Optical system and image display apparatus
An optical system configured to guide light from a display element to an observation side includes a first lens having a first half-transmissive reflective surface provided to a surface on a display element side of the first lens, and a second lens having a second half-transmissive reflective surface. The light from the display element transmits through the second half-transmissive reflective surface, is reflected on the first half-transmissive reflective surface, is reflected on the second half-transmissive reflective surface, transmits through the first half-transmissive reflective surface, and is guided to the observation side. One of the first lens, the second lens, and another lens has negative refractive power. The first lens has a concave surface facing the observation side. A predetermined inequality is satisfied.
1. An optical system configured to guide light from a display element to an observation side, the optical system comprising:
a first lens having a first half-transmissive reflective surface provided to a surface on a display element side of the first lens; and
a second lens having a second half-transmissive reflective surface,
wherein the light from the display element transmits through the second half-transmissive reflective surface, is reflected on the first half-transmissive reflective surface, is reflected on the second half-transmissive reflective surface, transmits through the first half-transmissive reflective surface, and is guided to the observation side,
wherein one of the first lens, the second lens, and another lens has negative refractive power,
wherein the first lens has a concave surface facing the observation side, and
wherein the following inequality is satisfied:
1.
≤
❘
"\[LeftBracketingBar]"
fn
/
f
❘
"\[RightBracketingBar]"
≤
20.
10.
≤
vdn
≤
40.
where fn is a focal length of the one having the negative refractive power, f is a focal length of the optical system, νdn is an Abbe number of the one having the negative refractive power based on d-line.
2. The optical system according to claim 1 , wherein the light from the display element transmits through the one having the negative refractive power only once and is guided to the observation side.
3. The optical system according to claim 1 , wherein the one having the negative refractive power is made of a resin material.
4. The optical system according to claim 1 , wherein the following inequality is satisfied:
-
1
.
1
≤
fp
/
fn
≤
-
0
.
1
where fp is a focal length of a positive lens having largest refractive power among at least one positive lens included in the optical system.
5. The optical system according to claim 1 , wherein the following inequality is satisfied:
1.
≤
fp
/
f
≤
8.
where fp is a focal length of a positive lens having largest refractive power among at least one positive lens included in the optical system.
6. The optical system according to claim 1 , wherein the following inequality is satisfied:
-
5.
≤
HM
2
_
refR
/
f
≤
-
1.
where HM2_refR is a radius of curvature of a spherical surface passing through a surface vertex of the second half-transmissive reflective surface on an optical axis of the optical system and an end position of an optical effective diameter of the second half-transmissive reflective surface.
7. The optical system according to claim 1 , wherein the following inequality is satisfied:
-
0
.2
≤
HM
2
_refR
/
HM
1
_refR
≤
1.
where HM1_refR is a radius of curvature of a spherical surface passing through a surface vertex of the first half-transmissive reflective surface on an optical axis of the optical system and an end position of an optical effective diameter of the first half-transmissive reflective surface, and HM2_refR is a radius of curvature of a spherical surface passing through a surface vertex of the second half-transmissive reflective surface on an optical axis of the optical system and an end position of an optical effective diameter of the second half-transmissive reflective surface.
8. The optical system according to claim 1 , wherein the following inequality is satisfied:
0
.
5
≤
OAL
/
f
≤
1.5
where OAL is a distance on an optical axis from a surface closest to a pupil plane in the optical system to a display surface of the display element.
9. The optical system according to claim 1 , wherein the one having the negative refractive power is disposed closest to a pupil plane in the optical system.
10. The optical system according to claim 9 , wherein the first lens is the one having the negative refractive power.
11. The optical system according to claim 1 , wherein the first half-transmissive reflective surface is provided to a curved surface of the first lens.
12. The optical system according to claim 1 , wherein the one having the negative refractive power is disposed closer to the display element than the first lens.
13. The optical system according to claim 12 , wherein the other lens is the one having the negative refractive power and is cemented to the second lens.
14. The optical system according to claim 13 , wherein the second half-transmissive reflective surface is provided to a cemented surface between the second lens and the one having the negative refractive power.
15. The optical system according to claim 1 , wherein the first half-transmissive reflective surface is provided to a flat surface of the first lens.
16. An optical system configured to guide light from a display element to an observation side, the optical system comprising:
a first lens having a first half-transmissive reflective surface; and
a second lens having a second half-transmissive reflective surface,
wherein the light from the display element transmits through the second half-transmissive reflective surface, is reflected on the first half-transmissive reflective surface, is reflected on the second half-transmissive reflective surface, transmits through the first half-transmissive reflective surface, and is guided to the observation side,
wherein one of the first lens, the second lens, and another lens has negative refractive power, and
wherein the light from the display element transmits through the one having the negative refractive power only once and is guided to the observation side,
wherein the following inequality is satisfied:
10.
≤
vdn
≤
40.
where νdn is an Abbe number of the one having the negative refractive power based on d-line.
17. The optical system according to claim 16 , wherein the first half-transmissive reflective surface is provided to a surface on a display element side of the first lens, and
wherein the second half-transmissive reflective surface is provided to a surface on the observation side or the display element side of the second lens.
18. The optical system according to claim 16 , wherein the one having the negative refractive power is made of a resin material.
