Optical: systems and elements – Image stabilization – By movable refractive structure
Reexamination Certificate
2001-09-26
2004-09-07
Nguyen, Thong Q. (Department: 2872)
Optical: systems and elements
Image stabilization
By movable refractive structure
C359S554000, C359S676000
Reexamination Certificate
active
06788464
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a zoom lens and optical apparatus using the same. In particular, the present invention is suitable for photograph cameras, video cameras, electronic still cameras, digital cameras, 3-CCD compatible electronic cameras and the like which attempt to obtain still images and stabilize shot images by displacing images by moving part of lens units that constitute the zoom lens so as to have a component of a direction perpendicular to an optical axis, and by optically correcting blurs in shot images when the zoom lens vibrates (or inclines).
A so-called five-unit zoom lens including five lens units having, in order from the object side, positive, negative, positive, negative and positive refractive powers has conventionally been known as a zoom type suitable for a single-lens reflex camera.
This zoom type is suitable for a zoom lens of a high magnification range since each lens unit moves a relatively small distance, and advantageous in making wide-angle a short focus side since it may easily keep a long back focus.
This type of zoom lens is disclosed in U.S. Pat. Nos. 4,437,732, 4,498,741, Japanese Patent Publications No. Sho 61-51291 and the like. This assignee also discloses similar zoom lenses in Japanese Laid-Open Patent Applications Nos. Hei 6-230285, Hei 8-179213, Hei 9-304697 and the like.
On the other hand, a shooting system blurs images when receiving occasional vibrations. Various zoom lenses each including a mechanism for compensating for blurred images caused by the occasional vibrations (i.e., a vibration-resistant mechanism) have conventionally been proposed. For example, U.S. Pat. Nos. 5,270857, 6,124,972 and the like propose means for moving part of lens units which constitute an optical system (of the zoom lens) in a direction approximately perpendicular to the optical axis so as to compensating for vibration caused blurred images.
U.S. Pat. No. 5,270,857 discloses a zoom lens in its embodiment that is suitable primarily for a taking lens for use with a lens shutter camera, and teaches a structure that compensates for blurred images by moving in a direction approximately perpendicular to the optical axis partial lens unit part of a three-unit zoom lens that includes, in order from an object side, a first lens unit of negative refractive power, a second lens unit of positive refractive power, and a third lens unit of negative refractive power.
U.S. Pat. No. 6,124,972 discloses a zoom lens in its embodiment that is suitable primarily for a standard zoom lens for use with a single-lens reflex camera, and teaches a structure that compensates for blurred images by moving in a direction approximately perpendicular to the optical axis a second lens unit in a four-unit zoom lens that includes, in order from an object side, a first lens unit of positive refractive power, the second lens unit of negative refractive power, a third lens unit of positive refractive power, and a fourth lens unit of negative refractive power.
In general, a mechanism for vibrating part of lens unit in a shooting system so as to eliminate blurs in a shot image and obtaining still images requires a larger image-blur correcting capability, to smaller shift and rotary amounts of lens unit(s) (or movable lens unit(s)) to be vibrated for blur correction, a wholly compact apparatus, and the like.
In addition, if the defocus of the movable lens unit causes much eccentric aberration, the eccentric aberration defocuses images after blurs are corrected.
Therefore, an optical system having the vibration resistant function requires a smaller amount of eccentric aberration generated when the movable lens is moved in a direction orthogonal to the optical axis and made in an eccentric state, a larger blur-image correction capability with a smaller shift amount of the movable lens unit, a large so-called eccentric sensitivity (that is a ratio &Dgr;X/&Dgr;H of a correction amount &Dgr;X to blurred images to a unit shift amount &Dgr;H), and the like.
The zoom lens disclosed in U.S. Pat. No. 5,270,857 is a zoom lens that is suitable primarily for a zoom lens for use with a lens shutter camera and equipped with a mechanism for compensating for vibrations. In attempting to apply the zoom lens structure disclosed herein to a single-lens reflex camera, the back focus to keep a drive space for a QR mirror (quick return mirror) often runs short.
The zoom lens disclosed in U.S. Pat. No. 6,124,972 is a standard zoom lens for a single-lens reflex camera and equipped with a mechanism for compensating for vibrations, but such a four-unit structure of the lens unit makes it difficult to realize high range zooming.
SUMMARY OF THE INVENTION
It is an exemplified object of the present invention to provide a zoom lens and optical apparatus using the same which have high range zooming and maintains good stability of optical performance throughout the zoom range, facilitating a compact size of the entire apparatus even when equipped with a (vibration resistant) mechanism for compensating for vibrations, and has a vibration resistant function which may provide good images during compensation for vibrations.
In order to achieve the above object, a zoom lens of one aspect of the present invention comprises, in order from an object side, a first lens unit of positive refractive power, a second lens unit of negative refractive power, a third lens unit of positive refractive power, a fourth lens unit of negative refractive power, and a fifth lens unit of positive refractive power, wherein the zoom lens moves part of the lens units during zooming from a wide-angle end to a telephoto end so that a separation between the first lens unit and the second lens unit increases, a separation between the second lens unit and the third lens unit decreases, a separation between the third lens unit and the fourth lens unit increases, and a separation between the fourth lens unit and the fifth lens unit decreases, and wherein an image is displaced by moving at least part of the fourth lens unit so as to have a component of a direction perpendicular to an optical axis. According to the zoom lens, third lens constricts a luminous flux incident to the fourth lens unit. Therefore, it is relatively easy to miniaturize the fourth lens unit. In this zoom type, the fourth lens unit assists the zoom range in becoming enough large and serves to properly correct fluctuations in various aberrations during zooming, thus providing relatively small zooming contributions. Therefore, the present invention is characterized in that it is easy to properly control a remaining aberration amount in this lens unit. Due to this characteristic, the fourth lens unit may appropriately correct various eccentric aberrations during defocusing. Thereby, the zoom lens of the present invention may make small the entire apparatus to which such a zoom lens is applied, and maintain good stability of optical performance during compensation for vibrations.
In the above zoom lens, the fourth lens unit comprises two or more lens components including a lens component of negative refractive power, and the image is displaced by moving the lens component of negative refractive power so as to have the component of the direction perpendicular to the optical axis. According to this zoom lens, the lens component of negative refractive power may be set independent of a refractive power suitable for the compensation for vibrations by setting the refractive power of the entire fourth lens unit to be suitable for the zoom lens, and by assigning the lens component of negative refractive power to an image displacement correction unit.
In the above zoom lens, the fourth lens unit includes a lens component of positive refractive power and a lens component of negative refractive power. According to this zoom lens, the lens component of positive refractive power may easily make strong the lens component of negative refractive power as an image displacement correction unit, thereby making small the defocus amount during compensation for vibrations, and ren
Canon Kabushiki Kaisha
Morgan & Finnegan L.L.P.
Nguyen Thong Q.
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