Patent Application
20110228158
This application is based on application No. 2010-065050 filed in Japan on Mar. 19, 2010, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a zoom lens system, an interchangeable lens apparatus, and a camera system. In particular, the present invention relates to: a compact and lightweight zoom lens system having a relatively high zooming ratio, in which aberration fluctuation in association with focusing is reduced, and aberrations particularly in a close-object in-focus condition are sufficiently compensated to provide excellent optical performance over the overall focusing condition; and an interchangeable lens apparatus and a camera system each employing this zoom lens system.
2. Description of the Background Art
In recent years, interchangeable-lens type digital camera systems (also referred to simply as “camera systems”, hereinafter) have been spreading rapidly. Such interchangeable-lens type digital camera systems can realize: taking of a high-sensitive and high-quality image; high-speed focusing and high-speed image processing after image taking; and easy replacement of an interchangeable lens apparatus in accordance with a desired scene. Furthermore, an interchangeable lens apparatus having a zoom lens system that forms an optical image with variable magnification is popular because it allows free change of focal length without the necessity of lens replacement.
A compact zoom lens system having a high zooming ratio and excellent optical performance from a wide-angle limit to a telephoto limit has been desired as a zoom lens system to be used in an interchangeable lens apparatus. Various kinds of zoom lens systems having multiple-unit configurations, such as four-unit configuration and five-unit configuration, have been proposed. In such zoom lens systems, focusing is usually performed such that some lens units in the lens system are moved in a direction along the optical axis. However, when focusing from an infinity in-focus condition to a close-object in-focus condition is performed by a single lens unit, the amount of movement at focusing of this lens unit depends on paraxial power configuration in the entire lens system. Therefore, it is difficult to favorably compensate the amount of aberration fluctuation from a wide angle limit to a telephoto limit.
In order to reduce aberration fluctuation at the time of focusing, various zoom lens systems are proposed, in which a plurality of lens units in the lens system are individually moved in the direction along the optical axis.
Japanese Patent No. 4402368 discloses a zoom lens having four-unit configuration of positive, negative, negative, and positive. In this zoom lens, at the time of zooming, a first lens unit and a fourth lens unit move from the image side to the object side, and thereby the intervals between the respective lens units are changed. At the time of focusing, a second lens unit moves to the image side at a wide-angle limit and moves to the object side at a telephoto limit, and a third lens unit moves to the object side regardless of the zooming condition. The amounts of movement at the time of focusing of the second and third lens units are set forth.
Japanese Laid-Open Patent Publication No. 2009-169051 discloses a zoom lens having three-or-more-unit configuration, in which a negative lens unit is located closest to the object side. In this zoom lens, the intervals between the respective lens units are changed at the time of zooming. A first focusing unit and a second focusing unit which includes a positive lens and a negative lens individually move at the timing of focusing. Abbe numbers of the positive lens and the negative lens are set forth.
Japanese Laid-Open Patent Publication No. 11-072705 discloses a zoom lens having a six-unit configuration of positive, negative, positive, positive, negative, and positive. In this zoom lens, at the time of zooming, at least one magnification-variable lens unit among the second to sixth lens units moves along the optical axis. At least one of the third to sixth lens units is moved along the optical axis to compensate variation in the image point position due to the zooming. At least two focusing lens units among the first to sixth lens units are moved along the optical axis to perform focusing.
In each of the zoom lenses disclosed in the above-described patent literatures, the aberration fluctuation at the time of focusing is reduced to some extent. However, since compensation of aberrations, particularly in a close-object in-focus condition, is insufficient, the zoom lenses do not have excellent optical performance over the entire object distance from an infinite object distance to a close object distance.
An object of the present invention is to provide: a compact and lightweight zoom lens system having a relatively high zooming ratio, in which aberration fluctuation in association with focusing is reduced, and aberrations particularly in a close-object in-focus condition are sufficiently compensated to provide excellent optical performance over the overall focusing condition; and an interchangeable lens apparatus and a camera system each employing this zoom lens system.
The novel concepts disclosed herein were achieved in order to solve the foregoing problems in the conventional art, and herein is disclosed:
a zoom lens system comprising a plurality of lens units, each lens unit comprising at least one lens element, wherein
the zoom lens system, in order from an object side to an image side, comprises a first lens unit, a second lens unit, a third lens unit and subsequent lens units including at least a fourth lens unit,
an aperture diaphragm is either included in the third lens unit or located on the image side relative to the third lens unit,
at least two among the first lens unit, the second lens unit, the third lens unit and the subsequent lens units are movable lens units which individually move along an optical axis at the time of zooming from a wide-angle limit to a telephoto limit during image taking,
at least two of the movable lens units are focusing lens units which move along the optical axis at the time of focusing from an infinity in-focus condition to a close-object in-focus condition in at least one zooming position from a wide-angle limit to a telephoto limit, and
at least the second lens unit and one of the subsequent lens units are the focusing lens units.
The novel concepts disclosed herein were achieved in order to solve the foregoing problems in the conventional art, and herein is disclosed:
an interchangeable lens apparatus comprising:
a zoom lens system; 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; wherein
the zoom lens system comprises a plurality of lens units, each lens unit comprising at least one lens element, in which
the zoom lens system, in order from an object side to an image side, comprises a first lens unit, a second lens unit, a third lens unit and subsequent lens units including at least a fourth lens unit,
an aperture diaphragm is either included in the third lens unit or located on the image side relative to the third lens unit,
at least two among the first lens unit, the second lens unit, the third lens unit and the subsequent lens units are movable lens units which individually move along an optical axis at the time of zooming from a wide-angle limit to a telephoto limit during image taking,
at least two of the movable lens units are focusing lens units which move along the optical axis at the time of focusing from an infinity in-focus condition to a close-object in-focus condition in at least one zooming position from a wide-angle limit to a telephoto limit, and
at least the second lens unit and one of the subsequent lens units are the focusing lens units.
