JPH0735977A - Zoom lens - Google Patents

Abstract

PURPOSE:To obtain a zoom lens of miniaturization and light in weight and with high specification and high performance by employing four lens group constitution and providing lens surfaces of aspherical shape to satisfy specific conditions at a first lens group and a second lens group, respectively. CONSTITUTION:This lens is provided with the first to fourth lens groups G1-G4 with positive, negative, negative, and positive refracting powers sequentially from an object side. When variable magnification is performed, the second and third lens groups G2, G3 are moved on an optical axis. An i-th lens group Gi (i=1 and 2) is provided with at least one lens surface of aspherical shape to satisfy condition 10<-31xai(hi)-xi(hi)1<10<-1>. Where, the maximum effective radius of the lens surface of aspherical shape is assumed as hi, and a value of (x) in the maximum effective radius hi by assuming the surface apex of the lens surface of aspherical shape as an origin and an x-axis as the optical axis and expressing a y-axis in a coordinate system setting as a straight line passing the origin and intersecting orthogonally to the x-axis as xai(hi). The value of (x) of the paraxial radius of curvature of the lens surface of aspherical shape in the maximum effective radius hi also is assumed as xi(hi).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is small and lightweight, has a large diameter,
The present invention relates to a zoom lens having a large zoom ratio, and particularly to a zoom lens suitable for a television camera.

[0002]

2. Description of the Related Art Conventionally, a zoom lens having a large aperture and a large zoom ratio has a four-group structure having positive, negative, negative, positive or positive, negative, positive, positive refracting power in order from the object side. It has been known. In these zoom lenses, zooming is performed by moving the second lens group and the third lens group.

[0003]

In recent years, there has been an increasing demand for a compact, lightweight and high-performance zoom lens having a large aperture, a wide angle of view, and a large zoom ratio. In general, a zoom lens is designed to increase the power of each lens group as a means for achieving higher specifications while maintaining a further reduction in size and weight, or maintaining a reduction in size and weight. However, various aberrations are sacrificed for that purpose. However, there is a problem that performance problems occur.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a compact, lightweight, high-performance zoom lens having high performance.

[0005]

[Means for Solving the Problems]
Therefore, the zoom lens according to the present invention has the following configuration.
It For example, as shown in FIG. 1, the positive refracting power is increased in order from the object side.
First lens group G having ₁And a second lens with negative refractive power
Group G₂And the third lens group G having negative refractive power₃And positive refraction
Fourth lens group G with power_FourFor zoom lenses with
The second lens group during zooming from the wide-angle end to the telephoto end.
G₂Moves from the object side to the image side along the optical axis, and
Lens group G₃So that it moves back and forth on the optical axis
Composed. Then, the first lens group G₁From the optical axis
Aspherical surface with negative refractive power gradually increasing toward the periphery
Shape or an aspherical shape such that the positive refractive power gradually weakens.
The second lens is configured to have at least one lens surface.
Group G₂Is gradually refracted from the optical axis toward the periphery
Aspherical shape such that the power becomes stronger or gradually the negative refracting power becomes weak
Have at least one aspherical lens surface
And satisfy the following conditions.

[0006]

[Equation 1] 10 ⁻³ <| xa ₁ (h ₁ ) −x ₁ (h ₁ ) | / h ₁ <10 ⁻¹ (1)

[0007]

[Equation 2] 10 ⁻³ <| xa ₂ (h ₂ ) −x ₂ (h ₂ ) | / h ₂ <10 ⁻¹ (2) where, h ₁ : aspherical shape in the first lens group G _1. maximum effective radius of the lens surface, h _2: lens surface maximum effective radius of the aspherical shape of the second lens group G _{2, xa 1 (h 1)} : a first aspheric surface vertex of the lens group G ₁ In the coordinate system where the x-axis is the optical axis and the y-axis is a straight line that passes through the origin and is orthogonal to the x-axis at the origin, the value of x at the maximum effective radius h ₁ , xa ₂ (h ₂ ): 2nd When the apex of the aspherical surface of the lens group G ₂ is the origin, the x axis is the optical axis, and the y axis is a straight line that passes through the origin and is orthogonal to the x axis, the x of the maximum effective radius h ₂ values, x ₁ (h _1): Table first taking an aspherical surface vertex of the lens group G ₁ to the origin, taken optical axis in the x-axis, the coordinate system of the straight line perpendicular to the street x axis at the origin in the y-axis When in, the paraxial curvature radius of the lens surface of aspherical shape in the maximum effective radius h ₁ x
X ₂ (h ₂ ): A coordinate system in which the apex of the aspherical surface of the second lens group G ₂ is the origin, the x axis is the optical axis, and the y axis is a straight line passing through the origin and orthogonal to the x axis. When expressed, x of the paraxial radius of curvature of the aspherical lens surface at the maximum effective radius h ₂
The value of the,

[0008]

In the present invention, first, since the first lens group G ₁ has a positive refracting power and the second lens group G ₂ has a negative refracting power, the aberration correction in each lens group will be considered. And the first
At least one aspherical surface in the lens group G ₁ has a shape in which the negative refracting power becomes stronger from the optical axis toward the periphery or the positive refracting power becomes weaker than the paraxial radius of curvature of this aspherical surface. The aspheric surface of at least one surface of the second lens group G ₂ has a shape in which the positive refractive power becomes stronger from the optical axis toward the periphery, as compared with the paraxial radius of curvature of this aspheric surface, or It is desirable that the negative refractive power should be weakened.

