JP2006178244A - Zoom lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a zoom lens which has wide angle of view and with which a high zoom ratio is assured. <P>SOLUTION: The zoom lens is equipped with a first lens group I having positive refractive power, a second lens group II having negative refractive power, a third lens group III having positive refractive power, a fourth lens group IV having negative refractive power, and a fifth lens group V having positive refractive power, in the order from the object side to the image face side, in which the first lens group I is fixed, and zooming from a wide angle end to a telephoto end is performed by moving the second lens group II from the object side to the image plane side, and the aberration correction accompanying the zooming is performed by moving the third lens group III, the fourth lens group IV and the fifth lens group V. As a result, the zoom lens of the high optical performance with which the wide angle of view as wide as about 75° can be obtained at a wide angle end, a variable power ratio (zoom ratio) of about 5 times can be assured and the various aberrations are well corrected over the entire area of a zoom range can be obtained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an inner focus type zoom lens that is applied to a high-quality digital still camera or digital video camera equipped with a solid-state imaging device such as a CCD, and in particular, a zoom lens having a wide angle of view and a high zoom ratio. About.

  As a conventional zoom lens mounted on a digital still camera or the like, a first lens group and a second lens array arranged in order from the object side so that a lens group having a positive refractive power suitable for a high zoom ratio precedes. A lens group, a third lens group, and a fourth lens group, and at least one aspheric surface is provided in the third lens group or the fourth lens group, and the second lens group is moved to perform zooming; A so-called positive lead type zoom lens is known that corrects fluctuations and focusing during zooming by moving the zoom lens (see, for example, Patent Document 1).

  Further, as another conventional zoom lens, a first lens group, a second lens group, and so on, which are arranged in order from the object side so that a lens group having a negative refractive power suitable for a wide angle of view precedes, The third lens group includes a third lens group, and a plurality of aspheric surfaces are provided in the second lens group, and the second lens group is moved from the image plane side to the object side and the distance from the second lens group is changed. A so-called negative lead type zoom lens is known that performs zooming from the wide-angle end to the telephoto end by moving the zoom lens (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 62-178717 JP 2003-121741 A

  However, due to the nature of the zoom lens, in the positive lead type zoom lens disclosed in Patent Document 1, the angle of view at the wide-angle end is about 50 °, and it is difficult to increase the angle of view beyond that. Further, due to the nature of the zoom lens, in the negative lead type zoom lens disclosed in Patent Document 2, the zoom ratio (magnification ratio) that can be secured is about 3 to 4 times, and it is difficult to increase the zoom ratio beyond that. It is.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a zoom lens with high optical performance that achieves both a wide angle of view and a high zoom ratio. Specifically, the zoom lens is an inner focus type zoom lens that has a wide angle of view of about 75 ° at the wide angle end and a large zoom ratio of about 5 times and has excellent optical performance with various aberrations corrected well. Is to provide.

The zoom lens of the present invention includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power in order from the object side to the image plane side. A fourth lens group having a negative refractive power and a fifth lens group having a positive refractive power, the first lens group is fixed, and the second lens group is moved from the object side to the image plane side. Zooming from the wide-angle end to the telephoto end is performed, and aberrations associated with zooming are corrected by moving the third lens group, the fourth lens group, and the fifth lens group.
According to this configuration, with the first lens group stationary, the second lens group moves from the object side to the image plane side to perform zooming from the wide-angle end to the telephoto end, and the third lens group and the fourth lens. The group and the fifth lens group are moved as appropriate to correct aberrations associated with zooming.
In this way, the first lens group is fixed as an inner focus type zoom lens, and five lens groups having positive, negative, positive, negative, and positive refractive powers are arranged from the object side to the image plane side. As a result, a wide field angle of about 75 ° at the wide-angle end can be obtained, and a zoom ratio of about 5 times can be secured, and various aberrations are well corrected over the entire zoom range. High zoom lens can be obtained.

