JP2000105336A - Zoom lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zoom lens capable of covering from an ultra-wide angle area to an ultra-telephotographing area, being miniaturized and compensating every kind of aberration by setting the angle of view to >=85 deg. at a wide angle end and <=2.5 deg. at a telephotographing end by assuming the use of a camera shake correction means depending on video signal processing. SOLUTION: In this zoom lens 1 having a lens system constituted of 19 lenses being five groups; f1.4 is the synthetic focal distance of the 1st lens L1 to the 4th lens L4 of a 1st lens group Gr1, fI is the synthetic focal distance of the 1st lens group, h1.4 is the height of a paraxial ray which is parallel with an optical axis and whose height is 1 at the time of emitting the paraxial ray from the 4th lens when the paraxial ray is made incident from an object side, f1.3 is the synthetic focal distance of the 1st lens to the 3rd lens L3 of the 1st lens group, f2 is the focal distance of the 2nd lens L2 and r6 is the radius of curvature of the surface of the 3rd lens on an image surface side. Respective conditions |fI/f1.4|<0.04, 1,25<hl.4<1.5, 0.2<|f1.3/f2|<0.5 and 0.8<r6/fI<1.5 are satisfied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-magnification zoom lens for a video camera covering an ultra wide angle range to a super telephoto range.

[0002]

2. Description of the Related Art In a zoom lens for a consumer video camera, there are two directions in which the advantages of a miniaturized image pickup device can be utilized. There is a direction to aim for a higher magnification of the zoom ratio.

[0003] By the way, in increasing the zoom ratio of the above-mentioned zoom lens, on the telephoto side, shaking of the screen due to camera shake is a serious problem in practical use.
Therefore, as means for mitigating the influence of such camera shake, an optical camera shake correction means using a variable apex angle prism and the like, and an image in a narrow range is cut out from the effective image circle of the lens and outputted, Accordingly, a camera shake correction unit based on video signal processing has been devised in which the range of the cutout is made variable sequentially.

In correcting camera shake using the variable apex angle prism, it is necessary to configure the lens system so as to cover the entire angle of view even if the variable apex angle prism is small. This is advantageous from the viewpoint of. As a zoom lens designed with such an intention, for example, there is a zoom lens described in JP-A-8-5913.

In the zoom lens described in the above publication, the zoom ratio is about 20 times. However, recently, with the miniaturization of the image pickup device, a zoom lens having a larger zoom ratio has been required. Have been.

[0006]

However, when the zoom ratio is increased, for example, when a zoom ratio exceeding 40 times is considered, there are the following problems.

That is, in a zoom lens using an optical camera shake correcting means using a variable apex angle prism, a narrower angle of view at the wide-angle end can reduce the size of the variable apex angle prism. Although the angle of view at the wide-angle end is narrowed, the angle of view at the telephoto end becomes extremely narrow, which increases the amount of screen sway remaining after camera shake correction. As a result, there arises a problem that it is not possible to achieve both camera shake correction and downsizing of the lens system.

In general, it is preferable for the user to increase the zoom ratio of the zoom lens because the photographing areas on both the wide-angle side and the telephoto side are widened. As long as the zoom lens is used, the widening of the zoom lens is limited, which is contrary to the user's request.

Further, in the conventional lens system designing means as described in the above publication, the zoom lens having an ultra-high magnification zoom ratio in which the diameter of the front lens is small has the following characteristics.
That is, since the light flux is limited by the effective diameter of the first lens group, the F value at the telephoto end becomes dark, and the light flux passing through the second lens group becomes thin. As a result, the first lens group at the telephoto end becomes lighter. There arises a problem that the generated spherical aberration cannot be corrected by the second lens group.
The lens group cannot be composed of three general lenses. In order to solve the spherical aberration generated at the telephoto end, it is effective to configure one of the lens surfaces of the lenses constituting the first lens group with an aspheric surface. Increases in costs are inevitable.

The present invention has been made in view of the above-mentioned problems, and presupposes the use of camera shake correction means by video signal processing.
85 ° or more at wide angle end, 2.5 at telephoto end
An object of the present invention is to provide a compact zoom lens capable of covering from the ultra-wide angle range to the super-telephoto range and having good correction of various aberrations.

