JPH06230283A - Zoom lens - Google Patents

Abstract

PURPOSE:To obtain a zoom lens having a small number of lenses, the excellent performance and well corrected aberration by providing at least one gradient refractive index lens having the gradient of refractive index in the direction of the optical axis. CONSTITUTION:A first lens group 1 of a positive refractive power, a second lens group 2 and a third lens group 3 having negative refractive powers, respectively, and a fourth lens group 4 having a positive refractive power and image forming action are arranged in the order from the object side. The second lens group 2 and the third lens group 3 give the zooming action by mutually and relatively moving along the optical axis 9 at the same time while keeping an image plane 8 at a constant position. The lens of the fourth lens group closest to the object side is made to be an axial type gradient refractive index lens 10. The difference between the largest refractive index and the smallest refractive index i.e. the absolute amount of the variation of refractive index is below 0.01. The lens 10 is provided in the vicinity of a diaphragm 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a video-integrated camera,
The present invention relates to a zoom lens applied to a single-lens reflex camera, a projector, etc.

[0002]

2. Description of the Related Art Conventionally, as a zoom lens used in a device such as a video-integrated camera, many compact and high-performance zoom lenses have been proposed. However, in order to make the entire apparatus such as a camera more compact and have high performance such as excellent image quality, further miniaturization and higher performance of the zoom lens are desired. In recent years, zoom lenses have been proposed that are compact and have high performance by using an aspherical lens, but it is difficult to manufacture an aspherical lens when the lens aperture is large or the aspherical shape is complicated. Therefore, problems such as high cost occur.

Under these circumstances, the progress of lens manufacturing technology has led to the introduction of a so-called gradient index lens in which the refractive index changes in the lens, as disclosed in Japanese Patent Laid-Open No. 1-243011. The gradient index lens includes a radial type whose refractive index changes in the radial direction of the lens, and an axial type whose refractive index changes in the optical axis direction of the lens. The gradient index lens element has an effect equivalent to that of an aspherical surface in terms of aberration correction by making an appropriate lens shape and a refractive index gradient wait. Furthermore, the gradient index lens can also correct chromatic aberration that cannot be corrected by an aspherical surface by appropriately changing the gradient of the refractive index for each wavelength.

[0004]

However, the radial type of the above gradient index lenses has the problems that it is difficult to obtain a large aperture lens by the current manufacturing method and the cost becomes high. On the other hand, the axial type has a large aperture and is very likely to be put into practical use as a zoom lens for video-integrated cameras, etc., but the difference between the largest refractive index and the smallest refractive index, that is, the refractive index. When the change amount of is large, there is a problem that it is difficult to realize.

It is an object of the present invention to apply an axial type gradient index lens which is easy to manufacture, and considers the arrangement location and the like so that its ability can be effectively exerted, whereby the number of lenses can be reduced. The objective is to provide a compact zoom lens with good performance in which aberrations are well corrected.

[0006]

Means for Solving the Problems I having a positive refractive power
The lens group (1) and each of them have a negative refracting power, and while keeping the image plane (8) at a fixed position, they simultaneously move relative to each other along the optical axis (9) to achieve a zooming action. A second lens group (2) and a third lens group which present, and a fourth lens group (4) which has a positive refractive power and exhibits an image forming action,
Or a first lens group (I) having negative refracting power, which exhibits a zooming effect by moving relative to each other at the same time along the optical axis (9). 11) and a second lens group (12) having a positive refractive power, and a zoom lens formed by arranging the second lens group (12) in order from the object side, and at least two lens groups of the lens group. In a zoom lens that performs zooming by changing the axial spacing of lens groups, at least one gradient index lens having a gradient gradient in the optical axis direction is provided, and the gradient index lens is the largest. The difference between the refractive index and the smallest refractive index, that is, the absolute value of the amount of change in the refractive index is 0.01 or less, and the gradient index lens is provided near the diaphragm or in a lens group including the diaphragm. It has a configuration.

[0007]

Next, the operation of the present invention will be described.

FIG. 20 is a principle view showing a gradient index lens in a zoom lens according to the present invention.

The gradient index lens (10) shown in FIG. 20 (a) has a refractive index gradient (16) as shown in FIG. 20 (b) by a manufacturing method such as ion exchange. ing. As shown in the figure, the gradient index lens (10) is a so-called axial gradient index lens (10) in which the refractive index changes along the optical axis (9) direction (z direction) of the lens. Is. That is, with respect to the lens thickness t, it has a refractive index n ₁ at the apex of the spherical surface on the left side in FIG. 20 (a), and refraction along the optical axis (9) along the refractive index gradient (16). The refractive index becomes smaller and the refractive index becomes n ₀ at a certain point. Due to the gradient of the refractive index of the gradient index lens (10), for example, in the case of a lens having a spherical surface, the refractive index differs depending on the lens height of the spherical surface (y-axis direction shown in FIG. 20). It has a function of performing aberration correction equivalent to that of an aspherical surface by giving a different shape and a refractive index gradient. Gradient Index Lens (1
0), the difference between the largest refractive index and the smallest refractive index, that is, the amount of change in the refractive index (Δ shown in FIG. 20B).
If n) is large, the aberration correction capability is also improved. However, a gradient index lens having a large amount of change in refractive index is difficult to manufacture, and the cost increases. Therefore, it is desirable to satisfy the following conditions.

[0010]

## EQU1 ## In the gradient index lens (10), not only the gradient of the refractive index as shown in FIG. 20 (b) but also n ₁ in FIG. 20 (b) is n _0. It may be smaller, or may have a refractive index gradient from the middle of the lens thickness.

Next, the operation of the zoom lens to which the gradient index lens according to the present invention is applied will be described.

FIG. 1 is a sectional view showing a structure of a zoom lens according to the present invention.

