| 摘要 |
PROBLEM TO BE SOLVED: To enhance visibility in both of an illumination lighting time and a non-lighting time by forming a light transmission plate so that intensities of outgoing lights in a direction vertical with respect to the surface of the light transmission plate emitting lights from a light source become smaller than intensities of outgoing lights in a direction oblique with respect to the surface of the light transmission plate. SOLUTION: Protrusions 5 are provided on the surface of a light transmission plate 1 at whose end face 7a point light source 2 is arranged which is in a side opposite to the counter surface of a body to be illuminated 3. Each surface of the protrusions 5 is made to be a face roughly forming the angle of not larger than 30 degrees with respect to a surface parallel with the light transmission plate 1 consisting of transparent material whose refractive index is not smaller than 1.4. Then, when luminous fluxes made incident from the end face 7 form angles of not larger than 45 degrees with respect to the surface parallel with the plate 1, after they repeat total reflections in the plate 1 like light beams 6a, 6b, when the light beams reflected on the respective protrusions 5 become to form angles roughly exceeding 45 degrees with respect to the surface parallel with the plate 1, the plate 1 emits outgoing lights 8 to a direction having an angle θ with respect to a direction vertical with respect to the surface of the plate 1. At this time, intensities of outgoing lights to a direction vertical with respect to the surface of the light transmission plate 1 become smaller than intensities of outgoing lights to a direction oblique with respect to the surface of the light transmission plate 1. |
