# Patent

## Title
Zoom lens system, interchangeable lens apparatus and camera system

## Abstract

Provided is a zoom lens system including a compact focusing lens unit and having a suppressed change in image magnification at the time of movement of the focusing lens unit. The zoom lens system of the present invention includes, in order from an object side to an image side, a first lens unit G1 having negative optical power, a second lens unit G2 having positive optical power, a third lens unit G3 having positive optical power, and a fourth lens unit G4 having negative optical power. The fourth lens unit G4 moves to the image side along an optical axis at the time of focusing from an infinity in-focus condition to a close-point in-focus condition.

## Background
CROSS-REFERENCE TO RELATED APPLICATION
This application is based on Japanese Patent Application Nos. 2009-021832 and 2009-021833 filed on Feb. 2, 2009. Hereby, the contents of Japanese Patent Application Nos. 2009-021832 and 2009-021833 are incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a zoom lens system and, in particular, to a zoom lens system suitable for an imaging lens system employed in an interchangeable lens apparatus in a so-called interchangeable-lens type digital camera system. Further, the present invention relates to an interchangeable lens apparatus and a camera system that employ this zoom lens system.
2. Description of the Background Art
In recent years, interchangeable-lens type digital camera systems are rapidly spreading. The interchangeable-lens type digital camera system (also simply referred to as “camera system”) is a camera system including: a camera body employing an image sensor composed of a CCD (Charge Coupled Device), a CMOS (Complementary Metal-Oxide Semiconductor), or the like; and an interchangeable lens apparatus employing an imaging lens system for forming an optical image on the light acceptance surface of the image sensor. Zoom lens systems applicable to the above interchangeable-lens type digital camera are disclosed in Japanese Laid-Open Patent Publication No. 2005-284097, Japanese Laid-Open Patent Publication No. 2005-352057, Japanese Laid-Open Patent Publication No. 2006-221092, Japanese Laid-Open Patent Publication No. 2005-316396, Japanese Laid-Open Patent Publication No. 2006-267425, Japanese Laid-Open Patent Publication No. 2007-219315, Japanese Laid-Open Patent Publication No. 2008-3195, and Japanese Laid-Open Patent Publication No. 2008-15251.
On the other hand, there are interchangeable-lens type digital camera systems employing a function of displaying image data generated by the imaging lens system or the image sensor on a display unit such as a liquid crystal display or the like of a camera body (hereinafter referred to as “live view function”) (e.g., Japanese Laid-Open Patent Publication No. 2000-111789 and Japanese Laid-Open Patent Publication No. 2000-333064).
SUMMARY OF THE INVENTION
In the camera system disclosed in Japanese Laid-Open Patent Publication No. 2000-111789 and Japanese Laid-Open Patent Publication No. 2000-333064, when the live view function is being performed, a contrast AF method is employed to perform focusing operation. The contrast AF is the focusing operation based on the contrast value of image data obtained from the image sensor. Hereinafter, an operation of the contrast AF will be described.
First, the camera system oscillates the focusing lens unit in the optical axis direction at a high-speed (hereinafter referred to as “wobbling”) thereby to detect the direction of displacement from an in-focus condition. After the wobbling, the camera system detects, from an output signal of the image sensor, signal components in a predetermined frequency band in an image region and calculates an optimal position of the focusing lens unit for realizing the in-focus condition. Thereafter, the camera system moves the focusing lens unit to the optimal position, and completes the focusing operation. When the focusing operation is performed continuously in video image taking or the like, the camera system repeats a series of the above operations.
Generally, in order that uneasiness such as flickers should be avoided, video displaying need be performed at a high rate of, for example, 30 frames per second. Thus, basically, video image taking using the interchangeable-lens type digital camera also need be performed at the same rate of 30 frames per second. Accordingly, the focusing lens unit need be driven at the high rate of 30 Hz at the time of wobbling.
However, if the weight of the focusing lens unit is large, a larger motor or actuator is required to move the focusing lens unit at a high rate. This causes a problem that the outer diameter of the lens barrel is increased. However, in the case of the zoom lens systems disclosed in the above conventional arts, the focusing lens unit is hardly light-weighted.
Further, in the interchangeable-lens type digital camera, it should be noted that the size of the image corresponding to a photographic object varies in association with wobbling. This variation in the image is caused mainly by the fact that the movement of the focusing lens unit in the optical axis direction generates a change in the focal length of the entire lens system. Then, when a large change in the image taking magnification is generated in association with wobbling, the image taking person will feel uneasiness.
An object of the present invention is to provide a zoom lens system which includes a compactly constructed focusing lens unit and which has a suppressed change in the image magnification at the time of movement of the focusing lens unit, and an interchangeable lens apparatus and a camera system which employ this zoom lens system.
A zoom lens system according to the present invention includes a plurality of lens units and performs zooming by changing intervals among the lens units. The plurality of lens units, in order from an object side to an image side, includes: a first lens unit having negative optical power; a second lens unit having positive optical power; a third lens unit having positive optical power; and a fourth lens unit having negative optical power. The fourth lens unit moves to the image side along an optical axis at the time of focusing from an infinity in-focus condition to a close-point in-focus condition.
Further, another zoom lens system according to the present invention includes a plurality of lens units and performs zooming by changing intervals among the lens units. The plurality of lens units, in order from an object side to an image side, includes: a first lens unit having negative optical power; a second lens unit having negative optical power; a third lens unit having positive optical power; a fourth lens unit having positive optical power; and a fifth lens unit having negative optical power. The fifth lens unit moves to the image side along an optical axis at the time of focusing from an infinity in-focus condition to a close-point in-focus condition.
Still another zoom lens system according to the present invention includes a plurality of lens units and performs zooming by changing intervals among the lens units. The plurality of lens units, in order from an object side to an image side, includes: a first lens unit having negative optical power; a second lens unit having positive optical power; a third lens unit; and a fourth lens unit. The first lens unit, in order from the object side to the image side, includes: a negative meniscus first lens element having negative optical power and having a concave surface facing the image side; a negative meniscus second lens element having negative optical power and having a concave surface facing the image side; and a negative meniscus third lens element having negative optical power and having a concave surface facing the image side. At least one lens element included in the first lens unit is an aspheric lens.
Further, an interchangeable lens apparatus according to the present invention includes: any of the above zoom lens system, and a mount section connected to a camera body that includes an image sensor which receives an optical image formed by the zoom lens system thereby to convert the optical image to an electrical image signal.
A camera system according to the present invention includes: an interchangeable lens apparatus that includes any of the above zoom lens system, and a camera body which is connected to the interchangeable lens apparatus via a camera mount section in an attachable and removable manner and includes an image sensor which receives an optical image formed by the zoom lens system thereby to convert the optical image to an electrical image signal.
According to the present invention, it is possible to provide a zoom lens system which includes a compactly constructed focusing lens unit and which has a suppressed change in image magnification at the time of movement of the focusing lens unit, and an interchangeable lens apparatus and a camera system which employ the zoom lens system.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a lens arrangement diagram showing an infinity in-focus condition of a zoom lens system according to Embodiment 1 (Example 1);
FIG. 2 is a longitudinal aberration diagram showing an infinity in-focus condition of a zoom lens system according to Example 1;
FIG. 3 is a lens arrangement diagram showing an infinity in-focus condition of a zoom lens system according to Embodiment 2 (Example 2);
FIG. 4 is a longitudinal aberration diagram showing an infinity in-focus condition of a zoom lens system according to Example 2;
FIG. 5 is a lens arrangement diagram showing an infinity in-focus condition of a zoom lens system according to Embodiment 3 (Example 3);
FIG. 6 is a longitudinal aberration diagram showing an infinity in-focus condition of a zoom lens system according to Example 3;
FIG. 7 is a lens arrangement diagram showing an infinity in-focus condition of a zoom lens system according to Embodiment 4 (Example 4);
FIG. 8 is a longitudinal aberration diagram showing an infinity in-focus condition of a zoom lens system according to Example 4;
FIG. 9 is a lens arrangement diagram showing an infinity in-focus condition of a zoom lens system according to Embodiment 5 (Example 5);
FIG. 10 is a longitudinal aberration diagram showing an infinity in-focus condition of a zoom lens system according to Example 5;
FIG. 11 is a lens arrangement diagram showing an infinity in-focus condition of a zoom lens system according to Embodiment 6 (Example 6);
FIG. 12 is a longitudinal aberration diagram showing an infinity in-focus condition of a zoom lens system according to Example 6;
FIG. 13 is a lens arrangement diagram showing an infinity in-focus condition of a zoom lens system according to Embodiment 7 (Example 7);
FIG. 14 is a longitudinal aberration diagram showing an infinity in-focus condition of a zoom lens system according to Example 7;
FIG. 15 is a lens arrangement diagram showing an infinity in-focus condition of a zoom lens system according to Embodiment 8 (Example 8);
FIG. 16 is a longitudinal aberration diagram showing an infinity in-focus condition of a zoom lens system according to Example 8; and
FIG. 17 is a schematic construction diagram of an interchangeable-lens type digital camera system according to Embodiment 9.



DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIGS. 1, 3, 5, 7, 9, 11, 13 and 15 show lens arrangement diagrams of zoom lens systems according to Embodiments 1, 2, 3, 4, 5, 6, 7 and 8, respectively, and each show a zoom lens system in a infinity in-focus condition.
In each diagram, 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=√{square root over ( )}(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 diagram, each bend arrow located between part (a) and part (b) indicates a line obtained by connecting the positions of the lens units 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 diagram, an arrow imparted to a lens unit indicates focusing from an infinity in-focus condition to a close-object in-focus condition. That is, the arrow indicates the moving direction at the time of focusing from an infinity in-focus condition to a close-object in-focus condition.
In FIGS. 1, 3, 5, 7, 9, 11, 13, and 15, asterisk “*” imparted to a particular surface indicates that the surface is aspheric. Further, in each diagram, symbol (+) or symbol (−) imparted to the symbol of each lens unit corresponds to the sign of the optical power of the lens unit. Still further, in each diagram, the straight line located on the most right-hand side indicates the position of the image surface S. Still further, in each diagram, the straight line located between adjoining lens elements indicates the position of an aperture diaphragm A.
(Embodiment 1)
The zoom lens system according to Embodiment 1, in order from the object side to the image side, includes a first lens unit G1 having negative optical power, a second lens unit G2 having positive 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.
The first lens unit G1, in order from the object side to the image side, includes: a negative meniscus first lens element L1 with the convex surface facing the object side; a negative meniscus second lens element L2 with the convex surface facing the object side; a negative meniscus third lens element L3 with the convex surface facing the object side; a bi-concave fourth lens element L4; and a positive meniscus fifth lens element L5 with the convex surface facing the object side. A surface of the third lens element L3 facing the image side is aspheric.
The second lens unit G2, in order from the object side to the image side, includes: a negative meniscus sixth lens element L6 with the convex surface facing the object side; and a positive meniscus seventh lens element L7 with the convex surface facing the object side. The sixth lens element L6 and the seventh lens element L7 are cemented with each other.
The third lens unit G3, in order from the object side to the image side, includes: a negative meniscus eighth lens element L8 with the convex surface facing the object side; a bi-convex ninth lens element L9; a bi-concave tenth lens element L10; a bi-convex eleventh lens element L11; a positive meniscus twelfth lens element L12 with the convex surface facing the image side; and a bi-convex thirteenth lens element L13. The eighth lens element L8 and the ninth lens element L9 are cemented with each other. In addition, the tenth lens element L10 and the eleventh lens element L11 are cemented with each other.
The fourth lens unit G4 consists of a negative meniscus fourteenth lens element L14 with the convex surface facing the object side.
The fifth lens unit G5, in order from the object side to the image side, includes: a negative meniscus fifteenth lens element L15 with the convex surface facing the object side; and a bi-convex sixteenth lens element L16. The fifteenth lens element L15 and the sixteenth lens element L16 are cement with each other. A surface of the sixteenth lens element L16 facing the image side is aspheric.
At the time of zooming, the plurality of lens units move along the optical axis such that: the interval between the first lens unit G1 and the second lens unit G2 at a telephoto limit is made shorter than the interval at a wide-angle limit; the interval between the second lens unit G2 and the third lens unit G3 at a telephoto limit is made shorter than the interval at a wide-angle limit; the interval between the third lens unit G3 and the fourth lens unit G4 at a telephoto limit is made shorter than the interval at a wide-angle limit; and the interval between the fourth lens unit G4 and the fifth lens unit G5 at a telephoto limit is made longer than the interval at a wide-angle limit. More specifically, at the time of zooming from a wide-angle limit to a telephoto limit, the first lens unit G1 moves to the image side along the optical axis, whereas the second lens unit G2, the third lens unit G3, and the fourth lens unit G4 move to the object side along the optical axis. The fifth lens unit G5 is fixed relative to the image surface S at the time of zooming. The aperture diaphragm A moves to the object side together with the second lens unit G2.
Further, at the time of focusing from an infinity in-focus condition to a close-point in-focus condition, the fourth lens unit G4 moves to the image side along the optical axis.
(Embodiment 2)
The zoom lens system according to Embodiment 2, in order from the object side to the image side, includes a first lens unit G1 having negative optical power, a second lens unit G2 having positive 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.
The first lens unit G1, in order from the object side to the image side, includes: a negative meniscus first lens element L1 with the convex surface facing the object side; a negative meniscus second lens element L2 with the convex surface facing the object side; a negative meniscus third lens element L3 with the convex surface facing the object side; a bi-concave fourth lens element L4; and a positive meniscus fifth lens element L5 with the convex surface facing the object side. The fourth lens element L4 and the fifth lens element L5 are cemented with each other. Further, a surface of the third lens element L3 facing the image side is aspheric.
The second lens unit G2, in order from the object side to the image side, includes: a negative meniscus sixth lens element L6 with the convex surface facing the object side; and a positive meniscus seventh lens element L7 with the convex surface facing the object side. The sixth lens element L6 and the seventh lens element L7 are cemented with each other.
The third lens unit G3, in order from the object side to the image side, includes: a negative meniscus eighth lens element L8 with the convex surface facing the object side; a bi-convex ninth lens element L9; a bi-concave tenth lens element L10, a bi-convex eleventh lens element L11, a positive meniscus twelfth lens element L12 with the convex surface facing the image side; and a bi-convex thirteenth lens element L13. The eighth lens element L8 and the ninth lens element L9 are cemented with each other. In addition, the tenth lens element L10 and the eleventh lens element L11 are cemented with each other.
The fourth lens unit G4 consists of a negative meniscus fourteenth lens element L14 with the convex surface facing the object side.
The fifth lens unit G5, in order from the object side to the image side, includes: a negative meniscus fifteenth lens element L15 with the convex surface facing the object side; and a bi-convex sixteenth lens element L16. The fifteenth lens element L15 and the sixteenth lens element L16 are cemented with each other. Further, a surface of the sixteenth lens element L16 facing the image side is aspheric.
At the time of zooming, the plurality of lens units move along the optical axis such that: the interval between the first lens unit G1 and the second lens unit G2 at a telephoto limit is made shorter than the interval at a wide-angle limit; the interval between the second lens unit G2 and the third lens unit G3 at a telephoto limit is made shorter than the interval at a wide-angle limit; the interval between the third lens unit G3 and the fourth lens unit G4 at a telephoto limit is made shorter than the interval at a wide-angle limit; and the interval between the fourth lens unit G4 and the fifth lens unit G5 at a telephoto limit is made longer than the interval in a wide-angle limit. More specifically, at the timing of zooming from a wide-angle limit to a telephoto limit, the first lens unit G1 moves to the image side along the optical axis, whereas the second lens unit G2, third lens unit G3, and the fourth lens unit G4 move to the object side along the optical axis. The fifth lens unit G5 is fixed relative to the image surface S at the time of zooming. The aperture diaphragm A moves to the object side together with the second lens unit G2.
Further, at the time of focusing from an infinity in-focus condition to a close-point in-focus condition, the fourth lens unit G4 moves to the image side along the optical axis.
(Embodiment 3)
The zoom lens system according to Embodiment 3, in order from the object side to the image side, includes: a first lens unit G1 having negative optical power, a second lens unit G2 having positive 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.
The first lens unit G1, in order from the object side to the image side, includes: a negative meniscus first lens element L1 with the convex surface facing the object side; a negative meniscus second lens element L2 with the convex surface facing the object side; a negative meniscus third lens element L3 with the convex surface facing the object side; a bi-concave fourth lens element L4; and a positive meniscus fifth lens element L5 with the convex surface facing the object side. The fourth lens element L4 and the fifth lens element L5 are cemented with each other. A surface of the third lens element L3 facing the image side is aspheric.
The second lens unit G2, in order from the object side to the image side, includes: a negative meniscus sixth lens element L6 with the convex surface facing the object side; and a positive meniscus seventh lens element L7 with the convex surface facing the object side. The sixth lens element L6 and the seventh lens element L7 are cemented with each other.
The third lens unit G3, in order from the object side to the image side, includes: a plano-concave eighth lens element L8 with the concave surface facing the image side; a bi-convex ninth lens element L9; a bi-concave tenth lens element L10; a bi-convex eleventh lens element L11; and a bi-convex twelfth lens element L12. The eighth lens element L8 and the ninth lens element L9 are cemented with each other. In addition, the tenth lens element L10 and the eleventh lens element L11 are cemented with each other.
The fourth lens unit G4 consists of a negative meniscus thirteenth lens element L13 with the convex surface facing the object side.
The fifth lens unit G5, in order from the object side to the image side, includes: a bi-concave fourteenth lens element L14; and a bi-convex fifteenth lens element L15. The fourteenth lens element L14 and the fifteenth lens element L15 are cemented with each other. Further, a surface of the fifteenth lens element L15 facing the image side is aspheric.
At the time of zooming, the plurality of lens units move along the optical axis such that: the interval between the first lens unit G1 and the second lens unit G2 at a telephoto limit is made shorter than the interval at a wide-angle limit; the interval between the second lens unit G2 and the third lens unit G3 at a telephoto limit hardly changes from the interval at a wide-angle limit; the interval between the third lens unit G3 and the fourth lens unit G4 at a telephoto limit is made shorter than the interval at a wide-angle limit; and the interval between the fourth lens unit G4 and the fifth lens unit G5 at a telephoto limit is made longer than the interval at a wide-angle limit. More specifically, at the time of zooming from a wide-angle limit to a telephoto limit, the first lens unit G1 moves to the image side along the optical axis, whereas the second lens unit G2, the third lens unit G3, and the fourth lens unit G4 move to the object side along the optical axis. The fifth lens unit G5 is fixed relative to the image surface S at the time of zooming. The aperture diaphragm A moves to the object side together with the second lens unit G2.
Further, at the time of focusing from an infinity in-focus condition to a close-point in-focus condition, the fourth lens unit G4 moves to the image side along the optical axis.
(Embodiment 4)
The zoom lens system according to Embodiment 4, in order from the object side to the image side, includes a first lens unit G1 having negative optical power, a second lens unit G2 having positive 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.
The first lens unit G1, in order from the object side to the image side, includes: a negative meniscus first lens element L1 with the convex surface facing the object side; a negative meniscus second lens element L2 with the convex surface facing the object side; a negative meniscus third lens element L3 with the convex surface facing the object side; an bi-concave fourth lens element L4; and a positive meniscus fifth lens element L5 with the convex surface facing the object side. The fourth lens element L4 and the fifth lens element L5 are cemented with each other. Further, a surface of the third lens element L3 facing the image side is aspheric.
The second lens unit G2, in order from the object side to the image side, includes: a negative meniscus sixth lens element L6 with the convex surface facing the object side; and a positive meniscus seventh lens element L7 with the convex surface facing the object side. The sixth lens element L6 and the seventh lens element L7 are cemented with each other. A surface of the seventh lens element L7 facing the image side is aspheric.
The third lens unit G3, in order from the object side to the image side, includes: a negative meniscus eighth lens element L8 with the convex surface facing the object side; a bi-convex ninth lens element L9; a bi-concave tenth lens element L10; a bi-convex eleventh lens element L11; and a bi-convex twelfth lens element L12. The eighth lens element L8 and the ninth lens element L9 are cemented with each other. In addition, the tenth lens element L10 and the eleventh lens element L11 are cemented with each other.
The fourth lens unit G4 consists of a negative meniscus thirteenth lens element L13 with the convex surface facing the object side.
The fifth lens unit G5, in order from the object side to the image side, includes: a bi-concave fourteenth lens element L14; and a bi-convex fifteenth lens element L15. The fourteenth lens element L14 and the fifteenth lens element L15 are cemented with each other. Further, a surface of the fifteenth lens element L15 facing the image side is aspheric.
At the time of zooming, the plurality of lens units move along the optical axis such that: the interval between the first lens unit G1 and the second lens unit G2 at a telephoto limit is made shorter than the interval at a wide-angle limit; the interval between the second lens unit G2 and the third lens unit G3 at a telephoto limit is made shorter than the interval at a wide-angle limit; the interval between the third lens unit G3 and the fourth lens unit G4 at a telephoto limit hardly changes from the interval at a wide-angle limit; and the interval between the fourth lens unit G4 and the fifth lens unit G5 at a telephoto limit is made longer than the interval at a wide-angle limit. More specifically, at the time of zooming from a wide-angle limit to a telephoto limit, the first lens unit G1 moves to the image side along the optical axis, whereas the second lens unit G2, the third lens unit G3, and the fourth lens unit G4 move to the object side along the optical axis. The fifth lens unit G5 is fixed relative to the image surface S at the time of zooming. The aperture diaphragm A moves to the object side together with the second lens unit G2.
Further, at the time of focusing from an infinity in-focus condition to a close-point in-focus condition, the fourth lens unit G4 moves to the image side along the optical axis.
