Lighting unit with variable flood to spot capability - has twin fixed and moving lenses with matching concentric convex and concave prisms enabling selection of light beam

摘要

The lighting unit with parabolic reflector (1) has two plastic or glass lenses (4,6) mounted in front of and co-axial with the reflector (1). The lens (4) nearest the reflector (1) has concentric circular prisms of convex form (5) and is fixed, whilst the front lens (6) has matching concentric prisms of concave form (7) and can move axially over a distance (a). When the two lenses (4,6) are touching a parallel spotlight beam is obtained, whilst a floodlight beam of variable divergence is obtainable as soon as the lenses (4,6) are separated. USE/ADVANTAGE - In pocket torches, shopwindow or theatre lighting. Economic to manufacture and various lighting characteristics are possible by changing prism dimensions or including planar regions in make-up of lens, does not produce dark spots of rings when beam is divergent.