JP2001296475A - Zoom lens and optical equipment using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a zoom lens by which a photographing viewing angle is widened, and whose portability is excellent by shortening a lens entire length, and which consists of three groups, and to provide an optical equipment using the zoom lens. SOLUTION: In the zoom lens having the first lens group L1 of negative refracting power, the second lens group L2 of positive refracting power and the third lens group L3 of the positive refracting power in this order from an object side and performing variable power by moving respective lens groups L1-L3, the third lens group L3 consists of one or two lenses including a positive lens, and refractive index ndp3 and Abbe number νdp3 of the material of the positive lens in the third lens group L3 are respectively appropriately set.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Recently, with the advancement of functions of an image pickup apparatus (camera) such as a video camera and a digital still camera using a solid-state image pickup device, an optical system used therein has a large aperture ratio zoom including a wide angle of view. Lenses are needed. In this type of camera, between the back of the lens and the image sensor,
In order to dispose various optical members such as a low-pass filter and a color correction filter, a lens system having a relatively long back focus is required for an optical system used therein. further,
In the case of a color camera using a color image pickup device,
In order to avoid color shading, it is desired that the optical system used has good telecentric characteristics on the image side.

Conventionally, there are two lens groups, a first lens group having a negative refractive power and a second lens group having a positive refractive power, and the magnification is changed by changing the distance between both lenses. Various types of so-called short zoom type wide-angle two-unit zoom lenses have been proposed. In these short zoom type optical systems, the second system having a positive refractive power
The magnification is changed by moving the group, and the image point position accompanying the magnification is corrected by moving the first group having a negative refractive power. In a lens configuration composed of these two lens groups,
The zoom magnification is about twice.

In order to combine the entire lens into a compact shape while having a high zoom ratio of 2 or more, for example, Japanese Patent Publication No. 7-3507 and Japanese Patent Publication No. 6-40170 disclose a two-group zoom lens. A so-called three-group zoom lens has been proposed in which a third lens group having a negative or positive refractive power is arranged on the image side to correct various aberrations that occur with increasing magnification.

Also, US Pat. No. 4,828,372 and US Pat.
Japanese Patent Application Publication No. 262897 also discloses a zoom lens in which a second group of a negative, positive, and positive three-group zoom lens includes two sets of cemented lenses, and the second group includes six lenses.

However, since these three-group zoom lenses are mainly designed for 35 mm film photography, they have both a back focus length required for an optical system using a solid-state image sensor and good telecentric characteristics. Was hard to say.

[0007]

A wide-angle three-unit zoom lens system satisfying the back focus and telecentric characteristics has been proposed in, for example, JP-A-63-135913 and JP-A-7-261803. I have. Japanese Patent Application Laid-Open No. 9-21950 discloses a three-lens group consisting of three lens units having negative, positive, and positive refractive powers sequentially from the object side.
In the group zoom lens, the third group having a positive refractive power is fixed, and the first group having a negative refractive power and the second group having a positive refractive power are moved to perform zooming. An optical system using two or more plastic lenses is also disclosed.

However, in these conventional examples, the number of components of each lens group is relatively large, and the total lens length is long.
It had disadvantages such as high manufacturing cost.

Further, in the zoom lens disclosed in Japanese Patent Application Laid-Open No. 9-21950, the mechanical structure can be simplified by fixing the third lens group.
Since the third lens group does not contribute to zooming, the amount of movement of the second lens group during zooming is relatively increased, which is disadvantageous for shortening the overall length of the lens.

Further, in recent years, in order to achieve both compactness of the camera and high magnification of the lens, the interval between the lens groups during non-photographing is reduced to a distance different from the photographing state, and the amount of projection of the lens from the camera body is reduced. A so-called collapsible zoom lens is widely used. However, as in the above-described conventional example, the number of components in each group is large, and as a result the length of each lens group on the optical axis becomes long, or zooming of each lens group is performed. In addition, when the moving distance in focusing is large and the overall length of the lens is long, a desired retractable length may not be achieved.

In the present invention, in view of these drawbacks of the conventional example,
Particularly, it is suitable for a photographing system using a solid-state imaging device, and provides a compact, small-diameter, high-magnification ratio, high-magnification ratio, excellent optical performance, and optical apparatus zoom lens using the same, which has a small number of constituent lenses. With the goal.

Still another object of the present invention is to provide a zoom lens satisfying at least one of the following items and an optical apparatus using the same.

