| 摘要 |
A planar light device ( 30 ) for emitting light beams, including a light guide plate ( 31 ) having a plurality of diffraction grating units ( 33 ). The light guide plate includes a light-emitting surface ( 313 ), an opposite bottom surface, and a light incident surface ( 311 ) disposed therebetween. A light source ( 32 ) is disposed adjacent to the light incident surface. The diffraction grating units cover the bottom surface of the light guide plate. Each diffraction grating unit is divided into a first part (A) and a second part (B), the first and second parts having different alignment directions from each other.
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