JP2000227548A - Zoom lens - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To fully exploit the potential performance of a four-unit zoom lens and to solve the problem of manufacturing each component accompanying the increase in the zoom ratio. SOLUTION: In a multi-group zoom lens 1 having a plurality of lens groups, a first lens group GRI located closest to the object side is replaced with a first lens of a concave meniscus lens having a convex surface facing the object side in order from the object side. It is composed of a cemented lens of L1 and a second lens L2 of a convex lens, and a third lens L3 of a convex meniscus lens having a convex surface facing the object side, and a glass material having a wear degree of 300 or more is used as a material of the second lens. A thin layer of resin was formed on one surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention mainly relates to an increase in the magnification of a zoom lens of a consumer video camera, that is, a zoom ratio of 50 even though this is the most common zoom system.
The present invention relates to a technique for providing a zoom lens that achieves an ultra-high magnification of about twice and has a brightness of about F1.8 at the wide-angle end and is excellent in correcting various aberrations throughout the zoom range.

[0002]

2. Description of the Related Art A conventional zoom lens of a consumer video camera has a positive, negative, positive, and positive refractive power arrangement in order from the object side, as described in, for example, Japanese Patent Publication No. 2746155. Group configuration is common, and the third
By devising the configuration of the lens group and the fourth lens group and by utilizing an aspheric surface, functions such as high magnification and miniaturization have been improved.

However, achieving high magnification and downsizing of a zoom lens at the same time largely depends on downsizing of an image pickup device.

[0004] That is, at the time of manufacturing each component of the zoom lens, the required accuracy could not be obtained because the above components had to be made large before. A high-magnification zoom lens can be designed with the same size as the conventional image pickup device, and the size of each of the above components can be relatively reduced. This is because lenses that were not used become practical.

[0005] The applicant of the present application filed Japanese Patent Application No.
No. 84 provides a five-group zoom lens having a positive, negative, positive, negative, and positive refractive power arrangement in order from the object side, realizing a zoom ratio of about 50 times with a screen diagonal length of 3 mm.

The zoom lens having the five-group configuration has an effect that the front lens diameter can be reduced in spite of the large zoom ratio. It was convenient to attach it to.

Another feature is that the ability to darken the F-number at the telephoto end is one of the means for correcting spherical aberration and chromatic aberration.

However, the zoom lens having the five-group configuration has the following problems.

That is, if the F-number at the telephoto end is darkened, it may be too dark to be a practical obstacle.
Since the lens system has a five-group configuration, the number of constituent lenses inevitably increases, and there is a problem that the cost is high as a consumer zoom lens.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and has the following drawbacks: fully exploiting the potential performance of a four-unit zoom lens and manufacturing the components with a higher zoom ratio. It is an object to solve the above.

[0011]

In order to solve the above problems, a zoom lens according to the present invention has the following arrangement.

The first one is a multi-lens zoom lens having a plurality of lens groups, wherein the first lens group located closest to the object side is a concave meniscus lens having a convex surface facing the object side in order from the object side. It is composed of a cemented lens of the first lens and the second lens of the convex lens and a third lens of a convex meniscus lens having a convex surface facing the object side, and a glass material having a degree of wear of 300 or more is used as a material of the second lens. A thin layer of resin is formed on one surface.

Therefore, the second lens, which is a convex lens, is manufactured at low cost with a glass material having a high degree of wear, and the surface with poor surface accuracy caused by using the glass material with a high degree of wear is corrected by a thin layer of resin. Since the required surface accuracy is obtained, it is possible to reduce the manufacturing cost of the zoom lens.

According to a second aspect of the present invention, there is provided a zoom lens having a multi-group configuration having a plurality of lens groups, wherein the first lens group located closest to the object side is sequentially convexed toward the object side from the object side. The first lens of the concave meniscus lens and the third lens of the meniscus lens having a convex surface facing the object side are formed of a third lens having a wear degree of 300 or more. A thin layer of resin is formed on at least one surface of a glass material.