[0013] Good correction of astigmatism and distortion, especially on the wide-angle side. -To reduce the aberration sharing of the moving lens group while minimizing the lens configuration, to reduce the performance deterioration due to eccentricity between the lens groups due to manufacturing errors, and to facilitate the manufacturing. To provide good image-side telecentric imaging suitable for a photographing system using a solid-state imaging device while minimizing the number of components. The length of each lens unit on the optical axis required for the retractable zoom lens and the amount of movement of each lens unit on the optical axis due to zooming and focusing are shortened. • Correctly correct distortion not only at the wide-angle end but throughout the zoom range. -To reduce the fluctuation of the telecentric imaging on the image side due to zooming.・ Achieve further miniaturization by reducing the amount of movement of the zoom lens unit while maintaining telecentric imaging.・ Simplify the focusing mechanism for near objects.
And so on.

[0014]

According to a first aspect of the present invention, there is provided a zoom lens having a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, and a positive refractive power. In a zoom lens having a third lens group and performing zooming by moving each lens group, the third lens group includes one or two lenses including a positive lens, and the positive lens in the third lens group. The refractive index of the lens material is ndp3 and the Abbe number is νdp
3, the condition is satisfied that ndp3 <1.5 ‥‥‥ (1) νdp3> 70.0 ‥‥‥ (2)

According to a second aspect of the present invention, in the first aspect of the present invention, when the zooming operation is performed from the wide-angle end to the telephoto end, the first zoom lens is moved.
The lens unit moves along a locus convex toward the image side, the second lens unit moves monotonously toward the object side, and the third lens unit moves toward the image side.

According to a third aspect of the present invention, in the first or second aspect, the first lens group includes a negative lens and a positive lens.
The negative lens is characterized in that at least one surface is aspherical.

According to a fourth aspect of the present invention, in the third aspect of the invention, the refractive index of the material of the negative lens in the first lens group is set to n.
When dn1 and Abbe's number are νdn1, the following condition is satisfied: ndn1> 1.70３ (3) νdn1> 35.0 ‥‥‥ (4)

According to a fifth aspect of the present invention, in the first aspect of the present invention, the second lens group includes two sets of cemented lenses.

According to a sixth aspect of the present invention, in the fifth aspect of the present invention, the second lens group includes a positive lens having a convex surface facing the object side and a negative lens having a concave surface facing the image side closest to the object side. 1, the object side lens surface of the positive lens is aspheric, the paraxial radius of curvature of the object side lens surface of the positive lens is R21, and the image side lens surface of the negative lens is When the radius of curvature is R23, the following condition is satisfied: 0.5 <(R21−R23) / (R21 + R23) <0.15 ‥‥‥ (5)

According to a seventh aspect of the present invention, in the fifth or sixth aspect, a positive lens is disposed on the most image side in the second lens group, and the refractive index of the material of the positive lens is ndp2, and the Abbe number is When νdp2 is satisfied, ndp2> 1.70 ‥‥‥ (6) νdp2> 40.0 ‥‥‥ (7) is satisfied.

According to an eighth aspect of the present invention, in the first aspect of the present invention, the third lens group includes one positive lens.

According to a ninth aspect of the present invention, in the invention of the eighth aspect, one positive lens of the third lens group has at least one positive lens.
It is characterized by having two aspheric surfaces.

A tenth aspect of the present invention is characterized in that, in the eighth or ninth aspect, the third lens group is moved to the object side to perform focusing from an object at infinity to an object at a short distance.

According to an eleventh aspect of the present invention, in the invention of any one of the first to tenth aspects, at the telephoto end, the first
Let L be the distance from the object-side vertex of the lens closest to the object side of the lens group to the image plane, and L be the distance from the object-side vertex of the lens closest to the object side of the first lens group. The distance to the image-side vertex of the lens closest to the image side is L1, and the distance from the object-side vertex of the lens closest to the object side of the second lens group is closest to the image side of the second lens group. The distance from the lens to the image-side vertex is L2,
When the distance from the object-side vertex of the lens closest to the object side of the lens group to the image-side vertex of the lens closest to the image side of the third lens group is L3, 0.25 <(L1 + L2 + L3 ) / L <0.45 ‥‥‥ (8).

According to a twelfth aspect of the present invention, in any one of the first to eleventh aspects, the sum of the thicknesses on the optical axis of each lens constituting the second lens group is D2, and When the sum of the air intervals of A is defined as A2, the following condition is satisfied: 0.05 <A2 / D2 <0.2 (9)

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

[0027]

FIG. 1 is a sectional view of a lens according to a first embodiment of the present invention, which will be described later. 2 to 4 are aberration diagrams at the wide-angle end, a middle position, and a telephoto end according to the first embodiment of the present invention.