The zoom lens shown in the figure has the I-th lens group (1) having a positive refracting power, and each of them has a negative refracting power, and while keeping the image plane (8) at a constant position, the optical axis ( 9) the second lens group (2) and the third lens group which exhibit a zooming effect by simultaneously moving relative to each other, and the fourth lens group which has a positive refracting power and exhibits an imaging effect
(4) and are arranged in order from the object side. The fourth lens group (4) includes a lens having a positive refractive power, a lens having a negative refractive power, a lens having a positive refractive power, a lens having a negative refractive power, and a positive refractive power. And a lens having the above are arranged in order from the object side, and the lens closest to the object in the IV lens group (4) is an axial type gradient index lens (10). With such a configuration, the gradient index lens is arranged in the vicinity of the diaphragm, and it is possible to provide a function of correcting spherical aberration and the like in particular.

FIG. 4, FIG. 5 and FIG. 10 are sectional views showing another structure of the zoom lens according to the present invention.

In the zoom lens shown in these figures, the IV lens group (4) has a lens having a positive refracting power, a lens having a negative refracting power, and a lens having a positive refracting power.
Are arranged in order from the object side, and at least one of the lens closest to the object in the IV lens group (4) or the lens closest to the image plane (8) is a gradient index lens. The configuration is (10).
Furthermore, in the zoom lens shown in FIGS. 4, 5 and 10, the fourth lens group (4) is provided with at least one aspherical surface. As a result, it becomes possible to satisfactorily correct aberrations with a small number of lenses due to the synergistic effect of aberration correction by the gradient of the refractive index of the gradient index lens (10) and aberration correction of the aspherical surface. Further, by making at least one of the surfaces of the gradient index lens (10) as an aspherical surface, a greater aberration correction effect can be obtained.

13 and 14 are sectional views showing another structure of the zoom lens according to the present invention.

The zoom lens shown in the figure has a negative refracting power and is the first I lens group (1) having a negative refracting power which exhibits a zooming effect by simultaneously moving relative to each other along the optical axis (9).
1) and the second lens group (12) having positive refractive power,
Are arranged in order from the object side, the second lens group (12) has a gradient index lens (10) having a gradient of refractive index in the optical axis direction, and further has at least one aspherical surface. The configuration is provided. As a result, due to the synergistic effect of the above-described aberration correction, it is possible to obtain a zoom lens having good performance with a small number of lenses.

The gradient index lens (10) described above is used.
Needless to say, it is possible to correct chromatic aberration that cannot be corrected with an aspherical surface, by appropriately changing the refractive index gradient for each wavelength.

Further, in the drawing showing the structure of the zoom lens described above, the crystal plate (7) is introduced when the zoom lens is used as a lens for a video camera, for example, and does not have a function as a lens. It has a function as a frequency optical filter. Also, the shielding surface (6)
Has an action of cutting an unnecessary portion of the light flux mainly reaching the periphery of the image plane (8).

[0020]

EXAMPLES Next, examples of the present invention will be described.

As described above, FIG. 1, FIG. 4, FIG.
0, FIG. 13 and FIG. 14 are sectional views showing the configuration of one embodiment of the zoom lens according to the present invention.

First, specific numerical examples of the lens system shown in FIG. 1 will be shown. This is f = 9.5-52.7, F = 1.
This is the case of the 8 zoom lens.

R ₁ = 52.05, d ₁ = 0.90, n ₁ = 1.8467, ν ₁ = 24 r ₂ = 27.89, d ₂ = 5.23, n ₂ = 1.5891, ν ₂ = 61 r ₃ = -90.34, d ₃ = 0.20 r ₄ = 23.54, d ₄ = 2.77, n ₃ = 1.5891, ν ₃ = 61 r ₅ = 50.30, d ₅ = variable _{r 6 = 18.91, d 6 =} 0.85, n 4 = 1.7432, ν 4 = 49 r 7 = 8.827, d 7 = 2.99 r 8 = -14.58, d _{8 = 0.85, n 5 = 1.7432} , ν 5 = 49 r 9 = 9.945, d 9 = 2.48, n 6 = 1.8467, ν 6 = 24 r 10 = 264.2, d ₁₀ = variable _{r 11 = -16.14, d 11 =} 0.85, n 7 = 1.7283, ν 7 = 28 r 12 = -75.06, d 12 = variable r ₁₃ = 26.52, d ₁₃ = 4 _{00, n 8 = 1.6861, ν} 8 = 33 r 14 = -24.01, d 14 = 1.50 r 15 = -11.08, d 15 = 1.00, n 9 = 1.8052, ν _{9 = 25 r 16 = -14.82,} d 16 = 1.00 r 17 = ∞ ( _{stop), d 17 = 5.00 r 18} = 18.99, d 18 = 2.60, n 10 = 1. 6968, ν ₁₀ = 55 r ₁₉ = -274.2, d ₁₉ = 0.85 r ₂₀ = 19.32, d ₂₀ = 0.85, n ₁₁ = 1.8052, ν ₁₁ = 25 r ₂₁ = 9. 940, d ₂₁ = 1.00 r ₂₂ = 13.70, d ₂₂ = 2.60, n ₁₂ = 1.5891, ν ₁₂ = 61 r ₂₃ = -91.37, d ₂₃ = 3.00 r ₂₄ = ∞, d ₂₄ = 4.00 r ₂₅ = ∞, d ₂₅ = 6.00, n ₁₃ = 1.5168, ν ₁₃ = 64 r ₂₆ = ∞ In the above, r _i is the i-th lens from the object side. It is the radius of curvature of the surface, and when the center of curvature is on the image plane side when viewed from the lens surface, it is positive, and when it is on the object side, it is negative.

D _i represents the distance on the optical axis between the i-th lens surface and the (i + 1) -th lens surface adjacent thereto. Further, n _j and ν _j are j from the object side, respectively.
The refractive index and Abbe number of the th lens are shown.