The novel concepts disclosed herein were achieved in order to solve the foregoing problems in the conventional art, and herein is disclosed:
a camera system comprising:
an interchangeable lens apparatus including a zoom lens system; 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; wherein
the zoom lens system comprises a plurality of lens units, each lens unit comprising at least one lens element, in which
the zoom lens system, in order from an object side to an image side, comprises a first lens unit, a second lens unit, a third lens unit and subsequent lens units including at least a fourth lens unit,
an aperture diaphragm is either included in the third lens unit or located on the image side relative to the third lens unit,
at least two among the first lens unit, the second lens unit, the third lens unit and the subsequent lens units are movable lens units which individually move along an optical axis at the time of zooming from a wide-angle limit to a telephoto limit during image taking,
at least two of the movable lens units are focusing lens units which move along the optical axis at the time of focusing from an infinity in-focus condition to a close-object in-focus condition in at least one zooming position from a wide-angle limit to a telephoto limit, and
at least the second lens unit and one of the subsequent lens units are the focusing lens units.
According to the present invention, it is possible to provide: a compact and lightweight zoom lens system having a relatively high zooming ratio, in which aberration fluctuation in association with focusing is reduced, and aberrations particularly in a close-object in-focus condition are sufficiently compensated to provide excellent optical performance over the overall focusing condition; and an interchangeable lens apparatus and a camera system each employing this zoom lens system.
This and other objects and features of this invention will become clear from the following description, taken in conjunction with the preferred embodiments with reference to the accompanied drawings in which:
In each Fig., part (a) shows a lens configuration at a wide-angle limit (in the minimum focal length condition: focal length fW), part (b) shows a lens configuration at a middle position (in an intermediate focal length condition: focal length fM=√(fW*fT)), and part (c) shows a lens configuration at a telephoto limit (in the maximum focal length condition: focal length fT). Further, in each Fig., each bent arrow located between part (a) and part (b) indicates a line obtained by connecting the positions of each lens unit respectively at a wide-angle limit, a middle position and a telephoto limit, in order from the top. In the part between the wide-angle limit and the middle position, and the part between the middle position and the telephoto limit, the positions are connected simply with a straight line, and hence this line does not indicate actual motion of each lens unit.
Moreover, in each Fig., an arrow imparted to a lens unit indicates focusing from an infinity in-focus condition to a close-object in-focus condition. That is, in
Each of the zoom lens systems according to Embodiments 1 and 2, in order from the object side to the image side, comprises a first lens unit G1 having positive optical power, a second lens unit G2 having negative optical power, a third lens unit G3 having positive optical power, a fourth lens unit G4 having negative optical power, and a fifth lens unit G5 having positive optical power. In the zoom lens systems according to Embodiments 1 and 2, at the time of zooming, the second lens unit G2 and the fourth lens unit G4 individually move in the direction along the optical axis so that the intervals between the respective lens units, i.e., the interval between the first lens unit G1 and the second lens unit G2, the interval between the second lens unit G2 and the third lens unit G3, the interval between the third lens unit G3 and the fourth lens unit G4, and the interval between the fourth lens unit G4 and the fifth lens unit G5, vary. In the zoom lens systems according to Embodiments 1 and 2, these lens units are arranged in a desired optical power configuration, and thereby size reduction is achieved in the entire lens system while maintaining high optical performance.
Each of the zoom lens systems according to Embodiments 3 to 6, in order from the object side to the image side, comprises a first lens unit G1 having positive optical power, a second lens unit G2 having negative optical power, a third lens unit G3 having positive optical power, a fourth lens unit G4, a fifth lens unit G5, and a sixth lens unit G6 having positive optical power. In the zoom lens systems according to Embodiments 3 and 4, the fourth lens unit G4 has positive optical power and the fifth lens unit G5 has negative optical power. In the zoom lens systems according to Embodiments 5 and 6, the fourth lens unit G4 has negative optical power and the fifth lens unit G5 has positive optical power. In the zoom lens systems according to Embodiments 3 and 4, at the time of zooming, the second lens unit G2, the third lens unit G3, and the fifth lens unit G5 individually move in the direction along the optical axis so that the intervals between the respective lens units, i.e., the interval between the first lens unit G1 and the second lens unit G2, the interval between the second lens unit G2 and the third lens unit G3, the interval between the third lens unit G3 and the fourth lens unit G4, the interval between the fourth lens unit G4 and the fifth lens unit G5, and the interval between the fifth lens unit G5 and the sixth lens unit G6, vary. In the zoom lens systems according to Embodiments 5 and 6, at the time of zooming, the second lens unit G2, the fourth lens unit G4, and the fifth lens unit G5 individually move in the direction along the optical axis so that the intervals between the respective lens units, i.e., the interval between the first lens unit G1 and the second lens unit G2, the interval between the second lens unit G2 and the third lens unit G3, the interval between the third lens unit G3 and the fourth lens unit G4, the interval between the fourth lens unit G4 and the fifth lens unit G5, and the interval between the fifth lens unit G5 and the sixth lens unit G6, vary. In the zoom lens systems according to Embodiments 3 to 6, these lens units are arranged in a desired optical power configuration, and thereby size reduction is achieved in the entire lens system while maintaining high optical performance.
Further, in
Further, as shown in
As shown in
In the zoom lens system according to Embodiment 1, the second lens unit G2, in order from the object side to the image side, comprises a bi-concave fourth lens element L4, a bi-concave fifth lens element L5, and a positive meniscus sixth lens element L6 with the convex surface facing the object side. Among these, the fifth lens element L5 has an aspheric object side surface. The second lens unit G2 is a lens unit having the greatest absolute value of optical power among all the lens units, as shown in Numerical Example 1 described later.
In the zoom lens system according to Embodiment 1, the third lens unit G3, in order from the object side to the image side, comprises a positive meniscus seventh lens element L7 with the convex surface facing the object side, a negative meniscus eighth lens element L8 with the convex surface facing the object side, a positive meniscus ninth lens element L9 with the convex surface facing the object side, a bi-convex tenth lens element L10, and a negative meniscus eleventh lens element L11 with the convex surface facing the image side. Among these, the eighth lens element L8 and the ninth lens element L9 are cemented with each other, and the tenth lens element L10 and the eleventh lens element L11 are cemented with each other. The ninth lens element L9 has an aspheric image side surface, and the tenth lens element L10 has an aspheric object side surface. Further, an aperture diaphragm A is provided between the ninth lens element L9 and the tenth lens element L10.
