Patent ID: 8454206

Claim:
A surface light source device comprising: a lamp post comprising a plurality of side surfaces; a plurality of light sources distributed in rows on one or more of the side surfaces of the lamp post; a plurality of first prism sheets arranged around the lamp post; and a plurality of second prism sheets arranged around the first prism sheets; wherein, each of the first prism sheet and the second prism sheet comprises a light incident surface and a light exit surface opposite to the light incident surface; each of the light exit surfaces of the first prism sheet and the second prism sheet comprises a plurality of substantially parallel elongated protrusions, and the longitudinal directions of the elongated protrusions of the first prism sheet and the second prism sheet are substantially perpendicular to each other; the first prism sheets and the lamp post are approximately spaced by a first predefined distance, the second prism sheets and the first prism sheets are approximately spaced by a second predefined distance.