(Embodiment 5)
The zoom lens system according to Embodiment 5, in order from the object side to the image side, includes, a first lens unit G1 having negative optical power, a second lens unit G2 having positive 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.
The first lens unit G1, in order from the object side to the image side, includes: a negative meniscus first lens element L1 with the convex surface facing the object side; a negative meniscus second lens element L2 with the convex surface facing the object side; a negative meniscus third lens element L3 with the convex surface facing the object side; a bi-concave fourth lens element L4; and a positive meniscus fifth lens element L5 with the convex surface facing the object side. The fourth lens element L4 and the fifth lens element L5 are cemented with each other. A surface of the third lens element L3 facing the image side is aspheric.
The second lens unit G2, in order from the object side to the image side, includes: a negative meniscus sixth lens element L6 with the convex surface facing the object side; and a positive meniscus seventh lens element L7 with the convex surface facing the object side. The sixth lens element L6 and the seventh lens element L7 are cemented with each other. Further, a surface of the seventh lens element L7 facing the image side is aspheric.
The third lens unit G3, in order from the object side to the image side, includes: a bi-concave eighth lens element L8; a bi-convex ninth lens element L9; a bi-concave tenth lens element L10; a bi-convex eleventh lens element L11; and a bi-convex twelfth lens element L12. The eighth lens element L8 and the ninth lens element L9 are cemented with each other. In addition, the tenth lens element L10 and the eleventh lens element L11 are cemented with each other.
The fourth lens unit G4 consists of a negative meniscus thirteenth lens element L13 with the convex surface facing the object side.
The fifth lens unit G5, in order from the object side to the image side, includes: a negative meniscus fourteenth lens element L14 with the convex surface facing the object side; and a bi-convex fifteenth lens element L15. A surface of the fifteenth lens element L15 facing the image side is aspheric.
At the time of zooming, the plurality of lens units move along the optical axis such that: the interval between the first lens unit G1 and the second lens unit G2 at a telephoto limit is made shorter than the interval at a wide-angle limit; the interval between the second lens unit G2 and the third lens unit G3 at a telephoto limit is made shorter than the interval at a wide-angle limit; the interval between the third lens unit G3 and the fourth lens unit G4 at a telephoto limit hardly changes from the interval at a wide-angle limit; and the interval between the fourth lens unit G4 and the fifth lens unit G5 at a telephoto limit is made longer than the interval at a wide-angle limit. More specifically, at the time of zooming from a wide-angle limit to a telephoto limit, the first lens unit G1 moves to the image side along the optical axis, whereas the second lens unit G2, the third lens unit G3, and the fourth lens unit G4 move to the object side along the optical axis. The fifth lens unit G5 is fixed relative to the image surface S at the time of zooming. The aperture diaphragm A moves to the object side together with the second lens unit G2.
Further, at the time of focusing from an infinity in-focus condition to a close-point in-focus condition, the fourth lens unit G4 moves to the image side along the optical axis.
(Embodiment 6)
The zoom lens system according to Embodiment 6, in order from the object side to the image side, includes a first lens unit G1 having negative 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 positive optical power, a fifth lens unit G5 having negative optical power, and a sixth lens unit G6 having positive optical power.
The first lens unit G1, in order from the object side to the image side, includes: a negative meniscus first lens element L1 with the convex surface facing the object side; a negative meniscus second lens element L2 with the convex surface facing the object side; and a negative meniscus third lens element L3 with the convex surface facing the object side. A surface of the third lens element L3 facing the image side is aspheric.
The second lens unit G2, in order from the object side to the image side, includes: a negative meniscus fourth lens element L4 with the convex surface facing the object side; and a positive meniscus fifth lens element L5 with the convex surface facing the object side.
The third lens unit G3, in order from the object side to the image side, includes: a bi-convex sixth lens element L6; and a negative meniscus seventh lens element L7 with the convex surface facing the image side. The sixth lens element L6 and the seventh lens element L7 are cemented with each other. Further, a surface of the sixth lens element L6 facing the object side is aspheric.
The fourth lens unit G4, in order from the object side to the image side, includes: a negative meniscus eighth lens element L8 with the convex surface facing the object side; a bi-convex ninth lens element L9; a bi-concave tenth lens element L10; a bi-convex eleventh lens element L11; and a bi-convex twelfth lens element L12. The eighth lens element L8 and the ninth lens element L9 are cemented with each other. In addition, the tenth lens element L10 and the eleventh lens element L11 are cemented with each other.
The fifth lens unit G5 consists of a negative meniscus thirteenth lens element L13 with the convex surface facing the object side.
The sixth lens unit G6 includes a bi-convex fourteenth lens element L14, a bi-concave fifteenth lens element L15, and a bi-convex sixteenth lens element L16. The fourteenth lens element L14 and the fifteenth lens element L15 are cemented with each other. A surface of the sixteenth lens element L16 facing the image side is aspheric.
At the time of zooming, the plurality of lens units move along the optical axis such that: the interval between the first lens unit G1 and the second lens unit G2 at a telephoto limit hardly changes from the interval at a wide-angle limit; the interval between the second lens unit G2 and the third lens unit G3 at a telephoto limit is made shorter than the interval at a wide-angle limit; the interval between the third lens unit G3 and the fourth lens unit G4 at a telephoto limit is made shorter than the interval at a wide-angle limit; the interval between the fourth lens unit G4 and the fifth lens unit G5 at a telephoto limit hardly changes from the interval at a wide-angle limit; and the interval between the fifth lens unit G5 and the sixth lens unit G6 at a telephoto limit is made longer than the interval at a wide-angle limit. More specifically, at the time of zooming from a wide-angle limit to a telephoto limit, the first lens unit G1 and the second lens unit G2 move to the image side along the optical axis, whereas the third lens unit G3, the fourth lens unit G4, and the fifth lens unit G5 move to the object side along the optical axis. The sixth lens unit G6 is fixed relative to the image surface S at the time of zooming. The aperture diaphragm A moves to the object side together with the third lens unit G3.
Further, at the time of focusing from an infinity in-focus condition to a close-point in-focus condition, the fifth lens unit G5 moves to the image side along the optical axis.
(Embodiment 7)
The zoom lens system according to Embodiment 7, in order from the object side to the image side, includes a first lens unit G1 having negative optical power, second lens unit G2 having positive 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.
The first lens unit G1, in order from the object side to the image side, includes: a negative meniscus first lens element L1 with the convex surface facing the object side; a negative meniscus second lens element L2 with the convex surface facing the object side; a negative meniscus third lens element L3 with the convex surface facing the object side; a bi-concave fourth lens element L4; and a positive meniscus fifth lens element L5 with the convex surface facing the object side. A surface of the first lens element L1 facing the image side and a surface of the third lens element L3 facing the image side are aspheric. Further, the fourth lens element L4 and the fifth lens element L5 are cemented with each other.
The first lens element L1 is a hybrid lens obtained by cementing a transparent resin layer formed of a UV cured resin onto a lens element made of glass. The hybrid lens has an aspheric surface formed of a transparent resin layer. Accordingly, it is possible to form a large diameter aspheric surface which is difficult to obtain by only press-molding of glass. Further, as compared to the case where the lens element is formed of a resin only, the hybrid lens is stable against temperature variation in terms of both refractive-index variation and shape variation, and thus it is possible to provide a lens element having a high refractive index.
The second lens unit G2, in order from the object side to the image side, includes: a negative meniscus sixth lens element L6 with the convex surface facing the object side; and a positive meniscus seventh lens element L7 with the convex surface facing the object side. The sixth lens element L6 and the seventh lens element L7 are cemented with each other.
The third lens unit G3, in order from the object side to the image side, includes: a negative meniscus eighth lens element L8 with the convex surface facing the object side; a bi-convex ninth lens element L9; a plano-concave tenth lens element L10 with the concave surface facing the object side; a plano-convex eleventh lens element L11 with the convex surface facing the object side; a positive meniscus twelfth lens element L12 with the convex surface facing the image side; and a bi-convex thirteenth lens element L13. The eighth lens element L8 and the ninth lens element L9 are cemented with each other. In addition, the tenth lens element L10 and the eleventh lens element L11 are cemented with each other.
The fourth lens unit G4 consists of a negative meniscus fourteenth lens element L14 with the convex surface facing the object side.
The fifth lens unit G5, in order from the object side to the image side, includes: a bi-concave fifteenth lens element L15; and a bi-convex sixteenth lens element L16. The fifteenth lens element L15 and the sixteenth lens element L16 are cemented with each other. Further, a surface of the sixteenth lens element L16 facing the image side is aspheric.
At the time of zooming, the plurality of lens units move along the optical axis such that: the interval between the first lens unit G1 and the second lens unit G2 at a telephoto limit is made shorter than the interval at a wide-angle limit; the interval between the second lens unit G2 and the third lens unit G3 at a telephoto limit is made shorter than the interval at a wide-angle limit; the interval between the third lens unit G3 and the fourth lens unit G4 at a telephoto limit is made shorter than the interval at a wide-angle limit; and the interval between the fourth lens unit G4 and the fifth lens unit G5 at a telephoto limit is made longer than the interval at a wide-angle limit. More specifically, at the time of zooming from a wide-angle limit to a telephoto limit, the first lens unit G1 moves to the image side along the optical axis, whereas the second lens unit G2, the third lens unit G3, and the fourth lens unit G4 move to the object side along the optical axis. The fifth lens unit G5 is fixed relative to the image surface S at the time of zooming. The aperture diaphragm A moves to the object side together with the second lens unit G2.
Further, at the time of focusing from an infinity in-focus condition to a close-point in-focus condition, the fourth lens unit G4 moves to the image side along the optical axis.
(Embodiment 8)
The zoom lens system according to Embodiment 8, in order from the object side to the image side, includes a first lens unit G1 having negative optical power, a second lens unit G2 having positive optical power, a third lens unit G3 having positive optical power, and a fourth lens unit G4 having negative optical power.
The first lens unit G1, in order from the object side to the image side, includes: a negative meniscus first lens element L1 with the convex surface facing the object side; a negative meniscus second lens element L2 with the convex surface facing the object side; a negative meniscus third lens element L3 with the convex surface facing the object side; a bi-concave fourth lens element L4; and a positive meniscus fifth lens element L5 with the convex surface facing the object side. The fourth lens element L4 and the fifth lens element L5 are cemented with each other. Further, a surface of the second lens element L2 facing the object side is aspheric.
The second lens unit G2, in order from the object side to the image side, includes: a bi-convex sixth lens element L6; and a negative meniscus seventh lens element L7 with the convex surface facing the image side. The sixth lens element L6 and the seventh lens element L7 are cemented with each other. Further, a surface of the sixth lens element L6 facing the object side is aspheric.
The third lens unit G3, in order from the object side to the image side, includes: a negative meniscus eighth lens element L8 with the convex surface facing the object side; a bi-convex ninth lens element L9; and a positive meniscus tenth lens element L10 with the convex surface facing the object side. The eighth lens element L8 and the ninth lens element L9 are cemented with each other.
The fourth lens unit G4, in order from the object side to the image side, includes: a positive meniscus eleventh lens element L11 with the convex surface facing the image side; a negative meniscus twelfth lens element L12 with the convex surface facing the image side; a bi-concave thirteenth lens element L13; and a bi-convex fourteenth lens element L14. The twelfth lens element L12 and the thirteenth lens element L13 are cemented with each other. Further, a surface of the eleventh lens element L11 facing the object side is aspheric.
At the time of zooming, the respective lens units move along the optical axis such that: the interval between the first lens unit G1 and the second lens unit G2 at a telephoto limit is made shorter than the interval at a wide-angle limit; the interval between the second lens unit G2 and the third lens unit G3 at a telephoto limit is made longer than the interval at a wide-angle limit; and the interval between the third lens unit G3 and the fourth lens unit G4 at a telephoto limit is made longer than the interval at a wide-angle limit. More specifically, at the time of zooming from a wide-angle limit to a telephoto limit, the first lens unit G1 moves to the image side along the optical axis, whereas the second lens unit G2, the third lens unit G3, and the fourth lens unit G4 move to the object side along the optical axis. The aperture diaphragm A moves to the object side together with the third lens unit G3.
Further, at the time of focusing from an infinity in-focus condition to a close-point in-focus condition, the second lens unit G2 moves to the image side along the optical axis.
The following description is given for conditions to be satisfied by the zoom lens system according to each embodiment. Here, in the zoom lens system according to each embodiment, a plurality of conditions to be satisfied are set forth. Thus, a configuration of the zoom lens system that satisfies as many applicable conditions as possible is most preferable. However, when an individual condition is satisfied, a zoom lens system having a corresponding effect can be obtained.
In the zoom lens system according to Embodiments 1 to 5, 7, and 8, it is preferable that the following condition is satisfied.