In the zoom lens system according to Embodiment 1, the fourth lens unit G4, in order from the object side to the image side, comprises a negative meniscus twelfth lens element L12 with the convex surface facing the object side, and a bi-concave thirteenth lens element L13.
In the zoom lens system according to Embodiment 1, the fifth lens unit G5 comprises solely a bi-convex fourteenth lens element L14. The fourteenth lens element L14 has an aspheric image side surface.
In the zoom lens system according to Embodiment 1, the tenth lens element L10 and the eleventh lens element L11 in the third lens unit G3 correspond to an image blur compensating lens unit described later, which moves in a direction perpendicular to the optical axis in order to optically compensate image blur.
In the zoom lens system according to Embodiment 1, at the time of zooming from a wide-angle limit to a telephoto limit during image taking, the second lens unit G2 and the fourth lens unit G4 monotonically move to the image side, and the first lens unit G1, the third lens unit G3, and the fifth lens unit G5 are fixed relative to the image surface S. That is, in zooming, the second lens unit G2 and the fourth lens unit G4 individually move along the optical axis so that the interval between the first lens unit G1 and the second lens unit G2 and the interval between the third lens unit G3 and the fourth lens unit G4 increase, and the interval between the second lens unit G2 and the third lens unit G3 and the interval between the fourth lens unit G4 and the fifth lens unit G5 decrease.
Further, in the zoom lens system according to Embodiment 1, at the time of focusing from an infinity in-focus condition to a close-object in-focus condition, the second lens unit G2 does not move along the optical axis at a wide-angle limit, but moves to the object side along the optical axis in other zooming conditions. Further, at the time of focusing from the infinity in-focus condition to the close-object in-focus condition, the fourth lens unit G4 moves to the image side along the optical axis at a wide-angle limit, and moves to the object side along the optical axis in other zooming conditions.
As shown in
In the zoom lens system according to Embodiment 2, the second lens unit G2, in order from the object side to the image side, comprises a bi-concave fourth lens element L4, a bi-concave fifth lens element L5, and a positive meniscus sixth lens element L6 with the convex surface facing the object side. Among these, the fifth lens element L5 has an aspheric object side surface. The second lens unit G2 is a lens unit having the greatest absolute value of optical power among all the lens units, as shown in Numerical Example 2 described later.
In the zoom lens system according to Embodiment 2, the third lens unit G3, in order from the object side to the image side, comprises a positive meniscus seventh lens element L7 with the convex surface facing the object side, a negative meniscus eighth lens element L8 with the convex surface facing the object side, a positive meniscus ninth lens element L9 with the convex surface facing the object side, a bi-convex tenth lens element L10, and a negative meniscus eleventh lens element L11 with the convex surface facing the image side. Among these, the eighth lens element L8 and the ninth lens element L9 are cemented with each other, and the tenth lens element L10 and the eleventh lens element L11 are cemented with each other. The ninth lens element L9 has an aspheric image side surface, and the tenth lens element L10 has an aspheric object side surface. Further, an aperture diaphragm A is provided between the ninth lens element L9 and the tenth lens element L10.
In the zoom lens system according to Embodiment 2, the fourth lens unit G4, in order from the object side to the image side, comprises a negative meniscus twelfth lens element L12 with the convex surface facing the object side, and a bi-concave thirteenth lens element L13.
In the zoom lens system according to Embodiment 2, the fifth lens unit G5 comprises solely a bi-convex fourteenth lens element L14. The fourteenth lens element L14 has an aspheric image side surface.
In the zoom lens system according to Embodiment 2, the tenth lens element L10 and the eleventh lens element L11 in the third lens unit G3 correspond to an image blur compensating lens unit described later, which moves in a direction perpendicular to the optical axis in order to optically compensate image blur.
In the zoom lens system according to Embodiment 2, at the time of zooming from a wide-angle limit to a telephoto limit during image taking, the second lens unit G2 and the fourth lens unit G4 monotonically move to the image side, and the first lens unit G1, the third lens unit G3, and the fifth lens unit G5 are fixed relative to the image surface S. That is, in zooming, the second lens unit G2 and the fourth lens unit G4 individually move along the optical axis so that the interval between the first lens unit G1 and the second lens unit G2 and the interval between the third lens unit G3 and the fourth lens unit G4 increase, and the interval between the second lens unit G2 and the third lens unit G3 and the interval between the fourth lens unit G4 and the fifth lens unit G5 decrease.
Further, in the zoom lens system according to Embodiment 2, at the time of focusing from an infinity in-focus condition to a close-object in-focus condition, the second lens unit G2 does not move along the optical axis at a wide-angle limit, but moves to the object side along the optical axis in other zooming conditions. Further, at the time of focusing from the infinity in-focus condition to the close-object in-focus condition, the fourth lens unit G4 moves to the image side along the optical axis at a wide-angle limit, and moves to the object side along the optical axis in other zooming conditions.
As shown in
In the zoom lens system according to Embodiment 3, the second lens unit G2, in order from the object side to the image side, comprises a positive meniscus fourth lens element L4 with the convex surface facing the image side, a bi-concave fifth lens element L5, a bi-concave sixth lens element L6, and a bi-convex seventh lens element L7. Among these, the fourth lens element L4 and the fifth lens element L5 are cemented with each other. The fourth lens element L4 is an aspherical lens element formed of a thin layer of resin or the like, and has an aspheric object side surface. The second lens unit G2 is a lens unit having the greatest absolute value of optical power among all the lens units, as shown in Numerical Example 3 described later.
In the zoom lens system according to Embodiment 3, the third lens unit G3, in order from the object side to the image side, comprises a bi-convex eighth lens element L8, a negative meniscus ninth lens element L9 with the convex surface facing the object side, and a bi-convex tenth lens element L10. Among these, the ninth lens element L9 and the tenth lens element L10 are cemented with each other. The eighth lens element L8 has two aspheric surfaces.
In the zoom lens system according to Embodiment 3, the fourth lens unit G4, in order from the object side to the image side, comprises a bi-convex eleventh lens element L11, and a negative meniscus twelfth lens element L12 with the convex surface facing the image side. The eleventh lens element L11 and the twelfth lens element L12 are cemented with each other. The eleventh lens element L11 has an aspheric object-side surface. Further, an aperture diaphragm A is provided on the object side relative to the eleventh lens element L11.
