JP2006220715A - Zoom lens and imaging apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a satisfactorily compact zoom lens of excellent optical characteristics, the lens which has a power variation ratio of about 3, and is improved in terms of a manufacturing error and reduced in manufacturing cost. <P>SOLUTION: The zoom lens is constituted of a 1st negative lens group G1, a 2nd positive lens group G2 and a 3rd positive lens group G3, wherein the power is varied by varying a distance between respective lens groups. The 1st lens group G1 is constituted of two negative and positive lenses, the 2nd lens group G2 is constituted of two positive lenses and one negative lens, the 3rd lens group G3 is constituted of one positive lens. Provided that n<SB>1</SB>denotes the refractive index of the negative lens in the 1st lens group G1, n<SB>2</SB>denotes the refractive index of the positive lens in the 1st lens group G1, n<SB>1</SB>>1.8 and n<SB>2</SB>>1.8 are satisfied. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a zoom lens and an imaging apparatus using the same, and more particularly to a three-group zoom lens having a solid-state imaging element suitable for a compact digital camera and an imaging apparatus using the same.

  Conventionally, digital cameras and video cameras are required to have high image quality and low cost, similar to those used for general cameras. For example, a zoom lens suitable for a solid-state imaging device is disclosed in Patent Document 1 as a three-group zoom lens, and in order from the object side, a first lens group having a negative refractive power and a second lens group having a positive refractive power. A three-group zoom lens system having three lens groups of a third lens group having a positive refractive power and performing zooming by moving the first lens group and the second lens group from the wide-angle end to the telephoto end is there.

  However, the optical system disclosed in Patent Document 1 has a relatively large number of lenses, such as seven, and curvature of field occurs when the thickness of the cemented lens of the second lens group changes even a little, and the manufacturing cost is low. It has disadvantages such as high.

  Another zoom lens is disclosed in Patent Document 2 as a three-group zoom lens. In order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a positive refractive power. This is a three-group zoom lens system that has three lens groups of the third lens group and performs zooming by moving the first lens group and the second lens group from the wide-angle end to the telephoto end. Although this zoom lens system has a zoom ratio of about 3 times, the number of lenses is small as 6 elements in 5 groups and still has a brightness of an aperture ratio of 1: 2.8 or more at the wide angle end. Are better.

However, the optical system disclosed in Patent Document 2 has a thick lens alone and a long total length with respect to the focal length, and is still not satisfactory in terms of compactness when the lens is housed.
JP 2001-318311 A JP 2003-140041 A

  The present invention has been made in view of such problems of the prior art, and it is a first object to provide a zoom lens having an appropriate zoom ratio, sufficiently compact and having excellent optical characteristics. Objective. It is a second object of the present invention to provide a zoom lens that is low in manufacturing cost, sufficiently compact, and has excellent optical characteristics by making it resistant to manufacturing errors.

The first zoom lens of the present invention that achieves the above object comprises, in order from the object side, 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 the zoom lens that changes the magnification by changing the interval between the lens groups,
The first lens group includes two negative lenses and a positive lens, the second lens group includes two positive lenses and one negative lens, and the third lens group includes one positive lens. And satisfying the following conditional expression.

n ₁ > 1.8 (1-1)
n ₂ > 1.8 (1-2)
Here, n ₁ is the refractive index of the negative lens of the first lens group, and n ₂ is the refractive index of the positive lens of the first lens group.

  Hereinafter, the reason and action of the above configuration in the first zoom lens of the present invention will be described.

  By adopting a three-group zoom lens type with negative and positive refractive power arrangement and the above-mentioned configuration of each lens group, a thin zoom lens with a zoom ratio of about 3 times maintaining sufficient telecentricity can be obtained. It will be advantageous.

  By making the first lens group into two lenses, a negative lens and a positive lens, it becomes easier to reduce the size and correct the aberration.

  Since the second lens group is a group that tends to have a strong refractive power, it is easy to reduce the size of the second lens group and correct aberrations by adopting a three-lens configuration of two positive lenses and one negative lens. Become.

  In addition, in order to make the lens compact in a compact manner while obtaining an appropriate zoom ratio, it is easy to ensure telecentricity and correct the image plane by using a single positive lens in the third lens group.

  Conditional expressions (1-1) and (1-2) are conditions for reducing the size of the first lens unit while suppressing the occurrence of aberrations while ensuring the refractive power.

  In the first lens group, off-axis rays are incident at a wide angle at the wide angle end. Therefore, it is preferable in terms of aberration correction that the negative lens and the positive lens have a meniscus shape with a strong convex surface facing the object side. On the other hand, when such a shape is taken, the thickness of the first lens group tends to increase.

  Therefore, the refractive index of the two lenses constituting the first lens group is increased and the thickness of the first lens group is decreased so that the conditional expressions (1-1) and (1-2) are simultaneously satisfied. ing.

  Exceeding the lower limit of 1.8 to the conditional expressions (1-1) and (1-2) is not preferable from the viewpoint of compactness because a large curvature must be given to the lens in order to obtain sufficient power.

  It is more preferable to specify an upper limit value 2.3 (<2.3) in conditional expressions (1-1) and (1-2) to prevent the lens material from becoming expensive.

  According to a second zoom lens of the present invention, in the first zoom lens, the first lens group includes, in order from the object side, a negative lens having a concave surface on the image surface side and a positive lens having a convex surface on the object side. And satisfies the following conditions.

0.3 <| f _1G / R ₁ + f _1G / R ₃ + f _1G / R ₄ | <1.9 (A)
Where f _1G is the focal length of the first lens group,
R ₁ is the absolute value of the paraxial radius of curvature of the object side surface of the first lens unit negative lens;
R ₃ is the absolute value of the paraxial radius of curvature of the object side surface of the first lens unit positive lens;
R ₄ is the absolute value of the paraxial radius of curvature of the image side surface of the first lens unit positive lens;
It is.

  Hereinafter, the reason and action of the second zoom lens according to the present invention having the above configuration will be described.

  The first lens group includes, in order from the object side, a negative lens having a concave surface facing the image surface side and a positive lens having a convex surface facing the object side, so that the incident angles of off-axis light on these surfaces Can be reduced, which is advantageous for off-axis aberration correction.

  Conditional expression (A) specifies the radius of curvature of the object side surface of the first lens group negative lens, the object side surface of the positive lens, and the image surface side surface.

  If the lower limit of 0.3 in conditional expression (A) is exceeded, the curvature of the three surfaces will be too small, and it will be difficult to correct off-axis aberrations at the wide-angle end.

  If the upper limit value 1.9 of conditional expression (A) is exceeded, the power of any one of the first, third, and fourth lens surfaces of the first lens group becomes strong, which is disadvantageous for downsizing of the first lens group. In addition, aberration fluctuations due to decentration increase.