FIG. 5 is a sectional view of a lens according to a second embodiment of the present invention, which will be described later. 6 to 8 are aberration diagrams at a wide angle end, a middle position, and a telephoto end according to the second embodiment of the present invention.

FIG. 9 is a sectional view of a lens according to a third embodiment of the present invention, which will be described later. 10 to 12 show Embodiment 3 of the present invention.
7 is an aberration diagram at a wide-angle end, a middle position, and a telephoto end of FIG.

FIG. 13 is a schematic view of a main part of an optical apparatus using the zoom lens of the present invention.

In the sectional view of the lens, L1 denotes a first group (first lens group) having a negative refractive power, L2 denotes a second group (second lens group) having a positive refractive power, and L3 denotes a third group having a positive refractive power. A group (third lens group), SP denotes an aperture stop, and IP denotes an image plane. G is a glass block such as a filter or a color separation prism.

Next, the lens configuration of the zoom lens according to the present embodiment will be described.

In the zoom lens of this embodiment, in order from the object side, a first lens unit L1 having a negative refractive power, a second lens unit L2 having a positive refractive power, and a third lens unit L2 having a positive refractive power.
The zoom lens has three lens groups, and moves each lens group during zooming from the wide-angle end to the telephoto end.
Specifically, the first lens group moves reciprocatingly convex toward the image side, the second lens group moves toward the object side, and the third lens group moves toward the image side or moves along a locus convex toward the object side. .

The zoom lens according to the present embodiment performs main zooming by moving the second lens group, and reciprocates the first lens group and moves in the image side direction by the third lens group.
The movement of the image point accompanying the magnification change is corrected by moving along a locus convex toward the object side.

The third lens group is responsible for increasing the refractive power of the photographing lens in accordance with the miniaturization of the image pickup device, and particularly reducing the refractive power of the short zoom system composed of the first and second lens groups. Occurrence of aberrations in the lenses constituting one lens group is suppressed to achieve good optical performance. Particularly, telecentric imaging on the image side required for a photographing apparatus (optical apparatus) using a solid-state imaging device or the like is achieved by giving the third lens group the role of a field lens.

The aperture SP is placed closest to the object side of the second lens group, and the distance between the entrance pupil and the first lens group on the wide-angle side is shortened to increase the outer diameter of the lens constituting the first lens group. And the first lens group and the third lens group cancel out off-axis various aberrations with a stop arranged on the object side of the second lens group, thereby achieving good optical performance without increasing the number of constituent lenses. It has gained.

In the zoom lens of this embodiment, the third lens group has at least one positive lens, and the refractive index and Abbe number of the material of the positive lens satisfy the conditional expressions (1) and (2). It is characterized by things.

The conditional expressions (1) and (2) are mainly for favorably correcting field curvature and lateral chromatic aberration. When the value exceeds the upper limit of conditional expression (1), the Petzval sum increases in the negative direction, and it becomes difficult to correct the field curvature. If the value exceeds the upper limit of conditional expression (2), it becomes difficult to correct lateral chromatic aberration at the telephoto end, which is not preferable.

Although the zoom lens according to the present embodiment achieves the initial purpose by the above configuration, in order to obtain better optical performance or to reduce the size of the entire lens system, the following items are required. It is desirable to satisfy at least one of the conditions.

(A-1) During zooming from the wide-angle end to the telephoto end, the first lens group moves along a locus convex toward the image side, and the second lens group moves monotonously toward the object side. The third lens group moves to the image side.

(A-2) The first lens group is composed of two lenses, a negative lens and a positive lens, and at least one surface of the negative lens is aspheric.

In the zoom lens system according to the present invention, the first lens group having a negative refractive power has a role of focusing the off-axis principal ray on the center of the stop, and refracting the off-axis principal ray on the wide-angle side. Due to the large amount, various off-axis aberrations, particularly astigmatism and distortion, are likely to occur.

In view of this, a concave-convex (negative-positive) configuration is employed in which an increase in the lens diameter closest to the object side is suppressed as in a normal wide-angle lens. More preferably, the image side surface of the negative lens 11 having a meniscus shape is formed as an aspheric surface having a weak negative refractive power around the lens, so that astigmatism and distortion are corrected in a well-balanced manner. The first lens group is composed of a small number of lenses, and the overall size of the lens is reduced.

