JP2013054191A - Zoom lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zoom lens which is compact in size and light in weight and is capable of maintaining high image formation performance, even when varying power, while maintaining a wide angle of view.SOLUTION: The zoom lens is configured by arranging, in order from an object side, a first lens group Ghaving positive refractive power, a second lens group Ghaving negative refractive power, an aperture diaphragm STP for regulating a predetermined aperture, a third lens group Ghaving positive refractive power, and a fourth lens group Ghaving positive refractive power. In particular, the second lens group Gis configured by arranging, in order from the object side, a first lens Lhaving an aspherical surface and negative refractive power, a second lens Lhaving negative refractive power, and a third lens Lhaving positive refractive power. The zoom lens satisfies a predetermined condition, so that the zoom lens can be reduced in size and weight and can obtain excellent image formation performance by effectively suppressing the occurrence of distortion over an entire variable power range.

Description

  The present invention relates to a compact and lightweight wide-angle zoom lens that is optimal for mounting on an imaging device such as a video camera or a digital camera.

  In recent years, digital cameras and the like are required to be further miniaturized and to have a high zoom ratio. In order to meet this requirement, a compact, high-magnification zoom lens has been proposed (for example, see Patent Document 1).

  The zoom lens described in Patent Document 1 focuses on the telephoto end where the F-number increases, and generates axial chromatic aberration at the telephoto end, and corrects distortion at which the aberration tends to be noticeable at the wide-angle end opposite to the telephoto end. The emphasis is on.

Japanese Patent No. 4503918

  By the way, in recent years, with the advancement of communication technology, so-called TV conference systems that can hold a conference while being away from each other are becoming popular. Therefore, when the zoom lens described in Patent Document 1 is used in a TV conference system, this zoom lens has an F number of about 3.8, and is not suitable for capturing an accurate image indoors. Further, since the lens constituting the first group moves, the lens barrel shape cannot be simplified. Furthermore, in order to achieve high resolution, additional lenses need to be added not only to the focus group but also to other lens groups, and the entire length of the optical system is extended, so that downsizing of the optical system is hindered.

  Furthermore, because of the nature of the TV conference system, the subject to be photographed is a person who is relatively close to the camera, so it is necessary to take a wide-angle image. Therefore, a zoom lens that can obtain high resolution even when zooming at a wide angle is desired. However, conventional zoom lenses such as those described in Patent Document 1 have a problem that distortion occurs greatly when zooming at a wide angle.

  An object of the present invention is to provide a zoom lens that is small and lightweight and can maintain high imaging performance even when zooming while maintaining a wide angle of view in order to eliminate the above-described problems caused by the conventional technology. To do.

In order to solve the above-described problems and achieve the object, a zoom lens according to the present invention includes a first lens group having a positive refractive power and a second lens having a negative refractive power, which are arranged in order from the object side. And a third lens group having a positive refractive power, and the second lens group is disposed in order from the object side, and has a negative refractive power in which an aspheric surface is formed on the object side A first lens having negative refractive power, a third lens having negative refractive power, and a third lens having positive refractive power, each of the second lens group and the third lens group being close to the aperture stop. The zoom lens is zoomed from the wide-angle end to the telephoto end to satisfy the following conditional expression.
(1) -1.1 <F2 / F3 <-0.5
(2) -0.3 <F2 / F1 <0
(3) | α1 |> 55
Where F1 is the focal length of the first lens group, F2 is the focal length of the second lens group, F3 is the focal length of the third lens group, and α1 is the emission of the principal ray on the final lens surface of the first lens. Indicates a corner.

  According to the present invention, it is possible to provide a zoom lens that is small and lightweight and can maintain a bright and high imaging performance even when zooming while maintaining a wide angle of view. In particular, this zoom lens can effectively suppress distortion over the entire zoom range from the wide-angle end to the telephoto end.

Furthermore, the zoom lens according to the present invention is characterized in that, in the above invention, an aspheric surface is formed on the object side of the first lens constituting the second lens group, and the following conditional expression is satisfied: .
(4) SA1 / F2 <−0.015
However, F2 is the focal length of the second lens group, and SA1 is a spherical shape corresponding to 90% of one side of the aspherical part of the lens on the first lens object side constituting the second lens group. The sag amount in the spherical shape (the direction is a positive direction of light travel).

  According to the present invention, in particular, this zoom lens can effectively suppress distortion over the entire zooming range from the wide-angle end to the telephoto end.

Furthermore, the zoom lens according to the present invention is characterized in that, in the above invention, an aspheric surface is formed on the object side of the first lens constituting the second lens group, and the following conditional expression is satisfied: .
(5) -2.0 <F21 × DDX12 <4.0
However, F21 shows the focal length of the 1st lens which comprises the said 2nd lens group, DDX12 shows the secondary differential amount of the aspherical curve of the object side effective diameter of the 1st lens which comprises the said 2nd lens group.

  According to the present invention, it is possible to effectively correct various aberrations such as distortion, astigmatism, and chromatic aberration of magnification while configuring an optical system with a small number of lenses.

Furthermore, the zoom lens according to the present invention is characterized in that, in the above-mentioned invention, the first lens constituting the second lens group has an aspheric surface on the image side, and satisfies the following conditional expression: To do.
(6) -1.5 <F21 × DDX11 <0.5
(7) −5.0 <F21 × DDX21 <−0.5
(8) −4.0 <F21 × DDX22 <0
However, DDX11 is the second derivative of the aspherical curve at the center of the object side surface of the first lens constituting the second lens group, and DDX21 is the aspherical curve at the center of the image side surface of the first lens constituting the second lens group. DDX22 represents the second derivative of the aspheric curve of the effective image side diameter of the first lens constituting the second lens.

  According to the present invention, it is possible to effectively correct various aberrations such as distortion, astigmatism, and chromatic aberration of magnification while configuring an optical system with a small number of lenses.

Furthermore, in the zoom lens according to the present invention, in the above invention, the first lens group includes a cemented lens including a first lens having a negative refractive power and a second lens having a positive refractive power. It satisfies the conditional expression.
(9) nd1> 1.9
(10) nd2> 1.77
(11) νd2−νd1> 17
However, nd1 is the refractive index of the first lens constituting the first lens group with respect to the d-line, nd2 is the refractive index of the second lens constituting the first lens group with respect to the d-line, and νd1 is the first lens group. Abbe number with respect to d-line of the first lens constituting the lens, and νd2 indicate Abbe number with respect to d-line of the second lens constituting the first lens group.

  According to the present invention, various aberrations can be effectively corrected while achieving a reduction in the diameter of the optical system.

Furthermore, the zoom lens according to the present invention is the zoom lens according to the present invention, wherein the third lens group is arranged in order from the object side, the first lens having a positive refractive power, and the second lens having a positive refractive power; A cemented lens including a third lens having a negative refractive power and a fourth lens having a positive refractive power formed with an aspheric surface are satisfied, and the following conditional expression is satisfied.
(12) 25 <(F33R2 / F34R1) × (FF34 / D3) <60
However, F33R2 is the curvature of the image side surface of the third lens that constitutes the third lens group, F34R1 is the curvature of the object side surface of the fourth lens that constitutes the third lens group, and FF34 is the third lens group. The focal length of the fourth lens, D3, indicates the distance between the third lens and the fourth lens constituting the third lens group.

