JP2002311330A - Zoom lens and optical apparatus using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a zoom lens which utilizes negative lead type lens constitution, whose photographic viewing angle at a wide-angle end is 84 deg., whose variable power ratio is 2.9 and which has brightness that an F-number is about 2.9 in all the variable power range and has high optical performance in all the variable power range, and optical equipment using the zoom lens. SOLUTION: This zoom lens is provided with a 1st A lens group having negative refractive power, a 1st B lens group having negative refractive power, a 2nd lens group having positive refractive power, a 3rd lens group having negative refractive power and a 4th lens group having positive refractive power in order from an object side. Variable power is performed by moving the respective lens groups, and focusing from an infinity object to a short-distance object is performed by moving the 1st B lens group to the object side. Then, the synthetic focal distance f1AB of the 1st A lens group and the 1st B lens group and the focal distance (ft) of an entire system at a telephoto end are appropriately set.

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 photographic camera, a video camera, a video still camera, a digital camera, and the like, and an optical apparatus using the same.

In addition, the present invention adopts a negative lead type configuration in which a lens unit having a negative refractive power precedes, and has a photographic field angle of about 84 ° at the wide angle end while having a brightness of F number 2.9. The present invention relates to a zoom lens having a wide angle of view, a high zoom ratio of about 2.9, excellent aberration correction over the entire zoom range, and high optical performance, and an optical apparatus using the same.

[0003]

2. Description of the Related Art Conventionally, a so-called negative lead type zoom lens in which a lens unit having a negative refractive power precedes is widely used for a wide angle of view having a photographic angle of view of 70 ° or more because it is relatively easy to widen the angle of view. It is often used for zoom lenses.

For example, Japanese Patent Publication No. 49-29146 and Japanese Patent Publication No. 52-20018 disclose a first lens unit having a negative refractive power and a second lens unit having a positive refractive power in order from the object side.
There has been proposed a so-called two-unit zoom lens having two lens groups and performing zooming by changing the distance between both lens groups.

In the above two-unit zoom lens, the second lens unit having a positive refractive power is divided into three lens units having positive, negative, and positive refractive powers. The performed four-group zoom lens is disclosed in, for example, Japanese Patent Application Laid-Open No. 53-345.
39, JP-A-60-68311 and JP-A-6-68311.
It has been proposed in JP-A-3-241511, JP-A-1-193709 and the like.

In addition, JP-A-6-82698, JP-A-5-19170, and JP-A-7-287168 disclose a first group of negative refracting power and a positive refracting power in order from the object side. The zoom lens has four lens groups, a second group, a third group having a negative refractive power, and a fourth group having a positive refractive power. At the time of zooming, at least two of these lens groups are used. A zoom lens in which zooming is performed by moving the zoom lens has been proposed.

On the other hand, Japanese Patent Application Laid-Open No. 52-109952 discloses
JP-A-55-57815, JP-A-55-1171
No. 19, Japanese Patent Publication No. 61-53696, Japanese Patent Publication No. 5
In JP-A-2-41068 or the like, the first group is divided into a plurality of lens groups in a four-group zoom lens, and the lens group closest to the object is fixed during focusing, and the lens group on the image plane side behind it is fixed. A zoom lens using an inner focus that moves a part of the lens during focusing is disclosed.

[0008]

In recent years, a standard zoom lens used for a single-lens reflex camera, a video camera, or the like, which has a wide angle of view and has a high zoom ratio, has been demanded. In particular, there is a tendency to reduce the size of a shooting screen (imaging means), and a zoom lens having a wider angle of view is required.

In general, in a negative lead type zoom lens, a photographing angle of view at the wide-angle end is about 75 °, a zoom ratio is about 3 and an F at the wide-angle end while securing a predetermined back focus.
In order to obtain good optical performance over the entire zoom range while securing the number of about 3, it is necessary to appropriately set the refractive power arrangement of each lens group.

In general, if the refractive power of each lens unit in a zoom lens is increased, the amount of movement of each lens unit to obtain a predetermined zoom ratio is reduced, so that the angle of view is increased while shortening the overall length of the lens. Becomes easier.

However, if the refractive power of each lens group is simply increased, aberration fluctuation accompanying zooming becomes large, and it is difficult to obtain good optical performance over the entire zoom range, especially when widening the angle of view. There is a problem that comes.

