JPH0735978A - Zoom lens - Google Patents

Abstract

PURPOSE:To obtain a zoom lens miniaturized and light weight and with high specification and high performance by employing four lens group constitution and providing a lens surface of aspherical shape to satisfy a specific condition at a first lens group. 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. The first lens group G1 is provided with at least one lens surface of aspherical shape. The lens surface of aspherical shape satisfies condition 10<-31xa(h)-x(h)1/10<-1>. Where, the maximum effective radius of the lens surface of aspherical shape is assumed as (h), and a value of (x) in the maximum effective radius (h) by taking 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 as a coordinate system passing the origin and setting as a straight line perpendicular to the x-axis as xa(h). Also, the value of (x) of the paraxial radius of curvature of the lens surface of aspherical shape in the maximum effective radius is assumed as x(h).

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. Generally, as a means for further increasing the specifications while further reducing the size and weight of the zoom lens, or maintaining the size and weight, a configuration that strengthens the power of each lens group is used. However, there is a problem that the optical performance deteriorates.

Therefore, an object of the present invention is to provide a high-performance zoom lens which is small in size, light in weight, has high specifications.

[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 G₁Is at least
Configured to have a single aspherical lens surface,
The aspherical lens surface is from the optical axis toward the periphery,
A shape in which the negative refracting power gradually increases or a positive refracting power gradually increases
It is defined as a weakening shape and is designed to satisfy the following conditions.
Is made.

[0006]

## EQU1 ## 10 ⁻³ <| xa (h) −x (h) | / h <10 ⁻¹ (1) where h is the maximum effective radius of the aspherical lens surface, and xa (h) is not The value of x at the maximum effective radius h is expressed by a coordinate system in which the apex of the spherical lens surface 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 perpendicular to the x axis. (H): When the apex of the aspherical lens surface is taken as the origin, the x-axis is the optical axis, and the y-axis is a straight line that passes through the origin and is perpendicular to the x-axis. X is the paraxial radius of curvature of the aspherical lens surface.

[0007]

According to the present invention, first, since the first lens group G ₁ has a positive refractive power, given the aberration correction in the first lens group G within _1, at least one surface of the first lens group G ₁ The aspheric surface of has a shape in which the negative refracting power becomes stronger or the positive refracting power becomes weaker from the optical axis toward the periphery as compared with the paraxial radius of curvature of this aspherical surface. desirable.

Further, in order to satisfactorily correct various aberrations and to easily manufacture an aspherical lens, the present invention defines the optimum range of the amount of aspherical surface by the condition (1). . Here, if the upper limit of condition (1) is exceeded,
Since the amount of aspherical surface is significantly increased, it is very difficult to manufacture an aspherical lens. On the other hand, if the value goes below the lower limit, the spherical aberration at the telephoto end becomes undercorrected, which is not preferable.

Further, in the present invention, the first lens group G ₁ includes the negative lens group L ₁₁ and at least three positive lens groups in order from the object side 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 L 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 .

[0010] 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, in that case, the aspherical shape is considerably deviated from the paraxial radius of curvature of this aspherical surface, and it becomes complicated including undulations, making it difficult to manufacture and stricter tolerances such as eccentricity. Not preferable.

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 . Due to 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.

[0013]

## EQU2 ## −0.7 <(R ₂ + R ₁ ) / (R ₂ −R ₁ ) <0 (2) where R _{1 is} the paraxial curvature of the lens surface of the negative lens group L ₁₁ closest to the object side. Radius, R ₂ : Paraxial radius of curvature of the most image-side lens surface of the negative lens unit L ₁₁ .

Negative lens group L₁₁Exceeds the upper limit of condition (2)
In this case, spherical aberration on the telephoto side will be under-corrected.
Not good. Now try to correct this spherical aberration
If it is necessary to increase the amount of aspherical surface, it is difficult to manufacture.
Becomes In addition, the negative lens unit L ₁₁Exceeds the lower limit of condition (2)
However, it is preferable because the distortion of the pincushion type increases.
Not good.

The zoom lens according to the present invention is preferably constructed so as to satisfy the following conditions in addition to the above-mentioned construction.

[0016]

[Equation 3] 0.6 <F _T ^1/2・ f ₁ / f _T <0.9 (3) 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 (3) defines the optimum power of the variable power portion in order to reduce the size of the variable power 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 (3), it becomes 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.

[0019]

0.9 <| β _2W · V ^1/2 | <1.3 (4) where β _2W is the magnification of the second lens group G _{2 at} the wide-angle end, and V is the zoom ratio.