  Furthermore, it is preferable in terms of aberration correction that the lower limit value is 0.5, and further 0.7.

  Further, when the upper limit is set to 1.6, and further to 1.4, it is preferable for reducing aberration variation due to downsizing and decentration.

  According to a third zoom lens of the present invention, in the first and second zoom lenses, the two lenses in the first lens group have a positioning portion for relative positioning of the lenses, and the positioning portion. In the above, the lenses are in contact with each other and a space is sandwiched within the effective diameter.

  The reason and operation of the third zoom lens according to the present invention will be described below.

  Since the two lenses are in contact with each other at the positioning portion, a frame for fixing the lens is not necessary, so that a manufacturing error of the frame does not affect the relative relationship between the lenses. As a result, the error in the thrust direction of the lens and the error in the tilt direction can be reduced. In particular, by combining with conditional expressions (1-1) and (1-2), an optical system with high performance and good assemblability becomes possible.

  According to a fourth zoom lens of the present invention, in the first to third zoom lenses, the first lens group includes a negative meniscus lens convex to the object side and a positive lens, and the second lens group includes: It is composed of a positive lens and a cemented lens of a positive lens and a negative lens in order from the object side.

  The reason and action of the fourth zoom lens according to the present invention having the above configuration will be described below. With such a configuration, the number of lenses in the first lens group and the second lens group is suppressed, and the configuration length of the second lens group is reduced. Can be shortened and made compact when the lens is stored.

  According to a fifth zoom lens of the present invention, in the first to fourth zoom lenses, the positive lens of the first lens group is a double-sided aspheric surface, and the third lens group is composed of one positive lens, The image side surface is an aspherical surface.

  The reason and operation of the fifth zoom lens according to the present invention will be described below.

  By using aspherical surfaces on both surfaces of the positive lens in the first lens group, distortion and field curvature can be corrected well. Further, by using an aspheric surface on the rear side of the third lens group, it is possible to correct field curvature and coma favorably.

  According to a sixth zoom lens of the present invention, in the fourth zoom lens, the negative lens of the cemented lens in the second lens group satisfies the following conditional expression.

D ₂ / f _w <0.2 (2)
Where D ₂ is the thickness of the negative lens of the cemented lens in the second lens group (thickness on the optical axis),
f _w is the focal length of the entire system at the wide-angle end,
It is.

  The reason and action of the sixth zoom lens according to the present invention will be described below.

  By satisfying conditional expression (2), the total thickness of the second lens group is reduced, and the collapsed thickness can be kept small.

  Furthermore, the upper limit value of conditional expression (2) may be set to 0.15.

  Instead of conditional expression (2), the following conditional expression (2-1) may be satisfied.

D ₂ / f _2G <0.15 (2-1)
Where D ₂ is the thickness of the negative lens of the cemented lens in the second lens group (thickness on the optical axis),
f _2G is the focal length of the second lens group,
It is.

  By satisfying conditional expression (2-1), the total thickness of the second lens group is reduced, and the retractable thickness can be kept small.

  Furthermore, the upper limit value of conditional expression (2-1) is preferably 0.1.

  According to a seventh zoom lens of the present invention, in the first to sixth zoom lenses, the negative lens of the first lens group satisfies the following conditional expression.

0.9 <R ₂ / f _w <1.03 (3)
Where R ₂ is the paraxial radius of curvature on the image plane side of the negative lens in the first lens group,
f _w is the focal length of the entire system at the wide-angle end,
It is.

  Hereinafter, the reason and operation of the seventh zoom lens according to the present invention will be described.

  If the lower limit of 0.9 in conditional expression (3) is exceeded, the curvature of the lens included in the first lens group becomes too strong, and the center thickness and edge thickness increase accordingly, resulting in an increase in the size of the entire zoom lens system. . On the other hand, if the upper limit of 1.03 is exceeded, the refractive power of the first lens group becomes too small, and a sufficient field angle cannot be secured in the wide-angle end state.

  Further, instead of the conditional expression (3), the following conditional expression (3-1) may be satisfied.

−0.48 <R ₂ / f _1G <−0.4 (3-1)
Where R ₂ is the paraxial radius of curvature on the image plane side of the negative lens in the first lens group,
f _1G is the focal length of the first lens group,
It is.

  If the lower limit of -0.48 of conditional expression (3-1) is exceeded, the curvature of the lens included in the first lens group becomes too strong, and the center thickness and edge thickness increase accordingly, resulting in a large zoom lens system. It will become. When the upper limit of −0.4 is exceeded, the refractive power of the first lens unit becomes too small, and a sufficient angle of view cannot be secured in the wide-angle end state.

  The eighth zoom lens of the present invention is characterized in that, in the sixth zoom lens, the positive lens of the third lens group is a plastic lens.

  The reason and action of the above configuration in the eighth zoom lens of the present invention will be described below. Conditional expressions (1-1), (1-2), and (2) or (2-1) are satisfied. In the above, even when a glass material having a low refractive index is used for the third lens group, the occurrence of aberrations in the first lens group, the second lens group, and the third lens group can be suppressed, and a plastic lens is used. Thus, a lightweight, inexpensive, high-quality, high-performance zoom lens can be configured.

  According to a ninth zoom lens of the present invention, in the first to eighth zoom lenses, a positive lens closest to the object side in the second lens group is an aspherical lens.

  The reason and operation of the ninth zoom lens according to the present invention will be described below. The object-side positive lens in the second lens group receives an axial light beam that diverges from the first lens group. For this reason, it is advantageous for miniaturization by increasing the refractive power and giving a converging action to the divergent light beam. On the other hand, in this positive lens, spherical aberration tends to occur due to the strong refractive power. Therefore, the occurrence of axial aberration can be reduced by using an aspherical lens as the positive lens on the object side.

  The tenth zoom lens of the present invention is a diaphragm that moves integrally with the second lens group further to the object side than the lens closest to the object side of the second lens group in the first to eighth zoom lenses. It is characterized by having.

  The reason and action of the tenth zoom lens according to the present invention will be described below. In this case, since there is a diaphragm near the second lens group, the second lens group can be downsized. Is advantageous. Moreover, it becomes easy to ensure telecentricity. Moreover, it is also preferable in that the incident height of the off-axis light beam of the first lens does not become too high.

An eleventh zoom lens according to the present invention is a zoom lens that includes a plurality of lens groups including a first lens group that is disposed closest to the object side and has a negative refractive power, and performs zooming by changing the distance between the lens groups. ,
The first lens group includes, in order from the object side, a first lens having a negative refractive power and a second lens having a positive refractive power, and the image surface side surface of the first lens is a plane perpendicular to the optical axis outside the effective diameter. And the object side surface of the second lens has a plane part outside the effective diameter and perpendicular to the optical axis, and the plane part of the first lens and the second lens plane part are in contact with each other. To do.