−0.65<fW/f1<−0.45  (1)

where,
f1 is a focal length 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 ratio between the focal length of the entire system and the focal length of the first lens unit. When the value exceeds the upper limit of the condition (1), it becomes difficult to compensate the astigmatism or the distortion, which causes difficulty in achieving preferable optical performance in the periphery part of the image. Further, when the value goes below the lower limit of the condition (1), the entire length of the lenses increases, and in addition, the diameter of the first lens unit increases. Thus, it becomes difficult to achieve the size reduction.
In the zoom lens system according to Embodiments 1 to 5, 7, and 8, it is preferable that the following condition is satisfied.

0.1<fW/f2<0.3  (2)

where,
f2 is a focal length 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 ratio between the focal length of the entire system and the focal length of the second lens unit. When the value exceeds the upper limit of the condition (2), the entire length of the lenses increases, and it becomes difficult to achieve the size reduction. At the same time, it becomes difficult to preferably compensate a so-called coma aberration in a range from a middle position to a telephoto limit. Further, when the value goes below the lower limit of the condition (2), there is no effect of the field curvature compensation, which is obtained by imparting the refractive power to the second lens unit and to the subsequent third lens unit and changing the interval therebetween by zooming. Thus, it becomes difficult to achieve the preferable optical performance in the periphery part of the image.
In the zoom lens system according to Embodiments 1 to 5, 7, and 8, it is preferable that the following condition is satisfied.

0.25<fW/f3<0.5  (3)

where,
f3 is a focal length of the third lens unit, and
fW is a focal length of the entire system at a wide-angle limit.
The condition (3) sets forth the ratio between the focal length of the entire system and the focal length of the third lens unit. When the value exceeds the upper limit of the condition (3), it becomes difficult to compensate the spherical aberration or the coma aberration which relates to the optical performance on and around the optical axis, and in addition, the intervals between third lens unit and the lens units before and after the third lens unit become insufficient, which causes difficulty in configuring the zoom lens system. Further, when the value goes below the lower limit of the condition (3), the amount of movement of the third lens unit increases at the time of variation of magnification, and thus it becomes difficult to achieve the size reduction.
In the zoom lens system according to Embodiments 1 to 5, 7, and 8, it is preferable that the following condition is satisfied.

−0.1<fW/f4<−0.05  (4)

where,
f4 is a focal length of the fourth lens unit, and
fW is a focal length of the entire system at a wide-angle limit.
The condition (4) sets forth the ratio between the focal length of the entire system and the focal length of the fourth lens unit. When the value exceeds the upper limit of the condition (4), a change in the astigmatism or the like caused by the decentering error or the like of the fourth lens unit increases. In addition, since the positive optical power of the third lens unit on the object side relative to the fourth lens unit increase, a change in the coma aberration caused by the decentering error or the like of the third lens unit is apt to increase. Thus, the situation is not preferable since costs necessary for manufacturing increase. Further, when the value goes below the lower limit of the condition (4), the amount of movement of the fourth lens unit at the time of focusing increases, and thus it becomes difficult to achieve the size reduction.
In the zoom lens system according to Embodiments 1 to 5 and 7, it is preferable that the following condition is satisfied.

0.01<fW/f5<0.15  (5)

where,
f5 is a focal length of the fifth lens unit, and
fW is a focal length of the entire system at a wide-angle limit.
The condition (5) sets forth the ratio between the focal length of the entire system and the focal length of the fifth lens unit. When the value exceeds the upper limit of the condition (5), the zoom lens system is approximate to the true telecentric condition. Thus, the diameter of the fifth lens unit increases, and as a result it becomes difficult to achieve the size reduction. Further, when the value goes below the lower limit of the condition (5), the zoom lens system is deviated from the telecentric condition, and in particular, the incident angle of light to be incident on the periphery part of the image sensor increases, and thus this situation is unpreferable in terms of characteristics of the image sensor.
In the zoom lens system according to the respective embodiments, it is preferable that the following condition is satisfied.

DISW<−8  (6)

where,
DISW is distortion (%) at the maximum image height at a wide-angle limit.
The distortion DISW can be obtained from the following formula.

DISW=(Y′−Y)/Y×100(unit: %)

(where, Y′ is a real image height, and Y is an ideal image height).
When the value exceeds the upper limit of the condition (6), the distortion is compensated excessively, and it becomes difficult to compensate the coma aberration or the astigmatism. Thus, it becomes difficult to achieve the size reduction.
In the zoom lens system according to the respective embodiments, it is preferable that the following condition is satisfied.

2.3<(R11+R12)/(R11−R12)<10  (7)

where,
R11 is an object side curvature radius of the lens element closest to the object side in the first lens unit, and
R12 is an image side curvature radius of the lens element closest to the object side in the first lens unit.
The condition (7) sets forth the shape of the lens element closest to the object side in the first lens unit. When the value exceeds the upper limit of the condition (7), the diameter of the lens element increases, and it becomes difficult to process the lens element. Thus, it becomes difficult to achieve the size reduction, and at the same time, the manufacturing costs increase. Further, when the value goes below the lower limit of the condition (7), a large negative distortion is generated, and thus this leads to insufficient compensation of the distortion.
In the zoom lens system according to the respective embodiments, it is preferable that the following condition is satisfied.

2.3<(R21+R22)/(R21−R22)<10  (8)

where,
R21 is an object side curvature radius of the second lens element from the object side in the first lens unit, and
R22 is an image side curvature radius of the second lens element from the object side in the first lens unit.
The condition (8) sets forth the shape of the second lens element from the object side in the first lens unit. When the value exceeds the upper limit of the condition (8), the diameter of the lens element increases, and it becomes difficult to process the lens element. Thus, it becomes difficult to achieve the size reduction, and at the same time, the manufacturing costs increase. Further, when the value goes below the lower limit of the condition (8), a large negative distortion is generated, and thus this leads to insufficient compensation of the distortion.
In the zoom lens system according to the respective embodiment, it is preferable that the following condition is satisfied.

2.3<(R31+R32)/(R31−R32)<10  (9)

where,
R31 is an object side curvature radius of the third lens element from the object side in the first lens unit, and
R32 is an image side curvature radius of the third lens element from the object side in the first lens unit.
The condition (9) sets forth the shape of the third lens element from the object side in the first lens unit. When the value exceeds the upper limit of the condition (9), the diameter of the lens element increases, and it becomes difficult to process the lens element. Thus, it becomes difficult to achieve the size reduction, and at the same time, the manufacturing costs increases. Further, when the value goes below the lower limit of the condition (9), a large negative distortion is generated, and thus this leads to insufficient compensation of the distortion.
In the zoom lens system according to the respective embodiments, it is preferable that the following condition is satisfied.

1.4<DL/YM<2.5  (10)

(where, 100<2ωW<140)
where,
DL is an effective diameter of the lens surface closest to the image side,
YM is the maximum image height at a wide-angle limit, and
ωW is a half view angle (°) at a wide-angle limit.
The condition (10) sets forth the ratio between the effective diameter of the lens surface closest to the image side and the maximum image height. When the value exceeds the upper limit of the condition (10), the diameter of the lens closest to the image side increases, and it becomes difficult to achieve the size reduction. Further, when the value goes below the lower limit of the condition (10), the back focus needs to be elongated in order to avoid an increase in the incident angle of light. Thus, it becomes difficult to achieve the size reduction.
In the zoom lens system according to the respective embodiments, it is preferable that the following condition is satisfied.

1.2<BFW/YM<1.6.  (11)

where,
BFW is the back focus at a wide-angle limit,
YM is the maximum image height at a wide-angle limit, and
ωW is a half view angle (°) at a wide-angle limit.
The condition (11) sets forth the ratio between the back focus at a wide-angle limit and the maximum image height. When the value exceeds the upper limit of the condition (11), the zoom lens system exhibits a significant retrofocus characteristic, which causes difficulty in compensating the distortion. Thus, it becomes difficult to achieve the size reduction. Further, when the value goes below the lower limit of the condition (11), the shadow of foreign particles (dust) adhering to the surface of the lens closest to the image side becomes significant on the taken image. Thus, handling of the interchangeable lens apparatus becomes complicated. For example, adherence of foreign particles needs to be carefully checked at the time of changing the lens system.
In the zoom lens system according to Embodiment 6, it is preferable that the following condition is satisfied.

−0.65<fW/f120<−0.45  (12)

where,
f12W is a composite focal length of the first lens unit and the second lens unit at a wide-angle limit, and
fW is a focal length of the entire system at a wide-angle limit.
The condition (12) sets forth the ratio between the focal length of the entire system, and the composite focal length of the first lens unit and the second lens unit. When the value exceeds the upper limit of the condition (12), it becomes difficult to compensate the astigmatism or the distortion, which causes difficulty in achieving preferable optical performance in the periphery part of the image. Further, when the value goes below the lower limit of the condition (12), the entire length of the lenses increases, and at the same time, the diameter of the first lens unit or the second lens unit increases. Thus it becomes difficult to achieve the size reduction.
In the zoom lens system according to Embodiment 6, it is preferable that the following condition is satisfied.

0.1<fW/f3<0.3  (13)

where,
f3 is a focal length of the third lens unit, and
fW is a focal length of the entire system at a wide-angle limit.
The condition (13) sets forth the ratio between the focal length of the entire system and the focal length of the third lens unit. When the value exceeds the upper limit of the condition (13), the entire length of the lenses increases, and thus it becomes difficult to achieve the size reduction. At the same time, it becomes difficult to preferably compensate a so-called coma aberration in a range from a middle position to a telephoto limit. Further, when the value goes below the lower limit of the condition (13), there is no effect of the field curvature compensation, which is obtained by imparting the refractive power to the third lens unit and to the subsequent fourth lens unit and changing the intervals by zooming. Thus, it becomes difficult to achieve the preferable optical performance in the periphery part of the image.
In the zoom lens system according to Embodiment 6, it is preferable that the following condition is satisfied.

0.25<fW/f4<0.5  (14)

where,
f4 is a focal length of the fourth lens unit, and
fW is a focal length of the entire system at a wide-angle limit.
The condition (14) sets forth the ratio of the focal length of the entire system and the focal length of the fourth lens unit. When the value exceeds the upper limit of the condition (14), it becomes difficult to compensate the spherical aberration or the coma aberration which relates to the optical performance on and around the optical axis, and in addition, the intervals between fourth lens unit and the lens units before and after the fourth lens unit becomes insufficient, which causes difficulty in configuring the zoom lens system. Further, when the value goes below the lower limit of the condition (14), the amount of movement of the fourth lens unit increases at the time of variation of magnification, and thus it becomes difficult to achieve the size reduction.
In the zoom lens system according to Embodiment 6, it is preferable that the following condition is satisfied.

−0.1<fW/f5<−0.05  (15)

where,
f5 is a focal length of the fifth lens unit, and
fW is a focal length of the entire system at a wide-angle limit.
The condition (15) sets forth the ratio between the focal length of the entire system and the focal length of the fifth lens unit. When the value exceeds the upper limit of the condition (15), a change in the astigmatism or the like caused by the decentering errors or the like of the fifth lens unit increases. In addition, since the positive optical power of the fourth lens unit on the object side relative to the fifth lens unit increases, a change in the coma aberration caused by the decentering error or the like of the fourth lens unit is apt to increase. Thus, the situation is not preferable since costs necessary for manufacturing increase. Further, when the value goes below the lower limit of the condition (15), the amount of movement of the fifth lens unit at the time of focusing increases, and thus it becomes difficult to achieve the size reduction.
In the zoom lens system according to Embodiment 6, it is preferable that the following condition is satisfied.