In the above configuration, the first lens group is composed of a single first lens having a positive refractive power, and the focal length of the lens system from the first lens group to the image plane at the wide-angle end is fw. When the focal length is fG1 and the Abbe number of the first lens is ν1, the following conditional expressions (1) and (2)
(1) 0.05 <fw / fG1 <0.12
(2) ν1> 60
A configuration that satisfies the above can be adopted.
According to this configuration, by configuring the first lens group having a large lens diameter with a single first lens, it is possible to achieve a reduction in size and cost, and the first lens group (first lens) can be achieved. By fixing, the lens can be prevented from being eccentric and firmly held, and the strength against external impact or the like can be increased. Further, by satisfying conditional expressions (1) and (2), various aberrations, particularly chromatic aberration, can be favorably corrected while shortening the overall length of the lens system.

In the above configuration, the second lens group includes a second lens having a negative refractive power closest to the object side, and the second lens has an aspherical surface on at least one of the object side surface and the image side surface. Can be adopted.
According to this configuration, by providing an aspherical surface on the second lens located closest to the object side in the second lens group, it is possible to satisfactorily correct various aberrations, particularly negative distortion, and zoom with high optical performance. A lens can be obtained.

In the above configuration, the third lens group may have a configuration having at least one aspheric surface.
According to this configuration, it is possible to satisfactorily correct various aberrations, particularly spherical aberration and coma aberration, and it is possible to obtain a zoom lens with high optical performance.

In the above configuration, it is possible to adopt a configuration in which focusing is performed by moving the fourth lens group.
According to this configuration, the focusing power can be reduced by moving the fourth lens group having a relatively small lens diameter and a light weight, thereby reducing the power consumption consumed by the driving motor. be able to.

  As described above, according to the zoom lens of the present invention, it is possible to obtain a zoom lens having a high zoom ratio and a wide angle of view and high optical performance in which various aberrations are well corrected over the entire zoom range. That is, a wide angle of view of about 75 ° is obtained at the wide-angle end, and a zoom ratio (magnification ratio) of about 5 times can be secured, various aberrations are corrected well, optical performance is high, and high-quality digital still A zoom lens suitable for cameras, digital video cameras and the like can be obtained.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, exemplary embodiments of the invention will be described with reference to the accompanying drawings.
1 and 2 show an embodiment of a zoom lens according to the present invention. FIG. 1 is a basic configuration diagram, and FIG. 2 is a state diagram at a wide-angle end, an intermediate position, and a telephoto end.

In this zoom lens, as shown in FIG. 1, a first lens group (I) having a positive refractive power as a whole, a second lens group (II) having a negative refractive power as a whole, and a positive refraction as a whole. A third lens group (III) having a power, a fourth lens group (IV) having a negative refractive power as a whole, and a fifth lens group (V) having a positive refractive power as a whole from the object side to the image plane side It is arranged sequentially toward
Then, as shown in FIGS. 2A, 2B, and 2C, the second lens group (II) is viewed from the object side with the first lens group (I) fixed at a predetermined position. And zooming from the wide-angle end to the telephoto end, and the third lens group (III) to the fifth lens group (IV) move from the image plane side to the object side, and aberrations caused by zooming Correction is made. Further, the fourth lens group (IV) moves to perform focusing (focusing operation).
In this way, the first lens group (I) is fixed as an inner focus type zoom lens, and five lenses having positive, negative, positive, negative, and positive refractive powers from the object side to the image plane side. By arranging the groups (I), (II), (III), (IV), and (V), a wide angle of view of about 75 ° can be obtained at the wide angle end, and a zoom ratio of about 5 times (zoom) Ratio) can be secured, and a zoom lens with high optical performance in which various aberrations are well corrected over the entire zoom range can be obtained.