  The reason and operation of the eleventh zoom lens according to the present invention will be described below.

  Since the two lenses are in contact with each other at a plane portion perpendicular to the optical axis, a frame for fixing the lens is not necessary, so that the manufacturing error of the frame does not affect the relative relationship between the lenses. As a result, the error in the thrust direction of the lens and the error in the tilt direction can be reduced.

In a twelfth zoom lens according to the present invention, in the eleventh zoom lens, one or both of the first lens and the second lens are formed of a molded lens made of glass.
The image lens side surface of the first lens has a plane portion perpendicular to the optical axis formed integrally with the surface outside the effective diameter, and the object side surface of the second lens is molded integrally with the surface outside the effective diameter. The planar portion of the first lens and the planar portion of the second lens are incorporated so as to be in contact with each other.

  Hereinafter, the reason and action of the twelfth zoom lens according to the present invention will be described. The plane portion perpendicular to the optical axis outside the effective diameter is formed integrally with the lens surface so that the plane portion can be accurately formed. .

  According to a thirteenth zoom lens of the present invention, in the eleventh and twelfth zoom lenses, the planar portion is formed such that the object side surface of the second lens is smoothly continuous from the optical axis. It is a feature.

  In the following, the reason and action of the thirteenth zoom lens according to the present invention will be explained. In such a configuration, since the plane portion and the effective portion are continuous in forming the lens, the lens is processed. It becomes easy.

In a fourteenth zoom lens according to the present invention, in the eleventh to thirteenth zoom lenses, the refractive index of the negative first lens in the first lens group is n ₁ , and the refractive power of the positive second lens is n ₂ . In this case, the following conditional expression is satisfied.

n ₁ > 1.8 (1-1)
n ₂ > 1.8 (1-2)
The reason and action of the above-described configuration in the fourteenth zoom lens of the present invention will be described below.

In order to reduce the overall length and reduce the diameter, it is important to use a first lens unit having a refractive index of 1.8 or more, which increases the tilt and thrust effectiveness of both lenses. Therefore, by incorporating the first lens and the second lens as described above so as to be in contact with each other at the lens plane portion, the effect can be suppressed to a small value. Therefore, a glass material with n ₁ > 1.8 and n ₂ > 1.8. Can be used.

  In particular, when the refractive index of the positive lens is increased, the curvature of the object side surface of the positive lens in the first lens group can be easily reduced. Therefore, when this positive lens is formed by a mold, the effective portion and the flat portion are smoothed. Then, creation becomes easy.

  A fifteenth zoom lens according to the present invention includes, in order from the object side to the eleventh to fourteenth zoom lenses, a negative first lens group, a positive second lens group, and a positive third lens group. It is characterized by this.

  The reason and operation of the fifteenth zoom lens according to the present invention will be described below. The three-times zoom lens having a negative and positive refractive power arrangement is thin, and the magnification is three times while maintaining sufficient telecentricity. A zoom lens having a zoom ratio of about a degree can be obtained. In order to make the zoom lens compact while obtaining a zoom ratio of 2 times or more, a positive lens is used in the third lens group to ensure telecentricity, correct the image plane, and zoom.

  According to a sixteenth zoom lens of the present invention, in the fifteenth zoom lens, the second lens group includes two positive lenses and one negative lens, and the third lens group includes one positive lens. In addition, the second lens in the first lens group is a double-sided aspheric surface, and the positive lens in the third lens group is an aspherical lens.

  The reason and action of the above configuration in the sixteenth zoom lens of the present invention will be described below. By using an aspherical surface for the first lens group, distortion and field curvature can be favorably corrected. Further, by using an aspheric surface on the rear side of the third lens group, it is possible to correct field curvature and coma favorably.

  According to a seventeenth zoom lens of the present invention, in the eleventh to sixteenth zoom lenses, the first lens group includes a negative meniscus lens convex to the object side and a positive lens, and the second lens group includes: It is composed of a positive lens and a cemented lens of a positive lens and a negative lens in order from the object side.

  The reason and action of the above configuration in the seventeenth zoom lens of the present invention will be described below. With such a configuration, the number of lenses in the first lens group and the second lens group is suppressed, and the configuration length of the second lens group is reduced. Can be shortened and made compact when the lens is stored.

  In addition, you may comprise so that several structural requirements mentioned above may be satisfied simultaneously.

  According to the present invention as described above, in the zoom lens of the type preceded by the negative lens group, it is possible to provide a zoom lens having an appropriate zoom ratio, sufficiently compact, and having excellent optical characteristics.

  Further, in a zoom lens of a type preceded by a negative lens group, it is possible to provide a zoom lens that is sufficiently compact and has excellent optical characteristics by keeping manufacturing cost low by making it strong against manufacturing errors.

  Examples 1 to 5 of the zoom lens according to the present invention will be described below. FIGS. 1 to 5 show lens cross-sectional views of the wide-angle end (a), the intermediate state (b), and the telephoto end (c) when focusing on an object point at infinity in Examples 1 to 5, respectively. 1 to 5, the first lens group is G1, the aperture stop is S, the second lens group is G2, the third lens group is G3, and a low-pass filter with a wavelength range limiting coat that limits infrared light is configured. The parallel flat plate is indicated by F, the parallel flat plate of the cover glass of the electronic image sensor is indicated by C, and the image plane is indicated by I. In addition, you may give the multilayer film for a wavelength range restriction | limiting to the surface of the cover glass C. FIG. Further, the cover glass C may have a low-pass filter action.

  In Examples 1 to 5 of FIGS. 1 to 5, the plane portion perpendicular to the optical axis outside the effective diameter of the image surface side surface of the negative lens of the first lens group G1 and the effective diameter outside the object side surface of the positive lens are used. The plane portion that is in contact with the plane portion perpendicular to the optical axis and that fixes the lenses is indicated by P.

  As shown in FIG. 1, the zoom lens of Example 1 includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, and a refractive power. The first lens group G1 moves along a concave locus on the object side when zooming from the wide-angle end to the telephoto end, and at the telephoto end, the wide-angle end is at the wide-angle end. Positioned slightly on the object side from the position, the aperture stop S and the second lens group G2 integrally move monotonically toward the object side, and the third lens group G3 moves toward the image plane side.

  In order from the object side, the first lens group G1 includes a negative meniscus lens having a convex surface directed toward the object side, and a biconvex positive lens. The negative meniscus lens and the biconvex positive lens have respective image side surfaces and object side surfaces. The planes perpendicular to the optical axis provided outside the effective diameter (the plane of the object side surface of the biconvex positive lens are formed in a shape that is smoothly continuous with the effective surface) are mutually connected by the flat portions P that are in contact with each other. The second lens group G2 is composed of a biconvex positive lens, a cemented lens of a positive meniscus lens having a convex surface facing the object side and a negative meniscus lens having a convex surface facing the object side. The group G3 includes one positive meniscus lens having a convex surface facing the image surface side.

  The aspherical surfaces are used for the five surfaces of the biconvex positive lens of the first lens group G1, the both surfaces of the biconvex positive lens of the second lens group G2, and the image side surface of the positive meniscus lens of the third lens group G3. ing.

  As shown in FIG. 2, the zoom lens according to the second embodiment includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, and a refractive power. The first lens group G1 moves along a concave locus on the object side when zooming from the wide-angle end to the telephoto end, and at the telephoto end, the wide-angle end is at the wide-angle end. The aperture stop S and the second lens group G2 are monotonously moved toward the object side, and the third lens group G3 is moved along a locus convex toward the image plane side at the telephoto end. Located slightly closer to the object side than the wide-angle end position.

  In order from the object side, the first lens group G1 includes a negative meniscus lens having a convex surface directed toward the object side and a positive meniscus lens having a convex surface directed toward the object side. The negative meniscus lens and the positive meniscus lens are respectively images. A flat surface perpendicular to the optical axis provided outside the effective diameter of the surface side surface and the object side surface (the plane of the object side surface of the positive meniscus lens is formed in a shape that is smoothly continuous with the effective surface). The second lens group G2 includes a biconvex positive lens, and a cemented lens of a positive meniscus lens having a convex surface facing the object side and a negative meniscus lens having a convex surface facing the object side. The third lens group G3 is composed of one biconvex positive lens.

  The aspherical surfaces are used for the five surfaces of the positive meniscus lens of the first lens group G1, the double-sided positive lens of the second lens group G2, and the image side surface of the biconvex positive lens of the third lens group G3. ing.

  As shown in FIG. 3, the zoom lens of Example 3 includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, and a refractive power. The first lens group G1 moves along a concave locus on the object side when zooming from the wide-angle end to the telephoto end, and at the telephoto end, the wide-angle end is at the wide-angle end. The aperture stop S and the second lens group G2 are monotonously moved toward the object side, and the third lens group G3 is moved along a locus convex toward the image plane side at the telephoto end. Located on the image plane side from the wide-angle end position.

  In order from the object side, the first lens group G1 includes a negative meniscus lens having a convex surface directed toward the object side and a positive meniscus lens having a convex surface directed toward the object side. The negative meniscus lens and the positive meniscus lens are respectively images. A flat surface perpendicular to the optical axis provided outside the effective diameter of the surface side surface and the object side surface (the plane of the object side surface of the positive meniscus lens is formed in a shape that is smoothly continuous with the effective surface). The second lens group G2 is composed of a biconvex positive lens and a cemented lens of a biconvex positive lens and a biconcave negative lens, and the third lens group G3 is a biconvex positive lens. It consists of one sheet.

  The aspheric surfaces are 5 on the image plane side surfaces of the positive meniscus lens of the first lens group G1, both surfaces of the biconvex positive lens of the single lens of the second lens group G2, and the biconvex positive lens of the third lens group G3. Used on the surface.

  As shown in FIG. 4, the zoom lens of Example 4 includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, and a refractive power. The first lens group G1 moves along a concave locus on the object side when zooming from the wide-angle end to the telephoto end, and at the telephoto end, the wide-angle end is at the wide-angle end. Positioned slightly on the object side from the position, the aperture stop S and the second lens group G2 integrally move monotonically toward the object side, and the third lens group G3 moves toward the image plane side.

  In order from the object side, the first lens group G1 includes a negative meniscus lens having a convex surface directed toward the object side, and a biconvex positive lens. The negative meniscus lens and the biconvex positive lens have respective image side surfaces and object side surfaces. The planes perpendicular to the optical axis provided outside the effective diameter (the plane of the object side surface of the biconvex positive lens are formed in a shape that is smoothly continuous with the effective surface) are mutually connected by the flat portions P that are in contact with each other. The second lens group G2 is composed of a biconvex positive lens, a cemented lens of a positive meniscus lens having a convex surface facing the object side and a negative meniscus lens having a convex surface facing the object side. The group G3 includes one positive meniscus lens having a convex surface facing the image surface side.

  The aspherical surfaces are used for the five surfaces of the biconvex positive lens of the first lens group G1, the both surfaces of the biconvex positive lens of the second lens group G2, and the image side surface of the positive meniscus lens of the third lens group G3. ing.

  As shown in FIG. 5, the zoom lens of Example 5 includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, and a refractive power. The first lens group G1 moves along a concave locus on the object side when zooming from the wide-angle end to the telephoto end, and at the telephoto end, the wide-angle end is at the wide-angle end. The aperture stop S and the second lens group G2 are integrally moved monotonically to the object side, and the third lens group G3 is moved to the image plane side.

  In order from the object side, the first lens group G1 includes a negative meniscus lens having a convex surface directed toward the object side and a positive meniscus lens having a convex surface directed toward the object side. The negative meniscus lens and the positive meniscus lens are respectively images. A flat surface perpendicular to the optical axis provided outside the effective diameter of the surface side surface and the object side surface (the plane of the object side surface of the positive meniscus lens is formed in a shape that is smoothly continuous with the effective surface). The second lens group G2 includes a biconvex positive lens, and a cemented lens of a positive meniscus lens having a convex surface facing the object side and a negative meniscus lens having a convex surface facing the object side. The third lens group G3 is composed of one biconvex positive lens.

  The aspherical surfaces are used for the five surfaces of the positive meniscus lens of the first lens group G1, the double-sided positive lens of the second lens group G2, and the image side surface of the biconvex positive lens of the third lens group G3. ing.

The numerical data of each of the above embodiments are shown below. Symbols are the above, f is the total focal length, _FNO is the F number, ω is the half angle of view, WE is the wide angle end, ST is the intermediate state, TE telephoto end, r _1, r ₂ ... curvature radius of each lens surface, d _1, d ₂ ... the spacing between the lens surfaces, n _d1, n _d2 ... d-line refractive index of each lens, [nu _d1 , Ν _d2 ... Is the Abbe number of each lens. The aspherical shape is represented by the following formula, where x is an optical axis with the light traveling direction being positive, and y is a direction orthogonal to the optical axis.

x = (y ² / r) / [1+ {1- (K + 1) (y / r) ² } ^1/2 ]
+ A ₄ y ⁴ + A ₆ y ⁶ + A ₈ y ⁸ + A ₁₀ y ¹⁰ + A ₁₂ y ¹²
Where r is the paraxial radius of curvature, K is the conic coefficient, and A ₄ , A ₆ , A ₈ , A ₁₀ , and A ₁₂ are the fourth, sixth, eighth, tenth, and twelfth aspheric coefficients, respectively. .