In the present invention, it is more preferable that each lens constituting the first lens group is centered on a point where the stop and the optical axis intersect in order to suppress occurrence of off-axis aberration caused by refraction of the off-axis principal ray. The shape should be close to a concentric spherical surface.

(A-3) When the refractive index of the material of the negative lens in the first lens group is ndn1 and the Abbe number is νdn1, ndn1> 1.70 {(3) νdn1> 35.0} ‥‥ (4) The following condition must be satisfied.

The conditional expressions (3) and (4) are for achieving both compactness of the entire lens system and good imaging performance.

When the value exceeds the upper limit of conditional expression (3), the Petzval sum of the first lens unit increases in the positive direction, and it becomes difficult to correct the field curvature.

When the value exceeds the upper limit of conditional expression (4),
In particular, it is difficult to correct chromatic aberration of magnification at the wide angle end, which is not preferable.

(A-4) The second lens group is composed of two sets of cemented lenses.

In the present invention, in order to cope with a reduction in the amount of chromatic aberration required with the increase in the number of pixels of a solid-state imaging device such as a CCD and the miniaturization of a cell pitch, two sets of second lens groups are joined. By forming a lens, that is, a first cemented lens in which a meniscus-shaped positive lens 21 and a meniscus-shaped negative lens 22 are joined, and a second cemented lens in which a negative lens 23 and a positive lens 24 are joined, axial chromatic aberration and The chromatic aberration of magnification is well corrected.

The advantage of forming the second lens group by two sets of cemented lenses is that the refractive power of the concave (negative) lens component in the so-called triplet type is separated into two components, and the singlet type like the triplet type is used. By increasing the degree of freedom in aberration correction with respect to the aberration correction method using one concave lens component, correction of off-axis flare, which was corrected by increasing the glass thickness of the concave lens component, and before and after the concave lens component There is no need to correct spherical aberration by using two negative air lenses, and the thickness of the second lens group on the optical axis can be reduced as compared with the triplet type. It contributes to shortening the overall length.

(A-5) The second lens group has a first cemented lens in which a positive lens having a convex surface facing the object side and a negative lens having a concave surface facing the image side are cemented on the most object side. The object-side lens surface of the positive lens is aspherical, and the paraxial radius of curvature of the object-side lens surface of the positive lens is R21, and the radius of curvature of the image-side lens surface of the negative lens is R23. 0.5 <(R21−R23) / (R21 + R23) <0.15 (5)

When the value exceeds the upper limit of conditional expression (5), the Petzval sum of the second lens unit increases in the negative direction, and it becomes difficult to correct the field curvature.

If the lower limit of conditional expression (5) is exceeded, it becomes difficult to correct spherical aberration and coma, which is not preferable.

(A-6) A positive lens is disposed closest to the image in the second lens group. When the refractive index of the material of the positive lens is ndp2 and the Abbe number is νdp2, ndp2> 1.70. ‥‥‥ (6) νdp2> 40.0 ‥‥‥ (7)

When the value exceeds the upper limit of conditional expression (6), the Petzval sum increases in the negative direction, and it becomes difficult to correct the field curvature.
If the value exceeds the upper limit of conditional expression (7), it becomes difficult to correct axial chromatic aberration at the telephoto end, which is not preferable.

(A-7) The third lens group comprises one positive lens.

The third lens group having a positive refractive power is composed of one positive lens 31 having a convex surface on the object side, and also has a role as a field lens for making the image side telecentric. I have.

(A-8) One positive lens of the third lens group has at least one aspheric surface.

In particular, in the present invention, it is preferable to provide an aspheric surface on the image side lens surface of the positive lens 31 whose positive refractive power becomes weak around the lens. According to this, it is possible to favorably correct various off-axis aberrations over the entire zoom range.

(A-9) The third lens group is moved to the object side to perform focusing from an object at infinity to an object at a short distance.

When focusing from an object at infinity to an object at a short distance by using the zoom lens of the present invention, good performance can be obtained by moving the first lens unit to the object side, but more preferably. It is better to move the third lens group to the object side.

This is caused by an increase in the diameter of the front lens and an increase in the load on the actuator caused by moving the first lens unit having the heaviest lens weight, which occurs when the first lens unit disposed closest to the object side is focused. This is because the first lens group and the second lens group can be moved simply during zooming by simply cooperating with a cam or the like, and simplification of the mechanical structure and improvement in accuracy can be achieved.

