| 摘要 |
A prism unit has transmitting/totally-reflecting surfaces which cross each other, formed using at least one prism. Light emanating from a light source falls on the prism unit. The light is transmitted or totally reflected from the surfaces according to an angle of incidence at which the light falls on the prism unit. Transmitted light is radiated forwards, while totally-reflected light is directed laterally. A reflecting member is located laterally in order to cover the prism unit, whereby light totally reflected laterally by the prism unit is reflected forwards. In order to constitute the transmitting/totally-reflecting surfaces, a first air layer and a second air layer are formed in the prism unit so to have a substantially uniform width and oppose each other with a plane, which contains a glowing member of the light source and extends forwards, between them.
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