As shown in FIG. 1, the first lens group (I) includes a single first lens 1 having a positive refractive power. In this way, by configuring the first lens group having a large lens diameter with the single first lens 1, it is possible to achieve a reduction in size and cost, and the first lens group (the first lens 1) can be achieved. By being fixed, the lens can be prevented from being eccentric and firmly held, and the strength against external impacts can be increased.
As shown in FIG. 1, the second lens group (II) includes a second lens 2 having a negative refractive power, a third lens 3 having a negative refractive power, arranged in order from the object side to the image plane side, The fourth lens 4 has a negative refractive power and the fifth lens 5 has a positive refractive power.
As shown in FIG. 1, the third lens group (III) includes a sixth lens 6 having a positive refractive power, an aperture stop SD that defines a predetermined aperture, a negative aperture, which are arranged in order from the object side to the image plane side. And a seventh lens 7 having a refractive power of 8, an eighth lens 8 having a positive refractive power and being joined to the seventh lens 7, and a ninth lens 9 having a positive refractive power.

As shown in FIG. 1, the fourth lens group (IV) is joined to the tenth lens 10 and the tenth lens 10 having positive refractive power, which are arranged in order from the object side to the image plane side, and is negative. The eleventh lens 11 has a refractive power.
The tenth lens 10 and the eleventh lens 11 constituting the fourth lens group (IV) are formed with a relatively small lens diameter as compared with the lenses constituting the other lens groups, and the entire lens group is also configured. It is lighter than other lens groups. Therefore, when focusing is performed by moving the fourth lens group (IV), the driving force for focusing can be reduced, and therefore the power consumption consumed by the drive motor can be reduced.
As shown in FIG. 1, the fifth lens group (V) is joined to the twelfth lens 12 and the twelfth lens 12 having positive refractive power arranged in order from the object side to the image surface side, and is negative. It is constituted by a thirteenth lens 13 having a refractive power.

  In the above configuration, a glass filter 14 that functions as an infrared cut filter, a low-pass filter, or the like is disposed closer to the image plane side than the fifth lens group (V), that is, the thirteenth lens 13. An image forming plane P of a CCD as a solid-state image sensor is disposed in FIG.

Here, the length of the lens system (from the object-side surface (front surface) to the imaging plane P of the first lens 1) is the total length of the lens system, the focal length of the lens system is f, and the focal length of the lens system at the wide angle end. Is denoted by fw, the focal length of the lens system at the intermediate position is denoted by fm, the focal length of the lens system at the telephoto end is denoted by ft, and the focal lengths of the first lens group (I) to the fifth lens group (V) are denoted by fG1 to fG5.
Further, in the first lens 13 to the thirteenth lens 13 and the glass filter 14, as shown in FIG. 1, each surface is Si (i = 1 to 26), and the curvature radius of each surface Si is Ri (i = 1-26), the refractive index for the d-line is represented by Ni and the Abbe number is represented by νi (i = 1-14).
Further, the distance (thickness, air interval) on each optical axis L from the first lens 1 to the glass filter 14 to the image plane P is represented by Di (i = 1 to 25), and the image of the thirteenth lens 13 is displayed. The distance from the surface side (rear surface) S24 to the imaging plane P is defined as back focus (air conversion distance), and the distance from the rear surface S26 of the glass filter 14 to the image plane P is represented by BF.

The first lens 1 is a meniscus lens made of a glass material and having a convex surface S1 on the object side and a concave surface S2 on the image surface side.
The second lens 2 is a meniscus lens made of a glass material and having a convex surface S3 on the object side and a concave surface S3 on the image surface side.
The third lens 3 is a biconcave lens formed of a glass material and having a concave surface S5 on the object side and a concave surface S6 on the image surface side.
The fourth lens 4 is a biconcave lens made of a glass material and having a concave surface S7 on the object side and a concave surface S8 on the image surface side.
The fifth lens 5 is a biconvex lens formed of a glass material and having a convex surface S9 on the object side and a convex surface S10 on the image surface side.

