JP2001117004A - Zoom lens and video camera using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a compact zoom lens which is constituted of small number of lenses and has the angle of view >=62 deg. and where aberration including chromatic aberration are excellently corrected. SOLUTION: This zoom lens is constituted of a 1st lens group 11 having positive refractive power and fixed with respect to an image surface, a 2nd lens group 12 having negative refractive power and performing variable power action by moving on an optical axis, a diaphragm 15 fixed with respect to the image surface, a 3rd lens group 13 having positive refractive power, and a 4th lens group 14 having positive refractive power and moving on the optical axis so that the image surface fluctuated by the movement of the 2nd lens group 12 and an object may be kept at a fixed position from a reference surface, which are arranged in order from the object side to the image surface side. The 2nd lens group 12 is constituted of two negative lenses and one positive lens. The 3rd lens group 13 is constituted of two positive lenses and one negative lens. The 4th lens group 14 is constituted of a positive lens. The 2nd to the 4th lens groups 12 to 14 respectively include at least one aspherical surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens and a video camera using the same. More specifically,
The present invention relates to a compact aspherical zoom lens having a field angle at a wide angle end of 62 degrees or more and having a camera shake correction function, and a video camera using the same.

[0002]

2. Description of the Related Art In recent consumer video cameras,
With the spread of the DV format, it is essential to achieve both miniaturization and high image quality. Accordingly, there is a strong demand for a wide-angle zoom lens having a high optical quality, a short overall optical length, and a large angle of view.

For example, Japanese Patent Application Laid-Open No. 9-281392 discloses a zoom lens having high image quality, an angle of view at the wide angle end of 59.2 to 60.7 degrees, and a zoom ratio of about 10 times. ing.

[0004]

SUMMARY OF THE INVENTION However, Japanese Patent Application Laid-Open No. Hei 9-2
The zoom lens disclosed in JP 813922 realizes miniaturization and high image quality with a small lens configuration of ten lenses, but the angle of view at the wide angle end is about 61 degrees or less.

In order to realize a larger angle of view while maintaining high image quality, it is necessary to use ten or more lenses or to increase the total optical length. There was a problem that it was not possible.

The present invention has been made to solve the above-mentioned problems in the prior art, and provides a zoom lens having a small lens structure, an angle of view of 62 degrees or more, and a camera shake correction function. In addition, another object of the present invention is to provide a small and high-quality video camera using the zoom lens.

[0007]

In order to achieve the above-mentioned object, a zoom lens according to the present invention has a positive refractive power, which is arranged in order from an object side to an image plane side, and has an image plane. And a second lens group having a negative refractive power and performing a zooming action by moving on the optical axis.
A lens group, an aperture fixed with respect to the image plane, a third lens group having a positive refractive power, and an image plane having a positive refractive power and varying with the movement of the second lens group and the object. A fourth lens group that moves on the optical axis so as to be kept at a fixed position from a reference plane, wherein the second lens group is composed of two negative lenses and one positive lens. The third lens group includes three lenses, two positive lenses and one negative lens, and includes at least one aspheric surface. And wherein the fourth lens group comprises a positive lens including at least one aspheric surface. According to the configuration of this zoom lens, the third lens group includes three lenses, two positive lenses and one negative lens, so that the third lens group is small and has a small spherical aberration from the wide-angle end to the standard position. A well-corrected zoom lens is realized. In addition, at least one aspherical surface is arranged in each of the second to fourth lens units having a small lens diameter, and an optimal aspherical shape and lens type are adopted, so that a lens configuration of less than 62 degrees can be achieved with a small lens configuration. A small zoom lens having an angle of view and excellently correcting various aberrations including chromatic aberration can be realized. Further, since the lenses constituting the second to fourth lens groups all have small lens diameters, the aspheric lenses included in these lens groups can be easily manufactured.

In the above-described zoom lens system according to the present invention, the second lens group includes three lenses: a negative lens arranged in order from the object side, and a cemented lens of the negative lens and the positive lens. preferable.

In the zoom lens according to the present invention, it is preferable that the second lens group includes a negative lens, a negative lens, and a positive lens arranged in order from the object side.

In the zoom lens according to the present invention, the third lens group includes three lenses, a positive lens and a cemented lens of a positive lens and a negative lens, which are arranged in order from the object side. preferable.

In the zoom lens according to the present invention, it is preferable that the third lens group includes a positive lens, a positive lens, and a negative lens arranged in order from the object side.

In the configuration of the zoom lens of the present invention, when the focal length of the second lens unit is f2 and the focal length of the entire system at the wide-angle end is fw, the following conditional expression (1) is satisfied. Is preferred.

1.0 <| f2 | / fw <2.0 (1) According to this preferred example, the field curvature can be corrected to be small despite the wide angle, and the size is small. It is possible to realize a zoom lens that can be realized.

In the zoom lens according to the present invention, the second lens group includes a first negative lens, a second negative lens, and a positive lens arranged in order from the object side. When the object-side surface of the second negative lens is an aspheric surface, the local radius of curvature near the optical axis is R10, and the local radius of curvature of the outer peripheral portion is R11, the following conditional expression (2) is satisfied. It is preferable to satisfy.

0.8 <| R11 | / | R10 | <3.0 (2) According to this preferred example, it is possible to satisfactorily correct coma aberration on the wide angle side and spherical aberration on the telephoto side. it can.