Therefore, the third lens, which is a meniscus lens having a convex surface facing the object side, is manufactured at low cost from a glass material having a high degree of wear, and the surface having poor surface accuracy caused by using the glass material having a high degree of wear is removed. Since the required surface accuracy is obtained by correcting with a thin layer, the manufacturing cost of the zoom lens can be reduced.

Further, a third zoom lens according to the present invention comprises, in order from the object side, a first fixed zoom lens which has a positive refractive power and is always fixed.
A lens group, a second lens group having a negative refractive power and movable mainly for zooming, a third lens group having a positive refractive power and always fixed, and a positive refractive power. Then, in the zoom lens constituted by a fourth lens group movable for correction of the focal position by zooming and focusing, the first lens group is formed of a concave meniscus lens having a convex surface facing the object side in order from the object side. 1st lens and 2nd of convex lens
The second lens group includes a cemented lens with a lens and a third lens of a convex meniscus lens having a convex surface facing the object side. The second lens group includes a fourth lens of a concave meniscus lens having a convex surface facing the object side in order from the object side. The third lens group is constituted by a cemented lens of the seventh lens of the convex lens and the eighth lens of the concave lens in order from the object side, and the third lens group is constituted by a cemented lens of the fifth lens of the concave lens and the sixth lens of the convex lens,
The fourth lens group is constituted by a cemented lens of the ninth lens of the concave meniscus lens and the tenth lens of the convex lens, and the eleventh lens of the convex lens, in order from the object side to the convex side, and constitutes the first lens group. At least one surface of each lens is formed by an aspheric surface, and the surface formed by the aspheric surface has an aspheric shape in which the effective diameter is shallower than the depth of the paraxial spherical surface in the case of a convex surface, and in the case of a concave surface, Is an aspherical shape whose effective diameter is deeper than the depth of the paraxial spherical surface.

Accordingly, a zoom lens having an ultra-high magnification and a practical size and having a sufficiently high image quality for use in a consumer video camera by making the most of the advantages of a small-sized image sensor. Can be provided.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an outline of a zoom lens according to the present invention will be described.

(1) In a multi-group zoom lens having a plurality of lens groups, the first lens group GRI located closest to the object side is replaced with the first meniscus lens of a concave meniscus lens whose convex surface faces the object side in order from the object side. A second lens L3 composed of a cemented lens of the lens L1 and a second convex lens L2 and a third convex meniscus lens L3 having a convex surface facing the object side;
Using a glass material having a wear degree of 300 or more for the material of the lens L2,
It is characterized in that a thin layer of resin is formed on at least one surface thereof.

(2) In a multi-unit zoom lens having a plurality of lens groups, the first lens group GRI located closest to the object side is replaced with a first meniscus lens of a concave meniscus lens whose convex surface faces the object side in order from the object side. A third lens L3 of a convex meniscus lens having a cemented lens of the lens L1 and the second convex lens L2 and a convex meniscus lens having a convex surface facing the object side;
Using a glass material having a wear degree of 300 or more for the material of the lens L3,
It is characterized in that a thin layer of resin is formed on at least one surface thereof.

The configurations of the above (1) and (2) are, for example,
When an ultra-high-magnification zoom lens having a zoom ratio of about 50 is to be designed in a small size, the manufacturing cost of a glass material used for the convex lens of the first lens group GRI having a positive refractive index as a whole on the most object side is reduced. It is about means.

That is, in order to effectively correct the secondary spectrum on the telephoto side, at least one convex lens is composed of an ultra-low dispersion glass or an abnormal partial Strongly low dispersion glass must be used, but these anomalous dispersion glasses have a high abrasion degree of 300 or more and must be carefully finished by a skilled technician to obtain good surface accuracy. . In addition, there is a difficulty in processing such that the surface is soft and easily scratched, for example, easily scratched by a bell chuck in a centering process. The degree of wear is measured by a measuring method based on the Japan Optical Glass Industrial Standards (JOGIS).