In addition, r _{1 to} r ₅ are the radii of curvature of the respective lens surfaces constituting the I-th lens group (1), and r _{6 to} r ₁₀ are the II-th lenses.
The radius of curvature of the lens surfaces constituting the lens group and _{(2), r 11, r} 12 is the radius of curvature of the lens surfaces constituting the first III lens group _{(3), r 13 ~r 2} 3 Part In the IV lens group (4), r ₁₇ included in the IV lens group (4) is a diaphragm (5), r ₂₄ is a shielding surface (6), and r _{25 to} r ₂₆ are quartz plates (7), respectively. Is the radius of curvature of each lens surface constituting

In the above, d ₅ , d ₁₀ and d ₁₂ differ depending on the focal length f. An example is shown below.

When f = 9.5 mm: d ₅ = 0.59 mm, d
_{When 10} = 15.1 mm, d ₁₂ = 4.86 mm and f = 33.8 mm: d ₅ = 14.6 mm, d ₁₀ = 1.78 m
When m, d ₁₂ = 4.18 mm and f = 52.7 mm: d ₅ = 17.5 mm, d ₁₀ = 2.62 m
m, d ₁₂ = 0.50 mm In this embodiment, r ₁₃ and r ₁₄ are the gradient index lens (10), and the shape of the gradient of the refractive index is expressed by the following equation.

[0028]

[Formula 2] n _Z = N ₀₀ + N ₀₁ · z + N ₀₂ · z ² + N ₀₃ · z ³ + N ₀₄ · z ⁴ + N ₀₅ · z ⁵ However, Z is the optical axis with the image plane side being positive from the point where the lens is located. The upper distances, N _{00 to} N ₀₅ , represent coefficients representing the refractive index gradient.

The gradient index lens (10) in the above embodiment has a gradient of refractive index from a point 1 mm away from the spherical apex of the 13th surface toward the image plane side, and the coefficient thereof is, for example, as shown below. is there.

N ₀₀ = 1.6861, N ₀₁ = 1.66 × 10 ~
² , N ₀₂ = 3.28 x 10 to ³ N ₀₃ = -4.76 x 10 to ⁴ , N ₀₄ = -3.16 x 10 to ⁴ , N ₀₅ = 9.8
0 × 10¯ ⁵ 2, when the object distance ∞ in the above Example 1, the characteristic diagram showing the aberration when focal length 9.5 mm, 3
Similarly, is a characteristic diagram showing aberrations when the focal length is 52.7 mm. In each characteristic diagram, (a) is the center of the image plane of the light beam, (b) is the height of the light beam on the image plane corresponding to 0.6 times the maximum angle of view at each focal length, ( FIG. 3C is a diagram corresponding to the ray height on the image plane corresponding to 0.9 times the maximum angle of view for each focal length.

In the above embodiment, the number of lenses is small and the size is reduced by the action of the gradient index lens (10), and the aberration is satisfactorily corrected as shown in FIGS.

Next, a second specific numerical example shown in FIG. 4 will be shown. These are the cases of a zoom lens with f = 9.5 to 52.3 and F = 1.8.

R ₁ = 52.05, d ₁ = 0.90, n ₁ = 1.8467, ν ₁ = 24 r ₂ = 27.89, d ₂ = 5.23, n ₂ = 1.5891, ν ₂ = 61 r ₃ = -90.34, d ₃ = 0.20 r ₄ = 23.54, d ₄ = 2.77, n ₃ = 1.5891, ν ₃ = 61 r ₅ = 50.30, d ₅ = variable _{r 6 = 18.91, d 6 =} 0.85, n 4 = 1.7432, ν 4 = 49 r 7 = 8.827, d 7 = 2.99 r 8 = -14.58, d _{8 = 0.85, n 5 = 1.7432} , ν 5 = 49 r 9 = 9.945, d 9 = 2.48, n 6 = 1.8467, ν 6 = 24 r 10 = 264.2, d ₁₀ = variable _{r 11 = -16.14, d 11 =} 0.85, n 7 = 1.7283, ν 7 = 28 r 12 = -75.06, d 12 = variable r ₁₃ * = 12.34, d ₁₃ = _{.00, n 8 = 1.6512, ν} 8 = 33 r 14 = -50.75, d 14 = 2.03 r 15 = ∞ ( _{stop), d 15 = 1.00 r 16} = 21.80, d ₁₆ = 2.00, n ₉ = 1.8052, ν ₉ = 25 r ₁₇ = 10.19, d ₁₇ = 1.57 r ₁₈ = 19.93, d ₁₈ = 4.00, n ₁₀ = 1.7130. , Ν ₁₀ = 54 r ₁₉ = -20.43, d ₁₉ = 3.50 r ₂₀ = ∞, d ₂₀ = 4.00 r ₂₁ = ∞, d ₂₁ = 6.00, n ₁₁ = 1.5168, ν ₁₁ = 64 r ₂₂ = ∞ Each symbol has the same content as in the first embodiment.

The I-th lens group (1) to the III-th lens group (3) are equivalent to those in the first embodiment, and r _{13 to} r ₁₉ are the IV-th lens group (4) and the IV-th lens group ( 4) r ₁₅ contained in the diaphragm (5), r ₂₀ shielding surface (6), r ₂₁ ~r ₂₂
Is the radius of curvature of each lens surface that constitutes each of the crystal plates (7).

In the second embodiment, d ₅ , d ₁₀ ,
d ₁₂ varies depending on the focal length f, and an example is shown below.

When f = 9.5 mm: d ₅ = 0.59 mm, d
_{When 10} = 15.1 mm, d ₁₂ = 4.86 mm and f = 33.6 mm: d ₅ = 14.6 mm, d ₁₀ = 1.78 m
When m, d ₁₂ = 4.18 mm and f = 52.3 mm: d ₅ = 17.5 mm, d ₁₀ = 2.62 m
m, d ₁₂ = 0.50 mm In the present embodiment, r ₁₃ and r ₁₄ are the gradient index lens (10), and 2 mm from the spherical vertex of the 13th surface to the image plane side.
It has a refractive index gradient from the offset point. The coefficient representing the refractive index gradient is, for example, as shown below.