In the zoom lens system according to Embodiment 3, the fifth lens unit G5, in order from the object side to the image side, comprises a negative meniscus thirteenth lens element L13 with the convex surface facing the object side, a bi-concave fourteenth lens element L14, a bi-convex fifteenth lens element L15, and a bi-convex sixteenth lens element L16. Among these, the fourteenth lens element L14 and the fifteenth lens element L15 are cemented with each other. The sixteenth lens element L16 has two aspheric surfaces.
In the zoom lens system according to Embodiment 3, the sixth lens unit G6 comprises solely a positive meniscus seventeenth lens element L17 with the convex surface facing the object side. The seventeenth lens element L17 has two aspheric surfaces.
In the zoom lens system according to Embodiment 3, the eleventh lens element L11 and the twelfth lens element L12 in the fourth lens unit G4 correspond to an image blur compensating lens unit described later, which moves in a direction perpendicular to the optical axis in order to optically compensate image blur.
In the zoom lens system according to Embodiment 3, at the time of zooming from a wide-angle limit to a telephoto limit during image taking, the second lens unit G2 monotonically moves to the image side, the third lens unit G3 moves with locus of a convex to the object side, and the fifth lens unit G5 moves with locus of a convex to the image side so that its position is closer to the image side at a telephoto limit than at a wide-angle limit. Further, the first lens unit G1, the fourth lens unit G4, and the sixth lens unit G6 are fixed relative to the image surface S. That is, in zooming, the second lens unit G2, the third lens unit G3, and the fifth lens unit G5 individually move along the optical axis so that the interval between the first lens unit G1 and the second lens unit G2 and the interval between the fourth lens unit G4 and the fifth lens unit G5 increase, and the interval between the second lens unit G2 and the third lens unit G3 and the interval between the fifth lens unit G5 and the sixth lens unit G6 decrease.
Further, in the zoom lens system according to Embodiment 3, at the time of focusing from an infinity in-focus condition to a close-object in-focus condition, the second lens unit G2 does not move along the optical axis at a wide-angle limit, but moves to the object side along the optical axis in other zooming conditions. Further, at the time of focusing from the infinity in-focus condition to the close-object in-focus condition, the fifth lens unit G5 moves to the image side along the optical axis at a wide-angle limit and at a telephoto limit, and moves to the object side along the optical axis in other zooming conditions.
As shown in
In the zoom lens system according to Embodiment 4, the second lens unit G2, in order from the object side to the image side, comprises a negative meniscus fourth lens element L4 with the convex surface facing the image side, a bi-concave fifth lens element L5, a bi-concave sixth lens element L6, and a bi-convex seventh lens element L7. Among these, the fourth lens element L4 and the fifth lens element L5 are cemented with each other. The fourth lens element L4 is an aspherical lens element formed of a thin layer of resin or the like, and has an aspheric object side surface. The second lens unit G2 is a lens unit having the greatest absolute value of optical power among all the lens units, as shown in Numerical Example 4 described later.
In the zoom lens system according to Embodiment 4, the third lens unit G3, in order from the object side to the image side, comprises a bi-convex eighth lens element L8, a negative meniscus ninth lens element L9 with the convex surface facing the object side, and a bi-convex tenth lens element L10. Among these, the ninth lens element L9 and the tenth lens element L10 are cemented with each other. The eighth lens element L8 has two aspheric surfaces.
In the zoom lens system according to Embodiment 4, the fourth lens unit G4, in order from the object side to the image side, comprises a bi-convex eleventh lens element L11, and a negative meniscus twelfth lens element L12 with the convex surface facing the image side. The eleventh lens element L11 and the twelfth lens element L12 are cemented with each other. The eleventh lens element L11 has an aspheric object side surface. Further, an aperture diaphragm A is provided on the object side relative to the eleventh lens element L11.
In the zoom lens system according to Embodiment 4, the fifth lens unit G5, in order from the object side to the image side, comprises a negative meniscus thirteenth lens element L13 with the convex surface facing the object side, a bi-concave fourteenth lens element L14, a bi-convex fifteenth lens element L15, and a bi-convex sixteenth lens element L16. Among these, the fourteenth lens element L14 and the fifteenth lens element L15 are cemented with each other. The sixteenth lens element L16 has two aspheric surfaces.
In the zoom lens system according to Embodiment 4, the sixth lens unit G6 comprises solely a positive meniscus seventeenth lens element L17 with the convex surface facing the object side. The seventeenth lens element L17 has two aspheric surfaces.
In the zoom lens system according to Embodiment 4, the eleventh lens element L11 and the twelfth lens element L12 in the fourth lens unit G4 correspond to an image blur compensating lens unit described later, which moves in a direction perpendicular to the optical axis in order to optically compensate image blur.
In the zoom lens system according to Embodiment 4, at the time of zooming from a wide-angle limit to a telephoto limit during image taking, the second lens unit G2 monotonically moves to the image side, the third lens unit G3 moves with locus of a convex to the object side, and the fifth lens unit G5 moves with locus of a convex to the image side so that its position is closer to the image side at a telephoto limit than at a wide-angle limit. Further, the first lens unit G1, the fourth lens unit G4, and the sixth lens unit G6 are fixed relative to the image surface S. That is, in zooming, the second lens unit G2, the third lens unit G3, and the fifth lens unit G5 individually move along the optical axis so that the interval between the first lens unit G1 and the second lens unit G2 and the interval between the fourth lens unit G4 and the fifth lens unit G5 increase, and the interval between the second lens unit G2 and the third lens unit G3 and the interval between the fifth lens unit G5 and the sixth lens unit G6 decrease.
Further, in the zoom lens system according to Embodiment 4, at the time of focusing from an infinity in-focus condition to a close-object in-focus condition, the second lens unit G2 does not move along the optical axis at a wide-angle limit, but moves to the object side along the optical axis in other zooming conditions. Further, at the time of focusing from the infinity in-focus condition to the close-object in-focus condition, the fifth lens unit G5 moves to the image side along the optical axis in all zooming conditions.
As shown in
In the zoom lens system according to Embodiment 5, the second lens unit G2, in order from the object side to the image side, comprises a bi-concave fourth lens element L4, a positive meniscus fifth lens element L5 with the convex surface facing the object side, and a bi-concave sixth lens element L6. Among these, the fourth lens element L4 and the fifth lens element L5 are cemented with each other.
