Diffraction light guide plate and display device including the same

A diffraction light guide plate comprising:

• a light guide unit configured to guide light;
• an input diffraction optical element configured to diffract light, which is outputted from a light source and inputted to the input diffraction optical element, so as to guide the inputted light on the light guide unit;
• and
• two diffraction optical elements configured to receive the diffracted light from the input diffraction optical element and one-dimensionally expand the received light by diffraction,
• wherein each of the two diffraction optical elements receives the expanded light from the other of the diffraction optical elements and outputs the received light from the light guide unit by diffraction, and there is no region where the two diffraction optical elements overlap each other on the light guide unit,
• wherein each of the input diffraction optical element and the two diffraction optical elements includes linear gratings repeatedly formed at predetermined pitches, and has grating vectors defined as having magnitudes inversely proportional to the pitches of the linear gratings and directions perpendicular to directions in which the linear gratings are orientated, and the sum of the grating vectors of the input diffraction optical element and the two diffraction optical elements is 0, and
• wherein the grating vectors of the input diffraction optical element and those of the two diffraction optical elements have the same magnitude.