Optical device, image display device, and display apparatus
An optical device includes a first A deflecting member, a first B deflecting member, a first C deflecting member, a second A deflecting member, a second B deflecting member, and a second C deflecting member. Light emitted from an image forming device that enters the first A deflecting member and is emitted toward a pupil of an observer via the first B deflecting member and the first C deflecting member. Light emitted from the image forming device that enters the second A deflecting member is emitted toward the pupil of the observer via the second B deflecting member and the second C deflecting member. A direction of light deflected by the first A deflecting member that is orthogonally projected on a light guide plate is opposite a direction of light deflected by the second A deflecting member that is orthogonally projected on the light guide plate.
1. An optical device, on which light emitted from an image forming device is incident, in which the light is guided, and from which the light is emitted, the optical device comprising:
a light guide plate;
a first deflecting unit; and
a second deflecting unit, wherein
the first deflecting unit includes a first A deflecting member, a first B deflecting member, and a first C deflecting member,
the second deflecting unit includes a second A deflecting member, a second B deflecting member, and a second C deflecting member,
the first A deflecting member and the second A deflecting member being in a different plane than the first B deflecting member and the second B deflecting member,
part of the light emitted from the image forming device enters the first A deflecting member,
light incident on the first A deflecting member is deflected by the first A deflecting member, enters the first B deflecting member by total reflection inside of the light guide plate, is deflected by the first B deflecting member, enters the first C deflecting member by total reflection inside of the light guide plate, is deflected by the first C deflecting member, and is emitted toward a pupil of an observer,
at least a remaining part of the light emitted from the image forming device enters the second A deflecting member,
light incident on the second A deflecting member is deflected by the second A deflecting member, enters the second B deflecting member by total reflection inside of the light guide plate, is deflected by the second B deflecting member, enters the second C deflecting member by total reflection inside of the light guide plate, is deflected by the second C deflecting member, and is emitted toward the pupil of the observer, and
assuming that a direction obtained when a propagation direction of the light deflected by the first A deflecting member is orthogonally projected on the light guide plate is a first direction, and that a direction obtained when a propagation direction of the light deflected by the second A deflecting member is orthogonally projected on the light guide plate is a second direction, the first direction is opposite to the second direction.
2. The optical device according to claim 1 , wherein
assuming that
a point on the light guide plate, at which light emitted from the center point of an image forming region of the image forming device collides with the light guide plate, is an origin,
an axis line of the light guide plate that passes through the origin and is directed toward the first direction is an X-axis,
an axis in a thickness direction of the light guide plate that passes through the origin is a Z-axis, and
an axis that is orthogonal to the X-axis and the Z-axis is a Y-axis,
the first deflecting unit and the second deflecting unit are disposed symmetrically to a YZ plane.
3. The optical device according to claim 1 , wherein the first A deflecting member and the second A deflecting member each include a volume hologram diffraction grating, and satisfy
k X 1-A +k X 2-A =0,
k Y 1-A =k Y 2-A , and
k Z 1-A =k Z 2-A ,
where
a wave vector of the first A deflecting member is k v 1-A ,
an X component, a Y component, and a Z component of k v 1-A are k X 1-A , k Y 1-A , and k Z 1-A , respectively,
a wave vector of the second A deflecting member is k v 2-A , and
an X component, a Y component, and a Z component of k v 2-A are k X 2-A , k Y 2-A , and k Z 2-A , respectively.
4. The optical device according to claim 3 , wherein
the first C deflecting member and the second C deflecting member each include a volume hologram diffraction grating, and satisfy
k X 1-C +k X 2-C =0,
k Y 1-C =k Y 2-C , and
k Z 1-C =k Z 2-C ,
where
a wave vector of the first C deflecting member is k v 1-C ,
an X component, a Y component, and a Z component of k v 1-C are k X 1-C , k Y 1-C , and k Z 1-C , respectively,
a wave vector of the second C deflecting member is k v 2-C , and
an X component, a Y component, and a Z component of k v 2-C are k X 2-C , k Y 2-C , and k Z 2-C , respectively.
5. The optical device according to claim 4 , wherein
the first B deflecting member and the second B deflecting member each include a volume hologram diffraction grating, and satisfy
k X 1-B +k X 2-B =0,
k Y 1-B =k Y 2-B , and
k Z 1-B =k Z 2-C ,
where
a wave vector of the first B deflecting member is k v 1-B ,
an X component, a Y component, and a Z component of k v 1-B are k X 1-B , k Y 1-B , and k Z 1-B , respectively,
a wave vector of the second B deflecting member is k v 2-B , and
an X component, a Y component, and a Z component of k v 2-B are k X 2-B , k Y 2-B , and k Z 2-B , respectively.
6. The optical device according to claim 5 , wherein
k v 1-A +k v 1-B +k v 1-C =0, and
k v 2-A +k v 2-B +k v 2-C =0
are satisfied.
7. The optical device according to claim 1 , wherein
the part of the light that is emitted from the image forming device and enters the first A deflecting member enters the second A deflecting member.
8. The optical device according to claim 7 , wherein
the first A deflecting member and the second A deflecting member partially overlap.
9. The optical device according to claim 1 , wherein
the first A deflecting member and the first B deflecting member are laminated, and
the second A deflecting member and the second B deflecting member are laminated.