0.01<fW/f6<0.15  (16)

where,
f6 is a focal length of the sixth lens unit, and
fW is a focal length of the entire system at a wide-angle limit.
The condition (16) sets forth the ratio between the focal length of the entire system and the focal length of the sixth lens unit. When the value exceeds the upper limit of the condition (16), the zoom lens system is approximate to the true telecentric condition. Thus, the diameter of the sixth lens unit increases, and as a result it becomes difficult to achieve the size reduction. Further, when the value goes below the lower limit of the condition (16), the zoom lens system is deviated from the telecentric condition, and in particular, the incident angle of light to be incident on the periphery part of the image sensor increases, and thus this situation is unpreferable in terms of characteristics of the image sensor.
Here, the lens units constituting the zoom lens system of the respective embodiments may be composed exclusively of refractive type lens elements that deflect the incident light by refraction (that is, lenses of a type in which deflection is achieved at the interface between media each having a distinct refractive index). Alternatively, the lens units may employ any one of or a combination of some of: diffractive type lens elements that deflect the incident light by diffraction; refractive-diffractive hybrid type lens elements or the like that deflect the incident light by a combination of diffraction and refraction; and gradient index type lens elements that deflect the incident light by distribution of refractive index in the medium.
(Embodiment 9)
FIG. 17 is a schematic construction diagram of an interchangeable-lens type digital camera system according to Embodiment 9.
A interchangeable-lens type digital camera system 100 (hereinafter, simply referred to as “camera system”) according to the present embodiment includes a camera body 101, and an interchangeable lens apparatus 201 connected to the camera body 101 in an attachable and removable manner.
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 thereby to convert the optical image into an electric image signal, a liquid crystal display monitor 103 which displays an image signal converted by the image sensor 102, and a camera mount section 104. On the other hand, the interchangeable lens apparatus 201 includes the zoom lens system 202 according to any one of Embodiments 1 to 8, a lens barrel which holds the zoom lens system 202, and a lens mount section 204 connected to the camera mount section 104 of the camera body. The camera mount section 104 and the lens mount section 204 are connected to each other not only physically but also electrically, and function as interfaces. That is, a controller (not shown) inside the camera body 101 is electrically connected to a controller (not shown) inside the interchangeable lens apparatus 201, thereby achieving mutual signal communication.
The camera system 100 according to the present embodiment includes the zoom lens system 202 according to any one of Embodiments 1 to 8, and hence is capable of displaying an preferable optical image at the time of focusing in a live view state.
EXAMPLES
Hereinafter, numerical examples will be described below in which the zoom lens systems according to Embodiments 1 to 8 are implemented specifically. As will be described later, Numerical Examples 1 to 8 corresponds to Embodiments 1 to 8, respectively. Here, in each numerical example, the units of the length are all “mm”, while the units of the 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 aspheric surfaces, and the aspheric surface configuration is defined by the following formula.




  Z
  =
  
    
      
        
          h
          2
        
        /
        r
      
      
        1
        +
        
          
            1
            -
            
              
                (
                
                  1
                  +
                  κ
                
                )
              
              ⁢
              
                
                  (
                  
                    h
                    /
                    r
                  
                  )
                
                2
              
            
          
        
      
    
    +
    
      ∑
      
        
          A
          n
        
        ⁢
        
          h
          n
        
      
    
  




Here, the symbols in the formula indicate the following quantities:

    Z is the distance from an on-the-aspheric-surface point at a height h relative to the optical axis to a tangential plane at the top of the aspheric surface;
    h is the height relative to the optical axis;
    r is the radius of curvature at the top;
    κ is the conic constant; and
    An is the n-th order aspheric coefficient.


FIGS. 2, 4, 6, 8, 10, 12, 14, and 16 are longitudinal aberration diagrams of an infinity in-focus condition of the zoom lens systems according to Numerical Examples 1, 2, 3, 4, 5, 6, 7, and 8.
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 diagram, indicated as F), 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 diagram, indicated as H), the solid line and the dash line indicate the characteristics to the sagittal image plane (in each diagram, indicated as “s”) and the meridional image plane (in each diagram, indicated as “m”), respectively.
Numerical Example 1
The zoom lens system of Numerical Example 1 corresponds to Embodiment 1 shown in FIG. 1. Data of the zoom lens system according to Numerical Example 1, i.e., the surface data, the aspherical data, the various data, the lens element data, the zoom lens unit data, and the zoom lens unit magnification are shown in Table 1, Table 2, Table 3, Table 4, Table 5, and Table 6, respectively.







TABLE 1







(Surface data)











Surface number
r
d
nd
vd














Object surface
∞





 1
32.61610
2.00000
1.80420
46.5


 2
20.03180
6.25890


 3
28.62190
1.80000
1.80420
46.5


 4
16.57000
2.64120


 5
20.52130
1.70000
1.80800
40.9


 6*
11.47060
7.78130


 7
−302.25460
1.05000
1.49700
81.6


 8
17.88820
0.26000


 9
18.09470
4.00840
1.80610
33.3


10
60.79620
Variable


11
19.24800
0.70000
1.74330
49.2


12
6.77140
2.24910
1.67270
32.2


13
170.51120
1.89140


14
∞
Variable


(Diaphragm)


15
3979.65950
0.70000
1.84666
23.8


16
13.78260
2.33950
1.51680
64.2


17
−21.54820
1.31900


18
−9.53570
0.80000
1.51680
64.2


19
21.19960
2.89150
1.49700
81.6


20
−15.02470
0.20000


21
−58.86510
1.97180
1.49700
81.6


22
−20.72310
0.20000


23
41.66740
3.23430
1.49700
81.6


24
−20.80500
Variable


25
26.65630
0.80000
1.51823
59.0


26
17.53640
Variable


27
84.08090
0.90000
1.80518
25.5


28
27.44430
3.57720
1.52300
70.1


 29*
−39.99340
BF


Image surface
∞
















TABLE 2







(Aspherical data)








Surface



No.
Parameters











6
K = −4.01413E−01, A4 = −2.82803E−05, A6 = −1.13654E−07,



A8 = −7.54243E−10, A10 = 5.36525E−12,



A12 = −3.87978E−14


29
K = 0.00000E+00, A4 = 5.16711E−05, A6 = 2.64198E−07,



A8 = −6.34113E−09, A10 = 9.00687E−11,



A12 = −4.31222E−13
















TABLE 3







(Various data)


Zooming ratio 1.89190











Wide
Middle
Telephoto
















Focal length
7.2006
9.9053
13.6229



F-number
4.00268
3.85380
4.09472



View angle
59.0156
48.7020
38.1410



Image height
10.8150
10.8150
10.8150



Overall length of lens
95.5429
90.8643
89.7896



system



BF
15.38321
15.38860
15.39895



d10
19.2075
9.1749
1.9157



d14
1.9913
2.0522
1.2990



d24
2.5261
2.0100
1.8500



d26
5.1612
10.9650
18.0524



Entrance pupil position
19.8078
18.7380
17.5657



Exit pupil position
−50.9354
−68.0300
−85.0516



Front principal point
26.2266
27.4671
29.3411



position



Back principal point
88.3423
80.9590
76.1668



position

















TABLE 4







(Lens element data)









Unit
Initial surface No.
Focal length












1
1
−69.4814


2
3
−52.4229


3
5
−35.1378


4
7
−33.9445


5
9
30.6741


6
11
−14.3986


7
12
10.4247


8
15
−16.3366


9
16
16.6409


10
18
−12.6150


11
19
18.1737


12
21
63.2652


13
23
28.4087


14
25
−101.9601


15
27
−50.9622


16
28
31.6971
















TABLE 5







(Zoom lens unit data)
















Front




Initial

Length of
principal



surface

lens
point
Back principal


Unit
No.
Focal length
unit
position
point position















1
1
−14.89596
27.49980
9.27046
14.76759


2
11
40.61921
4.84050
−0.45077
0.77074


3
15
22.48920
13.65610
11.20519
17.60033


4
25
−101.96007
0.80000
1.58769
1.84449


5
27
80.78660
4.47720
2.60670
4.21608
















TABLE 6







(Zoom lens unit magnification)












Initial






surface



Unit
No.
Wide
Middle
Telephoto














1
1
0.00000
0.00000
0.00000


2
11
−7.04498
9.51959
3.52410


3
15
0.06774
−0.06597
−0.23278


4
25
1.25623
1.31323
1.38290


5
27
0.80635
0.80628
0.80616









Numerical Example 2
The zoom lens system of Numerical Example 2 corresponds to Embodiment 2 shown in FIG. 3. Data of the zoom lens system according to Numerical Example 2, i.e., the surface data, the aspherical data, the various data, the lens element data, the zoom lens unit data, and the zoom lens unit magnification are shown in Table 7, Table 8, Table 9, Table 10, Table 11, and Table 12, respectively.







TABLE 7







(Surface data)











Surface number
r
d
nd
vd





Object surface
∞





 1
32.47020
2.00000
1.80420
46.5


 2
20.03180
6.27370


 3
28.59860
1.80000
1.80420
46.5


 4
16.57000
2.70090


 5
20.52130
1.70000
1.80800
40.9


 6*
11.44550
8.07250


 7
−100.75020
1.00000
1.49700
81.6


 8
19.58010
4.00410
1.80610
33.3


 9
92.88670
Variable


10
18.85950
0.70000
1.74330
49.2


11
6.74340
2.25040
1.67270
32.2


12
116.25340
1.89560


13
∞
Variable


(Diaphragm)


14
595.95060
0.70000
1.84666
23.8


15
13.82680
2.34620
1.51680
64.2


16
−21.12650
1.32080


17
−9.70390
0.80000
1.51680
64.2


18
20.99080
2.87260
1.49700
81.6


19
−15.71880
0.20000


20
−58.64710
1.97850
1.49700
81.6


21
−20.62270
0.20000


22
41.46940
3.23800
1.49700
81.6


23
−20.82360
Variable


24
26.64750
0.80000
1.51823
59.0


25
17.53290
Variable


26
81.82020
0.90000
1.80518
25.5


27
27.27070
3.58130
1.52300
70.1


 28*
−40.37930
BF


Image surface
∞
















TABLE 8







(Aspherical data)








Surface



No.
Parameters











6
K = −3.93507E−01, A4 = −2.91092E−05, A6 = −9.83771E−08,



A8 = −1.09494E−09, A10 = 7.89710E−12,



A12 = −4.73408E−14


28
K = 0.00000E+00, A4 = 5.27176E−05, A6 = 2.51049E−07,



A8 = −5.97520E−09, A10 = 8.53715E−11,



A12 = −4.07934E−13
















TABLE 9







(Various data)


Zooming ratio 1.88982











Wide
Middle
Telephoto
















Focal length
7.2052
9.9040
13.6166



F-number
4.00224
3.85285
4.09430



View angle
59.1763
48.7875
38.1653



Image height
10.8150
10.8150
10.8150



Overall length of lens
95.5329
90.8882
89.8292



system



BF
15.38680
15.39045
15.40348



d9
19.1344
9.1208
1.8888



d13
1.9956
2.0689
1.2998



d23
2.5108
2.0100
1.8500



d25
5.1707
10.9634
18.0525



Entrance pupil position
19.8352
18.7716
17.6109



Exit pupil position
−50.5737
−67.7646
−84.7428



Front principal point
26.2533
27.4959
29.3761



position



Back principal point
88.3277
80.9842
76.2125



position

















TABLE 10







(Lens element data)









Unit
Initial surface No.
Focal length












1
1
−70.0446


2
3
−52.4889


3
5
−34.9551


4
7
−32.8954


5
8
30.0453


6
10
−14.4782


7
11
10.5544


8
14
−16.7280


9
15
16.5496


10
17
−12.7277


11
18
18.5672


12
20
62.9126


13
22
28.3825


14
24
−101.9672


15
26
−51.1776


16
27
31.6996
















TABLE 11







(Zoom lens unit data)
















Front




Initial

Length of
principal



surface

lens
point
Back principal


Unit
No.
Focal length
unit
position
point position















1
1
−14.90085
27.55120
9.28790
14.66851


2
10
42.30042
4.84600
−0.60680
0.62440


3
14
22.37367
13.65610
11.04562
17.23657


4
24
−101.96715
0.80000
1.58811
1.84491


5
26
80.34236
4.48130
2.56393
4.17322
















TABLE 12







(Zoom lens unit magnification)












Initial






surface


Unit
No.
Wide
Middle
Telephoto














1
1
0.00000
0.00000
0.00000


2
10
−10.54686
7.04668
3.19613


3
14
0.04533
−0.08923
−0.25690


4
24
1.25690
1.31376
1.38348


5
26
0.80465
0.80460
0.80444









Numerical Example 3
The zoom lens system of Numerical Example 3 corresponds to Embodiment 3 shown in FIG. 5. Data of the zoom lens system according to Numerical Example 3, i.e., the surface data, the aspherical data, the various data, the lens element data, the zoom lens unit data, and the zoom lens unit magnification are shown in Table 13 Table 14, Table 15, Table 16, Table 17, and Table 18, respectively.