In the zoom lens system according to Embodiment 5, the third lens unit G3, in order from the object side to the image side, comprises a positive meniscus seventh lens element L7 with the convex surface facing the object side, a negative meniscus eighth lens element L8 with the convex surface facing the object side, a positive meniscus ninth lens element L9 with the convex surface facing the object side, a bi-convex tenth lens element L10, and a negative meniscus eleventh lens element L11 with the convex surface facing the image side. Among these, the eighth lens element L8 and the ninth lens element L9 are cemented with each other, and the tenth lens element L10 and the eleventh lens element L11 are cemented with each other. The seventh lens element L7 has two aspheric surfaces, and the tenth lens element L10 has an aspheric object side surface. Further, an aperture diaphragm A is provided between the seventh lens element L7 and the eighth lens element L8.
In the zoom lens system according to Embodiment 5, the fourth lens unit G4 comprises solely a negative meniscus twelfth lens element L12 with the convex surface facing the object side. The fourth lens unit G4 is a lens unit having the greatest absolute value of optical power among all the lens units, as shown in Numerical Example 5 described later.
In the zoom lens system according to Embodiment 5, the fifth lens unit G5, in order from the object side to the image side, comprises a bi-convex thirteenth lens element L13, and a bi-concave fourteenth lens element L14.
In the zoom lens system according to Embodiment 5, the sixth lens unit G6 comprises solely a positive meniscus fifteenth lens element L15 with the convex surface facing the object side.
In the zoom lens system according to Embodiment 5, the tenth lens element L10 and the eleventh lens element L11 in the third lens unit G3 correspond to an image blur compensating lens unit described later, which moves in a direction perpendicular to the optical axis in order to optically compensate image blur.
In the zoom lens system according to Embodiment 5, at the time of zooming from a wide-angle limit to a telephoto limit during image taking, the second lens unit G2 monotonically moves to the image side, and the fourth lens unit G4 and the fifth lens unit G5 move to the object side with locus of a convex to the image side. The first lens unit G1, the third lens unit G3, and the sixth lens unit G6 are fixed relative to the image surface S. That is, in zooming, the second lens unit G2, the fourth lens unit G4, and the fifth lens unit G5 individually move along the optical axis so that the interval between the first lens unit G1 and the second lens unit G2 and the interval between the fifth lens unit G5 and the sixth lens unit G6 increase, and the interval between the second lens unit G2 and the third lens unit G3 and the interval between the third lens unit G3 and the fourth lens unit G4 decrease.
Further, in the zoom lens system according to Embodiment 5, at the time of focusing from an infinity in-focus condition to a close-object in-focus condition, the second lens unit G2 moves to the object side along the optical axis at a telephoto limit, but does not move along the optical axis in other zooming conditions. Further, at the time of focusing from the infinity in-focus condition to the close-object in-focus condition, the fourth lens unit G4 moves to the image side along the optical axis in all zooming conditions. Further, at the time of focusing from the infinity in-focus condition to the close-object in-focus condition, the fifth lens unit G5 moves to the image side along the optical axis in all zooming conditions.
As shown in
In the zoom lens system according to Embodiment 6, the second lens unit G2, in order from the object side to the image side, comprises a bi-concave fourth lens element L4, a positive meniscus fifth lens element L5 with the convex surface facing the object side, and a bi-concave sixth lens element L6. Among these, the fourth lens element L4 and the fifth lens element L5 are cemented with each other.
In the zoom lens system according to Embodiment 6, the third lens unit G3, in order from the object side to the image side, comprises a positive meniscus seventh lens element L7 with the convex surface facing the object side, a negative meniscus eighth lens element L8 with the convex surface facing the object side, a positive meniscus ninth lens element L9 with the convex surface facing the object side, a bi-convex tenth lens element L10, and a negative meniscus eleventh lens element L11 with the convex surface facing the image side. Among these, the eighth lens element L8 and the ninth lens element L9 are cemented with each other, and the tenth lens element L10 and the eleventh lens element L11 are cemented with each other. The seventh lens element L7 has two aspheric surfaces, and the tenth lens element L10 has an aspheric object side surface. Further, an aperture diaphragm A is provided between the seventh lens element L7 and the eighth lens element L8.
In the zoom lens system according to Embodiment 6, the fourth lens unit G4 comprises solely a negative meniscus twelfth lens element L12 with the convex surface facing the object side. The fourth lens unit G4 is a lens unit having the greatest absolute value of optical power among all the lens units, as shown in Numerical Example 6 described later.
In the zoom lens system according to Embodiment 6, the fifth lens unit G5, in order from the object side to the image side, comprises a bi-convex thirteenth lens element L13, and a bi-concave fourteenth lens element L14.
In the zoom lens system according to Embodiment 6, the sixth lens unit G6 comprises solely a positive meniscus fifteenth lens element L15 with the convex surface facing the object side.
In the zoom lens system according to Embodiment 6, the tenth lens element L10 and the eleventh lens element L11 in the third lens unit G3 correspond to an image blur compensating lens unit described later, which moves in a direction perpendicular to the optical axis in order to optically compensate image blur.
In the zoom lens system according to Embodiment 6, at the time of zooming from a wide-angle limit to a telephoto limit during image taking, the second lens unit G2 monotonically moves to the image side, and the fourth lens unit G4 and the fifth lens unit G5 move to the object side with locus of a convex to the image side. The first lens unit G1, the third lens unit G3, and the sixth lens unit G6 are fixed relative to the image surface S. That is, in zooming, the second lens unit G2, the fourth lens unit G4, and the fifth lens unit G5 individually move along the optical axis so that the interval between the first lens unit G1 and the second lens unit G2 and the interval between the fifth lens unit G5 and the sixth lens unit G6 increase, and the interval between the second lens unit G2 and the third lens unit G3 and the interval between the third lens unit G3 and the fourth lens unit G4 decrease.
Further, in the zoom lens system according to Embodiment 6, at the time of focusing from an infinity in-focus condition to a close-object in-focus condition, the second lens unit G2 moves to the object side along the optical axis at a telephoto limit, but does not move along the optical axis in other zooming conditions. Further, at the time of focusing from the infinity in-focus condition to the close-object in-focus condition, the fourth lens unit G4 moves to the image side along the optical axis in all zooming conditions. Further, at the time of focusing from the infinity in-focus condition to the close-object in-focus condition, the fifth lens unit G5 moves to the image side along the optical axis in all zooming conditions.
