| 摘要 |
PROBLEM TO BE SOLVED: To do way with brightness irregularity by optical and positioned displacement of a light source, in a surface light source device emitting the light introducing to a light guiding plate from a light incident end surface, from a light emitting surface. SOLUTION: A light source 23 is arranged opposed to a light incident end surface 20 of a light guiding plate 18, and plural optical patterns 32 are formed on the area of the light incident end surface 20 opposed to the light source 23. Each optical pattern 32 is formed uniformly in the thickness direction of the light guiding plate 18, and a period Λ of the plural optical patterns 32 arranged in the width direction of the light incident end surface 20 is set to be 1/n (n=1,2,...) times the width W of the light source 23. And length L of the area where the optical patterns 32 are provided is set to be larger than (W+δ+2h), that is, the sum of the width W of the light source 23, the positioned displacement δ of the light source 23 and two images the distance h from the light source 23 to the light incident end surface 20. |