In the configuration of the zoom lens of the present invention, when the focal length of the third lens unit is f3 and the focal length of the entire system at the wide-angle end is fw, the following conditional expression (3) is satisfied. Is preferred.

2.5 <f3 / fw <4.0 (3) According to this preferred example, a back focus in which a crystal filter, an IR cut filter, or the like can be inserted can be secured, and Thus, a zoom lens that can be reduced in size can be realized.

In the zoom lens of the present invention, the object-side surface of the lens closest to the object side in the third lens group is an aspheric surface, and the local radius of curvature near the optical axis is R20. When the local radius of curvature of the outer peripheral portion is R21, it is preferable that the following conditional expression (4) is satisfied.

1.1 <R21 / R20 <2.0 (4) According to this preferred example, it is possible to realize a zoom lens in which spherical aberration over the entire zoom range is satisfactorily corrected.

In the above-described zoom lens according to the present invention, when the absolute value of the radius of curvature of the image side surface of the concave lens included in the third lens group is R30 and the focal length of the third lens group is f3, It is preferable to satisfy the following conditional expression (5).

0.35 <R30 / f3 <0.6 (5) According to this preferred example, a zoom lens in which the coma of the light beam outside the principal ray of the off-axis light is satisfactorily corrected is provided. Can be realized.

In the configuration of the zoom lens according to the present invention, when the focal length of the fourth lens group is f4 and the focal length of the entire system at the wide-angle end is fw, the following conditional expression (6) is satisfied. Is preferred.

2.4 <f4 / fw <3.0 (6) According to this preferred example, it is possible to secure a back focus in which a crystal filter, an IR cut filter, or the like can be inserted, and Thus, a zoom lens that can be reduced in size can be realized.

In the zoom lens according to the present invention, the surface of the fourth lens group on the object side is aspheric, the local radius of curvature near the optical axis is R40, and the local radius of curvature of the outer peripheral portion is R40. When the radius is R41, the following conditional expression (7)
Is preferably satisfied.

1.3 <R41 / R40 <1.6 (7) According to this preferable example, the zoom lens in which the coma of the light flux inside the principal ray of the off-axis light is favorably corrected is provided. Can be realized.

In the zoom lens system according to the present invention, the stop diameter of the stop provided on the object side of the third lens unit and fixed to the image plane decreases as the focal length of the entire system increases. When the stop diameter at the telephoto end is St and the stop diameter at the wide-angle end is Sw, it is preferable that the following conditional expression (8) is satisfied.

St / Sw <0.92 (8) According to this preferred example, deterioration of aberration at the long focal length side, particularly at the telephoto end, can be reduced.

In general, the deterioration of the optical performance of the zoom lens during zooming can be reduced by adjusting the aberration performance of each lens unit. That is, compared to the type in which some lenses inside the lens group are moved perpendicularly to the optical axis, by moving the entire lens group in which the optical performance is united, a camera shake correction function with less deterioration of aberration is provided. A zoom lens can be realized. In this case, when the amount of movement of the third lens group at the focal length f of the entire system at the time of camera shake correction is Y, the amount of movement of the third lens group at the telephoto end is Yt, and the focal length at the telephoto end is ft. It is preferable to satisfy the following conditional expressions (9) and (10).

Yt> Y (9) (Y / Yt) / (f / ft) <1.5 (10) According to this preferable example, camera shake correction with less deterioration in optical performance can be performed. Can be realized.

Further, a zoom lens according to the present invention is a video camera provided with a zoom lens, wherein the zoom lens according to the present invention is used as the zoom lens. According to the configuration of this video camera,
A small and wide-angle video camera can be realized.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described more specifically with reference to embodiments.

<First Embodiment> FIG. 1 shows a first embodiment of the present invention.
FIG. 3 is a layout diagram showing a configuration of a zoom lens according to the embodiment.

As shown in FIG. 1, first from the object side (the left side in FIG. 1) to the image plane 17 side (the right side in FIG. 1).
A lens group 11, a second lens group 12, an aperture 15, a third lens group 13, a fourth lens group 14, a flat plate 16 equivalent to an optical low-pass filter and a face plate of a CCD are arranged in this order. It is configured.

The first lens group 11 has a positive refractive power,
It is fixed with respect to the image plane 17 at the time of zooming and at the time of focusing. The second lens group 12 includes three lenses, a first negative lens and a cemented lens of a second negative lens and a positive lens, which are arranged in order from the object side, and has a negative refractive power as a whole. In addition, a zooming effect is performed by moving the optical axis. The third lens group 13 is composed of three lenses, a positive lens arranged in order from the object side and a cemented lens of a positive lens and a negative lens. It is in a fixed state. The fourth lens group 14 is composed of one positive lens. The fourth lens group 14 is moved along the optical axis so as to keep the image plane, which fluctuates due to the movement of the second lens group 12 and the object, at a fixed position from the reference plane. The movement of the image by the magnification and the focus adjustment are performed simultaneously.

When the focal length of the second lens group 12 is f2 and the focal length of the entire system at the wide-angle end is fw, it is desirable that the following conditional expression (1) is satisfied.

1.0 <| f2 | / fw <2.0 (1) The conditional expression (1) is an expression relating to the power of the second lens group 12. When | f2 | / fw becomes 1.0 or less, it becomes difficult to correct the field curvature. | F2 | /
When fw becomes 2.0 or more, the second
Since the movement amount of the lens group 12 is large, the overall length is long, and it is difficult to realize a small zoom lens.