10. The optical device according to claim 1 , wherein
the first A deflecting member, the first B deflecting member, and the first C deflecting member each include a volume hologram diffraction grating, and satisfy
η 1-B /η 1-A <1, and
η 1-C /η 1-A <1
where
with respect to the light emitted from the image forming device,
an average diffraction efficiency of the first A deflecting member is η 1-A ,
an average diffraction efficiency of the first B deflecting member is η 1-B , and
an average diffraction efficiency of the first C deflecting member is η 1-C , and
the second A deflecting member, the second B deflecting member, and the second C deflecting member each include a volume hologram diffraction grating, and satisfy
η 2-B /η 2-A <1, and
η 2-C /η 2-A <1
where
with respect to the light emitted from the image forming device,
an average diffraction efficiency of the second A deflecting member is η 1-A ,
an average diffraction efficiency of the second B deflecting member is η 1-B , and
an average diffraction efficiency of the second C deflecting member is η 2-C .
11. An image display device, comprising:
an image forming device; and
an optical device, on which light emitted from the image forming device is incident, in which the light is guided, and from which the light is emitted, the optical device including
a light guide plate,
a first deflecting unit, and
a second deflecting unit, wherein
the first deflecting unit includes a first A deflecting member, a first B deflecting member, and a first C deflecting member,
the second deflecting unit includes a second A deflecting member, a second B deflecting member, and a second C deflecting member,
the first A deflecting member and the second A deflecting member being in a different plane than the first B deflecting member and the second B deflecting member,
part of the light emitted from the image forming device enters the first A deflecting member,
light incident on the first A deflecting member is deflected by the first A deflecting member, enters the first B deflecting member by total reflection inside of the light guide plate, is deflected by the first B deflecting member, enters the first C deflecting member by total reflection inside of the light guide plate, is deflected by the first C deflecting member, and is emitted toward a pupil of an observer,
at least a remaining part of the light emitted from the image forming device enters the second A deflecting member,
light incident on the second A deflecting member is deflected by the second A deflecting member, enters the second B deflecting member by total reflection inside of the light guide plate, is deflected by the second B deflecting member, enters the second C deflecting member by total reflection inside of the light guide plate, is deflected by the second C deflecting member, and is emitted toward the pupil of the observer, and
assuming that a direction obtained when a propagation direction of the light deflected by the first A deflecting member is orthogonally projected on the light guide plate is a first direction, and that a direction obtained when a propagation direction of the light deflected by the second A deflecting member is orthogonally projected on the light guide plate is a second direction, the first direction is opposite to the second direction.
12. The image display device according to claim 11 , wherein
assuming that
a point on the light guide plate, at which light emitted from the center point of an image forming region of the image forming device collides with the light guide plate, is an origin,
an axis line of the light guide plate that passes through the origin and is directed toward the first direction is an X-axis,
an axis in a thickness direction of the light guide plate that passes through the origin is a Z-axis, and
an axis that is orthogonal to the X-axis and the Z-axis is a Y-axis,
the first deflecting unit and the second deflecting unit are disposed symmetrically to a YZ plane.
13. The image display device according to claim 11 , wherein
the part of the light that is emitted from the image forming device and enters the first A deflecting member enters the second A deflecting member.
14. The image display device according to claim 13 , wherein
the first A deflecting member and the second A deflecting member partially overlap.
15. The image display device according to claim 11 , wherein
the first A deflecting member and the first B deflecting member are laminated, and
the second A deflecting member and the second B deflecting member are laminated.
16. A display apparatus, comprising:
a frame to be mounted to a head of an observer; and
an image display device attached to the frame,
the image display device including
an image forming device, and
an optical device, on which light emitted from the image forming device is incident, in which the light is guided, and from which the light is emitted, the optical device including
a light guide plate,
a first deflecting unit, and
a second deflecting unit, wherein
the first deflecting unit includes a first A deflecting member, a first B deflecting member, and a first C deflecting member,
the second deflecting unit includes a second A deflecting member, a second B deflecting member, and a second C deflecting member,
the first A deflecting member and the second A deflecting member being in a different plane than the first B deflecting member and the second B deflecting member,
part of the light emitted from the image forming device enters the first A deflecting member,
light incident on the first A deflecting member is deflected by the first A deflecting member, enters the first B deflecting member by total reflection inside of the light guide plate, is deflected by the first B deflecting member, enters the first C deflecting member by total reflection inside of the light guide plate, is deflected by the first C deflecting member, and is emitted toward a pupil of an observer,
at least a remaining part of the light emitted from the image forming device enters the second A deflecting member,
light incident on the second A deflecting member is deflected by the second A deflecting member, enters the second B deflecting member by total reflection inside of the light guide plate, is deflected by the second B deflecting member, enters the second C deflecting member by total reflection inside of the light guide plate, is deflected by the second C deflecting member, and is emitted toward the pupil of the observer, and
assuming that a direction obtained when a propagation direction of the light deflected by the first A deflecting member is orthogonally projected on the light guide plate is a first direction, and that a direction obtained when a propagation direction of the light deflected by the second A deflecting member is orthogonally projected on the light guide plate is a second direction, the first direction is opposite to the second direction.
17. The display apparatus according to claim 16 , wherein
assuming that
a point on the light guide plate, at which light emitted from the center point of an image forming region of the image forming device collides with the light guide plate, is an origin,
an axis line of the light guide plate that passes through the origin and is directed toward the first direction is an X-axis,
an axis in a thickness direction of the light guide plate that passes through the origin is a Z-axis, and
an axis that is orthogonal to the X-axis and the Z-axis is a Y-axis,
the first deflecting unit and the second deflecting unit are disposed symmetrically to a YZ plane.
18. The display apparatus according to claim 16 , wherein
the part of the light that is emitted from the image forming device and enters the first A deflecting member enters the second A deflecting member.
19. The display apparatus according to claim 18 , wherein
the first A deflecting member and the second A deflecting member partially overlap.
20. The display apparatus according to claim 16 , wherein
the first A deflecting member and the first B deflecting member are laminated, and
the second A deflecting member and the second B deflecting member are laminated.