JP2003098434A - Zoom lens and optical equipment having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a zoom lens having a high variable power ratio, having high optical performance capable of sufficiently copying with a situation even in the case of using a solid-state imaging element consisting of many pixels, and optical equipment having the zoom lens. SOLUTION: This zoom lens is provided with a 1st lens group immovable in the optical axis direction in the case of variable power and focusing and having positive refractive power, a 2nd lens group having a variable power function and having negative refractive power, a 3rd lens group having positive refractive power and a 4th lens group having a function for correcting an image surface fluctuated by the variable power and a focusing function and having positive refractive power in this order from the object side. The 1st lens group has one or more negative lenses and a plurality of positive lenses and satisfies conditional expressions; 30<ν-<40, Pgf-<0.6 and ν+>75, where the Abbe number of the material of one negative lens in the 1st lens group is ν-, the partial dispersion ratio thereof is Pgf- and the average Abbe number of the material of a plurality of positive lenses in the 1st lens group is ν+.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens suitable for a still camera, a video camera, a silver halide photography camera, a digital still camera and the like, and an optical apparatus having the zoom lens.

In addition to the above, according to the present invention, a part of the lens group of the optical system is moved so as to have a component in the direction perpendicular to the optical axis, so that an image (image) taken when the optical system vibrates (tilts). It has a zoom lens with an anti-vibration function, which is suitable for video cameras, silver halide photography cameras, digital cameras, etc. that stabilize the captured image by optically correcting the blur to obtain a still image. It relates to an optical device.

[0003]

2. Description of the Related Art When an image is captured from a moving object such as a car or an airplane in progress, vibration is transmitted to the image capturing system, which causes camera shake to cause blur in a captured image. Conventionally, various anti-vibration optical systems (zoom lenses) having a function (anti-vibration function) of preventing blur of a captured image have been proposed.

For example, in Japanese Unexamined Patent Publication No. 56-21133, an optical device is provided with a detecting means for detecting a vibration state, and a part of optical members in the optical device is provided in accordance with an output signal from the detecting means. By moving the image in a direction that cancels the vibrational displacement of the image, the image blur is corrected (anti-vibration is performed) to stabilize the image. JP-A-61-223
According to Japanese Patent No. 819, in an image pickup system in which a variable apex angle prism is arranged closest to the object side, the blurring of the image is corrected by changing the prism apex angle of the variable apex angle prism in response to the vibration of the image pickup system. We are trying to stabilize. Japanese Patent Laid-Open No. 1-11
In Japanese Patent No. 6619 and Japanese Patent Application Laid-Open No. 2-124521,
Vibration of the imaging system is detected using an acceleration sensor, and a still image is obtained by vibrating some lens groups of the imaging system in the direction perpendicular to the optical axis according to the signal obtained at this time.

Further, in Japanese Patent Laid-Open No. 7-128619,
In a variable power optical system having a four-group configuration including first, second, third, and fourth lens units having positive, negative, positive, and positive refracting powers, the third lens unit includes two lenses having positive and negative refracting powers. The image blur is corrected by vibrating the lens group having a positive refractive power. In Japanese Patent Laid-Open No. 7-199124, in a variable power optical system having a four-group configuration including first, second, third, and fourth lens units having positive, negative, positive, and positive refractive power, the entire third lens unit is used. The image is corrected by vibrating. On the other hand, in JP-A-5-60974, positive, negative,
In a zoom lens having a four-group configuration including first, second, third, and fourth lens groups having positive and positive refractive powers, the third lens group is a telephoto type lens including a positive lens and a meniscus-shaped negative lens. We are trying to shorten the total length.

Further, the present applicant has filed Japanese Patent Application No. 11-2133.
No. 70, the first, the second, and the positive, negative, positive, and positive refractive powers.
Disclosed is a zoom lens having a four-group configuration including a third lens group and a fourth lens group, in which the entire third lens group is vibrated to correct image blur. Further, the first lens group has three lens structures, in order from the object side, a cemented lens including a negative lens and a positive lens, and a positive meniscus lens having a convex surface facing the object side.

Also, US Pat. No. 5,583,699, US Pat. No. 5,886,828, and JP-A-7-92431.
In the publication, in a zoom lens having a four-group configuration including first, second, third, and fourth lens groups having positive, negative, positive, and positive refractive powers, the first lens group is arranged in order from the object side to a negative lens. A zoom lens is disclosed in which a cemented lens including a lens and a positive lens and two meniscus-shaped positive lenses each having a convex surface facing the object side are provided, and a total of four lenses are provided.

In Japanese Patent Laid-Open No. 2000-305016, the positive, negative, positive and positive refractive powers of the first, second, third, and
In the four-group zoom lens including the fourth lens group, by using a lens made of a glass material having a small dispersion for the first lens group, chromatic aberration is improved especially at the telephoto end.

[0009]

Generally, a vibration isolation means for correcting image blur is arranged in front of the photographing system, and a part of the movable lens group (movable member) constituting the vibration isolation means is vibrated. The method of eliminating the blur of the photographed image and obtaining the still image has a problem that the entire apparatus becomes large and a moving mechanism for moving the movable lens group becomes complicated.