When focusing is performed by the third lens unit, the third lens unit is moved to the image side during zooming from the wide-angle end to the telephoto end, so that the telephoto end having a large focusing movement amount is moved to the image plane side. , It is possible to minimize the total amount of movement of the third lens unit required for zooming and focusing, thereby achieving a compact lens system as a whole.

(A-10) At the telephoto end, the distance from the object-side vertex of the lens closest to the object side of the first lens group to the image plane is L, and the distance from the vertex of the first lens group to the object side is L. The distance from the object-side vertex of the given lens to the image-side vertex of the lens closest to the image side of the first lens group is L1, and the object side of the second lens group closest to the object side. The distance from the vertex to the image-side vertex of the lens closest to the image side of the second lens group is L2, and the distance from the object-side vertex of the lens closest to the object side of the third lens group is the third position. When the distance from the lens closest to the image side of the lens group to the image-side vertex is L3, by satisfying the following condition: 0.25 <(L1 + L2 + L3) / L <0.45 (8) is there.

If the upper limit of conditional expression (8) is exceeded, the total optical length at the telephoto end will be short, but the total length of each lens unit on the optical axis will be large, which undesirably increases the retractable total length.

If the lower limit of conditional expression (8) is exceeded, the total length on the optical axis of each lens group will be small, but the total optical length at the telephoto end will be long, and the light of each lens group will necessarily be large. Since the amount of movement on the axis increases, the length of a cam ring or the like for moving each lens group increases, and as a result, the overall retracted length is not shortened, which is not preferable.

(A-11) When the total thickness on the optical axis of each lens constituting the second lens group is D2 and the total air space in the second lens group is A2, 0.05 <0.05 A2 / D2 <0.2 ‥‥‥ (9)

When the value exceeds the upper limit of conditional expression (9), the length of the second lens unit on the optical axis becomes long, and it is difficult to make the entire lens system compact, which is not preferable.

If the lower limit of conditional expression (9) is exceeded, the power of the air lens becomes small, making it difficult to satisfactorily correct spherical aberration.

(A-12) The first lens unit having a negative refractive power is composed of a negative meniscus lens 11 having a concave surface facing the image side and a positive meniscus lens 12 having a convex surface facing the object side in order from the object side. A positive lens composed of two lenses or two meniscus negative lenses 11 and 12 having a convex surface facing the object side and a positive meniscus lens 13 having a convex surface facing the object side. Meniscus positive lens 2 having a concave surface facing the image side in order from the object side to the second lens group having a refractive power of
1. Meniscus negative lens 2 with the convex surface facing the object side
2. Meniscus negative lens 2 with the convex surface facing the object side
3. It has four lenses, a positive lens 24 having both lens surfaces convex, and is composed of two sets of cemented lenses in which a positive lens 21 and a negative lens 22 and a negative lens 23 and a positive lens 24 are cemented.
The third lens unit having a positive refractive power is constituted by a positive lens 31 having a convex surface facing the image side or a cemented lens of a negative lens and a positive lens.

According to this, it is possible to easily achieve a compact lens system while maintaining good optical performance.

(A-13) The second lens group having a positive refracting power is to dispose a positive lens 21 having a strong convex surface facing the object side closest to the object side in the lens group. According to this, it is possible to reduce the refraction angle of the off-axis principal ray emitted from the first lens group, and to reduce the occurrence of various off-axis aberrations.

(A-14) Positive lens 2 in the second lens group
Reference numeral 1 denotes a lens having a highest height for passing on-axis rays, and is mainly involved in correcting spherical aberration and coma.

For this reason, it is preferable that the lens surface on the object side of the positive lens 21 be an aspherical surface having a shape in which the positive refractive power becomes weak around the lens. According to this, it becomes easy to satisfactorily correct spherical aberration and coma.

(A-15) The negative lens 22 disposed on the image plane side of the positive lens 21 on the object side in the second lens group has a concave surface on the image side, and the object of the negative lens 23 on the image side that follows. It is preferable to form a negative air lens with the convex surface on the side.
According to this, it is possible to satisfactorily correct the spherical aberration generated with the increase in the aperture ratio.

(A-16) The back focus is sk ',
Assuming that the focal length of the third lens group is f3 and the imaging magnification of the third lens group is β3, the following relationship holds: sk ′ = f3 * (1−β3). Here, it is set so that 0 <β3 <1.0.

When the third lens group is moved to the image side during zooming from the wide-angle end to the telephoto end, the back focus s
k ′ decreases, and the imaging magnification β of the third lens group
3 increases on the telephoto side. Then, as a result, the magnification can be shared by the third lens group, and the amount of movement of the second lens group is reduced, thereby saving space. As a result, the size of the lens system is reduced.