On the other hand, the lens of a consumer video camera is
There has been a history of low cost manufacturing by workers who do not have a high-speed polishing machine or skilled skills, which has contributed to lowering the lens manufacturing cost and reducing the overall cost of the video camera.

However, if the above-described glass material having a high degree of wear is processed by the above-described method, the required surface accuracy cannot be obtained.
This results in deterioration of the imaging performance on the telephoto side and poor so-called drop due to latent damage.

Therefore, the present invention has a high degree of wear (30
0 or more) Using a glass material, an inexpensive lens is manufactured by an operator who does not have a high-speed polishing machine or skilled skills, and a thin layer of resin is formed on the surface of a spherical surface with poor surface accuracy, and the surface of the resin layer Accuracy is ensured by transferring the surface of the mold with high accuracy, so that the same effect as when the glass lens is polished with high accuracy is obtained.

(3) In order from the object side, a first lens group GRI having a positive refractive power and always fixed, and a first lens group GRI having a negative refractive power,
Second lens group GRII movable mainly for zooming
And a third lens group GRII having a positive refractive power and constantly fixed
In a zoom lens having a positive refractive power and a fourth lens group GRIV having a positive refractive power and movable for correction of focusing position and focusing by zooming,
The first lens L1 of the concave meniscus lens whose convex surface faces the object side in order from the object side and the cemented lens of the second lens L2 of the convex lens, and the third lens of the convex meniscus lens whose convex surface faces the object side. The second lens group GRII is composed of a fourth lens L4 of a concave meniscus lens having a convex surface facing the object side in order from the object side, a fifth lens L5 of a biconcave lens, and a sixth lens L6 of a convex lens. The third lens group GRIII is constituted by a cemented lens of a seventh lens L7 of a convex lens and an eighth lens L8 of a concave lens in order from the object side, and the fourth lens group GRIV is sequentially arranged on the object side from the object side. It is composed of a cemented lens of a ninth lens L9 of a concave meniscus lens with a convex surface and a tenth lens L10 of a convex lens and an eleventh lens L11 of a convex lens. At least one surface of each lens constituting the first lens group GRI is formed by an aspheric surface, and when the surface formed by the aspheric surface is a convex surface, the effective diameter of the aspheric surface becomes shallower than the depth of the paraxial spherical surface. In the case of a concave surface, it is characterized in that it has an aspherical shape in which the effective diameter is deeper than the depth of the paraxial spherical surface in the effective diameter.

(4) The first lens group GRI is characterized in that the aspherical surface is a compound aspherical surface in which a thin layer of resin is formed on the surface of the spherical surface.

(5) By adapting the radius of curvature of the glass spherical surface forming the compound aspherical surface of the first lens group GRI to the aspherical shape, the distribution of the thickness of the resin layer monotonically increases or monotonically within the effective diameter. It is characterized by approaching uniformity without decreasing.

(6) The second lens constituting the first lens group GRI
The material of at least one of the lens L2 and the third lens L3 has an Abbe number of 80 or more.

(7) The second lens L of the first lens group GRI
The material No. 2 has an Abbe number of 80 or more, and its image-side surface is composed of a composite aspherical surface.

(8) The second lens L of the first lens group GRI
It is characterized in that the Abbe number of the material of the second and third lenses L2 is set to 80 or more, and a thin layer of resin is formed on at least one surface of the third lens L3.

(9) The object-side surface of the seventh lens L7 of the third lens group GRIII is formed by an aspherical surface.
The image-side surfaces of the tenth lens L10 of the lens group GRIV are made up of aspherical surfaces, and these surfaces have an aspherical shape whose effective diameter is smaller than the depth of the paraxial spherical surface.

(10) The third lens unit and the fourth lens unit satisfy the following conditions. −0.018 <1 / νIII <0.018 (conditional expression 1) −0.005 <1 / νIV <0.005 (conditional expression 2) where νIII is the equivalent Abbe number of the third lens group GRIII, ν
IV: The equivalent Abbe number of the fourth lens group GRIV.