TABLE 13







(Surface data)











Surface number
r
d
nd
vd





Object surface
∞





 1
30.44780
2.00000
1.80420
46.5


 2
18.87500
7.34890


 3
27.75750
1.92780
1.80420
46.5


 4
16.42880
3.26840


 5
19.60000
1.55000
1.80470
41.0


 6*
10.89970
7.72330


 7
−225.11440
1.89310
1.49700
81.6


 8
16.32060
3.99170
1.80610
33.3


 9
57.99910
Variable


10
18.84770
0.70000
1.72342
38.0


11
6.23040
2.36850
1.68400
31.3


12
115.54490
1.70700


13
∞
Variable


(Diaphragm)


14
∞
0.70000
1.84666
23.8


15
13.71240
4.78040
1.51823
59.0


16
−15.01690
1.13690


17
−8.82940
0.80000
1.51680
64.2


18
104.27750
3.14800
1.49700
81.6


19
−12.21860
0.20000


20
33.45760
3.28830
1.49700
81.6


21
−21.12350
Variable


22
30.94380
1.00000
1.58144
40.9


23
19.52960
Variable


24
−73.91420
1.00000
1.80518
25.5


25
123.34430
3.41370
1.52500
70.3


 26*
−19.50200
BF


Image surface
∞
















TABLE 14







(Aspherical data)








Surface



No.
Parameters











6
K = −5.49068E−01, A4 = −1.42254E−05, A6 = −1.04715E−07,



A8 = −1.46986E−10, A10 = 3.11013E−12,



A12 = −2.87242E−14


26
K = 0.00000E+00, A4 = 8.23200E−05, A6 = −7.52604E−08,



A8 = 6.50947E−09, A10 = −9.16057E−11, A12 = 4.80195E−13
















TABLE 15







(Various data)


Zooming ratio 1.88906











Wide
Middle
Telephoto
















Focal length
7.2009
9.9186
13.6030



F-number
4.03569
3.88161
4.13870



View angle
58.9271
47.9004
37.3032



Image height
10.8150
10.8150
10.8150



Overall length of lens
96.5585
92.8958
92.3358



system



BF
15.38273
15.38116
15.38602



d9
18.0260
8.4931
1.4460



d13
1.7982
2.1728
1.6710



d21
2.4078
1.7000
1.7108



d23
4.9978
11.2027
18.1760



Entrance pupil position
20.4341
19.4466
18.3521



Exit pupil position
−58.3885
−89.5091
−126.2034



Front principal point
26.9321
28.4273
30.6482



position



Back principal point
89.3576
82.9771
78.7328



position

















TABLE 16







(Lens element data)









Unit
Initial surface No.
Focal length












1
1
−66.9043


2
3
−54.1627


3
5
−33.1474


4
7
−30.5391


5
8
27.0196


6
10
−13.1720


7
11
9.5439


8
14
−16.1958


9
15
14.6636


10
17
−15.7133


11
18
22.2055


12
20
26.5851


13
22
−94.0884


14
24
−57.2713


15
25
32.3410
















TABLE 17







(Zoom lens unit data)
















Front




Initial

Length
principal



surface

of lens
point
Back principal


Unit
No.
Focal length
unit
position
point position















1
1
−14.40374
29.70320
10.19859
16.32686


2
10
37.60170
4.77550
−0.50091
0.78179


3
14
22.69792
14.05360
11.13540
17.51424


4
22
−94.08838
1.00000
1.77131
2.11793


5
24
68.03402
4.41370
5.03396
6.83127
















TABLE 18







(Zoom lens unit magnification)












Initial surface





Unit
No.
Wide
Middle
Telephoto














1
1
0.00000
0.00000
0.00000


2
10
−4.88114
20.55381
4.23608


3
14
0.10003
−0.03110
−0.19604


4
22
1.26498
1.33090
1.40509


5
24
0.80943
0.80945
0.80938









Numerical Example 4
The zoom lens system of Numerical Example 4 corresponds to Embodiment 4 shown in FIG. 7. Data of the zoom lens system according to Numerical Example 4, i.e., the surface data, the aspherical data, the various data, the lens element data, the zoom lens unit data, and the zoom lens unit magnification are shown in Table 19, Table 20, Table 21, Table 22, Table 23, and Table 24, respectively.







TABLE 19







(Surface data)











Surface number
r
d
nd
vd





Object surface
∞





 1
33.73000
2.00000
1.80420
46.5


 2
20.50000
5.85990


 3
26.77380
1.80000
1.80420
46.5


 4
16.10000
4.64310


 5
19.60000
1.55000
1.80470
41.0


 6*
10.69470
8.26910


 7
−298.88690
1.26450
1.49700
81.6


 8
16.57410
5.66770
1.80610
33.3


 9
58.84120
Variable


10
19.49320
0.70000
1.72342
38.0


11
7.80550
4.16820
1.68400
31.3


12*
65.51100
1.50600


13 (Diaphragm)
∞
Variable


14
268.54290
0.70000
1.84666
23.8


15
18.67540
2.51990
1.51823
59.0


16
−12.40510
0.78790


17
−9.47110
0.80000
1.51680
64.2


18
12.00420
3.75020
1.49700
81.6


19
−17.26890
0.20000


20
38.76770
2.94440
1.49700
81.6


21
−18.34760
Variable


22
33.88100
1.00000
1.58144
40.9


23
19.79670
Variable


24
−205.25430
1.00000
1.80518
25.5


25
58.31210
3.35500
1.52500
70.3


26*
−23.17480
BF


Image surface
∞
















TABLE 20







(Aspherical data)








Sur-



face


No.
Parameters











6
K = −4.41439E−01, A4 = −3.54100E−05, A6 = 1.15587E−07,



A8 = −3.74110E−09, A10 = 2.31717E−11, A12 = −9.50173E−14


12
K = 0.00000E+00, A4 = 4.91209E−05, A6 = −2.40723E−06, A8 =



1.65752E−07, A10 = −4.61598E−09, A12 = 0.00000E+00


26
K = 0.00000E+00, A4 = 7.10598E−05, A6 = 6.08469E−08,



A8 = −1.63689E−09, A10 = 4.66337E−11, A12 = −2.92076E−13
















TABLE 21







(Various data)


Zooming ratio 1.88910











Wide
Middle
Telephoto
















Focal length
7.2001
9.8960
13.6017



F-number
4.05005
4.05027
4.05142



View angle
58.9987
48.4820
37.6168



Image height
10.8150
10.8150
10.8150



Overall length of lens
96.4352
91.3849
91.2929



system



BF
15.37255
15.84598
15.85089



d9
17.9459
8.0821
1.5843



d13
2.1001
1.9877
1.1500



d21
1.7000
2.0393
1.7000



d23
4.8308
8.9439
16.5218



Entrance pupil position
20.1706
19.2415
18.3453



Exit pupil position
−39.9985
−51.4394
−71.3834



Front principal point
26.4345
27.6821
29.8262



position



Back principal point
89.2352
81.4889
77.6912



position

















TABLE 22







(Lens element data)









Unit
Initial surface No.
Focal length












1
1
−69.6856


2
3
−54.2988


3
5
−31.7123


4
7
−31.5544


5
8
27.0070


6
10
−18.4597


7
11
12.5859


8
14
−23.7367


9
15
14.7927


10
17
−10.1157


11
18
14.8816


12
20
25.4941


13
22
−84.1001


14
24
−56.3032


15
25
32.0423
















TABLE 23







(Zoom lens unit data)
















Front




Initial

Length of
principal



surface

lens
point
Back principal


Unit
No.
Focal length
unit
position
point position















1
1
−14.24164
31.05430
9.85997
16.74252


2
10
44.08317
6.37420
−1.41896
0.69708


3
14
21.93528
11.70240
8.51387
12.79729


4
22
−84.10010
1.00000
1.56191
1.91263


5
24
69.44057
4.35500
4.15667
5.84080
















TABLE 24







(Zoom lens unit magnification)












Initial surface





Unit
No.
Wide
Middle
Telephoto














1
1
0.00000
0.00000
0.00000


2
10
−44.20775
4.97181
2.86917


3
14
0.01098
−0.12954
−0.28937


4
22
1.30241
1.36019
1.45039


5
24
0.80002
0.79320
0.79313









Numerical Example 5
The zoom lens system of Numerical Example 5 corresponds to Embodiment 5 shown in FIG. 9. Data of the zoom lens system according to Numerical Example 5, i.e., the surface data, the aspherical data, the various data, the lens element data, the zoom lens unit data, and the zoom lens unit magnification are shown in Table 25, Table 26, Table 27, Table 28, Table 29, and Table 30, respectively.