The condition (4) is a condition for maintaining good Petzval sum. As a result, although the zooming unit is downsized under the condition (3),
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. Figure 9
Second lens group G₂In the figure which shows the state of the magnification change by
is there. In FIG. 9, P is the first lens group G₁Image point by
Position, that is, the second lens group G₂Object position with respect to
2 lens group G₂The locus | trajectory of the image point formed by is shown.
Here, the second lens group G₂Let v be the scaling factor due to
Second lens group G₂The magnification at the wide-angle end and the telephoto end.
-1 / v each^1/2, -V^1/2Range W₀
-T₀If is selected as the reference variable range, the position of the image point Q is wide-angle.
The third lens group G is the same at the end and the telephoto end.₃Position of both ends
Matches with. At this time, the second lens group G ₂The scaling factor v of
It 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, if the space required to prevent mechanical interference between the lens groups is Δ, then 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

[0023]

[Formula 5] f ₂ = (f ₁ −Δ) · β _2W / (1−β _2W ) (5). 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 shown in FIG.
Reference zoom range of the second lens group G ₂ in zoom range W ₀ -
This is equivalent to selecting the area WT below T ₀ . In the present invention, the zoom range of the second lens group G ₂ be in the range of the condition (4), it is possible to weaken the negative power of the second lens group G _2.

Here, if the lower limit of the condition (4) 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. Two
The ratio of the amount of movement of the third lens group G ₃ to the amount of movement of the lens group G ₂ becomes extremely large, which is not preferable because the lens barrel mechanism for moving both groups is inconvenient.

Further, in the present invention, in order to satisfactorily correct various aberrations and maintain high performance even though the aperture ratio is large,
It is desirable that the third lens group G ₃ and the fourth lens group G ₄ have the following configurations. First, it is desirable that the third lens group G ₃ be composed of a negative lens L ₃ which is formed by bonding a biconcave negative lens and a biconvex positive lens. 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 , and a biconvex positive lens L 4.
A front group having a negative lens L ₄₄ cemented with ₄₃ and a biconvex positive lens L ₄₃ and having a surface having a stronger curvature facing the object side, a biconvex positive lens L ₄₅ , two cemented lenses L ₄₆ , L _47, and It is preferable that the rear lens group has a positive lens L ₄₈ having a surface having a stronger curvature facing the object side.

[0026]

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 zoom lens according to a first embodiment of 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, and a third lens group having a negative refractive power. It has G ₃ 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 the present embodiment, the first lens unit G ₁ and the fourth lens unit G ₁ are used for zooming from the wide-angle end to the telephoto end.
The lens group G ₄ is fixed in the optical axis direction, and
The lens group G ₂ is monotonically extended to the object side along the optical axis, and the third lens group G ₃ is configured to move so as to reciprocate on the optical axis. In the zoom lens of this embodiment,
The first lens group G ₁ includes, in order from the object side, a biconcave negative lens L ₁₁ , a biconvex positive lens L _12, and a biconvex positive lens L ₁₃ having a stronger curvature toward the object side. , A meniscus-shaped positive lens L ₁₄ having a convex surface directed toward the object side. In the present embodiment, an aspherical layer provided on the object-side lens surface of the positive lens L ₁₂ and having an aspherical surface on the object side is also shown.

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 cemented lens L _{22 including} a meniscus-shaped positive lens having a convex surface facing the image side and a biconcave negative lens, and a cemented lens L including a biconvex positive lens and a biconcave negative lens.
_{With 23} and. The third lens group G ₃ has a cemented lens L _{3 including} , in order from the object side, a biconcave negative lens and a biconvex positive lens.

The fourth lens group G ₄ includes, in order from the object side, a positive meniscus lens L having a convex surface facing the image side.
₄₁ , a biconvex positive lens L ₄₂ , a biconvex positive lens L _43, and a meniscus negative lens L having a convex surface facing the image 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 convex surface facing the image side. ₄₇ and a biconvex positive lens L ₄₈ having a stronger 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 is the focal length and F is 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 the zoom lens according to the present 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 the 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,

[0032]

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

[0033]

[Table 1] f = 8.75 to 127 F = 1.72 to 2.25 (Variable spacing during zooming) f 8.75 40 127 d 9 0.5664 30.1640 39.6122 d17 41.3281 7.6530 5.7641 d20 7.2725 11.3500 3.7907 (aspherical coefficient) 3rd surface k = 0.0000 A = -3.9124 × 10 ^-7 B = 3.2071 × 10 ^-11 C = -1.8226 × 10 ^-14 D = 0.0000 ｜ xa (h) −x (h) ｜ = 0.603mm (h = 35.5mm) (Values corresponding to conditions) (1) 1.699 × 10 ^-2 (2) -0.164 ( 3) 0.704 (4) 1.166 FIGS. 2 (a), (b), and (c) are aberration diagrams at the wide-angle end, aberration diagrams at the intermediate focal length state, and telephoto end, respectively, of the first embodiment. The various aberration figures 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 of the present invention will be described with reference to FIG. FIG. 3 is a lens configuration diagram of a zoom lens according to a second example.