For example, if the refractive power arrangement and the lens configuration of each lens group are inappropriate, even if the number of lenses is increased, the aberration variation accompanying zooming becomes large, and it is difficult to obtain high optical performance over the entire zoom range. It is becoming.

In particular, if the focal length at the wide-angle end is to be made shorter and the photographic field angle is to be made wider, the aberration variation accompanying zooming becomes larger.

On the other hand, the inner focus type zoom lens has a smaller effective diameter of the first lens unit as compared with a zoom lens which moves and focuses the entire first lens unit. Shooting, especially very close-up shooting, becomes easier, and since the relatively small and light lens group is moved, the driving force of the lens group can be small,
It has features such as quick focusing.

However, if an attempt is made to widen the angle of view of the lens system using the inner focus method, fluctuations in various aberrations due to focusing become remarkable, and it becomes extremely difficult to maintain good optical performance.

An object of the present invention is to provide a zoom lens having a wide angle of view and high optical performance over the entire zoom range, and an optical apparatus using the same.

In addition, the present invention achieves a wide angle of view, a large aperture, and a high zoom ratio while employing an inner focus method, and reduces fluctuations of various aberrations accompanying zooming and focusing, thereby achieving a full zoom. It is an object of the present invention to provide a zoom lens having high optical performance over a magnification range and an entire focus range, and an optical apparatus using the same.

In addition to the above, the present invention utilizes a negative lead type lens structure, has a photographic field angle of 84 ° at the wide angle end, a zoom ratio of 2.9, and an F number of about 2.9 in the entire zoom range. It is another object of the present invention to provide a zoom lens having high optical performance in the entire zoom range and an optical apparatus using the same.

[0019]

According to the first aspect of the present invention, there is provided a zoom lens according to the present invention. Lens group, third lens group with negative refractive power, fourth lens group with positive refractive power
In a zoom lens having a lens group, at the telephoto end with respect to the wide-angle end, the distance between the first A lens group and the first B lens group changes or is fixed, and the distance between the first B lens group and the second lens group is small. The magnification is changed by moving the lens groups so that the distance between the second lens group and the third lens group is large and the distance between the third lens group and the fourth lens group is small.
Each of the lens group and the first B lens group has an aspheric surface, and one of these aspheric surfaces is an aspheric surface having a negative refractive power that becomes stronger as the distance from the optical axis increases, and the other becomes a negative surface as the distance from the optical axis increases. It is characterized by being an aspheric surface whose refractive power becomes weak.

In the zoom lens according to the second aspect of the present invention, in order from the object side, a first A lens group having a negative refractive power, a first B lens group having a negative refractive power, a second lens group having a positive refractive power, and a negative refractive power. In a zoom lens having a third lens unit having a positive power and a fourth lens unit having a positive refractive power, the first lens unit at the telephoto end with respect to the wide angle end
The distance between the lens group and the first B lens group changes or is fixed, the distance between the first B lens group and the second lens group is small,
Zooming is performed by moving the lens groups so that the distance between the second lens group and the third lens group is large and the distance between the third lens group and the fourth lens group is small. Focusing is performed by moving the first B lens group toward the object side, and at the wide-angle end, the combined focal length of the first A lens group and the first B lens group when focusing on an object at infinity is f1AB, and the entire system at the telephoto end. The focal length of ft
Where −0.6 <f1AB / ft <−0.45 (1)

In the zoom lens according to the third aspect of the invention, in order from the object side, a first A lens group having a negative refractive power, a first B lens group having a negative refractive power, a second lens group having a positive refractive power, and a negative refractive power. In a zoom lens having a third lens unit having a positive power and a fourth lens unit having a positive refractive power, the first lens unit at the telephoto end with respect to the wide-angle end,
The distance between the lens group and the first B lens group changes or is fixed, the distance between the first B lens group and the second lens group is small,
The magnification is changed by moving the lens units so that the distance between the second lens group and the third lens group is large and the distance between the third lens group and the fourth lens group is small, and the 1A lens group and the 1B lens group Is the combined focal length of f1AB, the focal length of the entire system at the telephoto end is ft, and the F-number of the entire system at the telephoto end is F
In the case of NOT, the following condition is satisfied: -1.8 <f1AB * FNOT / ft <-1.3 (2)

According to a fourth aspect of the present invention, at the wide-angle end, the combined focal length of the first A lens group and the first B lens group when focusing on an object at infinity is f.
Assuming that 1AB, the focal length of the entire system at the telephoto end is ft, and the F number of the entire system at the telephoto end is FNOT, the following condition is satisfied: -1.8 <f1AB * FNOT / ft <-1.3 (2) Is satisfied.

