US 12,222,509 B2
Light flux diameter expanding element and image display device
Osamu Yokoyama, Shiorjiri (JP)
Assigned to SEIKO EPSON CORPORATION, Tokyo (JP)
Filed by SEIKO EPSON CORPORATION, Tokyo (JP)
Filed on Feb. 15, 2023, as Appl. No. 18/110,181.
Application 18/110,181 is a continuation of application No. 17/197,249, filed on Mar. 10, 2021, granted, now 11,619,818.
Application 17/197,249 is a continuation of application No. 16/367,985, filed on Mar. 28, 2019, granted, now 10,989,925, issued on Apr. 27, 2021.
Application 16/367,985 is a continuation of application No. 15/433,618, filed on Feb. 15, 2017, granted, now 10,281,725, issued on May 7, 2019.
Claims priority of application No. 2016-036787 (JP), filed on Feb. 29, 2016.
Prior Publication US 2023/0194877 A1, Jun. 22, 2023
Int. Cl. G02B 27/01 (2006.01); G02B 5/18 (2006.01); G02B 6/124 (2006.01); G02B 26/10 (2006.01)
CPC G02B 27/0172 (2013.01) [G02B 5/1842 (2013.01); G02B 5/1866 (2013.01); G02B 6/124 (2013.01); G02B 2005/1804 (2013.01); G02B 26/105 (2013.01); G02B 2027/011 (2013.01); G02B 2027/0112 (2013.01); G02B 2027/0118 (2013.01); G02B 2027/013 (2013.01); G02B 2027/0178 (2013.01)] 17 Claims
OG exemplary drawing
 
1. A light flux diameter expanding element comprising:
a first light guiding plate with a thickness of 0.2 mm to 0.8 mm that has:
a first input portion into which a first light is incident, the first input portion having a plurality of diffraction gratings that diffracts the first light; and
a first output portion having a plurality of diffraction gratings that emits the first light diffracted by the first input portion; and
a second light guiding plate with a thickness of 0.2 mm to 0.8 mm that has:
a second input portion into which a second light is incident, the second input portion having a plurality of diffraction gratings that diffracts the second light; and
a second output portion having a plurality of diffraction gratings that emits the second light diffracted by the second input portion, wherein
the second light includes a wavelength being larger than a wavelength of the first light,
a length of an interval at which the diffraction gratings is repeated in the second input portion of the second light guiding plate is longer than a length of an interval at which the diffraction gratings is repeated in the first input portion of the first light guiding plate,
a length of an interval at which the diffraction gratings is repeated in the second output portion of the second light guiding plate is longer than a length of an interval at which the diffraction gratings is repeated in the first output portion of the first light guiding plate,
the first input portion of the first light guiding plate diffracts a part of the first light in a first direction as a first diffracted light and diffracts another part of the first light in a second direction different from the first direction as a second diffracted light, and
the first output portion of the first light guiding plate emits both the first diffracted light and the second diffracted light.