19. The optical system according to claim 16 , wherein the following inequality is satisfied:
-
1
.1
≤
fp
/
fn
≤
-
0
.
1
where fp is a focal length of a positive lens having largest refractive power among at least one positive lens included in the optical system.
20. The optical system according to claim 16 , wherein the following inequality is satisfied:
1.
≤
fp
/
f
≤
8.
where fp is a focal length of a positive lens having largest refractive power among at least one positive lens included in the optical system.
21. The optical system according to claim 16 , wherein the following inequality is satisfied:
-
5.
≤
HM
2
_
refR
/
f
≤
-
1.
where HM2_refR is a radius of curvature of a spherical surface passing through a surface vertex of the second half-transmissive reflective surface on an optical axis of the optical system and an end position of an optical effective diameter of the second half-transmissive reflective surface.
22. The optical system according to claim 16 , wherein the following inequality is satisfied:
-
0.2
≤
HM
2
_refR
/
HM
1
_refR
≤
1.
where HM1_refR is a radius of curvature of a spherical surface passing through a surface vertex of the first half-transmissive reflective surface on an optical axis of the optical system and an end position of an optical effective diameter of the first half-transmissive reflective surface, and HM2_refR is a radius of curvature of a spherical surface passing through a surface vertex of the second half-transmissive reflective surface on an optical axis of the optical system and an end position of an optical effective diameter of the second half-transmissive reflective surface.
23. The optical system according to claim 16 , wherein the following inequality is satisfied:
0
.
5
≤
OAL
/
f
≤
1.5
where OAL is a distance on an optical axis from a surface closest to a pupil plane in the optical system to a display surface of the display element.
24. The optical system according to claim 16 , wherein the one having the negative refractive power is disposed closest to a pupil plane in the optical system.
25. The optical system according to claim 24 , wherein the first lens is the one having the negative refractive power.
26. The optical system according to claim 16 , wherein the first half-transmissive reflective surface is provided to a curved surface of the first lens.
27. The optical system according to claim 16 , wherein the one having the negative refractive power is disposed closer to the display element than the first lens.
28. The optical system according to claim 27 , wherein the other lens is the one having the negative refractive power and is cemented to the second lens.
29. The optical system according to claim 28 , wherein the second half-transmissive reflective surface is provided to a cemented surface between the second lens and the one having the negative refractive power.
30. The optical system according to claim 16 , wherein the first half-transmissive reflective surface is provided to a flat surface of the first lens.
31. A display apparatus comprising:
an optical system configured to guide light from a display element to an observation side; and
the display element,
wherein the optical system includes:
a first lens having a first half-transmissive reflective surface provided to a surface on a display element side of the first lens; and
a second lens having a second half-transmissive reflective surface,
wherein the light from the display element transmits through the second half-transmissive reflective surface, is reflected on the first half-transmissive reflective surface, is reflected on the second half-transmissive reflective surface, transmits through the first half-transmissive reflective surface, and is guided to the observation side,
wherein one of the first lens, the second lens, and another lens has negative refractive power,
wherein the first lens has a concave surface facing the observation side, and
wherein the following inequality is satisfied:
1.
≤
❘
"\[LeftBracketingBar]"
fn
/
f
❘
"\[RightBracketingBar]"
≤
20.
10.
≤
vdn
≤
40.
where fn is a focal length of the one having the negative refractive power, f is a focal length of the optical system, and νdn is an Abbe number of the one having the negative refractive power based on d-line.
32. A display apparatus comprising:
an optical system configured to guide light from a display element to an observation side; and
the display element,
wherein the optical system includes:
a first lens having a first half-transmissive reflective surface; and
a second lens having a second half-transmissive reflective surface,
wherein the light from the display element transmits through the second half-transmissive reflective surface, is reflected on the first half-transmissive reflective surface, is reflected on the second half-transmissive reflective surface, transmits through the first half-transmissive reflective surface, and is guided to the observation side,
wherein one of the first lens, the second lens, and another lens has negative refractive power, and
wherein the light from the display element transmits through the one having the negative refractive power only once and is guided to the observation side,
wherein the following inequality is satisfied:
10.
0
≤
vdn
≤
40.
where νdn is an Abbe number of the one having the negative refractive power based on d-line.
33. An optical system configured to guide light from a display element to an observation side, the optical system comprising:
a first lens having a first half-transmissive reflective surface provided to a surface on a display element side of the first lens; and
a second lens having a second half-transmissive reflective surface,
wherein the light from the display element transmits through the second half-transmissive reflective surface, is reflected on the first half-transmissive reflective surface, is reflected on the second half-transmissive reflective surface, transmits through the first half-transmissive reflective surface, and is guided to the observation side,
wherein one of the first lens, the second lens, and another lens has negative refractive power,
wherein the first half-transmissive reflective surface has a curved shape, and
wherein the following inequality is satisfied:
1.
≤
❘
"\[LeftBracketingBar]"
fn
/
f
❘
"\[RightBracketingBar]"
≤
20.
10.
≤
vdn
≤
40.
where fn is a focal length of the one having the negative refractive power, f is a focal length of the optical system, and νdn is an Abbe number of the one having the negative refractive power based on d-line.