Example 1
r ₁ = 600.000 d ₁ = 0.90 n _d1 = 1.83481 ν _d1 = 42.71
r ₂ = 6.464 d ₂ = 2.09
r ₃ = 25.787 (aspherical surface) d ₃ = 2.29 n _d2 = 1.82114 ν _d2 = 24.06
r ₄ = -72.532 (aspherical surface) d ₄ = (variable)
r ₅ = ∞ (aperture) d ₅ = 0.52
r ₆ = 9.186 (aspherical surface) d ₆ = 2.10 n _d3 = 1.58913 ν _d3 = 61.25
r ₇ = -16.117 (aspherical surface) d ₇ = 0.10
r ₈ = 4.700 d ₈ = 2.01 n _d4 = 1.60311 ν _d4 = 60.64
r ₉ = 7.781 d ₉ = 0.70 n _d5 = 1.84666 ν _d5 = 23.78
r ₁₀ = 3.277 d ₁₀ = (variable)
r ₁₁ = -76.478 d ₁₁ = 2.30 n _d6 = 1.52542 ν _d6 = 55.78
r ₁₂ = -8.749 (aspherical surface) d ₁₂ = (variable)
r ₁₃ = ∞ d ₁₃ = 0.96 n _d7 = 1.54771 ν _d7 = 62.84
r ₁₄ = ∞ d ₁₄ = 0.60
r ₁₅ = ∞ d ₁₅ = 0.50 n _d8 = 1.51633 ν _d8 = 64.14
r ₁₆ = ∞ d ₁₆ = 0.80
r ₁₇ = ∞ (image plane)
Aspheric coefficient 3rd surface K = 4.269
A ₄ = -1.87599 × 10 ^-4
A ₆ = 7.64679 × 10 ^-7
A ₈ = -1.59780 × 10 ^-7
A ₁₀ = -3.77931 × 10 ^-9
4th surface K = 0.000
A ₄ = -4.24687 × 10 ^-4
A ₆ = 2.52348 × 10 ^-6
A ₈ = -7.16449 × 10 ^-7
A ₁₀ = 2.59036 × 10 ^-8
A ₁₂ = -5.82742 × 10 ^-10
6th page K = 2.867
A ₄ = -8.17109 × 10 ^-4
A ₆ = -2.79925 × 10 ^-5
A ₈ = -1.75116 × 10 ^-6
A ₁₀ = 0
Surface 7 K = 8.841
A ₄ = 3.16055 × 10 ^-4
A ₆ = -2.51075 × 10 ^-5
A ₈ = 1.10436 × 10 ^-7
A ₁₀ = 0
Surface 12 K = 0.000
A ₄ = 5.95690 × 10 ^-4
A ₆ = -1.46363 × 10 ^-5
A ₈ = 2.97205 × 10 ^-7
A ₁₀ = 1.48953 × 10 ^-9
Zoom data (∞)
WE ST TE
f (mm) 6.450 11.020 18.590
F _NO 2.65 3.53 5.00
ω (°) 31.593 18.767 11.388
d ₄ 13.63 6.33 2.10
d ₁₀ 5.48 10.41 18.01
d ₁₂ 1.96 1.57 0.98.

Example 2
r ₁ = 40.804 d ₁ = 0.90 n _d1 = 1.80400 ν _d1 = 46.57
r ₂ = 6.218 d ₂ = 1.95
r ₃ = 15.243 (aspherical surface) d ₃ = 2.00 n _d2 = 1.84666 ν _d2 = 23.78
r ₄ = 43.725 (aspherical surface) d ₄ = (variable)
r ₅ = ∞ (aperture) d ₅ = 0.10
r ₆ = 45.000 (aspherical surface) d ₆ = 2.00 n _d3 = 1.58313 ν _d3 = 59.38
r ₇ = -7.732 (aspherical surface) d ₇ = 0.20
r ₈ = 4.026 d ₈ = 1.80 n _d4 = 1.60311 ν _d4 = 60.64
r ₉ = 6.815 d ₉ = 0.80 n _d5 = 1.84666 ν _d5 = 23.78
r ₁₀ = 3.066 d ₁₀ = (variable)
r ₁₁ = 60.253 d ₁₁ = 2.51 n _d6 = 1.52542 ν _d6 = 55.78
r ₁₂ = -10.285 (aspherical surface) d ₁₂ = (variable)
r ₁₃ = ∞ d ₁₃ = 0.96 n _d7 = 1.54771 ν _d7 = 62.84
r ₁₄ = ∞ d ₁₄ = 0.80
r ₁₅ = ∞ d ₁₅ = 0.50 n _d8 = 1.51633 ν _d8 = 64.14
r ₁₆ = ∞ d ₁₆ = 0.80
r ₁₇ = ∞ (image plane)
Aspheric coefficient 3rd surface K = -0.838
A ₄ = -6.54143 × 10 ^-5
A ₆ = -3.82957 × 10 ^-5
A ₈ = 2.14452 × 10 ^-6
A ₁₀ = -4.23358 × 10 ^-8
4th surface K = 0.000
A ₄ = -3.73404 × 10 ^-4
A ₆ = -4.02332 × 10 ^-5
A ₈ = 2.38711 × 10 ^-6
A ₁₀ = -5.34810 × 10 ^-8
6th surface K = -4.773
A ₄ = -1.63350 × 10 ^-3
A ₆ = -6.65602 × 10 ^-5
A ₈ = -2.50994 × 10 ^-6
A ₁₀ = 0
Surface 7 K = 2.932
A ₄ = -5.94103 × 10 ^-5
A ₆ = -2.65976 × 10 ^-5
A ₈ = 2.33540 × 10 ^-6
A ₁₀ = 0
Surface 12 K = -0.704
A ₄ = 1.73265 × 10 ^-4
A ₆ = 1.85462 × 10 ^-6
A ₈ = -1.45809 × 10 ^-7
A ₁₀ = 0
Zoom data (∞)
WE ST TE
f (mm) 6.460 11.000 18.590
F _NO 3.00 3.91 5.33
ω (°) 30.396 18.131 10.907
d ₄ 14.25 6.40 1.40
d ₁₀ 5.76 10.11 16.81
d ₁₂ 1.18 1.00 1.56.

Example 3
r ₁ = 300.050 d ₁ = 0.90 n _d1 = 1.80400 ν _d1 = 46.57
r ₂ = 6.450 d ₂ = 1.80
r ₃ = 15.428 (aspherical surface) d ₃ = 2.00 n _d2 = 1.82114 ν _d2 = 24.06
r ₄ = 90.475 (aspherical surface) d ₄ = (variable)
r ₅ = ∞ (aperture) d ₅ = 0.00
r ₆ = 31.500 (aspherical surface) d ₆ = 1.80 n _d3 = 1.48749 ν _d3 = 70.44
r ₇ = -8.912 (aspherical surface) d ₇ = 0.20
r ₈ = 5.451 d ₈ = 2.51 n _d4 = 1.67790 ν _d4 = 55.34
r ₉ = -8.486 d ₉ = 0.80 n _d5 = 1.59270 ν _d5 = 35.31
r ₁₀ = 3.360 d ₁₀ = (variable)
r ₁₁ = 221.891 d ₁₁ = 2.30 n _d6 = 1.52542 ν _d6 = 55.78
r ₁₂ = -10.272 (aspherical surface) d ₁₂ = (variable)
r ₁₃ = ∞ d ₁₃ = 0.96 n _d7 = 1.54771 ν _d7 = 62.84
r ₁₄ = ∞ d ₁₄ = 0.80
r ₁₅ = ∞ d ₁₅ = 0.50 n _d8 = 1.51633 ν _d8 = 64.14
r ₁₆ = ∞ d ₁₆ = 0.76
r ₁₇ = ∞ (image plane)
Aspheric coefficient 3rd surface K = -0.140
A ₄ = -1.53377 × 10 ^-4
A ₆ = -4.69559 × 10 ^-6
A ₈ = -3.81572 × 10 ^-7
A ₁₀ = 1.21558 × 10 ^-8
4th surface K = 0.000
A ₄ = -3.83875 × 10 ^-4
A ₆ = -1.32313 × 10 ^-5
A ₈ = 1.05382 × 10 ^-7
A ₁₀ = -1.33184 × 10 ^-9
6th surface K = -222.219
A ₄ = -4.46470 × 10 ^-4
A ₆ = -1.56452 × 10 ^-4
A ₈ = 4.01062 × 10 ^-6
A ₁₀ = 0
Surface 7 K = 2.239
A ₄ = -2.75746 × 10 ^-4
A ₆ = -6.35509 × 10 ^-5
A ₈ = 2.00725 × 10 ^-6
A ₁₀ = 0
Surface 12 K = -1.266
A ₄ = 1.46615 × 10 ^-4
A ₆ = -1.81005 × 10 ^-6
A ₈ = -4.95228 × 10 ^-8
A ₁₀ = 0
Zoom data (∞)
WE ST TE
f (mm) 6.447 10.973 18.553
F _NO 2.99 3.96 5.44
ω (°) 31.014 18.295 10.961
d ₄ 13.53 6.29 1.50
d ₁₀ 5.50 10.43 17.27
d ₁₂ 1.67 1.00 1.17.

Example 4
r ₁ = 268.142 d ₁ = 0.90 n _d1 = 1.83481 ν _d1 = 42.71
r ₂ = 6.466 d ₂ = 2.05
r ₃ = 23.852 (aspherical surface) d ₃ = 2.25 n _d2 = 1.84666 ν _d2 = 23.78
r ₄ = -115.636 (aspherical surface) d ₄ = (variable)
r ₅ = ∞ (aperture) d ₅ = 0.52
r ₆ = 9.836 (aspherical surface) d ₆ = 2.10 n _d3 = 1.58913 ν _d3 = 61.14
r ₇ = -14.876 (aspherical surface) d ₇ = 0.10
r ₈ = 4.700 d ₈ = 2.01 n _d4 = 1.60311 ν _d4 = 60.64
r ₉ = 7.840 d ₉ = 0.70 n _d5 = 1.84666 ν _d5 = 23.78
r ₁₀ = 3.321 d ₁₀ = (variable)
r ₁₁ = -234.912 d ₁₁ = 2.23 n _d6 = 1.52542 ν _d6 = 55.78
r ₁₂ = -9.384 (aspherical surface) d ₁₂ = (variable)
r ₁₃ = ∞ d ₁₃ = 0.96 n _d7 = 1.54771 ν _d7 = 62.84
r ₁₄ = ∞ d ₁₄ = 0.60
r ₁₅ = ∞ d ₁₅ = 0.50 n _d8 = 1.51633 ν _d8 = 64.14
r ₁₆ = ∞ d ₁₆ = 0.80
r ₁₇ = ∞ (image plane)
Aspheric coefficient 3rd surface K = 4.986
A ₄ = -1.57553 × 10 ^-4
A ₆ = -2.56359 × 10 ^-6
A ₈ = -2.06881 × 10 ^-7
A ₁₀ = -1.96672 × 10 ^-9
4th surface K = 0.000
A ₄ = -3.80671 × 10 ^-4
A ₆ = -3.35620 × 10 ^-7
A ₈ = -7.60214 × 10 ^-7
A ₁₀ = 2.91748 × 10 ^-8
A ₁₂ = -6.16124 × 10 ^-10
6th surface K = 2.683
A ₄ = -7.48363 × 10 ^-4
A ₆ = -3.47002 × 10 ^-5
A ₈ = -1.28246 × 10 ^-6
A ₁₀ = 0
Surface 7 K = 5.711
A ₄ = 1.87600 × 10 ^-4
A ₆ = -3.25799 × 10 ^-5
A ₈ = -5.16557 × 10 ^-8
A ₁₀ = 0
Surface 12 K = 0.000
A ₄ = 6.90315 × 10 ^-4
A ₆ = -3.12977 × 10 ^-5
A ₈ = 1.51283 × 10 ^-6
A ₁₀ = -3.12539 × 10 ^-8
Zoom data (∞)
WE ST TE
f (mm) 6.450 11.000 18.590
F _NO 2.66 3.53 5.00
ω (°) 30.383 17.966 10.838
d ₄ 13.70 6.34 2.10
d ₁₀ 5.60 10.43 18.08
d ₁₂ 1.90 1.60 1.04.

Example 5
r ₁ = 52.387 d ₁ = 0.80 n _d1 = 1.83481 ν _d1 = 42.71
r ₂ = 6.600 d ₂ = 1.90
r ₃ = 18.650 (aspherical surface) d ₃ = 2.25 n _d2 = 2.00170 ν _d2 = 20.65
r ₄ = 49.640 (aspherical surface) d ₄ = (variable)
r ₅ = ∞ (aperture) d ₅ = 0.52
r ₆ = 12.288 (aspherical surface) d ₆ = 2.10 n _d3 = 1.58913 ν _d3 = 61.24
r ₇ = -12.431 (aspherical surface) d ₇ = 0.10
r ₈ = 4.700 d ₈ = 2.00 n _d4 = 1.60311 ν _d4 = 60.64
r ₉ = 7.433 d ₉ = 0.70 n _d5 = 1.84666 ν _d5 = 23.78
r ₁₀ = 3.471 d ₁₀ = (variable)
r ₁₁ = 590.423 d ₁₁ = 2.20 n _d6 = 1.52542 ν _d6 = 55.78
r ₁₂ = -9.819 (aspherical surface) d ₁₂ = (variable)
r ₁₃ = ∞ d ₁₃ = 0.96 n _d7 = 1.54771 ν _d7 = 62.84
r ₁₄ = ∞ d ₁₄ = 0.60
r ₁₅ = ∞ d ₁₅ = 0.50 n _d8 = 1.51633 ν _d8 = 64.14
r ₁₆ = ∞ d ₁₆ = 0.79
r ₁₇ = ∞ (image plane)
Aspheric coefficient 3rd surface K = -17.705
A ₄ = -7.27267 × 10 ^-5
A ₆ = -8.24112 × 10 ^-6
A ₈ = 7.94390 × 10 ^-8
A ₁₀ = 8.88090 × 10 ^-10
4th surface K = 0.000
A ₄ = -6.44514 × 10 ^-4
A ₆ = 1.98569 × 10 ^-6
A ₈ = -2.56686 × 10 ^-7
A ₁₀ = 1.44795 × 10 ^-8
A ₁₂ = -3.41244 × 10 ^-10
6th page K = 2.651
A ₄ = -4.50048 × 10 ^-4
A ₆ = -8.11323 × 10 ^-5
A ₈ = 2.50010 × 10 ^-6
A ₁₀ = 0
Surface 7 K = 9.035
A ₄ = 7.46290 × 10 ^-4
A ₆ = -7.81287 × 10 ^-5
A ₈ = 5.71733 × 10 ^-6
A ₁₀ = 0
Surface 12 K = 0.000
A ₄ = 3.35417 × 10 ^-4
A ₆ = -7.88925 × 10 ^-6
A ₈ = 2.00340 × 10 ^-7
A ₁₀ = -8.39908 × 10 ^-10
Zoom data (∞)
WE ST TE
f (mm) 6.450 11.000 18.590
F _NO 2.69 3.55 5.00
ω (°) 31.677 18.372 11.052
d ₄ 14.08 6.77 2.59
d ₁₀ 5.56 10.33 17.91
d ₁₂ 1.94 1.65 1.08.

  Aberration diagrams at the time of focusing on an object point at infinity in Examples 1 to 5 are shown in FIGS. In these aberration diagrams, (a) is the wide angle end, (b) is the intermediate state, (c) is the spherical aberration (SA), astigmatism (AS), distortion (DT), and lateral chromatic aberration (CC) at the telephoto end. ). In each figure, “FIY” indicates the maximum image height.

Next, the angle of view, the values of conditional expressions (1-1) to (3-1), and the values of f _1G and f _2G in each of the above embodiments will be shown.

Conditional Example Example 1 Example 2 Example 3 Example 4 Example 5
(1-1) 1.83481 1.80400 1.80400 1.83481 1.83481
(1-2) 1.82114 1.84666 1.82114 1.84666 2.00170
(A) 0.76 1.72 1.15 0.76 1.32
(2) 0.11 0.12 0.12 0.11 0.11
(2-1) 0.064 0.074 0.074 0.064 0.065
(3) 1.00 0.96 1.00 1.00 1.02
(3-1) -0.46 -0.41 -0.44 -0.46 -0.46
f _1G -13.93 -15.21 -14.58 -14.03 -14.20
f _2G 10.89 10.76 10.75 10.9 10.78
.

  FIGS. 11 to 13 are conceptual diagrams of the configuration of a digital camera according to the present invention in which the zoom lens as described above is incorporated in the photographing optical system 41. FIG. 11 is a front perspective view showing the appearance of the digital camera 40, FIG. 12 is a rear front view thereof, and FIG. 13 is a schematic cross-sectional view showing the configuration of the digital camera 40. However, in FIGS. 11 and 13, the photographing optical system 41 is not retracted. In this example, the digital camera 40 includes a photographing optical system 41 having a photographing optical path 42, a finder optical system 43 having a finder optical path 44, a shutter button 45, a flash 46, a liquid crystal display monitor 47, a focal length change button 61, When the photographing optical system 41 is retracted, including the setting change switch 62, the photographing optical system 41, the finder optical system 43, and the flash 46 are covered with the cover 60 by sliding the cover 60. When the cover 60 is opened and the camera 40 is set to the photographing state, the photographing optical system 41 is brought into the non-collapsed state of FIG. 13, and when the shutter button 45 disposed on the upper part of the camera 40 is pressed, the photographing is performed in conjunction therewith. Photographing is performed through the optical system 41, for example, the zoom lens of the first embodiment. An object image formed by the photographic optical system 41 is formed on the imaging surface of the CCD 49 through a low-pass filter F and a cover glass C that are provided with a wavelength band limiting coat. The object image received by the CCD 49 is displayed as an electronic image on the liquid crystal display monitor 47 provided on the back of the camera via the processing means 51. Further, the processing means 51 is connected to a recording means 52 so that a photographed electronic image can be recorded. The recording means 52 may be provided separately from the processing means 51, or may be configured to perform recording / writing electronically using a floppy disk, memory card, MO, or the like. Further, it may be configured as a silver salt camera in which a silver salt film is arranged in place of the CCD 49.

  Further, a finder objective optical system 53 is disposed on the finder optical path 44. The finder objective optical system 53 includes a plurality of lens groups (three groups in the figure) and two prisms, and includes a zoom optical system whose focal length changes in conjunction with the zoom lens of the photographing optical system 41. The object image formed by the finder objective optical system 53 is formed on the field frame 57 of the erecting prism 55 that is an image erecting member. Behind the erecting prism 55, an eyepiece optical system 59 for guiding the erect image to the observer eyeball E is disposed. A cover member 50 is disposed on the exit side of the eyepiece optical system 59.

  The digital camera 40 configured in this manner has a high performance because the photographing optical system 41 is extremely thin when retracted, and the imaging performance is extremely stable at high zooming and in all zooming ranges.・ Compact and wide angle can be realized.