Further, in order to satisfactorily correct various aberrations and to easily manufacture an aspherical lens, in the present invention, the optimum range of the amount of aspherical surface is set according to the above conditions (1) and (2). Stipulates. Here, if the upper limit of the condition (1) is exceeded, the amount of aspherical surface will significantly increase, making it very difficult to manufacture an aspherical lens. On the other hand, when the value goes below the lower limit, spherical aberration on the telephoto side is undercorrected, which is not preferable.

If the upper limit of the condition (2) is exceeded, the pin-cushion distortion aberration increases from the intermediate focal length state to the telephoto side, which is not preferable. When the value goes below the lower limit of the condition (2), fluctuations in various aberrations due to zooming, particularly fluctuations in field curvature become remarkable, and spherical aberration on the telephoto side is overcorrected, which is not preferable. Further, in the present invention, the first lens group G ₁ includes, in order from the object side, the negative lens group L ₁₁ and at least three positive lens groups L because of the high specifications and high performance required for the zoom lens for the television camera.
Desirably, the second lens group G ₂ is configured to include ₁₂ , L ₁₃ , and L ₁₄ , and the second lens group G ₂ is configured to include at least three lens groups L ₂₁ , L ₂₂ , and L ₂₃ .

[0011] Particularly, in order to reduce the size and weight reduction, it is important to reduce the number of lenses of the first lens group G _1, the first
Using an aspherical surface in the lens group G _1, if the first lens group G ₁ to 3 groups following structure, like a significant effect on weight reduction. However, the aspherical shape in that case is considerably deviated from the paraxial radius of curvature of this aspherical surface, and
It is not preferable because it becomes complicated including undulations, its manufacture becomes difficult, and tolerances such as eccentricity become strict.

Further, in the present invention, when it is attempted to correct the pincushion type distortion aberration by the negative lens unit L ₁₁ , the spherical aberration on the telephoto side tends to be largely under. Therefore, it is desirable to provide at least one aspherical surface on either the negative lens group L ₁₁ or the positive lens group L ₁₂ in the first lens group G ₁ . With the aspherical surface of the negative lens unit L ₁₁ itself or the positive lens unit L _{12 in} the vicinity thereof, it becomes possible to excellently correct spherical aberration on the telephoto side.

Further, in the present invention, the first lens group G
It is desirable that the negative lens unit L _{11 in 1} be configured so as to satisfy the following conditional expression.

[0014]

[Equation 3] −1.0 <(R ₂ + R ₁ ) / (R ₂ −R ₁ ) <− 0.1 (3) where R _{1 is} the most object side lens surface of the negative lens group L ₁₁ . Paraxial radius of curvature, R ₂ : Paraxial radius of curvature of the lens surface of the negative lens group L ₁₁ closest to the image.

When the negative lens unit L ₁₁ exceeds the upper limit of the condition (3), spherical aberration on the telephoto side is undercorrected (under).
Is not preferable. Here, in order to correct this spherical aberration, it is necessary to increase the amount of aspherical surface, which makes manufacturing difficult. If the negative lens unit L ₁₁ exceeds the lower limit of the condition (3), pincushion distortion aberration increases, which is not preferable.

It is desirable that the zoom lens according to the present invention is constructed so as to satisfy the following conditions in addition to the above construction.

[0017]

[Formula 4] 0.6 <F _T ^1/2・ f ₁ / f _T <0.9 (4) where f _T : composite focal length of the entire system at the telephoto end, F _T : F number at the telephoto end, f ₁ : focal length of the first lens group G ₁ , Is.

The condition (4) defines the optimum power of the zooming portion in order to reduce the size of the zooming portion of the zoom lens while maintaining the imaging performance. With this, it is possible to define the optimum power range of the zooming unit according to the zoom ratio and the maximum aperture ratio of the zoom lens. When the value exceeds the upper limit of the condition (4), it is difficult to reduce the size of the variable power portion, which is not preferable. On the other hand, when the value goes below the lower limit, it is effective for downsizing, but aggravation of various aberrations accompanying this is remarkable. In particular, the Petzval sum is deteriorated due to the stronger powers of the second lens group G ₂ and the third lens group G ₃ , and the apparent F number of the first lens group G _{1 on} the telephoto side becomes too small. It is not preferable because spherical aberration becomes difficult to correct. Further, manufacturing tolerances become strict, and the image quality is significantly deteriorated due to decentering of each lens.

The zoom lens according to the present invention preferably satisfies the following conditions in addition to the above-mentioned constitution.

[0020]

[Equation 5] 0.9 <| β _2W · V ^1/2 | <1.3 (5) where β _2W is the magnification at the wide-angle end of the second lens group G ₂ , and V is the zoom ratio.

