Reflective type telephoto lens and photographing apparatus including the same
A reflective type telephoto lens and a photographing apparatus including the reflective type telephoto lens are provided. The reflective type telephoto lens includes: a first lens that receives an incident flux of light from an object side; a main mirror including a reflective unit that reflects light transmitted through the first lens toward the object side, and a transmission portion disposed on a center portion thereof; a sub-mirror group including a sub-mirror that reflects light from the main mirror toward an image side; and a focusing lens group that focuses the light reflected by the sub-mirror.
1. A reflective type telephoto lens comprising:
a first lens that receives an incident flux of light from an object side;
a main mirror comprising a reflective unit that reflects light transmitted through the first lens toward the object side, and a transmission portion disposed on a center portion thereof;
a sub-mirror group comprising a sub-mirror that reflects light from the main mirror toward an image side; and
a focusing lens group that focuses the light reflected by the sub-mirror,
wherein the first lens comprises an accommodation portion disposed on a center portion thereof, and the sub-mirror group is disposed in the accommodation portion, and
wherein the reflective type telephoto lens satisfies the following inequality
0.4
≤
f
before
f
≤
0.8
,
where f before denotes a combined focal length of the first lens, the main mirror, and the sub-mirror group located in front of the focusing lens group, and f denotes an entire focal length of the reflective type telephoto lens.
2. The reflective type telephoto lens of claim 1 , wherein the reflective type telephoto lens satisfies following inequality
0.9
≤
f
primary
f
secondary
≤
1.5
,
where f primary denotes a focal length of the main mirror, and f secondary denotes a focal length of the sub-mirror group.
3. The reflective type telephoto lens of claim 1 , wherein the reflective type telephoto lens satisfies following inequality
0.1
≤
f
AF
f
≤
0.6
,
where f AF denotes a focal length of the focusing lens group, and f denotes the entire focal length of the reflective type telephoto lens.
4. The reflective type telephoto lens of claim 1 , wherein the focusing lens group comprises three or less lenses.
5. The reflective type telephoto lens of claim 1 , wherein the focusing lens group comprises at least one biconcave lens.
6. The reflective type telephoto lens of claim 1 , wherein the focusing lens group comprises a biconvex lens and a biconcave lens.
7. The reflective type telephoto lens of claim 1 , wherein the focusing lens group comprises a planoconvex lens and a biconcave lens.
8. The reflective type telephoto lens of claim 1 , wherein the focusing lens group comprises a biconvex lens, a biconcave lens, and a planoconvex lens.
9. The reflective type telephoto lens of claim 1 , wherein a stop is disposed between the sub-mirror and the focusing lens group.
10. The reflective type telephoto lens of claim 1 , wherein the sub-mirror group comprises a second lens next to the sub-mirror.
11. A reflective type telephoto lens comprising:
a first lens that receives an incident flux of light from an object side;
a main mirror comprising a reflective unit that reflects light transmitted through the first lens toward the object side, and a transmission portion disposed on a center portion thereof;
a sub-mirror group comprising a sub-mirror that reflects light from the main mirror toward an image side; and
a focusing lens group that focuses the light reflected by the sub-mirror,
wherein the focusing lens group is disposed on an optical axis between the main mirror and the sub-mirror, and wherein the reflective type telephoto lens satisfies the following inequality
0.4
≤
f
before
f
≤
0.8
,
where f before denotes a combined focal length of the first lens, the main mirror, and the sub-mirror group located in front of the focusing lens group, and f denotes an entire focal length of the reflective type telephoto lens.
12. The reflective type telephoto lens of claim 1 , wherein the reflective type telephoto lens has a half-viewing angle ranging from 2° to 3°.
13. The reflective type telephoto lens of claim 1 , wherein an entire length of the reflective type telephoto lens is not changed when the focusing lens group performs a focusing operation.
14. A reflective type telephoto lens comprising:
a first lens that receives an incident flux of light from an object side;
a main mirror comprising a reflective unit that reflects light transmitted through the first lens toward the object side, and a transmission portion disposed on a center portion thereof;
a sub-mirror group comprising a sub-mirror that reflects light from the main mirror toward an image side; and
a focusing lens group that focuses the light reflected by the sub-mirror,
wherein the first lens comprises an accommodation portion disposed on a center portion thereof, and the sub-mirror group is disposed in the accommodation portion, and
wherein the reflective type telephoto lens satisfies the following inequality
0.9
≤
f
primary
f
secondary
≤
1.5
,
where f primary denotes a focal length of the main mirror, and f secondary denotes a focal length of the sub-mirror group.
15. The reflective type telephoto lens of claim 14 , wherein the reflective type telephoto lens satisfies the following inequality
0.1
≤
f
AF
f
≤
0.6
,
where f AF denotes a focal length of the focusing lens group, and f denotes an entire focal length of the reflective type telephoto lens.
16. The reflective type telephoto lens of claim 14 , wherein the focusing lens group comprises three or less lenses.
17. The reflective type telephoto lens of claim 14 , wherein the focusing lens group comprises at least one biconcave lens.
18. The reflective type telephoto lens of claim 14 , wherein the focusing lens group comprises a biconvex lens and a biconcave lens.
19. The reflective type telephoto lens of claim 14 , wherein the focusing lens group comprises a planoconvex lens and a biconcave lens.
20. A photographing apparatus comprising:
a reflective type telephoto lens; and
an imaging device that receives light focused by the reflective type telephoto lens,
wherein the reflective type telephoto lens comprises:
a first lens that receives an incident flux of light from an object side;
a main mirror comprising a reflective unit that reflects light transmitted through the first lens toward the object side, and a transmission portion disposed on a center portion thereof;
a sub-mirror group comprising a sub-mirror that reflects light from the main mirror toward an image side; and
a focusing lens group that focuses the light reflected by the sub-mirror,
wherein the first lens comprises an accommodation portion disposed on a center portion thereof, and the sub-mirror group is disposed in the accommodation portion, and
wherein the reflective type telephoto lens satisfies the following inequality
0.4
≤
f
before
f
≤
0.8
,
where f before denotes a combined focal length of the first lens, the main mirror, and the sub-mirror group located in front of the focusing lens group, and f denotes an entire focal length of the reflective type telephoto lens.
21. The photographing apparatus of claim 20 , wherein the photographing apparatus satisfies the following equation
0.1
≤
f
AF
f
≤
0.6
,
where f AF denotes a focal length of the focusing lens group, and f denotes the entire focal length of the reflective type telephoto lens.
22. The photographing apparatus of claim 20 , wherein the photographing apparatus satisfies the following equation
0.9
≤
f
primary
f
secondary
≤
1.5
,
where f primary denotes a focal length of the main mirror, and f secondary denotes a focal length of the sub-mirror group.