Incidentally, the equivalent Abbe number νIII of the third lens group GRIII is a convenient composite focal length calculated by using the third lens group GRIII as a thin-walled close contact system, fIII, the seventh lens L8
And the focal length and Abbe number of the eighth lens L9 are respectively f
7, f8, ν7, ν8, 1 / fIII = 1 / f
7 + 1 / f8 and 1 / fIII · νIII = 1 / f7 · ν7 +
1 / f8 · ν8 is a value obtained by replacing the lens with a thin single lens for convenience. Similarly, the equivalent Abbe number νIV of the fourth lens group GRIV is calculated by assuming the fourth lens group GRIII as a thin-walled close contact system. A convenient combined focal length is fIV, a ninth lens L9, a tenth lens L10, and an eleventh lens L11.
The focal length and Abbe number of f9, f10, f1, respectively
Assuming that 1, ν9, ν10, f11, 1 / fIV = 1 /
f9 + 1 / f10 + 1 / f11 and 1 / fIV · νIV = 1
/F9.v9+1/f10.v10+1/f11.v1
This is a value obtained from 1 and conveniently replaced with a thin single lens.

The configurations (3) to (10) specifically show the configuration of each lens group so that the latent performance of the four-unit zoom lens is adapted to increase the zoom ratio. .

The first lens group GRI and the second lens group GRII
Has a structure which has been conventionally used as a lens type, but glass having anomalous dispersion was used for the convex lens of the first lens group GRI.

In order to correct spherical aberration mainly on the telephoto side, at least one of the lenses constituting the first lens group GRI needs to be aspherical. This is because, when the surfaces of the lenses constituting the first lens group GRI are formed only of spherical surfaces, it is inevitable that factors specific to the underside of the spherical aberration remain.

The second lens group GRII is connected to the first lens group GR.
In order to correct the spherical aberration generated from I, a specific factor is provided on the over side.

Incidentally, the spherical aberration generated from the lens group is determined by the relationship between the factors specific to each lens group and the height of the light ray that enters parallel to the optical axis and passes through the principal plane of the lens group. There is a property that determines the effect on the amount of spherical aberration of the system.

At the wide-angle end, since the light beam determined by the F-number is narrow, the spherical aberration generated from the first lens group GRI and the second lens group GRII has little effect on the entire lens system, and the zooming on the telephoto side is performed. As you go, the first
The height of light rays incident on the lens group GRI increases and the amount of occurrence of spherical aberration on the under side increases, but the second lens group GR
Since the ray height at II also increases in proportion to this, the amount of occurrence of spherical aberration on the over side also increases, and the first lens group GR
The balance between the cancellation of the spherical aberration between the lens unit I and the second lens unit GRII is balanced, and a favorable correction situation is maintained for the entire lens system.

However, when zooming further to the telephoto side and the incident light beam is restricted by the aperture diameter of the first lens group GRI and the F-number becomes extremely dark, the height of the light ray incident on the second lens group GRII decreases. In spite of the condition that the residual spherical aberration of the first lens group GRI is maximized,
The spherical aberration on the second lens group GRII over side is reduced, the spherical aberration of the entire lens system remains largely on the under side, and this cannot be corrected by the lens groups subsequent to the second lens group GRII. .

By the way, the applicant of the present application has proposed in the above-mentioned 1997 Patent Application No. 236384 that the reason why the spherical aberration remains on the under side on the telephoto side and as a solution therefor is to provide an aspherical surface in the first lens group. Provided a means to use.

Therefore, in the zoom lens of the present invention,
The configuration of the lens system has changed from the above-mentioned five-group system to the four-group system. However, if the above causes and countermeasures are applied as they are, the lens will have a higher zoom ratio and a smaller size as a consumer video camera lens. And a good and economical means of simultaneously achieving good review correction.

In the present invention, since the first lens group GRI has an aspherical surface, since the effective diameter of the lens is large and the anomalous dispersion glass is not suitable for a mold manufacturing method, the surface of the spherical surface formed by polishing has a complex non-spherical surface. It is realistic to form a spherical film.

