Imaging optical system and image pickup apparatus having the same
An imaging optical system includes, in order from an object side to an image side, at least one concave lens, an aperture stop, a first transmissive reflective surface, a quarter waveplate, and a second transmissive reflective surface, arranged such that light from the object side transmits through the first transmissive reflective surface and the quarter waveplate in this order, is reflected by the second transmissive reflective surface toward the object side, transmits through the quarter waveplate, is reflected by the first transmissive reflective surface toward the image side, transmits through the quarter waveplate and the second transmissive reflective surface in this order, and travels toward the image side. A predetermined inequality is satisfied.
1 . An imaging optical system comprising, in order from an object side to an image side:
at least one negative lens;
an aperture stop;
a first transmissive reflective surface;
a quarter waveplate; and
a second transmissive reflective surface,
arranged such that light from the object side transmits through the first transmissive reflective surface and the quarter waveplate in this order, is reflected by the second transmissive reflective surface toward the object side, transmits through the quarter waveplate, is reflected by the first transmissive reflective surface toward the image side, transmits through the quarter waveplate and the second transmissive reflective surface in this order, and travels toward the image side,
wherein the following inequality is satisfied:
0.55
≤
zm
1
/
f
≤
4.8
where zm1 is a distance on an optical axis from the first transmissive reflective surface to an image plane, and f is a focal length of the imaging optical system.
2 . The imaging optical system according to claim 1 , wherein the following inequality is satisfied:
1.2
≤
zp
/
f
≤
6.5
where zp is a distance on the optical axis from the aperture stop to the image plane.
3 . The imaging optical system according to claim 1 , wherein the following inequality is satisfied:
1.
≤
Dp
/
f
≤
6.5
where Dp is a distance on the optical axis from a lens surface closest to an object of the imaging optical system to the aperture stop.
4 . The imaging optical system according to claim 1 , wherein the following inequality is satisfied:
0.005
≤
Dm
/
L
≤
0.06
where L is an overall length of the imaging optical system, and Dm is a distance on the optical axis from the first transmissive reflective surface to the second transmissive reflective surface.
5 . The imaging optical system according to claim 1 , wherein the following inequality is satisfied:
0.5
≤
zm
2
/
f
≤
4.5
where zm2 is a distance on the optical axis from the second transmissive reflective surface to the image plane.
6 . The imaging optical system according to claim 1 , wherein the following inequality is satisfied:
0.07
≤
Dm
1
/
L
≤
0.4
where L is an overall length of the imaging optical system, and Dm1 is a distance on the optical axis from the aperture stop to the first transmissive reflective surface.
7 . The imaging optical system according to claim 1 , wherein the following inequality is satisfied:
0.09
≤
Dm
2
/
L
≤
0.42
where L is an overall length of the imaging optical system, and Dm2 is a distance on the optical axis from the aperture stop to the second transmissive reflective surface.
8 . The imaging optical system according to claim 1 , wherein the following inequality is satisfied:
2.5
≤
L
/
f
≤
11.5
where L is an overall length of the imaging optical system.
9 . The imaging optical system according to claim 1 , wherein the following inequality is satisfied:
0.55
≤
Fno
≤
2.5
where Fno is an F-number of the imaging optical system.
10 . The imaging optical system according to claim 1 , wherein the second transmissive reflective surface has a concave shape on the object side.
11 . An imaging optical system comprising, in order from an object side to an image side:
an aperture stop;
a first transmissive reflective surface;
a quarter waveplate; and
a second transmissive reflective surface,
arranged such that light from the object side transmits through the first transmissive reflective surface and the quarter waveplate in this order, is reflected by the second transmissive reflective surface toward the object side, transmits through the quarter waveplate, is reflected by the first transmissive reflective surface toward the image side, transmits through the quarter waveplate and the second transmissive reflective surface in this order, and travels toward the image side,
wherein the following inequality is satisfied:
0.8
≤
zm
1
/
f
≤
4.8
where zm1 is a distance on an optical axis from the first transmissive reflective surface to the image plane, and f is a focal length of the imaging optical system.
12 . The imaging optical system according to claim 11 , wherein the following inequality is satisfied:
1.2
≤
zp
/
f
≤
6.5
where zp is a distance on the optical axis from the aperture stop to the image plane.
13 . The imaging optical system according to claim 11 , wherein the following inequality is satisfied:
1.
≤
Dp
/
f
≤
6.5
where Dp is a distance on the optical axis from a lens surface closest to an object of the imaging optical system to the aperture stop.
14 . The imaging optical system according to claim 11 , wherein the following inequality is satisfied:
0.005
≤
Dm
/
L
≤
0.06
where L is an overall length of the imaging optical system, and Dm is a distance on the optical axis from the first transmissive reflective surface to the second transmissive reflective surface.
15 . The imaging optical system according to claim 11 , wherein the following inequality is satisfied:
0.5
≤
zm
2
/
f
≤
4.5
where zm2 is a distance on the optical axis from the second transmissive reflective surface to the image plane.
16 . The imaging optical system according to claim 11 , wherein the following inequality is satisfied:
0.07
≤
Dm
1
/
L
≤
0.4
where L is an overall length of the imaging optical system, and Dm1 is a distance on the optical axis from the aperture stop to the first transmissive reflective surface.
17 . The imaging optical system according to claim 11 , wherein the following inequality is satisfied:
0.09
≤
Dm
2
/
L
≤
0.42
where L is an overall length of the imaging optical system, and Dm2 is a distance on the optical axis from the aperture stop to the second transmissive reflective surface.
18 . The imaging optical system according to claim 11 , wherein the following inequality is satisfied:
2.5
≤
L
/
f
≤
11.5
where L is an overall length of the imaging optical system.
19 . An image pickup apparatus comprising:
an imaging optical system; and
an image sensor configured to receive an image formed by the imaging optical system,
wherein the imaging optical system includes, in order from an object side to an image side:
at least one negative lens;
an aperture stop;
a first transmissive reflective surface;
a quarter waveplate; and
a second transmissive reflective surface,
arranged such that light from the object side transmits through the first transmissive reflective surface and the quarter waveplate in this order, is reflected by the second transmissive reflective surface toward the object side, transmits through the quarter waveplate, is reflected by the first transmissive reflective surface toward the image side, transmits through the quarter waveplate and the second transmissive reflective surface in this order, and travels toward the image side, and
wherein the following inequality is satisfied:
0.55
≤
zm
1
/
f
≤
4.8
where zm1 is a distance on an optical axis from the first transmissive reflective surface to an image plane, and f is a focal length of the imaging optical system.
20 . An image pickup apparatus comprising:
an imaging optical system; and
an image sensor configured to receive an image formed by the imaging optical system,
wherein the imaging optical system includes, in order from an object side to an image side:
an aperture stop;
a first transmissive reflective surface;
a quarter waveplate; and
a second transmissive reflective surface,
arranged such that light from the object side transmits through the first transmissive reflective surface and the quarter waveplate in this order, is reflected by the second transmissive reflective surface toward the object side, transmits through the quarter waveplate, is reflected by the first transmissive reflective surface toward the image side, transmits through the quarter waveplate and the second transmissive reflective surface in this order, and travels toward the image side, and
wherein the following inequality is satisfied:
0.8
≤
zm
1
/
f
≤
4.8
where zm1 is a distance on an optical axis from the first transmissive reflective surface to the image plane, and f is a focal length of the imaging optical system.