  According to the present invention, various aberrations (particularly astigmatism) can be effectively corrected while simplifying the production of the optical system.

Furthermore, the zoom lens according to the present invention is characterized in that, in the above invention, the fourth lens group including a positive lens is provided on the image side of the third lens group, and satisfies the following conditional expression: To do.
(13) 0.8 <F4 / F41 <1.4
(14) νd> 60
Where F4 is the focal length of the fourth lens group, F41 is the focal length of the positive lens included in the fourth lens group, and νd is the Abbe number of the positive lens included in the fourth lens group with respect to the d-line.

  According to the present invention, astigmatism, coma aberration, and chromatic aberration of magnification can be more effectively corrected.

  According to the present invention, there is an effect that it is possible to provide a zoom lens that is small and lightweight and can maintain high imaging performance even when zooming is performed while maintaining a wide angle of view.

FIG. 3 is a cross-sectional view along the optical axis showing the configuration of the zoom lens according to Example 1; FIG. 6 is a diagram illustrating all aberrations at the wide-angle end of the zoom lens according to Example 1; FIG. 6 is a diagram illustrating various aberrations in an intermediate region of the zoom lens according to the first example. FIG. 7 is a diagram illustrating all aberrations at the telephoto end of the zoom lens according to Example 1; FIG. 6 is a cross-sectional view along the optical axis showing the configuration of a zoom lens according to Example 2; FIG. 10 is a diagram illustrating all aberrations at the wide-angle end of the zoom lens according to Example 2; FIG. 6 is a diagram illustrating various aberrations in an intermediate area of the zoom lens according to the second example. FIG. 10 is a diagram illustrating all aberrations at the telephoto end of the zoom lens according to Example 2; FIG. 6 is a cross-sectional view along the optical axis showing the configuration of a zoom lens according to Example 3; FIG. 10 is a diagram illustrating all aberrations at the wide-angle end of the zoom lens according to Example 3; FIG. 9 is a diagram illustrating various aberrations in an intermediate area of the zoom lens according to the third example. FIG. 10 is a diagram illustrating all aberrations at the telephoto end of the zoom lens according to Example 3;

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

  The zoom lens according to the present invention has a first lens group having a positive refractive power, a second lens group having a negative refractive power, an aperture stop, and a positive refractive power, which are arranged in order from the object side. And a third lens group. Then, zooming from the wide-angle end to the telephoto end is performed by bringing the second lens group and the third lens group close to the aperture stop. The positions of the first lens group and the aperture stop are always fixed.

  In the zoom lens according to the present invention, by fixing the position of the first lens group, it is easy to prevent the entry of dust and the like from the outside. In addition, by fixing the position of the aperture stop, the drive group can be limited, and the mechanical configuration that controls the drive of the drive group can be simplified. By simplifying the mechanical structure, the number of mechanical parts can be reduced. In addition, since the position of the aperture stop is fixed, the configuration of the aperture stop can be simplified. This simplification can reduce the variation in component accuracy, and the component accuracy including the diaphragm can be suppressed to several μm or less, so that a high-resolution full HD image quality of 1080 or more can be achieved.

  An object of the present invention is to provide a zoom lens that is small and light and can maintain a bright and high imaging performance even when zooming while maintaining a wide angle of view. Therefore, in order to achieve this purpose, various conditions as shown below are set.

First, in the zoom lens according to the present invention, the second lens group has a negative refractive power and a first lens having a negative refractive power in which an aspheric surface is formed on the object side, which are arranged in order from the object side. A second lens and a third lens having a positive refractive power are provided. At that time, the focal length of the first lens group is F1, the focal length of the second lens group is F2, the focal length of the third lens group is F3, and the exit angle of the principal ray on the final lens surface of the first lens group is α1. When doing so, it is preferable that the following conditional expression is satisfied.
(1) -1.1 <F2 / F3 <-0.5
(2) -0.3 <F2 / F1 <0
(3) | α1 |> 55

  Conditional expressions (1), (2), and (3) indicate conditions for shortening the overall length of the optical system, ensuring a wide angle of view, and effectively correcting various aberrations. If the lower limit of conditional expression (1) is not reached, the occurrence of various aberrations becomes significant, making correction difficult. Further, the sensitivity of the optical system is increased, and even if a slight lens position shift occurs, the imaging performance of the optical system is significantly deteriorated. For this reason, it becomes difficult to realize an optical system with excellent imaging performance. On the other hand, if the upper limit of conditional expression (1) is exceeded, it is difficult to correct various aberrations (especially spherical aberration and coma aberration). In this state, when various aberrations are corrected, a new lens must be added to the optical system, which leads to hindering the shortening of the total length of the optical system, which is not preferable. If the lower limit of conditional expression (2) is not reached, the diameter of the lens constituting the first lens group becomes large, which increases the weight of the optical system and increases the lens cost. In addition, it becomes difficult to sufficiently correct the chromatic aberration of magnification. On the other hand, if the upper limit of conditional expression (2) is exceeded, the curvature of the lenses constituting the second lens group or the third lens group becomes tight, and the occurrence of various aberrations becomes significant. In order to correct this, it is necessary to add a new lens in the optical system, which hinders shortening of the total length of the optical system. If the lower limit of conditional expression (3) is not reached, it will be difficult to achieve downsizing. In the state of downsizing, the occurrence of various aberrations on the wide side becomes remarkable. In the case of a wide-angle lens, there is an effect of preventing the light beam entering the lens on the first surface from reaching a position having a tight incident angle with respect to the lens surface.

In addition, if the conditional expressions (1) and (2) satisfy the following ranges, more favorable effects can be expected.
(1) ′ −0.8 <F2 / F3 <−0.6
(2) ′ −0.1 <F2 / F1 <0
By satisfying the ranges defined by the conditional expressions (1) ′ and (2) ′, the occurrence of spherical aberration and coma aberration can be suppressed more satisfactorily.

Furthermore, in the zoom lens according to the present invention, the sag amount—aspherical shape, which is a spherical shape corresponding to 0.9% on one side of the aspherical portion of the lens on the side surface of the first lens object constituting the second lens group. When the sag amount (direction is positive in the light traveling direction) is SA1, it is preferable to satisfy the following equation.
(4) SA1 / F2 <−0.015

  Conditional expression (4) is a condition for effectively correcting various aberrations such as astigmatism and lateral chromatic aberration while effectively suppressing the occurrence of distortion by the first lens of the second lens group. It is shown. If the upper limit of conditional expression (4) is exceeded, it will be difficult to effectively correct distortion over the entire zoom range from the wide-angle end to the telephoto end while suppressing the occurrence of astigmatism. In addition, the processing difficulty of the first lens increases, leading to an increase in the cost of the optical system.

In addition, if the said conditional expression (4) satisfies the range shown next, a more preferable effect can be anticipated.
(4) 'SA1 / F2 <−0.018
By satisfying the range defined by the conditional expression (4) ′, it is possible to more effectively suppress the occurrence of spherical aberration, astigmatism, and distortion.

