Abstract: An exemplary light guide plate (500) includes: a light incident portion (51) for receiving a light; a light reflecting portion (52) for reflecting the light input through the light incident portion; and a light emitting portion (53) opposite to the light reflecting portion, for outputting the reflected light. The light incident portion includes a first diffractive optical element (512) located thereat. The first diffractive optical element includes a plurality of protrusions (512a) each having a curved surface, with the protrusions being arranged symmetrically opposite to each other across a central axis of symmetry of the first diffractive optical element. The light emitting portion may include a second diffractive optical element (532) located thereat. The second diffractive optical element includes a plurality of elongate protrusions, with the protrusions being arranged symmetrically opposite to each other across a central axis of symmetry of the second diffractive optical element.