According to a fifth aspect of the present invention, in the third aspect of the invention, focusing from an object at infinity to an object at a short distance is performed by the first B
It is characterized by moving the lens group to the object side.

According to a sixth aspect of the present invention, in the first aspect of the present invention, the combined focal length of the fourth lens unit is set to f.
4. When the focal length of the entire system at the wide-angle end is fw and the F-number of the entire system at the telephoto end is FNOT, the following condition is satisfied: 0.65 <f4 / (fw * FNOT) <0.95 (3) It is characterized by satisfaction.

A seventh aspect of the present invention is characterized in that, in the first, second or third aspect of the present invention, the fourth lens has at least three positive lenses and at least one negative lens.

The invention of claim 8 is the invention of claim 2, 3, 4 or 5.
The first A lens group, the first B lens group, the second
Any one of the lens group, the third lens group, and the fourth lens group has one or more aspheric surfaces.

The invention of claim 9 is the invention of claim 2, 3, 4, or 5.
The first invention is characterized in that each of the first A lens group and the first B lens group has one or more aspheric surfaces.

According to a tenth aspect of the present invention, in the first aspect of the present invention, the first A lens group has an aspheric surface whose negative refractive power becomes weaker as the distance from the optical axis increases. The group is characterized in that it has an aspherical surface whose negative refractive power increases as the distance from the optical axis increases.

According to an eleventh aspect of the present invention, when zooming from the wide-angle end to the telephoto end, the second lens unit and the fourth lens unit are integrated to move toward the object side in any one of the first to tenth aspects. It is characterized by moving.

According to a twelfth aspect of the present invention, in any one of the first to eleventh aspects, a flare cut stop is provided between the third lens unit and the fourth lens unit.

According to a thirteenth aspect of the present invention, an optical apparatus includes the zoom lens according to any one of the first to twelfth aspects.

[0032]

1 is a sectional view of a zoom lens according to a first numerical embodiment at a wide-angle end, FIG. 2 is an aberration diagram at a wide-angle end of the zoom lens according to the first numerical embodiment, and FIG. FIG. 4 is an aberration diagram at a telephoto end of a zoom lens.

FIG. 4 is a cross-sectional view of the zoom lens of Numerical Embodiment 2 at the wide-angle end, FIG. 5 is an aberration diagram of the zoom lens of Numerical Embodiment 2 at the wide-angle end, and FIG. It is an aberrational figure of an edge.

FIG. 7 is a sectional view of the zoom lens of Numerical Embodiment 3 at the wide-angle end, FIG. 8 is an aberration diagram of the zoom lens of Numerical Embodiment 3 at the wide-angle end, and FIG. It is an aberrational figure of an edge.

FIG. 10 is a sectional view of the zoom lens of Numerical Embodiment 4 at the wide-angle end, FIG. 11 is an aberration diagram of the zoom lens of Numerical Embodiment 4 at the wide-angle end, and FIG. It is an aberrational figure of an edge.

In each lens cross-sectional view, L1 denotes a first group (first lens group) having a negative refractive power, and a first lens group A having a negative refractive power.
It has a lens unit L1A and a first B lens unit L1B having a negative refractive power.

L2 is a second group (second lens group) having a positive refractive power, L3 is a third group (third lens group) having a negative refractive power, L
Reference numeral 4 denotes a fourth group (fourth lens group) having a positive refractive power. SP
Denotes an aperture stop, FC denotes a fixed flare cut stop, and IP denotes an image plane.

Arrows indicate the trajectories of the movements of the respective lens units when zooming from the wide-angle end to the telephoto end. At the wide-angle end and the telephoto end, the zoom position is defined as the zoom position when the zooming lens group is located at both ends of the mechanically movable range on the optical axis.