FIG. 2 is a lens cross-sectional view at the wide-angle end (a), the intermediate state (b), and the telephoto end (c) when focusing on an object point at infinity according to the first exemplary embodiment of the zoom lens of the present invention. It is the same figure as FIG. 1 of Example 2 of the zoom lens of this invention. It is the same figure as FIG. 1 of Example 3 of the zoom lens of this invention. It is the same figure as FIG. 1 of Example 4 of the zoom lens of this invention. It is the same figure as FIG. 1 of Example 5 of the zoom lens of this invention. FIG. 6 is an aberration diagram for Example 1 upon focusing on an object point at infinity. FIG. 6 is an aberration diagram for Example 2 upon focusing on an object point at infinity. FIG. 10 is an aberration diagram for Example 3 upon focusing on an object point at infinity. FIG. 10 is an aberration diagram for Example 4 upon focusing on an object point at infinity. FIG. 10 is an aberration diagram for Example 5 upon focusing on an object point at infinity. It is a front perspective view which shows the external appearance of the digital camera by this invention. FIG. 12 is a rear perspective view of the digital camera of FIG. 11. It is sectional drawing of the digital camera of FIG.

Explanation of symbols

G1 ... 1st lens group G2 ... 2nd lens group G3 ... 3rd lens group S ... Aperture stop F ... Low pass filter C ... Cover glass I ... Image plane P ... Plane part E ... Observer eyeball 40 ... Digital camera 41 ... Photography Optical system 42 ... Shooting optical path 43 ... Viewfinder optical system 44 ... Viewfinder optical path 45 ... Shutter button 46 ... Flash 47 ... Liquid crystal display monitor 49 ... CCD
DESCRIPTION OF SYMBOLS 50 ... Cover member 51 ... Processing means 52 ... Recording means 53 ... Viewfinder objective optical system 55 ... Erect prism 57 ... Field frame 59 ... Eyepiece optical system 60 ... Cover 61 ... Focal length change button 62 ... Setting change switch

Claims (18)

In order from the object side, 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, and changing the distance between the lens groups, In the zoom lens to perform
The first lens group includes two negative lenses and a positive lens, the second lens group includes two positive lenses and one negative lens, and the third lens group includes one positive lens. And a zoom lens characterized by satisfying the following conditional expression:
n ₁ > 1.8 (1-1)
n ₂ > 1.8 (1-2)
Here, n ₁ is the refractive index of the negative lens of the first lens group, and n ₂ is the refractive index of the positive lens of the first lens group. The first lens group includes, in order from the object side, a negative lens having a concave surface facing the image surface side and a positive lens having a convex surface facing the object side, and satisfies the following conditions: The zoom lens according to 1.
0.3 <| f _1G / R ₁ + f _1G / R ₃ + f _1G / R ₄ | <1.9 (A)
Where f _1G is the focal length of the first lens group,
R ₁ is the absolute value of the paraxial radius of curvature of the object side surface of the first lens unit negative lens;
R ₃ is the absolute value of the paraxial radius of curvature of the object side surface of the first lens unit positive lens;
R ₄ is the absolute value of the paraxial radius of curvature of the image side surface of the first lens unit positive lens;
It is. The two lenses in the first lens group have a positioning portion for positioning the lenses relative to each other, the lenses are in contact with each other at the positioning portion, and a space is sandwiched within the effective diameter. The zoom lens according to claim 1 or 2, characterized in that: The first lens group includes a negative meniscus lens convex to the object side and a positive lens, and the second lens group includes a positive lens and a cemented lens of a positive lens and a negative lens in order from the object side. The zoom lens according to claim 1, wherein the zoom lens is a zoom lens. 5. The positive lens of the first lens group is a double-sided aspheric surface, the third lens group is composed of a single positive lens, and the image side surface thereof is an aspherical surface. The zoom lens according to any one of the above. The zoom lens according to claim 4, wherein the negative lens of the cemented lens in the second lens group satisfies the following conditional expression.
D ₂ / f _w <0.2 (2)
D ₂ is the thickness of the negative lens of the cemented lens in the second lens group,
f _w is the focal length of the entire system at the wide-angle end,
It is. The zoom lens according to claim 1, wherein the negative lens of the first lens group satisfies the following conditional expression.
0.9 <R ₂ / f _w <1.03 (3)
Where R ₂ is the paraxial radius of curvature on the image plane side of the negative lens in the first lens group,
f _w is the focal length of the entire system at the wide-angle end,
It is. The zoom lens according to claim 6, wherein the positive lens of the third lens group is a plastic lens. The zoom lens according to any one of claims 1 to 8, wherein a positive lens closest to the object side in the second lens group is an aspherical lens. The zoom according to any one of claims 1 to 9, further comprising a stop that moves integrally with the second lens group, further on the object side than the lens closest to the object side of the second lens group. lens. In a zoom lens that includes a plurality of lens groups including a first lens group that is disposed closest to the object side and has a negative refractive power, and performs zooming by changing the interval between the lens groups,
The first lens group includes, in order from the object side, a first lens having a negative refractive power and a second lens having a positive refractive power, and the image surface side surface of the first lens is a plane perpendicular to the optical axis outside the effective diameter. And the object side surface of the second lens has a plane part outside the effective diameter and perpendicular to the optical axis, and the plane part of the first lens and the second lens plane part are in contact with each other. Zoom lens to be used. One or both of the first lens and the second lens are formed of a glass molded lens,
The image lens side surface of the first lens has a plane portion perpendicular to the optical axis formed integrally with the surface outside the effective diameter, and the object side surface of the second lens is molded integrally with the surface outside the effective diameter. 12. The zoom lens according to claim 11, further comprising a plane portion perpendicular to the optical axis, wherein the plane portion of the first lens and the second lens plane portion are assembled so as to contact each other. 13. The zoom lens according to claim 11, wherein the planar portion is formed such that the object-side surface of the second lens is smoothly continuous from the optical axis. The following conditional expressions are satisfied, where n _{1 is} the refractive index of the negative first lens of the first lens group and n ₂ is the refractive power of the positive second lens: 14. The zoom lens according to any one of items 13.
n ₁ > 1.8 (1-1)
n ₂ > 1.8 (1-2) The zoom lens according to claim 11, wherein the zoom lens includes a negative first lens group, a positive second lens group, and a positive third lens group in order from the object side. The second lens group is composed of two positive lenses and one negative lens, the third lens group is composed of one positive lens, and the second lens in the first lens group is double-sided. 16. The zoom lens according to claim 15, wherein the zoom lens is an aspheric surface, and the positive lens in the third lens group is an aspheric lens. The first lens group includes a negative meniscus lens convex to the object side and a positive lens, and the second lens group includes a positive lens and a cemented lens of a positive lens and a negative lens in order from the object side. The zoom lens according to claim 11, wherein the zoom lens is a zoom lens. 18. An image pickup apparatus comprising: the zoom lens according to claim 1; and an image pickup element that is disposed on an image side of the zoom lens and converts an image formed by the zoom lens into an electric signal. .

Images