JP2007065364A - Zoom lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-performance zoom lens which is compact though it has a high variable power ratio such as about 8 or more, and which can restrain the occurrence of aberration. <P>SOLUTION: A first lens group 110 is constituted by arranging a negative lens 111, a positive lens 112 and a positive lens 113 in order from an object side, and has positive refractive power as a whole. A second lens group 120 is constituted by arranging a negative lens 121, a negative lens 122, a positive lens 123 and a negative lens 124 in order from the object side, and has negative refractive power as a whole. A third lens group 130 is constituted by arranging a positive lens 131, a positive lens 132 and a negative lens 133 in order from the object side, and has positive refractive power as a whole. Both surfaces of the positive lens 131 and the surface on an image surface 160 side of the negative lens 133 are formed to be aspherical. A fourth lens group 140 is constituted by arranging a positive lens 141 and a negative lens 142 in order from the object side, and has positive refractive power as a whole. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a zoom lens mounted on a digital camera or a video camera equipped with an image sensor such as a CCD, and more particularly to a zoom lens having a high zoom ratio of about 8 times or more.

  Conventionally, many zoom lenses having a high zoom ratio of about 8 have been proposed for mounting on digital cameras, video cameras, and the like (see, for example, Patent Documents 1 and 2).

  For example, the zoom lens described in Patent Document 1 includes a zooming unit composed of two groups of a first group having a positive refractive power and a second group having a negative refractive power and movable during zooming in order from the object side. And an imaging system composed of two groups, a third group having a positive refractive power and a fourth group having a positive refractive power and movable for zooming and focusing.

  The third group includes two positive lenses having one convex surface on the object side and one negative lens from the object side, and at least one of the third group lens surfaces from the optical axis. It is an aspheric surface whose positive refractive power becomes weaker as it moves away. The fourth group is composed of only one positive lens, and is an aspheric surface in which the positive refractive power becomes weaker as at least one of the lens surfaces of the fourth group moves away from the optical axis. Further, it is characterized in that the following four conditional expressions for shortening the conjugate of the imaging system and preventing mechanical interference with the zooming system are satisfied.

0.9 <f ₃ / (f _w · _ft ) ^1/2 <1.3
0.5 <| f _3-3 | / f ₃ <0.9
−0.1 <β _4s <0.3
0.7 <β _4t / β _4w <1.5

Where f _w and f _t are the focal lengths of the entire system at the wide-angle end and the telephoto end, f ₃ is the combined focal length of the third lens unit, f _3-3 is the focal length of the negative lens of the third lens unit, and β _4s is the focal length of the entire system ^{_{(f w · f t) 1/2}} , the magnification of the fourth group of the focal point at infinity, beta _4w, a focal length of the entire system beta _4t are respectively f _w, with f _t The magnification of the fourth lens group when focusing on an object point at infinity.

JP-A-5-27167 JP-A-7-20281

  However, conventional techniques such as the zoom lens described in each of the above-mentioned patent documents, when used in a video camera equipped with an image sensor with a large number of pixels, which has become the mainstream in recent years, has a variable magnification from the wide angle end to the telephoto end. There is a problem that it is difficult to satisfactorily correct various aberrations that occur during the process. In particular, the occurrence of various aberrations becomes remarkable at the telephoto end, and the occurrence of chromatic aberration is particularly noticeable. In order to correct this chromatic aberration, the front lens diameter of the zoom lens must be increased to increase the overall length, and another problem arises that the zoom lens becomes larger.

  An object of the present invention is to provide a zoom lens having a simple configuration and a compact size while having a high zoom ratio of about 8 times or more in order to solve the above-described problems caused by the prior art. In addition, it is an object of the present invention to provide a high-performance zoom lens capable of suppressing the occurrence of various aberrations.

In order to solve the above-described problems and achieve the object, a zoom lens according to a first aspect of the present invention includes a first lens group having a positive refractive power, arranged in order from the object side, and a negative refractive power. And a second lens group having a plurality of lens groups, wherein the entire length of the zoom lens is OVL, the focal length at the wide-angle end of the entire zoom lens system is fw, and the entire zoom lens system Where the focal length at the telephoto end is ft, and the focal length of the second lens group is f2.
OVL / fw> 11.8
And ft / | f2 | <8.0
It is characterized by satisfying.

  According to the first aspect of the present invention, it is possible to provide a zoom lens having a short front lens diameter and a short overall length while having a high zoom ratio of about 8 times or more.

A zoom lens according to a second aspect of the present invention includes a plurality of first lens groups having a positive refractive power and a second lens group having a negative refractive power, which are arranged in order from the object side. A zoom lens including a lens group, wherein the entire length of the zoom lens is OVL, the focal length at the wide angle end of the entire zoom lens system is fw, the focal length of the first lens group is f1, and the second lens group Let f2 be the focal length of
OVL / fw> 11.8
And f1 / f2 <−5.1
It is characterized by satisfying.

  According to the second aspect of the present invention, it is possible to provide a zoom lens having a short overall length while having a high zoom ratio of about 8 times or more.

A zoom lens according to a third aspect of the present invention includes a plurality of first lens groups having a positive refractive power and a second lens group having a negative refractive power, which are arranged in order from the object side. A zoom lens configured by a lens group, wherein the entire length of the zoom lens is OVL, the focal length at the wide-angle end of the entire zoom lens system is fw, and the Abbe number of the i-th lens constituting the zoom lens is νd _i ( i = 1, 2, 3,...
OVL / fw> 11.8
And 25 <νd _i <41
It is characterized by satisfying.

  According to the third aspect of the present invention, there is provided a high performance zoom lens having a high zoom ratio of about 8 times or more and having a small front lens diameter and suppressing occurrence of chromatic aberration (particularly on the telephoto end side). Can be provided.

A zoom lens according to a fourth aspect of the present invention includes a plurality of first lens groups having a positive refractive power and a second lens group having a negative refractive power, which are arranged in order from the object side. A zoom lens including a lens group, wherein the entire length of the zoom lens is OVL, the focal length at the wide-angle end of the entire zoom lens system is fw, and the refractive index of the i-th lens constituting the zoom lens is nd _i ( i = 1, 2, 3,...
OVL / fw> 11.8
And nd _i > 1.88
It is characterized by satisfying.

  According to the fourth aspect of the present invention, it is possible to provide a high-performance zoom lens that has a high zoom ratio of about 8 times or more and has a small front lens diameter and suppresses various aberrations. .

A zoom lens according to a fifth aspect of the present invention includes a plurality of first lens groups having a positive refractive power and a second lens group having a negative refractive power, which are arranged in order from the object side. A zoom lens configured by a lens group, wherein the entire length of the zoom lens is OVL, the focal length at the wide-angle end of the entire zoom lens system is fw, the focal length at the telephoto end of the entire zoom lens system is ft, When the focal length of one lens unit is f1, and the focal length of the second lens unit is f2,
OVL / fw> 11.8
And ft / | f2 | <8.0
And f1 / f2 <−5.1
It is characterized by satisfying.

  According to the fifth aspect of the present invention, it is possible to provide a zoom lens having a small front lens diameter and a short overall length while having a high zoom ratio of about 8 times or more.

A zoom lens according to a sixth aspect of the present invention includes a plurality of first lens groups having a positive refractive power and a second lens group having a negative refractive power, which are arranged in order from the object side. A zoom lens configured by a lens group, wherein the entire length of the zoom lens is OVL, the focal length at the wide-angle end of the entire zoom lens system is fw, the focal length at the telephoto end of the entire zoom lens system is ft, When the focal length of the two lens groups is f2, and the Abbe number of the i-th lens constituting the zoom lens is νd _i (i = 1, 2, 3,...),
OVL / fw> 11.8
And ft / | f2 | <8.0
And 25 <νd _i <41
It is characterized by satisfying.

  According to the sixth aspect of the present invention, it is possible to provide a zoom lens having a small front lens diameter and a short overall length while having a high zoom ratio of about 8 times or more. In addition, it is possible to provide a high-performance zoom lens capable of suppressing the occurrence of chromatic aberration (particularly the telephoto end side).

A zoom lens according to a seventh aspect of the present invention includes a plurality of first lens groups having a positive refractive power and a second lens group having a negative refractive power, which are arranged in order from the object side. A zoom lens configured by a lens group, wherein the entire length of the zoom lens is OVL, the focal length at the wide-angle end of the entire zoom lens system is fw, the focal length at the telephoto end of the entire zoom lens system is ft, When the focal length of the two lens groups is f2, and the refractive index of the i-th lens constituting the zoom lens is nd _i (i = 1, 2, 3,...),
OVL / fw> 11.8
And ft / | f2 | <8.0
And nd _i > 1.88
It is characterized by satisfying.

  According to the seventh aspect of the present invention, it is possible to provide a zoom lens having a small front lens diameter and a short overall length while having a high zoom ratio of about 8 times or more. In addition, a high-performance zoom lens that can suppress the occurrence of various aberrations can be provided.

A zoom lens according to an eighth aspect of the present invention includes a plurality of first lens groups having a positive refractive power and a second lens group having a negative refractive power, which are arranged in order from the object side. A zoom lens including a lens group, wherein the entire length of the zoom lens is OVL, the focal length at the wide angle end of the entire zoom lens system is fw, the focal length of the first lens group is f1, and the second lens group Is the focal length of f2 and the Abbe number of the i-th lens constituting the zoom lens is νd _i (i = 1, 2, 3,...),
OVL / fw> 11.8
And f1 / f2 <−5.1
And 25 <νd _i <41
It is characterized by satisfying.

  According to the eighth aspect of the present invention, it is possible to provide a zoom lens having a small front lens diameter and a short total length while having a high zoom ratio of about 8 times or more. In addition, it is possible to provide a high-performance zoom lens capable of suppressing the occurrence of chromatic aberration (particularly the telephoto end side).

A zoom lens according to a ninth aspect of the present invention includes a plurality of first lens groups having a positive refractive power and a second lens group having a negative refractive power, which are arranged in order from the object side. A zoom lens including a lens group, wherein the entire length of the zoom lens is OVL, the focal length at the wide angle end of the entire zoom lens system is fw, the focal length of the first lens group is f1, and the second lens group F2 and the refractive index of the i-th lens constituting the zoom lens is nd _i (i = 1, 2, 3,...),
OVL / fw> 11.8
And f1 / f2 <−5.1
And nd _i > 1.88
It is characterized by satisfying.

  According to the ninth aspect of the present invention, it is possible to provide a zoom lens having a short front lens diameter and a short overall length while having a high zoom ratio of about 8 times or more. In addition, a high-performance zoom lens that can suppress the occurrence of various aberrations can be provided.

A zoom lens according to a tenth aspect of the present invention includes a plurality of first lens groups having a positive refractive power and a second lens group having a negative refractive power, which are arranged in order from the object side. A zoom lens configured by a lens group, wherein the entire length of the zoom lens is OVL, the focal length at the wide-angle end of the entire zoom lens system is fw, and the Abbe number of the i-th lens constituting the zoom lens is νd _i ( i = 1, 2, 3,..., and when the refractive index of the i-th lens constituting the zoom lens is nd _i (i = 1, 2, 3,...),
OVL / fw> 11.8
And 25 <νd _i <41
And nd _i > 1.88
It is characterized by satisfying.

  According to the tenth aspect of the present invention, it is possible to provide a high-performance zoom lens that has a high zoom ratio of about 8 times or more and has a small front lens diameter and can suppress the occurrence of various aberrations. .

A zoom lens according to an eleventh aspect of the present invention includes a plurality of first lens groups having a positive refractive power and a second lens group having a negative refractive power, which are arranged in order from the object side. A zoom lens configured by a lens group, wherein the entire length of the zoom lens is OVL, the focal length at the wide-angle end of the entire zoom lens system is fw, the focal length at the telephoto end of the entire zoom lens system is ft, The focal length of one lens group is f1, the focal length of the second lens group is f2, and the Abbe number of the i-th lens constituting the zoom lens is νd _i (i = 1, 2, 3,...). When
OVL / fw> 11.8
And ft / | f2 | <8.0
And f1 / f2 <−5.1
And 25 <νd _i <41
It is characterized by satisfying.

  According to the eleventh aspect of the present invention, it is possible to provide a zoom lens having a small front lens diameter and a short overall length while having a high zoom ratio of about 8 times or more. In addition, it is possible to provide a high-performance zoom lens capable of suppressing the occurrence of chromatic aberration (particularly the telephoto end side).

A zoom lens according to a twelfth aspect of the present invention includes a plurality of first lens groups having a positive refractive power and a second lens group having a negative refractive power, which are arranged in order from the object side. A zoom lens configured by a lens group, wherein the entire length of the zoom lens is OVL, the focal length at the wide-angle end of the entire zoom lens system is fw, the focal length at the telephoto end of the entire zoom lens system is ft, The focal length of one lens group is f1, the focal length of the second lens group is f2, and the refractive index of the i-th lens constituting the zoom lens is nd _i (i = 1, 2, 3,...). When
OVL / fw> 11.8
And ft / | f2 | <8.0
And f1 / f2 <−5.1
And nd _i > 1.88
It is characterized by satisfying.

  According to the twelfth aspect of the present invention, it is possible to provide a zoom lens having a small front lens diameter and a short overall length while having a high zoom ratio of about 8 times or more. In addition, a high-performance zoom lens that can suppress the occurrence of various aberrations can be provided.

A zoom lens according to a thirteenth aspect of the present invention is a plurality of lens groups including a first lens group having a positive refractive power and a second lens group having a negative refractive power, which are arranged in order from the object side. A zoom lens having the entire length of the zoom lens OVL, the focal length at the wide-angle end of the entire zoom lens system fw, the focal length at the telephoto end of the entire zoom lens system ft, and the second lens The focal length of the group is f2, the Abbe number of the i-th lens constituting the zoom lens is νd _i (i = 1, 2, 3,...), And the refractive index of the i-th lens constituting the zoom lens is nd. _{When i} (i = 1, 2, 3,...),
OVL / fw> 11.8
And ft / | f2 | <8.0
And 25 <νd _i <41
And nd _i > 1.88
It is characterized by satisfying.

  According to the invention of the thirteenth aspect, it is possible to provide a zoom lens having a small front lens diameter and a short overall length while having a high zoom ratio of about 8 times or more. In addition, a high-performance zoom lens that can suppress the occurrence of various aberrations can be provided.

A zoom lens according to a fourteenth aspect of the present invention includes a plurality of first lens groups having a positive refractive power and a second lens group having a negative refractive power, which are arranged in order from the object side. A zoom lens including a lens group, wherein the entire length of the zoom lens is OVL, the focal length at the wide angle end of the entire zoom lens system is fw, the focal length of the first lens group is f1, and the second lens group Is the focal length of f2, the Abbe number of the i-th lens constituting the zoom lens is νd _i (i = 1, 2, 3,...), And the refractive index of the i-th lens constituting the zoom lens is nd _i. (I = 1, 2, 3,...)
OVL / fw> 11.8
And f1 / f2 <−5.1
And 25 <νd _i <41
And nd _i > 1.88
It is characterized by satisfying.

  According to the fourteenth aspect of the present invention, it is possible to provide a zoom lens having a small front lens diameter and a short total length while having a high zoom ratio of about 8 times or more. In addition, a high-performance zoom lens that can suppress the occurrence of various aberrations can be provided.

A zoom lens according to a fifteenth aspect of the present invention includes a plurality of first lens groups having a positive refractive power and a second lens group having a negative refractive power, which are arranged in order from the object side. A zoom lens configured by a lens group, wherein the entire length of the zoom lens is OVL, the focal length at the wide-angle end of the entire zoom lens system is fw, the focal length at the telephoto end of the entire zoom lens system is ft, The focal length of one lens group is f1, the focal length of the second lens group is f2, the Abbe number of the i-th lens constituting the zoom lens is νd _i (i = 1, 2, 3,...), When the refractive index of the i-th lens constituting the zoom lens is nd _i (i = 1, 2, 3,...),
OVL / fw> 11.8
And ft / | f2 | <8.0
And f1 / f2 <−5.1
And 25 <νd _i <41
And nd _i > 1.88
It is characterized by satisfying.

  According to the fifteenth aspect of the present invention, it is possible to provide a zoom lens having a simple configuration and a compact size while having a high zoom ratio of about 8 times or more. In addition, a high-performance zoom lens that can suppress the occurrence of various aberrations can be provided.

  A zoom lens according to a sixteenth aspect of the present invention is the zoom lens according to any one of the first to fifteenth aspects, wherein the first lens group and the second lens group are changed upon zooming from the wide-angle end to the telephoto end. The distance between the lens group is increased.

  According to the sixteenth aspect of the present invention, since zooming can be performed by the first lens group and the second lens group, an increase in the overall length of the zoom lens can be suppressed, and a compact zoom lens can be provided. it can.

  According to the present invention, it is possible to provide a zoom lens having a simple configuration and a compact zoom lens while having a high zoom ratio of about 8 times or more. In addition, it is possible to provide a high-performance zoom lens that can suppress the occurrence of various aberrations.

  Hereinafter, preferred embodiments of the zoom lens according to the present invention will be described in detail.

  The zoom lens according to the embodiment of the present invention includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens having a positive refractive power. It includes a lens group and a fourth lens group having a positive refractive power. In this zoom lens, the second lens group and the fourth lens group are movable, and the first lens group and the third lens group are not movable and are fixed.

  The zoom lens moves the second lens group to the image plane side so that the distance between the first lens group and the second lens group increases during zooming from the wide-angle end to the telephoto end. . In this way, the zoom lens is prevented from being lengthened by moving the minimum necessary lens group and executing zooming. Further, the fourth lens group performs focusing so as to follow a U-turn trajectory that moves to the image side after moving to the object side once upon zooming from the wide-angle end to the telephoto end. For this reason, the space closer to the image plane than the third lens group can be used effectively, and the image forming system of the zoom lens can be reduced in size.

  An object of the present invention is to provide a zoom lens that can be used in a compact digital camera, video camera, or the like. For this purpose, it is necessary not only to reduce the size of the lens, but also to provide high optical performance that matches the performance of a small image sensor with a large number of pixels.

Therefore, first, it is preferable that the following conditional expression is satisfied when the total length of the zoom lens is OVL and the focal length at the wide-angle end of the zoom lens is fw.
OVL / fw> 11.8 (1)

  This conditional expression (1) is an expression that defines conditions for realizing a high zoom ratio of about 8 times or more. If the value of OVL / fw is 11.8 or less, the focal length of each lens group constituting the zoom lens becomes too short, and it is difficult to realize high zoom ratio, which is not preferable.

In general, when a zoom lens is used in a digital camera, a video camera, or the like, a cover glass may be disposed between the surface closest to the image plane of the zoom lens and the image plane. In this case, it is preferable that the following conditional expression is satisfied when the total length of the zoom lens including the cover glass is OVL ′ and the focal length at the wide-angle end of the zoom lens is fw.
OVL ′ / fw> 12.0 (1) ′

Further, when the focal length at the telephoto end of the zoom lens of this embodiment is ft and the focal length of the second lens group is f2, it is preferable that the following conditional expression is satisfied.
ft / | f2 | <8.0 (2)

  Conditional expression (2) is an expression that prescribes conditions for reducing the front lens diameter of the zoom lens and suppressing the overall length. When the value of ft / | f2 | is 8.0 or more, the amount of movement of the second lens group at the time of zooming increases and the front lens diameter also increases, so that the zoom lens can be reduced in size. Disappear.

In the zoom lens according to this embodiment, it is preferable that the following conditional expression is satisfied when the focal length of the first lens group is f1 and the focal length of the second lens group is f2.
f1 / f2 <−5.1 (3)

  Conditional expression (3) is an expression that defines a condition for suppressing the movement amount of the second lens group at the time of zooming and shortening the overall length of the zoom lens. If the value of f1 / f2 is −5.1 or more, the amount of movement of the second lens group at the time of zooming becomes too large, which hinders downsizing of the zoom lens.

Further, when the Abbe number of the i-th lens constituting the zoom lens of this embodiment is νd _i (i = 1, 2, 3,...), It is preferable that the following conditional expression is satisfied.
25 <νd _i <41 (4)

Conditional expression (4) is an expression that defines conditions for reducing the front lens diameter of the zoom lens and suppressing the occurrence of chromatic aberration (particularly, at the telephoto end side). The value of [nu] d _i is the out of the defined range by the conditional expression (4), the front lens diameter of the zoom lens becomes large, sufficient miniaturization can not be achieved. Further, chromatic aberration cannot be corrected sufficiently.

Furthermore, when the refractive index of the i-th lens constituting the zoom lens of this embodiment is nd _i (i = 1, 2, 3,...), It is preferable that the following conditional expression is satisfied.
nd _i > 1.88 (5)

Conditional expression (5) is an expression that defines conditions for reducing the front lens diameter of the zoom lens and suppressing the occurrence of various aberrations. When the value of nd _i is 1.88 or less, the front lens diameter of the zoom lens becomes large, and sufficient miniaturization cannot be achieved. Further, various aberrations cannot be corrected sufficiently.

  The zoom lens according to this embodiment satisfies the above conditional expressions (1) and (2), so that the focal length of each lens group constituting the zoom lens is appropriately set, and the zoom lens can be zoomed at high magnification. In addition to this, the front lens diameter of the zoom lens can be reduced and the overall length can be shortened.

  Further, in addition to the conditional expressions (1) and (2), the conditional expression (3) is further satisfied, so that the movement amount of the second lens group at the time of zooming is suppressed and the total length of the zoom lens is further increased. Can be shortened.

  In addition to the conditional expressions (1) to (3), the above conditional expression (4) is satisfied to further reduce the front lens diameter of the zoom lens and suppress the occurrence of chromatic aberration (particularly the telephoto end side). Will be able to.

  Further, in addition to the conditional expressions (1) to (4), the above conditional expression (5) is further satisfied, whereby the occurrence of various aberrations can be suppressed. For example, it is possible to expect an excellent effect in preventing shading and color misregistration that occurs when a color image sensor is used.

  As described above, the zoom lens according to this embodiment provides a compact and high-performance zoom lens that achieves a high zoom ratio if all the conditional expressions (1) to (5) are satisfied. Can be ideal. However, even if all of the conditional expressions (1) to (5) are not satisfied, it is useful to satisfy some of the conditional expressions (2) to (5) in addition to the conditional expression (1). A zoom lens can be provided.

  For example, in addition to the above-described combinations, by satisfying the conditional expressions (1) and (3), the focal length of each lens group constituting the zoom lens is appropriately set, and high zooming is realized. It is possible to reduce the total length of the zoom lens by suppressing the movement amount of the second lens group during zooming.

  In addition, the zoom lens according to this embodiment satisfies the conditional expressions (1) and (4), so that the focal length of each lens group constituting the zoom lens is appropriately set, and high zooming is realized. In addition, the front lens diameter of the zoom lens can be reduced, and the occurrence of chromatic aberration (particularly on the telephoto end side) can be suppressed.

  In addition, the zoom lens according to this embodiment satisfies the conditional expressions (1) and (5), so that the focal length of each lens group constituting the zoom lens is appropriately set, and high zooming is realized. In addition, the front lens diameter of the zoom lens can be reduced, and the occurrence of various aberrations can be suppressed.

  In the zoom lens according to this embodiment, when a cover glass is disposed between the final surface of the zoom lens and the image plane, the condition (1) is substituted for the conditional expression (1). ) 'Must be satisfied.

  If the zoom lens according to this embodiment includes an aspherical lens, various aberrations can be corrected with a small number of lenses.

  Further, the zoom lens according to this embodiment may be configured by only the first lens group and the second lens group as long as the conditional expressions (1) to (5) are satisfied, as described above. The object of the present invention can be achieved.

  Examples of the present invention will be described below.

Example 1
FIG. 1 is a cross-sectional view along the optical axis showing the configuration of the zoom lens according to Example 1 of the present invention. The zoom lens includes a first lens group 110 having a positive refractive power, a second lens group 120 having a negative refractive power, a third lens group 130 having a positive refractive power, and a positive lens in order from an object side (not shown). A fourth lens group 140 having a refractive power of is arranged. A diaphragm 150 is disposed between the second lens group 120 and the third lens group 130. A cover glass 170 is disposed between the fourth lens group 140 and the image plane 160. The cover glass 170 is not essential and can be omitted.

  The first lens group 110 includes a negative lens 111, a positive lens 112, and a positive lens 113 arranged in order from the object side. The second lens group 120 includes a negative lens 121, a negative lens 122, a positive lens 123, and a negative lens 124 arranged in this order from the object side. The third lens group 130 includes a positive lens 131, a positive lens 132, and a negative lens 133 arranged in order from the object side. Aspheric surfaces are formed on both surfaces (14th surface and 15th surface) of the positive lens 131 and on the side surface (19th surface) of the image surface 160 of the negative lens 133. The fourth lens group 140 includes a positive lens 141 and a negative lens 142 arranged in order from the object side.

  The zoom lens according to Example 1 has a compact lens configuration of 12 elements in 4 groups as described above. A lens arranged at a position that is not easily affected by temperature changes may be molded from a plastic material in order to reduce manufacturing costs. For example, each lens constituting the third lens group 130 and the fourth lens group 140 close to the image plane 160 corresponds to this.

  In this zoom lens, zooming is performed by moving the second lens group 120 in a direction along the optical axis. Specifically, the second lens group 120 is moved toward the image plane 160 so that the distance between the first lens group 110 and the second lens group 120 is increased, thereby changing from the wide-angle end to the telephoto end. Do it twice. In this zoom lens, focusing is performed by moving the fourth lens group 140 in a direction along the optical axis. Specifically, focusing is performed by moving the fourth lens group 140 to the object side and then moving to the image plane 160 side in conjunction with zooming from the wide-angle end to the telephoto end.

  Various numerical data related to the zoom lens according to Example 1 will be described below.

Full length (OVL) of zoom lens of Example 1 = 78.68
Total length (OVL ′) of the zoom lens (including the cover glass 170) of Example 1 = 79.02
Focal length (fw) at the wide angle end of the entire zoom lens system of Embodiment 1 = 6.5
Focal length (ft) at the telephoto end of the entire zoom lens system of Embodiment 1 = 61.75
F number = 3.3
Focal length (f1) of first lens group 110 = 40.4
Focal length (f2) of second lens group 120 = -7.96
Focal length (f3) of the third lens group 130 = 26.50
Focal length (f4) of fourth lens group 140 = 18.1

r ₁ = 52.29
d ₁ = 1.2 nd ₁ = 2.02 νd ₁ = 25.3
r ₂ = 30.63
d ₂ = 4.1 nd ₂ = 1.50 νd ₂ = 81.6
r ₃ = -219.5
d ₃ = 0.2
r ₄ = 27.64
d ₄ = 3.4 nd ₃ = 1.73 νd ₃ = 54.7
r ₅ = 105.76
d ₅ = 0.85 (wide-angle end) to 14.90 (intermediate end) to 23.14 (telephoto end)
r ₆ = 33.71
d ₆ = 0.6 nd ₄ = 1.88 νd ₄ = 40.8
r ₇ = 9.02
d ₇ = 4.04
r ₈ = -23.19
_{d 8 = 0.6 nd 5 = 1.59} νd 5 = 61.3
r ₉ = 11.08
d ₉ = 2.3 nd ₆ = 1.85 νd ₆ = 23.8
r ₁₀ = 338.43
d ₁₀ = 1.83
r ₁₁ = -12.33
d ₁₁ = 0.8 nd ₇ = 1.49 νd ₇ = 70.4
r ₁₂ = -66.12
d ₁₂ = 24.17 (wide-angle end) to 10.13 (intermediate end) to 1.89 (telephoto end)
r ₁₃ = ∞ (aperture)
d ₁₃ = 1.6
r ₁₄ = 8.01 (aspherical surface)
d ₁₄ = 2.2 nd ₈ = 1.58 νd ₈ = 59.5
r ₁₅ = -111.8 (aspherical surface)
d ₁₅ = 0.3
r ₁₆ = 9.78
d ₁₆ = 1.6 nd ₉ = 1.49 νd ₉ = 81.6
r ₁₇ = 40.77
d ₁₇ = 0.6 nd ₁₀ = 1.88 νd ₁₀ = 40.8
r ₁₈ = 6.80
d ₁₈ = 8.79 (wide-angle end) to 4.12 (intermediate end) to 6.83 (telephoto end)
r ₁₉ = 15.36 (aspherical surface)
d ₁₉ = 3.5 nd ₁₁ = 1.58 νd ₁₁ = 59.5
r ₂₀ = -11.04
d ₂₀ = 2.0 nd ₁₂ = 1.92 νd ₁₂ = 20.9
r ₂₁ = -18.38
d ₂₁ = 2.83 (wide-angle end) to 7.50 (intermediate end) to 4.77 (telephoto end)
r ₂₂ = ∞
d ₂₂ = 1.0 nd ₁₃ = 1.52 νd ₁₃ = 64.2
r ₂₃ = ∞
d ₂₃ = 10.0

Cone coefficient (ε) and aspheric coefficient (A, B, C, D, E)
(14th page)
ε = 1, A = 0,
B = -6.78 × 10 ^-5 , C = -5.80 × 10 ^-6 ,
D = 3.46 × 10 ^-7 , E = -1.05 × 10 ^-9
(15th page)
ε = 1, A = 0,
B = 1.31 × 10 ⁻⁴ , C = −5.70 × 10 ⁻⁶ ,
^{D = 5.02 × 10 -7, E} = -3.33 × 10 -9
(19th page)
ε = 1, A = 0,
B = -7.21 × 10 ^-5 , C = 1.57 × 10 ^-6 ,
D = -8.79 × 10 ^-8 , E = 1.82 × 10 ^-9

  FIG. 2 is an aberration diagram at the wide-angle end of the zoom lens according to Example 1. FIG. 3 is an aberration diagram at an intermediate end of the zoom lens according to the first example. FIG. 4 is an aberration diagram at the telephoto end of the zoom lens according to the first example.

(Example 2)
FIG. 5 is a cross-sectional view along the optical axis showing the configuration of the zoom lens according to Example 2 of the present invention. The zoom lens includes a first lens group 210 having a positive refractive power, a second lens group 220 having a negative refractive power, a third lens group 230 having a positive refractive power, and a positive lens in order from an object side (not shown). A fourth lens group 240 having a refractive power of is arranged. A stop 250 is disposed between the second lens group 220 and the third lens group 230. A cover glass 270 is disposed between the fourth lens group 240 and the image plane 260. The cover glass 270 is not essential and can be omitted.

  The first lens group 210 includes a negative lens 211, a positive lens 212, and a positive lens 213 arranged in order from the object side. The second lens group 220 includes a negative lens 221, a negative lens 222, and a positive lens 223 arranged in this order from the object side. The third lens group 230 includes a positive lens 231, a positive lens 232, and a negative lens 233 arranged in order from the object side. Aspherical surfaces are formed on both surfaces (the 13th surface and the 14th surface) of the positive lens 231 and the image surface 260 side surface (the 18th surface) of the negative lens 233. The fourth lens group 240 includes a positive lens 241 and a negative lens 242 arranged in this order from the object side.

  The zoom lens according to Example 2 has a compact lens configuration of 11 elements in 4 groups as described above. Therefore, compared with Example 1, the manufacturing cost is reduced by one lens. In addition, a lens arranged at a position that is not easily affected by temperature changes may be molded from a plastic material in order to reduce manufacturing costs. For example, each lens constituting the third lens group 230 and the fourth lens group 240 close to the image plane 260 corresponds to this.

  In this zoom lens, zooming is performed by moving the second lens group 220 in a direction along the optical axis. Specifically, the second lens group 220 is moved to the image plane 260 side so that the distance between the first lens group 210 and the second lens group 220 is increased, thereby changing from the wide-angle end to the telephoto end. Do it twice. In this zoom lens, focusing is performed by moving the fourth lens group 240 in a direction along the optical axis. Specifically, in conjunction with zooming from the wide-angle end to the telephoto end, the fourth lens group 240 is once moved to the object side and then moved to the image plane 260 side to perform focusing.

  Various numerical data related to the zoom lens according to Example 2 will be described below.

Total length (OVL) of zoom lens of Example 2 = 78.42
Full length (OVL ′) of zoom lens (including cover glass 270) of Example 2 = 78.8
Focal length (fw) at the wide-angle end of the entire zoom lens system of Example 2 = 6.5
Focal length (ft) at the telephoto end of the entire zoom lens system of Embodiment 2 = 61.1
F number = 3.3
Focal length (f1) of the first lens group 210 = 42.9
Focal length (f2) of the second lens group 220 = −8.9
Focal length (f3) of the third lens group 230 = 23.7
Focal length (f4) of the fourth lens group 240 = 20.0

r ₁ = 48.60
d ₁ = 1.15 nd ₁ = 1.91 νd ₁ = 31.3
r ₂ = 26.64
d ₂ = 5.26 nd ₂ = 1.49 νd ₂ = 70.44
r ₃ = -605.28
d ₃ = 0.2
r ₄ = 25.27
d ₄ = 3.5 nd ₃ = 1.62 νd ₃ = 63.39
r ₅ = 116.60
d ₅ = 0.8 (wide-angle end) to 16.13 (intermediate end) to 26.25 (telephoto end)
r ₆ = 62.95
_{d 6 = 0.6 nd 4 = 1.83} νd 4 = 42.72
r ₇ = 7.19
d ₇ = 3.0
r ₈ = -26.91
d ₈ = 0.6 nd ₅ = 1.62 νd ₅ = 63.39
r ₉ = 18.15
d ₉ = 0.8
r ₁₀ = 13.83
d ₁₀ = 2.10 nd ₆ = 1.92 νd ₆ = 20.88
r ₁₁ = 43.60
d ₁₁ = 27.95 (wide-angle end) to 12.62 (intermediate end) to 2.50 (telephoto end)
r ₁₂ = ∞ (aperture)
d ₁₂ = 1.65
r ₁₃ = 12.75 (aspherical surface)
d ₁₃ = 1.95 nd ₇ = 1.58 νd ₇ = 59.46
r ₁₄ = -29.74 (aspherical surface)
d ₁₄ = 0.15
r ₁₅ = 8.02
d ₁₅ = 2.89 nd ₈ = 1.49 νd ₈ = 81.61
r ₁₆ = -140.90
d ₁₆ = 0.6 nd ₉ = 1.88 νd ₉ = 40.8
r ₁₇ = 7.47
d ₁₇ = 8.74 (wide-angle end) to 4.25 (intermediate end) to 6.84 (telephoto end)
r ₁₈ = 20.01 (aspherical surface)
d ₁₈ = 3.69 nd ₁₀ = 1.58 νd ₁₀ = 59.46
r ₁₉ = -7.43
d ₁₉ = 0.6 nd ₁₁ = 1.90 νd ₁₁ = 31.3
r ₂₀ = -13.84
d ₂₀ = 6.94 (wide-angle end) to 11.43 (intermediate end) to 8.85 (telephoto end)
r ₂₁ = ∞
d ₂₁ = 1.0 nd ₁₃ = 1.51 νd ₁₃ = 64.2
r ₂₂ = ∞
d ₂₂ = 4.89

Cone coefficient (ε) and aspheric coefficient (A, B, C, D, E)
(13th page)
ε = 1, A = 0,
B = 6.51 × 10 ⁻⁸ , C = −3.41 × 10 ⁻⁶ ,
D = 3.76 × 10 ^-7 , E = -1.63 × 10 ^-8
(14th page)
ε = 1, A = 0,
B = 7.16 × 10 ⁻⁵ , C = −4.72 × 10 ⁻⁶ ,
D = -5.33 × 10 ^-7 , E = -2.25 × 10 ^-8
(18th page)
ε = 1, A = 0,
^{B = -1.14 × 10 -6, C} = 3.48 × 10 -6,
D = -1.61 × 10 ^-7 , E = 3.79 × 10 ^-9

  FIG. 6 is an aberration diagram at the wide-angle end of the zoom lens according to Example 2. FIG. 7 is an aberration diagram at an intermediate end of the zoom lens according to the second example. FIG. 8 is an aberration diagram of the zoom lens according to Example 2 at the telephoto end.

In the above numerical data, r _1, r _2, · · · · each lens, the curvature of such diaphragm surface radius, d _1, d _2, · · · · each lens, such as a diaphragm thickness or their The distance between the surfaces, nd ₁ , nd ₂ ,... Indicates the refractive index of the d-line of each lens, and νd ₁ , νd ₂ ,.

  Each of the aspherical shapes is expressed by the following expression when the X axis is in the optical axis direction, the H axis is in the direction perpendicular to the optical axis, and the light traveling direction is positive.

  Here, r is a paraxial radius of curvature, ε is a conical coefficient, and A, B, C, D, and E are second-order, fourth-order, sixth-order, eighth-order, and tenth-order aspheric coefficients, respectively.

  As described above, the zoom lens according to this embodiment satisfies the above conditional expression, and thus has a simple and compact configuration while having a high zoom ratio of about 8 times or more. Furthermore, a high-performance zoom lens capable of suppressing the occurrence of various aberrations. This can be expected to be particularly effective in preventing shading and color misregistration that occur when used in video cameras and digital cameras equipped with an image sensor with a large number of pixels, which has become the mainstream in recent years.

  In addition, since the zoom lens of this embodiment includes a lens having an aspherical surface, various aberrations can be favorably corrected with a small number of lenses.

  In addition, since the lenses constituting the third lens group and the fourth lens group, which are arranged at positions that are not easily affected by temperature changes, are molded from a plastic material, the manufacturing cost can be reduced.

  As described above, the zoom lens of the present invention is useful for a compact digital camera, a video camera, and the like, and is particularly suitable when a small size and high optical performance are required.

It is sectional drawing which follows the optical axis which shows the structure of the zoom lens concerning Example 1 of this invention. FIG. 6 is an aberration diagram at a wide-angle end of the zoom lens according to Example 1; FIG. 6 is an aberration diagram at an intermediate end of the zoom lens according to Example 1; FIG. 6 is an aberration diagram at a telephoto end of a zoom lens according to Example 1; It is sectional drawing which follows the optical axis which shows the structure of the zoom lens concerning Example 2 of this invention. FIG. 6 is an aberration diagram at a wide angle end of a zoom lens according to Example 2; FIG. 6 is an aberration diagram at an intermediate end of the zoom lens according to Example 2; FIG. 6 is an aberration diagram at a telephoto end of a zoom lens according to Example 2;

Explanation of symbols

110, 210 First lens group 120, 220 Second lens group 130, 230 Third lens group 140, 240 Fourth lens group 150, 250 Diaphragm 160, 260 Image surface 170, 270 Cover glass 111, 121, 122, 124, 133, 142, 211, 221, 222, 233, 242 Negative lens 112, 113, 123, 131, 132, 141, 212, 213, 223, 231, 232, 241 Positive lens

Claims (16)

A zoom lens composed of a plurality of lens groups including a first lens group having a positive refractive power and a second lens group having a negative refractive power, arranged in order from the object side,
When the overall length of the zoom lens is OVL, the focal length at the wide-angle end of the entire zoom lens system is fw, the focal length at the telephoto end of the entire zoom lens system is ft, and the focal length of the second lens group is f2.
OVL / fw> 11.8
And ft / | f2 | <8.0
A zoom lens characterized by satisfying A zoom lens composed of a plurality of lens groups including a first lens group having a positive refractive power and a second lens group having a negative refractive power, arranged in order from the object side,
When the total length of the zoom lens is OVL, the focal length at the wide angle end of the entire zoom lens system is fw, the focal length of the first lens group is f1, and the focal length of the second lens group is f2.
OVL / fw> 11.8
And f1 / f2 <−5.1
A zoom lens characterized by satisfying A zoom lens composed of a plurality of lens groups including a first lens group having a positive refractive power and a second lens group having a negative refractive power, arranged in order from the object side,
The total length of the zoom lens is OVL, the focal length at the wide angle end of the entire zoom lens system is fw, and the Abbe number of the i-th lens constituting the zoom lens is νd _i (i = 1, 2, 3,...) And when
OVL / fw> 11.8
And 25 <νd _i <41
A zoom lens characterized by satisfying A zoom lens composed of a plurality of lens groups including a first lens group having a positive refractive power and a second lens group having a negative refractive power, arranged in order from the object side,
The total length of the zoom lens is OVL, the focal length at the wide-angle end of the entire zoom lens system is fw, and the refractive index of the i-th lens constituting the zoom lens is nd _i (i = 1, 2, 3,...) And when
OVL / fw> 11.8
And nd _i > 1.88
A zoom lens characterized by satisfying A zoom lens composed of a plurality of lens groups including a first lens group having a positive refractive power and a second lens group having a negative refractive power, arranged in order from the object side,
The overall length of the zoom lens is OVL, the focal length at the wide-angle end of the entire zoom lens system is fw, the focal length at the telephoto end of the entire zoom lens system is ft, the focal length of the first lens group is f1, the second When the focal length of the lens group is f2,
OVL / fw> 11.8
And ft / | f2 | <8.0
And f1 / f2 <−5.1
A zoom lens characterized by satisfying A zoom lens composed of a plurality of lens groups including a first lens group having a positive refractive power and a second lens group having a negative refractive power, arranged in order from the object side,
The overall length of the zoom lens is OVL, the focal length at the wide-angle end of the entire zoom lens system is fw, the focal length at the telephoto end of the entire zoom lens system is ft, the focal length of the second lens group is f2, and the zoom lens When the Abbe number of the i-th lens constituting νd _i (i = 1, 2, 3,...),
OVL / fw> 11.8
And ft / | f2 | <8.0
And 25 <νd _i <41
A zoom lens characterized by satisfying A zoom lens composed of a plurality of lens groups including a first lens group having a positive refractive power and a second lens group having a negative refractive power, arranged in order from the object side,
The overall length of the zoom lens is OVL, the focal length at the wide-angle end of the entire zoom lens system is fw, the focal length at the telephoto end of the entire zoom lens system is ft, the focal length of the second lens group is f2, and the zoom lens When the refractive index of the i-th lens constituting nd is nd _i (i = 1, 2, 3, ...),
OVL / fw> 11.8
And ft / | f2 | <8.0
And nd _i > 1.88
A zoom lens characterized by satisfying A zoom lens composed of a plurality of lens groups including a first lens group having a positive refractive power and a second lens group having a negative refractive power, arranged in order from the object side,
The zoom lens is configured by OVL, the focal length of the zoom lens system at the wide angle end is fw, the focal length of the first lens group is f1, and the focal length of the second lens group is f2. When the Abbe number of the i-th lens is νd _i (i = 1, 2, 3,...),
OVL / fw> 11.8
And f1 / f2 <−5.1
And 25 <νd _i <41
A zoom lens characterized by satisfying A zoom lens composed of a plurality of lens groups including a first lens group having a positive refractive power and a second lens group having a negative refractive power, arranged in order from the object side,
The zoom lens is configured by OVL, the focal length of the zoom lens system at the wide angle end is fw, the focal length of the first lens group is f1, and the focal length of the second lens group is f2. When the refractive index of the i-th lens is nd _i (i = 1, 2, 3,...),
OVL / fw> 11.8
And f1 / f2 <−5.1
And nd _i > 1.88
A zoom lens characterized by satisfying A zoom lens composed of a plurality of lens groups including a first lens group having a positive refractive power and a second lens group having a negative refractive power, arranged in order from the object side,
The total length of the zoom lens is OVL, the focal length at the wide angle end of the entire zoom lens system is fw, and the Abbe number of the i-th lens constituting the zoom lens is νd _i (i = 1, 2, 3,...) When the refractive index of the i-th lens constituting the zoom lens is nd _i (i = 1, 2, 3,...),
OVL / fw> 11.8
And 25 <νd _i <41
And nd _i > 1.88
A zoom lens characterized by satisfying A zoom lens composed of a plurality of lens groups including a first lens group having a positive refractive power and a second lens group having a negative refractive power, arranged in order from the object side,
The overall length of the zoom lens is OVL, the focal length at the wide-angle end of the entire zoom lens system is fw, the focal length at the telephoto end of the entire zoom lens system is ft, the focal length of the first lens group is f1, the second When the focal length of the lens group is f2, and the Abbe number of the i-th lens constituting the zoom lens is νd _i (i = 1, 2, 3,...),
OVL / fw> 11.8
And ft / | f2 | <8.0
And f1 / f2 <−5.1
And 25 <νd _i <41
A zoom lens characterized by satisfying A zoom lens composed of a plurality of lens groups including a first lens group having a positive refractive power and a second lens group having a negative refractive power, arranged in order from the object side,
The overall length of the zoom lens is OVL, the focal length at the wide-angle end of the entire zoom lens system is fw, the focal length at the telephoto end of the entire zoom lens system is ft, the focal length of the first lens group is f1, the second When the focal length of the lens group is f2, and the refractive index of the i-th lens constituting the zoom lens is nd _i (i = 1, 2, 3,...),
OVL / fw> 11.8
And ft / | f2 | <8.0
And f1 / f2 <−5.1
And nd _i > 1.88
A zoom lens characterized by satisfying A zoom lens composed of a plurality of lens groups including a first lens group having a positive refractive power and a second lens group having a negative refractive power, arranged in order from the object side,
The overall length of the zoom lens is OVL, the focal length at the wide-angle end of the entire zoom lens system is fw, the focal length at the telephoto end of the entire zoom lens system is ft, the focal length of the second lens group is f2, and the zoom lens Νd _i (i = 1, 2, 3,...) And the refractive index of the i-th lens constituting the zoom lens are nd _i (i = 1, 2, 3,...). ...)
OVL / fw> 11.8
And ft / | f2 | <8.0
And 25 <νd _i <41
And nd _i > 1.88
A zoom lens characterized by satisfying A zoom lens composed of a plurality of lens groups including a first lens group having a positive refractive power and a second lens group having a negative refractive power, arranged in order from the object side,
The zoom lens is configured by OVL, the focal length of the zoom lens system at the wide angle end is fw, the focal length of the first lens group is f1, and the focal length of the second lens group is f2. The Abbe number of the i-th lens is νd _i (i = 1, 2, 3,...), And the refractive index of the i-th lens constituting the zoom lens is nd _i (i = 1, 2, 3,...). )
OVL / fw> 11.8
And f1 / f2 <−5.1
And 25 <νd _i <41
And nd _i > 1.88
A zoom lens characterized by satisfying A zoom lens composed of a plurality of lens groups including a first lens group having a positive refractive power and a second lens group having a negative refractive power, arranged in order from the object side,
The overall length of the zoom lens is OVL, the focal length at the wide-angle end of the entire zoom lens system is fw, the focal length at the telephoto end of the entire zoom lens system is ft, the focal length of the first lens group is f1, the second The focal length of the lens group is f2, the Abbe number of the i-th lens constituting the zoom lens is νd _i (i = 1, 2, 3,...), And the refractive index of the i-th lens constituting the zoom lens is When nd _i (i = 1, 2, 3,...),
OVL / fw> 11.8
And ft / | f2 | <8.0
And f1 / f2 <−5.1
And 25 <νd _i <41
And nd _i > 1.88
A zoom lens characterized by satisfying The zoom lens according to any one of claims 1 to 15, wherein an interval between the first lens group and the second lens group is increased during zooming from the wide-angle end to the telephoto end.

Images