The second lens group 12 is composed of three lenses, a first negative lens arranged in order from the object side, and a cemented lens of a second negative lens and a positive lens. When the object-side surface of the negative lens is an aspheric surface, and the local radius of curvature near the optical axis is R10 and the local radius of curvature at the outer peripheral portion is R11, the following conditional expression (2) is satisfied. desirable.

0.8 <| R11 | / | R10 | <3.0 (2) When | R11 | / | R10 | is equal to or greater than 3.0, on the wide-angle side, it is larger than the principal ray of off-axis light. The coma aberration of the outer ray is largely generated, and the spherical aberration is insufficiently corrected on the telephoto side. ｜ R
When 11 | / | R10 | is 0.8 or less, the spherical aberration particularly on the telephoto side becomes overcorrected, and it becomes difficult to obtain good aberration correction.

The focal length of the third lens group 13 is represented by f
3. When the focal length of the entire system at the wide-angle end is fw,
It is desirable to satisfy the following conditional expressions (3).

2.5 <f3 / fw <4.0 (3) The conditional expression (3) is an expression relating to the power of the third lens group 13. When f3 / fw is 2.5 or less, it becomes difficult to secure a back focus in which a crystal filter, an IR cut filter, or the like can be inserted.
Further, when f3 / fw is 4.0 or more, the total length becomes long, and it is difficult to realize a small-sized zoom lens.

The third lens group 13 includes two positive lenses and one
It is desirable to have three negative lenses. With this lens configuration, it is possible to realize a zoom lens that is small in size and in which spherical aberration from the wide-angle end to the standard position is well corrected.

Further, the object-side surface of the lens disposed closest to the object side of the third lens group 13 is an aspheric surface, the local radius of curvature near the optical axis is R20, and the local radius of curvature of the outer peripheral portion is R21. In this case, it is preferable to satisfy the following conditional expression (4).

1.1 <R21 / R20 <2.0 (4) The above-mentioned conditional expression (4) satisfies the aspheric surface of the object-side surface of the lens closest to the object side in the third lens group 13. And defines a range in which the spherical aberration is satisfactorily corrected. When R21 / R20 is 1.1 or less, negative spherical aberration occurs, and when R21 / R20 exceeds 2.0, overcorrection occurs and positive spherical aberration occurs.

Further, when the absolute value of the radius of curvature of the image side surface of the concave lens included in the third lens group 13 is R30, and the focal length of the third lens group 13 is f3, the following conditional expression (5) is satisfied.
It is desirable to satisfy

0.35 <R30 / f3 <0.6 (5) The conditional expression (5) defines a range in which the coma of the light beam outside the principal ray of the off-axis light is favorably corrected. It is specified. When R30 / f3 is 0.6 or more, an inward frame occurs at the zooming intermediate position, and R30 / f3 is set to 0.1.
When it is less than 35, outward frames are generated.

The focal length of the fourth lens group 14 is represented by f
4. When the focal length of the entire system at the wide-angle end is fw,
It is desirable to satisfy the following conditional expressions (6).

2.4 <f4 / fw <3.0 (6) The conditional expression (6) is an expression relating to the power of the fourth lens group 14. If f4 / fw is 2.4 or less, it becomes difficult to secure a back focus for inserting a crystal filter, an IR cut filter, and the like. Also, f4 /
When fw becomes 3.0 or more, the fourth time during focusing
The amount of movement of the lens group 14 becomes large, and it is difficult to realize a small zoom lens.

The object-side surface of the lens of the fourth lens group 14 is aspheric, and the local radius of curvature near the optical axis is R4.
0, when the local radius of curvature of the outer peripheral portion is R41, it is preferable that the following conditional expression (7) is satisfied.

1.3 <R41 / R40 <1.6 (7) The conditional expression (7) is an expression relating to the aspherical surface of the object-side surface of the lens of the fourth lens unit 14, and is off-axis. This defines a range in which the coma of the light beam inside the principal ray of the light is favorably corrected. When R41 / R40 is 1.3 or less, an inward frame is generated, and when R41 / R40 is 1.6 or more, an outward frame is generated.

Also, the aperture diameter of the aperture stop 15 provided on the object side of the third lens group 13 and fixed to the image plane 17 decreases as the focal length of the entire system increases, and the aperture diameter at the telephoto end decreases. When St and the aperture diameter at the wide-angle end are Sw, it is desirable to satisfy the following conditional expression (8).

St / Sw <0.92 (8) When St / Sw is 0.92 or more, the deterioration of aberration at the long focal length side, particularly at the telephoto end, increases.

It is desirable that the entire third lens group 13 be moved perpendicular to the optical axis to correct the image fluctuation due to camera shake. By doing so, it is possible to reduce deterioration of chromatic aberration during correction.

The amount of movement of the third lens group 13 (correction lens) at the focal length f of the entire system at the time of camera shake correction is represented by Y,
Assuming that the amount of movement of the third lens group 13 at the telephoto end is Yt and the focal length at the telephoto end is ft, the following conditional expression (9):
It is desirable to satisfy (10).

