JP2001221948A - Zoom lens - Google Patents

Abstract

[PROBLEMS] To realize a zoom lens in which various aberrations including chromatic aberration are satisfactorily corrected with a small lens configuration of ten lenses and which has an angle of view of 62 ° or more. A first lens group having a positive refractive power and fixed with respect to an image plane, and a second lens group having a negative refractive power and performing a zooming action by moving on an optical axis. Lens group 12
An aperture 15 fixed to the image plane 17, a third lens group 13 having a positive refractive power, and an image plane having a positive refractive power and fluctuating due to movement of the second lens group 12 and an object. 1
The fourth lens group 14 that moves on the optical axis so as to keep the lens 7 at a fixed position from the reference plane is arranged in this order from the object side. The second lens group 12 is composed of two negative lenses and one positive lens, the third lens group 13 is composed of two positive lenses and one negative lens, and the fourth lens group 1
4 is constituted by one lens. Second lens group 1
Each of the second, third and fourth lens groups 13 and 14 includes at least one aspheric 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 which is used in a video camera or the like and has a small angle of view at a wide angle end of 62.degree. Or more, a zoom lens having a camera shake correction function, and a zoom lens using them. For video cameras.

[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 small size 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 a high image quality and a 10 × zoom ratio having an angle of view at the wide angle end of 59.2 ° to 60.7 °.

[0004]

However, the zoom lens disclosed in the above-mentioned publication 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 °. It was below. In order to achieve 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 is a problem that a small zoom lens cannot be realized.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in the prior art, and various aberrations including chromatic aberration can be satisfactorily corrected with a lens structure of as few as 10 lenses, and an angle of view of 62 ° or more can be obtained. Another object of the present invention is to provide a zoom lens having a camera shake correction function and a zoom lens having a camera shake correction function, and to provide a small, high-quality video camera using the zoom lens.

[0006]

In order to achieve the above object, a first configuration of an aspherical zoom lens according to the present invention is as follows.
A first lens group fixed to the image plane, having a positive refractive power, arranged in order from the object side, and having a negative refractive power;
A second lens group that performs a zooming action by moving on the optical axis, a stop fixed to the image plane, a third lens group having a positive refractive power, and a positive refractive power; A zoom lens comprising: a second lens group; and a fourth lens group that moves on an optical axis so as to keep an image plane that fluctuates due to movement of an object at a fixed position from a reference plane, wherein the second lens group Is constituted by three lenses including a first negative lens and a cemented lens of a second negative lens and a positive lens arranged in order from the object side, and includes at least one aspheric surface, The third lens group includes a first positive lens, a cemented lens of a second positive lens having a refractive index of 1.55 or less and an Abbe number of 65 or more, and a cemented lens of a second lens and a negative lens arranged in order from the object side. And three lenses consisting of Both include aspheric first surface, said fourth
The lens group includes at least one aspheric surface.

A second configuration of the aspherical zoom lens according to the present invention includes a first lens group having a positive refractive power and fixed to an image plane, which is arranged in order from the object side; A second lens group having a negative refractive power and performing zooming by moving on the optical axis, a stop fixed to the image plane, and a third lens group having a positive refractive power; 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 due to the movement of the object, at a constant position from the reference plane. So,
The second lens group is a first lens group arranged in order from the object side.
And three lenses including a negative lens and a cemented lens of a second negative lens and a positive lens,
The third lens group includes at least one aspheric surface,
A first positive lens arranged in order from the object side;
The fourth lens group includes at least one aspheric surface, and is configured by three lenses including a second positive lens having a refractive index of 5 or less and an Abbe number of 65 or more, and a negative lens. It is characterized by including at least one aspheric surface.

A third configuration of the aspherical zoom lens according to the present invention includes a first lens group having a positive refractive power and fixed to an image plane, which is arranged in order from the object side; A second lens group having a negative refractive power and performing zooming by moving on the optical axis, a stop fixed to the image plane, and a third lens group having a positive refractive power; 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 due to the movement of the object, at a constant position from the reference plane. So,
The second lens group is a first lens group arranged in order from the object side.
A negative lens, a second negative lens, and a positive lens, and includes at least one aspheric surface, the third lens group is arranged in order from the object side, At least one surface of a first positive lens and a cemented lens of a second positive lens having a refractive index of 1.55 or less and an Abbe number of 65 or more and a cemented lens of a negative lens. The fourth lens group includes at least one aspherical surface.

According to the first to third configurations of these zoom lenses, various types of aberration including chromatic aberration can be achieved with a lens configuration as small as 10 by optimizing the lens type, the arrangement of the aspheric surfaces, and the shape of the aspheric surfaces. Can be satisfactorily corrected. In addition, since the diameters of the lenses constituting the second lens group, the third lens group, and the fourth lens group are all small, the aspheric lenses included in these lens groups can be easily manufactured. In addition, since the third lens group is composed of three lenses including two positive lenses and one negative lens, the third lens group is small and has good spherical aberration from the wide-angle end to the standard position. A corrected zoom lens can be realized.