Next, the features of the lens structure of each of Numerical Examples 1 to 3 of the zoom lens according to the present invention will be described.

[Numerical embodiment 1] Numerical embodiment 1 shown in FIG.
Denotes a zoom lens having a magnification ratio of 3 and an aperture ratio of about 2.7 to 4.8.

[Numerical embodiment 2] Numerical embodiment 2 shown in FIG.
In zooming from the wide-angle end to the telephoto end, the first lens group moves reciprocally in a convex shape toward the image side, the second lens group moves toward the object side, and the third lens group moves toward the image side. .

In this embodiment, the first lens group is composed of three lenses, a meniscus-shaped negative lens 11, a meniscus-shaped negative lens 12, and a meniscus-shaped positive lens 13, in order from the object side. Further widening of the angle can be easily achieved with respect to a lens having two lenses in one lens group.

In the numerical example 2, the zoom ratio is 3 times and the aperture ratio is 2.6.
The zoom lens is about 4.8.

[Numerical embodiment 3] Numerical embodiment 3 shown in FIG.
In zooming from the wide-angle end to the telephoto end, the first lens group moves reciprocally in a convex shape toward the image side, the second lens group moves toward the object side, and the third lens group moves toward the image side. .

In this embodiment, the third lens group is a cemented lens composed of a negative meniscus lens and a positive lens having both lens surfaces convex, so that chromatic aberration can be sufficiently reduced together with the two cemented lenses of the second lens group. Has been corrected.

Numerical Example 3 is a zoom lens having a zoom ratio of 3.0 and an aperture ratio of about 2.7 to 4.8.

Hereinafter, numerical examples of the present invention will be described. In the numerical examples, Ri is the radius of curvature of the ith surface in order from the object side, and Di is the ith surface and (i) in order from the object side.
+1) The distance between the surfaces, Ni and νi are the refractive index and Abbe number of the glass of the i-th optical member in order from the object side.

The aspheric surface has an X axis in the optical axis direction, an H axis in a direction perpendicular to the optical axis, a positive traveling direction of light, R represents a paraxial radius of curvature, and each aspheric coefficient represents K, B, C, D. , E, F,

[0089]

(Equation 1)

This is represented by the following equation. Also, for example, "D
The indication " ^-Z " means "10- ^Z ". Table 1 shows the relationship between the above-described conditional expressions and the numerical examples.