The zoom lens systems according to Embodiments 1 to 6, in order from the object side to the image side, comprise the first lens unit G1, the second lens unit G2, the third lens unit G3 and the subsequent lens units including at least the fourth lens unit G4, and the aperture diaphragm is either included in the third lens unit G3 or located on the image side relative to the third lens unit G3. Therefore, the aperture diameter is reduced, and thereby the unit size of the aperture diaphragm is reduced. In addition, since no aperture diaphragm is located on the object side relative to the third lens unit G3, the second lens unit G2 and the third lens unit G3 can be moved close to each other at a telephoto limit, and thus aberration compensation at the telephoto limit is facilitated. Furthermore, since the unit of the aperture diaphragm, which tends to have a large diameter, is located apart from the second lens unit G2, the actuator of the second lens unit G2 is easily arranged, and size reduction is achieved in the diameter direction of the lens barrel.
In the zoom lens systems according to Embodiments 1 to 6, the second lens unit G2 does not move along the optical axis at a wide-angle limit, but moves to the object side along the optical axis at a telephoto limit at the time of focusing from an infinity in-focus condition to a close-object in-focus condition. Slight deterioration of focusing performance of the second lens unit G2 at a wide-angle limit is offset with high focusing performance of one of the subsequent lens units. For example, in the zoom lens systems according to Embodiments 1 to 6, various aberrations can be sufficiently compensated in a balanced manner in addition to achievement of further excellent focusing performance in comparison with in conventional zoom lens systems in which focusing performance is achieved by moving only one focusing lens unit to the object side along the optical axis at a wide-angle limit. The amount of movement of the second lens unit G2 at the time of focusing easily becomes great, and the size of the actuator tends to be large. However, the actuator is easily arranged, and size reduction of the lens barrel is achieved since one of the subsequent lens units is the focusing lens unit. Moreover, the first lens unit G1 and the second lens unit G2 can be moved close to each other at a wide-angle limit in an infinity in-focus condition since the second lens unit G2 does not move at the time of focusing at a wide-angle limit. As a result, aberrations at a wide-angle limit can be easily compensated.
In the zoom lens systems according to Embodiments 1 to 6, since the first lens unit G1 is fixed relative to the image surface at the time of zooming from a wide-angle limit to a telephoto limit during image taking, weight reduction of the movable lens units is achieved, and thereby actuators can be arranged inexpensively. In addition, generation of noise during zooming is suppressed. Moreover, since the overall length of lens system is not changed, a user can easily operate the lens system, and entry of dust or the like into the lens system is sufficiently prevented.
In the zoom lens systems according to Embodiments 1 to 6, at the time of zooming from a wide-angle limit to a telephoto limit during image taking, the lens unit having the aperture diaphragm, i.e., the third lens unit G3 in Embodiments 1, 2, 5 and 6 or the fourth lens unit G4 in Embodiments 3 and 4, is fixed relative to the image surface. Therefore, the unit including the lens unit having the aperture diaphragm which is heavy in weight is not moved, and thereby the actuators can be arranged inexpensively.
In the zoom lens systems according to Embodiments 1 to 6, at the time of zooming from a wide-angle limit to a telephoto limit during image taking, the lens unit located closest to the image side, i.e., the fifth lens unit G5 in Embodiments 1 and 2 or the sixth lens unit G6 in Embodiments 3 to 6, is fixed relative to the image surface. Therefore, entry of dust or the like into the lens system is sufficiently prevented.
In the zoom lens systems according to Embodiments 1 to 6, the first lens unit G1 has positive optical power. Therefore, the size of the lens system is reduced. In addition, the amount of aberration caused by decentering of lens elements is reduced.
In the zoom lens systems according to Embodiments 1 to 6, at the time of focusing from an infinity in-focus condition to a close-object in-focus condition in the same zooming position from a wide-angle limit to a telephoto limit during image taking, the ratio of an amount of movement of a focusing lens unit α, which is one of the focusing lens units, to an amount of movement of a focusing lens unit β, which is one of the focusing lens units and is different from the focusing lens unit α, is constant regardless of the object distance. Therefore, focusing control is facilitated.
The zoom lens systems according to Embodiments 1 to 6 are each provided with an image blur compensating lens unit which moves in a direction perpendicular to the optical axis. The image blur compensating lens unit compensates image point movement caused by vibration of the entire system, that is, optically compensates image blur caused by hand blurring, vibration and the like.
When image point movement caused by vibration of the entire system is to be compensated, the image blur compensating lens unit moves in the direction perpendicular to the optical axis, so that image blur is compensated in a state that size increase in the entire zoom lens system is suppressed to realize a compact construction and that excellent imaging characteristics such as small decentering coma aberration and small decentering astigmatism are satisfied.
The image blur compensating lens unit according to the present invention may be a single lens unit. If a single lens unit is composed of a plurality of lens elements, the image blur compensating lens unit may be any one lens element or a plurality of adjacent lens elements among the plurality of lens elements.
The zoom lens systems according to Embodiments 1 and 2 have a five-unit construction including first to fifth lens units G1 to G5, and the zoom lens systems according to Embodiments 3 to 6 have a six-unit construction including first to sixth lens units G1 to G6. In the present invention, however, the number of lens units constituting the zoom lens system is not particularly limited so long as the zoom lens system comprises the first lens unit G1 to the third lens unit G3 and the subsequent lens units including at least the fourth lens unit G4, in which the aperture diaphragm is either included in the third lens unit G3 or located on the image side relative to the third lens unit G3, at least two among the all lens units are the movable lens units, at least two of the movable lens units are the focusing lens units, and at least the second lens unit G2 and one of the subsequent lens units are the focusing lens units. Further, the optical powers of the respective lens units constituting the zoom lens system are not particularly limited.
The following description is given for conditions preferred to be satisfied by a zoom lens system like the zoom lens systems according to Embodiments 1 to 6. Here, a plurality of preferable conditions are set forth for the zoom lens system according to each embodiment. A construction that satisfies all the plurality of conditions is most desirable for the zoom lens system. However, when an individual condition is satisfied, a zoom lens system having the corresponding effect is obtained.