When the large residual spherical aberration on the telephoto side is corrected by the compound aspherical surface, the burden on the aspherical surface for correcting the aberration is large, and the fluctuation of the aberration is too sensitive to the deviation from the designed shape of the aspherical surface. Become. The composite aspherical film has a thickness of 0.1
Since it is a thin resin layer of about mm, the shape change is generally considered to be negligible with respect to temperature change,
If it is too sensitive to aberration fluctuations, slight changes in shape due to temperature changes cannot be ignored.

Since the amount of aspherical surface as a deviation from the paraxial spherical surface is necessary for aberration correction, it is not possible to make the surface shape sensitive to a change in aberration due to a temperature change. However, it is possible to make the shape close to a similar shape by making the shape change due to the temperature change uniform.

The refractive index of the anomalous dispersion glass is 1.4.
The refractive index of the aspherical resin forming the resin layer is about 1.
When it is set to about 53, since the refractive power of the spherical surface of the anomalous dispersion glass to which the aspherical resin is attached is very weak, it can be used as a degree of freedom for making the thickness of the resin layer uniform. That is, by setting the radius of curvature of the spherical surface that fits averagely to the aspheric surface of the resin surface, and adjusting the spherical surface of the anomalous dispersion glass to the radius of curvature, the resin layer does not monotonically increase nor decrease monotonically. It can be made uniform.

The extraordinarily dispersible glass is (ng-n
F) is a graph represented by the value defined by (Nf-nC) and the Abbe number, which is greatly deviated from the straight line connecting C7 and F2. In the present invention, the abnormal partial dispersion and the low Since it is important to have both dispersibility and glass, an Abbe number of 80 or more glass is used as the second lens L2 which is a convex lens.
Alternatively, it is used for the third lens L3.

Third lens group GRIII and fourth lens group GRI
V is mainly for correcting various aberrations from the wide-angle end to the intermediate focal region. As a lens system suitable for such good aberration correction, there is a zoom lens described in Japanese Patent Publication No. 2777480. The basic lens arrangement and shape of the present invention are similar to the zoom lens described in the above publication.

However, the zoom lens described in the above publication has a zoom ratio of about 8 times,
In order to obtain good aberration correction at a zoom ratio of about 50 times, various aberrations are improved by changing or adding components of the present invention, and insensitivity to errors in component accuracy and assembly accuracy is reduced. It is necessary to improve the reproducibility of design performance at times.

For example, in the third lens group GRIII, if the convex lens and the concave lens are not joined, eccentricity occurs at the time of assembling, which causes one-sided blur. Therefore, in the present invention, these are used as cemented lenses, and centering is performed at the time of joining, so that stable performance can be obtained. The correction of spherical aberration and coma on the wide-angle side is
The improvement can be achieved by making the object-side surface of the seventh lens L7, which is a convex lens, an aspheric surface and a surface that functions to reduce the refracting power as the distance from the optical axis increases.

The fourth lens group GRIV includes a ninth lens L9 which is a concave lens and a tenth lens L1 which is a convex lens.
By making 0 a cemented lens, the performance during mass production is stabilized, and the image-side surface of the tenth lens L10 is made aspheric, so that the curvature of field and the fourth lens group GRIV mainly move. This has the function of suppressing the fluctuation of aberration due to the above.

Next, correction of chromatic aberration in the intermediate focal length range from the wide-angle end will be described.

To correct axial chromatic aberration, the third lens group GR
III and the fourth lens group GRIV have a large effect, and the fourth lens group GRIV has a large effect on correcting lateral chromatic aberration. In addition, since the fourth lens group GRIV moves with zooming and focusing, this causes variation in chromatic aberration.

The above conditional expression 1 defines conditions for achromaticity of the third lens group GRIII, and is intended to prevent chromatic aberration from being biased toward the fourth lens group GRIV.

That is, if the value of 1 / νIII exceeds the upper limit in conditional expression 1, the achromatic effect of the third lens group GRIII is weakened, and the achromatic effect of the fourth lens group GR4 is correspondingly enhanced. I have to help.

As a result, in the conditional expression 2 defining the condition for achromatism of the fourth lens group GRIV, 1 / ν
When the value of IV falls below the lower limit, the fourth lens group GR
The fluctuation of the axial chromatic aberration and the chromatic aberration of magnification accompanying the movement of the IV exceeds the allowable range, which is a drawback of the high-magnification zoom lens.

On the other hand, if the value of 1 / νIII in the conditional expression 1 exceeds the lower limit, the achromatic effect of the fourth lens group GRIV must be weakened in order to balance axial chromatic aberration. Accordingly, 1 / νIV in the conditional expression 2
When the value exceeds the upper limit, the chromatic aberration of magnification is mainly corrected by the fourth lens group GRIV.
In particular, it is difficult to correct lateral chromatic aberration when the fourth lens group GRIV moves toward the object side.

Next, numerical examples showing embodiments of the zoom lens of the present invention will be described with reference to the accompanying drawings.

First, common items will be described.

The zoom lens 1 includes, in order from the object side, a first lens group GRI having a positive refractive power and always fixed, and a second lens group having a negative refractive power and movable mainly for zooming. A group GRII, a third lens group GRIII having a positive refractive power and fixed at all times, and a fourth lens group GRIV having a positive refractive power and movable for correction of a focal position by zooming and focusing. And the first lens group GR
I is a first lens L1 of a concave meniscus lens having a convex surface facing the object side in order from the object side, and a second lens L2 of the convex lens
And a third lens L3 of a convex meniscus lens having a convex surface facing the object side, and a second lens group G
RII is constituted by a cemented lens of the fourth lens L4 of the concave meniscus lens and the fifth lens L5 of the biconcave lens and the sixth lens L6 of the convex lens, with the convex surface facing the object side in order from the object side, and the third lens group GRIII From the object side in order from the seventh lens L7 of the convex lens and the eighth lens L8 of the concave lens
And a fourth lens group GRIV,
It is composed of a cemented lens formed by a ninth lens L9 of a concave meniscus lens and a tenth lens L10 of a convex lens whose convex surface faces the object side in order from the object side, and an eleventh lens L11 of a convex lens.

In the zoom lens 1, the object-side surface of the second lens L2 of the first lens group GRI is a compound aspherical surface, and the object-side surface of the seventh lens L7 of the third lens group GRIII is non-aspheric. The fourth lens group GRIV has a spherical surface.
The image-side surface of the lens L10 is aspheric.

Further, the sixth lens L of the second lens group GRII
An aperture 2 is provided between the sixth lens 6 and the seventh lens L7 of the third lens group GRIII, and the eleventh lens of the fourth lens group GRIV and the image plane 3
The filter 4 is disposed between the two.

Hereinafter, numerical examples showing the details of the zoom lens of the present invention will be described.

In the following description, “i ′” is a suffix relating to the thin resin layer formed on the i-th surface counted from the object side, and [ri] is the suffix of the i-th surface counted from the object side. The radius of curvature, "di" is the surface distance between the i-th surface and the (i + 1) -th surface, "ni" is the refractive index at the d-line of the material constituting the i-th lens Li, and "νi" is the i-th lens Li Abbe number of the material to be processed, "fi" is the focal length of the i-th lens Li,
“FIII” is a convenient synthetic focal length calculated using the third lens group GRIII as a thin-walled close contact system, “fIV” is a convenient synthetic focal length calculated using the fourth lens group GRIV as a thin-walled close-contact system, and “νIII” The equivalent Abbe number of the three lens group GRIII,
“ΝIV” is the equivalent Abbe number of the fourth lens group GRIV.

The definition of the aspherical surface is as follows: When the depth of the aspherical surface is “xi” and the height from the optical axis is “H”, xi = H ² / ri ｛1+ (1−H ² / ri ² ) ^1/2 ｝ +｝
(Aj · jH ^j ). In each of the following tables showing aspheric coefficients, "e" indicates an exponential expression with base 10; for example, "e-3" is " ^10-3 ".
It is.

