Colourless lens for turn indicator lamp - has internal prisms preventing reflection of coloured light when illuminated from outside

摘要

The lens prevents the apparent emission of coloured light from a turn indicator lamp when the latter is illuminated by light from outside. The lens (17) is made of colourless material with prisms (21) formed on its inner surface. The edge (9) of the prisms lie in the same plane as the optical axis (13) of lamp (15) and reflector (10). A colour filter (14) surrounds the envelope of the lamp. Light beams (26) entering from outside, and within a defined angle (32-36) strike the prism face (22) at an angle which ensures reflection, and not colour is seen. Some beams (24) outside the defined angles are refracted but strike the reflector (10) at an angle which effectively eliminates the re-emission of coloured light. Only beams (25) in a small angle strike the reflector and are directed at the colour filter giving rise to a visible coloured light.