Further, in an optical system for performing image stabilization using a variable apex angle prism, there is a problem that the amount of eccentric magnification chromatic aberration is increased during image stabilization, especially on the long focal length side.

On the other hand, in the image stabilization optical system for performing image stabilization by decentering a part of the lenses of the image pickup system in the direction perpendicular to the optical axis, a special extra optical system is required for image stabilization. Although there is an advantage of not doing so, there is a problem that a space for a lens to be moved is required, and an amount of decentration aberration generated during image stabilization becomes large.

Further, in a variable power optical system having a four-group structure consisting of first, second, third and fourth lens units having positive, negative, positive and positive refractive powers, the entire third lens unit is perpendicular to the optical axis. When the third lens group is composed of a telephoto type of a positive lens and a meniscus negative lens in order to shorten the overall length when performing image stabilization by moving in the direction, there are many eccentric aberrations such as eccentric coma and eccentric field curvature. However, there is a problem that the image quality is deteriorated due to the occurrence.

Further, in the above-mentioned conventional example, a zoom ratio of 8 times or more can be applied to a video camera or the like, but when used in a digital camera using an image pickup means composed of many pixels of 1 million pixels or more. It was insufficient in terms of aberration correction.

The first lens unit includes a cemented lens composed of a negative lens and a positive lens, and one meniscus-shaped positive lens, for a total of 3 lenses.
When configured with a single lens, the lens configuration is simplified but has a zoom ratio of 8 times or more, and for an image pickup apparatus using a solid-state image pickup element including many pixels, correction of axial chromatic aberration on the telephoto side. Was insufficient, especially the correction of the secondary spectrum was insufficient.

Further, the first lens group is composed of a cemented lens composed of a negative lens and a positive lens, and two meniscus-shaped positive lenses, and the number of lenses is increased. At this time, low dispersion glass is used as the material of the positive lens. And the secondary spectrum is reduced. A zoom lens having an image stabilizing function having such a structure is proposed in Japanese Patent Application Laid-Open No. 7-92431, but the fourth lens group is fixed during zooming and one of the fourth lens group is fixed during image stabilizing. Since the part is vibrated, the number of constituent lenses of the fourth lens group is large, which is disadvantageous in terms of downsizing. Further, in the zoom lens having no image stabilizing function proposed in US Pat. No. 5,886,828 and US Pat. No. 5,583,699, the second lens group includes the negative lens 2
Since the zoom lens is composed of one element and one positive lens, the zoom lens for a digital camera using an image pickup unit having a zoom ratio of 8 times or more and including pixels of 1 million pixels or more, corrects chromatic aberration of magnification in the entire zoom range. Is not always enough.

Further, in Japanese Patent Laid-Open No. 2000-305016, a glass material having a small dispersion is used for the first lens group, but the partial dispersion of the negative lens is large, so that the effect of reducing the secondary spectrum is not sufficiently obtained. .

It is an object of the present invention to provide a zoom lens having high optical performance that can sufficiently cope with a solid-state image pickup device having a large zoom ratio and a large number of pixels, and an optical apparatus having the zoom lens. .

In addition, according to the present invention, when a relatively small and lightweight lens group forming a part of an optical system is moved so as to have a component in a direction perpendicular to the optical axis, and the optical system vibrates (tilts). By compensating for the image blur of the image, and by appropriately adjusting the configuration of the lens group for compensating for the pixel blur, the overall size of the device is reduced, the mechanism is simplified, and the load on the driving means is reduced. While having a vibration-proof function that satisfactorily corrects eccentric aberration when the lens unit is decentered, and satisfactorily corrects the secondary spectrum on the telephoto side.
An object of the present invention is to provide a zoom lens and an optical device including the same, which can sufficiently deal with a camera using an image sensor including pixels of 0,000 pixels or more.

[0019]

A zoom lens according to the present invention comprises, in order from the object side, a first lens unit having a positive refractive power which is immovable in the optical axis direction for zooming and focusing, and zooming. It has a second lens group having a negative refractive power having a function, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power having a function of correcting an image surface which varies due to zooming and a focusing function. In the zoom lens described above, the first lens group has one or more negative lenses and a plurality of positive lenses, the Abbe number of the material of one negative lens in the first lens group is ν-, and the partial dispersion ratio is Pgf-, the first
The average Abbe number of the materials of the positive lenses in the lens group is ν
It is characterized by satisfying the conditional expression of 30 <ν− <40 Pgf− <0.6ν +> 75 when +.

According to a second aspect of the present invention, in the first aspect of the present invention, the first lens group has, in order from the object side, a negative lens having a concave surface having a larger absolute value of refractive power toward the image side than the object side, and a positive lens. , And has a positive lens.

According to a third aspect of the present invention, in the first aspect, the first lens group has, in order from the object side, a negative lens having a concave surface having a larger absolute value of refractive power toward the image side than the object side, and a positive lens. , A positive lens, and a meniscus lens having a convex surface facing the object side.

In a fourth aspect of the present invention, when the focal length of the first lens group is f1 and the focal length of the negative lens in the first lens group is f1N in the first, second or third invention, <| F1N | / f1 <2.2 It is characterized by satisfying the conditional expression.