In this embodiment, when zooming from the wide-angle end to the telephoto end, the first A lens unit L1A and the first B lens unit L
1B, the third lens unit L3 has a part of a locus convex on the image plane side, and both the second and fourth units are moved to the object side.

At this time, the distance between the first A lens unit L1A and the first B lens unit L1B at the telephoto end with respect to the wide angle end changes,
Alternatively, the distance between the first lens unit L1B and the second lens unit L2 is small, the distance between the second lens unit and the third lens unit is large, and the distance between the third lens unit and the fourth lens unit is small. I have to.

In particular, the distance between the first A lens unit and the first B lens unit at the telephoto end with respect to the wide-angle end becomes smaller in Numerical Embodiments 1 and 2, does not change in Numerical Embodiment 3, and increases in Numerical Embodiment 4. Has become.

The aperture stop SP and the flare cut stop FC are moved together with the third lens unit during zooming.

In this embodiment, the first lens group and the first B lens group are treated as two lens groups. However, if the first A lens group and the first B lens group are treated as two lens groups, they are treated as five lens groups as a whole. Can also.

The zoom lens according to the present invention has the above-described basic structure. In the first aspect, the following order is from the object side: a first A lens group having a negative refractive power, a first B lens group having a negative refractive power, and a positive refractive power. The second lens group of power,
In a zoom lens having a third lens group having a negative refractive power and a fourth lens group having a positive refractive power, the distance between the first A lens group and the first B lens group at the telephoto end with respect to the wide angle end changes,
Alternatively, the lens is fixed such that the distance between the first B lens group and the second lens group is small, the distance between the second lens group and the third lens group is large, and the distance between the third lens group and the fourth lens group is small. The first A lens group and the first B lens group each have an aspherical surface, and one of these aspherical surfaces has a negative refractive power that increases as the distance from the optical axis increases. It is characterized in that it is a spherical surface and the other is an aspherical surface in which the negative refractive power becomes weaker as the distance from the optical axis increases.

By using an aspherical surface for the first and second lens groups A and B, spherical aberration, astigmatism, coma, and the like are corrected well. In particular, coma at the telephoto end can be favorably corrected.

In the second invention, focusing from an object at infinity to an object at a short distance is performed by the first method.
The B lens group is moved to the object side. At the wide angle end, the combined focal length of the first A lens group and the first B lens group when focusing on an object at infinity is f1AB, and the focal length of the entire system at the telephoto end. Where ft is ft, the following condition is satisfied: -0.6 <f1AB / ft <-0.45 (1)

If the combined focal length of the first-A lens unit L1A and the first-B lens unit L1B becomes smaller than the upper limit value of the conditional expression (1), it is advantageous for downsizing of the lens outer diameter. Coma aberration worsens. On the other hand, when the value exceeds the lower limit, coma is easily corrected, but it is disadvantageous for downsizing, and the outer diameter of the lens increases.

In the sectional view of the lens, the arrow F indicates the first B lens unit L when focusing from an object at infinity to an object at a close distance.
1B shows a trajectory for moving 1B to the object side.

As described above, focusing from an object at infinity to an object at a close distance is performed by focusing the first B lens unit L1B in the first unit L1.
Adopts the inner focus method, which moves the lens toward the object side, to obtain good optical performance over the entire object distance, and to minimize the external pressure and to optimize the lens weight and focus shift amount of the focus lens group for the focus drive torque. It has gained.

The value range of conditional expression (1) is more preferably -0.6 <f1AB / ft <-0.47 (1a).

In the third invention, the combined focal length of the first A lens unit and the first B lens unit when focusing on an object at infinity at the wide angle end is represented by f
When 1AB, the focal length of the entire system at the telephoto end is ft, and the F-number of the entire system at the telephoto end is FNOT, the condition of -1.8 <f1AB * FNOT / ft <-1.3 (2) is satisfied. It is characterized by satisfaction.

Conditional expression (2) is the combined focus of the first A lens group and the first B lens group when focusing on an object at infinity at the wide angle end with respect to the F-number FNOT at the telephoto end and the focal length ft at the telephoto end of the entire system. It specifies the distance,
If the combined focal length of the first-A lens unit L1A and the first-B lens unit L1B becomes smaller than the upper limit, it is advantageous for making the lens outer diameter compact, but the coma aberration particularly at the telephoto time becomes worse. On the other hand, when the value exceeds the lower limit, coma is easily corrected, but it is disadvantageous for downsizing, and the outer diameter of the lens increases.