N ₀₀ = 1.6512, N ₀₁ = 1.66 × 10 ~
² , N ₀₂ = -3.28 x 10 to ³ N ₀₃ = 4.76 x 10 to ⁴ , N ₀₄ = 3.16 x 10 to ⁴ , N ₀₅ = -9.8
0 × 10 to ^{5 Further} , in this embodiment, the lens surface having a radius of curvature marked with * is an aspherical surface, and the shape is expressed by the aspherical surface coefficient as in the following expression.

[0038]

Z ′ = C · Y ² / {1 + √ (1- (K + 1) · C ² · Y ² )}
+ A ₄ · Y ⁴ + A ₆ · Y ⁶ + A ₈ · Y ⁸ + A ₁₀ · Y ¹⁰ However, Z'is the distance from the tangent plane of the aspherical vertex of the point on the aspherical surface at the height Y from the optical axis, C Is the curvature of the reference spherical surface (1 / r), K is the conic constant, Y is the height from the optical axis, and A is
Reference symbols _{4 to} A ₁₀ denote aspherical coefficients of 4th to 10th orders, respectively.

The aspherical surface coefficients in the second embodiment are shown below.

13th surface: K = -1.4052, A ₄ = -1.2656 × 10
~ ⁴ , A ₆ = 4.1425 x 10 ~ ⁶ , A ₈ = -9.8185 x 10 ~ ⁸ , A ₁₀
= 9.4019 × 10 to ¹⁰ FIG. 6 is a characteristic diagram showing aberrations when the focal length is 9.5 mm when the shooting distance is ∞ in the second embodiment, and FIG.
Similarly, is a characteristic diagram showing aberrations when the focal length is 52.3 mm. In addition, (a) shown in each characteristic diagram,
The symbols (b) and (c) have the same contents as in the case of the first embodiment.

In the second embodiment described above, the action of the gradient index lens (10) and the aspherical surface provided on the lens has a synergistic effect on aberration correction, thereby reducing the number of lenses and downsizing. As shown in FIGS. 6 and 7, the aberration is well corrected.

Next, a third concrete numerical example as shown in FIG. 5 will be shown. These are f = 9.5-52.1, F =
This is the case of the 1.8 zoom lens.

R ₁ = 52.05, d ₁ = 0.90, n ₁ = 1.8467, ν ₁ = 24 r ₂ = 27.89, d ₂ = 5.23, n ₂ = 1.5891, ν ₂ = 61 r ₃ = -90.34, d ₃ = 0.20 r ₄ = 23.54, d ₄ = 2.77, n ₃ = 1.5891, ν ₃ = 61 r ₅ = 50.30, d ₅ = variable _{r 6 = 18.91, d 6 =} 0.85, n 4 = 1.7432, ν 4 = 49 r 7 = 8.827, d 7 = 2.99 r 8 = -14.58, d _{8 = 0.85, n 5 = 1.7432} , ν 5 = 49 r 9 = 9.945, d 9 = 2.48, n 6 = 1.8467, ν 6 = 24 r 10 = 264.2, d ₁₀ = variable _{r 11 = -16.14, d 11 =} 0.85, n 7 = 1.7283, ν 7 = 28 r 12 = -75.06, d 12 = variable r ₁₃ = ∞ (stop), d ₁₃ = 0 _{50 r 14 * = 11.35, d} 14 = 5.00, n 8 = 1.6512, ν 8 = 33 r 15 = -59.38, d 15 = 2.03 r 16 = 23.44, d 16 = 2.00, n ₉ = 1.8052, ν ₉ = 25 r ₁₇ = 10.21, d ₁₇ = 1.57 r ₁₈ = 21.22, d ₁₈ = 4.00, n ₁₀ = 1.7130, v ₁₀ = 54 r ₁₉ = -20.61, d ₁₉ = 3.50 r ₂₀ = ∞, d ₂₀ = 4.00 r ₂₁ = ∞, d ₂₁ = 6.00, n ₁₁ = 1.5168, v ₁₁ = 64 r ₂₂ = ∞ Each symbol has the same content as in the first embodiment.

The I-th lens group (1) to the III-th lens group (3) are the same as those in the first embodiment, and r _{13 to} r ₁₉ are the IV lens group (4) and the IV lens group ( R ₁₃ included in 4) is a diaphragm (5), r ₂₀ is a shielding surface (6), and r _{21 to} r ₂₂
Is the radius of curvature of each lens surface that constitutes each of the crystal plates (7).

In the second embodiment, d ₅ , d ₁₀ ,
d ₁₂ varies depending on the focal length f, and an example is shown below.

When f = 9.5 mm: d ₅ = 0.59 mm, d
_{When 10} = 15.1 mm, d ₁₂ = 4.86 mm and f = 33.6 mm: d ₅ = 14.6 mm, d ₁₀ = 1.78 m
When m, d ₁₂ = 4.18 mm f = 52.3 mm: d ₅ = 17.5 mm, d ₁₀ = 2.62 m
m, d ₁₂ = 0.50 mm In the present embodiment, r ₁₃ and r ₁₄ are the gradient index lens (10), and 2 mm from the spherical vertex of the 13th surface to the image plane side.
It has a refractive index gradient from the offset point. The coefficient representing the refractive index gradient is, for example, as shown below.

N ₀₀ = 1.6512, N ₀₁ = 1.66 × 10 ~
² , N ₀₂ = -3.28 x 10 to ³ N ₀₃ = 4.76 x 10 to ⁴ , N ₀₄ = 3.16 x 10 to ⁴ , N ₀₅ = -9.8
0 × 10 to ^{5 Further} , in this embodiment, the lens surface having a radius of curvature marked with * is an aspherical surface, and the shape is expressed by the aspherical surface coefficient as in the following expression.

[0048]

Z ′ = C · Y ² / {1 + √ (1- (K + 1) · C ² · Y ² )}
+ A ₄ · Y ⁴ + A ₆ · Y ⁶ + A ₈ · Y ⁸ + A ₁₀ · Y ¹⁰ However, Z'is the distance from the tangent plane of the aspherical vertex of the point on the aspherical surface at the height Y from the optical axis, C Is the curvature of the reference spherical surface (1 / r), K is the conic constant, Y is the height from the optical axis, and A is
Reference symbols _{4 to} A ₁₀ denote aspherical coefficients of 4th to 10th orders, respectively.