The second embodiment shown in FIG. 3 is the fourth lens group G.
_FourThe configuration is different from that of the first embodiment of FIG. In this example
In order to simplify the explanation, the fourth lens group G_Fourof
Only the configuration will be described in detail. Fourth lens group G_FourIs an object
From the side, the meniscus-shaped positive lens with the convex surface facing the image side.
L₄₁And a biconvex positive lens L₄₂And a biconvex positive
Lens L₄₃And negative lens L with biconcave shape₄₄Joining consisting of
Lens and biconvex positive lens L₄₅And a biconcave negative lens
Cemented lens L including a lens and a biconvex positive lens ₄₆When,
Biconvex positive lens and meniscus type with convex surface facing the image side
Lens L consisting of a negative lens₄₇And on the object side
A biconvex positive lens L with a stronger convex surface ₄₈Have and
It

The specifications according to this embodiment are shown in Table 2 below.
In the specification table of the embodiment, f is the focal length and F is 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). Further, the aspherical shape is represented by the above formula (6). In the zoom lens according to the present embodiment as well, since the aberration correction is performed by including the prism block showing the parallel plane plate such as the color separation prism and various filters, the specifications thereof are also shown.

[0037]

[Table 2] f = 8.27 to 159.5 F = 1.81 to 2.45 (Variable spacing in zooming) f 8.27 40 159.5 d 9 0.5718 35.7308 47.9889 d17 52.0518 10.3298 5.3941 d20 5.7830 12.3460 5.0236 ( aspherical coefficients) third surface k = -3.9093 A = -1.6643 × 10 -7 B = 2.1587 × 10 - ¹¹ C = -2.7964 × 10 ^-14 D = 7.4 360 × 10 ^-18 ｜ xa (h) -x (h) ｜ ＝ 0.858mm (h = 40.4mm) (Values corresponding to conditions) (1) 2.124 × 10 ^-2 ( 2) -0.283 (3) 0.676 (4) 1.029 FIGS. 4 (a), (b) and (c) are aberration diagrams at the wide angle end and aberration diagrams at the intermediate focal length state of the second embodiment, respectively. , Shows 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 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. [Third Embodiment] Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 5 is a lens configuration diagram of a zoom lens according to a third example.

In the zoom lens of the third embodiment shown in FIG. 5, the first lens group G ₁ includes, in order from the object side, a biconcave negative lens L ₁₁ , a biconvex positive lens L _12, and an object. A biconvex positive lens L ₁₃ having a stronger curvature toward the side, and a meniscus positive lens L ₁₄ having a convex surface toward the object side. In this embodiment, 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,
A cemented lens L ₂₂ consisting of a positive lens and a double concave negative lens of meniscus shape having a convex surface facing the image side, a meniscus toward a positive lens and a negative lens and a convex surface on the object side of a bi- And a cemented lens L _{23 including} a positive lens having a shape.

The third lens group G ₃ has a cemented lens L ₃ including a biconcave negative lens and a biconvex positive lens, as in the first embodiment shown in FIG. In addition, the fourth lens group G
₄ is a meniscus-shaped positive lens L ₄₁ having a convex surface facing the image side, a biconvex positive lens L ₄₂ , a biconvex positive lens L _43, and a concave surface facing the object side in order from the object side. a cemented lens consisting of a negative lens L ₄₄ Metropolitan meniscus, a positive lens L ₄₅ of double-convex shape, a cemented lens L ₄₆ consisting of a biconcave negative lens and a positive lens of biconvex shape, a bi-convex It has a cemented lens L _{47 including} a positive lens and a meniscus negative lens having a convex surface facing the image side, and a meniscus positive lens L ₄₈ having a convex surface facing the object side.

The specifications according to this embodiment are shown in Table 3 below.
In the specification table of the embodiment, f is the focal length and F is 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). Further, the aspherical shape is represented by the above formula (6). In the zoom lens according to the present embodiment as well, the aberration correction is performed including the prism block PB showing the parallel plane plate such as the color separation prism and various filters, and therefore these data are also shown.