Table 1 and FIG. 2 show the numerical values of the zoom lens 1 according to Numerical Example 1 and the configuration of the first lens group GRI.

[0068]

[Table 1]

As shown in Table 1 above, the surface distances d5 and d1 are associated with the zooming and focusing of the zoom lens 1.
0, d14 and d19 are variable. Accordingly, Table 2 shows that the wide-angle end (f = 2.316) and the telephoto end (f = 1)
22.02) and an intermediate focal position (f) between the wide-angle end and the telephoto end.
= 40.131) indicates the respective numerical values of the above variable surface spacings.

[0070]

[Table 2]

Table 3 shows that the surfaces r3 ', r12, and r17 constituted by the aspheric surfaces have the fourth, sixth, eighth, and tenth order.
The following aspheric coefficients A4, A6, A8 and A10 are shown.

[0072]

[Table 3]

Table 4 shows numerical values related to the conditional expressions 1 and 2.

[0074]

[Table 4]

FIGS. 3 to 5 show spherical aberration, astigmatism, and distortion at the wide-angle end, an intermediate focal position between the wide-angle end and the telephoto end, and at the telephoto end, respectively.

In the spherical aberration diagram, the solid line shows the value on the d line, the broken line shows the value on the g line, and the dashed line shows the value on the C line. In the astigmatism diagram, the solid line shows the sagittal image plane and the broken line shows the meridional image. This shows the value on the surface (the same applies to the following numerical examples).

Table 5 and FIG. 6 show numerical values of the zoom lens 1A and the structure of the first lens group GRI according to Numerical Example 2.

[0078]

[Table 5]

As shown in Table 5, the zoom lens 1A
Surface spacing d5 with zooming and focusing of
d10, d14 and d19 are variable. Therefore, Table 6 shows that the wide-angle end (f = 2.304) and the telephoto end (f = 2.304)
122.22) and the numerical values of the above-mentioned variable surface intervals at the intermediate focal position (f = 40.552) between the wide-angle end and the telephoto end.

[0080]

[Table 6]

Table 7 shows that the surfaces r3 ', r12 and r17 constituted by aspherical surfaces have the fourth, sixth, eighth and tenth order.
The following aspheric coefficients A4, A6, A8 and A10 are shown.

[0082]

[Table 7]

Table 8 shows numerical values relating to the conditional expressions 1 and 2.

[0084]

[Table 8]

FIGS. 7 to 9 show the spherical aberration, astigmatism, and distortion at the wide-angle end, at the intermediate focal position between the wide-angle end and the telephoto end, and at the telephoto end, respectively.

Table 9 and FIG. 10 show the numerical values of the zoom lens 1B and the structure of the first lens group GRI according to Numerical Example 3.

[0087]

[Table 9]

As shown in Table 9 above, the surface distances d5 and d1 are associated with the drawing tool and focusing of the zoom lens 1.
0, d14 and d19 are variable. Therefore, Table 10 shows that the wide-angle end (f = 2.316) and the telephoto end (f =
122.02) and the numerical values of the above-mentioned variable surface distances at the intermediate focal position (f = 40.131) between the wide-angle end and the telephoto end.

[0089]

[Table 10]

Table 11 shows that the surfaces r3 ', r12, and r17 constituted by aspherical surfaces have the fourth, sixth, eighth, and first orders.
The 0th order aspherical coefficients A4, A6, A8 and A10 are shown.

[0091]

[Table 11]

Table 12 shows numerical values relating to the conditional expressions 1 and 2.

[0093]

[Table 12]

FIGS. 11 to 13 show the spherical aberration, astigmatism, and distortion at the wide-angle end, at the intermediate focal position between the wide-angle end and the telephoto end, and at the telephoto end, respectively.

As described above, according to the present invention,
Conventionally, by simply adding a new component to a general four-group zoom lens, the effect of the miniaturized imaging device is maximized to achieve a very high zoom ratio, a practical size and It is possible to provide a zoom lens that simultaneously achieves a sufficiently high image quality for use in a consumer video camera.