[0011]

In order to solve the above-mentioned problems, a zoom lens according to the present invention includes a first lens unit having a positive refractive power and a negative refractive power in order from an object side to an image plane side. A second lens group that is movable in the direction of the optical axis to mainly perform zooming, a third lens group that has positive refractive power, and a focal point during zooming that has negative refractive power. The first lens group includes a fourth lens group movable in the optical axis direction for correcting a change in position and performing focusing, and a fifth lens group having a positive refractive power. From
A concave meniscus first lens having a convex surface facing the object side, a second lens having a convex lens facing the object side, a concave meniscus third lens having a convex surface facing the object side, a fourth lens having a convex lens, and a fifth lens having a concave lens. The second lens group is constituted by a cemented lens of a lens and a sixth lens of a convex lens and a seventh lens of a convex lens, and the second lens group is a cemented lens of an eighth lens of a concave lens, and a ninth lens of a concave lens and a tenth lens of a convex lens. A third lens group, the first lens group being a convex lens.
1 lens, 12th lens of concave lens and 1st lens of convex lens
The fourth lens group is composed of a cemented lens of three lenses, the fourth lens group is composed of a fourteenth lens of a concave lens, and a cemented lens of a fifteenth lens of a concave lens and a sixteenth lens of a convex lens, and the fifth lens group is It is composed of a seventeenth lens of a convex lens, a cemented lens of an eighteenth lens of a convex lens and a nineteenth lens of a concave lens, and f1.4 is a combined focal length of the first to fourth lenses of the first lens group, fI
Is the combined focal length of the first lens group, and h1.4 is the fourth focal length when a paraxial ray having a height of 1 and being parallel to the optical axis is incident from the object side.
Height of paraxial ray when exiting from lens L4, f1.3
Is the combined focal length of the first to third lenses in the first lens group, f2 is the focal length of the second lens, and r6 is the radius of curvature of the image-side surface of the third lens, | fI / f1.4. |
<0.04, 1.25 <h1.4 <1.5, 0.2 <|
f1.3 / f2 | <0.5, 0.8 <r6 / fI <1.
5 are satisfied.

Therefore, assuming the use of the camera shake correction means by video signal processing, the angle of view is 85 ° at the wide angle end.
As described above, a compact zoom lens having an angle of view of 2.5 ° or less at the telephoto end and capable of covering from the super-wide-angle range to the super-telephoto range can be configured with good correction of various aberrations. Will be possible.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the accompanying drawings. still,
1 to 4 show the first embodiment (numerical example 1), and FIGS. 5 to 8 show the second embodiment (numerical example 2).
It shows.

First, common items in each embodiment will be described.

In the following description, "si" is the i-th surface counted from the object side, "ri" is the radius of curvature of the surface si, and "di" is the i-th surface and the (i + 1) -th surface from the object side. And “ni” is the d-line (wavelength 5) of the i-th lens.
87.6 nm), “νi” is the Abbe number of the i-th lens, “f” is the focal length of the entire lens system, and “Fn”.
o. "Indicates an open F value and" ω "a half angle of view.

The lenses used in the embodiments include those having a lens surface formed by an aspherical surface. Accordingly, assuming that the depth of the aspheric surface is “x” and the height from the optical axis is “H”, x = H ² / ri ｛1+ (1−H ² / ri ² ) ^{1 / 2} $ + A4
H ⁴ + A 6 · H ⁶ + A 8 · H ⁸ + A 10 · H ¹⁰ A4, A6, A8
And A10 are fourth-order, sixth-order, eighth-order, and tenth-order aspherical coefficients, respectively.

The zoom lenses 1 and 2 in the first and second embodiments are, as shown in FIGS. 1 and 5, a first lens having a positive refractive power in order from the object side to the image plane IMG side. A group Gr1 and a second lens group Gr having a negative refractive power and movable in the optical axis direction to mainly perform zooming.
2, a third lens group Gr3 having a positive refractive power, and a negative lens power, which can be moved in the optical axis direction in order to correct a change in a focal position during zooming and perform focusing. And a fifth lens group Gr5 having a positive refractive power.

The first lens group Gr1 includes, in order from the object side,
Concave meniscus first lens L with the convex surface facing the object side
1, a second lens L2 of a convex lens, a third lens L3 of a concave meniscus shape having a convex surface facing the object side, a fourth lens L4 of a convex lens, a fifth lens L5 of a concave lens, and a sixth lens L6 of a convex lens. Of the cemented lens and the seventh of the convex lens
It is composed of seven lenses L7.

The second lens group Gr2 is composed of an eighth lens L8 of a concave lens, and a cemented lens of a ninth lens L9 of a concave lens and a tenth lens L10 of a convex lens.

The third lens unit Gr3 includes an eleventh lens unit of a convex lens type.
It is composed of three lenses, a lens L11 and a cemented lens of a twelfth lens L12 of a concave lens and a thirteenth lens L13 of a convex lens.

The fourth lens unit Gr4 includes a fourteenth concave lens unit.
It is composed of three lenses, a cemented lens of a lens L14, a fifteenth lens L15 as a concave lens, and a sixteenth lens L16 as a convex lens.

