Zoom lens system, interchangeable lens apparatus and camera system
View Patent ↗A zoom lens system having at least five lens units, each lens unit being composed of at least one lens element, the zoom lens system, in order from an object side to an image side, comprising: a positive first lens unit; and a negative second lens unit, and in order from the image side to the object side, comprising: a positive lens unit γ; a negative lens unit β; and a positive lens unit α, wherein the first lens unit is composed of only optical elements having optical power, and in zooming from a wide-angle limit to a telephoto limit, at least the positive first lens unit is fixed with respect to an image surface, the positive lens unit α moves with respect to the image surface separately from an aperture diaphragm, and the negative lens unit β moves to the object side.
1. A zoom lens system having at least five lens units, each lens unit being composed of at least one lens element,
the zoom lens system, in order from an object side to an image side, comprising:
a first lens unit having positive optical power; and
a second lens unit having negative optical power, and
the zoom lens system, in order from the image side to the object side, comprising:
a lens unit γ having positive optical power;
a lens unit β having negative optical power; and
a lens unit α having positive optical power, wherein
the first lens unit is composed of only optical elements having optical power,
in zooming from a wide-angle limit to a telephoto limit at a time of image taking, at least the first lens unit is fixed with respect to an image surface, the lens unit α moves with respect to the image surface separately from an aperture diaphragm, and the lens unit β moves to the object side, and
the following condition (6) is satisfied:
nd 1G <1.65 (6)
where,
nd 1G is refractive index to the d-line of an optical element having the largest Optical axial thickness among the optical elements constituting the first lens unit.
2. The zoom lens system as claimed in claim 1 , wherein the following condition (1) is satisfied:
0.5< f W /T 1G <3.0 (1)
where,
f W is a focal length of the zoom lens system at the wide-angle limit, and
T 1G is an optical axial thickness of the first lens unit.
3. The zoom lens system as claimed in claim 1 , wherein the following condition (2) is satisfied:
0.4< Y T /T 1G <3.0 (2)
where,
Y T is an image height at the telephoto limit, and
T 1G is an optical axial thickness of the first lens unit.
4. The zoom lens system as claimed in claim 1 , wherein the following condition (3) is satisfied:
0.3< f W /T γG <7.0 (3)
where,
f W is a focal length of the zoom lens system at the wide-angle limit, and
T γG is an optical axial thickness of the lens unit γ.
5. The zoom lens system as claimed in claim 1 , wherein the following condition (4) is satisfied:
0.2< Y T /T γG <6.0 (4)
where,
Y T is an image height at the telephoto limit, and
T γG is an optical axial thickness of the lens unit γ.
6. The zoom lens system as claimed in claim 1 , wherein the following condition (5) is satisfied:
4.0< f W /T air1G2GW <350.0 (5)
where,
f W is a focal length of the zoom lens system at the wide-angle limit, and
T air1G2GW is an air space between the first lens unit and the second lens unit at the wide-angle limit.
7. The zoom lens system as claimed in claim 1 , wherein the following condition (7) is satisfied:
48<vd 1G (7)
where,
vd 1G is an Abbe number to the d-line of an optical element having the largest optical axial thickness among the optical elements constituting the first lens unit.
8. The zoom lens system as claimed in claim 1 , wherein
the zoom lens system is provided with an image blur compensating lens unit which moves in a direction perpendicular to an optical axis in order to optically compensate image blur, and
in zooming from the wide-angle limit to the telephoto limit at the time of image taking, the image blur compensating lens unit moves with respect to the image surface.
9. The zoom lens system as claimed in claim 1 , wherein
the zoom lens system is provided with an image blur compensating lens unit which moves in a direction perpendicular to an optical axis in order to optically compensate image blur, and
the image blur compensating lens unit is a part of any one of the lens units constituting the zoom lens system.
10. The zoom lens system as claimed in claim 1 , wherein
in zooming from the wide-angle limit to the telephoto limit at the time of image taking, the aperture diaphragm is fixed with respect to the image surface.
11. The zoom lens system as claimed in claim 1 , wherein
in zooming from the wide-angle limit to the telephoto limit at the time of image taking, the lens unit γ is fixed with respect to the image surface.
12. The zoom lens system as claimed in claim 1 , wherein
in zooming from the wide-angle limit to the telephoto limit at the time of image taking, the number of the aperture diaphragm and lens units, that are fixed with respect to the image surface, is equal to the number of lens units that move with respect to the image surface, or the number of the lens units that are fixed with respect to the image surface is equal to the number of the lens units that move with respect to the image surface.
13. The zoom lens system as claimed in claim 1 , wherein the following condition (8) is satisfied:
0.7<| M αG /M βG |<11.0 (8)
where,
M αG is an amount of movement of the lens unit α with respect to the image surface, in zooming from the wide-angle limit to the telephoto limit at the time of image taking, and
M βG is an amount of movement of the lens unit β with respect to the image surface, in zooming from the wide-angle limit to the telephoto limit at the time of image taking.
14. The zoom lens system as claimed in claim 1 , wherein the following condition (9) is satisfied:
L T /f T <1.45 (9)
where,
L T is an overall length of the zoom lens system, that is a distance from a most object side surface of the first lens unit to the image surface, at the telephoto limit, and
f T is a focal length of the zoom lens system at the telephoto limit.
15. The zoom lens system as claimed in claim 1 , wherein the following condition (10) is satisfied:
2.6<( f T /f W )×(tan(θ W )) 2 (10)
where,
f T is a focal length of the zoom lens system at the telephoto limit,
f W is a focal length of the zoom lens system at the wide-angle limit, and
θ W is a half view angle (°) at the wide-angle limit.
16. The zoom lens system as claimed in claim 1 , wherein the following condition (11) is satisfied:
0.02<| M βG /f W |<2.0 (11)
where,
M βG is an amount of movement of the lens unit β with respect to the image surface, in zooming from the wide-angle limit to the telephoto limit at the time of image taking, and
f W is a focal length of the zoom lens system at the wide-angle limit.
17. The zoom lens system as claimed in claim 1 , wherein
focusing from an infinity in-focus condition to a close-object in-focus condition is performed by moving the lens unit β along an optical axis direction.
18. An interchangeable lens apparatus comprising:
the zoom lens system as claimed in claim 1 ; and
a lens mount section which is connectable to a camera body including an image sensor for receiving an optical image formed by the zoom lens system and converting the optical image into an electric image signal.
19. A camera system comprising:
an interchangeable lens apparatus including the zoom lens system as claimed in claim 1 ; and
a camera body which is detachably connected to the interchangeable lens apparatus via a camera mount section, and includes an image sensor for receiving an optical image formed by the zoom lens system and converting the optical image into an electric image signal.