The aspherical surface coefficients in the second embodiment are shown below.

13th surface: K = -1.4052, A ₄ = -1.2656 × 10
~ ⁴ , A ₆ = 4.1425 x 10 ~ ⁶ , A ₈ = -9.8185 x 10 ~ ⁸ , A ₁₀
= 9.4019 × 10 to ¹⁰ FIG. 6 is a characteristic diagram showing aberrations when the focal length is 9.5 mm when the shooting distance is ∞ in the second embodiment, and FIG.
Similarly, the figure is a characteristic diagram showing aberrations when the focal length is 52.3 mm. In addition, (a) shown in each characteristic diagram,
The symbols (b) and (c) have the same contents as in the case of the first embodiment.

In the second embodiment, the effect of the gradient index lens (10) and the aspherical surface provided on the lens has a synergistic effect on aberration correction, and the number of lenses is small and the structure is small. As shown in FIGS. 6 and 7, the aberration is well corrected.

Next, a third specific numerical example as shown in FIG. 5 will be shown. These are f = 9.5-52.1, F =
This is the case of the 1.8 zoom lens.

R ₁ = 52.05, d ₁ = 0.90, n ₁ = 1.8467, ν ₁ = 24 r ₂ = 27.89, d ₂ = 5.23, n ₂ = 1.5891, ν ₂ = 61 r ₃ = -90.34, d ₃ = 0.20 r ₄ = 23.54, d ₄ = 2.77, n ₃ = 1.5891, ν ₃ = 61 r ₅ = 50.30, d ₅ = variable _{r 6 = 18.91, d 6 =} 0.85, n 4 = 1.7432, ν 4 = 49 r 7 = 8.827, d 7 = 2.99 r 8 = -14.58, d _{8 = 0.85, n 5 = 1.7432} , ν 5 = 49 r 9 = 9.945, d 9 = 2.48, n 6 = 1.8467, ν 6 = 24 r 10 = 264.2, d ₁₀ = variable _{r 11 = -16.14, d 11 =} 0.85, n 7 = 1.7283, ν 7 = 28 r 12 = -75.06, d 12 = variable r ₁₃ = ∞ (stop), d ₁₃ = 0 _{50 r 14 * = 11.35, d} 14 = 5.00, n 8 = 1.6512, ν 8 = 33 r 15 = -59.38, d 15 = 2.03 r 16 = 23.44, d 16 = 2.00, n ₉ = 1.8052, ν ₉ = 25 r ₁₇ = 10.21, d ₁₇ = 1.57 r ₁₈ = 21.22, d ₁₈ = 4.00, n ₁₀ = 1.7130, v ₁₀ = 54 r ₁₉ = -20.61, d ₁₉ = 3.50 r ₂₀ = ∞, d ₂₀ = 4.00 r ₂₁ = ∞, d ₂₁ = 6.00, n ₁₁ = 1.5168, v ₁₁ = 64 r ₂₂ = ∞ Each symbol has the same content as in the first embodiment.

The I-th lens group (1) to the III-th lens group (3) are the same as those in the first embodiment, and r _{13 to} r ₁₉ are the IV lens group (4) and the IV lens group ( R ₁₃ included in 4) is a diaphragm (5), r ₂₀ is a shielding surface (6), and r _{21 to} r ₂₂
Is the radius of curvature of each lens surface that constitutes each of the crystal plates (7).

In the third embodiment, d ₅ , d ₁₀ ,
d ₁₂ varies depending on the focal length f, and an example is shown below.

When f = 9.5 mm: d ₅ = 0.59 mm, d
_{When 10} = 15.1 mm, d ₁₂ = 4.86 mm and f = 33.5 mm: d ₅ = 14.6 mm, d ₁₀ = 1.78 m
When m, d ₁₂ = 4.18 mm and f = 52.1 mm: d ₅ = 17.5 mm, d ₁₀ = 2.62 m
m, d ₁₂ = 0.50 mm In this embodiment, r ₁₄ and r ₁₅ are the gradient index lens (10), which are 2 mm from the spherical vertex of the 14th surface to the image plane side.
It has a refractive index gradient from the offset point. The coefficient representing the refractive index gradient is, for example, as shown below.

N ₀₀ = 1.6512, N ₀₁ = 1.66 × 10 ~
² , N ₀₂ = -3.28 x 10 to ³ N ₀₃ = 4.76 x 10 to ⁴ , N ₀₄ = 3.16 x 10 to ⁴ , N ₀₅ = -9.8
0 × 10 to ⁵ The aspherical surface coefficient in the third embodiment is shown below.

14th surface: K = -1.3657, A ₄ = -1.2190 × 10
~ ⁴ , A ₆ = 4.1066 x 10 ~ ⁶ , A ₈ = -9.0798 x 10 ~ ⁸ , A ₁₀
= 7.8968 × 10 to ¹⁰ FIG. 8 is a characteristic diagram showing aberrations when the focal length is 9.5 mm when the shooting distance is ∞ in the third embodiment, and FIG.
Similarly, is a characteristic diagram showing aberrations when the focal length is 52.1 mm. In addition, (a) shown in each characteristic diagram,
The symbols (b) and (c) have the same contents as in the case of the first embodiment.

Also in the third embodiment, the action of the gradient index lens (10) and the aspherical surface provided on the lens has a synergistic effect on aberration correction, thereby reducing the number of lenses and reducing the size. Thus, as shown in FIGS. 8 and 9, the aberration is satisfactorily corrected.

Next, a fourth specific numerical example as shown in FIG. 10 will be shown. These are f = 9.7-53.7, F =
This is the case of the 1.8 zoom lens.