TABLE 25







(Surface data)











Surface number
r
d
nd
vd





Object surface
∞





 1
32.53230
2.00000
1.80420
46.5


 2
20.50000
5.29920


 3
24.93130
1.80000
1.80420
46.5


 4
16.00000
6.77330


 5
30.03360
1.93360
1.80470
41.0


 6*
14.19960
6.83460


 7
−81.80750
1.29550
1.49700
81.6


 8
29.31440
4.06670
1.80610
33.3


 9
213.26320
Variable


10
19.05720
0.70000
1.72623
54.8


11
6.93710
3.42900
1.63182
34.7


12*
696.48680
1.35570


13 (Diaphragm)
∞
Variable


14
−631.44520
0.70000
1.84666
23.8


15
17.41730
2.50600
1.53594
50.3


16
−12.21090
1.02130


17
−7.38790
0.80000
1.51742
52.1


18
24.34430
4.39930
1.49700
81.6


19
−10.50450
0.20000


20
55.10800
3.00710
1.49700
81.6


21
−19.57410
Variable


22
40.60470
1.00000
1.58144
40.9


23
23.96040
Variable


24
233.55820
1.00000
1.80518
25.5


25
34.11090
0.77000


26
79.43180
2.32080
1.52500
70.3


27*
−28.67840
BF


Image surface
∞
















TABLE 26







(Aspherical data)








Sur-



face


No.
Parameters











6
K = 0.00000E+00, A4 = −4.43286E−05, A6 = −1.05536E−07,



A8 = −2.37863E−09, A10 = 1.94014E−11, A12 = −8.16832E−14


12
K = 0.00000E+00, A4 = −3.18703E−07, A6 = −1.05633E−06,



A8 = −1.75650E−08, A10 = 0.00000E+00, A12 = 0.00000E+00


27
K = 0.00000E+00, A4 = 6.73656E−05, A6 = 4.76084E−07,



A8 = −6.30642E−09, A10 = 5.53166E−11, A12 = 0.00000E+00
















TABLE 27







(Various data)


Zooming ratio 1.88916











Wide
Middle
Telephoto
















Focal length
7.2007
9.8948
13.6032



F-number
4.05157
4.05172
4.05114



View angle
59.0196
48.8263
38.1892



Image height
10.8150
10.8150
10.8150



Overall length of lens
98.5596
90.7884
87.2555



system



BF
15.36996
15.68211
15.43608



d9
20.5242
9.1837
1.4783



d13
3.0469
2.6786
1.4085



d21
1.9738
2.0576
1.7000



d23
4.4326
7.9743
14.0205



Entrance pupil position
21.2510
20.1148
18.9129



Exit pupil position
−42.7313
−46.3055
−48.8643



Front principal point
27.5593
28.4301
29.6382



position



Back principal point
91.3589
80.8936
73.6523



position

















TABLE 28







(Lens element data)









Unit
Initial surface No.
Focal length












1
1
−74.4367


2
3
−61.0190


3
5
−35.3977


4
7
−43.2556


5
8
41.7491


6
10
−15.3935


7
11
11.0686


8
14
−20.0096


9
15
13.8012


10
17
−10.8607


11
18
15.4108


12
20
29.4558


13
22
−102.8018


14
24
−49.7209


15
26
40.4334
















TABLE 29







(Zoom lens unit data)
















Front




Initial

Length of
principal



surface

lens
point
Back principal


Unit
No.
Focal length
unit
position
point position















1
1
−14.95255
30.00290
10.49730
16.54644


2
10
41.90590
5.48470
−0.32700
1.30559


3
14
20.56078
12.63370
9.79278
15.07317


4
22
−102.80183
1.00000
1.57746
1.93084


5
24
181.29625
4.09080
8.72778
10.25289
















TABLE 30







(Zoom lens unit magnification)












Initial surface





Unit
No.
Wide
Middle
Telephoto














1
1
0.00000
0.00000
0.00000


2
10
−6.25432
9.03108
3.39440


3
14
0.06686
−0.06181
−0.21607


4
22
1.21332
1.25115
1.30730


5
24
0.94921
0.94749
0.94885









Numerical Example 6
The zoom lens system of Numerical Example 6 corresponds to Embodiment 6 shown in FIG. 11. Data of the zoom lens system according to Numerical Example 6, i.e., the surface data, the aspherical data, the various data, the lens element data, the zoom lens unit data, and the zoom lens unit magnification are shown in Table 31, Table 32, Table 33, Table 34, Table 35, and Table 36, respectively.







TABLE 31







(Surface data)











Surface number
r
d
nd
vd





Object surface
∞





 1
30.06520
2.00000
1.80420
46.5


 2
20.09930
6.13650


 3
25.33300
2.00000
1.80470
41.0


 4
15.86230
6.74200


 5
30.92990
1.20000
1.80420
46.5


 6*
14.21090
Variable


 7
129.66230
1.20000
1.56160
63.9


 8
17.52570
1.01240


 9
18.36670
3.34490
1.83985
24.9


10
38.38830
Variable


11*
33.50550
3.38690
1.66992
31.2


12
−7.43660
0.70000
1.75455
31.9


13
−47.16130
3.29690


14 (Diaphragm)
∞
Variable


15
209.92400
0.70000
1.84666
23.8


16
18.02210
2.70470
1.54169
48.2


17
−14.57450
1.18210


18
−8.49460
0.80000
1.52388
60.3


19
45.91050
3.53210
1.49700
81.6


20
−11.59690
0.20000


21
40.13460
2.75620
1.49700
81.6


22
−23.30420
Variable


23
28.17530
0.80000
1.80420
46.5


24
20.41840
Variable


25
133.58870
1.28810
1.49700
81.6


26
−326.46430
1.00000
1.70860
30.1


27
26.64730
0.74550


28
48.46360
2.82990
1.52500
70.3


29*
−26.39340
BF


Image surface
∞
















TABLE 32







(Aspherical data)








Sur-



face


No.
Parameters











6
K = 0.00000E+00, A4 = −4.18853E−05, A6 = −7.54669E−08,



A8 = −2.74114E−09, A10 = 1.97572E−11, A12 = −7.82285E−14


11
K = 0.00000E+00, A4 = 1.15782E−05, A6 = 1.00411E−06, A8 =



2.90105E−09, A10 = 0.00000E+00, A12 = 0.00000E+00


29
K = 0.00000E+00, A4 = 5.10029E−05, A6 = 4.63941E−07,



A8 = −5.18498E−09, A10 = 4.22156E−11, A12 = 0.00000E+00
















TABLE 33







(Various data)


Zooming ratio 1.88911











Wide
Middle
Telephoto
















Focal length
7.2003
9.8961
13.6021



F-number
4.05093
4.05037
4.05080



View angle
59.0300
48.9134
38.0753



Image height
10.8150
10.8150
10.8150



Overall length of lens
98.5551
92.6356
90.7195



system



BF
15.37564
15.37648
15.37629



d6
5.9699
5.7466
5.9541



d10
19.3861
9.6612
2.5120



d14
3.1202
2.4786
1.3500



d22
1.6210
1.5000
1.5000



d24
3.5241
8.3145
14.4689



Entrance pupil position
21.8963
21.0204
20.1109



Exit pupil position
−39.8493
−45.4177
−52.1867



Front principal point
28.1577
29.3056
30.9745



position



Back principal point
91.3549
82.7394
77.1174



position

















TABLE 34







(Lens element data)









Unit
Initial surface No.
Focal length












1
1
−82.8060


2
3
−58.2085


3
5
−33.7713


4
7
−36.2237


5
9
38.9594


6
11
9.3963


7
12
−11.7901


8
15
−23.3241


9
16
15.3223


10
18
−13.6143


11
19
19.0162


12
21
30.0991


13
23
−96.6666


14
25
190.9182


15
26
−34.7268


16
28
32.9765
















TABLE 35







(Zoom lens unit data)
















Front




Initial

Length of
principal



surface

lens
point
Back principal


Unit
No.
Focal length
unit
position
point position















1
1
−14.65895
18.07850
11.34033
14.74765


2
7
−415.88336
5.55730
7.91331
9.87009


3
11
41.03613
7.38380
0.65248
2.27420


4
15
21.58856
11.87510
8.73033
12.96911


5
23
−96.66660
0.80000
1.68820
2.02342


6
25
122.24738
5.86350
8.15157
10.20019
















TABLE 36







(Zoom lens unit magnification)












Initial surface





Unit
No.
Wide
Middle
Telephoto














1
1
0.00000
0.00000
0.00000


2
7
0.92882
0.92928
0.92885


3
11
−9.55702
7.29685
3.25841


4
15
0.04931
−0.08529
−0.25022


5
23
1.23366
1.28322
1.34689


6
25
0.90970
0.90969
0.90969









Numerical Example 7
The zoom lens system of Numerical Example 7 corresponds to Embodiment 7 shown in FIG. 13. Data of the zoom lens system according to Numerical Example 7, i.e., the surface data, the aspherical data, the various data, the lens element data, the zoom lens unit data, and the zoom lens unit magnification are shown in Table 37, Table 38, Table 39, Table 40, Table 41, and Table 42, respectively.







TABLE 37







(Surface data)











Surface number
r
d
nd
vd





Object surface
∞





 1
34.98260
2.00000
1.83481
42.7


 2
20.91070
0.10000
1.51358
51.5


 3*
20.10540
5.24770


 4
28.16500
1.80000
1.80420
46.5


 5
17.40950
3.01750


 6
22.94070
1.70000
1.80800
40.9


 7*
12.33290
7.58410


 8
−76.20100
0.99820
1.49700
81.6


 9
20.06080
3.79030
1.80610
33.3


10
92.44010
Variable


11
21.64480
0.69650
1.74400
44.8


12
6.34930
3.28500
1.68893
31.2


13
219.85800
1.84030


14 (Diaphragm)
∞
Variable


15
193.13050
0.70000
1.84666
23.8


16
12.68210
2.68480
1.51680
64.2


17
−17.27710
0.97100


18
−9.70000
0.80730
1.51742
52.1


19
∞
3.03910
1.51742
52.1


20
−18.28920
0.19950


21
−43.02110
1.69640
1.49700
81.6


22
−20.25080
0.27020


23
49.40670
3.14070
1.49700
81.6


24
−18.15150
Variable


25
28.93600
0.96040
1.51742
52.1


26
18.53510
Variable


27
−1362.70280
0.90090
1.80518
25.5


28
42.39530
2.82070
1.52300
70.1


29*
−29.17310
BF


Image surface
∞
















TABLE 38







(Aspherical data)








Surface



No.
Parameters











3
K = −2.35976E−01, A4 = 5.47891E−06, A6 = −1.50170E−09,



A8 = −1.08127E−11, A10 = 6.68891E−15,



A12 = −1.45786E−17


7
K = −1.25675E+00, A4 = 2.76324E−05, A6 = 6.29138E−08,



A8 = −1.42803E−11, A10 = 2.94442E−13,



A12 = −2.03884E−15


29
K = 2.54186E−02, A4 = 6.83869E−05, A6 = 8.18446E−08,



A8 = 7.76681E−10, A10 = −1.11959E−12,



A12 = −7.22409E−16
















TABLE 39







(Various data)


Zooming ratio 1.88052











Wide
Middle
Telephoto
















Focal length
7.2243
9.8927
13.5855



F-number
4.06339
3.88367
4.08364



View angle
59.0597
48.7147
38.0758



Image height
10.8150
10.8150
10.8150



Overall length of lens
96.4894
91.3856
89.6074



system



BF
15.30610
15.31409
15.32811



d10
19.9455
9.9370
2.6861



d14
2.6700
2.4800
1.4000



d24
3.0288
2.3581
2.2278



d26
5.2884
11.0458
17.7148



Entrance pupil position
19.2217
18.2131
17.1107



Exit pupil position
−53.5278
−66.6235
−76.3525



Front principal point
25.6878
26.9114
28.6831



position



Back principal point
89.2651
81.4929
76.0219



position

















TABLE 40







(Lens element data)









Unit
Initial surface No.
Focal length












1
1
−62.6421


2
4
−61.2591


3
6
−35.5557


4
8
−31.8426


5
9
31.0579


6
11
−12.3158


7
12
9.4311


8
15
−16.0602


9
16
14.5975


10
18
−18.7469


11
19
35.3469


12
21
75.1259


13
23
27.1282


14
25
−102.8995


15
27
−51.0499


16
28
33.4962
















TABLE 41







(Zoom lens unit data)
















Front




Initial

Length of
principal



surface

lens
point
Back principal


Unit
No.
Focal length
unit
position
point position















1
1
−14.57691
26.23780
8.79535
14.27683


2
11
43.69483
5.82180
−0.47326
1.18738


3
15
21.89206
13.50900
10.67027
16.66186


4
25
−102.89954
0.96040
1.81806
2.12497


5
27
91.53606
3.72160
3.56427
4.97749
















TABLE 42







(Zoom lens unit magnification)












Initial surface





Unit
No.
Wide
Middle
Telephoto














1
1
0.00000
0.00000
0.00000


2
11
−18.87227
5.67966
2.92388


3
15
0.02510
−0.10926
−0.27755


4
25
1.23602
1.29208
1.35708


5
27
0.84651
0.84642
0.84627









Numerical Example 8
The zoom lens system of Numerical Example 8 corresponds to Embodiment 8 shown in FIG. 15. Data of the zoom lens system according to Numerical Example 8, i.e., the surface data, the aspherical data, the various data, the lens element data, the zoom lens unit data, and the zoom lens unit magnification are shown in Table 43, Table 44, Table 45, Table 46, Table 47, and Table 48, respectively.