It is more preferable that the numerical range of conditional expression (2) is -1.75 <f1AB * FNOT / ft <-1.4 (2a).

As described above, in the first, second, and third embodiments of the present invention, the lens group to which the aspherical surface is applied, the refractive power of each lens group, the moving condition of each lens group in zooming, and the like are described above. By appropriately setting the zoom lens as described above, a zoom lens having a wide angle of view, a high zoom ratio, a bright F-number, and high optical performance is obtained.

In the second invention, at the wide-angle end, the combined focal length of the first A lens group and the first B lens group when focusing on an object at infinity is f1AB, the focal length of the entire system at the telephoto end is ft, Assuming that the F number of the entire system at the telephoto end is FNOT, it is more preferable to satisfy the following condition: -1.8 <f1AB * FNOT / ft <-1.3 (2)

Here, the technical meaning of conditional expression (2) is the same as described above.

In the third aspect of the present invention, it is more preferable to perform focusing from an object at infinity to an object at a short distance by moving the first B lens unit to the object side.

The advantage of adopting the inner focus method is the same as that described in the first invention.

Hereinafter, the first, second and third inventions are collectively referred to as the present invention.

The zoom lens according to the present invention achieves the initial object by the above-described configuration, but is improved over the entire zoom range and the entire object distance while further widening the angle of view, increasing the aperture, and increasing the zoom ratio. To obtain optical performance, it is preferable to satisfy at least one of the following conditions.

When the combined focal length of the fourth lens group is f4, the focal length of the entire system at the wide-angle end is fw, and the F number of the entire system at the telephoto end is FNOT: 0.65 <f4 / (fw * FNOT) <0.95 (3) The following condition must be satisfied.

Conditional expression (3) defines the focal length of the fourth lens unit with respect to the F-number FNOT at the wide-angle end and the focal length fw at the wide-angle end of the entire system. When the focal length becomes long, it becomes easy to correct coma aberration at the time of telephoto, but the stroke for zooming becomes large, and the overall length increases. If the lower limit is exceeded, it is advantageous for making the lens compact, but it becomes difficult to correct aberrations.

It is more preferable that the numerical value range of the conditional expression (3) is 0.66 <f4 / (fw * FNOT) <0.9 (3a).

The fourth lens has three or more positive lenses and one or more negative lenses.

At this time, if anomalous dispersion glass is used as the material of the positive lens, chromatic aberration can be removed satisfactorily.

◎ 1A lens group, 1B lens group, 2nd lens group
Any one of the lens group, the third lens group, and the fourth lens group has one or more aspheric surfaces.

This is effective in correcting spherical aberration, astigmatism, coma, and the like.

The first A lens group and the first B lens group each have at least one aspherical surface.

According to this, the coma generated on the telephoto side can be corrected well. In particular, by appropriately using an aspherical lens, a zoom lens having high optical performance in which aberration is satisfactorily corrected despite a wide angle of view and a bright F number is achieved.

The first A lens group has an aspheric surface whose negative refractive power becomes weaker as the distance from the optical axis increases.
The lens group has an aspheric surface in which the negative refractive power increases as the distance from the optical axis increases.

According to this, coma at the wide-angle end and near the telephoto end can be corrected well.

When zooming from the wide-angle end to the telephoto end, the second
That is, the lens group and the fourth lens group move integrally to the object side.

This is preferable because the mechanical structure is simplified.

◎ A flare cut stop is provided between the third lens unit and the fourth lens unit.

According to this, even during zooming, it is possible to maintain a constant F-number over the entire zoom range, and it is possible to ensure good optical performance for harmful light at the periphery of the screen.

The following are numerical examples of the present invention. In each numerical example, i indicates the order of the surface from the object side and ri
Is the radius of curvature of the i-th surface from the object side, di is the i-th and i + 1-th lens thickness or air gap from the object side,
ni and vi are the refractive index and Abbe number of the material of the i-th optical member. Here, f, Fno, and 2ω represent the focal length, F number, and angle of view of the entire system when focusing on an object at infinity, respectively.