R ₁ = 52.05, d ₁ = 0.90, n ₁ = 1.8467, ν ₁ = 24 r ₂ = 27.89, d ₂ = 5.23, n ₂ = 1.5891, ν ₂ = 61 r ₃ = -90.34, d ₃ = 0.20 r ₄ = 23.54, d ₄ = 2.77, n ₃ = 1.5891, ν ₃ = 61 r ₅ = 50.30, d ₅ = variable _{r 6 = 18.91, d 6 =} 0.85, n 4 = 1.7432, ν 4 = 49 r 7 = 8.827, d 7 = 2.99 r 8 = -14.58, d _{8 = 0.85, n 5 = 1.7432} , ν 5 = 49 r 9 = 9.945, d 9 = 2.48, n 6 = 1.8467, ν 6 = 24 r 10 = 264.2, d ₁₀ = variable _{r 11 = -16.14, d 11 =} 0.85, n 7 = 1.7283, ν 7 = 28 r 12 = -75.06, d 12 = variable r ₁₃ * = 12.99, d ₁₃ = 3 .35, n ₈ = 1.6512, ν ₈ = 33 r ₁₄ = −19.18, d ₁₄ = 1.16 r ₁₅ = ∞ (diaphragm), d ₁₅ = 3.64 r ₁₆ = 54.32, d ₁₆ = 2.00, n ₉ = 1.8052, ν ₉ = 25 r ₁₇ = 10.03, d ₁₇ = 1.07 r ₁₈ = 15.23, d ₁₈ = 5.00, n ₁₀ = 1.6512 , Ν ₁₀ = 33 r ₁₉ = -18.57, d ₁₉ = 3.50 r ₂₀ = ∞, d ₂₀ = 4.00 r ₂₁ = ∞, d ₂₁ = 6.00, n ₁₁ = 1.5168, ν ₁₁ = 64 r ₂₂ = ∞ Each symbol has the same content as in the first embodiment.

The first lens group (1) to the third lens group (3) are the same as those in the first embodiment, and r _{13 to} r ₁₉ are the fourth lens group (4) and the fourth lens group (4). 4) r ₁₅ contained in the diaphragm (5), r ₂₀ shielding surface (6), r ₂₁ ~r ₂₂
Is the radius of curvature of each lens surface that constitutes each of the crystal plates (7).

In the fourth embodiment, d ₅ , d ₁₀ ,
d ₁₂ varies depending on the focal length f, and an example is shown below.

When f = 9.7 mm: d ₅ = 0.59 mm, d
₁₀ = 15.1 mm, d ₁₂ = 4.86 mm f = 34.5 mm: d ₅ = 14.6 mm, d ₁₀ = 1.78 m
When m, d ₁₂ = 4.18 mm and f = 53.7 mm: d ₅ = 17.5 mm, d ₁₀ = 2.62 m
m, d ₁₂ = 0.50 mm In the present embodiment, r ₁₈ and r ₁₉ are the gradient index lens (10), and 2 mm from the spherical apex of 18 surfaces to the image surface side.
It has a refractive index gradient from the offset point. The coefficient representing the refractive index gradient is, for example, as shown below.

N ₀₀ = 1.6512, N ₀₁ = -1.66 × 10 ~
² , N ₀₂ = 3.28 x 10 to ³ N ₀₃ = -4.76 x 10 to ⁴ , N ₀₄ = -3.16 x 10 to ⁴ , N ₀₅ = 9.8
0 × 10 to ⁵ The aspherical surface coefficient in the fourth embodiment is shown below.

13th surface: K = -0.9709, A ₄ = -8.6855 × 10
~ ⁵ , A ₆ = -2.0610 x 10 ~ ⁶ , A ₈ = 4.3637 x 10 ~ ⁸ , A ₁₀
= -2.7298 × 10 to ¹⁰ FIG. 11 is a characteristic diagram showing aberrations when the focal length is 9.7 mm and the focal length is 53.7 mm when the shooting distance is ∞ in the fourth embodiment. 9 is a characteristic diagram showing aberrations in FIG. The symbols (a), (b) and (c) shown in each characteristic diagram have the same contents as in the case of the first embodiment.

Also in the fourth embodiment, the action of the gradient index lens (10) and the aspherical surface provided on the lens has a synergistic effect on aberration correction, thereby reducing the number of lenses and downsizing. Thus, as shown in FIGS. 11 and 12, the aberration is satisfactorily corrected.

Next, FIG. 1 showing another embodiment according to the present invention.
A fifth specific numerical example of the lens system shown in FIG. This is f = 5.2-15.0, F = 2.0
This is the case with the zoom lens.

R ₁ = 57.88, d ₁ = 0.50, n ₁ = 1.6968, ν ₁ = 56 r ₂ = 4.092, d ₂ = 1.69 r ₃ = 16.44, d ₃ = 1.95, n ₂ = 1.8052, ν ₂ = 25 r ₄ * = 145.1, d ₄ = variable r ₅ = ∞ (aperture), d ₅ = 0.50 r ₆ = 6.134, d ₆ = 1.00, n ₃ = 1.8467, ν ₃ = 24 r ₇ = 5.121, d ₇ = 5.40, n ₄ = 1.6512, ν ₄ = 33 r ₈ * = -24.28 , D ₈ = variable r ₉ = ∞, d ₉ = 4.40, n ₅ = 1.5163, ν ₅ = 64 r ₁₀ = ∞ Each symbol has the same content as in the first embodiment.

R _{1 to} r ₄ represent the radii of curvature of the respective lens surfaces constituting the I-th lens group (1), and r _{5 to} r ₈ represent the first radius.
The radius of curvature of each lens surface forming the II lens group (2) is shown. R ₅ and r ₉ and r ₁₀ included in the II lens group (2) are the diaphragm (5) and the quartz plate (7), respectively. ), Is the radius of curvature of each lens surface constituting each of the above.

In the above fifth embodiment, d ₄ and d ₈ differ depending on the focal length f, and an example is shown below.

When f = 5.2 mm: d ₄ = 11.5 mm, d
_{When 8} = 3.00 mm f = 7.7 mm: d ₄ = 6.25 mm, d ₈ = 5.63 m
When m f = 15.0 mm: d ₄ = 1.00 mm, d ₈ = 13.2 m
m In this embodiment, r ₇ and r ₈ are the gradient index lens (10) having a gradient of refractive index from the spherical apex of the seven surfaces. The coefficient representing the refractive index gradient is, for example, as shown below.

N ₀₀ = 1.6861, N ₀₁ = 1.66 × 10 ~
² , N ₀₂ = 3.28 x 10 to ³ N ₀₃ = -4.76 x 10 to ⁴ , N ₀₄ = -3.16 x 10 to ⁴ , N ₀₅ = 9.8
0 × 10 to ⁵ The aspherical surface coefficients in the fifth embodiment are shown below.

[0074] 4 _{side: K = 1413.6, A 4 =} -1.1887 × 1
0 to ³ , A ₆ = 5.1169 × 10 to ⁵ , A ₈ = -6.7099 × 10 to ⁶ , A
₁₀ = 9.5313 x 10 to ⁸ 8 planes: K = -9.7 x 10 ¹⁴ , A ₄ = 1.8637 x 10 to ³ , A ₆ =-
_{^{1.2290 × 10 ~ 4, A 8}} = 4.3695 × 10 ~ 5, A 10 = -4.3622 ×
10 to ⁶ FIG. 15 is a characteristic diagram showing aberrations when the focal length is 5.2 mm and the focal length is 15.0 mm in the fifth embodiment, and FIG. 16 shows aberrations when the focal length is 15.0 mm. It is a characteristic diagram. The symbols (a), (b) and (c) shown in each characteristic diagram have the same contents as in the case of the first embodiment.

Also in the fifth embodiment, the action of the gradient index lens (10) and the aspherical surface provided on the lens has a synergistic effect on aberration correction, thereby reducing the number of lenses and downsizing. Thus, as shown in FIGS. 15 and 16, the aberration is satisfactorily corrected.

Next, a sixth concrete example of numerical values as shown in FIG. 14 will be shown. This is f = 5.2-15.0, F = 2.
This is the case of a 0 zoom lens.

R ₁ * = 12.02, d ₁ = 0.50, n ₁ = 1.6968, ν ₁ = 56 r ₂ * = 3.734, d ₂ = 1.69 r ₃ * = 65.67 , D ₃ = 1.95, n ₂ = 1.8052, ν ₂ = 25 r ₄ * = − 1676, d ₄ = variable r ₅ = ∞ (diaphragm), d ₅ = 0.50 r ₆ * = 5. 977, d ₆ = 7.40, n ₃ = 1.5074, ν ₃ = 60 r ₇ * = − 14.61, d ₇ = 2.00 r ₈ = ∞, d ₈ = variable r ₉ = ∞, d ₉ = 4.40, n ₄ = 1.5163, ν ₄ = 64 r ₁₀ = ∞ Each symbol has the same content as in the first embodiment.

R _{1 to} r ₄ are the radii of curvature of the respective lens surfaces constituting the I-th lens group (11), and r _{5 to} r ₇ are the II-th lenses.
The radius of curvature of each lens surface constituting the lens group (12) is shown. R ₅ and r ₈ included in the second lens group (12) are a diaphragm (5), a shielding surface (6), and r _{9 respectively.} , R ₁₀ are the radii of curvature of the respective lens surfaces constituting the quartz plate (7).

In the sixth embodiment, d ₄ and d ₈ differ depending on the focal length f, and an example is shown below.

When f = 5.2 mm: d ₄ = 11.5 mm, d ₈ = 0.96 mm f = 7.7 mm: d ₄ = 6.25 mm, d ₈ = 3.59 mm f = 15.0 mm When: d ₄ = 1.00 mm, d ₈ = 11.2 mm Further, in the present embodiment, r ₆ and r ₇ are the gradient index lenses (10), and the gradient of the refractive index from the spherical vertices of the six surfaces is Have The coefficient representing the refractive index gradient is as shown below, for example.

N ₀₀ = 1.5891, N ₀₁ = -7.2 × 10 to ³ ,
N ₀₂ = -4.3 x 10 to ³ N ₀₃ = 7.4 x 10 to ³ , N ₀₄ = -4.1 x 10 to ³ , N ₀₅ = 7.9 x
10 to ⁴ The aspherical surface coefficients in the fifth embodiment are shown below.

[0082] 1 _{side: K = -4.0188, A 4 =} -6.8628 × 1
0 to ⁵ , A ₆ = -6.9655 × 10 to ⁶ , A ₈ = 8.7348 × 10 to ⁹ , A
₁₀ = 2.7436 × _10¯ ⁸ 2 ^{side: K = -7.4 × 10 ~ 2} , A 4 = 1.2726 × 10 ~ 4, A 6
= -2.2812 x 10 to ⁵ , A ₈ = -4.0654 x 10 to ⁶ , A ₁₀ = 3.92
22 × 10 ~ ⁷ 3 _{surfaces: K = -100.07, A 4 =} -1.3689 × 10 ~ 5, A 6 = -
_{^{2.7712 × 10 ~ 5, A 8}} = 1.7296 × 10 ~ 6, A 10 = -3.6453 ×
10 to ⁷ 4th surface: K = -2.4 × 10 ¹⁴ , A ₄ = -1.1177 × 10 to ³ , A ₆ =-
_{^{3.9476 × 10 ~ 5, A 8}} = 1.8978 × 10 ~ 6, A 10 = -4.1340 ×
^10-7 6 _{faces: K = -0.1347, A 4 =} -1.9945 × 10 ~ 4, A 6 = -
1.5303 x 10 to ⁶ , A ₈ = 2.4529 x 10 to ⁷ , A ₁₀ = 7.3280 x
^10-9 seventh _{surface: K = -24.036, A 4 =} 8.3944 × 10 ~ 4, A 6 = -
_{^{1.4317 × 10 ~ 4, A 8}} = 2.5342 × 10 ~ 5, A 10 = -8.9754 ×
10 to ⁷ are characteristic diagrams showing aberrations when the focal length is 5.2 mm and the focal length is 15.0 mm in the sixth embodiment, and FIG. 18 shows aberrations when the focal length is 15.0 mm. It is a characteristic diagram. The symbols (a), (b) and (c) shown in each characteristic diagram have the same contents as in the case of the first embodiment.