On the other hand, the condition that the second positive lens constituting the third lens group has a refractive index of 1.55 or less and an Abbe number of 65 or more satisfactorily reduces axial chromatic aberration and field curvature over the entire zoom range. It is effective in correcting.

Further, the zoom lenses according to the first to the first aspects of the present invention.
In the third configuration, 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,
It is preferable that the following condition (Equation 12) is satisfied. [Equation 12] 1.0 <| f2 | / fw <2.0 According to this preferred example, despite the wide angle,
It is possible to realize a small zoom lens in which the curvature of field is corrected to be small.

Also, the zoom lens according to the present invention has the following first to first aspects.
In the third configuration, the object-side surface of the second negative lens that forms the second lens group is an aspheric surface, the local radius of curvature near the optical axis of the aspheric surface is R10, and the outer circumference of the aspheric surface is When the local radius of curvature of the portion is R11, the following (Equation 13)
Is preferably satisfied. [Equation 13] 0.8 <| R11 | / | R10 | <3.0 According to this preferred example, coma can be favorably corrected on the wide-angle side and spherical aberration can be favorably corrected on the telephoto side.

Further, the first to the fifth zoom lenses of the present invention.
In the third configuration, the focal length of the third lens group is f
3. When the focal length of the entire system at the wide-angle end is fw,
It is preferable that the following condition is satisfied. [Equation 14] 2.5 <f3 / fw <4.0 According to this preferred example, it is possible to realize a small-sized zoom lens having a secured back focus into which a crystal filter, an IR cut filter, or the like can be inserted. it can.

Also, the first to the fifth zoom lenses of the present invention.
In the third configuration, the focal length of the entire system at the wide-angle end is fw, and the first positive lens and the second
When the air gap between the lens and the positive lens is d31, it is preferable that the following condition (Equation 15) is satisfied. [Equation 15] 0.02 <d31 / fw <0.50 According to this preferred example, axial chromatic aberration can be favorably corrected with a glass material having no practical problem while maintaining a manufacturable lens interval. .

Further, the first to the fifth zoom lenses of the present invention.
In the third configuration, the object-side surface of the lens closest to the object that forms the third lens group is an aspheric surface, the local radius of curvature near the optical axis of the aspheric surface is R20, and the aspheric surface is When the local radius of curvature of the outer peripheral portion is R21, it is preferable that the following condition (Equation 16) is satisfied. [Formula 16] 1.05 <R21 / R20 <2.0 According to this preferred example, spherical aberration over the entire zoom range can be favorably corrected.

Further, the first to the fifth zoom lenses of the present invention.
In the third configuration, 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, the following condition (Equation 17) is satisfied. Preferably. [Equation 17] 0.35 <R30 / f3 <0.6 According to this preferred example, coma aberration of a light beam outside the principal ray of off-axis light can be favorably corrected.

Also, the zoom lens according to the first to the first aspects of the present invention.
In the third configuration, the focal length of the fourth lens group is f
4. When the focal length of the entire system at the wide-angle end is fw,
It is preferable that the following condition (Equation 18) is satisfied. [Equation 18] 2.3 <f4 / fw <3.0 According to this preferred example, it is possible to realize a small-sized zoom lens with a secured back focus, into which a crystal filter or an IR cut filter can be inserted. it can.

Further, the first to the fifth zoom lenses of the present invention.
In the third configuration, the object-side surface of the fourth lens group is an aspheric surface, the local radius of curvature near the optical axis of the aspheric surface is R40, and the local radius of curvature of the outer peripheral portion of the fourth lens group is R40. Is R41, it is preferable that the following condition (Equation 19) is satisfied. [Equation 19] 1.3 <R41 / R40 <1.6 According to this preferred example, the coma aberration of the light flux inside the principal ray of the off-axis light can be favorably corrected.

Further, the zoom lenses according to the first to the first aspects of the present invention.
In the third configuration, the stop diameter of the stop decreases as the focal length of the entire system increases, and the stop diameter at the telephoto end is set to S.
When t and the aperture diameter at the wide angle end are Sw, it is preferable that the following condition (Equation 20) is satisfied. [Equation 20] St / Sw <0.92 According to this preferred example, deterioration of aberration on the long focal length side can be reduced.

Further, the zoom lenses according to the first to fifth aspects of the present invention are described below.
In the third configuration, a function of correcting the image movement at the time of camera shake by moving the entire third lens group perpendicularly to the optical axis according to the shake amount obtained from the camera shake amount detector. Preferably it is provided. According to this preferred example, compared to the type in which some lenses inside the lens group are moved perpendicularly to the optical axis, the entire camera group having a uniform optical performance is moved, so that the camera shake with less deterioration of aberration is achieved. A zoom lens having a correction function can be realized. In this case, 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. Then, the following (Equation 21), (Equation 22)
Is preferably satisfied. [Equation 21] Yt> Y [Equation 22] (Y / Yt) / (f / ft) <1.5 According to this preferred example, a zoom lens having a camera shake correction function with less deterioration in optical performance is realized. can do.

Further, the structure of a zoom lens according to the present invention is characterized in that the zoom lens according to the present invention is used. According to the configuration of the video camera, a small-sized and wide-angle video camera can be realized.

[0022]

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

FIG. 1 shows a first embodiment of the present invention.
FIG. 3 is a configuration diagram showing a zoom lens according to the embodiment. As shown in FIG. 1, the zoom lens according to the present embodiment includes a first lens group 11, a second lens group 12, and a stop 1 arranged in order from the object side to the image plane 17 side.
5, a third lens group 13, a fourth lens group 14, and a flat plate 16 equivalent to an optical low-pass filter and a face plate of a CCD.

The first lens group 11 has a positive refractive power,
It is fixed to the image plane 17 both during zooming and during focusing. The second lens group 12 includes three lenses including 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. Has a refractive power of The second lens group 12 is a lens group that performs a zooming action by moving on the optical axis. The third lens group 13 is composed of three lenses including a first positive lens and a cemented lens of a second positive lens and a negative lens arranged in order from the object side. In addition, at the time of focusing, it is fixed to the image plane 17. The fourth lens group 14 is composed of a single lens having a positive refractive power, and is configured to maintain the second lens group 12 and the image plane 17 that fluctuates due to the movement of the object at a fixed position from the reference plane. Move on an axis. That is, the fourth lens group 14 simultaneously moves the image by zooming and adjusts the focus by moving on the optical axis.

The second positive lens constituting the third lens group preferably has a refractive index of 1.55 or less and an Abbe number of 65 or more. By satisfying these conditions, axial chromatic aberration and curvature of field in the entire zoom range can be favorably corrected.

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 condition (Equation 23) is satisfied. [Equation 23] 1.0 <| f2 | / fw <2.0 The above (Equation 23) is a conditional 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 |
If / fw is 2.0 or more, the amount of movement of the second lens group 12 during zooming becomes large, and the overall length becomes long.
It is difficult to realize a small zoom lens.

The object-side surface of the second negative lens constituting the second lens group 12 is an aspheric surface, the local radius of curvature near the optical axis of the aspheric surface is R10, and the outer peripheral portion of the aspheric surface is When the local radius of curvature of is represented by R11, the following (Equation 24)
It is desirable that the following condition be satisfied. [Expression 24] 0.8 <| R11 | / | R10 | <3.0 | R11 | / | R10 | is 3.0 or more, outside of the light ray outside the principal ray of the off-axis light on the wide angle side. A large coma aberration occurs, and spherical aberration is insufficiently corrected on the telephoto side. ｜ R
When 11 | / | R10 | is 0.8 or less, the spherical aberration is excessively corrected, especially on the telephoto side, and a large inner coma occurs near the standard position, so that good aberration correction cannot be obtained.

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 that the following condition (Equation 25) is satisfied. [Equation 25] 2.5 <f3 / fw <4.0 The above (Equation 25) is a conditional expression regarding 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.

As described above, the third lens group 13
It is composed of three lenses consisting of one positive lens and one negative lens. 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.

The air gap between the first positive lens and the second positive lens constituting the third lens group 13 is d31,
When the focal length of the entire system at the wide-angle end is fw, it is preferable that the following condition (Equation 26) is satisfied. [Equation 26] 0.02 <d31 / fw <0.5 When d31 / fw is equal to or less than 0.02, the two lenses may contact each other due to a manufacturing error, and the lens surface may be damaged. When d31 / fw is 0.5 or more, it is difficult to satisfactorily correct longitudinal chromatic aberration with a glass material having no practical problem.

Further, the object-side surface of the lens located closest to the object and constituting the third lens group 13 is an aspheric surface,
When the local radius of curvature near the optical axis of the aspheric surface is R20, and the local radius of curvature of the outer peripheral portion of the aspheric surface is R21,
It is desirable that the following condition (Equation 27) be satisfied. [Equation 27] 1.05 <R21 / R20 <2.0 The above (Equation 27) is a conditional expression relating to the aspherical surface of the object-side surface of the lens that is the most object-side lens constituting the third lens group 13. , Which defines a range in which spherical aberration is favorably corrected. When R21 / R20 becomes 1.05 or less,
When negative spherical aberration occurs and R21 / R20 becomes 2.0 or more, 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 condition (Equation 28) is satisfied. Is desirable. [Equation 28] 0.35 <R30 / f3 <0.6 The conditional expression (Equation 28) defines the range in which the coma of the light beam outside the principal ray of the off-axis light is favorably corrected. is there. When R30 / f3 becomes 0.6 or more, an inward frame occurs at the zooming intermediate position, and when R30 / f3 becomes 0.35 or less, an outward frame occurs.

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 that the following condition (Equation 29) is satisfied. [Equation 29] 2.3 <f4 / fw <3.0 The above (Equation 29) is a conditional expression regarding the power of the fourth lens group 14. When f4 / fw is 2.3 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. When f4 / fw becomes 3.0 or more, the amount of movement of the fourth lens group 14 during focusing increases,
It is difficult to realize a small zoom lens.

The object-side surface of the lens of the fourth lens group 14 is an aspherical surface. The local radius of curvature near the optical axis of the aspherical surface is R40, and the local radius of curvature of the outer peripheral portion of the aspherical surface is R40. When R41, it is preferable that the following condition (Equation 30) is satisfied. [Equation 30] 1.3 <R41 / R40 <1.6 The above (Equation 30) is a conditional expression regarding the aspherical surface of the object-side surface of the fourth lens unit 14, and is located inside the principal ray of the off-axis light. This defines the range in which the coma of the light beam 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.

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 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, it is desirable that the following condition (Equation 31) is satisfied. [Equation 31] St / Sw <0.92 When St / Sw is 0.92 or more, the deterioration of aberration at the long focal length side, particularly at the telephoto end, becomes large.

It is desirable that the entire third lens group 13 be moved perpendicular to the optical axis to correct image fluctuations due to camera shake. As a result, deterioration of chromatic aberration during correction can be reduced.

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 (correction lens) at the telephoto end is Yt, and the focal length at the telephoto end is ft, it is preferable that the following conditions (Equation 32) and (Equation 33) are satisfied. [Equation 32] Yt> Y [Equation 33] (Y / Yt) / (f / ft) <1.5 The above (Equation 32) and (Equation 33) represent the movement amount of the third lens group 13 (correction lens). It is a conditional expression regarding. In the case of a zoom lens, when the correction angle is constant in the entire zoom range, the larger the zoom ratio, the larger the amount of movement of the correction lens, and conversely, the smaller the zoom ratio, the smaller the amount of movement of the correction lens.
If the values deviate from the limits of the above (Equation 32) and (Equation 33), the correction will be excessive and the optical performance including monochromatic aberration will be greatly deteriorated.

[Second Embodiment] FIG. 2 shows a second embodiment of the present invention.
FIG. 3 is a configuration diagram showing a zoom lens according to the embodiment. As shown in FIG. 2, the zoom lens according to the present embodiment includes a first lens group 21, a second lens group 22, and a stop 2 arranged in order from the object side to the image plane 27 side.
5, a third lens group 23, a fourth lens group 24, and a flat plate 26 equivalent to an optical low-pass filter and a face plate of a CCD.

The first lens group 21 has a positive refractive power,
It is fixed with respect to the image plane 27 both during zooming and during focusing. The second lens group 22 is composed of three lenses including 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. Has a refractive power of The second lens group 22 is a lens group that performs a variable power operation by moving on the optical axis. The third lens group 23 includes three lenses including a first positive lens, a second positive lens, and a negative lens arranged in order from the object side. It is fixed with respect to the image plane 27. The fourth lens group 24 is composed of a single lens having a positive refractive power. The fourth lens group 24 keeps the second lens group 22 and the image plane 27 that fluctuates due to the movement of the object at a fixed position from the reference plane. Move on an axis. That is, the fourth lens group 24 simultaneously moves the image by zooming and adjusts the focus by moving on the optical axis.

As in the case of the first embodiment, the second positive lens constituting the third lens group 23 has a refractive index of 1.5.
It is desirable that the Abbe number be 5 or less and the Abbe number be 65 or more. Further, it is desirable that the conditions of (Equation 23) to (Equation 33) are satisfied.

[Third Embodiment] FIG. 3 shows a third embodiment of the present invention.
FIG. 3 is a configuration diagram showing a zoom lens according to the embodiment. As shown in FIG. 3, the zoom lens according to the present embodiment includes a first lens group 31, a second lens group 32, and a stop 3 arranged in order from the object side to the image plane 37 side.
5, a third lens group 33, a fourth lens group 34, and a flat plate 36 equivalent to an optical low-pass filter and a face plate of a CCD.

The first lens group 31 has a positive refractive power.
It is fixed to the image plane 37 both during zooming and during focusing. The second lens group 32 is composed of three lenses including a first negative lens, a second negative lens, and a positive lens arranged in order from the object side, and has a negative refractive power as a whole. have. This second lens group 32
Denotes a lens group that performs a zooming action by moving on the optical axis. The third lens group 33 is composed of three lenses including a first positive lens and a cemented lens of a second positive lens and a negative lens, which are arranged in order from the object side. Also, during focusing, it is fixed to the image plane 37. The fourth lens group 34 is composed of a single lens having a positive refractive power, and is configured to maintain the image plane 37 that fluctuates due to the movement of the second lens group 32 and the object at a fixed position from the reference plane. Move on an axis. That is, the fourth lens group 34 simultaneously moves the image by zooming and adjusts the focus by moving on the optical axis.

As in the case of the first embodiment, the second positive lens constituting the third lens group 33 has a refractive index of 1.5.
It is desirable that the Abbe number be 5 or less and the Abbe number be 65 or more. Further, it is desirable that the conditions of (Equation 23) to (Equation 33) are satisfied.

[Fourth Embodiment] FIG. 4 shows a fourth embodiment of the present invention.
FIG. 3 is a configuration diagram illustrating a zoom lens having a camera shake correction function according to the embodiment. As shown in FIG. 4, in the zoom lens having a camera shake correction function according to the present embodiment, a first lens group 41 and a second lens group 42 constituting the zoom lens according to the first to third embodiments. , 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 an image sensor 47 are arranged in this order. The third lens group 43 is connected to a detector 48 via a driving device 49 having a driving circuit.
Is connected. Here, the detector 48 detects the amount of camera shake. The driving device 49 moves the third lens group 43 in two directions perpendicular to the optical axis.
As a result, it is possible to realize a zoom lens having a small and highly accurate camera shake correction function.

[Fifth Embodiment] FIG. 5 shows a fifth embodiment of the present invention.
FIG. 3 is a configuration diagram showing a video camera according to the embodiment. The video camera according to the present embodiment is
A zoom lens 51, an image sensor 52, and a signal processing circuit 53 according to the fourth embodiment are configured.
Thereby, a small-sized and wide-angle video camera can be realized.

[0046]

The present invention will be described below in further detail with reference to specific examples.

Example 1 Table 1 below shows numerical examples of the zoom lens according to the first embodiment.

[0048]

[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 aspherical shape is defined by the following (Equation 34) (the same applies to the following Examples 2 to 5).

[0051]

(Equation 34)

Where SAG: distance from the aspherical vertex to a point on the aspherical surface at a height H from the optical axis H: height from the optical axis R: radius of curvature of the aspherical vertex K: conical constant D, E: Aspherical surface coefficient The following (Table 2) shows the aspherical shape of the zoom lens in the present embodiment.

[0053]

[Table 2]

Table 3 below shows values of an air gap variable by zooming when an object point is located at a position 2 m from the front end of the lens. Table 3 below shows the aperture diameter that changes with the focal length.

[0055]

[Table 3]

In the above (Table 3), the standard position is a position where the third lens group 13 and the fourth lens group 14 come closest to each other. F, F / NO, and ω (゜) represent the focal length, F number, and half angle of incidence at the wide-angle end, the standard position, and the telephoto end of the zoom lens shown in Table 1 above. As can be seen from the above (Table 3), the angle of view at the wide-angle end in this embodiment is 65.60 °.

In the zoom lens of this embodiment, as shown in Table 1 above, the second positive lens of the third lens group 13 has a refractive index of 1.55 or less and an Abbe number of 65 or more. The axial chromatic aberration and the field curvature in the entire zoom range are corrected well.

Table 4 below shows specific numerical values corresponding to the above (Equation 23) to (Equation 33) in this embodiment.

[0059]

[Table 4]

As shown in the above (Table 4), this embodiment
Although the focal length f2 of the second lens group 12 satisfies the above (Equation 23) and is wide-angle, it is possible to realize a small zoom lens in which the field curvature is corrected to be small.

The zoom lens in this embodiment is
A first lens group 12 is arranged in order from the object side.
, And three lenses including a second negative lens and a cemented lens of a positive lens. The object-side surface of the second negative lens is an aspherical surface. In particular, the local radius of curvature R10 near the optical axis of the aspherical surface and the local radius of curvature R11 of the outer peripheral portion of the aspherical surface are as described above ( It has the values shown in Table 4), and satisfies the conditional expression (Equation 24). Thereby, the coma on the wide-angle side and the spherical aberration on the telephoto side are satisfactorily corrected.

The zoom lens in this embodiment is
As shown in the above (Table 4), the focal length f3 of the third lens group 13 satisfies the above (Equation 25), and the crystal filter and the I
A small zoom lens having a back focus capable of inserting an R-cut filter or the like has been realized.

In the zoom lens of this embodiment, the third lens group 13 is composed of three lenses including a first positive lens and a cemented lens of a second positive lens and a negative lens. A zoom lens that is small and has a good correction of spherical aberration from the wide-angle end to the standard position is realized.

In the zoom lens of this embodiment, the first positive lens and the second
Has the value shown in the above (Table 4), and satisfies the above (Equation 26). Thereby, axial chromatic aberration is favorably corrected while maintaining a manufacturable lens interval.

Further, in the zoom lens of this embodiment, both surfaces of the lens which is the most object side of the third lens group 13 are aspherical, and in particular, the optical axis of the object side surface of the aspherical surface The local radius of curvature R20 in the vicinity and the local radius of curvature R21 in the outer peripheral portion of the aspheric surface have the values shown in the above (Table 4), and the above (Equation 27) is satisfied. As a result, spherical aberration over the entire zoom range is satisfactorily corrected.

In the zoom lens of this embodiment, the absolute value R30 of the radius of curvature of the image side surface of the concave lens included in the third lens group 13 and the focal length f of the third lens group 13
3 has the value shown in the above (Table 4), and the above (Equation 28) is satisfied. As a result, the coma of the light beam outside the principal ray of the off-axis light is favorably corrected.

Further, in the zoom lens of this embodiment, as shown in Table 4 above, the focal length f4 of the fourth lens group 14 satisfies the above (Equation 29), and a quartz filter, an IR cut filter, etc. Thus, a compact zoom lens having a back focus capable of inserting a zoom lens has been realized.

In the zoom lens of this embodiment, the object-side surface of the lens of the fourth lens unit 14 is an aspheric surface, and the local radius of curvature R40 near the optical axis of the aspheric surface and the aspheric surface of the aspheric surface. The local radius of curvature R41 of the outer peripheral portion has the value shown in the above (Table 4), and the above (Equation 30) is satisfied. As a result, the coma of the light beam inside the principal ray of the off-axis light is favorably corrected.

In the zoom lens of this embodiment, the stop diameter of the stop 15 fixed with respect to the image plane provided on the object side of the third lens group 13 is as shown in Table 3 above. The ratio decreases as the focal length of the entire system increases, and the ratio of the stop diameter St at the telephoto end to the stop diameter Sw at the wide-angle end has the value shown in Table 4 above. That is, the above (Equation 3)
1) is satisfied, and the aberration at the long focal length side, particularly at the telephoto end, is favorably corrected.

In this embodiment, 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 suppressed to a small value.

In this embodiment, the third lens group 13 (correction lens) at the wide-angle end, the standard position, and the telephoto end
The movement amount Y and the focal length f of the entire system satisfy the above (Equation 32) and (Equation 33) as shown in the above (Table 4), thereby suppressing the deterioration of various aberrations at the time of correction. Have been.

FIGS. 6 to 8 show aberration performance diagrams of the zoom lens shown in (Table 1) at the wide-angle end, the standard position, and the telephoto end. In each of the drawings, (a) is a diagram of spherical aberration with respect to d-line. (B) is a diagram of astigmatism, where a solid line indicates sagittal field curvature and a broken line indicates meridional field curvature. (C) is a diagram of distortion, (d) is a diagram of axial chromatic aberration, a solid line shows a value for d line, a short dashed line shows a value for F line, and a long dashed line shows a value for C line. I have. (E) is a diagram of chromatic aberration of magnification, where a short dashed line indicates a value for the F line, and a long dashed line indicates a value for 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 shows the aberration performance at the telephoto end at the time of 0.3 ° camera shake correction. In FIG. 9, (f) shows the relative image height of 0.75, (g) shows the center of the screen, and (h) shows the lateral aberration at the relative image height of -0.75. The solid line indicates the d line, the short dashed line indicates the F line, and the long dashed line indicates the C line. The above description of (f) to (h) is based on FIG.
3, FIG. 17, FIG. 21, and FIG.

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 Table 5 below shows other numerical examples of the zoom lens according to the first embodiment. The first lens group 11, the second lens group 12, and the aperture 15 are omitted because they are the same as those in the first embodiment (Table 1).

[0076]

[Table 5]

Table 6 below shows the aspherical shape of the zoom lens of this embodiment.

[0078]

[Table 6]

The following (Table 7) shows, as an example of an air gap variable by zooming, a value obtained when an object point is located at a position 2 m from the front end of the lens. Table 7 below shows the aperture diameter that changes with the focal length.

[0080]

[Table 7]

As can be seen from Table 7 above, the angle of view at the wide-angle end in this embodiment is 65.7 °.

In the zoom lens of this embodiment, as shown in Table 5 above, the second positive lens of the third lens group 13 has a refractive index of 1.55 or less and an Abbe number of 65 or more. I have.

Table 8 below shows specific numerical values corresponding to the above (Equation 23) to (Equation 33) in this embodiment.

[0084]

[Table 8]

As shown in the above (Table 8), the zoom lens in this embodiment satisfies the above-mentioned conditions (Equation 23) to (Equation 33).

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.
収 差 Shows aberration performance at the time of camera shake correction. As can be seen from FIGS. 10 to 13, the zoom lens according to the present embodiment shows good aberration performance.

Example 3 Table 9 below shows still another numerical example of the zoom lens according to the first embodiment. The first lens group 11, the second lens group 12, and the aperture 15 are omitted because they are the same as those in the first embodiment (Table 1).

[0088]

[Table 9]

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

[0090]

[Table 10]

The following (Table 11) shows, as an embodiment of an air gap variable by zooming, a value when an object point is located at a position 2 m from the front end of the lens. Table 11 below shows the aperture diameter that changes with the focal length.

[0092]

[Table 11]

As can be seen from the above (Table 11), the angle of view at the wide-angle end in this embodiment is 65.5 °.

As shown in Table 9 above, the second positive lens of the third lens group 13 has a refractive index of 1.55 or less and an Abbe number of 65 or more. I have.

Table 12 below shows specific numerical values corresponding to the above (Equation 23) to (Equation 33) in this embodiment.

[0096]

[Table 12]

As shown in the above (Table 12), the zoom lens of this embodiment satisfies the above-mentioned conditions (Equation 23) to (Equation 33).

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

Example 4 The following (Table 13) shows the second
14 shows numerical examples of the zoom lens according to the embodiment.

[0100]

[Table 13]

The following (Table 14) shows the aspherical shape of the zoom lens in this embodiment.

[0102]

[Table 14]

The following (Table 15) shows values when an object point is located at a position 2 m from the front end of the lens as an example of the air gap variable by zooming. Table 15 below shows the aperture diameter that changes with the focal length.

[0104]

[Table 15]

As can be seen from the above (Table 15), the angle of view at the wide-angle end in this embodiment is 69.5 °.