The invention of claim 5 is the invention of claim 1, 2, 3 or 4.
In the invention described above, the first lens group is characterized in that it has two or more positive lenses that satisfy ν1 +> 80 when the Abbe number of the material is ν1 +.

A sixth aspect of the present invention is the invention according to any one of the first to fifth aspects, in which the focal length of the second lens group is f
2. When the focal length of the entire system at the wide-angle end is fw and the focal length of the entire system at the telephoto end is ft,

[0025]

[Equation 2]

It is characterized in that the following conditional expression is satisfied.

The invention of claim 7 is the invention of any one of claims 1 to 6, wherein the radius of curvature of the object side surface of one negative lens in the first lens group is R11a, and the curvature of the image side surface is R11a. When the radius is R11b, -3.8 <(R11b + R11a) / (R11b-R1
It is characterized in that the conditional expression 1a) <− 2.0 is satisfied.

An eighth aspect of the present invention is characterized in that, in the invention of any one of the first to seventh aspects, the radius of curvature of the object side surface of the positive lens located closest to the object side of the first lens group is R12.
a, where R12b is the radius of curvature of the image side surface, 0.55 <(R12b + R12a) / (R12b-R1
The feature is that the conditional expression 2a) <1.1 is satisfied.

In a ninth aspect of the present invention, in the invention according to any one of the first to eighth aspects, the second lens group has, in order from the object side, a concave surface having a larger absolute value of refractive power on the image side than on the object side. It is characterized by having a meniscus-shaped negative lens directed toward it, a negative lens, a positive lens having a convex surface directed toward the object side, and a negative lens.

A tenth aspect of the present invention is the invention of any one of the first to ninth aspects, wherein the entire third lens group is displaced so as to have a component in a direction perpendicular to the optical axis, and the third lens group is displaced in a direction perpendicular to the optical axis. Is characterized in that the image position of is corrected.

The eleventh aspect of the present invention is the invention according to any one of the first to tenth aspects, wherein the third lens group has, in order from the object side, a positive lens G31 having a convex surface directed toward the object side and a concave surface directed toward the image side. Has a meniscus-shaped negative lens G32 facing the lens, and the radius of curvature of the object-side surface of the positive lens G31 is R31.
a, the radius of curvature of the image side surface is R31b, and the negative lens G32 is
Let R32a be the radius of curvature of the object-side surface and R32b be the radius of curvature of the image-side surface: 1.3 <(R31b + R31a) / (R31b-R31
a) <2.3-4.0 <(R32b + R32a) / (R32b-R3)
2a) <-1.5 is satisfied.

The twelfth aspect of the invention is characterized in that the zoom lens of the first to eleventh aspects is an optical system for forming an image on an image pickup device.

The optical equipment of the invention of claim 13 is the optical equipment of claim 1
The zoom lens according to any one of 12 and an image pickup device that receives an image formed by the zoom lens.

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the zoom lens of the present invention and an optical apparatus having the same will be described below.

FIG. 1 is a lens cross-sectional view at the wide-angle end according to the first embodiment of the present invention, and FIGS. 2, 3 and 4 are aberration diagrams at the wide-angle end, an intermediate zoom position, and a telephoto end according to the first embodiment of the present invention. is there.

FIG. 5 is a lens cross-sectional view at the wide-angle end according to the second embodiment of the present invention, and FIGS. 6, 7 and 8 are aberration diagrams at the wide-angle end, an intermediate zoom position and a telephoto end according to the second embodiment of the present invention. is there.

FIG. 9 is a lens cross-sectional view at the wide-angle end according to the third embodiment of the present invention, and FIGS. 10, 11, and 12 are aberration diagrams at the wide-angle end, an intermediate zoom position, and a telephoto end according to the third embodiment of the present invention. is there.

FIG. 13 is a schematic view of the essential portions of the paraxial refractive power arrangement of the zoom lens of the present invention.

FIG. 14 is an explanatory view of an optical principle for correcting an image blur caused when the optical system vibrates in the present invention.

In the lens cross-sectional views of the zoom lens of each embodiment and FIG. 13, L1 is the first lens group having a positive refractive power,
L2 is a second lens group having a negative refractive power, L3 is a third lens group having a positive refractive power, and L4 is a fourth lens group having a positive refractive power. SP is an aperture stop, which is located in front of the third lens unit L3.

G is an optical block corresponding to an optical filter, a face plate, or the like. IP is an image plane, and the image pickup surface of the image pickup means is located. FP is a flare cut diaphragm that cuts unnecessary light.

In each embodiment, by moving (shifting) all of the third lens unit L3 so as to have a component in the direction perpendicular to the optical axis, the blur of the photographed image when the entire optical system vibrates (tilts). Is being corrected. Incidentally, a part of the third lens unit L3 may be moved so as to have a component in the direction perpendicular to the optical axis to correct the blur of the captured image.

