US 11,747,623 B2
Display device and optical unit
Atsushi Saito, Chino (JP)
Assigned to SEIKO EPSON CORPORATION, Tokyo (JP)
Filed by SEIKO EPSON CORPORATION, Tokyo (JP)
Filed on Mar. 25, 2021, as Appl. No. 17/211,879.
Claims priority of application No. 2020-055571 (JP), filed on Mar. 26, 2020.
Prior Publication US 2021/0302740 A1, Sep. 30, 2021
Int. Cl. G02B 27/01 (2006.01)
CPC G02B 27/0172 (2013.01) [G02B 2027/0174 (2013.01); G02B 2027/0178 (2013.01)] 6 Claims
OG exemplary drawing
 
1. A display device comprising:
an image light generating device;
a light-guiding member on which image light emitted from the image light generating device is incident;
a first diffraction element provided at an incident side of the light-guiding member and having positive power;
a second diffraction element provided at an exit side of the light-guiding member and having positive power; and
a mirror provided at a convex of an end portion at the incident side of the light-guiding member and having positive power, wherein
the image light that passed through the first diffraction element is reflected by the mirror and propagates in the light-guiding member, and
the image light incident on the second diffraction element is deflected by the second diffraction element forming an exit pupil,
the first diffraction element is a first volume hologram having an interference fringe with a pitch and an inclination angle,
in the first diffraction element, the pitch of the interference fringe at an end portion closer side to the mirror is larger than the pitch of the interference fringe at an end portion farther side from the mirror,
in the first diffraction element, the inclination angle of the interference fringe at the end portion farther side from the mirror is larger than the inclination angle of the interference fringe at the end portion closer side to the mirror,
the second diffraction element is a second volume hologram having an interference fringe with a pitch and an inclination angle,
in the second diffraction element, the pitch of the interference fringe at an end portion closer side to the mirror is larger than the pitch of the interference fringe at an end portion farther side from the mirror, and
in the second diffraction element, the inclination angle of the interference fringe at the end portion farther side from the mirror is larger than the inclination angle of the interference fringe at the end portion closer side to the mirror.