The fifth lens unit Gr5 includes a seventeenth lens unit of a convex lens type.
It is composed of three lenses, a cemented lens of a lens L17 and an eighteenth lens L18 of a convex lens and a nineteenth lens L19 of a concave lens.

The zoom lenses 1 and 2 have f1.
4 is a combined focal length of the first to fourth lenses L1 to L4 of the first lens unit Gr1, fI is a combined focal length of the first lens unit Gr1, h1.4 is a paraxial ray parallel to the optical axis and having a height of 1. Is incident from the object side, the height of the paraxial ray when exiting from the fourth lens L4, f1.3 is the combined focal length of the first to third lenses of the first lens group, and f2 is the second Assuming that the focal length of the lens, r6, is the radius of curvature of the image-side surface of the third lens, | fI / f1.4 | <0.04 (hereinafter referred to as “conditional expression 1”), 1.25 <h1 0.4 <1.5 (hereinafter, referred to as “conditional expression 2”), 0.2 <| f1.3 / f2 | <0.5 (hereinafter, referred to as “conditional expression 3”), 0.8 <r6 /FI<1.5 (hereinafter referred to as “conditional expression 4”).

As described above, the zoom lenses 1 and 2 of the present invention have the first lens group Gr1 composed of seven lenses for the purpose of achieving both ultra wide angle and correction of spherical aberration at the telephoto end. It has the main features.

The first lens unit Gr1 includes a front unit having a negative refractive power, which includes a first lens L1 to a third lens L3,
It can be divided into a rear group having a positive refractive power, which is composed of the fourth lens L4 to the seventh lens L7.

The front group of the first lens group Gr1 has, for example, a structure similar to the front group of a retrofocus wide-angle lens in a so-called single-lens reflex camera, and the inclination of the principal ray at the wide-angle end affected by the angle of view. Is converted to a smaller value to narrow the angle of view encompassed by the lens systems of the rear group and thereafter.

The front group of the first lens group Gr1 has a strong negative refractive power, but has a first lens L1 and a third lens L3 in order to minimize the occurrence of barrel-shaped distortion. Is a concave meniscus lens having a convex surface facing the object side. Further, since it is necessary to correct distortion at the wide-angle end with a positive refractive power, the second lens L2 is a convex lens.
Is to correct this.

The rear group of the first lens group Gr1 has a fourth lens L4 for making the light beam spread in the front group substantially afocal, a fifth lens L5 for forming a converging system, and a sixth lens L5.
It comprises a lens L6 and a seventh lens L7. Fifth lens L
The fifth, sixth, and seventh lenses L6 and L7 have a configuration similar to the first lens group of a general video camera zoom lens, and vary in aberrations during zooming in balance with the second lens group Gr2. It has the function of suppressing.

Then, in order to apply a conventional (existing) lens configuration to the lens system after the fifth lens L5, the first lens L1 to the fourth lens L4 are made to have substantially afocal system characteristics. The above condition (1) defines the condition (1).

Therefore, the first to fourth lenses L1 to L
If the afocal characteristic of the lens No. 4 breaks down to have a negative refractive power, the positive refractive power of the fifth lens L5 to the seventh lens L7 becomes strong, and the telephoto side of the intermediate focal length region in zooming. In this case, it becomes difficult to correct spherical aberration and coma. Conversely, if the afocal characteristic of the first lens L1 to the fourth lens L4 breaks down to have a positive refractive power, the fourth lens L4
And the spherical aberration caused by this becomes large, and it becomes difficult to correct the spherical aberration.

Conditional expression 2 defines each magnification of the afocal system (first lens L1 to fourth lens L4) so that the conventional lens configuration can be applied to the lens system after the fifth lens L5. Things. That is, the reason that the value of h1.4 is within the range defined by the conditional expression 2 is that
In order to achieve both ultra-high zoom ratio and miniaturization of the zoom ratio in the zoom lenses 1 and 2, the F-number at the telephoto end is limited by limiting the luminous flux by the effective diameter of the fourth lens L4 to the seventh lens L7. This is because darkening the telephoto end is used as a means of correcting aberration.

Therefore, if the value of h1.4 in conditional expression 2 is below the lower limit, the angles of view of the lens systems subsequent to the fifth lens L5 are widened, and the fourth lens L4 to the seventh lens L
7 has an increased effective diameter, making it difficult to correct spherical aberration, core aberration, and axial chromatic aberration at the telephoto end. Also,
If the value of h1.4 exceeds the upper limit, the negative refractive power of the front group of the first lens group Gr1 becomes too strong, and it becomes difficult to correct distortion at the wide angle end.

Conditional expression 3 describes the distortion at the wide-angle end,
This defines conditions for enabling the second lens L2 to perform correction with good balance.