Furthermore, in the zoom lens according to the present invention, the focal length of the first lens constituting the second lens group is F21, and the second derivative of the aspherical curve of the effective diameter of the object side surface of the first lens constituting the second lens group. Is preferably DDX12, the following conditional expression is preferably satisfied.
(5) -2.0 <F21 × DDX12 <4.0

  Conditional expression (5) is a condition for effectively correcting various aberrations such as astigmatism and lateral chromatic aberration while effectively suppressing the occurrence of distortion by the first lens of the second lens group. It is shown. In conditional expression (5), the second derivative of the aspheric curve (representing the direction of change in the inclination of the aspheric surface) DDX is the distance from the apex of the lens surface to the optical axis direction x, and the height from the optical axis. This is a value obtained by d (dx / dy) / dy, where y is y and the light traveling direction is positive. If the lower limit of conditional expression (5) is not reached, it will be difficult to effectively correct distortion over the entire zoom range from the wide-angle end to the telephoto end while suppressing the occurrence of astigmatism. On the other hand, if the upper limit of conditional expression (5) is exceeded, the processing difficulty of the first lens in the second lens group increases and the cost of the optical system increases. In addition, the sensitivity of the lens becomes strong, and the imaging performance of the optical system significantly deteriorates even if a slight lens position shift occurs. For this reason, it becomes difficult to realize an optical system with excellent imaging performance.

In addition, the said conditional expression (5) can anticipate a more preferable effect, if the range shown next is satisfied.
(5) ′ −0.5 <F21 × DDX12 <2.1
By satisfying the range defined by the conditional expression (5) ′, it is possible to more effectively suppress the occurrence of distortion while suppressing astigmatism.

Furthermore, in the zoom lens according to the present invention, an aspherical surface is preferably formed on the image side of the first lens constituting the second lens group. Then, the focal length of the first lens constituting the second lens group is F21, and the two aspherical curves at the object side surface center (position of height 0.01 mm from the axis) of the first lens constituting the second lens group The secondary differential amount is DDX11, the secondary differential amount of the aspherical curve at the center of the image side surface of the first lens constituting the second lens group (position of height 0.01 mm from the axis) is DDX21, and the second lens is configured. When the second derivative of the aspherical curve of the image side effective diameter of the first lens is DDX22, it is preferable that the following conditional expression is satisfied.
(6) -1.5 <F21 × DDX11 <0.5
(7) −5.0 <F21 × DDX21 <−0.5
(8) −4.0 <F21 × DDX22 <0

  Conditional expressions (6) and (7) show conditions for satisfactorily correcting spherical aberration while effectively suppressing the occurrence of distortion over the entire zoom range. If either one of conditional expressions (6) and (7) is out of the specified range, it will be difficult to correct spherical aberration well. If the upper limit of conditional expressions (6) and (7) is exceeded, spherical aberration can be suppressed, but it is difficult to satisfactorily correct astigmatism and chromatic aberration. Further, since spherical aberration cannot be effectively suppressed, it is necessary to compensate with another lens, and it is necessary to add a lens in order to maintain optical performance. Conditional expression (8) represents a condition for satisfactorily correcting astigmatism and curvature of field while effectively suppressing the occurrence of distortion over the entire zoom range. If it is out of the range defined in the conditional expression (8), it is difficult to satisfactorily correct astigmatism and field curvature. In order to correct various aberrations that have become prominent by deviating from the range defined by conditional expressions (6), (7), and (8), it is necessary to add a new lens to the optical system. This is not preferable because it leads to obstructing the shortening of the total length of the optical system.

The conditional expressions (6) and (7) can be expected to have a more preferable effect when the following range is satisfied.
(6) ′ − 1.1 <F21 × DDX11 <0.1
(7) ′ −2.5 <F21 × DDX21 <−1.0
By satisfying the ranges defined by the conditional expressions (6) ′ and (7) ′, it is possible to more effectively suppress the occurrence of spherical aberration, astigmatism, and distortion.

Further, when the conditional expression (8) satisfies the following range, a more preferable effect can be expected.
(8) ′ −2.0 <F21 × DDX22 <−0.5
By satisfying the range defined by the conditional expression (8) ′, it is possible to more effectively suppress the occurrence of astigmatism while effectively suppressing the occurrence of distortion.

Furthermore, in the zoom lens according to the present invention, the first lens group includes a cemented lens including a first lens having a negative refractive power and a second lens having a positive refractive power. The refractive index for the d-line of the first lens constituting the first lens group is nd1, the refractive index for the d-line of the second lens constituting the first lens group is nd2, and the first lens constituting the first lens group. When the Abbe number with respect to the d-line is νd1, and the Abbe number with respect to the d-line of the second lens constituting the first lens group is νd2, it is preferable that the following conditional expression is satisfied.
(9) nd1> 1.9
(10) nd2> 1.77
(11) νd2−νd1> 17

  Conditional expressions (9) and (10) show conditions for effectively reducing the chromatic aberration and astigmatism of the magnification by reducing the diameter of the first lens unit. If either one of conditional expressions (9) and (10) is below the lower limit, it will be difficult to satisfactorily correct lateral chromatic aberration and astigmatism. In this state, in order to satisfactorily correct chromatic aberration of magnification and astigmatism, the diameter of the first lens group must be increased, which hinders the reduction in size and weight of the optical system. Conditional expression (11) represents a condition for improving the imaging performance of the optical system by suppressing the occurrence of various aberrations (particularly, chromatic aberration of magnification). If the lower limit of conditional expression (11) is not reached, various aberrations cannot be corrected satisfactorily. In particular, the occurrence of lateral chromatic aberration becomes significant.

Further, in the zoom lens according to the present invention, the third lens group includes a first lens having a positive refractive power, a second lens having a positive refractive power, and a negative refractive power, which are arranged in order from the object side. And a fourth lens having a positive refractive power in which an aspherical surface is formed. Then, the curvature of the image side surface of the third lens constituting the third lens group is F33R2, the curvature of the object side surface of the fourth lens constituting the third lens group is F34R1, and the focal point of the fourth lens constituting the third lens group. When the distance is FF34 and the distance between the third lens and the fourth lens constituting the third lens group is D3, it is preferable that the following conditional expression is satisfied.
(12) 25 <(F33R2 / F34R1) × (FF34 / D3) <60

  Conditional expression (12) indicates a condition for appropriately setting the distance between the third lens and the fourth lens constituting the third lens group to suppress the occurrence of various aberrations (particularly astigmatism). Is. If the lower limit of conditional expression (12) is not reached, the distance between the third lens and the fourth lens in the third lens group becomes too wide, and the occurrence of various aberrations (particularly astigmatism) becomes significant. On the other hand, if the upper limit in conditional expression (12) is exceeded, the distance between the third lens and the fourth lens in the third lens group becomes too narrow, and there is a situation in which these lenses easily collide with each other in the optical system manufacturing process. This is not preferable because the manufacturing difficulty of the optical system increases. Also, ghosts are likely to occur.

In addition, if the said conditional expression (12) satisfies the range shown next, a more preferable effect can be anticipated.
(12) ′ 30 <(F33R2 / F34R1) × (FF34 / D3) <50
By satisfying the range defined by the conditional expression (12) ′, it is possible to more effectively suppress the generation of astigmatism and coma while suppressing distortion.

Further, in the zoom lens according to the present invention, when it is necessary to correct astigmatism, coma aberration, and chromatic aberration of magnification while further suppressing the occurrence of distortion, a positive lens is provided on the image side of the third lens group. A fourth lens group configured to be included may be provided. In this case, when the focal length of the fourth lens group is F4, the focal length of the positive lens included in the fourth lens group is F41, and the Abbe number with respect to the d-line of the positive lens included in the fourth lens group is νd. It is preferable that the following conditional expression is satisfied.
(13) 0.8 <F4 / F41 <1.4
(14) νd> 60

  Conditional expression (13) shows the conditions necessary for correcting astigmatism and coma aberration more satisfactorily. If the lower limit of conditional expression (13) is not reached, the sensitivity of the positive lens included in the fourth lens group becomes strong, and the imaging performance of the optical system is significantly deteriorated even if a slight lens position shift occurs. . On the other hand, if the upper limit of conditional expression (13) is exceeded, astigmatism cannot be corrected sufficiently. In this state, in order to sufficiently correct astigmatism, it is necessary to add a new lens to the fourth lens group, which leads to obstructing the shortening of the total length of the optical system, which is not preferable. Conditional expression (14) represents a condition necessary for correcting chromatic aberration of magnification more satisfactorily. If the lower limit of conditional expression (14) is not reached, the occurrence of lateral chromatic aberration becomes significant.

  As described above, the zoom lens according to the present invention can be reduced in size and weight by using a lens with an aspherical surface formed as appropriate and satisfying the above conditional expressions. Even when zooming is performed while maintaining a wide angle of view, high imaging performance can be maintained. In particular, it is excellent in suppressing the occurrence of distortion over the entire zooming range from the wide-angle end to the telephoto end. For this reason, an optical system capable of obtaining a bright and clear image can be realized.

  Embodiments of the zoom lens according to the present invention will be described below in detail with reference to the drawings. The present invention is not limited to the following examples.

FIG. 1 is a cross-sectional view along the optical axis showing the configuration of the zoom lens according to the first embodiment. This zoom lens includes, in order from the object side (not shown), a first lens group G ₁₁ having a positive refractive power, a second lens group G ₁₂ having a negative refractive power, and an aperture stop STP that defines a predetermined aperture. The third lens group G ₁₃ having positive refractive power and the fourth lens group G ₁₄ having positive refractive power are arranged. Between the fourth lens group G ₁₄ and the image plane IMG, a cover glass CG is disposed. The cover glass CG is arranged as necessary, and can be omitted if unnecessary. Note that a light receiving surface of an image sensor such as a CCD or a CMOS is disposed on the imaging plane IMG.

The first lens group G ₁₁ includes a first lens L ₁₁₁ having a negative refractive power and a second lens L ₁₁₂ having a positive refractive power arranged in order from the object side. The first lens L ₁₁₁ and the second lens L ₁₁₂ are cemented.

The second lens group G ₁₂ includes, in order from the object side, a first lens L ₁₂₁ having a negative refractive power, a second lens L ₁₂₂ having a negative refractive power, and a third lens L ₁₂₃ having a positive refractive power. Are arranged. Aspheric surfaces are formed on both surfaces of the first lens L ₁₂₁ .

The third lens group G ₁₃ includes, in order from the object side, a first lens L ₁₃₁ having a positive refractive power, a second lens L ₁₃₂ having a positive refractive power, and a third lens L ₁₃₃ having a negative refractive power. And a fourth lens L ₁₃₄ having a positive refractive power. The second lens L ₁₃₂ and the third lens L ₁₃₃ are cemented. In addition, aspheric surfaces are formed on both surfaces of the fourth lens L ₁₃₄ , respectively.

The fourth lens group G ₁₄ is constituted by a positive lens L _141.

In this zoom lens, zooming from the wide-angle end to the telephoto end is performed by bringing the second lens group G ₁₂ and the third lens group G ₁₃ close to the aperture stop STP. The first lens group G ₁₁ and the aperture stop STP is fixed at all times.

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

Focal length of the entire zoom lens = 3.05 (wide-angle end) to 4.80 (middle range) to 7.40 (telephoto end)
F-number = 2.0 (wide-angle end) to 2.2 (middle range) to 2.8 (telephoto end)
Half angle of view (ω) = 46.2 (wide-angle end) to 31.2 (middle range) to 21.6 (telephoto end)
The focal length of the first lens group G ₁₁ (F1) = 64.0
Focal length of the second lens group G ₁₂ (F2) = - 6.92
Focal length of the third lens group G ₁₃ (F3) = 9.49
Focal length of the fourth lens group G ₁₄ (F4) = 33.5

(Lens data)
r ₁ = 38.2191
d ₁ = 1.000 nd ₁ = 1.94594 νd ₁ = 17.98
r ₂ = 29.4856
d ₂ = 4.100 nd ₂ = 1.77250 νd ₂ = 49.62
r ₃ = 219.6467
d ₃ = D (3) (variable)
r ₄ = 42.6536 (aspherical surface)
d ₄ = 1.100 nd ₃ = 1.85135 νd ₃ = 40.10
r ₅ = 4.7790 (aspherical surface)
d ₅ = 3.463
r ₆ = -15.3993
d ₆ = 0.600 nd ₄ = 1.61800 νd ₄ = 63.39
r ₇ = 8.8922
d ₇ = 0.876
r ₈ = 12.3012
d ₈ = 3.000 nd ₅ = 1.91713 νd ₅ = 29.93
r ₉ = -46.4996
d ₉ = D (9) (variable)
r ₁₀ = ∞ (aperture)
d ₁₀ = D (10) (variable)
r ₁₁ = 9.3124
d ₁₁ = 2.566 nd ₆ = 1.61800 νd ₆ = 63.39
r ₁₂ = -53.7350
d ₁₂ = 0.100
r ₁₃ = 7.5000
d ₁₃ = 4,500 nd ₇ = 1.49700 νd ₇ = 81.61
r ₁₄ = -9.9284
d ₁₄ = 0.500 nd ₈ = 1.90366 νd ₈ = 31.31
r ₁₅ = 7.7818
d ₁₅ = 0.200
r ₁₆ = 7.5000 (aspherical surface)
d ₁₆ = 4.308 nd ₉ = 1.59201 νd ₉ = 67.02
r ₁₇ = -13.8603 (aspherical surface)
d ₁₇ = D (17) (variable)
r ₁₈ = 24.7549
d ₁₈ = 2.759 nd ₁₀ = 1.55831 νd ₁₀ = 66.03
r ₁₉ = -73.0356
d ₁₉ = 1.000
r ₂₀ = ∞
d ₂₀ = 1.010 nd ₁₁ = 1.51633 νd ₁₁ = 64.14
r ₂₁ = ∞
d ₂₁ = BF (back focus)
r ₂₂ = ∞ (imaging plane)

Cone coefficient (K) and aspheric coefficient (B, C, D, E)
(Fourth surface)
K = 11.3437,
B = -1.02340 × 10 ^-4 ,
C = 1.17252 × 10 ⁻⁶ , D = −2.03850 × 10 ⁻⁸ ,
E = 9.71254 × 10 ^-11
(5th page)
K = 0.2429,
B = 2.21226 × 10 ^-4 ,
C = -6.58742 × 10 ⁻⁶ , D = 7.40842 × 10 ⁻⁷ ,
E = -2.40908 × 10 ^-8
(16th surface)
K = -3.4249,
B = 4.57614 × 10 ^-4 ,
C = -1.14616 × 10 ⁻⁵ , D = 3.20281 × 10 ⁻⁷ ,
E = 3.34324 × 10 ^-8
(Seventeenth surface)
K = 3.3228,
B = 9.59116 × 10 ^-4 ,
C = 2.98095 × 10 ⁻⁵ , D = -1.70593 × 10 ⁻⁶ ,
E = 1.45002 × 10 ^-7

(Scaled data)
Wide angle end Intermediate range Telephoto end
D (3) 1.700 7.147 10.017
D (9) 10.714 5.267 2.397
D (10) 4.977 3.429 1.030
D (17) 1.000 2.548 4.947
BF 0.53 0.53 0.53

(Numerical values related to conditional expression (1))
F2 / F3 = -0.729

(Numerical value related to conditional expression (2))
F2 / F1 = -0.108

(Numerical values related to conditional expression (3))
| Α1 | = 65.7

(Numerical values related to conditional expression (4))
SA1 = 0.138
SA1 / F2 = -0.020

(Numerical values for conditional expression (5))
F21 (a focal length of the first lens L ₁₂₁₎ = - 6.41
DDX12 (secondary derivative of the aspheric curve of the object side effective diameter of the first lens L ₁₂₁ ) = − 0.01726
F21 × DDX12 = 0.111

(Numerical values related to conditional expression (6))
DDX11 (second derivative of the aspheric curve of the object side surface center of the first lens L ₁₂₁₎ = 0.0234
F21 × DDX11 = -0.15

(Numerical values related to conditional expression (7))
DDX21 (secondary derivative of the aspheric curve at the center of the image forming surface IMG of the first lens L ₁₂₁ ) = 0.2092
F21 × DDX21 = -1.34

(Numerical value related to conditional expression (8))
DDX22 (secondary derivative of the aspherical curve of the effective diameter of the imaging surface IMG side surface of the first lens L ₁₂₁ ) = 0.2058
F21 × DDX22 = -1.32

(Numerical values related to conditional expression (9))
nd1 (refractive index of the first lens L ₁₁₁ with respect to the d-line) = 1.94594

(Numerical values related to conditional expression (10))
nd2 (refractive index of the second lens L ₁₁₂ with respect to the d line) = 1.77250

(Numerical value related to conditional expression (11))
νd1 (Abbe number of the first lens L ₁₁₁ with respect to the d-line) = 17.98
νd2 (Abbe number of the second lens L ₁₁₂ with respect to the d-line) = 49.62
νd2−νd1 = 31.64

(Numerical values for conditional expression (12))
F33R2 (the curvature of the image side surface of the third lens L ₁₃₃ ) = 7.7801
F34R1 (curvature of the object side surface of the fourth lens L ₁₃₄₎ = 7.5
FF 34 (focal length of the fourth lens L ₁₃₄₎ = 8.87
D3 (distance between the third lens L ₁₃₃ and the fourth lens L ₁₃₄ ) = 0.2
(F33R2 / F34R1) × (F34 / D3) = 46.09

(Numerical value related to conditional expression (13))
F41 (focal length of positive lens L ₁₄₁ ) = 33.5
F4 / F41 = 1

(Numerical value related to conditional expression (14))
νd (Abbe number with respect to d-line of positive lens L ₁₄₁ ) = 66.03

  FIG. 2 is a diagram illustrating various aberrations at the wide-angle end of the zoom lens according to the first example. FIG. 3 is a diagram illustrating various aberrations in the intermediate range of the zoom lens according to the first example. FIG. 4 is a diagram illustrating various aberrations at the telephoto end of the zoom lens according to the first example. In the figure, g represents g-line (λ = 435.84 nm), d represents d-line (λ = 587.56 nm), and C represents aberration at a wavelength corresponding to C-line (λ = 656.28 nm). S and M in the astigmatism diagram represent aberrations with respect to the sagittal image surface and the meridional image surface, respectively.

FIG. 5 is a cross-sectional view along the optical axis showing the configuration of the zoom lens according to the second embodiment. This zoom lens includes, in order from the object side (not shown), a first lens group G ₂₁ having a positive refractive power, a second lens group G ₂₂ having a negative refractive power, and an aperture stop STP that defines a predetermined aperture. , a third lens group G ₂₃ having a positive refractive power, is configured are arranged. Between the third lens group G ₂₃ and the image plane IMG, a cover glass CG is disposed. The cover glass CG is arranged as necessary, and can be omitted if unnecessary. Note that a light receiving surface of an image sensor such as a CCD or a CMOS is disposed on the imaging plane IMG.

The first lens group G ₂₁ includes a first lens L ₂₁₁ having a negative refractive power and a second lens L ₂₁₂ having a positive refractive power arranged in order from the object side. The first lens L ₂₁₁ and the second lens L ₂₁₂ are cemented.

The second lens group G ₂₂ includes, in order from the object side, a first lens L ₂₂₁ having a negative refractive power, a second lens L ₂₂₂ having a negative refractive power, and a third lens L ₂₂₃ having a positive refractive power. Are arranged. Aspheric surfaces are formed on both surfaces of the first lens L ₂₂₁ .

The third lens group G ₂₃ includes, in order from the object side, a first lens L ₂₃₁ having a positive refractive power, a second lens L ₂₃₂ having a positive refractive power, and a third lens L ₂₃₃ having a negative refractive power. And a fourth lens L ₂₃₄ having a positive refractive power. The second lens L ₂₃₂ and the third lens L ₂₃₃ are cemented. Further, aspheric surfaces are formed on both surfaces of the first lens L ₂₃₁ and both surfaces of the fourth lens L ₂₃₄ , respectively.

In this zoom lens, zooming from the wide-angle end to the telephoto end is performed by bringing the second lens group G ₂₂ and the third lens group G ₂₃ closer to the aperture stop STP. The first lens group G ₂₁ and the aperture stop STP are always fixed.

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

Focal length of the entire zoom lens = 3.05 (wide-angle end) to 4.80 (middle range) to 7.40 (telephoto end)
F-number = 2.0 (wide-angle end) to 2.2 (middle range) to 2.8 (telephoto end)
Half angle of view (ω) = 46.3 (wide-angle end) to 31.2 (middle range) to 21.6 (telephoto end)
Focal length (F1) of the first lens group G ₂₁ = 124.1
Focal length of the second lens group G ₂₂ (F2) = - 7.45
Focal length of the third lens group G ₂₃ (F3) = 9.08

(Lens data)
r ₁ = 75.7837
d ₁ = 1.000 nd ₁ = 1.94594 νd ₁ = 17.98
r ₂ = 47.7430
d ₂ = 3.253 nd ₂ = 1.90979 νd ₂ = 35.31
r ₃ = 241.0295
d ₃ = D (3) (variable)
r ₄ = 8.8503 (aspherical surface)
d ₄ = 1.100 nd ₃ = 1.85135 νd ₃ = 40.10
r ₅ = 4.1163 (aspherical surface)
d ₅ = 4.520
r ₆ = -39.6613
d ₆ = 0.500 nd ₄ = 1.61800 νd ₄ = 63.39
r ₇ = 6.6338
d ₇ = 1.129
r ₈ = 8.6350
d ₈ = 2.752 nd ₅ = 1.67835 νd ₅ = 28.25
r ₉ = 83.6436
d ₉ = D (9) (variable)
r ₁₀ = ∞ (aperture)
d ₁₀ = D (10) (variable)
r ₁₁ = 8.2885 (aspherical surface)
d ₁₁ = 2.797 nd ₆ = 1.61881 νd ₆ = 63.85
r ₁₂ = -37.2005 (aspherical surface)
d ₁₂ = 0.100
r ₁₃ = 9.5592
d ₁₃ = 3.968 nd ₇ = 1.49700 νd ₇ = 81.61
r ₁₄ = -16.0463
d ₁₄ = 0.500 nd ₈ = 1.90366 νd ₈ = 31.31
r ₁₅ = 6.5239
d ₁₅ = 0.200
r ₁₆ = 7.5000 (aspherical surface)
d ₁₆ = 3.142 nd ₉ = 1.59201 νd ₉ = 67.02
r ₁₇ = -9.1695 (aspherical surface)
d ₁₇ = D (17) (variable)
r ₁₈ = ∞
d ₁₈ = 1.010 nd ₁₀ = 1.51633 νd ₁₀ = 64.14
r ₁₉ = ∞
d ₁₉ = BF (back focus)
r ₂₀ = ∞ (imaging plane)

Cone coefficient (K) and aspheric coefficient (B, C, D, E)
(Fourth surface)
K = -2.2810,
B = -1.96644 × 10 ^-4 ,
C = 2.26947 × 10 ⁻⁶ , D = −2.007258 × 10 ⁻⁸ ,
E = 7.25031 × 10 ^-11
(5th page)
K = 0.0766,
B = -1.55174 × 10 ^-4 ,
C = -3.85958 × 10 ⁻⁶ , D = 2.32454 × 10 ⁻⁷ ,
E = -7.79221 × 10 ^-9
(11th page)
K = 0.9213,
B = -8.14375 × 10 ^-6 ,
C = -1.37839 × 10 ⁻⁶ , D = 2.72988 × 10 ⁻⁸ ,
E = 1.87790 × 10 ^-9
(Twelfth surface)
K = -82.0325,
B = 1.10858 × 10 ^-4 ,
C = 4.12240 × 10 ⁻⁶ , D = -1.64200 × 10 ⁻⁷ ,
E = 4.14587 × 10 ^-9
(16th surface)
K = -1.0946,
B = 7.80404 × 10 ^-4 ,
C = -1.21984 × 10 ⁻⁷ , D = 2.30139 × 10 ⁻⁶ ,
E = -5.03880 × 10 ^-8
(Seventeenth surface)
K = 1.5606,
B = 1.02397 × 10 ^-3 ,
C = 1.90200 × 10 ⁻⁵ , D = 4.25470 × 10 ⁻⁷ ,
E = 1.04492 × 10 ^-7

(Scaled data)
Wide angle end Intermediate range Telephoto end
D (3) 1.700 8.256 11.413
D (9) 12.106 5.550 2.393
D (10) 5.050 3.470 1.030
D (17) 1.000 2.580 5.020
BF 4.19 4.19 4.19

(Numerical values related to conditional expression (1))
F2 / F3 = -0.8205

(Numerical value related to conditional expression (2))
F2 / F1 = -0.06

(Numerical value for conditional expression (3))
| Α1 | = 57.2

(Numerical values related to conditional expression (4))
SA1 = 0.283
SA1 / F2 = -0.038

(Numerical values for conditional expression (5))
F21 (focal length of the first lens L ₂₂₁ ) = − 10.12.
DDX12 (secondary derivative of the aspheric curve of the object side effective diameter of the first lens L ₂₂₁ ) = − 0.0436
F21 × DDX12 = 0.44

(Numerical value for conditional expression (6))
DDX11 (secondary derivative of the aspheric curve at the object side center of the first lens L ₂₂₁ ) = 0.1130
F21 × DDX11 = 1.14

(Numerical values related to conditional expression (7))
DDX21 (secondary derivative of the aspherical curve at the center of the imaging surface IMG side surface of the first lens L ₂₂₁ ) = 0.243
F21 × DDX21 = -2.46

(Numerical value related to conditional expression (8))
DDX22 (secondary derivative of the aspherical curve of the effective diameter of the imaging surface IMG side surface of the first lens L ₂₂₁ ) = 0.209
F21 × DDX22 = -2.12

(Numerical values related to conditional expression (9))
nd1 (refractive index of the first lens L ₂₁₁ with respect to the d line) = 1.94594

(Numerical values related to conditional expression (10))
nd2 (refractive index of the second lens L ₂₁₂ with respect to the d line) = 1.90979

(Numerical value related to conditional expression (11))
νd1 (Abbe number of the first lens L ₂₁₁ with respect to the d line) = 17.98
νd2 (Abbe number of the second lens L ₂₁₂ with respect to the d line) = 35.31
νd2−νd1 = 17.33

(Numerical values for conditional expression (12))
F33R2 (curvature of the image side surface of the third lens L ₂₃₃₎ = 6.5239
F34R1 (curvature of the object side surface of the fourth lens L ₂₃₄₎ = 7.5
FF 34 (focal length of the fourth lens L ₂₃₄₎ = 7.494
D3 (distance between the third lens _L233 and the fourth lens _L234 ) = 0.2
(F33R2 / F34R1) × (F34 / D3) = 32.59

  FIG. 6 is a diagram illustrating various aberrations at the wide-angle end of the zoom lens according to the second example. FIG. 7 is a diagram illustrating various aberrations in the intermediate range of the zoom lens according to the second example. FIG. 8 is a diagram illustrating all aberrations at the telephoto end of the zoom lens according to the second example. In the figure, g represents g-line (λ = 435.84 nm), d represents d-line (λ = 587.56 nm), and C represents aberration at a wavelength corresponding to C-line (λ = 656.28 nm). S and M in the astigmatism diagram represent aberrations with respect to the sagittal image surface and the meridional image surface, respectively.

FIG. 9 is a cross-sectional view along the optical axis showing the configuration of the zoom lens according to the third example. This zoom lens includes, in order from the object side (not shown), a first lens group G ₃₁ having a positive refractive power, a second lens group G ₃₂ having a negative refractive power, and an aperture stop STP that defines a predetermined aperture. The third lens group G ₃₃ having positive refractive power and the fourth lens group G ₃₄ having positive refractive power are arranged. Between the fourth lens group G ₃₄ and the image plane IMG, a cover glass CG is disposed. The cover glass CG is arranged as necessary, and can be omitted if unnecessary. Note that a light receiving surface of an image sensor such as a CCD or a CMOS is disposed on the imaging plane IMG.

The first lens group G ₃₁ includes a first lens L ₃₁₁ having a negative refractive power and a second lens L ₃₁₂ having a positive refractive power arranged in order from the object side. The first lens L ₃₁₁ and the second lens L ₃₁₂ are cemented.

The second lens group G ₃₂ includes, in order from the object side, a first lens L ₃₂₁ having a negative refractive power, a second lens L ₃₂₂ having a negative refractive power, a third lens L ₃₂₃ having a positive refractive power Are arranged. Aspherical surfaces are formed on both surfaces of the first lens L ₃₂₁ , respectively.

The third lens group G ₃₃ includes, in order from the object side, a first lens L ₃₃₁ having a positive refractive power, a second lens L ₃₃₂ having a positive refractive power, and a third lens L ₃₃₃ having a negative refractive power. And a fourth lens L ₃₃₄ having a positive refractive power. The second lens L ₃₃₂ and the third lens L ₃₃₃ are cemented. In addition, aspheric surfaces are formed on both surfaces of the fourth lens _L334 .

The fourth lens group G ₃₄ includes a positive lens L ₃₄₁ and a negative lens L ₃₄₂ arranged in this order from the object side.

In this zoom lens, zooming from the wide-angle end to the telephoto end is performed by bringing the second lens group G ₃₂ and the third lens group G ₃₃ close to the aperture stop STP. The first lens group G ₃₁ and the aperture stop STP are always fixed.

  Various numerical data relating to the zoom lens according to Example 3 will be described below.

Focal length of the entire zoom lens = 2.8 (wide angle end) to 4.8 (middle range) to 7.6 (telephoto end)
F number = 1.9 (wide-angle end) to 2.3 (middle range) to 3.2 (telephoto end)
Half angle of view (ω) = 48.9 (wide-angle end) to 31.2 (middle range) to 21.2 (telephoto end)
Focal length (F1) of the first lens group G ₃₁ = 94.08
Focal length of the second lens group G ₃₂ (F2) = - 7.18
Focal length of the third lens group G ₃₃ (F3) = 10.65
Focal length of the fourth lens group G ₃₄ (F4) = 22.15

(Lens data)
r ₁ = 71.3463
d ₁ = 1.000 nd ₁ = 1.94594 νd ₁ = 17.98
r ₂ = 42.4436
d ₂ = 3.513 nd ₂ = 1.91082 νd ₂ = 35.25
r ₃ = 489.0559
d ₃ = D (3) (variable)
r ₄ = 27.5087 (aspherical surface)
d ₄ = 1.100 nd ₃ = 1.85135 νd ₃ = 40.10
r ₅ = 4.6612 (aspherical surface)
d ₅ = 3.825
r ₆ = -17.4893
d ₆ = 0.600 nd ₄ = 1.72916 νd ₄ = 54.67
r ₇ = 9.3223
d ₇ = 0.855
r ₈ = 12.2968
d ₈ = 2.793 nd ₅ = 1.90366 νd ₅ = 31.31
r ₉ = -33.2082
d ₉ = D (9) (variable)
r ₁₀ = ∞ (aperture)
d ₁₀ = D (10) (variable)
r ₁₁ = 9.8178
d ₁₁ = 2.203 nd ₆ = 1.69680 νd ₆ = 55.46
r ₁₂ = 107.4856
d ₁₂ = 0.700
r ₁₃ = 7.4823
d ₁₃ = 4,500 nd ₇ = 1.49700 νd ₇ = 81.61
r ₁₄ = -14.3008
d ₁₄ = 0.500 nd ₈ = 1.90366 νd ₈ = 31.31
r ₁₅ = 6.4400
d ₁₅ = 0.181
r ₁₆ = 6.2000 (aspherical surface)
d ₁₆ = 4.400 nd ₉ = 1.59201 νd ₉ = 67.02
r ₁₇ = -17.8881 (aspherical surface)
d ₁₇ = D (17) (variable)
r ₁₈ = 15.0822
d ₁₈ = 1.758 nd ₁₀ = 1.48749 νd ₁₀ = 70.24
r ₁₉ = -20.2082
d ₁₉ = 0.359
r ₂₀ = -13.2684
d ₂₀ = 0.622 nd ₁₁ = 1.92476 νd ₁₁ = 25.36
r ₂₁ = -15.8173
d ₂₁ = 0.500
r ₂₂ = ∞
d ₂₂ = 1.010 nd ₁₂ = 1.51633 νd ₁₂ = 64.14
r ₂₃ = ∞
d ₂₃ = BF (back focus)
r ₂₄ = ∞ (imaging plane)

Cone coefficient (K) and aspheric coefficient (B, C, D, E)
(Fourth surface)
K = -0.4863,
B = -1.72756 × 10 ^-4 ,
C = 2.20173 × 10 ^-6 , D = -2.55776 × 10 ^-8 ,
E = 1.24714 × 10 ^-10
(5th page)
K = 0.1419,
B = 1.01770 × 10 ^-4 ,
C = -3.55861 × 10 ⁻⁶ , D = 3.09840 × 10 ⁻⁷ ,
E = -1.05047 × 10 ^-8
(16th surface)
K = -1.9975,
B = 8.71980 × 10 ⁻⁴ ,
C = -3.67856 × 10 ⁻⁵ , D = 1.75884 × 10 ⁻⁶ ,
E = -3.66758 × 10 ^-8
(Seventeenth surface)
K = 4.7534,
B = 8.53333 × 10 ^-4 ,
C = -7.14546 × 10 ⁻⁶ , D = 8.21248 × 10 ⁻⁷ ,
E = 3.47975 × 10 ^-10

(Scaled data)
Wide angle end Intermediate range Telephoto end
D (3) 1.800 8.652 10.657
D (9) 11.730 4.878 2.873
D (10) 7.252 4.715 0.958
D (17) 1.300 3.837 7.594
BF 1.50 1.50 1.50

(Numerical values related to conditional expression (1))
F2 / F3 = -0.674

(Numerical value related to conditional expression (2))
F2 / F1 = -0.076

(Numerical values related to conditional expression (3))
| Α1 | = 57.4

(Numerical values for conditional expression (4))
SA1 = 0.323
SA1 / F2 = -0.045

(Numerical values for conditional expression (5))
F21 (a focal length of the first lens L ₃₂₁₎ = - 6.74
DDX12 (secondary derivative of the aspherical curve of the object side effective diameter of the first lens L ₃₂₁ ) =-0.300
F21 × DDX12 = 2.02

(Numerical values related to conditional expression (6))
DDX11 (secondary derivative of the aspheric curve at the center of the object side surface of the first lens L ₃₂₁ ) = 0.0364
F21 × DDX11 = −0.25

(Numerical values related to conditional expression (7))
DDX21 (second derivative of the aspheric curve of the image plane IMG side center of the first lens L ₃₂₁₎ = 0.243
F21 × DDX21 = -1.63

(Numerical value related to conditional expression (8))
DDX22 (second derivative of the aspheric curve of the image plane IMG side effective diameter of the first lens L ₃₂₁₎ = 0.209
F21 × DDX22 = -1.41

(Numerical values related to conditional expression (9))
nd1 (refractive index of the first lens L ₃₁₁ with respect to the d line) = 1.94594

(Numerical values related to conditional expression (10))
nd2 (refractive index of the second lens L ₃₁₂ with respect to the d line) = 1.91082

(Numerical value related to conditional expression (11))
νd1 (Abbe number of the first lens L ₃₁₁ with respect to the d-line) = 17.98
νd2 (Abbe number of the second lens L ₃₁₂ with respect to the d-line) = 35.25
νd2−νd1 = 17.27

(Numerical values for conditional expression (12))
F33R2 (curvature of the image side surface of the third lens L ₃₃₃₎ = 6.44
F34R1 (curvature of the object side surface of the fourth lens L ₃₃₄₎ = 6.2
FF 34 (focal length of the fourth lens L ₃₃₄₎ = 8.344
D3 (distance between the third lens L ₃₃₃ and the fourth lens L ₃₃₄ ) = 0.1808
(F33R2 / F34R1) × (F34 / D3) = 47.94

(Numerical value for conditional expression (13))
F41 (focal length of positive lens L ₃₄₁ ) = 18.01
F4 / F41 = 1.23

(Numerical value for conditional expression (14))
νd (Abbe number with respect to the d-line of the positive lens L ₃₄₁ ) = 70.24

  FIG. 10 is a diagram illustrating various aberrations at the wide-angle end of the zoom lens according to the third example. FIG. 11 is a diagram illustrating various aberrations in the intermediate range of the zoom lens according to the third example. FIG. 12 is a diagram illustrating all aberrations at the telephoto end of the zoom lens according to the third example. In the figure, g represents g-line (λ = 435.84 nm), d represents d-line (λ = 587.56 nm), and C represents aberration at a wavelength corresponding to C-line (λ = 656.28 nm). S and M in the astigmatism diagram represent aberrations with respect to the sagittal image surface and the meridional image surface, respectively.

In the numerical data in each of the above embodiments, r ₁ , r ₂ ,... Are the curvature radii of the respective lenses and diaphragm surfaces, and d ₁ , d ₂ ,. Thickness or spacing between them, nd ₁ , nd ₂ ,... Is the refractive index with respect to d-line (λ = 587.56 nm) of each lens, νd ₁ , νd ₂ ,. The Abbe number with respect to the d-line (λ = 587.56 nm) is shown. The unit of length is all “mm”, and the unit of angle is “°”.

  Each of the aspheric shapes is expressed by the following equation when the distance from the apex of the lens surface in the optical axis direction is x, the height in the direction perpendicular to the optical axis is y, and the light traveling direction is positive. Is done.

  Here, R is a paraxial radius of curvature, K is a conical coefficient, and B, C, D, and E are fourth-order, sixth-order, eighth-order, and tenth-order aspherical coefficients, respectively.

  As described above, the zoom lens according to each of the above-described embodiments is configured by using a lens having an aspheric surface as appropriate, and satisfies the above-described conditional expressions, so that it can be reduced in size and weight. High imaging performance can be maintained even when zooming is performed while maintaining a wide angle of view. In particular, it is excellent in suppressing the occurrence of distortion over the entire zooming range from the wide-angle end to the telephoto end. For this reason, an optical system capable of obtaining a bright and clear image can be realized.

  As described above, the zoom lens according to the present invention is useful for a digital camera, a video camera, and the like, and is particularly suitable for a camera used in a TV conference system.

G ₁₁ , G ₂₁ , G ₃₁ 1st lens group G ₁₂ , G ₂₂ , G ₃₂ 2nd lens group G ₁₃ , G ₂₃ , G ₃₃ 3rd lens group G ₁₄ , G ₃₄ 4th lens group L ₁₁₁ , L ₁₂₁ , L ₁₃₁ , L ₂₁₁ , L ₂₂₁ , L ₂₃₁ , L ₃₁₁ , L ₃₂₁ , L ₃₃₁ First lens L ₁₁₂ , L ₁₂₂ , L ₁₃₂ , L ₂₁₂ , L ₂₂₂ , L ₂₃₂ , L ₃₁₂ , L ₃₂₂ , L ₃₃₂ Second lens L ₁₂₃ , L ₁₃₃ , L ₂₂₃ , L ₂₃₃ , L ₃₂₃ , L ₃₃₃ Third lens L ₁₃₄ , L ₂₃₄ , L ₃₃₄ Fourth lens L ₁₄₁ , L ₃₄₁ Positive lens L ₃₄₂ Negative lens STP Aperture stop IMG Image plane CG Cover glass

Claims (7)

A first lens group having a positive refractive power, a second lens group having a negative refractive power, an aperture stop, and a third lens group having a positive refractive power, which are arranged in order from the object side. ,
The second lens group is arranged in order from the object side, and includes a first lens having an aspheric surface on the object side and having a negative refractive power, a second lens having a negative refractive power, and a positive refractive power. A third lens having
Zooming from the wide-angle end to the telephoto end by bringing the second lens group and the third lens group close to the aperture stop,
A zoom lens satisfying the following conditional expression:
(1) -1.1 <F2 / F3 <-0.5
(2) -0.3 <F2 / F1 <0
(3) | α1 |> 55
Where F1 is the focal length of the first lens group, F2 is the focal length of the second lens group, F3 is the focal length of the third lens group, and α1 is the principal ray on the final lens surface of the first lens group. Indicates the emission angle. 2. The zoom lens according to claim 1, wherein an aspheric surface is formed on the object side of the first lens constituting the second lens group, and the following conditional expression is satisfied.
(4) SA1 / F2 <−0.015
However, F2 is the focal length of the second lens group, and SA1 is a spherical shape corresponding to 90% of one side of the aspherical part of the lens on the first lens object side constituting the second lens group. The sag amount in the spherical shape (the direction is a positive direction of light travel). 3. The zoom lens according to claim 1, wherein the first lens constituting the second lens group has an aspheric surface on the object side, and satisfies the following conditional expression.
(5) -2.0 <F21 × DDX12 <4.0
However, F21 shows the focal length of the 1st lens which comprises the said 2nd lens group, DDX12 shows the secondary differential amount of the aspherical curve of the object side effective diameter of the 1st lens which comprises the said 2nd lens group. The first lens constituting the second lens group has an aspheric surface on the image side, and satisfies the following conditional expression: Zoom lens.
(6) -1.5 <F21 × DDX11 <0.5
(7) −5.0 <F21 × DDX21 <−0.5
(8) −4.0 <F21 × DDX22 <0
However, DDX11 is the second derivative of the aspherical curve at the object side center of the first lens constituting the second lens group, and DDX21 is the aspherical curve at the image side center of the first lens constituting the second lens group. , DDX22 represents the second derivative of the aspherical curve of the image side effective diameter of the first lens constituting the second lens. The first lens group includes a cemented lens including a first lens having a negative refractive power and a second lens having a positive refractive power,
The zoom lens according to claim 1, wherein the following conditional expression is satisfied.
(9) nd1> 1.9
(10) nd2> 1.77
(11) νd2−νd1> 17
However, nd1 is the refractive index of the first lens constituting the first lens group with respect to the d-line, nd2 is the refractive index of the second lens constituting the first lens group with respect to the d-line, and νd1 is the first lens group. Abbe number with respect to d-line of the first lens constituting the lens, and νd2 indicate Abbe number with respect to d-line of the second lens constituting the first lens group. The third lens group includes a first lens having a positive refractive power, a second lens having a positive refractive power, and a third lens having a negative refractive power, which are arranged in order from the object side. And a fourth lens having positive refractive power formed with an aspheric surface,
The zoom lens according to claim 1, wherein the following conditional expression is satisfied.
(12) 25 <(F33R2 / F34R1) × (FF34 / D3) <60
However, F33R2 is the curvature of the image side surface of the third lens that constitutes the third lens group, F34R1 is the curvature of the object side surface of the fourth lens that constitutes the third lens group, and FF34 is the third lens group. The focal length of the fourth lens, D3, indicates the distance between the third lens and the fourth lens constituting the third lens group. A fourth lens group configured to include a positive lens on the image side of the third lens group;
The zoom lens according to claim 1, wherein the following conditional expression is satisfied.
(13) 0.8 <F4 / F41 <1.4
(14) νd> 60
Where F4 is the focal length of the fourth lens group, F41 is the focal length of the positive lens included in the fourth lens group, and νd is the Abbe number of the positive lens included in the fourth lens group with respect to the d-line.

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