In the zoom lens according to this embodiment, as shown in Table 13 above, the second positive lens in the third lens group 23 has a refractive index of 1.55 or less and an Abbe number of 65 or more. I have.

The following Table 16 shows specific numerical values corresponding to the above (Equation 23) to (Equation 33) in this embodiment.

[0108]

[Table 16]

As shown in the above (Table 16), the zoom lens of this embodiment satisfies the conditional expressions (Equation 23) to (Equation 33).

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

(Example 5) The following (Table 17)
14 shows numerical examples of the zoom lens according to the embodiment.

[0112]

[Table 17]

Table 18 below shows the aspherical shape of the zoom lens according to the present embodiment.

[0114]

[Table 18]

The following (Table 19) shows, as an example of an air gap variable by zooming, a value obtained when an object point is located at a position 2 m from the front end of the lens. Table 19 below shows the aperture diameter that changes with the focal length.

[0116]

[Table 19]

As can be seen from the above (Table 19), the angle of view at the wide-angle end in this embodiment is 72.9 °.

In the zoom lens of this embodiment, as shown in Table 17 above, the second positive lens of the third lens group 33 has a refractive index of 1.55 or less and an Abbe number of 65 or more. I have.

The following (Table 20) shows specific numerical values corresponding to the above (Equation 23) to (Equation 33) in this embodiment.

[0120]

[Table 20]

As shown in the above (Table 20), the zoom lens of the present embodiment satisfies the conditions of (Equation 23) to (Equation 33).

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.
3 shows aberration performance at the time of camera shake correction. As can be seen from FIGS. 22 to 25, the zoom lens according to the present embodiment shows good aberration performance.

[0123]

As described above, according to the present invention,
In a four-unit zoom lens, at least one aspheric surface is arranged in each of the second lens unit, the third lens unit, and the fourth lens unit having a small lens diameter, and by adopting an optimal aspherical shape and lens type. It is possible to realize a small zoom lens having a wide-angle end angle of view of 62 ° or more and an aberration corrected satisfactorily with a lens configuration of as few as 10 lenses.

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

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

[Brief description of the drawings]

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

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

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

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

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

FIG. 6 is an aberration diagram at a wide angle end according to the first embodiment.

FIG. 7 is an aberration diagram at a standard position according to the first embodiment.

FIG. 8 is an aberration diagram at a telephoto end in Example 1.

FIG. 9 is an aberration diagram at the telephoto end in Example 1 at the time of 0.3 ° camera shake correction.

FIG. 10 is an aberration diagram at a wide-angle end according to a second embodiment.

FIG. 11 is an aberration diagram at a standard position according to the second embodiment.

FIG. 12 is an aberration diagram at a telephoto end in Example 2.

13 is an aberration diagram at the telephoto end of Example 2 at the time of 0.3 ° camera shake correction. FIG.

FIG. 14 is an aberration diagram at a wide-angle end according to a third embodiment.

FIG. 15 is an aberration diagram at a standard position in Example 3.

FIG. 16 is an aberration diagram at a telephoto end in Example 3;

FIG. 17 is an aberration diagram at the telephoto end of Example 3 at the time of 0.3 ° camera shake correction.

FIG. 18 is an aberration diagram at a wide-angle end according to a fourth embodiment.

FIG. 19 is an aberration diagram at a standard position in Example 4.

FIG. 20 is an aberration diagram at a telephoto end in Example 4.

FIG. 21 is an aberration diagram at the telephoto end of Example 4 at the time of 0.3 ° camera shake correction;

FIG. 22 is an aberration diagram at a wide-angle end in Example 5.

FIG. 23 is an aberration diagram at a standard position in Example 5.

FIG. 24 is an aberration diagram at a telephoto end in Example 5.

FIG. 25 is an aberration diagram at the telephoto end of Example 5 at the time of 0.3 ° camera shake correction;

[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 Fourth lens group 15, 25, 35, 45 diaphragm 16, 26, 36, 46 flat plate 17, 27, 37, 47 image plane 48 detector 49 driver 51 zoom lens 52 image sensor 53 signal processing circuit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshiyuki Ii 1006 Kazuma Kadoma, Kazuma City, Osaka Prefecture F-term (reference) 2H087 KA03 MA15 NA07 PA07 PA08 PA20 PB10 QA02 QA07 QA17 QA21 QA25 QA34 QA42 QA45 RA05 RA12 RA13 RA32 RA43 SA23 SA27 SA29 SA32 SA63 SA65 SA72 SA74 SB04 SB14 SB24 SB32 9A001 KK16 KK29 KK42

Claims (15)