Yt> Y (9) (Y / Yt) / (f / ft) <1.5 (10) The conditional expressions (9) and (10) satisfy the third lens group 13. Is an expression relating to the amount of movement of. In the case of a zoom lens, when the correction angle is constant over the entire zoom range, the larger the zoom ratio, the larger the amount of movement of the third lens group 13, and conversely, the smaller the zoom ratio, the smaller the amount of movement of the third lens group 13. . If Yt becomes Y or less and (Y / Yt) / (f / ft) becomes 1.5 or more, the correction becomes excessive, and the deterioration of the optical performance including monochromatic aberration increases.

<Second Embodiment> FIG. 2 shows a second embodiment of the present invention.
FIG. 3 is a layout diagram showing a configuration of a zoom lens according to the embodiment.

As shown in FIG. 2, first from the object side (the left side in FIG. 2) to the image plane 27 side (the right side in FIG. 2).
A lens group 21, a second lens group 22, an aperture 25, a third lens group 23, a fourth lens group 24, an optical low-pass filter and a flat plate 26 equivalent to a face plate of a CCD are arranged in this order. It is composed.

The first lens group 21 has a positive refractive power,
It is fixed with respect to the image plane 27 during zooming and during focusing. The second lens group 22 includes three lenses, a first negative lens arranged in order from the object side and a cemented lens of the second negative lens and the positive lens, and has a negative refractive power as a whole. In addition, a zooming effect is performed by moving the optical axis. The third lens group 23 includes three lenses, a positive lens, a positive lens, and a negative lens, which are arranged in order from the object side, and is fixed to the image plane 27 during zooming and focusing. is there. Fourth lens group 24
Is composed of one positive lens, and moves on the optical axis to keep the image plane, which fluctuates due to the movement of the second lens group 12 and the object, at a fixed position from the reference plane, thereby moving the image by zooming. And focus adjustment are performed simultaneously.

Also in the zoom lens of the present embodiment,
Similarly to the first embodiment, the conditional expressions (1) to (1)
It is desirable to satisfy (10).

<Third Embodiment> FIG. 3 shows a third embodiment of the present invention.
FIG. 3 is a layout diagram showing a configuration of a zoom lens according to the embodiment.

As shown in FIG. 3, first from the object side (the left side in FIG. 3) to the image plane 37 side (the right side in FIG. 3).
A lens group 31, a second lens group 32, a diaphragm 35, a third lens group 33, a fourth lens group 34, a flat plate 36 equivalent to an optical low-pass filter and a face plate of a CCD are arranged in this order. It is composed.

The first lens group 31 has a positive refractive power.
It is fixed with respect to the image plane 37 at the time of zooming and at the time of focusing. The second lens group 32 includes three lenses of a first negative lens, a second negative lens, and a positive lens arranged in order from the object side, has a negative refractive power as a whole, and moves along the optical axis. By doing so, the zooming action is performed. The third lens group 33 includes three lenses, a positive lens and a cemented lens of a negative lens and a positive lens, arranged in order from the object side.
7 is fixed. Fourth lens group 34
Is composed of one positive lens, and moves on the optical axis to keep the image plane, which fluctuates due to the movement of the second lens group 12 and the object, at a fixed position from the reference plane, thereby moving the image by zooming. And focus adjustment are performed simultaneously.

Also in the zoom lens of the present embodiment,
As in the first and second embodiments, it is desirable to satisfy the conditional expressions (1) to (10).

<Fourth Embodiment> FIG. 4 shows a fourth embodiment of the present invention.
FIG. 3 is a layout diagram showing a configuration of a zoom lens having a camera shake correction function according to the embodiment.

As shown in FIG. 4, first from the object side (the left side in FIG. 4) to the image plane 47 side (the right side in FIG. 4).
A lens group 41, a second lens group 42, an aperture 45, a third lens group 43, a fourth lens group 44, a flat plate 46 equivalent to an optical low-pass filter and a face plate of a CCD are arranged in this order. It is composed. Further, a detector 48 for detecting a camera shake amount, a driving device 49 for moving the third lens group 43 in two directions perpendicular to the optical axis based on a signal from the detector 48, and a driving device 4
9 for driving the driving circuit 9. Here, as the zoom lens, the zoom lens according to the first to third embodiments is used. With the above configuration, a zoom lens having a small and highly accurate camera shake correction function is realized.

<Fifth Embodiment> FIG. 5 shows a fifth embodiment of the present invention.
FIG. 3 is a layout diagram showing a configuration of a video camera according to the embodiment.

As shown in FIG. 5, a video camera according to the present embodiment has a zoom lens 51 and an image sensor 52.
And a signal processing circuit 53. Here, as the zoom lens 51, the zoom lens according to the first to fourth embodiments is used, thereby realizing a small-sized and wide-angle video camera.

[0067]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to specific examples.

(Example 1) Table 1 below shows specific examples of the zoom lens according to the first embodiment.

[0069]

[Table 1]

In Table 1 above, r (mm) is the radius of curvature of the lens, d (mm) is the thickness of the lens or the air gap of the lens, n is the refractive index of each lens with respect to the d-line, and ν is each lens. (The same applies to the following Examples 2 to 5).

The aspheric shape is defined by the following (Equation 1) (the same applies to the following Examples 2 to 5).

[0072]

(Equation 1)

In the above (Equation 1), H is the height from the optical axis, SAG is the distance from the aspherical vertex of the point on the aspherical surface whose height is H from the optical axis, and R is the aspherical vertex. , K represents a conical constant, and D and E represent aspheric coefficients.

The following Table 2 shows the aspherical shape of the zoom lens according to the present embodiment.