TABLE 43







(Surface data)













Surface number
r
d
nd
vd







Object surface
∞






 1
35.59120
2.00000
1.80420
46.5



 2
19.60000
6.20930



 3*
46.52590
2.00000
1.80470
41.0



 4
18.71380
3.37540



 5
25.12170
1.00000
1.80420
46.5



 6
18.02350
7.21140



 7
−34.36390
1.00000
1.49700
81.6



 8
76.37600
2.05840
1.84666
23.8



 9
551.50130
Variable



10*
157.15760
2.55990
1.62628
46.4



11
−6.95040
0.70000
1.71758
55.1



12
−24.79060
Variable



13 (Diaphragm)
∞
6.00000



14
99.20010
0.70000
1.84505
24.2



15
20.82540
6.70280
1.55487
64.3



16
−20.27800
0.20000



17
21.98820
1.81340
1.72799
28.1



18
89.55920
Variable



19*
−49.61050
1.88350
1.49700
81.6



20
−16.09080
0.20000



21
−36.25520
0.70000
1.49700
81.6



22
−50.08650
1.00000
1.82611
25.3



23
16.18320
1.15230



24
41.30550
3.13680
1.48890
70.3



25
−21.08640
BF



Image surface
∞

















TABLE 44







(Aspherical data)








Surface



No.
Parameters











3
K = 0.00000E+00, A4 = 1.56544E−05, A6 = 1.56679E−08,



A8 = 1.10484E−10, A10 = −6.49881E−13,



A12 = 1.43574E−15


10
K = 0.00000E+00, A4 = −1.03960E−06, A6 = −1.13322E−07,



A8 = 4.24478E−08, A10 = 0.00000E+00,



A12 = 0.00000E+00


19
K = 0.00000E+00, A4 = −6.89822E−05, A6 = −4.22724E−07,



A8 = 6.04668E−09, A10 = 0.00000E+00,



A12 = 0.00000E+00
















TABLE 45







(Various data)


Zooming ratio 1.94428











Wide
Middle
Telephoto
















Focal length
7.5030
10.4480
14.5880



F-number
4.05212
4.05214
4.05235



View angle
58.1750
48.3024
37.2049



Image height
10.8150
10.8150
10.8150



Overall length of lens
100.5550
92.5102
88.7805



system



BF
19.65911
20.44391
21.39269



d9
22.7797
10.9625
2.4000



d12
4.0409
4.2922
4.2922



d18
2.4721
5.2084
9.0924



Entrance pupil position
18.7789
17.9213
16.8818



Exit pupil position
−29.4478
−31.1871
−33.5144



Front principal point
25.1355
26.2550
27.5940



position



Back principal point
93.0520
82.0622
74.1925



position

















TABLE 46







(Lens element data)









Unit
Initial surface No.
Focal length












1
1
−57.4468


2
3
−40.1923


3
5
−84.6334


4
7
−47.5446


5
8
104.5015


6
10
10.6920


7
11
−13.6837


8
14
−31.3205


9
15
19.6603


10
17
39.5850


11
19
47.0403


12
21
−268.6786


13
22
−14.7054


14
24
29.0330
















TABLE 47







(Zoom lens unit data)
















Front




Initial

Length of
principal



surface

lens
point
Back principal


Unit
No.
Focal length
unit
position
point position















1
1
−12.50248
24.85450
9.28615
14.61265


2
10
50.49791
3.25990
1.86473
3.12977


3
13
20.66907
15.41620
10.95416
14.51666


4
19
−87.88159
8.07260
−5.69078
−4.43423
















TABLE 48







(Zoom lens unit magnification)












Initial surface





Unit
No.
Wide
Middle
Telephoto














1
1
0.00000
0.00000
0.00000


2
10
16.24168
3.38314
2.14987


3
13
−0.02705
−0.17965
−0.39166


4
19
1.36601
1.37494
1.38574









The following Tables 49 and 50 show values corresponding to the individual conditions in the zoom lens systems of the respective numerical examples.







TABLE 49







(Corresponding values to individual conditions:


Numerical Examples 1-4)









Numerical Example











Condition
1
2
3
4















(1)
fW/f1
−0.483
−0.484
−0.500
−0.506


(2)
fW/f2
0.177
0.170
0.192
0.163


(3)
fW/f3
0.320
0.322
0.317
0.328


(4)
fW/f4
−0.071
−0.071
−0.077
−0.086


(5)
fW/f5
0.089
0.090
0.106
0.104


(6)
DISW
−9.81
−10.44
−9.50
−9.74


(7)
(R11 + R12)/(R11 − R12)
4.184
4.221
4.262
4.099


(8)
(R21 + R22)/(R21 − R22)
3.750
3.755
3.900
4.017


(9)
(R31 + R32)/(R31 − R32)
3.535
3.522
3.506
3.402


(10)
DL/YM
1.658
1.636
1.650
1.597


(11)
BFW/YM
1.422
1.423
1.422
1.421



2ωW(°)
118.03
118.35
117.85
118.00


(12)
fW/f12W
—
—
—
—


(13)
fW/f3
—
—
—
—


(14)
fW/f4
—
—
—
—


(15)
fW/f5
—
—
—
—


(16)
fW/f6
—
—
—
—
















TABLE 50







(Corresponding values to individual conditions:


Numerical Examples 5-8)









Numerical Example











Condition
5
6
7
8















(1)
fW/f1
−0.482
—
−0.496
−0.600


(2)
fW/f2
0.172
—
0.165
0.149


(3)
fW/f3
0.350
—
0.330
0.363


(4)
fW/f4
−0.070
—
−0.070
−0.085


(5)
fW/f5
0.040
—
0.079
—


(6)
DISW
−9.82
−9.86
−10.26
−10.54


(7)
(R11 + R12)/(R11 − R12)
4.407
5.034
3.703
3.451


(8)
(R21 + R22)/(R21 − R22)
4.583
4.350
4.237
2.346


(9)
(R31 + R32)/(R31 − R32)
2.794
2.700
3.325
6.078


(10)
DL/YM
1.444
1.487
1.582
1.245


(11)
BFW/YM
1.421
1.422
1.415
1.818



2ωW(°)
118.04
118.06
118.12
116.35


(12)
fW/f12W
—
−0.529
—
—


(13)
fW/f3
—
0.175
—
—


(14)
fW/f4
—
0.334
—
—


(15)
fW/f5
—
−0.074
—
—


(16)
fW/f6
—
0.059
—
—









The zoom lens system according to the present invention is applicable to a digital input device such as a digital still camera, a digital video camera, a mobile telephone, a PDA (Personal Digital Assistance), a surveillance camera in a surveillance system, a Web camera or a vehicle-mounted camera. In particular, the present zoom lens system is suitable for an imaging device in a digital still camera, a digital video camera or the like that requires high image quality.
While the invention has been described in detail, the foregoing description is in all aspects illustrative and not restrictive. It is understood that numerous other modifications and variations can be devised without departing from the scope of the invention.

## Claims

1. A zoom lens system comprising a plurality of lens units and an aperture diaphragm arranged in the lens units, and performing zooming by changing intervals among the lens units, wherein
the plurality of lens units, in order from an object side to an image side, includes:
a first lens unit having negative optical power;
a second lens unit having positive optical power;
a third lens unit having positive optical power; and
a fourth lens unit having negative optical power,

the fourth lens unit moves to the image side along an optical axis at the time of focusing from an infinity in-focus condition to a close-point in-focus condition, and
the zoom lens unit satisfies the following condition:


−0.1<fW/f4<−0.05  (4)

where,
f4 is a focal length of the fourth lens unit, and
fw is a focal length of an entire system at a wide-angle limit.

2. The zoom lens system as claimed in claim 1, wherein, at the time of zooming from a wide-angle limit to a telephoto limit, the first lens unit, the second lens unit, the third lens unit, and the fourth lens unit move in a direction along an optical axis thereby to change intervals between the respective lens units.

3. The zoom lens system as claimed in claim 1, wherein the aperture diaphragm is arranged in the second lens unit.

4. The zoom lens system as claimed in claim 1, further comprising:
a fifth lens unit arranged on the image side relative to the fourth lens unit.

5. The zoom lens system as claimed in claim 4, wherein the fifth lens unit has positive optical power.

6. The zoom lens system as claimed in claim 1, wherein the fourth lens unit consists of one negative lens element having negative optical power.

7. The zoom lens system as claimed in claim 1, satisfying the following condition:


DISW<−8  (6)

where,
DISW is distortion (%) at a maximum image height at a wide-angle limit.

8. The zoom lens system as claimed in claim 1, satisfying the following condition:


−0.65<fW/f1<−0.45  (1)

where,
f1 is a focal length of the first lens unit, and
fw is a focal length of an entire system at a wide-angle limit.

9. The zoom lens system as claimed in claim 1, satisfying the following condition:


0.1<fW/f2<0.3  (2)

where,
f2 is a focal length of the second lens unit, and
fw is a focal length of an entire system at a wide-angle limit.

10. The zoom lens system as claimed in claim 1, satisfying the following condition:


0.25<fW/f3<0.5  (3)

where,
f3 is a focal length of the third lens unit, and
fw is a focal length of an entire system at a wide-angle limit.

11. The zoom lens system as claimed in claim 4, satisfying the following condition:


0.01<fW/f5<0.15  (5)

where,
f5 is a focal length of the fifth lens unit, and
fw is a focal length of an entire system at a wide-angle limit.

12. An interchangeable lens apparatus, comprising:
a zoom lens system including a plurality of lens units and an aperture diaphragm arranged in the lens units, and performing zooming by changing intervals among the lens units; and
a mount section connected to a camera body that includes an image sensor which receives an optical image formed by the zoom lens system thereby to convert the optical image to an electrical image signal, wherein
the plurality of lens units, in order from an object side to an image side, includes:
a first lens unit having negative optical power;
a second lens unit having positive optical power;
a third lens unit having positive optical power; and
a fourth lens unit having negative optical power,

the fourth lens unit moves to the image side along an optical axis at the time of focusing from an infinity in-focus condition to a close-point in-focus condition, and
the zoom lens unit satisfies the following condition:


−0.1<fW/f4<−0.05  (4)

where,
f4 is a focal length of the fourth lens unit, and
fW is a focal length of an entire system at a wide-angle limit.

13. A camera system, comprising:
an interchangeable lens apparatus that includes a zoom lens system including a plurality of lens units and an aperture diaphragm arranged in the lens units, and performing zooming by changing intervals among the lens units; and
a camera body which is connected to the interchangeable lens apparatus via a camera mount section in an attachable and removable manner and includes an image sensor which receives an optical image formed by the zoom lens system thereby to convert the optical image to an electrical image signal, wherein
the plurality of lens units, in order from an object side to an image side, includes:
a first lens unit having negative optical power;
a second lens unit having positive optical power;
a third lens unit having positive optical power; and
a fourth lens unit having negative optical power,

the fourth lens unit moves to the image side along an optical axis at the time of focusing from an infinity in-focus condition to a close-point in-focus condition, and
the zoom lens unit satisfies the following condition:


−0.1<fW/f4<−0.05  (4)

where,
f4 is a focal length of the fourth lens unit and
fw is a focal length of an entire system at a wide-angle limit.