[Claims] 1. A first lens group having a positive refractive power and fixed with respect to an image plane, arranged in order from the object side, and having a negative refractive power and moving on an optical axis. A second lens group having a variable magnification function, a stop fixed to an image plane, a third lens group having a positive refractive power, and a second lens group and an object having a positive refractive power. A fourth lens group that moves on the optical axis so as to keep the image plane that fluctuates due to the movement at a constant position from the reference plane,
The second lens group is a first lens group arranged in order from the object side.
And three lenses including a negative lens and a cemented lens of a second negative lens and a positive lens,
The third lens group includes at least one aspheric surface,
A first positive lens arranged in order from the object side;
The fourth lens, including three lenses including a second positive lens having a refractive index of 5 or less and an Abbe number of 65 or more and a cemented lens of a negative lens, and including at least one aspheric surface, A zoom lens, wherein the group includes at least one aspheric surface. 2. A first lens group having a positive refractive power and fixed with respect to an image plane, arranged in order from the object side, and having a negative refractive power and moving on an optical axis. A second lens group having a variable magnification function, a stop fixed to an image plane, a third lens group having a positive refractive power, and a second lens group and an object having a positive refractive power. A fourth lens group that moves on the optical axis so as to keep the image plane that fluctuates due to the movement at a constant position from the reference plane,
The second lens group is a first lens group arranged in order from the object side.
And three lenses including a negative lens and a cemented lens of a second negative lens and a positive lens,
The third lens group includes at least one aspheric surface,
A first positive lens arranged in order from the object side;
The fourth lens group includes at least one aspheric surface, and is configured by three lenses including a second positive lens having a refractive index of 5 or less and an Abbe number of 65 or more, and a negative lens. A zoom lens comprising at least one aspheric surface. 3. A first lens group having a positive refractive power and fixed with respect to an image plane, which is arranged in order from the object side, and having a negative refractive power and moving on an optical axis. A second lens group having a variable magnification function, a stop fixed to an image plane, a third lens group having a positive refractive power, and a second lens group and an object having a positive refractive power. A fourth lens group that moves on the optical axis so as to keep the image plane that fluctuates due to the movement at a constant position from the reference plane,
The second lens group is a first lens group arranged in order from the object side.
A negative lens, a second negative lens, and a positive lens, and includes at least one aspheric surface, the third lens group is arranged in order from the object side, At least one surface of a first positive lens and a cemented lens of a second positive lens having a refractive index of 1.55 or less and an Abbe number of 65 or more and a cemented lens of a negative lens. A zoom lens including an aspheric surface, wherein the fourth lens group includes at least one aspheric surface. 4. The optical system according to claim 1, wherein when the focal length of the second lens group is f2 and the focal length of the entire system at the wide-angle end is fw, the following condition is satisfied. Zoom lens. [Equation 1] 1.0 <| f2 | / fw <2.0 5. An object-side surface of a second negative lens constituting the second lens group is an aspheric surface, a local radius of curvature near the optical axis of the aspheric surface is R10, and an outer peripheral portion of the aspheric surface is The zoom lens according to any one of claims 1 to 4, wherein the following condition (Equation 2) is satisfied when the local radius of curvature is R11. [Equation 2] 0.8 <| R11 | / | R10 | <3.0 6. The optical system according to claim 1, wherein the following condition is satisfied 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. Zoom lens. [Equation 3] 2.5 <f3 / fw <4.0 7. The focal length of the entire system at the wide-angle end is fw,
Assuming that the air gap between the first positive lens and the second positive lens constituting the third lens group is d31, the following (Equation 4)
The zoom lens according to claim 1, wherein the following condition is satisfied. [Equation 4] 0.02 <d31 / fw <0.50 8. The object-side surface of the lens located closest to the object that forms the third lens group is an aspheric surface, the local radius of curvature near the optical axis of the aspheric surface is R20, and the outer periphery of the aspheric surface The aspherical zoom lens according to any one of claims 1 to 7, wherein the following condition (Equation 5) is satisfied when the local radius of curvature of the portion is R21. [Equation 5] 1.05 <R21 / R20 <2.0 9. 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, the following condition (Equation 6) is satisfied. The zoom lens according to claim 1. [Equation 6] 0.35 <R30 / f3 <0.6 10. The lens system according to claim 1, wherein the following condition (Equation 7) is satisfied when the focal length of the fourth lens unit is f4 and the focal length of the entire system at the wide-angle end is fw. Zoom lens. [Equation 7] 2.3 <f4 / fw <3.0 11. The object-side surface of the fourth lens group is an aspheric surface, and the local radius of curvature of the aspheric surface near the optical axis is R4.
0, when the local radius of curvature of the outer peripheral portion of the aspherical surface is R41, the following condition (Equation 8) is satisfied.
0. The zoom lens according to any one of 0 to 0. [Equation 8] 1.3 <R41 / R40 <1.6 12. When the stop diameter of the stop 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 condition (Equation 9) is satisfied. The zoom lens according to claim 1, wherein the zoom lens is satisfied. [Equation 9] St / Sw <0.92 13. A function of correcting the movement of an image at the time of camera shake by moving the entire third lens group perpendicularly to the optical axis in accordance with the camera shake obtained from the camera shake detector. The zoom lens according to claim 1. 14. 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 13, wherein the following conditions (Equation 10) and (Equation 11) are satisfied. [Equation 10] Yt> Y [Equation 11] (Y / Yt) / (f / ft) <1.5 15. A video camera using the zoom lens according to claim 1.