Therefore, when the value of | f1.3 / f2 | exceeds the lower limit, the above correction cannot be performed sufficiently, and
The barrel distortion becomes strong. Also, | f1.3
When the value of / f2 | exceeds the upper limit, the curvature of the distortion aberration curve and the curvature of the lateral chromatic aberration curve at the wide-angle end become large, and it becomes difficult to correct these with a good balance between the intermediate image height and the maximum image height. .

Conditional expression 4 defines conditions relating to correction of spherical aberration at the telephoto end. That is, at the telephoto end, the spherical aberration on the under side generated from the fourth lens L4 to the seventh lens L7 is reduced by the image plane IM of the third lens L3.
This is for correcting on the surface s6 on the G side. In general, a conventional zoom lens is configured to correct under-side spherical aberration generated from the first lens group by over-side spherical aberration generated from the second lens group.

In the zoom lenses 1 and 2, when zooming from the wide-angle end to the telephoto end, the first lens unit Gr1
When the thickness of the luminous flux passing through the second lens unit Gr2 and the thickness of the second lens unit Gr2 both increase, as in the case of the above-described conventional method, cancellation by spherical aberration on the under side and over side acts, but F at the telephoto end. Since making the value darker is one means of aberration correction, the light flux is limited by the effective diameter of the fourth lens L4 to the seventh lens L7. Therefore, the distance d13 between the second lens group and the first lens group is reduced. As the size increases, the thickness of the light beam passing through the second lens group Gr2 starts to decrease, and the above-described conventional method of canceling out due to under-side and over-side spherical aberration does not hold. Therefore, when the zoom ratio at which the telephoto end is extremely dark compared to the wide-angle end such as the zoom lenses 1 and 2 has an ultra-high zoom ratio, the spherical aberration generated from the first lens group Gr1 is smaller than the first lens group Gr1. It is necessary to suppress as much as possible.

Accordingly, when the value of r6 / fI is below the lower limit, the spherical aberration on the over side becomes strong and the correction is excessive, and when the value of r6 / fI exceeds the upper limit, the correction of the spherical aberration is insufficient. At the same time, in order to satisfy Condition 2, the negative refractive power of the first lens L1 increases, making it difficult to correct distortion at the wide-angle end.

Regarding the correction of chromatic aberration at the telephoto end, the zoom lenses 1 and 2 are composed of the fourth lens L4, the sixth lens L6, and the seventh lens L7 of the first lens group Gr1, where ν4 is the material forming the fourth lens L4. Assuming that Abbe's number, ν6 is the Abbe number of the material forming the sixth lens L6, and ν7 is the Abbe number of the material forming the seventh lens L7, 70 <(ν4
+ Ν6 + ν7) / 3 (hereinafter referred to as “conditional expression 5”).

For the correction of the chromatic aberration of the telephoto lens and the correction of the secondary spectrum, it is effective to use a material having a large Abbe number and an abnormal partial dispersion for the convex lens in the front group of the lens system. It is known.

However, in the zoom lenses 1 and 2, at the telephoto end, the incident light beam is spread most by the fourth to seventh lenses L4 to L7. Accordingly, the chromatic aberration at the telephoto end is caused by the fourth lens L4 to the seventh lens L4.
Since the fourth lens L4, the sixth lens L6, and the seventh lens L7, which are convex lenses, are made of a material suitable for correcting a secondary spectrum in a general telephoto lens, which is governed by the configuration of the lens L7. It is necessary to be formed of a material that satisfies the above conditional expression 5, that is, a so-called ultra-low dispersion glass. In addition, in the optical glass for the existing lens,
The above conditional expression 5 cannot be satisfied.

With respect to the correction of spherical aberration and coma on the wide-angle side, in the zoom lenses 1 and 2, at least one of the surfaces of the eleventh lens L11 to the thirteenth lens L13 constituting the third lens unit Gr3 is included. Is constituted by an aspherical surface, and at least one of the surfaces constituted by the aspherical surface has an aspherical shape having an effective diameter shallower than the depth of the paraxial spherical surface.

The third diverging light beam that has exited the second lens group Gr2 is turned into a convergent light beam and sent to the fourth lens group Gr4.
The lens group Gr3 has a strong positive refracting power and is a portion where a light beam spreads most at the wide-angle end, and therefore has a dominant influence on spherical aberration and coma at the wide-angle end. Therefore, in order to gently convert the divergent light beam to the convergent light beam, the third lens group Gr3 is divided into two lens groups each having a positive refractive power, and one of them is provided with a joint surface having a negative refractive power. Is effective,
For the zoom lenses 1 and 2, the third lens group Gr3
Is a convex lens (an eleventh lens L11), a concave lens (a twelfth lens L12), and a convex lens (a thirteenth lens L13).
And the occurrence of spherical aberration and coma are suppressed. As described above, at least one of the surfaces s20 to s24 of the eleventh lens L11 to the thirteenth lens L13 is made aspherical, and among the aspherical surfaces, as described above. At least one surface has an aspherical shape with an effective diameter that is shallower than the depth of the paraxial spherical surface.

