| 摘要 |
An outer prism light guide surrounds a cover which in turn surrounds a light source. The outer guide is formed of prism light guide wall material having uniform shape in cross-sections perpendicular to a first octature symmetry direction, with its optical center line parallel to the first octature symmetry direction. Surfaces of the wall material are substantially in octature relative to the first octature symmetry direction. A surface normal vector at any point on any internal surface of the material is either substantially parallel or substantially perpendicular to a first notional line extending from the point through and perpendicular to the optical center line. The cover has cylindrical symmetry about the optical center line to intercept a substantial portion of light emitted by the source. The cover is formed of prism light guide wall material, with surfaces of the cover wall material substantially in octature at any point on the cover relative to a second, spatially variable octature symmetry direction, which, at the point, is perpendicular to the first octature symmetry direction; and, perpendicular to a second notional line extending from the cover point through and perpendicular to the optical center line. A surface normal vector at any point on any outer surface of the cover is either substantially parallel or substantially perpendicular to the first octature symmetry direction. The cover is confined to a region sufficiently close to the optical center line to substantially prevent propagation of light rays incident on an inside surface of the cover to and through the light guide wall material.
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