1. Field of the Invention
The invention relates to an optical device and an optical module. More particularly, the invention relates to a light guide plate (LGP) and a light source module.
2. Description of the Related Art
A conventional light source module is roughly classified into a direct-type light source module and a side-type light source module. In the side-type light source module, a light guide plate (LGP) guides the light emitted by a light emitting device that is configured at the side of the LGP to the front surface of the LGP, so as to form a planar light source. Given the surfaces of the LGP are smooth, the light entering the side of the LGP is totally reflected by the surfaces of the LGP and thus cannot be emitted from the front surface of the LGP. Hence, etching points or screen printed points are configured on the front or rear surface of the conventional LGP, so as to disrupt the total reflection. However, when the total reflection is disrupted by the etching points or the screen printed points, and the light is able to be emitted from the front side of the LGP, the direction of the light often deviates from the direction of the normal line on the front surface of the LGP. As such, a prism sheet is required to be formed on the LGP to correct the direction of light. Use of the prism sheet, however, leads to an increase in the costs and the consumption of optical energy.
In Taiwan Patent No. 581891 (corresponding to U.S. Pat. No. 6,576,887), a bottom surface of an LGP has a retrieving structure, and the retrieving structure has a front guide surface, a rear surface, and a plateau portion. In Taiwan Patent Application Publication No. 200846731, at least one of the bottom surface and the light emitting surface of the LGP has a plurality of micro-structures. In Taiwan Patent Application Publication No. 200530632, the light guide surface of the LGP that faces the light emitting surface has a plurality of net points, and the net points are recessed in the light guide surface. In Taiwan Patent Application Publication No. 200615614, the bottom surface of the LGP contains irregular rough planes and smooth planes. In U.S. Pat. No. 7,153,017, a light incident surface of an optical deviator contains a prismatic plane. In Taiwan Patent No. I222533 (corresponding to U.S. Pat. No. 6,967,698), a liquid crystal display (LCD) device includes a planar light source device, and the planar light source device includes an LGP and a light emitting portion. In Taiwan Patent No. I282021, an LGP having micro-structures that are arranged on the bottom surface of the LGP in a repetitive manner. In Taiwan Patent No. I296352, an LGP has layers of ring-shaped micro-structures. In U.S. Pat. No. 6,454,452, a bottom surface of an LGP has wedge-shaped grooves. In Taiwan Patent No. M321111, an LGP having regularly arranged micro-structures is disclosed. In U.S. Pat. No. 6,612,722, an LGP having micro-structures is disclosed. In U.S. Pat. No. 6,834,973, a bottom surface of an LGP has reflective micro-structures.