| 摘要 |
A light guide with input and output faces (2, 3a) is polar-symmetric about the first face (2) and has optical properties such that the angle at which a ray is injected into the first face determines the position at which it leaves the second face (3a), or, if operated in the reverse direction, the position at which the ray enters the second face determines the angle at which the ray leaves the second face. The light guide includes a tapered transparent sheet (3), light from the first face entering at the thick end of this sheet, and the second face forming one face of the tapered sheet. An input /output slab (4) adjoins the tapered sheet (3) for fan-out of light from the first face (2) to the tapered sheet, and a transition region (8) is located between flat and' tapered sheets. The polar symmetry means that light rays always travel in line with the taper direction, which suppresses banding. Preferably the light guide further includes a prism device (20) for folding the light so that the flat and tapered sheets can be folded over each other. A method of making such a prism is also disclosed. |
