Patent ID: 7357557

Claim:
A light guide plate comprising: a plate member having a light transmitting capability; and a light incidence face which is a side surface of the plate member; wherein the plate member changes a path of light emitted from a light source arranged to face the light incidence face and emits planar illumination light from an upper surface of the plate member onto an object to be illuminated; wherein the light incidence face is formed to have an undulating surface portion defined by a quadratic curve and comprising rounded recessed portions and rounded raised portions interposed between the rounded recessed portions, the recessed portions and raised portions following one another in a longitudinal direction of the light incidence face, and wherein the undulating surface portion is formed by smoothly connecting each of the recessed portions and each of the raised portions alternately, and wherein a surface of each of the rounded recesses and raised portions is formed into a rough light diffusion surface.