For example, in a zoom lens system like the zoom lens systems according to Embodiments 1 to 6, which includes a plurality of lens units each comprising at least one lens element, in which the zoom lens system, in order from the object side to the image side, comprises a first lens unit, a second lens unit, a third lens unit and subsequent lens units including at least a fourth lens unit, an aperture diaphragm is either included in the third lens unit or located on the image side relative to the third lens unit, at least two among the first lens unit, the second lens unit, the third lens unit and the subsequent lens units are movable lens units which individually move along an optical axis at the time of zooming from a wide-angle limit to a telephoto limit during image taking, at least two of the movable lens units are focusing lens units which move along the optical axis at the time of focusing from an infinity in-focus condition to a close-object in-focus condition in at least one zooming position from a wide-angle limit to a telephoto limit, and at least the second lens unit and one of the subsequent lens units are the focusing lens units (this lens configuration is referred to as a basic configuration of the embodiments, hereinafter), the following condition (1) is preferably satisfied.
0.1<T1/fW<1.5 (1)
where
T1 is an axial thickness of the first lens unit, and
fW is a focal length of the entire system at a wide-angle limit.
The condition (1) sets forth the relationship between the axial thickness of the first lens unit and the focal length of the entire system at the wide-angle limit. When the value goes below the lower limit of the condition (1), the optical power of the first lens unit cannot be increased, and then the size of the zoom lens system might be increased. On the other hand, when the value exceeds the upper limit of the condition (1), the thickness of the first lens unit is increased, which also might result in an increase in the size of the zoom lens system.
When at least one of the following conditions (1)′ and (1)″ is satisfied, the above-mentioned effect is achieved more successfully.
0.17<T1/fW (1)′
T
1
/f
W<1.20 (1)″
For example, a zoom lens system having the basic configuration like the zoom lens systems according to Embodiments 1 to 6 preferably satisfies the following condition (2).
0.1<(T1+T2)/fW<2.5 (2)
where
T1 is an axial thickness of the first lens unit,
T2 is an axial thickness of the second lens unit, and
fW is a focal length of the entire system at a wide-angle limit.
The condition (2) sets forth the relationship between the sum of the axial thickness of the first lens unit and the axial thickness of the second lens unit, and the focal length of the entire system at a wide-angle limit. When the value goes below the lower limit of the condition (2), the optical powers of the lens units cannot be increased, and then the size of the zoom lens system might be increased. On the other hand, when the value exceeds the upper limit of the condition (2), the thicknesses of the lens units are increased. Also in this case, the size of the zoom lens system might be increased.
When at least one of the condition (2)′-1 or (2)′-2 and the condition (2)″-1 or (2)″-2 is satisfied, the above-mentioned effect is achieved more successfully.
0.20<(T1+T2)/fW (2)′-1
0.25<(T1+T2)/fW (2)′-2
(T1+T2)/fW<2.0 (2)″-1
(T1+T2)/fW<1.5 (2)″-2
For example, in a zoom lens system having the basic configuration like the zoom lens systems according to Embodiments 1 to 6, in which the second lens unit includes at least one lens element having positive optical power and at least one lens element having negative optical power, the following condition (3) is preferably satisfied.
νpνn<0 (3)
where
νp is an average of Abbe numbers to the d-line of the lens elements having positive optical power, and
νn is an average of Abbe numbers to the d-line of the lens elements having negative optical power.
The condition (3) sets forth the relationship in Abbe numbers between the positive lens elements and the negative lens elements, which constitute at least one focusing lens unit. When the condition (3) is satisfied, i.e., when the average of the Abbe numbers of the positive lens elements is less than the average of the Abbe numbers of the negative lens elements, aberrations, particularly chromatic aberration, do not vary very much even when the object distance varies.
When at least one of the following conditions (3)′ and (3)″ is satisfied, the above-mentioned effect is achieved more successfully.
νp−νn<−10.0 (3)′
−50.0<νp−νn (3)″
The individual lens units constituting the zoom lens systems according to Embodiments 1 to 6 are each composed exclusively of refractive type lens elements that deflect incident light by refraction (that is, lens elements of a type in which deflection is achieved at the interface between media having different refractive indices). However, the present invention is not limited to this construction. For example, the lens units may employ diffractive type lens elements that deflect incident light by diffraction; refractive-diffractive hybrid type lens elements that deflect incident light by a combination of diffraction and refraction; or gradient index type lens elements that deflect incident light by distribution of refractive index in the medium. In particular, in the refractive-diffractive hybrid type lens element, when a diffraction structure is formed in the interface between media having different refractive indices, wavelength dependence of the diffraction efficiency is improved. Thus, such a configuration is preferable.
The interchangeable-lens type digital camera system 100 according to Embodiment 7 includes a camera body 101, and an interchangeable lens apparatus 201 which is detachably connected to the camera body 101.
The camera body 101 includes: an image sensor 102 which receives an optical image formed by a zoom lens system 202 of the interchangeable lens apparatus 201, and converts the optical image into an electric image signal; a liquid crystal monitor 103 which displays the image signal obtained by the image sensor 102; and a camera mount section 104. On the other hand, the interchangeable lens apparatus 201 includes: a zoom lens system 202 according to any of Embodiments 1 to 6; a lens barrel 203 which holds the zoom lens system 202; and a lens mount section 204 connected to the camera mount section 104 of the camera body 101. The camera mount section 104 and the lens mount section 204 are physically connected to each other. Moreover, the camera mount section 104 and the lens mount section 204 function as interfaces which allow the camera body 101 and the interchangeable lens apparatus 201 to exchange signals, by electrically connecting a controller (not shown) in the camera body 101 and a controller (not shown) in the interchangeable lens apparatus 201. In
In Embodiment 7, since the zoom lens system 202 according to any of Embodiments 1 to 6 is employed, a compact interchangeable lens apparatus having excellent imaging performance can be realized at low cost. Moreover, size reduction and cost reduction of the entire camera system 100 according to Embodiment 7 can be achieved. In the zoom lens systems according to Embodiments 1 to 6, the entire zooming range need not be used. That is, in accordance with a desired zooming range, a range where satisfactory optical performance is obtained may exclusively be used. Then, the zoom lens system may be used as one having a lower magnification than the zoom lens systems described in Embodiments 1 to 6.