[Numerical Example 1] R 1 = 206.343 D 1 = 1.40 N 1 = 1.802238 ν 1 = 40.7 R 2 = 4.841 D 2 = 1.87 R 3 = 9.750 D 3 = 2.00 N 2 = 1.84666 ν 2 = 23.9 R 4 = 49.125 D 4 = Variable R 5 = (Aperture) D 5 = 0.70 R 6 = 4.564 D 6 = 2.00 N 3 = 1.74330 ν 3 = 49.3 R 7 = 10.675 D 7 = 0.80 N 4 = 1.69895 ν 4 = 30.1 R 8 = 3.878 D 8 = 0.72 R 9 = 10.459 D 9 = 0.50 N 5 = 1.84666 ν 5 = 23.9 R10 = 6.339 D10 = 1.80 N 6 = 1.60311 ν 6 = 60.6 R11 = -19.132 D11 = Variable R12 = 14.948 D12 = 1.40 N 7 = 1.48749 ν 7 = 70.2 R13 = -48.563 D13 = variable R14 = ∞ D14 = 2.82 N 8 = 1.51633 ν 8 = 64.1 R15 = ∞ ＼focal length 5.49 10.60 16.18 variable interval＼ D 4 16.12 5.84 2.43 D11 3.93 11.43 19.83 D13 4.20 3.82 2.53 Aspheric coefficient Surface number Curvature KBC 2 4.84094D + 00 -1.84876D + 00 1.10500D-03 -1.66493D-05 DEF 5.13200D-07 -2.00144D-08 3.39222D-10 Surface number Curvature KBC 6 4.56367 D + 00 -1.26047D-01 -2.89482D-04 -9.34418D-06 DE 1.07843D-07 -3.76119D-08 [Numerical example 2] R 1 = 59.735 D 1 = 1.30 N 1 = 1.67470 ν 1 = 54.9 R 2 = 6.518 D 2 = 2.02 R 3 = 21.785 D 3 = 0.80 N 2 = 1.77250 2 = 49.6 R 4 = 8.687 D 4 = 1.48 R 5 = 11.006 D 5 = 2.00 N 3 = 1.84666 ν 3 = 23.9 R 6 = 33.156 D 6 = Variable R 7 = (Aperture) D 7 = 0.80 R 8 = 4.526 D 8 = 2.20 N 4 = 1.74330 ν 4 = 49.3 R 9 = 11.087 D 9 = 0.60 N 5 = 1.69895 ν 5 = 30.1 R10 = 3.873 D10 = 0.75 R11 = 10.369 D11 = 0.50 N 6 = 1.84666 ν 6 = 23.9 R12 = 6.401 D12 = 1.80 N 7 = 1.60311 ν 7 = 60.6 R13 = -19.975 D13 = Variable R14 = 12.110 D14 = 1.50 N 8 = 1.48749 ν 8 = 70.2 R15 = -54.317 D15 = Variable R16 = ∞ D16 = 2.83 N 9 = 1.51633 ν 9 = 64.1 R17 = ∞ ＼focal length 5.00 9.79 14.98 variable interval＼ D 7 14.64 5.46 2.12 D14 4.83 13.24 21.64 D16 3.55 3.02 2.51 Aspherical surface coefficient Surface number Curvature KBC 2 6.51783D + 00 2.42523D-01 -5.97797D-04- 1.56333D-06 DEF -7.09941D-07 2.27735D-08 -6.39051D-10 Surface number Curvature KBC 8 4.52644D + 00 -1.27422D-01 -3.12555D-04 -9.46539D-06 DE 8.23854D-08 -3.89693 D-08 Surface number Curvature KBC 14 1.21103D + 01 0 -1.72597D-04 7.00489D-06 D -1.67824D-07 [Numerical example 3] R 1 = 156.481 D 1 = 1.30 N 1 = 1.80238 ν 1 = 40.7 R 2 = 5.435 D 2 = 1.83 R 3 = 9.697 D 3 = 2.20 N 2 = 1.84666 ν 2 = 23.9 R 4 = 34.098 D 4 = Variable R 5 = (Aperture) D 5 = 0.80 R 6 = 4.588 D 6 = 2.00 N 3 = 1.74330 ν 3 = 49.3 R 7 = 13.399 D 7 = 0.60 N 4 = 1.69895 ν 4 = 30.1 R 8 = 3.929 D 8 = 0.66 R 9 = 11.757 D 9 = 0.60 N 5 = 1.84666 ν 5 = 23.9 R10 = 7.899 D10 = 1.70 N 6 = 1.60311 ν 6 = 60.6 R11 = -20.079 D11 = Variable R12 = 25.476 D12 = 0.50 N 7 = 1.60342 ν 7 = 38.0 R13 = 24.901 D13 = 1.60 N 8 = 1.49700 ν 8 = 81.5 R14 = -25.962 D14 = Variable R15 = ∞ D15 = 2.80 N 9 = 1.51633 ν 9 = 64.1 R16 = ＼ ＼Focal length 5.64 10.99 16.51 variable interval＼ D 5 18.32 6.10 2.69 D12 3.11 9.75 18.27 D15 4.42 4.42 2.54 Aspherical surface number Curvature KBC 2 5.43534D + 00 -2.28361D + 00 1.23160D-03 -2.40093D-05 DEF 8.92996D-07 -2.78071D-08 3.81774D-10 Surface number Curvature KBC 6 4.58844D + 00 -1.27107D-01 -2.62331D-04 -8.61678D-06 DE 1.99209D-07 -3.78975D-08

[0092]

[Table 1]

Next, an embodiment of a video camera (optical apparatus) using the zoom lens of the present invention as a photographing optical system is shown in FIG.
3 will be described.

In FIG. 13, 10 is a video camera body, 11 is a photographing optical system constituted by the zoom lens of the present invention, 12 is an image pickup device such as a CCD for receiving a subject image by the photographing optical system 11, and 13 is an image pickup device Reference numeral 12 denotes a recording unit for recording the received subject image, and reference numeral 14 denotes a finder for observing the subject image displayed on a display element (not shown).

The display element is constituted by a liquid crystal panel or the like, and displays a subject image formed on the image pickup element 12. Reference numeral 15 denotes a liquid crystal display panel having the same function as the finder.

As described above, by applying the zoom lens of the present invention to an optical device such as a video camera, an optical device having a small size and high optical performance can be realized.

[0097]

According to the present invention, it is suitable for a photographing system using a solid-state imaging device, has a small number of constituent lenses, is compact, has a high zoom ratio with a small diameter, and has excellent optical performance. An optical device zoom lens using the same can be achieved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a lens according to a numerical example 1 of the present invention.