In the sixth embodiment as well, the action of the gradient index lens (10) and the aspherical surface provided on the lens has a synergistic effect on aberration correction, thereby reducing the number of lenses and downsizing. Therefore, as shown in FIGS. 17 and 18, the aberration is corrected well.

The aspherical surface in the above embodiment is formed by a glass lens directly, but as shown in FIG. 19, a normal lens or a refractive index distribution type glass material (15) is used. It goes without saying that an aspherical surface may be formed on the lens by using a synthetic resin material (14) or the like.

[0085]

As described above, according to the present invention, it is possible to provide a compact zoom lens which has a small number of lenses, is compact, and has excellent aberrations.

[Brief description of drawings]

FIG. 1 is a sectional view showing a configuration of a zoom lens of the present invention.

FIG. 2 is a characteristic diagram showing aberrations in the first numerical example of the present invention.

FIG. 3 is a characteristic diagram similarly showing aberration.

FIG. 4 is a sectional view showing a configuration of a second exemplary embodiment of the present invention.

FIG. 5 is a sectional view showing a configuration of a third exemplary embodiment of the present invention.

FIG. 6 is a characteristic diagram showing aberrations in the second numerical example of the present invention.

FIG. 7 is a characteristic diagram similarly showing aberration.

FIG. 8 is a characteristic diagram showing aberrations in the third numerical example of the present invention.

FIG. 9 is a characteristic diagram similarly showing aberration.

FIG. 10 is a sectional view showing a configuration of a fourth exemplary embodiment of the present invention.

FIG. 11 is a characteristic diagram showing aberrations in the fourth numerical example of the present invention.

FIG. 12 is a characteristic diagram similarly showing aberration.

FIG. 13 is a sectional view showing the configuration of the fifth exemplary embodiment of the present invention.

FIG. 14 is a sectional view showing the configuration of a sixth exemplary embodiment of the present invention.

FIG. 15 is a characteristic diagram showing aberrations in the fifth numerical example of the present invention.

FIG. 16 is a characteristic diagram similarly showing aberration.

FIG. 17 is a characteristic diagram showing aberrations in the sixth numerical example of the present invention.

FIG. 18 is a characteristic diagram similarly showing aberration.

FIG. 19 is a sectional view showing an essential part of an embodiment of the present invention.

FIG. 20 is a principle view showing an essential part of one embodiment of the present invention.

[Explanation of symbols]

1 ... I lens group, 2 ... II lens group, 3 ... III lens group, 4 ... IV lens group, 5 ... Aperture, 6 ... Shielding surface, 7 ...
Crystal plate, 8 ... Image plane, 9 ... Optical axis, 10 ... Gradient index type lens.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Taishi Yamazaki 292 Yoshida-cho, Totsuka-ku, Yokohama Hitachi, Ltd. Video Media Research Laboratory (72) Inventor Takesuke Maruyama 292 Yoshida-cho, Totsuka-ku, Yokohama Hitachi, Ltd. Visual Media Research Center

Claims (11)

[Claims] 1. A zoom lens comprising two or more lens groups, wherein zooming is performed by changing the axial distance of at least two lens groups of the lens groups, and a refractive index having a refractive index gradient in the optical axis direction. A zoom lens comprising at least one distributed lens. 2. The zoom lens according to claim 1, wherein the gradient index lens has an absolute value of a difference between a maximum refractive index and a minimum refractive index of 0.01 or less in the lens. lens. 3. The zoom lens according to claim 1, wherein the gradient index lens is provided near a diaphragm or in a lens group including the diaphragm. 4. An I-th lens group (1) having a positive refractive power.
And a second lens group II each having a negative refracting power and exhibiting a zooming effect by simultaneously moving relative to each other along the optical axis (9) while keeping the image plane (8) at a constant position. (2) and a third lens group, and a fourth lens group (4) having a positive refracting power and exhibiting an image forming action are arranged in this order from the object side. 4. The zoom lens according to claim 1, 2 or 3, characterized in that a gradient index lens having a refractive index gradient in the optical axis direction is provided in 4). 5. The zoom lens according to claim 4, wherein the fourth lens group (4) has a lens having a positive refractive power, a lens having a negative refractive power, and a lens having a positive refractive power. A zoom lens comprising a lens group having a negative refracting power and a lens having a positive refracting power arranged in order from the object side. 6. The zoom lens according to claim 4, wherein the IV lens group (4) includes a lens having a positive refracting power, a lens having a negative refracting power, and a lens having a positive refracting power. A zoom lens, wherein the zoom lens is a group of lenses arranged in order from the object side. 7. A first lens group (11) having a negative refracting power and exhibiting a zooming action by simultaneously moving relative to each other along the optical axis (9), and a first refracting power group. A zoom lens comprising a II lens group (12) arranged in order from the object side, wherein the second lens group (12) is provided with a gradient index lens having a gradient of refractive index in the optical axis direction. The zoom lens according to claim 1, claim 2, or claim 3. 8. The zoom lens according to claim 7, wherein a lens having a negative refractive power, a lens having a positive refractive power, a lens having a negative refractive power, and a lens having a positive refractive power are provided. A zoom lens characterized by being arranged in order from the object side. 9. The zoom lens according to claim 7, wherein a lens having a negative refracting power, a lens having a positive refracting power, and a lens having a positive refracting power are arranged in order from the object side. A zoom lens featuring. 10. The zoom lens according to claim 1, further comprising a lens having at least one aspherical surface. 11. The zoom lens according to claim 10, further comprising a gradient index lens having at least one aspherical surface.