| 摘要 |
PROBLEM TO BE SOLVED: To reduce uneven luminance in the vicinity of an incident surface by forming plural grooves extended from an emitting surface to a surface opposed to the emitting surface at least in an area opposed to a point light source at the end face of a plate-like member. SOLUTION: The grooves 13 having the same shape are repeatedly formed on an incident surface 12A of a light transmission plate 12 emitting illuminating light. The grooves 13 are formed to be extended from the emitting surface 12C to a rear surface 12B, and repeatedly formed all over the incident surface 12A. Furthermore, the groove 13 is formed by smoothly connecting a pair of inclined surfaces 13A and 13B having a plane inclined to the incident surface 12A to a curved surface 13C of circular-arc shape, and further smoothly connected to the adjacent groove having the similar curved surface 14 of circular- arc shape. The optical path of the illuminating light L made incident on the inclined surfaces 13A and 13B forming the groove 13 is bent by the inclined surfaces 13A and 13B and the light L is distributed to both side surfaces of the plate 12. The insufficient quantity of the light L is compensated and the uneven luminance of the emitting surface is reduced on the plate 12. |
