the second optical surface of the lens has a generally planar shape.
5 . The method of claim 1 , wherein the surface roughness of at least the central region of said first mold surface is obtained by sand blasting.