US 11,747,620 B2
Backlight unit and holographic display apparatus including the same
Chilsung Choi, Suwon-si (KR); Hoon Song, Yongin-si (KR); and Hongseok Lee, Seoul (KR)
Assigned to SAMSUNG ELECTRONICS CO., LTD., Suwon-si (KR)
Filed by SAMSUNG ELECTRONICS CO., LTD., Suwon-si (KR)
Filed on Mar. 5, 2020, as Appl. No. 16/810,403.
Claims priority of application No. 10-2019-0117489 (KR), filed on Sep. 24, 2019.
Prior Publication US 2021/0088788 A1, Mar. 25, 2021
Int. Cl. G02B 27/01 (2006.01); F21V 8/00 (2006.01)
CPC G02B 27/0172 (2013.01) [G02B 6/0065 (2013.01); G02B 6/0078 (2013.01); G02B 2027/0174 (2013.01); G02B 2027/0178 (2013.01)] 26 Claims
OG exemplary drawing
 
1. A backlight unit comprising:
a light source configured to emit light; and
a light guide structure configured to guide the light emitted from the light source, the light guide structure comprising:
a first coupler layer; and
a second coupler layer facing the first coupler layer,
wherein the first coupler layer comprises:
a first output coupler configured to expand light traveling inside the light guide structure in a first direction and output the expanded light in the first direction to the outside of the light guide structure; and
a first expansion coupler configured to expand the light traveling inside the light guide structure in a second direction perpendicular to the first direction and provide the expanded light in the second direction to the first output coupler, and
wherein the second coupler layer comprises:
a second output coupler configured to expand light traveling inside the light guide structure in the first direction and output the expanded light to the outside of the light guide structure; and
a second expansion coupler configured to expand light traveling inside the light guide structure in the second direction and provide the expanded light to the second output coupler,
wherein the light guide structure further comprises:
a first input coupler disposed adjacent to a first side of the second expansion coupler in the second direction and configured to provide light to the first side of the second expansion coupler; and
a second input coupler disposed adjacent to a second side of the second expansion coupler in the second direction and configured to provide light to the second side of the second expansion coupler,
wherein the second side is opposite to the first side in the second direction, and
wherein the light is repeatedly incident on the first expansion coupler and the second expansion coupler while the light travels inside the light guide structure.