The sixth lens 6 is a biconvex lens formed of a glass material and having a convex surface S11 on the object side and a convex surface S12 on the image surface side.
The seventh lens 7 is a biconcave lens made of a glass material and having a concave surface S14 on the object side and a concave surface S15 on the image side.
The eighth lens 8 is a biconvex lens formed of a glass material and bonded to the seventh lens 7 and having a convex surface S15 on the object side and a convex surface S16 on the image surface side.
The ninth lens 9 is a biconvex lens formed of a glass material and having a convex surface S17 on the object side and a convex surface S18 on the image surface side.

The tenth lens 10 is a biconvex lens formed of a glass material and having a convex surface S19 on the object side and a convex surface S20 on the image surface side.
The eleventh lens 11 is formed of a glass material and is joined to the tenth lens 10, and is a biconcave lens having a concave surface S20 on the object side and a concave surface S21 on the image side.
The twelfth lens 12 is a biconvex lens formed of a glass material and having a convex surface S22 on the object side and a convex surface S23 on the image surface side.
The thirteenth lens 13 is a meniscus lens formed of a glass material and bonded to the twelfth lens 12, with the concave surface S23 facing the object side and the convex surface S24 facing the image surface side.

In the above configuration, preferably, at least one of the object-side surface S3 and the image-side surface S4 of the second lens 2 constituting the second lens group (II) is formed as an aspheric surface. At least one of the object side surface and the image surface side surface of the sixth lens 6 to the ninth lens 9 constituting the lens group (III) is formed as an aspherical surface.
Thus, by providing an aspherical surface on the second lens 2 located closest to the object side in the second lens group (II), various aberrations, in particular, negative distortion aberration can be favorably corrected, and optical performance can be improved. A high zoom lens can be obtained. Further, by providing an aspheric surface on at least one surface of the lens constituting the third lens group (III), various aberrations, in particular, spherical aberration and coma aberration can be corrected satisfactorily. A high zoom lens can be obtained.

Here, the expression representing the aspheric surface is defined by the following expression.
Z = Cy ² / [1+ (1-εC ² y ² ) ^1/2 ] + Dy ⁴ + Ey ⁶ + Fy ⁸ + Gy ¹⁰ + Hy ¹²
Where Z: distance from the tangent plane at the apex of the aspheric surface to a point on the aspheric surface whose height from the optical axis L is y, y: height from the optical axis, C: curvature at the apex of the aspheric surface ( 1 / R), ε: conic constant, D, E, F, G, H: aspheric coefficients.

Further, in the above configuration, the focal length fw of the lens system from the first lens group (I) to the image plane P at the wide angle end, the focal length fG1 of the first lens group (I), and the Abbe number ν1 of the first lens 1. Preferably, the following conditional expressions (1) and (2)
(1) 0.05 <fw / fG1 <0.12
(2) ν1> 60
It is formed so as to satisfy.
Conditional expression (1) defines the relationship of the focal length of the lens system at the wide-angle end with respect to the focal length of the first lens group (I), and when the value of fw / fG1 exceeds the lower limit, On the other hand, if the value of fw / fG1 exceeds the upper limit value, the correction of chromatic aberration becomes difficult. Therefore, by satisfying conditional expression (1), it is possible to shorten the overall length of the lens system and achieve miniaturization, and it is possible to satisfactorily correct various aberrations, particularly chromatic aberration, over the entire zooming range.
Conditional expression (2) defines the Abbe number of the first lens 1, and by satisfying this conditional expression (2), various aberrations, particularly chromatic aberration, can be corrected satisfactorily over the entire zoom range. Can do.

  An example with specific numerical values of the zoom lens having the above configuration is shown as Example 1 below. In the first embodiment, the object-side surface S3 of the second lens 2, the object-side surface S11 and the image-side surface S12 of the sixth lens 6 are each formed as an aspheric surface, and the other surfaces are formed into a spherical surface. Is formed.