The aspheric surface has an X-axis in the optical axis direction, an H-axis in a direction perpendicular to the optical axis, a positive traveling direction of light, R is a paraxial radius of curvature,
When a, b, c, d, and e are aspheric coefficients

[0078]

(Equation 1)

This is represented by the following equation.

For example, the display of “eZ” is “1”.
0- ^z ".

Table 1 shows the relationship between the above-mentioned conditional expressions and various numerical values in the numerical examples.

[0082]

[Outside 1]

[0083]

[Outside 2]

[0084]

[Outside 3]

[0085]

[Outside 4]

[0086]

[Table 1]

Next, an embodiment of a single-lens reflex camera system using the zoom lens of the present invention will be described with reference to FIG. In FIG. 14, reference numeral 10 denotes a single-lens reflex camera body, 1
1 is a photographing optical system equipped with a zoom lens according to the present invention,
Reference numeral 12 denotes recording means such as a film or an image sensor for recording a subject image obtained through the photographing optical system 11, reference numeral 13 denotes a finder optical system for observing the subject image from the photographing optical system,
Reference numeral 4 denotes a rotating quick return mirror for switching and transmitting the subject image from the photographing optical system to the recording means 12 and the finder optical system 13. When observing the subject image with the viewfinder, the subject image formed on the focus plate 15 via the quick return mirror 14 is turned into an erect image by the pentaprism 16, and then enlarged and observed by the eyepiece optical system 17. At the time of photographing, the quick return mirror 14 rotates in the direction of the arrow, and the subject image is formed on the recording means 12 and recorded.

As described above, by applying the photographing optical system of the present invention to an optical apparatus such as a single-lens reflex camera interchangeable lens,
An optical device having high optical performance can be realized.

[0089]

According to the present invention, it is possible to achieve a zoom lens having a wide angle of view and high optical performance over the entire zoom range, and an optical apparatus using the same.

In addition, according to the present invention, while adopting the inner focus method, a wide angle of view, a large aperture and a high zoom ratio are achieved, and fluctuations of various aberrations accompanying zooming and focusing are reduced. A zoom lens having high optical performance over the zooming range and the entire focus range and an optical device using the same can be achieved.

In addition to the above, according to the present invention, a negative lead type lens configuration is used, the photographic field angle at the wide angle end is 84 °, the zoom ratio is 2.9, and the F-number is 2.9 in the entire zoom range.
A zoom lens having high brightness and high optical performance in the entire zoom range and an optical device using the same can be achieved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a zoom lens according to a numerical example 1 at a wide-angle end.

FIG. 2 is an aberration diagram at a wide-angle end of a zoom lens according to Numerical Example 1.

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

FIG. 4 is an aberration diagram at a telephoto end of a zoom lens according to Numerical Example 1.

FIG. 5 is a sectional view of a zoom lens according to a second numerical example at a wide-angle end.

FIG. 6 is an aberration diagram at a wide-angle end of a zoom lens according to Numerical Example 2.

FIG. 7 is an aberration diagram at a middle zoom position of the zoom lens according to Numerical Example 2.

8 is an aberration diagram at a telephoto end of a zoom lens according to Numerical Example 2. FIG.

FIG. 9 is a sectional view of a zoom lens according to a third numerical example at a wide-angle end.

FIG. 10 is an aberration diagram at a wide-angle end of a zoom lens according to Numerical Example 3.

FIG. 11 is an aberration diagram at a middle zoom position of the zoom lens according to Numerical Example 3.

FIG. 12 is an aberration diagram at a telephoto end of a zoom lens according to Numerical Example 3.

FIG. 13 is a sectional view of a main part of the optical apparatus of the present invention.

[Explanation of symbols]

 L1 1st lens group L1A 1A lens group L1B 1B lens group L2 2nd lens group L3 3rd lens group L4 4th lens group S Sagittal image plane M Meridional image plane d d-line g g-line

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H087 KA02 KA03 MA13 MA18 PA12 PA19 PB15 QA02 QA06 QA07 QA17 QA22 QA25 QA37 QA39 QA41 QA45 RA05 RA12 RA13 RA31 RA36 SA24 SA26 SA30 SA32 SA44 SA47 SA49 SA53 SA55 SA65 SA66 SB04 SB13 SB16 SB24 SB26 SB34 SB35 SB45

Claims (13)

