Patent ID: 7458704

Claim:
An optical element comprising: an incident surface on the optical element; and an emitting section formed on an opposite side of the optical element to the incident surface and comprising a plurality of protrusions, wherein when each of the plurality of protrusions is projected onto a reference plane perpendicular to the incident surface to form a reference contour, the reference contour being substantially a trapezoid, wherein when each of the plurality of protrusions is projected onto an orthogonal plane perpendicular to the incident surface and the reference plane to form an orthogonal contour, the orthogonal contour is substantially a trapezoid, the optical element satisfies 1≦( h 2− h 1)/ h 2×100≦35, where h 1 is a height of the reference contour, and h 2 is a height of a triangle formed by extending two legs of the reference contour, and wherein each of the plurality of protrusions comprises: a horizontal surface, and a plurality of slopes formed on respective laterals of the each of the plurality of protrusions and facing each other so that the each of the plurality of protrusions tapers in a direction away from and perpendicular to the incident surface and toward the horizontal surface.