[0075]

[Table 2]

Table 3 below shows the air gap (mm) that can be changed by zooming when the object point is at a position 2 m from the front end of the lens. Also, in Table 3 below,
The aperture diameter changes with the focal length. The standard positions in the following (Table 3) are the third lens group 13 and the fourth lens group 1.
4 is the closest position. In the following (Table 3), f (m
m), F / NO, and ω (゜) are the focal length at the wide-angle end, the standard position, and the telephoto end of the zoom lens in Table 1 above, and F
Number and half angle of incidence.

[0077]

[Table 3]

As can be seen from Table 3 above, the angle of view at the wide-angle end in this embodiment is about 64 degrees.

In the zoom lens of this embodiment, when the focal length of the second lens group 12 is f2 and the focal length of the entire system at the wide-angle end is fw, | f2 | / fw is a value shown in the following Table 4. have.

That is, a compact zoom lens that satisfies the above conditional expression (1) and has a small field curvature corrected in spite of a wide angle is realized.

The zoom lens in this embodiment is
The second lens group 12 includes three lenses, a first negative lens arranged in order from the object side, and a cemented lens of the second negative lens and the positive lens, and the second negative lens has an object side. Is an aspherical surface, and when the local radius of curvature near the optical axis is R10 and the local radius of curvature of the outer peripheral portion is R11, | R11 | / | R10 | is a value shown in the following (Table 4). have.

That is, the above-mentioned conditional expression (2) is satisfied, and excellent correction of coma on the wide-angle side and spherical aberration on the telephoto side is realized.

The zoom lens in this embodiment is
Assuming that the focal length of the third lens group 13 is f3 and the focal length of the entire system at the wide-angle end is fw, f3 / fw has the value shown in the following (Table 4).

That is, the above-mentioned conditional expression (3) is satisfied, and a back focus in which a crystal filter, an IR cut filter or the like can be inserted is secured, and a small zoom lens is realized.

The zoom lens in this embodiment is
When the object-side surface of the lens closest to the object side of the third lens group 13 is an aspheric surface, the local radius of curvature near the optical axis is R20, and the local radius of curvature of the outer peripheral portion is R21.
R21 / R20 has the values shown in the following (Table 4).

That is, the zoom lens in which the conditional expression (4) is satisfied and the spherical aberration over the entire zoom range is satisfactorily corrected is realized.

The zoom lens in this embodiment is
Assuming that the radius of curvature of the image side surface of the concave lens included in the third lens group 13 is R30 and the focal length of the third lens group 13 is f3, R30 / f3 has the value shown in the following (Table 4).

That is, the zoom lens in which the conditional expression (5) is satisfied and the coma of the light beam outside the principal ray of the off-axis light is well corrected is realized.

The zoom lens in this embodiment is
Assuming that the focal length of the fourth lens group 14 is f4 and the focal length of the entire system at the wide-angle end is fw, f4 / fw has the value shown in the following (Table 4).

That is, the above-mentioned conditional expression (6) is satisfied, a back focus in which a crystal filter, an IR cut filter and the like can be inserted is secured, and a small zoom lens is realized.

The zoom lens in this embodiment is
When the object-side surface of the lens of the fourth lens group 14 is an aspheric surface, and the local radius of curvature near the optical axis is R40 and the local radius of curvature of the outer peripheral portion is R41, R41 / R40 is as follows (Table 4). ).

In other words, a zoom lens that satisfies the conditional expression (7) and satisfactorily corrects the coma of the light beam inside the principal ray of the off-axis light is realized.

The zoom lens in this embodiment is
As shown in the above (Table 3), the stop diameter of the stop 15 provided on the object side of the third lens group 13 and fixed to the image plane 17 decreases with an increase in the focal length of the entire system. When the stop diameter at the end is St and the stop diameter at the wide-angle end is Sw, St / Sw has the values shown in the following (Table 4).

That is, the above-mentioned conditional expression (8) is satisfied, and a zoom lens in which the aberration at the long focal length side, particularly at the telephoto end is favorably corrected is realized.

The zoom lens in this embodiment is
By moving the entire third lens group 13 perpendicularly to the optical axis, the fluctuation of the image at the time of camera shake is corrected, and the deterioration of the chromatic aberration at the time of correction is reduced.

The zoom lens in this embodiment is
The movement amount of the third lens group 13 (correction lens) at the focal length f of the entire system at the time of camera shake correction is set to Y, and the third lens unit at the telephoto end is set to Y.
The amount of movement of the lens group 13 is Yt, and the focal length at the telephoto end is ft.
, Y, Yt and (Y / Yt) / (f / ft)
Have the values shown in the following (Table 4).

That is, the above-mentioned conditional expressions (9) and (10) are satisfied, and a zoom lens with small deterioration of various aberrations at the time of correction is realized.

[0098]

[Table 4]

FIGS. 6 to 8 show aberration diagrams at the wide-angle end, the standard position, and the telephoto end of the zoom lens shown in Table 1 above. In each figure, (a) is a diagram of the spherical aberration with respect to the d-line. (B) is a diagram of astigmatism,
The solid line indicates sagittal field curvature, and the broken line indicates meridional field curvature. (C) is a diagram showing the distortion, (d) is a diagram of the axial chromatic aberration, the solid line is d line, the short dashed line is F
The line and the long dashed line indicate values for the C line. (E) is a diagram of chromatic aberration of magnification, where a short broken line indicates a value with respect to the F line, and a long broken line indicates a value with respect to the C line. The above description of (a) to (e) is the same for FIGS. 10 to 12, 14 to 16, 18 to 20, and 22 to 24.