Regarding the correction of astigmatism and distortion at the wide-angle end, in the zoom lenses 1 and 2, the surfaces s30 to s34 of the seventeenth lens L17 to the nineteenth lens L19 constituting the fifth lens group Gr5 are Of which at least one
Is constituted by an aspherical surface, and at least one of the surfaces constituted by the aspherical surface has an aspherical shape having an effective diameter shallower than the depth of the paraxial spherical surface.

In the fifth lens group Gr5, the principal ray that has been jumped outward by the fourth lens group Gr4 has a ray height higher than the maximum image height, and the fifth ray group Gr5 has an exit pupil located behind the image plane. It is necessary to bend at the lens group Gr5. Therefore, in order to gently bend the principal ray, in the fifth lens group GR5, the positive refractive power is divided into two lens groups, and one of them is provided with a cemented surface having a negative refractive power. . That is, the convex lens (the seventeenth lens L1)
7) and a cemented lens of a convex lens (the eighteenth lens L18) and a concave lens (the nineteenth lens L19) so as to suppress astigmatism and distortion.

As described above, at least one of the surfaces s30 to s34 of the seventeenth lens L17 to the nineteenth lens L19 is made aspherical, and the aspherical surface is used, as described above. At least one of them has an aspherical shape having a smaller effective diameter than the depth of the paraxial spherical surface.

Since the zoom lenses 1 and 2 are for a video camera, a camera shake correcting means is applied. That is, the zoom lenses 1 and 2 are not optical shake correction means using a variable apex angle prism or the like, but cut out and output an image in a narrow range from the effective image circle of the lens, and respond to the shake. A camera shake correction unit based on video signal processing, in which the cutout range is sequentially variable, is applied.

In general, the influence of camera shake on the screen is very small on the wide-angle side and becomes larger on the telephoto side. In the camera shake correcting means based on the video signal processing, the size of the effective screen cut out after correcting the camera shake from the entire effective pixel range of the image sensor is constant over the entire zooming range, and the effective screen is changed from the entire effective pixel range. The remaining part excluding the part is a part that can be used for camera shake correction. Even on the wide-angle side where camera shake correction is hardly necessary, if the range used for camera shake correction is used effectively, the effective image circle must cover the entire effective pixel range.

Therefore, in the zoom lenses 1 and 2, since the ultra wide-angle lens is already sufficient at the wide-angle end for the effective screen, it is difficult to widen the effective image circle and further widen the angle. On the wide-angle side, the correction range of the camera shake on the effective pixel range is limited narrowly, and on the telephoto side, the effective image circle is set so as to widen the correction range of the camera shake.

Next, matters unique to each embodiment will be described.

Table 1 shows each value of the zoom lens 1.

[0051]

[Table 1]

As shown in Table 1, the distances d13, d18, d24, and d29 are variable (variable) due to the operations involved in zooming and focusing of the zoom lens 1.
able). Therefore, Table 2 shows that the wide-angle end (f = 1.0
0), d13 and d at the telephoto end (f = 39.87) and the intermediate focal position between the wide-angle end and the telephoto end (f = 17.56)
The values of 18, d24 and d29 are shown.

[0053]

[Table 2]

In the third lens unit Gr3 and the fifth lens unit Gr5, the surface s20 of the twelfth lens L12 and the surface s32 of the eighteenth lens are aspherical. Table 3 shows the fourth, sixth, eighth, and tenth planes s20 and s32.
The following aspheric coefficients A4, A6, A8, and A10 are shown.

[0055]

[Table 3]

Note that "E" in Table 3 above means an exponential expression with a base of 10 (the same applies to Table 7 described later).

Table 4 shows the values of the conditional expressions 1 to 5 of the zoom lens 1 and f, Fno. And 2ω.

[0058]

[Table 4]

FIGS. 2 to 4 show the zoom lens 1 at the wide-angle end.
The spherical aberration figure, the astigmatism figure, and the distortion figure at the intermediate focal position between the wide-angle end and the telephoto end and at the telephoto end are shown, respectively.
In the spherical aberration diagram, the solid line is the d line, the dashed line is the g line (wavelength 435.8 nm), and the dashed line is the C line (wavelength 656.3).
nm), and in the astigmatism diagram, the solid line indicates the value on the sagittal image plane, and the broken line indicates the value on the meridional image plane.

Table 5 shows each value of the zoom lens 2.

[0061]

[Table 5]

As shown in Table 5, the distances d13, d18, d24, and d29 are variable (variable) due to the operations involved in zooming and focusing of the zoom lens 1.
able). Accordingly, Table 6 shows that the wide-angle end (f = 1.0
0), d13 and d at the telephoto end (f = 39.76) and at the intermediate focal point position between the wide-angle end and the telephoto end (f = 17.17)
The values of 18, d24 and d29 are shown.

[0063]

[Table 6]

In the third lens unit Gr3 and the fifth lens unit Gr5, the surfaces s20 and s21 of the twelfth lens L12 and the surface s32 of the eighteenth lens are aspherical. Table 7 shows the four values of the surfaces s20, s21, and s32.
Next, sixth, eighth and tenth order aspherical coefficients A4, A6, A
8, A10 are shown.

[0065]

[Table 7]

Table 8 shows the values of the conditional expressions 1 to 5 of the zoom lens 2, and f, Fno. And 2ω.

[0067]

[Table 8]

FIGS. 6 to 8 show the zoom lens 2 at the wide-angle end.
The spherical aberration figure, the astigmatism figure, and the distortion figure at the intermediate focal position between the wide-angle end and the telephoto end and at the telephoto end are shown, respectively.
In the spherical aberration diagram, the solid line indicates the value on the d-line, the broken line indicates the value on the g-line, and the dashed line indicates the value on the C-line. In the astigmatism diagram, the solid line indicates the value on the sagittal image plane, and the broken line indicates the value on the meridional image plane. It is shown.

As described above, the zoom lenses 1 and 2 of the present invention are
Is an ultra-wide-angle range where f is equivalent to 25 mm to 1000 mm when converted to a lens for a camera using a 35 mm film.
An ultra-high-magnification zoom lens with a zoom ratio of 40, covering the super-telephoto range, composed of 19 elements in 5 groups, using three ultra-low dispersion glasses, and an aspherical shape with an effective diameter shallower than the depth of the paraxial sphere, With a lens system using two so-called glass mold aspherical lenses, it is possible to obtain a high-quality image in which various aberrations including distortion are corrected in a well-balanced manner over the entire zooming range.

The zoom lens 1 has a total length of 125.5 mm when the diagonal length of the effective pixel range is 4.5 mm and the diagonal length of the effective screen is 3.38 mm.
The diameter of the front lens (first lens L1) is 56 mm, and the aperture diameter is about 9.
The movement amount of the second lens group Gr2 is about 30 mm, and the movement amount of the fourth lens group Gr4 is about 12 mm. Accordingly, since the movement amounts of the second lens group Gr2 and the fourth lens group Gr4 are almost the same as those of the conventional zoom lens, the conventional technology can be applied to the moving mechanism of these lens groups, so that the productivity is high. Despite having a size sufficient for practical use as a zoom lens for a small video camera, an angle of view of 2.5 ° from an ultra-wide angle range exceeding an angle of view of 85 °
Covering the following super-telephoto range, it is possible to perform hand-held shooting in the super-telephoto range in correspondence with a camera shake correction unit using a video signal processing method.

Further, the specific shapes and structures of the respective parts shown in the above embodiments are merely examples of the embodiment of the present invention.
These should not limit the technical scope of the present invention.

[0072]

As is apparent from the above description, the zoom lens according to the present invention sequentially moves from the object side to the image plane side.
A first lens group having a positive refracting power, a second lens group having a negative refracting power and movable mainly in the optical axis direction for zooming, and a third lens group having a positive refracting power. A fourth lens group having a negative refractive power, having a negative refractive power, being movable in the optical axis direction for correcting a change in the focal position during zooming and performing focusing, and a positive refractive power. A first lens group having a concave meniscus shape having a convex surface facing the object side in order from the object side;
A second lens of a convex lens, a third lens of a concave meniscus shape having a convex surface facing the object side, a fourth lens of a convex lens,
The second lens group includes a cemented lens of a fifth lens of a concave lens and a sixth lens of a convex lens, and a seventh lens of a convex lens. The second lens group includes an eighth lens of a concave lens, a ninth lens of a concave lens, and a tenth lens of a convex lens. The third lens group is constituted by an eleventh lens of a convex lens, and the cemented lens of a twelfth lens of a concave lens and a thirteenth lens of a convex lens, and the fourth lens group Gr
4 is composed of a fourteenth lens of a concave lens, a cemented lens of a fifteenth lens of a concave lens and a fifteenth lens of a convex lens, and a fifth lens group is composed of a seventeenth lens of a convex lens, an eighteenth lens of a convex lens, and a concave lens. F1.4 is the combined focal length of the first to fourth lenses of the first lens unit, fI
Is the combined focal length of the first lens group, and h1.4 is the fourth focal length when a paraxial ray having a height of 1 and being parallel to the optical axis is incident from the object side.
Height of paraxial ray when exiting from lens L4, f1.3
Is the combined focal length of the first to third lenses in the first lens group, f2 is the focal length of the second lens, and r6 is the radius of curvature of the image-side surface of the third lens, | fI / f1.4. |
<0.04, 1.25 <h1.4 <1.5, 0.2 <|
f1.3 / f2 | <0.5, 0.8 <r6 / fI <1.
Since each of the conditions of (5) is satisfied, it is possible to cover from the ultra-wide-angle range to the super-telephoto range, and it is possible to correct various aberrations, especially spherical aberration, in a well-balanced manner over the entire zooming range.