In each of the embodiments, the second lens unit L is moved as shown by the arrow during zooming from the wide-angle end to the telephoto end.
2 is moved to the image surface side, and the image surface variation due to zooming is corrected by moving the fourth lens unit L4. Further, a rear focus type in which focusing is performed by moving the fourth lens unit L4 on the optical axis is adopted. Fourth lens unit L
The solid curve 4a and the dotted curve 4b regarding 4 are the movement loci for correcting the image plane variation due to the magnification change from the wide-angle end to the telephoto end when focusing on an object at infinity and a short-distance object, respectively. Shows. The first lens unit L1 and the third lens unit L3 are immovable in the optical axis direction for zooming and focusing.

In each embodiment, the fourth lens unit L4
Is moved to correct the image plane variation due to zooming,
Focusing is performed by moving the fourth lens unit L4. In particular, as shown by the curves 4a and 4b, the zoom lens is moved so as to have a convex locus toward the object side during zooming from the wide-angle end to the telephoto end. Thereby, the third lens unit L3
By effectively utilizing the space between the fourth lens unit L4 and the fourth lens unit L4, the overall length of the lens can be effectively shortened. In each embodiment, for example, when focusing from an object at infinity to a near object at the telephoto end, the fourth lens unit L4 is moved forward as shown by an arrow 4c.

In each embodiment, the third lens unit L3
Is moved (shifted) so that it has a component in the direction perpendicular to the optical axis to correct the image blur when the entire optical system vibrates. As a result, image stabilization is performed without newly adding an optical member such as a variable apex angle prism or a lens group for image stabilization, and the overall size of the optical system is prevented from increasing.

Next, the optical principle of the image stabilizing system for moving the lens group so as to have a component in the direction perpendicular to the optical axis to correct the blur of the photographed image will be described with reference to FIG.

As shown in FIG. 14A, the optical system has, in order from the object point P side, a fixed group (fixed lens group) Y1, a decentering group (decentering lens group, shift group) Y2, and a fixed group (fixed lens group). ) It is assumed that the object point P on the optical axis La, which is composed of three lens groups of Y3 and is sufficiently distant from the optical system, is imaged as an image point p at the center of the imaging plane IP. Now, assuming that the entire optical system including the imaging plane IP is momentarily tilted due to camera shake as shown in FIG. 14B, the object point P is also momentarily moved to the image point P ′, and a blurred image is obtained. Become. On the other hand, when the eccentric group Y2 is moved in the direction perpendicular to the optical axis La, as shown in FIG.
As shown in (C), the image point p moves to the point p ″, and the amount and direction of the movement depend on the refractive power arrangement of the optical system and are expressed as the decentering sensitivity of the lens group. In FIG. 14 (D), the image point p ′ deviated by camera shake is returned to the original image forming position p by moving the eccentric group Y2 by an appropriate amount in the direction perpendicular to the optical axis in B). As you can see, the camera shake is corrected, that is, the image stabilization is performed.

Assuming that the moving amount (shift amount) of the eccentric group Y2 required to correct the optical axis by θ ° is Δ, the focal length of the entire optical system is f, and the eccentricity sensitivity of the eccentric group Y2 is TS, Δ Is given by the following formula.

Δ = f · tan (θ) / TS Now, if the eccentricity sensitivity TS of the eccentricity group Y2 is too large, the movement amount Δ becomes a small value, but the movement amount of the shift group Y2 necessary for image stabilization can be made small. However, it becomes difficult to perform control for appropriately performing image stabilization, and correction remains. Particularly in video cameras and digital still cameras, the image size of the image sensor such as CCD is smaller than that of silver halide film and the focal length for the same angle of view is short. Therefore, the shift amount of the eccentric group Y2 for correcting the same angle is large. Δ becomes smaller. Therefore,
If the accuracy of the mechanism is about the same, the uncorrected amount on the screen will be relatively large.

On the other hand, if the eccentricity sensitivity TS is too small, the amount of movement of the eccentric group Y2 required for control becomes large, and the driving means such as an actuator for driving the eccentric group Y2 also becomes large.

In each embodiment, by setting the refractive power arrangement of each lens group to an appropriate value, the decentering sensitivity TS of the third lens group L3 is set to an appropriate value, and image stabilization due to mechanical control error is corrected. We have achieved a zoom lens that has less remaining and less load on driving means such as actuators.

Next, the features of the lens configuration of each embodiment will be described.

(A-1) The first lens unit L1 is arranged in order from the object side to the negative lens G11, the positive lens G12, and the object side having a concave surface having a large absolute value of the refractive power toward the image side as compared to the object side. Two meniscus positive lenses G1 with convex surfaces
3 and G14. The negative lens G11 and the positive lens G12 are independent or cemented.

In the first embodiment, the positive lens G12 and the positive lens G14 are used. In the second embodiment, the positive lens G12 is used. In the third embodiment, the positive lens G12, the positive lens G13, and the positive lens G14 are formed by using an abnormal dispersion glass material. The chromatic aberration that occurs in the first lens L1 group, particularly the secondary spectrum, which is difficult to correct when the focal length becomes long, is satisfactorily corrected.

Particularly in the second embodiment, the second-order spectrum is satisfactorily corrected by using an abnormally dispersive glass material having an Abbe number νd of 90 or more for the positive lens G12.

