Reflector and a starting sheet material, for forming a reflector

Starting sheet material adapted for forming a reflector for a lighting device, the starting sheet material comprising:

• a flat reflective sheet material shaped as a sector of an annulus bendable into a parabolic reflector or a truncated cone reflector, the flat reflective sheet material comprising a first surface, a second surface, a first edge shaped as a segment of a circle with a first radius and a second edge shaped as a segment of a circle with a second radius, the second radius being smaller than the first radius, a third edge and a fourth edge, the third edge and the fourth edge extending between said first edge and said second edge, wherein
• optical structures are provided on at least a part of at least one of the first surface and the second surface, said optical structures enabling collimation and/or beam shaping of incident light,
• said optical structures being positioned on the flat reflective sheet material along a direction perpendicular to the radial direction of the flat reflective sheet material, and
• wherein said positioning of the optical structures establishes gaps between individual optical structures enabling a portion of light emanating from a light source within the reflector and incident to an individual optical structure to be refracted twice by said individual optical structure before being subsequently reflected at the surface of the flat reflective sheet material.