Numerical examples are described below in which the zoom lens systems according to Embodiments 1 to 6 are implemented. Here, in the numerical examples, the units of length are all “mm”, while the units of view angle are all “∘”. Moreover, in the numerical examples, r is the radius of curvature, d is the axial distance, nd is the refractive index to the d-line, and vd is the Abbe number to the d-line. In the numerical examples, the surfaces marked with * are aspherical surfaces, and the aspherical surface configuration is defined by the following expression.
Here, the symbols in the formula indicate the following quantities.
Z is a distance from a point on an aspherical surface at a height h relative to the optical axis to a tangential plane at the vertex of the aspherical surface,
h is a height relative to the optical axis,
r is a radius of curvature at the top,
κ is a conic constant, and
An is a n-th order aspherical coefficient.
In each longitudinal aberration diagram, part (a) shows the aberration at a wide-angle limit, part (b) shows the aberration at a middle position, and part (c) shows the aberration at a telephoto limit. Each longitudinal aberration diagram, in order from the left-hand side, shows the spherical aberration (SA (mm)), the astigmatism (AST (mm)) and the distortion (DIS (%)). In each spherical aberration diagram, the vertical axis indicates the F-number (in each Fig., indicated as F), and the solid line, the short dash line and the long dash line indicate the characteristics to the d-line, the F-line and the C-line, respectively. In each astigmatism diagram, the vertical axis indicates the image height (in each Fig., indicated as H), and the solid line and the dash line indicate the characteristics to the sagittal plane (in each Fig., indicated as “s”) and the meridional plane (in each Fig., indicated as “m”), respectively. In each distortion diagram, the vertical axis indicates the image height (in each Fig., indicated as H).
In each lateral aberration diagram, the aberration diagrams in the upper three parts correspond to a basic state where image blur compensation is not performed at a telephoto limit, while the aberration diagrams in the lower three parts correspond to an image blur compensation state where the image blur compensating lens unit (Examples 1 and 2: the tenth lens element L10 and the eleventh lens element L11 in the third lens unit G3, Examples 3 and 4: the eleventh lens element L11 and the twelfth lens element L12 in the fourth lens unit G4, Examples 5 and 6: the tenth lens element L10 and the eleventh lens element L11 in the third lens unit G3) is moved by a predetermined amount in a direction perpendicular to the optical axis at a telephoto limit. Among the lateral aberration diagrams of a basic state, the upper part shows the lateral aberration at an image point of 70% of the maximum image height, the middle part shows the lateral aberration at the axial image point, and the lower part shows the lateral aberration at an image point of −70% of the maximum image height. Among the lateral aberration diagrams of an image blur compensation state, the upper part shows the lateral aberration at an image point of 70% of the maximum image height, the middle part shows the lateral aberration at the axial image point, and the lower part shows the lateral aberration at an image point of −70% of the maximum image height. In each lateral aberration diagram, the horizontal axis indicates the distance from the principal ray on the pupil surface, and the solid line, the short dash line and the long dash line indicate the characteristics to the d-line, the F-line and the C-line, respectively. In each lateral aberration diagram, the meridional plane is adopted as the plane containing the optical axis of the first lens unit G1 and the optical axis of the third lens unit G3 (Examples 1, 2, 5 and 6) or the plane containing the optical axis of the first lens unit G1 and the optical axis of the fourth lens unit G4 (Examples 3 and 4).
In the zoom lens system according to each example, the amount of movement of the image blur compensating lens unit in a direction perpendicular to the optical axis in the image blur compensation state at a telephoto limit is as follows.
When the shooting distance is infinity, at a telephoto limit, the amount of image decentering in a case that the zoom lens system inclines by 0.3° is equal to the amount of image decentering in a case that the image blur compensating lens unit displaces in parallel by each of the above-mentioned values in a direction perpendicular to the optical axis.
As seen from the lateral aberration diagrams, satisfactory symmetry is obtained in the lateral aberration at the axial image point. Further, when the lateral aberration at the +70% image point and the lateral aberration at the −70% image point are compared with each other in the basic state, all have a small degree of curvature and almost the same inclination in the aberration curve. Thus, decentering coma aberration and decentering astigmatism are small. This indicates that sufficient imaging performance is obtained even in the image blur compensation state. Further, when the image blur compensation angle of a zoom lens system is the same, the amount of parallel translation required for image blur compensation decreases with decreasing focal length of the entire zoom lens system. Thus, at arbitrary zoom positions, sufficient image blur compensation can be performed for image blur compensation angles up to 0.3° without degrading the imaging characteristics.
The zoom lens system of Numerical Example 1 corresponds to Embodiment 1 shown in
The zoom lens system of Numerical Example 2 corresponds to Embodiment 2 shown in
The zoom lens system of Numerical Example 3 corresponds to Embodiment 3 shown in
The zoom lens system of Numerical Example 4 corresponds to Embodiment 4 shown in
The zoom lens system of Numerical Example 5 corresponds to Embodiment 5 shown in
The zoom lens system of Numerical Example 6 corresponds to Embodiment 6 shown in
The following Table 25 shows the corresponding values to the individual conditions in the zoom lens systems of each of Numerical Examples.
48
The zoom lens system according to the present invention is applicable to a digital still camera, a digital video camera, a camera for a mobile telephone, a camera for a PDA (Personal Digital Assistance), a surveillance camera in a surveillance system, a Web camera, a vehicle-mounted camera or the like. In particular, the zoom lens system according to the present invention is suitable for a photographing optical system where high image quality is required like in a digital still camera system or a digital video camera system.
Also, the zoom lens system according to the present invention is applicable to, among the interchangeable lens apparatuses according to the present invention, an interchangeable lens apparatus having motorized zoom function, i.e., activating function for the zoom lens system by a motor, with which a digital video camera system is provided.
Although the present invention has been fully described by way of example with reference to the accompanying drawings, it is to be understood that various changes and modifications will be apparent to those skilled in the art. Therefore, unless otherwise such changes and modification depart from the scope of the present invention, they should be construed as being included therein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-065050 | Mar 2010 | JP | national |