[Claims] A first lens unit having a negative refractive power; a first lens unit having a negative refractive power; a second lens unit having a positive refractive power; a third lens unit having a negative refractive power; In a zoom lens having a fourth lens group having a positive refractive power, the distance between the first A lens group and the first B lens group at the telephoto end with respect to the wide-angle end changes or is fixed, and the first B lens group and the Zooming is performed by moving the lens groups so that the distance between the two lens groups is small, the distance between the second lens group and the third lens group is large, and the distance between the third lens group and the fourth lens group is small. The first A lens group and the first B lens group each have an aspheric surface,
A zoom lens characterized in that one of these aspherical surfaces is an aspherical surface whose negative refractive power increases as the distance from the optical axis increases, and the other is an aspherical surface whose negative refractive power decreases as the distance from the optical axis increases. . 2. In order from the object side, a first A lens group having a negative refractive power, a first B lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a negative refractive power, In a zoom lens having a fourth lens group having a positive refractive power, the distance between the first A lens group and the first B lens group at the telephoto end with respect to the wide-angle end changes or is fixed, and the first B lens group and the Zooming is performed by moving the lens groups so that the distance between the two lens groups is small, the distance between the second lens group and the third lens group is large, and the distance between the third lens group and the fourth lens group is small. Focusing from a distant object to a close object is performed by moving the first B lens group to the object side, and at the wide-angle end, the combined focal length of the first A lens group and the first B lens group when focusing on an object at infinity. Is f1AB, and the focal length of the entire system at the telephoto end is When ft is satisfied, the zoom lens satisfies the following condition: -0.6 <f1AB / ft <-0.45 (1) 3. In order from the object side, a first A lens group having a negative refractive power, a first B lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a negative refractive power, In a zoom lens having a fourth lens group having a positive refractive power, the distance between the first A lens group and the first B lens group at the telephoto end with respect to the wide-angle end changes or is fixed, and the first B lens group and the Zooming is performed by moving the lens groups so that the distance between the two lens groups is small, the distance between the second lens group and the third lens group is large, and the distance between the third lens group and the fourth lens group is small. The combined focal length of the 1A lens group and the 1B lens group is f1
AB, when the focal length of the entire system at the telephoto end is ft, and the F number of the entire system at the telephoto end is FNOT, the following condition is satisfied: -1.8 <f1AB * FNOT / ft <-1.3 (2) A zoom lens characterized by satisfaction. 4. At the wide-angle end, the combined focal length of the first A lens group and the first B lens group when focusing on an object at infinity is f1AB, the focal length of the entire system at the telephoto end is ft, and the total focal length at the telephoto end is ft. The zoom lens according to claim 2, wherein when the F number of the system is FNOT, the following condition is satisfied: -1.8 <f1AB * FNOT / ft <-1.3 (2). 5. The zoom lens according to claim 3, wherein focusing from an object at infinity to an object at a short distance is performed by moving the first B lens group to the object side. 6. When the combined focal length of the fourth lens unit is f4, the focal length of the entire system at the wide-angle end is fw, and the F number of the entire system at the telephoto end is FNOT, 0.65 <f4 / (fw * FNOT). The zoom lens according to any one of claims 1 to 5, wherein the following condition is satisfied. 7. The fourth lens according to claim 1, wherein the fourth lens has at least three positive lenses and at least one negative lens.
Or the zoom lens according to 3. 8. The first A lens group, the first B lens group, and the second
6. The zoom lens according to claim 2, wherein one of the lens group, the third lens group, and the fourth lens group has one or more aspheric surfaces. 9. The zoom lens according to claim 2, wherein each of the first A lens group and the first B lens group has one or more aspherical surfaces. 10. The first A lens group has an aspheric surface whose negative refractive power decreases as the distance from the optical axis increases, and the first B lens group has an aspheric surface whose negative refractive power increases as the distance from the optical axis increases. The zoom lens according to claim 1, further comprising: a zoom lens. 11. The zoom lens system according to claim 1, wherein at the time of zooming from the wide-angle end to the telephoto end, the second lens unit and the fourth lens unit move integrally to the object side. A zoom lens according to claim 1. 12. The zoom lens according to claim 1, further comprising a flare cut stop between the third lens group and the fourth lens group. 13. An optical apparatus comprising the zoom lens according to claim 1. Description: