JP2006208803A - Zoom lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a zoom lens capable of preventing shading or an insufficient amount of peripheral light. <P>SOLUTION: The zoom lens includes, in order from the object side (subject side) OBJ, a first group 110 having a positive refracting power, a second group 120 having a negative refracting power, a third group 130 having a positive refracting power, and a fourth group 140 having a positive refracting power. Where the focal distance of all the groups at the telephoto end is ft, the focal distance of the first group 110 is f1, the focal distance of the second group 120 is f2, the focal distance of the third group 130 is f3, and the focal distance of the fourth group 140 is f4, the following conditional formulas are satisfied: 1.70<f1/ft<1.75 and -1.15<f3/f2<-1.12. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a zoom lens having a four-group configuration applicable to a digital camera, a video camera, and the like.

  As a zoom lens having a four-group configuration applicable to a digital camera, a video camera, a film camera, and the like, for example, devices disclosed in the following Patent Documents 1, 2, and 3 are known.

  In Patent Document 1, the first group has a positive refractive power, the second group has a negative refractive power, the third group has a positive refractive power, and the fourth group has a positive refractive power. A projection zoom lens having the following is disclosed.

  In Patent Document 2, the first group has a negative refractive power, the second group has a positive refractive power, the third group has a negative refractive power, and the fourth group has a positive refractive power. A projection zoom lens having the following is disclosed.

In Patent Document 3, the first group has a positive refractive power, the second group has a negative refractive power, the third group has a positive refractive power, and the fourth group has a positive refractive power. A projection zoom lens having the following is disclosed.
Japanese Patent Laid-Open No. 10-253484 JP 11-64731 A JP 2003-29147 A

  However, the conventional zoom lens is designed to be compatible with a silver salt film, and when this is used as it is, an image sensor such as a CCD or a CMOS sensor is used, there is a disadvantage in that it causes shading and insufficient peripheral light amount. .

  An object of the present invention is to provide a zoom lens capable of preventing shading and insufficient peripheral light amount.

In order to achieve the above object, a zoom lens according to an aspect of the present invention includes, in order from the subject side, a first group having a positive refractive power, a second group having a negative refractive power, and a third group having a positive refractive power. , And a fourth group having positive refractive power, the focal length of the entire group at the telephoto end is ft, the focal length of the first group is f1, the focal length of the second group is f2, and the third group Where f3 is the focal length and f4 is the focal length of the fourth lens group, the following conditional expression is satisfied.
(Conditional expression)
1.70 <f1 / ft <1.75,
−1.15 <f3 / f2 <−1.12.

  Preferably, in order from the subject side, the first group includes a meniscus concave lens having a convex surface facing the subject side, a cemented lens of a convex lens, and a meniscus convex lens having a convex surface facing the subject side, and the second group includes A concave meniscus lens having a convex surface facing the subject, a concave lens, and a convex meniscus lens having a convex surface facing the subject.The third group includes a convex lens, a cemented lens of a convex lens and a concave lens, and a convex lens. The fourth group consists of a cemented lens of a concave lens and a convex lens.

  Preferably, each of the second group, the third group, and the fourth group includes at least one aspheric lens.

Preferably, the third group includes four lenses including a first lens, a second lens, a third lens, and a fourth lens, and the fourth group includes a fifth lens, and The first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens. When the refractive index is Nd1, Nd2, Nd3, Nd4, Nd5, Nd6 and the dispersion is νd1, νd2, νd3, νd4, νd5, νd6, the following conditional expression is satisfied.
(Conditional expression)
Nd4 <Nd1,
νd1 <νd4,
Nd1 <Nd2,
νd2 <νd1,
Nd5 <Nd6,
νd6 <νd5.

  According to the present invention, it is possible to provide a zoom lens that can prevent shading and insufficient peripheral light amount.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

<First Embodiment>
1, 2 and 3 are diagrams showing a first embodiment of a zoom lens according to the present invention. FIG. 1 shows a lens configuration at a wide angle end (wide), and FIG. FIG. 3 shows the lens configuration at the telephoto end (tele).

As shown in the figure, the zoom lens 100 is arranged in order from the object side (subject side) OBJ, a first group 110 having a positive refractive power, a second group 120 having a negative refractive power, and a positive refraction. The third group 130 having power, the fourth group 140 having positive refractive power, the imaging unit 150, and the diaphragm unit 160 disposed on the object side (second group 120 side) of the third group 130 are configured. .
In the zoom lens 100, when zooming is performed, the first group 110, the second group 120, the third group 130, and the fourth group 140 move on the optical axis AX.
In the zoom lens 100, the distance between the first group 110 and the second group 120 at the telephoto end is larger than that at the wide-angle end, and the distance between the second group 120 and the third group 130 is small. The distance between 130 and the fourth group 140 is increased.
Regarding the scaling function, the first group 110 can be configured to be variable (movable), but the first group 110 can be configured to be fixed.

  In the zoom lens 100 of the present embodiment, the focal length of the entire group at the telephoto end is ft, the focal length of the first group 110 is f1, the focal length of the second group 120 is f2, and the focal length of the third group 130. Where f3 is the focal length of the fourth group 140 and f4 is satisfied, the following conditional expression 1 is satisfied.

(Condition 1)
1.70 <f1 / ft <1.75,
−1.15 <f3 / f2 <−1.12.

  In the zoom lens 100 that satisfies the above conditions, each lens group is configured as follows.

  The first group 110 includes a meniscus concave lens 111 having a convex surface facing the object side (subject side), a cemented lens of a convex lens 112, and a meniscus convex lens 113 having a convex surface facing the object side (subject side).

  The second group 120 includes a meniscus concave lens 121 having a convex surface facing the object side (subject side), a concave lens 122, and a meniscus convex lens 123 having a convex surface facing the object side (subject side).

  The third group 130 includes a convex lens 131 as a first lens, a cemented lens of a convex lens 132 as a second lens and a concave lens 133 as a third lens, and a convex lens 134 as a fourth lens. Has been.

  The fourth group 140 includes a cemented lens of a concave lens 141 as a fifth lens and a convex lens 142 as a sixth lens.

In the imaging unit 150, a glass parallel flat plate (cover glass) 151 and an imaging element 152 made of, for example, a CCD or a CMOS sensor are sequentially arranged from the fourth group 140 side.
Light from the subject (object) through the imaging optical system configured by the first group to the fourth group is imaged on the imaging surface 152 a of the imaging element 152.

As described above, in the present embodiment, each of the second group 120, the third group 130, and the fourth group 140 includes at least one aspheric lens.
Further, in the present embodiment, the third group 130 includes a first lens (convex lens 131), a second lens (convex lens 132), a third lens (concave lens 133), and a fourth lens (convex lens 134). It consists of four lenses.
The fourth group 140 includes a fifth lens (concave lens 141) and a sixth lens (two lenses including a convex lens 142).
The zoom lens 100 according to the present embodiment has refractive indexes of Nd1, Nd2, and Nd3 for the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens, respectively. , Nd4, Nd5, Nd6, and dispersion are νd1, νd2, νd3, νd4, νd5, νd6, the following conditional expression 2 is satisfied.

(Condition 2)
Nd4 <Nd1,
νd1 <νd4,
Nd1 <Nd2,
νd2 <νd1,
Nd5 <Nd6,
νd6 <νd5.

  As described above, the zoom lens 100 according to the present embodiment is arranged in order from the object side (subject side) OBJ, the first group 110 having a positive refractive power, the second group 120 having a negative refractive power, the positive group. A third group 130 having a refractive power of 4 and a fourth group 140 having a positive refractive power, and the third group 130 is composed of four sheets and the fourth group is composed of two sheets. The second group 120 and the third group 130 Since each of the fourth group 140 includes at least one aspherical lens and satisfies the above-described conditional expressions 1 and 2, it is applied to an image sensor such as a CCD or CMOS sensor. Even so, shading can be suppressed, a sufficient amount of peripheral light can be obtained, and various aberrations can be satisfactorily suppressed with a relatively simple configuration.