FIG. 9 is a graph showing the aberration performance at the time of correcting the camera shake by 0.3 degree at the telephoto end. In FIG. 9, (f)
FIG. 7G is a diagram of the lateral aberration at a relative image height of 0.75, FIG. 7G is the center of the screen, and FIG. Short dashed line is F
The line and the solid line show the values for the d line, and the long broken lines show the values for the C line. The above description of (f) to (h) has been described with reference to FIGS.
The same applies to FIGS. 21 and 25.

As can be seen from FIGS. 6 to 9, the zoom lens according to this embodiment shows good aberration performance both at rest and at the time of camera shake correction.

(Example 2) The following (Table 5) shows another specific example of the zoom lens according to the first embodiment.

[0103]

[Table 5]

The following (Table 6) shows the aspherical shape of the zoom lens in this embodiment.

[0105]

[Table 6]

The following (Table 7) shows the variable air spacing (mm) by zooming when the object point is at a position 2 m from the lens tip. Also, in Table 7 below,
The aperture diameter changes with the focal length. The standard positions in the following (Table 7) are the third lens group 13 and the fourth lens group 1.
4 is the closest position. In the following (Table 7), f (m
m), F / NO, and ω (゜) are the focal length at the wide-angle end, the standard position, and the telephoto end of the zoom lens in Table 5 above, and F
Number and half angle of incidence.

[0107]

[Table 7]

As can be seen from the above (Table 7), the angle of view at the wide-angle end in this embodiment is about 65 degrees.

Table 8 below shows values such as | f2 | / fw for the zoom lens of this embodiment.

[0110]

[Table 8]

As shown in the above (Table 8), also in the zoom lens of this embodiment, the above-mentioned conditional expressions (1) to (10) are satisfied.

FIGS. 10 to 12 show aberration performance diagrams of the zoom lens shown in (Table 7) at the wide-angle end, the standard position, and the telephoto end. Further, FIG. 13 shows that 0.3 at the telephoto end.
FIG. 4 shows an aberration performance diagram at the time of correcting hand shake.

As can be seen from FIGS. 10 to 13, the zoom lens according to this embodiment shows good aberration performance both at rest and at the time of camera shake correction.

Example 3 The following (Table 9) shows still another specific example of the zoom lens according to the first embodiment.

[0115]

[Table 9]

The following (Table 10) shows the aspherical shape of the zoom lens in this embodiment.

[0117]

[Table 10]

The following (Table 11) shows the air gap (mm) that can be varied by zooming when the object point is at a position 2 m from the lens tip. The following (Table 11)
FIG. 7 shows the aperture diameter that changes with the focal length. The following (Table 1
The standard position in 1) is a position where the third lens group 13 and the fourth lens group 14 come closest to each other. The following (Table 11)
Medium, f (mm), F / NO, and ω (゜) are the above (Table 9)
Are the focal length, F-number, and half angle of view of the zoom lens at the wide angle end, the standard position, and the telephoto end.

[0119]

[Table 11]

As can be seen from the above (Table 11), the angle of view at the wide-angle end in this embodiment is about 63 degrees.

Table 12 below shows values such as | f2 | / fw for the zoom lens of this example.

[0122]

[Table 12]

As shown in the above (Table 12), also in the zoom lens of this embodiment, the conditional expressions (1) to (10) are satisfied.
Is satisfied.

FIGS. 14 to 16 show aberration performance diagrams of the zoom lens shown in (Table 11) at the wide-angle end, the standard position, and the telephoto end. Also, FIG.
The aberration performance figure at the time of 3 degree camera shake correction is shown.

As can be seen from FIGS. 14 to 17, the zoom lens according to this embodiment shows good aberration performance both at rest and at the time of camera shake correction.

(Example 4) The following (Table 13)
Specific examples of the zoom lens according to the embodiment will be described.

[0127]

[Table 13]

Table 14 below shows the aspherical shape of the zoom lens of this embodiment.

[0129]

[Table 14]

Table 15 below shows the variable air gap (mm) by zooming when the object point is at a position 2 m from the lens tip. The following (Table 15)
FIG. 7 shows the aperture diameter that changes with the focal length. The following (Table 1
The standard position in 5) is a position where the third lens group 23 and the fourth lens group 24 come closest to each other. The following (Table 15)
Medium, f (mm), F / NO, and ω (゜) are as shown in Table 1 above.
3) The focal length, F number, and half angle of view at the wide-angle end, standard position, and telephoto end of the zoom lens.

[0131]

[Table 15]

As can be seen from the above (Table 15), the angle of view at the wide-angle end in this embodiment is about 69 degrees.

Table 16 below shows values such as | f2 | / fw for the zoom lens of this embodiment.

[0134]

[Table 16]

As shown in the above (Table 16), also in the zoom lens of this embodiment, the conditional expressions (1) to (10) are satisfied.
Is satisfied.

FIGS. 18 to 20 show aberration performance diagrams of the zoom lens shown in (Table 15) at the wide-angle end, the standard position, and the telephoto end. Also, FIG.
The aberration performance figure at the time of 3 degree camera shake correction is shown.

As can be seen from FIGS. 18 to 21, the zoom lens according to this embodiment shows good aberration performance both at rest and at the time of camera shake correction.

Example 5 The following (Table 17) shows that
Specific examples of the zoom lens according to the embodiment will be described.

[0139]

[Table 17]

Table 18 below shows the aspherical shape of the zoom lens of this embodiment.

[0141]

[Table 18]

The following (Table 19) shows the air gap (mm) that can be changed by zooming when the object point is at a position 2 m measured from the front end of the lens. The following (Table 19)
FIG. 7 shows the aperture diameter that changes with the focal length. The following (Table 1
The standard position in 9) is a position where the third lens group 33 and the fourth lens group 34 come closest to each other. Following (Table 19)
Medium, f (mm), F / NO, and ω (゜) are as shown in Table 1 above.
3) The focal length, F number, and half angle of view at the wide-angle end, standard position, and telephoto end of the zoom lens.

[0143]

[Table 19]

As can be seen from the above (Table 19), the angle of view at the wide-angle end in this embodiment is about 73 degrees.

Table 20 below shows values such as | f2 | / fw for the zoom lens of this embodiment.

[0146]

[Table 20]

As shown in the above (Table 20), also in the zoom lens of this embodiment, the conditional expressions (1) to (10) are satisfied.
Is satisfied.

FIGS. 22 to 24 show aberration diagrams at the wide-angle end, the standard position, and the telephoto end of the zoom lens shown in Table 19 above. Further, FIG.
The aberration performance figure at the time of 3 degree camera shake correction is shown.

As can be seen from FIGS. 22 to 25, the zoom lens according to the present embodiment shows good aberration performance both at rest and during camera shake correction.

[0150]

As described above, according to the zoom lens of the present invention, in the four-unit zoom lens, at least one aspheric surface is arranged in each of the second to fourth lens units having a small lens diameter. By adopting the optimal aspherical shape and lens type, a small zoom lens with a wide-angle end angle of view of 62 degrees or more and a good correction of various aberrations including chromatic aberration with a small lens configuration Can be realized.

Further, according to the zoom lens of the present invention, it is possible to realize a compact zoom lens having a high-performance camera shake correction function.

Further, according to the video camera of the present invention,
Since the zoom lens of the present invention is used, a small and wide-angle video camera can be realized.

[Brief description of the drawings]

FIG. 1 is a layout diagram showing a configuration of a zoom lens according to a first embodiment of the present invention.

FIG. 2 is a layout diagram showing a configuration of a zoom lens according to a second embodiment of the present invention.

FIG. 3 is a layout diagram showing a configuration of a zoom lens according to a third embodiment of the present invention.

FIG. 4 is a layout diagram showing a configuration of a zoom lens having a camera shake correction function according to a fourth embodiment of the present invention.

FIG. 5 is a layout diagram showing a configuration of a video camera according to a fifth embodiment of the present invention.

FIG. 6 is an aberration performance diagram at the wide-angle end of the zoom lens according to the first embodiment of the present invention.

FIG. 7 is an aberration performance diagram at a standard position of the zoom lens according to the first embodiment of the present invention.

FIG. 8 is an aberration performance diagram at the telephoto end of the zoom lens according to the first embodiment of the present invention.

FIG. 9 is a diagram showing aberration performance of the zoom lens according to the first embodiment at the telephoto end at the time of correcting 0.3-degree camera shake.

FIG. 10 is an aberrational performance diagram at the wide-angle end of a zoom lens according to a second embodiment of the present invention.

FIG. 11 is an aberration performance diagram at a standard position of the zoom lens according to the second embodiment of the present invention.

FIG. 12 is an aberrational performance diagram at the telephoto end of a zoom lens according to a second embodiment of the present invention.

FIG. 13 is an aberration performance diagram of the zoom lens according to the second embodiment of the present invention at the telephoto end at the time of 0.3-degree camera shake correction.

FIG. 14 is an aberrational performance diagram at the wide-angle end of a zoom lens according to a third embodiment of the present invention.

FIG. 15 is an aberrational performance diagram at a standard position of the zoom lens according to the third embodiment of the present invention.

FIG. 16 is an aberrational diagram at the telephoto end of a zoom lens according to a third embodiment of the present invention.

FIG. 17 is a diagram showing aberration performance of the zoom lens according to the third embodiment of the present invention at the telephoto end at the time of correcting a 0.3-degree camera shake.

FIG. 18 is an aberrational performance diagram at the wide-angle end of a zoom lens according to a fourth embodiment of the present invention.

FIG. 19 is a diagram showing aberration performance of the zoom lens according to the fourth embodiment at the standard position.

FIG. 20 is an aberrational diagram at the telephoto end of a zoom lens according to a fourth embodiment of the present invention.

FIG. 21 is an aberration performance diagram at the telephoto end of the zoom lens according to Embodiment 4 of the present invention at the time of 0.3 ° camera shake correction.

FIG. 22 is a diagram showing aberration performance of the zoom lens according to the fifth embodiment of the present invention at the wide-angle end.

FIG. 23 is an aberrational diagram at a standard position of the zoom lens according to Embodiment 5 of the present invention.

FIG. 24 is an aberrational diagram at the telephoto end of a zoom lens according to a fifth embodiment of the present invention.

FIG. 25 is a diagram showing aberration performance at the telephoto end of the zoom lens according to Embodiment 5 of the present invention at the time of correcting a 0.3-degree camera shake.

[Explanation of symbols]

 11, 21, 31, 41 First lens group 12, 22, 32, 42 Second lens group 13, 23, 33, 43 Third lens group 14, 24, 34, 44 Third lens group 15, 25, 35, 45 diaphragm 16, 26, 36, 46 flat plate 17, 27, 37, 47 image plane 48 detector 49 driving device 51 zoom lens 52 imaging device 53 signal processing circuit

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshiyuki Ii 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture F-term (reference) 2H087 KA03 MA15 NA07 PA07 PA08 PA19 PA20 PB10 QA02 QA07 QA17 QA21 QA25 QA34 QA42 QA45 QA45 RA05 RA12 RA13 RA32 RA42 RA43 SA23 SA27 SA29 SA32 SA63 SA65 SA72 SA74 SB04 SB14 SB24 SB32 5C022 AA11 AB55 AB66 AC54 AC55

Claims (16)

[Claims] 1. A first lens having a positive refractive power and fixed to an image plane, which is arranged in order from an object side to an image plane side.
A lens group, a second lens group having a negative refractive power and performing zooming by moving on the optical axis, a diaphragm fixed to the image plane, and a third lens having a positive refractive power. A lens group, and a fourth lens group having a positive refractive power and moving on the optical axis so as to keep the image plane, which fluctuates by the movement of the second lens group and the object, at a fixed position from the reference plane Wherein the second lens group includes three lenses, two negative lenses and one positive lens, and includes at least one aspheric surface. The third lens group includes: The fourth lens group includes a positive lens including at least one aspherical surface, and includes a positive lens including at least one aspherical surface, and includes three positive lenses and two negative lenses. And zoom lens. 2. The second lens group includes a negative lens, a cemented lens of a negative lens and a positive lens, which are arranged in order from the object side.
2. The zoom lens according to claim 1, comprising a plurality of lenses. 3. The zoom lens according to claim 1, wherein the second lens group includes three lenses, a negative lens, a negative lens, and a positive lens, arranged in order from the object side. 4. The third lens group includes a positive lens, a cemented lens of a positive lens and a negative lens, which are arranged in order from the object side.
2. The zoom lens according to claim 1, comprising a plurality of lenses. 5. The zoom lens according to claim 1, wherein the third lens group includes three lenses, a positive lens, a positive lens, and a negative lens, arranged in order from the object side. 6. The zoom lens according to claim 1, wherein the following conditional expression (1) is satisfied, where f2 is the focal length of the second lens group and fw is the focal length of the entire system at the wide-angle end. 1.0 <| f2 | / fw <2.0 (1) 7. A second lens group comprising three lenses of a first negative lens, a second negative lens, and a positive lens arranged in order from the object side, and the second negative lens has an object side. Is an aspheric surface, and the local radius of curvature near the optical axis is R1
2. The zoom lens according to claim 1, wherein the following conditional expression (2) is satisfied, where 0 and a local radius of curvature of the outer peripheral portion is R11. 0.8 <| R11 | / | R10 | <3.0 (2) 8. The zoom lens according to claim 1, wherein the following conditional expression (3) is satisfied, where f3 is the focal length of the third lens group and fw is the focal length of the entire system at the wide-angle end. 2.5 <f3 / fw <4.0 (3) 9. The object-side surface of the lens closest to the object side of the third lens group is an aspherical surface, the local radius of curvature near the optical axis is R20, and the local radius of curvature of the outer peripheral portion is R21. The zoom lens according to claim 1, wherein the following conditional expression (4) is satisfied. 1.1 <R21 / R20 <2.0 (4) 10. The following conditional expression (5) is satisfied, where R30 is the absolute value of the radius of curvature of the image side surface of the concave lens included in the third lens group, and f3 is the focal length of the third lens group. 2. The zoom lens according to 1. 0.35 <R30 / f3 <0.6 (5) 11. The zoom lens according to claim 1, wherein the following conditional expression (6) is satisfied, where f4 is the focal length of the fourth lens group and fw is the focal length of the entire system at the wide-angle end. 2.4 <f4 / fw <3.0 (6) 12. When the object-side surface of the lens in the fourth lens group is an aspheric surface, the local radius of curvature near the optical axis is R40, and the local radius of curvature of the outer peripheral portion is R41, the following conditional expression ( The zoom lens according to claim 1, which satisfies the condition (7). 1.3 <R41 / R40 <1.6 (7) 13. The optical system according to claim 13, wherein the third lens group is provided on the object side.
When the stop diameter of the stop fixed to the image plane decreases as the focal length of the entire system increases, and the stop diameter at the telephoto end is St and the stop diameter at the wide-angle end is Sw, the following conditional expression (8)
The zoom lens according to claim 1, satisfying the following. St / Sw <0.92 (8) 14. The zoom lens according to claim 1, further comprising a function of correcting a fluctuation of an image due to camera shake by moving the entire third lens group perpendicularly to an optical axis. 15. When the amount of movement of the third lens group at the focal length f of the entire system at the time of camera shake correction is Y, the amount of movement of the third lens group at the telephoto end is Yt, and the focal length at the telephoto end is ft. The zoom lens according to claim 14, wherein the following conditional expressions (9) and (10) are satisfied. Yt> Y (9) (Y / Yt) / (f / ft) <1.5 (10) 16. A video camera provided with a zoom lens, wherein the zoom lens according to claim 1 is used as the zoom lens.