Main specifications in the first embodiment are shown in Table 1, various numerical data (setting values) are shown in Table 2, numerical data relating to the aspherical surface are shown in Table 3, and each lens system at the wide-angle end, intermediate position, and telephoto end. Table 4 shows numerical data regarding the focal length (wide angle end fw, intermediate position fm, telephoto end ft) and distances (intervals) D2, D10, D18, D21, and D24 on the optical axis L.
The numerical data of conditional expressions (1) and (2) is
(1) fw / fG1 = 7.25 / 87.438 = 0.083,
(2) ν1 = 70.2.

  Further, aberration diagrams relating to spherical aberration, astigmatism, and distortion at the wide-angle end, the intermediate position, and the telephoto end are as shown in FIG. 3, FIG. 4, and FIG. 3 to 5, d indicates aberration due to the d line, F indicates aberration due to the F line, S indicates aberration on the sagittal plane, and M indicates aberration on the meridional plane.

  In Example 1 described above, the entire length of the lens system (the front surface S1 to the imaging surface P of the first lens 1) is 105.4 mm (constant) and the back focus (the thirteenth lens 13) at each position from wide angle to intermediate to telephoto. The air conversion distance from the rear surface S24 to the imaging plane P) is 7.02 mm to 8.25 mm to 15.94 mm, the zoom ratio (zoom magnification) is 4.86 (constant value), and the F number is 2.90 to 3.28 to 5.15, angle of view (2ω) is 77.3 ° to 51.4 ° to 17.5 °, wide angle of view, high zoom ratio, and excellent optical performance with various aberrations corrected A high zoom lens can be obtained.

  6 and 7 show another embodiment of the zoom lens according to the present invention. FIG. 6 is a basic configuration diagram, and FIG. 7 is a state diagram at a wide angle end, an intermediate position, and a telephoto end. This embodiment is basically the same as the above-described embodiment except that the number of lenses constituting the second lens group (II) is increased by one, and the description of the same configuration is omitted.

In this embodiment, as shown in FIG. 6, the second lens group (II) is arranged in order from the object side to the image plane side, the second lens 2 having negative refractive power, and has positive refractive power. A fourth lens 4 ′ having a negative refractive power and a third lens 3 ′, a fourth lens 4 ′ having a negative refractive power, a fifth lens 5 ′ having a negative refractive power, and a sixth lens 6 having a positive refractive power It is comprised by '.
As shown in FIG. 6, the third lens group (III) includes a seventh lens 7 having a positive refractive power and an aperture stop SD that defines a predetermined aperture, a negative aperture, which are arranged in order from the object side to the image plane side. An eighth lens 8 'having a refractive power of 9, a ninth lens 9' having a positive refractive power and being joined to the eighth lens 8 ', and a tenth lens 10' having a positive refractive power.
As shown in FIG. 6, the fourth lens group (IV) is joined to an eleventh lens 11 ′ and an eleventh lens 11 ′ having positive refractive power, which are arranged in order from the object side to the image plane side. The lens is composed of a twelfth lens 12 'having negative refractive power.
As shown in FIG. 6, the fifth lens group (V) is cemented to a thirteenth lens 13 ′ and a thirteenth lens 13 ′ having positive refractive power, which are arranged in order from the object side to the image plane side. The fourteenth lens 14 'has a negative refractive power.

  In the above configuration, a glass filter 15 serving as an infrared cut filter, a low-pass filter, or the like is disposed closer to the image plane side than the fifth lens group (V), that is, the fourteenth lens 14 ′. A CCD imaging plane P as a solid-state image sensor is disposed behind.

Here, in the first lens 1 to the 14th lens 14 'and the glass filter 15, as shown in FIG. 6, each surface is Si (i = 1 to 27), and the curvature radius of each surface Si is Ri ( i = 1 to 27), the refractive index with respect to the d-line is represented by Ni, and the Abbe number is represented by νi (i = 1 to 15).
Further, the distance (thickness, air interval) on each optical axis L from the first lens 1 to the glass filter 15 to the image plane P is represented by Di (i = 1 to 26), and the 14th lens 14 ′ The distance from the image plane side surface (rear surface) S25 to the image plane P is defined as back focus (air conversion distance), and the distance from the rear surface S27 of the glass filter 15 to the image plane P is represented by BF.

The third lens 3 'is a meniscus lens made of a glass material and having a concave surface S5 on the object side and a convex surface S6 on the image surface side.
The fourth lens 4 ′ is a biconcave lens formed of a glass material and bonded to the third lens 3 ′ with the concave surface S 6 facing the object side and the concave surface S 7 facing the image surface side.
The fifth lens 5 ′ is a biconcave lens made of a glass material and having a concave surface S8 on the object side and a concave surface S9 on the image side.
The sixth lens 6 ′ is a biconvex lens formed of a glass material and having a convex surface S10 on the object side and a convex surface S11 on the image surface side.

The seventh lens 7 'is a biconvex lens formed of a glass material and having a convex surface S12 on the object side and a convex surface S13 on the image side.
The eighth lens 8 ′ is a biconcave lens made of a glass material and having a concave surface S15 on the object side and a concave surface S16 on the image surface side.
The ninth lens 9 ′ is a biconvex lens formed of a glass material and bonded to the eighth lens 8 ′, with the convex surface S16 facing the object side and the convex surface S17 facing the image surface side.
The tenth lens 10 'is a biconvex lens made of a glass material and having a convex surface S18 on the object side and a convex surface S19 on the image side.

The eleventh lens 11 ′ is a biconvex lens made of a glass material and having a convex surface S 20 on the object side and a convex surface S 21 on the image side.
The twelfth lens 12 'is a biconcave lens formed of a glass material and bonded to the eleventh lens 11', with the concave surface S21 facing the object side and the concave surface S22 facing the image surface side.
The thirteenth lens 13 'is a biconvex lens made of a glass material and having a convex surface S23 on the object side and a convex surface S24 on the image side.
The fourteenth lens 14 ′ is a meniscus lens formed of a glass material and bonded to the thirteenth lens 13 ′ with the concave surface S 24 facing the object side and the convex surface S 25 facing the image surface side.

  An example with specific numerical values of the zoom lens having the above-described configuration is shown as Example 2 below. In the second embodiment, the object-side surface S3 of the second lens 2, the object-side surface S12 and the image-side surface S13 of the seventh lens 7 ′ are each formed as an aspheric surface, and the other surfaces are spherical surfaces. Is formed.

Main specifications in the second embodiment are shown in Table 5, various numerical data (setting values) are shown in Table 6, numerical data relating to aspheric surfaces are shown in Table 7, and each lens system at the wide angle end, intermediate position, and telephoto end. Table 8 shows numerical data regarding the focal length (wide angle end fw, intermediate position fm, telephoto end ft) and distances (intervals) D2, D11, D19, D22, D25 on the optical axis L.
The numerical data of conditional expressions (1) and (2) is
(1) fw / fG1 = 7.25 / 82.992 = 0.087,
(2) ν1 = 70.4.

  Further, aberration diagrams relating to spherical aberration, astigmatism, and distortion at the wide-angle end, the intermediate position, and the telephoto end are as shown in FIG. 8, FIG. 9, and FIG. 8 to 10, d indicates aberration due to the d-line, F indicates aberration due to the F-line, S indicates aberration on the sagittal plane, and M indicates aberration on the meridional plane.

  In Example 2 described above, the total length of the lens system (the front surface S1 to the imaging surface P of the first lens 1) is 104.6 mm (constant) and the back focus (the fourteenth lens 14) at each position from wide angle to intermediate to telephoto. 'Air conversion distance from rear surface S25 to imaging plane P) is 6.48 mm to 7.69 mm to 15.07 mm, zoom ratio is 4.86 (constant value), and F number is 2.89. Optical performance with various aberrations corrected satisfactorily with a wide angle of view and a high zoom ratio, with a field angle (2ω) of -7. High zoom lens can be obtained.

11 and 12 show still another embodiment of the zoom lens according to the present invention. FIG. 11 is a basic configuration diagram, and FIG. 12 is a state diagram at a wide angle end, an intermediate position, and a telephoto end. This embodiment is basically the same as the embodiment shown in FIG. 1 except that the lens constituting the fifth lens group (II) is changed, and the description of the same configuration is omitted.
In this embodiment, the fifth lens group (V) is arranged in order from the object side to the image plane side, as shown in FIG. It is composed of a thirteenth lens 13 ″ that is cemented with ″ and has a positive refractive power.

As shown in FIG. 11, the twelfth lens 12 ″ is a meniscus lens formed of a glass material and having a convex surface S22 on the object side and a concave surface S23 on the image side.
As shown in FIG. 11, the thirteenth lens 13 ″ is made of a glass material and is joined to the twelfth lens 12 ″. The biconvex lens has the convex surface S23 on the object side and the convex surface S24 on the image surface side. Shape lens.

  A specific numerical example of the zoom lens having the above configuration will be described below as a third example. In Example 3, the object-side surface S3 of the second lens 2, the object-side surface S11 and the image-side surface S12 of the sixth lens 6 are each formed as aspherical surfaces, and the other surfaces are spherical. Is formed.

Main specifications in the third embodiment are shown in Table 9, various numerical data (setting values) are shown in Table 10, numerical data relating to the aspherical surface are shown in Table 11, and each lens system at the wide-angle end, intermediate position, and telephoto end. Table 12 shows numerical data regarding the focal length (wide-angle end fw, intermediate position fm, telephoto end ft) and distances (intervals) D2, D10, D18, D21, and D24 on the optical axis L.
The numerical data of conditional expressions (1) and (2) is
(1) fw / fG1 = 7.25 / 85.661 = 0.085,
(2) ν1 = 70.2.

  Further, aberration diagrams relating to spherical aberration, astigmatism, and distortion at the wide-angle end, the intermediate position, and the telephoto end are as shown in FIG. 13, FIG. 14, and FIG. In FIG. 13 to FIG. 15, d represents the aberration due to the d-line, F represents the aberration due to the F-line, S represents the aberration on the sagittal plane, and M represents the aberration on the meridional plane.

  In Example 3 described above, the entire length of the lens system (the front surface S1 to the imaging surface P of the first lens 1) is 106.0 mm (constant) and the back focus (the thirteenth lens 13) at each position from wide angle to intermediate to telephoto. The distance in terms of air from the rear surface S24 to the image plane P) is 7.86 mm to 9.68 mm to 16.46 mm, the zoom ratio is 4.86 (a constant value), and the F number is 2. An optical system in which various aberrations are favorably corrected with a wide angle of view and a high zoom ratio, ranging from 87 to 3.28 to 5.02 and an angle of view (2ω) of 77.6 ° to 50.1 ° to 17.3 °. A high-performance zoom lens can be obtained.

  As described above, the zoom lens of the present invention can achieve a wide angle of view of about 75 ° at the wide-angle end while ensuring a high zoom magnification of about 5 times while achieving miniaturization and the like. A high-quality digital still camera and digital video camera that require miniaturization because they have high optical performance with an F number of about 2.8 and various aberrations corrected well over the entire zoom range. Of course, the present invention can be applied to other lens optical systems that perform zooming photography.

1 is a basic configuration diagram showing an embodiment of a zoom lens according to the present invention. FIG. FIGS. 2A and 2B illustrate a zooming operation of the zoom lens illustrated in FIG. 1, in which FIG. 1A is a state diagram at a wide angle end, FIG. 1B is a state diagram at an intermediate position, and FIG. In the zoom lens according to Example 1, aberration diagrams of spherical aberration, astigmatism, and distortion at the wide-angle end are shown. In the zoom lens according to Example 1, aberration diagrams of spherical aberration, astigmatism, and distortion at an intermediate position are shown. In the zoom lens according to Example 1, aberration diagrams of spherical aberration, astigmatism, and distortion at the telephoto end are shown. It is a basic block diagram which shows other embodiment of the zoom lens which concerns on this invention. FIGS. 7A and 6B illustrate a zooming operation of the zoom lens illustrated in FIG. 6, in which FIG. 6A is a state diagram at a wide-angle end, FIG. 6B is a state diagram at an intermediate position, and FIG. In the zoom lens according to Example 2, aberration diagrams of spherical aberration, astigmatism, and distortion at the wide-angle end are shown. In the zoom lens according to Example 2, aberration diagrams of spherical aberration, astigmatism, and distortion at an intermediate position are shown. In the zoom lens according to Example 2, aberration diagrams of spherical aberration, astigmatism, and distortion at the telephoto end are shown. FIG. 6 is a basic configuration diagram showing still another embodiment of a zoom lens according to the present invention. 11A and 11B illustrate a zooming operation of the zoom lens illustrated in FIG. 11, in which FIG. 11A is a state diagram at the wide-angle end, FIG. 11B is a state diagram at the intermediate position, and FIG. 11C is a state diagram at the telephoto end. In the zoom lens according to Example 3, aberration diagrams of spherical aberration, astigmatism, and distortion at the wide-angle end are shown. In the zoom lens according to Example 3, aberration diagrams of spherical aberration, astigmatism, and distortion at an intermediate position are shown. In the zoom lens according to Example 3, aberration diagrams of spherical aberration, astigmatism, and distortion at the telephoto end are shown.

Explanation of symbols

I 1st lens group II 2nd lens group III 3rd lens group IV 4th lens group V 5th lens group 1 1st lens (1st lens group)
2 Second lens (second lens group)
3, 3 'third lens (first lens group)
4,4 'Fourth lens (second lens group)
5,5 'fifth lens (second lens group)
6 Sixth lens (third lens group)
6 'sixth lens (second lens group)
7,7 'seventh lens (third lens group)
8,8 'eighth lens (third lens group)
9, 9 'ninth lens (third lens group)
10 10th lens (4th lens group)
10 '10th lens (third lens group)
11, 11 ′ Eleventh lens (fourth lens group)
12 12th lens (5th lens group)
12 '12th lens 12' (4th lens group)
13, 13 'thirteenth lens (fifth lens group)
14 '14th lens (5th lens group)
14, 15 Glass filter SD Aperture stop D1 to D26 Distance on optical axis R1 to R27 Radius of curvature S1 to S27 Surface fw Focal length fG1 of lens system at wide angle end Focal length ν1 of first lens group Abbe number L of first lens optical axis

Claims (5)

In order from the object side to the image plane side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a negative refractive power A fourth lens group, a fifth lens group having positive refractive power,
The first lens group is fixed, the second lens group is moved from the object side to the image plane side, and zooming is performed from the wide-angle end to the telephoto end, and the third lens group, the fourth lens group, and the fifth lens are performed. Aberration correction accompanying zooming by moving the group,
A zoom lens characterized by that. The first lens group includes a single first lens having a positive refractive power,
When the focal length of the lens system from the first lens group to the image plane at the wide angle end is fw, the focal length of the first lens group is fG1, and the Abbe number of the first lens is ν1, the following conditional expression ( The zoom lens according to claim 1, wherein 1) and (2) are satisfied.
(1) 0.05 <fw / fG1 <0.12
(2) ν1> 60 The second lens group includes a second lens having negative refractive power on the most object side,
The second lens has an aspherical surface on at least one of the object side surface and the image side surface.
The zoom lens according to claim 1, wherein the zoom lens is a zoom lens. The third lens group has at least one aspheric surface;
The zoom lens according to claim 1, wherein the zoom lens is a zoom lens. Focusing is performed by moving the fourth lens group.
The zoom lens according to claim 1, wherein the zoom lens is a zoom lens.

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