Examples 1 and 2 according to specific numerical values of the zoom lens 100 are shown below.
In Example 1 and Example 2, the surface numbers as shown in FIG. 1 are provided for the lenses constituting each lens group of the zoom lens 100, the diaphragm 160, and the cover glass constituting the imaging unit 150. Was attached.
Specifically, the object side surface (convex surface) of the meniscus concave lens 111 constituting the first group 110 is No. 1, the opposite concave surface is No. 2, the second group side surface of the convex lens 112 is No. 3, and the meniscus The object side surface (convex surface) of the convex lens 113 is No. 4, the concave surface on the second group side is No. 5, the object side surface (convex surface) of the meniscus concave lens 121 constituting the second group 120 is No. 6, and the concave surface on the opposite side is No. 7, the object-side concave surface of the concave lens 122 is No. 8, the opposite concave surface is No. 9, the object side surface (convex surface) of the meniscus convex lens 123 is No. 10, the opposite concave surface is No. 11, and the aperture 160 No. 12, the object side convex surface of the convex lens 131 constituting the third group 130 is No. 13, the opposite convex surface is No. 14, the object side convex surface of the convex lens 132 is No. 15, the opposite side surface is No. 16, The concave surface on the fourth group side of the concave lens 133 is the 17th, convex No. 18 is the object-side convex surface of No. 134, No. 19 is the opposite convex surface, No. 20 is the object-side concave surface of the concave lens 141 constituting the fourth group 140, No. 21 is the concave surface on the opposite side, and The convex surface on the image sensor side is number 22, the surface on the fourth group side of the cover glass 151 is number 23, and the surface on the image sensor side is number 24.

Example 1
Table 1 shows the radius of curvature (R), interval (D), refractive index (Nd), and dispersion (ν) of each lens, stop, and cover glass corresponding to each surface number of the zoom lens in Example 1. Yes.

  Table 2 shows conic coefficients of the 11th, 13th, and 22nd surfaces.

  Table 3 shows the second, fourth, sixth, eighth, and tenth power data of the eleventh aspherical surface.

  Table 4 shows the second-order, fourth-order, sixth-order, eighth-order, and tenth-order power data of the 13th aspherical surface.

  Table 5 shows the second-order, fourth-order, sixth-order, eighth-order and tenth-order power data of the 22nd aspherical surface.

  Table 6 shows zoom space data.

4A is an aberration diagram showing spherical aberration, astigmatism, and distortion at the wide-angle end (wide) in Example 1, and FIG. 4B is a spherical aberration and astigmatism in normal in Example 1. FIG. FIG. 4C is an aberration diagram illustrating spherical aberration, astigmatism, and distortion aberration at the telephoto end (tele) in Example 1. FIG.
As can be seen from FIGS. 4A to 4C, according to Example 1, spherical, astigmatism, and distortion aberrations are well corrected at the focal length from the wide-angle end to the telephoto end, and imaging performance is improved. An excellent zoom lens can be obtained.

(Example 2)
Table 7 shows the radius of curvature (R), interval (D), refractive index (Nd), and dispersion (ν) of each lens, stop, and cover glass corresponding to each surface number of the zoom lens in Example 2. Yes.

  Table 8 shows conic coefficients of the 11th, 13th, and 22nd surfaces.

  Table 9 shows the second, fourth, sixth, eighth, and tenth power data of the eleventh aspherical surface.

  Table 10 shows the second, fourth, sixth, eighth and tenth power data of the thirteenth aspherical surface.

  Table 11 shows the second-order, fourth-order, sixth-order, eighth-order, and tenth-order power data of the 22nd aspherical surface.

  Table 12 shows zoom space data.