According to the invention described in claim 2, ν4
Is the Abbe number of the material forming the sixth lens, ν6 is the Abbe number of the material forming the sixth lens, and ν7 is the Abbe number of the material forming the seventh lens. The lens is set to 70 <(ν4 + ν6 + ν7) / 3
, The chromatic aberration and the secondary spectrum at the telephoto end can be effectively corrected.

According to the third and fourth aspects of the present invention, of the surfaces of the lenses constituting the third lens group,
At least one surface is formed by an aspheric surface, and among the surfaces formed by the aspheric surface, at least one surface has an aspheric shape that is shallower than the depth of the paraxial sphere in an effective diameter. The occurrence of coma can be suppressed.

According to the inventions set forth in claims 5 to 8, at least one of the surfaces of the lenses constituting the fifth lens group is constituted by an aspheric surface, and Since at least one of the surfaces has an aspherical shape with a smaller effective depth than the paraxial sphere, the occurrence of astigmatism and distortion on the wide-angle side can be suppressed.

Further, in the inventions according to the ninth to sixteenth aspects, the effective image circle at the telephoto end is made larger than the effective image circle at the wide-angle end, so that it is used for camera shake correction in the video signal processing system. A camera shake correction range obtained by extracting an effective screen from the entire effective pixel range of the imaging device can be effectively used even in a wide angle range.

[Brief description of the drawings]

FIG. 1 shows a first embodiment of a zoom lens according to the present invention together with FIGS. 2 to 4, and FIG. 1 is a schematic diagram showing a lens configuration.

FIG. 2 is a diagram illustrating spherical aberration, astigmatism, and distortion at a wide-angle end.

FIG. 3 is a diagram illustrating spherical aberration, astigmatism, and distortion at an intermediate focal position between a wide-angle end and a telephoto end.

FIG. 4 is a diagram illustrating spherical aberration, astigmatism, and distortion at the telephoto end.

FIG. 5 shows a second embodiment of the zoom lens of the present invention together with FIG. 6 to FIG. 8, and FIG. 5 is a schematic diagram showing a lens configuration.

FIG. 6 is a diagram showing spherical aberration, astigmatism, and distortion at the wide-angle end.

FIG. 7 is a diagram illustrating spherical aberration, astigmatism, and distortion at an intermediate focal position between a wide-angle end and a telephoto end.

FIG. 8 is a diagram showing spherical aberration, astigmatism, and distortion at the telephoto end.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... zoom lens, 2 ... zoom lens, Gr1 ... 1st lens group, Gr2 ... 2nd lens group, Gr3 ... 3rd lens group, Gr4 ... 4th lens group, Gr5 ... 5th lens group, L
1: 1st lens, L2: 2nd lens, L3: 3rd lens, L4: 4th lens, L6: 6th lens, L7: 7th
Lens, L8: Eighth lens, L9: Ninth lens, L10
... 10th lens, L11 ... 11th lens, L12 ... 1st lens
2 lenses, L13: 13th lens, L14: 14th lens, L15: 15th lens, L16: 16th lens, L
17 ... 17th lens, L18 ... 18th lens, L19 ...
19th lens, IMG ... image plane

Continued on the front page F-term (reference) 2H087 KA03 MA15 NA07 PA14 PA16 PB19 QA02 QA07 QA17 QA21 QA26 QA37 QA41 QA45 RA05 RA12 RA13 RA32 RA43 SA43 SA47 SA49 SA53 SA55 SA63 SA65 SB01 SB14 SB24 SB34 SB44 UA06 5C022 AA001 AB

Claims (16)