In order to suppress the secondary spectrum, the Abbe number of the material of the negative lens G11 in the first lens unit L1 is ν
-, When the partial dispersion ratio is Pgf, the conditional expression 30 <ν- <40 (1) Pgf- <0.6 (2) is satisfied. However, Pgf = (Ng-Nf) / (Nf-Nc) Ng, Nc, and Nf are the refractive indexes of the material with respect to the g-line, the c-line, and the f-line, respectively.

If the lower limit of conditional expression (1) is exceeded, the negative lens G
11 and the positive lens G12 material dispersion difference becomes large,
When performing achromatization with two wavelengths, the refracting power of each lens becomes weak, which is advantageous for correction of spherical aberration at the telephoto end, etc.
It becomes impossible to select an appropriate glass material for correcting the secondary spectrum. On the other hand, when the value exceeds the upper limit, the refracting power of each lens becomes too strong and spherical aberration and the like at the telephoto end become difficult, which is not preferable. If the upper limit of conditional expression (2) is exceeded, the difference between the partial dispersion ratios of the materials of the positive lens G12 and the negative lens G11 becomes large, and it becomes difficult to correct the secondary spectrum.

More preferably, the numerical ranges of the conditional expressions (1) and (2) are set to 32 <ν− <38 (1a) Pgf− <0.59 (2a).

(A-2) When the average Abbe number of the material of the plurality of positive lenses constituting the first lens unit L1 is ν +, the condition of ν +> 75 (3) is satisfied. If the lower limit of conditional expression (3) is exceeded, an attempt will be made to correct chromatic aberration under the condition of conditional expression (1), the refracting power of each lens will become too large, and other various aberrations will occur, especially spherical aberration and coma at the telephoto end. It is not good because it becomes difficult to correct.

More preferably, the numerical range of conditional expression (3) is set to ν +> 76 (3a) It is good to

(A-3) The negative lens is arranged closest to the object side in the first lens unit L1. As a result, the distance between the principal points between the first lens group and the second lens group is reduced so that the effective diameter of the front lens is reduced (A-4) Normally, in a zoom lens composed of four consumer lens groups. The first lens group is composed of one negative lens and two positive lenses, but since the low-dispersion glass material has a low refractive index, if it is used as it is in the first lens group, the curvature of each lens is large. Therefore, it becomes difficult to correct spherical aberration at the telephoto end.

Therefore, in each of the embodiments, the first lens unit L1 is configured by one negative lens and three positive lenses, so that the curvature of each lens surface of the positive lens can be set in an appropriate range, and the telephoto end The spherical aberration at is well corrected.

(A-5) When the focal length of the first lens unit L1 is f1 and the focal length of the negative lens G12 in the first lens unit L1 is f1N 1.2 <| f1N | / f1 <2.2 (4) The conditional expression is satisfied.

If the lower limit of conditional expression (4) is exceeded, it becomes difficult to correct distortion at the wide-angle end, which is not preferable.

If the upper limit is exceeded, chromatic aberration in the first lens unit L1 cannot be sufficiently corrected, which is not good.

More preferably, the numerical range of conditional expression (4) is set to       1.4 <| f1N | f1 <2.0 (4a) It is good to

(A-6) In Embodiments 1 and 3, when the Abbe number of the material in the first lens unit L1 is ν + in order to obtain a sufficient chromatic aberration correction effect, ν1 +> 80 (5) It has a plurality of positive lenses that satisfy the conditional expression.

(A-7) In order to reduce the size of the entire zoom lens system while maintaining good optical performance, the focal length of the second lens unit L2 is set to f2, and the focal length of the entire system at the wide-angle end is set. fw, when the focal length of the entire system at the telephoto end is ft

[0069]

[Equation 3]

The following conditional expression is satisfied.

Conditional expression (6) defines the refractive power of the first lens unit L1. When the lower limit of conditional expression (6) is exceeded and the refractive power of the first lens unit L1 becomes strong, conditional expression (1),
Even if the condition (2) is satisfied, the amount of secondary spectrum generated becomes large, which is not preferable. In addition, the chromatic aberration of magnification that occurs on the wide-angle side becomes large and correction becomes difficult, which is not preferable. On the contrary, when the upper limit is exceeded and the refractive power of the first lens unit L1 is weakened, the total lens length becomes long and it becomes difficult to downsize the entire system.

Conditional expression (7) defines the refractive power of the second lens unit L2. When the lower limit of conditional expression (7) is exceeded and the refractive power of the second lens unit L2 becomes strong, the movement amount of the second lens unit L2 at the time of zooming becomes small, but the Petzval sum becomes large in the negative direction overall. It is not good because it becomes difficult to correct the field curvature. On the contrary, if the upper limit of conditional expression (7) is exceeded,
This is not good because the amount of movement of the second lens unit L2 during zooming becomes large and the overall lens system does not become compact.

More preferably, the numerical ranges of conditional expressions (6) and (7) are

[0074]

[Equation 4]

It is preferable that

(A-8) A zoom lens for a digital still camera is required to have a high resolution, and in particular, chromatic aberration of magnification due to zooming is better corrected as compared with a zoom lens for a normal video camera. Is required to do so. Therefore, the second lens unit L2 is composed of three or more negative lenses and one or more positive lenses. With only two negative lenses, if the refractive power of the second lens unit L2 is increased to reduce the amount of movement during zooming in order to shorten the overall length, it becomes difficult to correct lateral chromatic aberration. Therefore, the second lens unit L2 is arranged in order from the object side, a meniscus-shaped negative lens having a concave surface having a larger absolute value of refractive power toward the image side than to the object side, a negative lens, and a positive lens having a convex surface facing toward the object side. With the configuration including the negative lens, the achromatic point of the principal point of the second lens unit L2 is effectively performed, and the variation of the chromatic aberration of magnification due to the magnification change is satisfactorily corrected.

(A-9) In order to satisfactorily correct various aberrations such as spherical aberration and distortion, the radius of curvature of the object-side surface of the negative lens G11 in the first lens unit L1 is R11a, and that of the image-side surface is R11a. When the radius of curvature is R11b, the conditional expression of −3.8 <(R11b + R11a) / (R11b−R11a) <− 2.0 (8) is satisfied.

If the lower limit of conditional expression (8) is exceeded, it becomes difficult to correct spherical aberration at the telephoto end, which is not preferable. On the contrary, if the upper limit is exceeded, it becomes difficult to correct distortion at the wide-angle end, which is not preferable.

More preferably, the numerical range of the conditional expression (8) is set to -3.0 <(R11b + R11a) / (R11b-R11a) <-2.2 (8a).

(A-10) Let R be the radius of curvature of the object-side surface of the most object-side positive lens G12 of the first lens unit L1.
12a, and the radius of curvature of the image-side surface is R12b, the conditional expression 0.55 <(R12b + R12a) / (R12b-R12a) <1.1 ... (9) is satisfied.

If the lower limit of conditional expression (9) is exceeded, it becomes difficult to correct spherical aberration at the telephoto end, which is not preferable. On the contrary, if the upper limit is exceeded, it becomes difficult to correct distortion at the telephoto end.

More preferably, the numerical range of conditional expression (9) is set to       0.60 <(R12b + R12a) / (R12b-R12a) <1.0 ・ (9a) It is good to

(A-11) Vibration is prevented by shifting the third lens group so that a part or all of L3 has a component in the direction perpendicular to the optical axis. In each embodiment, the entire third lens L3 is shifted.

In order to keep the optical performance, especially the optical performance at the time of anti-vibration excellent, and to reduce the total optical length, the third lens unit L3 is composed of two or more positive lenses and one or more negative lenses. I am configuring. In particular, the third lens unit L3 is arranged in order from the object side, a positive lens having a convex surface facing the object side and a meniscus-shaped negative lens having a concave surface having a larger absolute value of refractive power on the image surface side than on the object side. Aims to achieve both aberration correction and shortening the overall length.

In order to achieve even better optical performance, the radius of curvature of the object side surface of the positive lens located closest to the object side in the third lens unit L3 is R31a, and the radius of curvature of the image side surface is R31b. , The radius of curvature of the object-side surface of the negative lens of the third lens unit L3 is R32a, and the radius of curvature of the image-side surface is R32b.
Then, 1.3 <(R31b + R31a) / (R31b-R31a) <2.3 ... (10) -4.0 <(R32b + R32a) / (R32b-R32a) <-1.5 ... ( The conditional expression (11) is satisfied.

Conditional expression (10) is an expression which defines the shape factor of the positive lens closest to the object side in the third lens unit L3. When the upper limit of conditional expression (10) is exceeded and the degree of meniscus increases, coma aberration generated on each lens surface increases, and higher-order coma aberration occurs. In particular, the occurrence of decentering coma aberration at the time of image stabilization becomes remarkable, and the performance deteriorates at the time of image stabilization, which is not preferable. If the lower limit is exceeded and the shape is biconvex, the action of correcting lateral chromatic aberration occurring on the object side surface on the image side surface is weakened, which is not preferable.

Conditional expression (11) defines the form factor of the negative lens of the third lens unit L3. Conditional expression (11)
If the degree of meniscus is increased beyond the lower limit of, the primary axial chromatic aberration is overcorrected on the image-side lens surface, and the g-line is too much over the d-line, which is not preferable. Further, if the degree of the meniscus becomes weaker than the upper limit, the action of forming the third lens unit L3 in the telephoto configuration becomes weak and the entire lens length becomes long, which is not preferable.

When such a negative lens is provided, positive distortion occurs on the lens surface. This becomes a cause of large eccentric distortion during vibration isolation.

In order to reduce this decrease, it is sufficient to reduce the distortion aberration generated in the third lens unit L3 as a whole.

In each of the embodiments, by disposing the positive lens on the image side of the negative lens, the distortion is corrected in the third lens unit L3 while maintaining a certain degree of telephoto structure.
The occurrence of eccentric distortion that occurs when the third lens unit L3 is shifted for image stabilization is reduced.

More preferably, conditional expressions (10) and (11)
The numerical range of 1.5 <(R31b + R31a) / (R31b-R31a) <2.0 ... (10a) -3.5 <(R32b + R32a) / (R32b-R32a) <-2.0 ... ( 11a) is preferable.

(A-12) The fourth lens unit L4 is composed of two positive lenses and one negative lens, and spherical aberration caused by the movement of the fourth lens unit L4 during zooming or focusing. And the fluctuation of the field curvature are reduced.

Further, at least one positive lens in the fourth lens unit L4 has an aspherical surface.

(A-13) In order to achieve a reduction in light quantity change during image stabilization, the aperture diameter is reduced on the telephoto side to limit the central light flux during zooming, thereby relatively increasing the peripheral light quantity. I am trying.

Since the third lens unit L3 moves so as to have a component in the direction perpendicular to the main axis for image stabilization, it is necessary to increase the lens diameter accordingly. Therefore, a fixed diaphragm is arranged on the object side or the image plane side of the third lens unit L3 in order to prevent excessive axial light flux other than that regulated by the F number from entering too much. In each embodiment, the fixed diaphragm FP is disposed between the third lens unit L3 and the fourth lens unit L4 to effectively use the space and prevent unnecessary light flux from passing therethrough.

Next, an embodiment of a digital still camera (optical device) using the zoom lens of the present invention as a photographing optical system will be described with reference to FIG.

In FIG. 15, 10 is a camera body, and 11
Is a photographing optical system configured by the zoom lens of the present invention, and 12 is a finder for observing a subject image.

13 is a strobe device, 14 is a measurement window, and 15
Is a liquid crystal display window for notifying the operation of the camera, 16 is a release button, and 17 is an operation switch for switching various modes. Thus, by applying the zoom lens of the present invention to an optical device, a compact optical device having high optical performance is achieved.

As described above, according to each of the embodiments, the chromatic aberration at the telephoto end is satisfactorily corrected, and the zoom lens having good optical performance over the entire zoom range is realized by the above-mentioned configuration.

In particular, while having a large zoom ratio of 8 or more, the secondary spectrum on the telephoto side is favorably corrected and high optical performance is achieved, as compared with conventional zoom lenses for video cameras. It is possible to realize a zoom lens having an optical performance that is sufficiently compatible with a digital camera having a photographing element having 10,000 pixels or more and various optical devices having the zoom lens.

Next, each of Embodiments 1 to 3 of the present invention is supported.
Numerical Examples 1 to 3 will be shown. I in each numerical example
Is the order of the optical surfaces from the object side, and Ri is the i-th
The radius of curvature of the optical surface (i-th surface), Di is the i-th surface and the i-th surface
The distance between the surface and Ni and νi are
The refractive index and Abbe number of the material of the i-th optical member are shown. Well
Where k is the eccentricity and B, C, D, E, F ...
Number, the displacement along the optical axis at the height h from the optical axis
When x is based on a point, the aspherical shape is x = (h²/ R) / [1+ [1- (1 + k) (h / R)²]
^1/2] + Bh^Four+ Ch⁶+ Dh⁸+ Eh^Ten+ Fh¹²+ Gh¹⁴
+ Hh¹⁶ Is displayed. However, R is a radius of curvature. Also for example
The display of "e-Z" is "10 ^-ZMeans. Also, each number
Table 1 shows the correspondence with the above-mentioned conditional expressions in the value examples.
You

F is the focal length, Fno is the F number ω is the half angle of view.

[0103]

[Outer 1]

[0104]

[Outside 2]

[0105]

[Outside 3]

[0106]

[Table 1]

[0107]

According to the present invention, it is possible to achieve a zoom lens having a high optical performance that can sufficiently cope with the use of a solid-state image sensor having a high zoom ratio and a large number of pixels, and an optical apparatus having the zoom lens. be able to.

In addition to this, according to the present invention, the relatively small and lightweight lens group forming a part of the optical system is moved so as to have a component in the direction perpendicular to the optical axis, and the optical system vibrates (tilts). It is configured to correct the blurring of the image at the time,
By optimizing the configuration of the lens group for correcting the blurring of pixels, the lens group is eccentric while the overall size of the device is reduced, the mechanism is simplified, and the load on the driving unit is reduced. It has an anti-vibration function that satisfactorily corrects the eccentric aberration when
It is possible to achieve a zoom lens and an optical device including the zoom lens, which can sufficiently deal with a camera using an image sensor having pixels of, 000,000 pixels or more.

[Brief description of drawings]

FIG. 1 is a lens cross-sectional view of Numerical Example 1 of the present invention.

FIG. 2 is an aberration diagram at the wide-angle end according to Numerical Example 1 of the present invention.

FIG. 3 is an aberration diagram at a middle zoom position according to Numerical Example 1 of the present invention.

FIG. 4 is an aberration diagram at a telephoto end according to Numerical Example 1 of the present invention.

FIG. 5 is a lens cross-sectional view of Numerical Example 2 of the present invention.

FIG. 6 is an aberration diagram at a wide-angle end according to Numerical Example 2 of the present invention.

FIG. 7 is an aberration diagram at a middle zoom position in Numerical Example 2 of the present invention.

FIG. 8 is an aberration diagram at a telephoto end according to Numerical Example 2 of the present invention.

