Patent ID: 8511881

Claim:
A light guide plate, comprising: a light emitting surface; a bottom surface, opposite to the light emitting surface; at least one light incident surface, connecting the light emitting surface and the bottom surface; and a plurality of optical units, disposed on the bottom surface, wherein each of the optical units comprises: a first optical microstructure; and at least one second optical microstructure, adjacent to the first optical microstructure, wherein the first optical microstructure is disposed between the light incident surface and the second optical microstructure, and each second optical microstructure comprises: a first surface, inclining towards a side of the light incident surface, wherein a cross-sectional line obtained by cutting the first surface along a direction perpendicular to the light incident surface and the light emitting surface comprises a first cross-sectional line, and the first cross-sectional line is substantially a first inclined straight line; and a second surface, connected to the first surface and inclining away from the side of the light incident surface, wherein a cross-sectional line obtained by cutting the second surface along the direction perpendicular to the light incident surface and the light emitting surface comprises a second cross-sectional line, a first end, adjacent to the bottom surface, of the second cross-sectional line and a second end, away from the bottom surface, of the second cross-sectional line are connected to form a first reference straight line, an acute angle included by the first reference straight line and a normal line of the light emitting surface is α, and α satisfies an equation below: [ 90 ⁢ ° + sin - 1 ⁡ ( sin ⁢ ⁢ ψ n ) ] 2 - 15 ⁢ ° ≤ α ≤ [ 90 ⁢ ° + sin - 1 ⁡ ( sin ⁢ ⁢ ψ n ) ] 2 + 15 ⁢ ° wherein ψ is a desired angle included by an exiting light beam and the normal line of the light emitting surface, n is an index of refraction of the light guide plate, and the first surface of the second optical microstructure is between the first optical microstructure and the second surface of the second optical microstructure.