[Claims] 1. A first lens group having a positive refractive power and a negative refractive power, which are movable in the optical axis direction mainly to perform zooming, in order from an object side to an image plane side. A second lens group having a positive refractive power, a third lens group having a negative refractive power, and moving in the optical axis direction in order to correct a change in the focal position during zooming and to perform focusing. The first lens group includes a fourth lens group that is enabled and a fifth lens group having a positive refractive power. The first lens group has a concave meniscus first lens whose convex surface faces the object side in order from the object side. A second lens of a convex lens, a concave meniscus third lens having a convex surface facing the object side, a fourth lens of a convex lens, a cemented lens of a fifth lens of a concave lens and a sixth lens of a convex lens, and a convex lens Wherein the second lens group is a concave lens. The third lens group includes an eighth lens of a lens, a ninth lens of a concave lens, and a cemented lens of a tenth lens of a convex lens, and the third lens group includes an eleventh lens of a convex lens, a twelfth lens of a concave lens, and a The fourth lens group is constituted by a cemented lens of a thirteenth lens, and the fourth lens group is constituted by a cemented lens of a fourteenth lens of a concave lens, a fifteenth lens of a concave lens, and a sixteenth lens of a convex lens. Is a zoom lens comprising a seventeenth lens of a convex lens and a cemented lens of an eighteenth lens of a convex lens and a nineteenth lens of a concave lens, and satisfies the following conditions. | FI / f1.4 | <0.04 1.25 <h1.4 <1.5 0.2 <| f1.3 / f2 | <0.5 0.8 <r6 / fI <1.5 f1.4: Composite focal length of the first to fourth lenses of the first lens group, fI: Composite focal length of the first lens group, h1.4: Paraxial ray parallel to the optical axis and having a height of 1 The height of the paraxial ray when emitted from the fourth lens when incident from the side, f1.3: combined focal length of the first to third lenses of the first lens group, f2: focal point of the second lens Distance, r6: radius of curvature of the image-side surface of the third lens. 2. The zoom lens according to claim 1, wherein the fourth lens, the sixth lens, and the seventh lens are made of a material satisfying the following conditions. 70 <(ν4 + ν6 + ν7) / 3, where ν4 is the Abbe number of the material forming the fourth lens, ν6 is the Abbe number of the material forming the sixth lens, and ν7 is the Abbe number of the material forming the seventh lens. . 3. At least one of the surfaces of the lens constituting the third lens group is constituted by an aspheric surface, and at least one of the surfaces constituted by the aspheric surface is close to the effective diameter. The zoom lens according to claim 1, wherein the zoom lens has an aspherical shape that is shallower than a depth of the axial spherical surface. 4. At least one of the surfaces of the lens constituting the third lens group is formed by an aspheric surface, and at least one of the surfaces formed by the aspheric surface is close to the effective diameter. 3. The zoom lens according to claim 2, wherein the aspherical shape is formed shallower than the depth of the axial spherical surface. 5. The lens of the fifth lens group, wherein at least one of the surfaces has an aspherical surface, and at least one of the surfaces formed by the aspherical surface has a near effective diameter. The zoom lens according to claim 1, wherein the zoom lens has an aspherical shape that is shallower than a depth of the axial spherical surface. 6. A lens of a fifth lens group, wherein at least one of the surfaces has an aspherical surface, and at least one of the surfaces formed by the aspherical surface has a near effective diameter. 3. The zoom lens according to claim 2, wherein the aspherical shape is formed shallower than the depth of the axial spherical surface. 7. At least one of the surfaces of the lens constituting the fifth lens group is constituted by an aspheric surface, and at least one of the surfaces constituted by the aspheric surface is close to the effective diameter. The zoom lens according to claim 3, wherein the zoom lens has an aspherical shape that is shallower than a depth of the axial spherical surface. 8. At least one of the surfaces of the lens constituting the fifth lens group is constituted by an aspheric surface, and at least one of the surfaces constituted by the aspheric surface is close to the effective diameter. 5. The zoom lens according to claim 4, wherein the zoom lens has an aspherical shape that is shallower than a depth of the axial spherical surface. 9. The zoom lens according to claim 1, wherein the effective image circle at the telephoto end is larger than the effective image circle at the wide-angle end. 10. The zoom lens according to claim 2, wherein the effective image circle at the telephoto end is larger than the effective image circle at the wide-angle end. 11. The zoom lens according to claim 3, wherein an effective image circle at a telephoto end is larger than an effective image circle at a wide-angle end. 12. The zoom lens according to claim 4, wherein the effective image circle at the telephoto end is larger than the effective image circle at the wide angle end. 13. The zoom lens according to claim 5, wherein an effective image circle at a telephoto end is larger than an effective image circle at a wide-angle end. 14. The zoom lens according to claim 6, wherein an effective image circle at a telephoto end is larger than an effective image circle at a wide-angle end. 15. The zoom lens according to claim 7, wherein the effective image circle at the telephoto end is larger than the effective image circle at the wide angle end. 16. The zoom lens according to claim 8, wherein an effective image circle at the telephoto end is larger than an effective image circle at the wide-angle end.