Beam deflector and holographic three-dimensional image display apparatus employing the same

A backlight unit comprising:

• a light source configured to emit light;
• a beam deflector configured to deflect the light emitted by the light source through two stages;
• and
• a light guide plate configured to guide the light deflected by the beam deflector and configured to output the light through a light-output surface of the light guide plate,
• wherein the beam deflector comprises:
• a first beam deflector which comprises a plurality of first pattern electrodes provided in a first moving direction and having a stripe shape extending in a direction crossing the first moving direction, the first beam deflector being configured to deflect incident light in the first moving direction making an angle with a horizontal direction and a vertical direction, respectively, and oriented to a first location, and the first beam deflector comprising liquid crystals aligned such that long axes of the liquid crystals are parallel to the first moving direction when an electric field is not applied thereto;
• a second beam deflector which comprises a plurality of second pattern electrodes provided in a second moving direction and having a stripe shape extending in a direction crossing the second moving direction, the second beam deflector being configured to deflect the incident light that is deflected by the first beam deflector in the second moving direction making an angle with the horizontal direction and the vertical direction, respectively, at the first location, and oriented to a second location, and the second beam deflector comprising liquid crystals aligned such that long axes of the liquid crystals are parallel to the second moving direction when an electric field is not applied thereto;
• and
• a polarization converter provided between the first beam deflector and the second beam deflector and configured to convert polarization of the light incident to the second beam deflector such that the incident light deflected to the first moving direction by the first beam deflector is deflected to the second moving direction by the second beam deflector.

A holographic three-dimensional (3D) image display apparatus comprising:

• a backlight unit configured to emit light;
• and
• a spatial light modulator configured to form a holographic image by modulating the light emitted by the backlight unit,
• wherein the backlight unit comprises:
• a light source configured to emit the light;
• a beam deflector configured to deflect the light emitted by the light source through two stages, the beam deflector comprising a first beam deflector configured to deflect the light emitted by the light source in a first moving direction making an angle with a horizontal direction and a vertical direction, respectively, such that the deflected light is oriented to a first location, and a second beam deflector configured to deflect the light deflected from the first beam deflector such that the light is deflected in a second moving direction making an angle with the horizontal direction and the vertical direction, respectively, at the first location and is oriented to a second location;
• and
• a light guide plate configured to guide the light deflected from the beam deflector and output the light through a light-output surface of the light guide plate.