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

FIG. 3 is an intermediate aberration diagram of the numerical example 1 of the present invention.

FIG. 4 is an aberration diagram at a telephoto end in Numerical Embodiment 1 of the present invention.

FIG. 5 is a sectional view of a lens according to a numerical example 2 of the present invention.

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

FIG. 7 is an intermediate aberration diagram of the numerical example 2 of the present invention.

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

FIG. 9 is a sectional view of a lens according to a numerical example 3 of the present invention.

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

FIG. 11 is an intermediate aberration diagram of the numerical example 3 of the present invention.

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

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

[Explanation of symbols]

 L1 First group L2 Second group L3 Third group SP Aperture G Glass block IP Image plane d d line g g line ΔS Sagittal image plane ΔM Meridional image plane

 ──────────────────────────────────────────────────続 き Continuing on the front page F term (reference) 2H087 KA02 KA03 MA12 MA14 NA02 NA14 PA05 PA06 PA19 PA20 PB07 PB08 QA02 QA07 QA17 QA21 QA22 QA25 QA34 QA41 QA42 QA45 QA46 RA05 RA12 RA36 RA41 RA43 SA14 SA16 SA64 SB03 SA63 SB SB22 SB23

Claims (13)

[Claims] A first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power. In a zoom lens that performs variable magnification by zooming, the third lens group includes one or two lenses including a positive lens. The refractive index of the material of the positive lens in the third lens group is ndp3, and the Abbe number is νdp.
A zoom lens characterized by satisfying the following condition: ndp3 <1.5 νdp3> 70.0 2. The zooming operation from the wide-angle end to the telephoto end,
2. The apparatus according to claim 1, wherein the first lens group moves along a locus convex toward the image side, the second lens group moves monotonously toward the object side, and the third lens group moves toward the image side. Zoom lens. 3. The zoom lens according to claim 1, wherein said first lens group comprises two lenses, a negative lens and a positive lens, wherein at least one surface of said negative lens is an aspheric surface. . 4. When the refractive index of the material of the negative lens in the first lens group is ndn1 and the Abbe number is νdn1, the following condition is satisfied: ndn1> 1.70 νdn1> 35.0. The zoom lens according to claim 3. 5. The zoom lens according to claim 1, wherein said second lens group includes two sets of cemented lenses. 6. The second lens group has a first cemented lens in which a positive lens having a convex surface facing the object side and a negative lens having a concave surface facing the image side are cemented to the most object side. Is an aspheric surface, and the paraxial radius of curvature of the object side lens surface of the positive lens is R21, and the radius of curvature of the image side lens surface of the negative lens is R23. <(R21-R23) / (R21 + R23) <
The zoom lens according to claim 5, wherein the following condition is satisfied: 0.15. 7. A positive lens is disposed closest to the image in the second lens group, and the material of the positive lens has a refractive index of ndp2,
7. The zoom lens according to claim 5, wherein, when the Abbe number is νdp2, the following condition is satisfied: ndp2> 1.70 νdp2> 40.0. 8. The zoom lens according to claim 1, wherein said third lens group comprises one positive lens. 9. The zoom lens according to claim 8, wherein one positive lens of said third lens group has at least one aspheric surface. 10. The zoom lens according to claim 8, wherein the third lens group is moved to the object side to perform focusing from an object at infinity to an object at a short distance. 11. At the telephoto end, the distance from the object side vertex of the lens closest to the object side of the first lens group to the image plane is L, and the lens closest to the object side of the first lens group is L. L1 is the distance from the object-side vertex of the first lens group to the image-side vertex of the lens disposed closest to the image, and the distance from the object-side vertex of the lens disposed closest to the object of the second lens group is: The distance to the image-side vertex of the lens closest to the image side of the second lens group is L2, and the distance from the object-side vertex of the lens closest to the object side of the third lens group is the third
2. The condition that 0.25 <(L1 + L2 + L3) / L <0.45 is satisfied, where L3 is the distance to the image-side vertex of the lens located closest to the image side of the lens group. 11. The zoom lens according to any one of items 1 to 10. 12. When the sum of the thicknesses of the respective lenses constituting the second lens group on the optical axis is D2 and the sum of the air gaps in the second lens group is A2, 0.05 <A2 / D2. The zoom lens according to any one of claims 1 to 11, wherein a condition of <0.2 is satisfied. 13. An optical apparatus comprising the zoom lens according to claim 1. Description: