| 摘要 |
PURPOSE:To use light from a wire-shaped light source such as fluorescent light to realize the brightness uniform over the entire part by using the surface on the thick side of the wedge of a thin type wedge-like photoconductor consisting of a transparent medium having a specific refractive index as a light incident face and one of the slopes thereof as a reflection face. CONSTITUTION:The surface P5 on the thick side of the wedge of the wedge-like photoconductor 10 having such a shape in which the thickness of the photoconductor 2 decreases on progression of rays is used as the incident face, to which the light is entered from the wire-shaped light source 1. One plane P2 of the slopes having the max. area of the photoconductor 10 is used as the reflection face 2b, then the incident ray changes the progressing direction thereof gradually at every repetition of total reflection on progression of the incident ray. The incident ray exceeds the critical angle of the total reflection in some stage and eventually emits to the outside world from an exit side boundary face 2a. The refractive index (n) of the medium 2 is so determined as to satisfy the conditions 1.25<=n<=1.4 and such medium is combined with the shape of the photoconductor 10 so that the exit positions of respective modes are uniformly dispersed. Furthermore, a light diffusion plate 4 is disposed on the exit side.
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