[0043]

[Table 3] f = 8.75 to 127 F = 1.72 to 2.14 (Variable spacing during zooming) f 8.75 40 127 d 8 0.4287 34.0411 45.2350 d16 48.0608 9.5394 3.9992 d19 5.0260 9.9351 4.2814 (aspherical coefficient) 2nd surface k = 0.0000 A = 1.6502 × 10 ^-7 B = -5.7039 × 10 ^-12 C = 1.0880 × 10 ^-14 D = 0.0000 ｜ xa (h) −x (h) ｜ ＝ 0.267mm (h = 35.15mm) (Values corresponding to conditions) (1) 7.596 × 10 ^-3 (2) -0.465 (3 ) 0.766 (4) 1.034 Figures 6 (a), (b), and (c) show various aberration diagrams at the wide-angle end, various aberration diagrams at the intermediate focal length state, and various telephoto ends, respectively, of the third embodiment. The aberration diagram is 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 the aberration diagrams, 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. [Fourth Embodiment] Next, a fourth embodiment of the present invention will be described with reference to FIG. FIG. 7 is a lens configuration diagram of a zoom lens according to a fourth example.

In the fourth embodiment, the second lens group G₂And 4th
Group G_FourIs different from the first embodiment shown in FIG.
It In this embodiment, in order to simplify the explanation, the second lens is used.
Group G ₂And the fourth lens group G_FourAnd the configuration will be described in detail.
Second lens group G₂Is a convex surface on the object side in order from the object side.
Meniscus negative lens L_{twenty one}And a convex surface on the image side
Positive meniscus lens and negative biconcave lens
Cemented lens L consisting of_{twenty two}And a biconvex positive lens L_{twenty three}
And a biconcave negative lens L_{twenty four}Have and.

Fourth lens group G_FourIs the image in order from the object side
Meniscus positive lens L with the convex surface facing the side₄₁And both
Convex positive lens L₄₂And a biconvex positive lens L₄₃And both
Concave negative lens L₄₄Cemented lens consisting of and, and biconvex
Positive lens L₄₅And a biconcave negative lens and a biconvex
A cemented lens L consisting of a positive lens₄₆And the convex shape
Lens and a meniscus negative lens with the convex surface facing the image side
Cemented lens L ₄₇And a stronger convex surface
Double-convex positive lens L₄₈Have and.

The specifications according to this embodiment are shown in Table 4 below.
In the specification table of the embodiment, f is the focal length and F is 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). Further, the aspherical shape is represented by the above formula (6). In the zoom lens according to the present embodiment as well, the aberration correction is performed including the prism block PB showing the parallel plane plate such as the color separation prism and various filters, and therefore these data are also shown.

[0048]

[Table 4] f = 8.27 to 159.5 F = 1.82 to 2.47 (Variable spacing in zooming) f 8.27 40 159.5 d 9 0.5691 35.8735 48.1413 d18 51.9902 10.2369 5.1862 d21 5.7123 12.1612 4.9441 ( aspherical coefficients) third surface k = -3.9077 A = -1.6630 × 10 -7 B = 2.2118 × 10 - ¹¹ C = -2.7736 × 10 ^-14 D = 7.4101 × 10 ^-18 ｜ xa (h) -x (h) ｜ ＝ 0.853mm (h = 40.5mm) (Values corresponding to conditions) (1) 2.106 × 10 ^-2 ( 2) -0.290 (3) 0.678 (4) 1.029 FIGS. 8 (a), (b), and (c) are aberration diagrams at the wide-angle end and aberration diagrams at the intermediate focal length state of the fourth embodiment, respectively. , Shows 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 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. 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.

[0050]

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 second lens group G ₂ of the zoom lens according to the present invention.
It is explanatory drawing which shows the effect | action of.

[Explanation of Codes] G ₁ ... First lens group, G ₂ ... Second lens group, G ₃ ... Third lens group, G ₄ ... Fourth 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 along the optical axis from the object side to the image side, and the third lens group G ₃ moves so as to reciprocate on the optical axis, and the first lens group G ₁ has at least one aspherical surface. The aspherical lens surface is defined as a shape in which the negative refracting power gradually becomes stronger or a shape in which the positive refracting power gradually becomes weaker from the optical axis to the peripheral portion. A zoom lens that is characterized by its satisfaction. 10 ⁻³ <| xa (h) −x (h) | / h <10 ⁻¹ where, h: maximum effective radius of the aspherical lens surface, xa (h): of the aspherical lens surface When represented by a coordinate system with the surface vertex as the origin, the x-axis as the optical axis, and the y-axis as a straight line passing through the origin and perpendicular to the x-axis, the value of x at the maximum effective radius h, x (h): When expressed in a coordinate system, it is the value of x of the paraxial radius of curvature of the aspherical lens surface at the maximum effective radius h. 2. The first lens group G ₁ has, in order from the object side, a negative lens group L ₁₁ and at least three positive lens groups L ₁₂ , L ₁₃ and L ₁₄ , and the second lens group G ₂ Is at least three lens units 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. 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 -0.7 <(R₂+ R₁) / (R₂-R₁) <0 is satisfied, The zoom lens according to claim 3 characterized in that
Z.