Slim backlight unit for holographic display device and holographic display device including the same

A holographic display device comprising:

• a light source configured to emit light;
• a first beam expander configured to expand the light emitted from the light source in a first direction, the first beam expander comprising a first light guide plate which transmits light incident thereon;
• a second beam expander configured to expand the light output from the first beam expander in a second direction perpendicular to the first direction, the second beam expander comprising a second light guide plate which transmits light incident thereon;
• a beam deflector disposed on an optical path between the light source and the first beam expander, the beam deflector being configured to divide the light emitted from the light source into a first light beam and a second light beam, which are traveling at different angles, and two-dimensionally control paths of the first light beam and the second light beam;
• a spatial light modulator configured to diffract the first light beam coming from the second beam expander and thereby reproduce a first hologram image, and diffract the second light beam coming from the second beam expander and thereby reproduce a second hologram image;
• and
• a field lens configured to focus the first hologram image and the second hologram image, output from the spatial light modulator, onto different spaces.

A backlight unit comprising:

• a light source configured to provide a first light beam and a second light beam;
• a first beam expander configured to expand the first light beam and the second light beam in a first direction, the first beam expander comprising a first light guide plate which transmits the first light beam and the second light beam;
• a second beam expander configured to expand the first light beam and the second light beam output from the first beam expander in a second direction perpendicular to the first direction, the second beam expander comprising a second light guide plate which transmits the first light beam and the second light beam;
• a first beam deflector disposed on an optical path of the first light beam between the light source and the first beam expander, the first beam deflector being configured to two-dimensionally control a path of the first light beam;
• and
• a second beam deflector disposed on an optical path of the second light beam between the light source and the first beam expander, the second beam deflector being configured to two-dimensionally control a path of the second light beam, the path of the second light beam being different from the path of the first light beam.

A holographic display device comprising:

• a light source configured to provide a first light beam and a second light beam;
• a first beam expander configured to expand the first light beam and the second light beam in a first direction, the first beam expander comprising a first light guide plate which transmits the first light beam and the second light beam;
• a second beam expander configured to expand the first light beam and the second light beam output from the first beam expander in a second direction perpendicular to the first direction, the second beam expander comprising a second light guide plate which transmits the first light beam and the second light beam;
• a first beam deflector disposed on an optical path of the first light beam between the light source and the first beam expander, the first beam deflector being configured to two-dimensionally control a path of the first light beam;
• a second beam deflector disposed on an optical path of the second light beam between the light source and the first beam expander, the second beam deflector being configured to two-dimensionally control a path of the second light beam, the path of the second light beam being different from the path of the first light beam;
• a spatial light modulator configured to diffract the first light beam coming from the second beam expander and thereby reproduce a first hologram image, and diffract the second light beam coming from the second beam expander and thereby reproduce a second hologram image;
• and
• a field lens configured to focus the first hologram image and the second hologram image, output from the spatial light modulator, onto different spaces.