| 摘要 |
PROBLEM TO BE SOLVED: To provide a light transmission plate that emits light with uniform brightness. SOLUTION: A light transmission plate 1 has a bottom surface provided with a plurality of prism-like grooves 1c arranged almost in parallel by a given interval facing in the direction perpendicular to the incident light ray from an LED 3 with the notch-shaped slant angle θ. The light transmission plate 1 has one side provided with LED 3, and the other side with a diffusion reflector 5, and the prism surface with a reflector 6. The slant angle θ is determined so that the slant angle θ1 of the slant surface facing LED 3 forms with the slant angle #2 of the slant surface facing the diffusion reflector 5 with the following relationship: θ1>θ2 (≈45 deg.). The primary light emitted from LED 3 into the light transmission plate 1 is reflected at the slant angle θ1, partly emitted from the emitting surface, and the remaining portion being reflected again by the emitting surface 1b. Meanwhile, the secondary light obtained by the light portion passing the light transmission plate 1 and diffusively reflected by the diffusion reflector 5 is reflected at the slant angle θ2 directed to the emitting surface. The light portion scattered by the reflection plate 6 is mixed with the reflected primary and secondary light, uniformly emitted from the light transmission plate 1. |
