Patent ID: 7753543

Claim:
A prism sheet comprising: a transparent main body having: a first surface, a second surface opposite to the first surface, a plurality of first micro-depressions formed in the first surface and a plurality of second micro-depressions formed in the second surface, wherein the first micro-depressions cooperatively define a plurality of first waved ridges extending along a first direction and a plurality of second waved ridges extending along a second direction substantially perpendicularly intersecting with the first direction; an outline of a cross-section of each micro-depression taken along a plane perpendicular to the first waved ridges is a sinusoidal curve; an outline of a cross-section of each micro-depression taken along a plane perpendicular to the second waved ridges is a sinusoidal curve; each of the second micro-depressions is defined by four connecting inner sidewalls; a transverse width of each inner sidewall progressively decreases with increasing distance from the second surface.