This condition (5) is a condition for maintaining good Petzval sum. As a result, even though the zooming unit is downsized under the condition (4),
Since the power of the lens group G ₂ can be reduced,
It can prevent the deterioration of Petzval sum. As in the present invention
In a negative / negative / positive type zoom lens, the power of the second lens group G ₂ tends to be the strongest in each lens group, so the negative power of the second lens group G ₂ should be made as weak as possible. Is most effective for keeping the Petzval sum to a proper value.

A detailed description will be given below with reference to FIG. FIG.
Is the second lens group G₂Schematically shows how the magnification is changed by
It is a figure. In FIG. 13, P is the first lens group G₁By
Image point position, that is, the second lens group G₂Object position with respect to
Q is the second lens group G₂The locus of the image points formed by
Show. Here, the second lens group G₂Let v be the scaling factor
Then, the second lens group G₂Double at the wide-angle end and the telephoto end
The rate is -1 / v^1/2, -V^1/2Such an example
Surround W₀-T₀If is selected as the reference variable area, the position of the image point Q
Is the same at the wide-angle end and the telephoto end, and the third lens group G₃Position of
Also matches on both ends. At this time, the second lens group G ₂Scaling of
The rate v becomes equal to the zoom ratio V.

At the wide-angle end where the first lens group G ₁ and the second lens group G ₂ are closest to each other, when the space required to prevent mechanical interference between the lens groups is Δ, the second lens group at the wide-angle end is Magnification β _2W of lens group G ₂ and its focal length f ₂
Between

[0024]

## EQU6 ## There is a relationship of f ₂ = (f ₁ −Δ) · β _2W / (1−β _2W ) (6). From this equation, if β _2W is made larger than −1 / V ^1/2 , | f ₂ | becomes large, and the second lens group G ₂
It is clear that the power of is weakened. This is
3, the zooming range of the second lens group G ₂ is set to the reference zooming range W _0.
This corresponds to selecting a region WT below -T ₀ . In the present invention, if the variable power range of the second lens group G ₂ is set within the range of the conditional expression (5), the negative power of the second lens group G ₂ can be weakened.

Here, if the lower limit of conditional expression (5) is exceeded, the power of the second lens group G ₂ becomes strong, and the Petzval sum is unavoidably deteriorated, which is not preferable. On the other hand, if the upper limit is exceeded, the movable space required for zooming the second lens group G ₂ becomes large, which leads to an increase in the total length of the lens system and the diameter of the front lens. The ratio of the amount of movement of the third lens group G ₃ to the amount of movement of the second lens group G ₂ becomes extremely large, which is not preferable because the mechanism of the lens barrel for moving both groups is inconvenient.

Further, in the present invention, in order to satisfactorily correct various aberrations and maintain high performance in spite of the large aperture ratio,
It is desirable that the third lens group G ₃ and the fourth lens group G ₄ have the following configurations. First, the third lens group G ₃
It is desirable that the negative lens L ₃ is composed of a biconcave negative lens and a biconvex positive lens cemented together. Next, the fourth lens group G ₄ includes, in order from the object side, a positive meniscus lens L ₄₁ having a convex surface directed toward the image side, a biconvex positive lens L ₄₂ , a biconvex positive lens L _43, and this biconvex positive lens L _43. A front lens group having a negative lens L ₄₄ cemented to the object side and having a surface having a stronger curvature toward the object side, a biconvex positive lens L ₄₅ , two cemented lenses L ₄₆ and L _47, and a surface having a stronger curvature toward the object side. It is desirable that the rear lens group has a positive lens L ₄₈ directed to

[0027]

Embodiments of the present invention will be described below with reference to the drawings. [First Embodiment] FIG. 1 is a lens configuration diagram of a first embodiment according to the present invention. In FIG. 1, the zoom lens according to Example 1 includes, in order from the object side, a first lens group G ₁ having a positive refractive power.
A second lens group G ₂ having a negative refractive power, a third lens group G ₃ having a negative refractive power, and a fourth lens group G ₄ having a positive refractive power. Further, in FIG. 1, a parallel plane plate such as a color separation prism and various filters arranged between the image surface of the zoom lens closest to the image and the image surface is shown as a prism block PB.

In the zoom lens of this embodiment, at the time of zooming from the wide-angle end to the telephoto end, the first lens group G ₁ and the fourth lens group G ₄ are fixed in the optical axis direction, and the second lens group G ₂ is monotonically extended to the object side along the optical axis,
The third lens group G ₃ is configured to move so as to reciprocate on the optical axis. In this embodiment, the first lens group G
Reference numeral ₁ denotes, in order from the object side, a biconcave negative lens L ₁₁ , a biconvex positive lens L ₁₂ , a biconvex positive lens L ₁₃ having a stronger curvature toward the object side, and a convex surface on the object side. And a meniscus-shaped positive lens L ₁₄ directed to. Here, the image side lens surface of the negative lens L ₁₁ is formed in an aspherical shape.

The second lens group G ₂ includes, in order from the object side, a negative meniscus lens L ₂₁ having a convex surface facing the object side,
It includes a biconcave negative lens L ₂₂ , a biconvex positive lens, a biconcave negative lens, and a cemented lens L _{23 including} a meniscus positive lens having a convex surface facing the object side. Here, the lens surface of the negative lens L _{22 on} the object side is formed in an aspherical shape.

The third lens group G ₃ has a cemented lens L ₃ which is composed of, in order from the object side, a biconcave negative lens and a biconvex positive lens having a stronger curvature toward the object side. The fourth lens group G ₄ includes a meniscus positive lens L ₄₁ having a concave surface facing the object side, a biconvex positive lens L ₄₂ having a stronger curvature facing the object side, and a biconvex positive lens. L
₄₃ and a meniscus negative lens L with a concave surface facing the object side
_A cemented lens consisting of ₄₄ and a positive biconvex lens L
₄₅ , a cemented lens L _{46 including a} biconcave negative lens and a biconvex positive lens, and a cemented lens L _{46 including} a biconvex positive lens and a meniscus negative lens having a concave surface facing the object side. ₄₇ and a positive meniscus lens L ₄₈ having a convex surface facing the object side.

The specifications according to this embodiment are shown in Table 1 below.
In the specification table of the embodiment, f indicates the focal length and F indicates the F number. The number at the left end represents the order from the object side of the lens surface, r is the radius of curvature of the lens surface, d is the distance between the lens surfaces, and n and ν are the refractive index and the Abbe number d line (λ =
587.6 nm). In this embodiment, aberration correction is performed by including the prism block PB showing a plane parallel plate such as a color separation prism and various filters, and therefore these data are also shown.

Further, the aspherical shape is such that r is an aspherical surface in a coordinate system in which the apex of the aspherical surface is the origin, the optical axis is the X axis, and a straight line passing through the origin and orthogonal to the X axis is the Y axis. When paraxial radius of curvature, k are conic constants, and A, B, C, and D are aspherical coefficients, respectively,

[0033]

[Expression 7] X = y ² · r ⁻¹ · {1+ [1- (1 + k) (y / r) ² ] ^1/2 } ⁻¹ + Ay ⁴ + By ⁶ + Cy ⁸ + Dy ¹⁰ (7) .

[0034]

[Table 1] f = 8.75 to 127 F = 1.72 to 2.13 (Variable spacing during zooming) f 8.75 40 127 d 8 0.8543 34.4666 45.6605 d16 47.8103 9.2889 3.7487 d19 5.0260 9.9351 4.2814 (aspherical coefficient) 2nd surface k = 0.0000 A = 1.6949 × 10 ^-7 B = -7.4565 × 10 ^-12 C = 8.9183 × 10 ^-15 D = 0.0000 ｜ xa ₁ (h ₁ ) −x ₁ (h ₁ ) ｜ ＝ 0.265mm (h ₁ = 35.15mm) 11th surface k = 0.0000 A = 8.0949 × 10 ^-6 B = -4.4929 × 10 ^-8 C = 4.6469 × 10 ^-10 D = 0.0000 ｜ xa ₂ (h ₂ ) −x ₂ (h ₂ ) ｜ ＝ 0.055 mm (h ₂ = 9.2 mm) (Values corresponding to conditions) (1) 7.539 × 10 ^-3 (2) 5.978 × 10 ^-3 (3) -0.456 (4) 0.765 (5) 1.034 Figures 2 (a), (b), and (c) show the wide-angle end of the first embodiment, respectively. Various aberration diagrams, various aberration diagrams at the intermediate focal length state, and various aberration diagrams at the telephoto end are shown. In each aberration diagram, F is the F number,
y is the image height, d is the d line (λ = 587.6 nm), and SC is the sine condition. In the diagram of astigmatism, the broken line M indicates the meridional image plane and the solid line S indicates the sagittal image plane.

From the comparison of each aberration diagram, it is apparent that this embodiment has excellent imaging performance in which various aberrations are satisfactorily corrected from the wide-angle end to the telephoto end. [Second Embodiment] Next, a second embodiment according to the present embodiment will be described with reference to FIG. FIG. 3 is a lens configuration diagram of the second embodiment.

In the second embodiment, the first and second lens groups G₁,
G₂The configuration is different from that of the first embodiment of FIG. In this example
In order to simplify the description, the first and second lens groups G
₁, G ₂The configuration of will be described. In FIG.
Group G₁Is a biconcave negative lens L in order from the object side.
₁₁And a biconvex positive lens L₁₂And a stronger song on the object side
Biconvex positive lens L with directivity₁₃And a convex surface on the object side
Meniscus-shaped positive lens L₁₄Have and. here
Then, the biconvex positive lens L₁₂The lens surface on the object side of
An aspherical layer with an aspherical surface on the object side is provided.
Has been.

The second lens group G ₂ includes, in order from the object side, a meniscus negative lens L having a convex surface facing the object side.
₂₁ , a cemented lens L ₂₂ having a positive meniscus lens having a concave surface facing the object side and a biconcave negative lens, a biconvex positive lens, and a meniscus negative lens having a concave surface facing the object. And a cemented lens L _{23 including a} lens.
Here, on the image-side lens surface of the cemented lens L ₂₂ , there is provided an aspherical layer having an aspherical surface on the image side.

The specifications according to this embodiment are shown in Table 2 below.
In the specification table of the embodiment, f indicates the focal length and F indicates the F number. The number at the left end represents the order from the object side of the lens surface, r is the radius of curvature of the lens surface, d is the distance between the lens surfaces, and n and ν are the refractive index and the Abbe number d line (λ =
587.6 nm). In this embodiment, aberration correction is performed by including the prism block PB showing a plane parallel plate such as a color separation prism and various filters, and therefore these data are also shown.

Further, the aspherical shape is expressed by the above equation (7).

[0040]

[Table 2] f = 8.75 to 127 F = 1.72 to 2.13 (Variable spacing during zooming) f 8.75 40 127 d 9 0.7161 34.1772 45.2766 d18 46.5657 8.2694 2.8840 d21 5.1631 9.9982 4.2842 (aspherical coefficient) 3rd surface k = 0.0000 A = -2.6356 × 10 ^-7 B = 1.8109 × 10 ^-11 C = -1.7028 × 10 ^-14 D = 0.0000 ｜ xa ₁ (h ₁ ) −x ₁ (h ₁ ) ｜ ＝ 0.418mm (h ₁ = 35.35mm) 15th surface k = 0.0000 A = -2.6178 × 10 ^-5 B = 5.3831 × 10 ^-8 C = -9.2878 × 10 ^-10 D = 0.0000 ｜ xa ₂ (h ₂ ) −x ₂ (h ₂ ) ｜ ＝ 0.170mm (h ₂ = 8.85mm) (Condition-compatible numerical value) (1 ) 1.182 × 10 ^-2 (2) 1.921 × 10 ^-2 (3) -0.293 (4) 0.764 (5) 1.040 Figures 4 (a), (b), and (c) show the wide-angle end of the second embodiment, respectively. The various aberration diagrams at, the various aberration diagrams at the intermediate focal length state, and the various aberration diagrams at the telephoto end are shown. In each aberration diagram, F is the F number,
y is the image height, d is the d line (λ = 587.6 nm), and SC is the sine condition. In the diagram of astigmatism, the broken line M indicates the meridional image plane and the solid line S indicates the sagittal image plane.

From the comparison of each aberration diagram, it is apparent that this embodiment has excellent imaging performance in which various aberrations are satisfactorily corrected from the wide-angle end to the telephoto end. Next, the third and fourth embodiments of the present invention will be described with reference to FIGS. FIG. 5 is a lens configuration diagram of the third embodiment,
FIG. 7 is a lens configuration diagram of the fourth example. In the third and fourth examples shown in FIGS. 5 and 7, the configuration of the fourth lens group G ₄ is different from that of the second example shown in FIG. Here, in order to simplify the description, the configuration of the fourth lens group G ₄ will be described.

In FIGS. 5 and 7, the fourth lens group G_Four
Is a positive meniscus lens L having a concave surface facing the object side.
₄₁And a positive biconvex lens with a stronger curvature toward the object side.
Z L ₄₂And a biconvex positive lens L₄₃And facing the concave side to the object side
Negative meniscus lens L₄₄Joining Ren consisting of
And a biconvex positive lens L₄₅And a negative lens with a biconcave shape
And a cemented lens L composed of a biconvex positive lens₄₆And both
Meniscus type with convex positive lens and concave surface facing the object side
Lens L consisting of a negative lens₄₇And on the object side
Biconvex positive lens L with stronger curvature₄₈Have and
It

[Third Embodiment] Table 3 below shows specifications according to the third embodiment. In the specification table of the embodiment, f indicates the focal length and F indicates the F number. The number at the left end represents the order from the object side of the lens surface, r is the radius of curvature of the lens surface, d is the distance between the lens surfaces, n and ν are the refractive index and the d-line of the Abbe number (λ = 587.6 nm) Is the value for. In this embodiment, aberration correction is performed by including the prism block PB showing a plane parallel plate such as a color separation prism and various filters, and therefore these data are also shown.

Further, the aspherical shape is expressed by the above equation (7).

[0045]

[Table 3] f = 8.75 to 127 F = 1.72 to 2.24 (Variable spacing during zooming) f 8.75 40 127 d 9 0.7767 30.3742 39.8224 d18 40.1399 6.4650 4.5761 d21 7.2725 11.3500 3.7906 (aspherical coefficient) 3rd surface k = 0.0000 A = -3.9534 × 10 ^-7 B = 2.1461 × 10 ^-11 C = -1.7069 × 10 ^-14 D = 0.0000 ｜ xa ₁ (h ₁ ) −x ₁ (h ₁ ) ｜ ＝ 0.606mm (h ₁ = 35.2mm) 15th surface k = 0.0000 A = -3.8567 × 10 ^-5 B = 4.7754 × 10 ^-8 C = -1.2011 × 10 ^-9 D = 0.0000 ｜ xa ₂ (h ₂ ) −x ₂ (h ₂ ) ｜ ＝ 0.240mm (h ₂ = 8.7mm) (Condition-compatible numerical value) (1 ) 1.722 × 10 ^-2 (2) 2.759 × 10 ^-2 (3) -0.338 (4) 0.703 (5) 1.166 [Fourth Embodiment] Table 4 below shows specifications according to the fourth embodiment. In the specification table of the embodiment, f indicates the focal length and F indicates the F number. The leftmost number represents the order from the object side of the lens surface, r is the radius of curvature of the lens surface, and d
Is the lens surface distance, and n and ν are values of the refractive index and Abbe number for the d-line (λ = 587.6 nm). In this embodiment, aberration correction is performed by including the prism block PB showing a plane parallel plate such as a color separation prism and various filters, and therefore these data are also shown.

Further, the aspherical shape is expressed by the above equation (7).

[0047]

[Table 4] f = 8.75 to 127 F = 1.71 to 2.23 (Variable spacing during zooming) f 8.75 40 127 d 9 0.6445 30.2432 39.6913 d18 39.1961 5.5197 3.6309 d21 7.4568 11.5344 3.9752 (aspherical coefficient) 3rd surface k = 0.0000 A = -2.6356 × 10 ^-7 B = 1.8109 × 10 ^-11 C = -1.7028 × 10 ^-14 D = 0.0000 ｜ xa ₁ (h ₁ ) −x ₁ (h ₁ ) ｜ ＝ 0.403mm (h ₁ = 35.05mm) 15th surface k = 0.0000 A = -4.5754 × 10 ^-5 B = 3.8469 × 10 ^-8 C = -1.5146 × 10 ^-9 D = 0.0000 ｜ xa ₂ (h ₂ ) −x ₂ (h ₂ ) ｜ ＝ 0.273mm (h ₂ = 8.55mm) (Condition-compatible numerical value) (1 ) 1.150 × 10 ^-2 (2) 3.193 × 10 ^-2 (3) -0.807 (4) 0.701 (5) 1.166 Figures 6 (a), (b), (c) and Figures 8 (a), (b) , (c) are aberration diagrams at the wide-angle end, aberration diagrams at the intermediate focal length state, and aberration diagrams at the telephoto end of the third and fourth examples, respectively. In each aberration diagram, F is the F number, y is the image height, and d is the d line (λ
= 587.6 nm), SC shows the sine condition. In the diagram of astigmatism, the broken line M is the meridional image plane and the solid line S is
Indicates the sagittal image plane.

From the comparison of the aberration diagrams, it is apparent that the third and fourth examples have excellent imaging performance in which various aberrations are favorably corrected from the wide-angle end to the telephoto end. [Fifth Embodiment] Next, referring to FIG. 9, a fifth embodiment of the present invention will be described.
An example will be described. FIG. 9 is a lens configuration diagram of the fifth example.

The fifth embodiment shown in FIG. 9 is the fourth lens group G.
The configuration of ₄ is different from that of the second embodiment shown in FIG. In the present embodiment, in order to simplify the explanation, this fourth lens group G ₄
The configuration of will be described. In FIG. 9, the fourth lens group G ₄ includes a meniscus-shaped positive lens L ₄₁ having a concave surface on the object side, a biconvex positive lens L ₄₂ having a stronger curvature on the object side, and a biconvex shape. A cemented lens composed of a positive lens L ₄₃ and a biconcave negative lens L ₄₄ having a stronger curvature toward the object side, a biconvex positive lens L ₄₅ , a biconcave negative lens and a biconvex positive lens. A cemented lens consisting of a lens L ₄₆
And a cemented lens L _{47 including} a biconvex positive lens and a meniscus negative lens having a concave surface facing the object side, and a biconvex positive lens L ₄₈ .

Table 5 below shows specifications according to this embodiment. In the specification table of the embodiment, f is the focal length and F is F.
Indicates the number. The number at the left end represents the order from the object side of the lens surface, r is the radius of curvature of the lens surface, d is the distance between the lens surfaces, n and ν are the refractive index and the d-line of the Abbe number (λ = 587.6 nm) Is the value for. In this embodiment, aberration correction is performed by including the prism block PB showing a plane parallel plate such as a color separation prism and various filters, and therefore these data are also shown.

The aspherical shape is expressed by the above-mentioned equation (7).

[0052]

[Table 5] f = 8.27 to 159.5 F = 1.82 to 2.47 (Variable spacing in zooming) f 8.27 40 159.5 d 9 0.6829 35.8419 48.1000 d18 51.8105 10.0885 5.1527 d21 5.7830 12.3460 5.0236 ( aspherical coefficients) third surface k = -3.9187 A = -1.6634 × 10 -7 B = 2.3628 × 10 - ¹¹ C = -2.7906 × 10 ^-14 D = 8.0568 × 10 ^-18 ｜ xa ₁ (h ₁ ) −x ₁ (h ₁ ) ｜ ＝ 0.813mm (h ₁ = 40.4mm) 15th surface k = 0.0000 A =- 1.2873 × 10 ^-5 B = 0.0000 C = 0.0000 D = 0.0000 ｜ xa ₂ (h ₂ ) −x ₂ (h ₂ ) ｜ ＝ 0.079mm (h ₂ = 8.85mm) (Values corresponding to conditions) (1) 2.012 × 10 ^-2 (2) 8.927 × 10 ^-3 (3) -0.314 (4) 0.679 (5) 1.029 FIGS. 10 (a), (b) and (c) show various aberrations at the wide angle end of the fifth embodiment. The figure shows various aberration diagrams in the intermediate focal length state, and various aberration diagrams at the telephoto end. In each aberration diagram, F is the F number, y is the image height, d is the d line (λ = 587.6 nm), and SC is the sine condition. In the diagram of astigmatism, the broken line M
Indicates the meridional image plane, and the solid line S indicates the sagittal image plane.

From a comparison of the aberration diagrams, it is apparent that the fifth embodiment has excellent imaging performance, with various aberrations corrected well from the wide-angle end to the telephoto end. [Sixth Embodiment] Next, a sixth embodiment will be described with reference to FIG. FIG. 11 is a lens configuration diagram of the sixth example.

The fifth embodiment shown in FIG. 11 differs from the second embodiment of FIG. 3 in the construction of the second lens group G ₂ and the fourth lens group G ₄ . In this embodiment, for the sake of simplicity, the configurations of the second lens group G ₂ and the fourth lens group G ₄ will be described. In FIG. 11, the second lens group G ₂ includes, in order from the object side, a negative meniscus lens L ₂₁ having a convex surface facing the object side, a positive meniscus lens having a concave surface facing the object side, and a biconcave lens. A cemented lens L ₂₁ consisting of a negative lens
And a biconvex positive lens L ₂₃ having a stronger curvature on the image side.
And a meniscus negative lens L having a concave surface facing the object side.
_{With 24} and.

The fourth lens group G ₄ includes, in order from the object side, a positive meniscus lens L having a concave surface facing the object side.
₄₁ , a biconvex positive lens L ₄₂ , a cemented lens including a biconvex positive lens L _43, and a meniscus negative lens L ₄₄ having a concave surface facing the object side, and a biconvex positive lens L ₄₅
And a cemented lens L _{46 including a} biconcave negative lens having a stronger curvature toward the image side and a biconvex positive lens, and a biconvex positive lens having a stronger curvature toward the image side and the object side. It has a cemented lens L _{47 including} a negative meniscus lens having a concave surface, and a biconvex positive lens L ₄₈ having a stronger curvature toward the object side.

Table 6 below shows specifications according to this embodiment. In the specification table of the embodiment, f is the focal length and F is F.
Indicates the number. The number at the left end represents the order from the object side of the lens surface, r is the radius of curvature of the lens surface, d is the distance between the lens surfaces, n and ν are the refractive index and the d-line of the Abbe number (λ = 587.6 nm) Is the value for. In this embodiment, aberration correction is performed by including the prism block PB showing a plane parallel plate such as a color separation prism and various filters, and therefore these data are also shown.

Further, the aspherical shape is expressed by the above equation (7).

[0058]

[Table 6] f = 8.75 to 127 F = 1.71 to 2.24 (Variable spacing during zooming) f 8.75 40 127 d 9 0.6404 30.2392 39.6871 d19 39.2006 5.5242 3.6354 d22 7.4568 11.5344 3.9752 (aspherical coefficient) 3rd surface k = 0.0000 A = -2.6356 × 10 ^-7 B = 1.8109 × 10 ^-11 C = -1.7028 × 10 ^-14 D = 0.0000 ｜ xa ₁ (h ₁ ) −x ₁ (h ₁ ) ｜ ＝ 0.403mm (h ₁ = 35.05mm) 15th surface k = 0.0000 A = -4.7228 × 10 ^-5 B = 4.1317 × 10 ^-8 C = -1.6405 × 10 ^-9 D = 0.0000 ｜ xa ₂ (h ₂ ) −x ₂ (h ₂ ) ｜ ＝ 0.340mm (h ₂ = 8.9mm) (Values corresponding to conditions) (1 ) 1.150 × 10 ^-2 (2) 3.820 × 10 ^-2 (3) -0.783 (4) 0.703 (5) 1.166 FIGS. 12 (a), (b), and (c) are the wide-angle end of the sixth embodiment, respectively. The various aberration diagrams at, the various aberration diagrams at the intermediate focal length state, and the various aberration diagrams at the telephoto end are shown. In each aberration diagram, F is the F number, y is the image height, d is the d line (λ = 587.6 nm), and SC is the sine condition. In the diagram of astigmatism, the broken line M
Indicates the meridional image plane, and the solid line S indicates the sagittal image plane.

From a comparison of the aberration diagrams, it is apparent that the sixth embodiment has excellent imaging performance, with various aberrations corrected well from the wide-angle end to the telephoto end. As described above, according to each of the above-described embodiments, it is possible to realize a high-performance zoom lens that has a large zoom ratio, is bright, and is small in size, and that various aberrations are well corrected.

[0060]

As described above, according to the present invention, it is possible to provide a high-performance zoom lens which is compact, lightweight, has high specifications.

[Brief description of drawings]

FIG. 1 is a lens configuration diagram of a first embodiment according to the present invention.

FIG. 2 is a diagram of various types of aberration in each focal length state of the first example.

FIG. 3 is a lens configuration diagram of a second embodiment according to the present invention.

FIG. 4 is a diagram of various types of aberration in each focal length state of the second example.

FIG. 5 is a lens configuration diagram of a third embodiment according to the present invention.

FIG. 6 is a diagram of various types of aberration in each focal length state of the third example.

FIG. 7 is a lens configuration diagram of a fourth example according to the present invention.

FIG. 8 is a diagram of various types of aberration in each focal length state of the fourth example.

FIG. 9 is a lens configuration diagram of a fifth embodiment according to the present invention.

FIG. 10 is a diagram of various types of aberration in each focal length state of the fifth example.

FIG. 11 is a lens configuration diagram of a sixth example according to the present invention.

FIG. 12 is a diagram of various types of aberration in each focal length state of the sixth example.

FIG. 13 is a second lens group G of the zoom lens according to the present invention.
FIG. 7 is an explanatory view showing the action of ₂ .

[Explanation of symbols]

G ₁ ... 1st lens group, G ₂ ... 2nd lens group, G ₃ ... 3rd lens group, G ₄ ... 4th lens group,

Claims (4)

[Claims] 1. A first lens group G ₁ having a positive refractive power, a second lens group G ₂ having a negative refractive power, a third lens group G ₃ having a negative refractive power, and a positive lens group in order from the object side. A zoom lens having a fourth lens group G ₄ having a refractive power, wherein the second lens group G is used when zooming from the wide-angle end to the telephoto end.
₂ moves from the object side to the image side along the optical axis, and the third lens group G ₃ moves so as to reciprocate on the optical axis, and the first lens group G ₁ moves from the optical axis to the periphery. At least one aspherical lens surface having a gradually increasing negative refractive power or gradually decreasing a positive refractive power, the second lens group G ₂ includes: A zoom characterized by having at least one aspherical lens surface with gradually increasing positive refracting power toward the periphery or with an aspherical surface having gradually decreasing negative refracting power, and satisfying the following conditions: lens. 10 ⁻³ <| xa ₁ (h ₁ ) −x ₁ (h ₁ ) | / h ₁ <10
^-1 10 ^-3 <| xa ₂ (h ₂ ) -x ₂ (h ₂ ) | / h ₂ <10
^-1 where h _{1 is} the maximum effective radius of the aspherical lens surface in the first lens group G ₁ , h _{2 is} the maximum effective radius of the aspherical lens surface in the second lens group G _2. Radius, xa ₁ (h ₁ ): Coordinates where the apex of the aspheric surface of the first lens group G ₁ is the origin, the x axis is the optical axis, and the y axis is a straight line passing through the origin and orthogonal to the x axis. When expressed in a system,
The value of x at the maximum effective radius h ₁ , xa ₂ (h ₂ ): The apex of the aspheric surface of the second lens group G ₂ is the origin, the x axis is the optical axis, and the y axis is the origin. When expressed in a coordinate system that is a straight line orthogonal to the x-axis,
The value of x at the maximum effective radius h ₂ , x ₁ (h ₁ ): The apex of the aspherical surface of the first lens group G ₁ is the origin, the x axis is the optical axis, and the y axis is the origin. When expressed in a coordinate system that is a straight line orthogonal to the x-axis,
The value of x of the paraxial radius of curvature of the aspherical lens surface at the maximum effective radius h ₁ , x ₂ (h ₂ ): Taking the apex of the aspherical surface of the second lens group G ₂ as the origin, and x When the axis is the optical axis and the y-axis is a straight line that passes through the origin and is orthogonal to the x-axis,
A value of x of a paraxial radius of curvature of the aspherical lens surface at the maximum effective radius h ₂ . 2. The first lens group G ₁ includes, in order from the object side, a negative lens group L ₁₁ and at least three positive lens groups L 1.
₁₂ , L ₁₃ , and L _14, and the second lens group G ₂ includes at least three lens groups L
The zoom lens according to claim 1, further comprising: ₂₁ , L ₂₂ and L ₂₃ . 3. At least one of the negative lens group L ₁₁ and the positive lens group L _{12 in} the first lens group G ₁ has at least one aspherical lens surface. The zoom lens according to claim 2, wherein the zoom lens is a zoom lens. 4. The first lens group G₁Inside the negative lens group
L₁₁Is the negative lens group L₁₁Most object side lens surface
And the paraxial radius of curvature of the most image-side lens surface is R₁Over
And R ₂And -1.0 <(R₂+ R₁) / (R₂-R₁) <-0.1 is satisfied. The zoom lens according to claim 3, wherein
Z.