5A is an aberration diagram showing spherical aberration, astigmatism, and distortion at the wide-angle end (wide) in Example 2, and FIG. 5B is a spherical aberration and astigmatism in normal in Example 2. FIG. 5C is an aberration diagram illustrating spherical aberration, astigmatism, and distortion aberration at the telephoto end (tele) in the second embodiment.
As can be seen from FIGS. 5 (a) to 5 (c), according to the first embodiment, spherical, astigmatism and distortion aberrations are well corrected at the focal length from the wide angle end to the telephoto end, and the imaging performance is improved. An excellent zoom lens can be obtained.

It is a figure which shows 1st Embodiment of the zoom lens which concerns on this invention, Comprising: It is a figure which shows the lens structure in a wide angle end. It is a figure which shows 1st Embodiment of the zoom lens which concerns on this invention, Comprising: It is a figure which shows the lens structure in normal. It is a figure which shows 1st Embodiment of the zoom lens which concerns on this invention, Comprising: It is a figure which shows the lens structure in a telephoto end. (A) is an aberration diagram showing spherical aberration, astigmatism, and distortion at the wide angle end (wide) in Example 1, and (b) is a normal spherical aberration, astigmatism in Example 1, FIG. 4C is an aberration diagram showing spherical aberration, astigmatism, and distortion at the telephoto end (tele) in Example 1. FIG. (A) is an aberration diagram showing spherical aberration, astigmatism, and distortion at the wide-angle end (wide) in Example 2, and (b) is spherical aberration, astigmatism, and distortion in normal in Example 2. FIG. 4C is an aberration diagram illustrating aberrations, and FIG. 6C is an aberration diagram illustrating spherical aberration, astigmatism, and distortion at the telephoto end (tele) in the second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Zoom lens 110 ... 1st group 111 ... Meniscus concave lens 112 ... Convex lens 113 ... Meniscus convex lens 120 ... 2nd group 121 ... Meniscus concave lens 122 ... Concave lens 123 ... Meniscus convex lens 130 ... 3rd group 131 ... Convex lens as 1st lens 132 ... Convex lens as second lens 133 ... Concave lens as third lens 134 ... Convex lens as fourth lens 140 ... Fourth group 141 ... Concave lens as fifth lens 142 ... Convex lens as sixth lens 150 ... Imaging unit,
151 ... Cover glass 152 ... Image sensor 160 ... Diaphragm part

Claims (4)

In order from the subject side, a first group having a positive refractive power, a second group having a negative refractive power, a third group having a positive refractive power, and a fourth group having a positive refractive power,
The focal length of the entire group at the telephoto end is ft, the focal length of the first group is f1, the focal length of the second group is f2, the focal length of the third group is f3, and the focal length of the fourth group is f4. Zoom lens that satisfies the following conditional expression.
(Conditional expression)
1.70 <f1 / ft <1.75
−1.15 <f3 / f2 <−1.12 In order from the subject side, the first group is composed of a meniscus concave lens having a convex surface facing the subject side, a cemented lens of a convex lens, and a meniscus convex lens having a convex surface facing the subject side.
The second group includes a meniscus concave lens having a convex surface facing the subject, a concave lens, and a meniscus convex lens having a convex surface facing the subject.
The third group includes a convex lens, a cemented lens of a convex lens and a concave lens, and a convex lens.
The zoom lens according to claim 1, wherein the fourth group includes a cemented lens of a concave lens and a convex lens. The zoom lens according to claim 1, wherein each of the second group, the third group, and the fourth group includes at least one aspheric lens. The third group includes four lenses including a first lens, a second lens, a third lens, and a fourth lens,
The fourth group is composed of two lenses including a fifth lens and a sixth lens,
The refractive indexes of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens are Nd1, Nd2, Nd3, Nd4, Nd5, and Nd6. 4. The zoom lens according to claim 1, wherein when the dispersion is νd1, νd2, νd3, νd4, νd5, and νd6, the following conditional expression is satisfied.
(Conditional expression)
Nd4 <Nd1
νd1 <νd4
Nd1 <Nd2
νd2 <νd1
Nd5 <Nd6
νd6 <νd5

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