FIG. 9 is a lens cross-sectional view of Numerical Example 3 of the present invention.

FIG. 10 is an aberration diagram at a wide-angle end according to Numerical Example 3 of the present invention.

FIG. 11 is an aberration diagram at a middle zoom position in Numerical Example 3 of the present invention.

FIG. 12 is an aberration diagram at a telephoto end according to Numerical Example 3 of the present invention.

FIG. 13 is a schematic view of the paraxial refractive power arrangement of the zoom lens of the present invention.

FIG. 14 is an explanatory diagram of an optical principle of image stabilization according to the present invention.

FIG. 15 is a schematic view of a main part of an optical device of the present invention.

[Explanation of symbols]

L1 First lens group L2 Second lens group L3 Third lens group L4 Fourth lens group d d line g g line ΔM meridional image surface ΔS sagittal image surface SP diaphragm FP flare cut diaphragm IP imaging surface G CCD force plate or Glass block such as low-pass filter ω Half angle of view fno F number

Continued front page    F term (reference) 2H087 KA01 MA15 NA07 PA11 PA20                       PB14 QA02 QA07 QA17 QA21                       QA25 QA34 QA42 QA45 RA05                       RA12 RA13 RA32 RA37 RA42                       RA43 SA23 SA27 SA29 SA32                       SA63 SA65 SA72 SA74 SB05                       SB15 SB24 SB34

Claims (13)

[Claims] 1. A first lens unit having a positive refractive power which is immovable in the optical axis direction for zooming and focusing in order from the object side, a second lens unit having a negative refractive power having a zooming function, and a positive lens unit. In the zoom lens having the third lens unit having a refracting power and the fourth lens unit having a positive refracting power having a function of correcting an image surface that varies due to zooming and a focusing function, the first lens unit has at least one lens element. Negative lens and a plurality of positive lenses, the Abbe number of the material of one negative lens in the first lens group is ν-, the partial dispersion ratio is Pgf-, and the plurality of positive lenses in the first lens group A zoom lens characterized by satisfying a conditional expression: 30 <ν− <40 Pgf− <0.6ν +> 75, where ν + is the average Abbe number of the material 2. The first lens group, in order from the object side,
The zoom lens according to claim 1, further comprising a negative lens, a positive lens, and a positive lens having a concave surface having a larger absolute value of refractive power toward the image side than toward the object side. 3. The first lens group, in order from the object side,
2. A negative lens having a concave surface having a larger absolute value of refractive power on the image side than on the object side, a positive lens, a positive lens, and a meniscus lens having a convex surface facing the object side. Zoom lens. 4. When the focal length of the first lens group is f1 and the focal length of the negative lens in the first lens group is f1N, the conditional expression 1.2 <| f1N | / f1 <2.2 is satisfied. The zoom lens according to claim 1, 2 or 3, which is satisfied. 5. The first lens group has two or more positive lenses that satisfy ν1 +> 80 when the Abbe number of the material is ν1 +, and the first lens group has two or more positive lenses. The described zoom lens. 6. When the focal length of the second lens group is f2, the focal length of the entire system at the wide-angle end is fw, and the focal length of the entire system at the telephoto end is ft, then: 6. The following conditional expression is satisfied:
The zoom lens according to any one of 1. 7. When the radius of curvature of the object side surface and the radius of curvature of the image side surface of one negative lens in the first lens group are R11a and R11b, respectively, −3.8 <(R11b + R11a) / ( R11b-R1
7. The conditional expression 1a) <-2.0 is satisfied.
The zoom lens according to any one of 1. 8. When the radius of curvature of the object side surface of the positive lens located closest to the object side in the first lens group is R12a and the radius of curvature of the image side surface is R12b, 0.55 <(R12b + R12a) / (R12b-R1
7. The conditional expression 2a) <1.1 is satisfied.
The zoom lens according to any one of 1. 9. The second lens group, in order from the object side,
A negative lens having a meniscus shape having a concave surface with a larger absolute value of refractive power on the image side than on the object side, a negative lens, a positive lens having a convex surface on the object side, and a negative lens. The zoom lens according to any one of 8 above. 10. The image position is corrected in the direction perpendicular to the optical axis by displacing the entire third lens group so as to have a component in the direction perpendicular to the optical axis. The zoom lens according to any one of 1. 11. The third lens group, in order from the object side,
It has a positive lens G31 having a convex surface facing the object side and a meniscus-shaped negative lens G32 having a concave surface facing the image surface side. The radius of curvature of the object side surface of the positive lens G31 is R31a, and the image side surface is The radius of curvature is R31b, the radius of curvature of the object side surface of the negative lens G32 is R32a, and the radius of curvature of the image side surface is R3.
When 2b, 1.3 <(R31b + R31a) / (R31b-R31
a) <2.3-4.0 <(R32b + R32a) / (R32b-R3)
2. The conditional expression 2a) <-1.5 is satisfied.
The zoom lens according to any one of 0. 12. An optical system for forming an image on an image pickup device, as claimed in any one of claims 1 to 11.
The zoom lens according to item. 13. An optical apparatus comprising: the zoom lens according to claim 1; and an image pickup device that receives an image formed by the zoom lens.