Further, a combination of the above-mentioned components makes it possible to obtain a zoom lens which is also excellent in workability of the lens.

Incidentally, the specific shapes and structures of the respective parts shown in the above-described embodiment are merely examples for embodying the present invention, and the technical features of the present invention are thereby described. The scope should not be construed as limiting.

[0098]

As is apparent from the above description, the zoom lens of the present invention is a multi-lens zoom lens having a plurality of lens groups, in which the first lens group located closest to the object side is moved from the object side. The first lens of the concave meniscus lens having the convex surface facing the object side and the cemented lens of the second lens of the convex lens in order, and the third lens of the convex meniscus lens having the convex surface facing the object side are formed. Using a glass material with a wear degree of 300 or more, at least one of
Since a thin layer of resin is formed on the surface of the surface, the second lens, which is a convex lens, is manufactured at a low cost with a glass material having a high degree of wear, and the surface with poor surface accuracy caused by using a glass material with a high degree of wear is formed of a resin. Since the required surface accuracy is obtained by performing the correction using the thin layer, the manufacturing cost of the zoom lens can be reduced.

According to the second aspect of the present invention, in a zoom lens having a multi-group configuration having a plurality of lens groups,
The first lens group located closest to the object side is a cemented lens of the first lens of the concave meniscus lens having a convex surface facing the object side in order from the object side and the meniscus lens having the convex surface facing the object side. Since the third lens is made of a glass material having a degree of wear of 300 or more and a thin layer of resin is formed on at least one surface of the third lens, a meniscus lens having a convex surface facing the object side is used. A third lens is manufactured at a low cost using a glass material having a high degree of wear, and a surface having a poor surface accuracy caused by using a glass material having a high degree of wear is corrected by a thin layer of resin to obtain a necessary surface accuracy. Therefore, the manufacturing cost of the zoom lens can be reduced.

According to the third aspect of the present invention, in order from the object side, a first lens group having a positive refractive power and always fixed, and a first lens group having a negative refractive power and mainly for zooming are provided. A movable second lens group, and a constantly fixed third lens group having a positive refractive power.
In a zoom lens constituted by a lens group and a fourth lens group having a positive refractive power and movable for correction of a focal position by zooming and focusing,
The lens group is composed of a cemented lens of the first lens of the concave meniscus lens having a convex surface facing the object side and the third lens of a convex meniscus lens having a convex surface facing the object side in order from the object side. The second lens group is composed of a fourth lens of a concave meniscus lens having a convex surface facing the object side in order from the object side, and a cemented lens of a fifth lens of a biconcave lens and a sixth lens of the convex lens, and a third lens group Is composed of a cemented lens composed of a seventh lens of a convex lens and an eighth lens of a concave lens in order from the object side, and the fourth lens group is composed of a ninth lens of a concave meniscus lens having a convex surface facing the object side in order from the object side. It is composed of a cemented lens with the tenth lens of the convex lens and an eleventh lens of the convex lens, and at least one surface of each lens constituting the first lens group is an aspheric surface. The surface constituted by the aspherical surface has an aspherical shape that is shallower than the depth of the paraxial spherical surface in the effective diameter in the case of a convex surface, and is deeper than the depth of the paraxial spherical surface in the effective diameter in the case of a concave surface. Aspherical shape, making the most of the advantages of a small image sensor,
It is possible to provide a zoom lens having an ultra-high magnification and a practical size, and having a sufficiently high image quality for use in a consumer video camera.

In the invention described in claim 4, the aspherical surface is a complex aspherical surface formed by forming a thin layer of resin on the spherical surface, so that the lens surface has an aspherical shape. It can be configured with high accuracy and at low cost.

According to the fifth aspect of the present invention, by adjusting the radius of curvature of the glass spherical surface forming the composite aspherical surface to the aspherical shape, the distribution of the thickness of the resin layer is monotonous within the effective diameter. Since the uniformity is approached without increasing or monotonously decreasing, it is possible to effectively suppress the fluctuation of various aberrations caused by the change in the shape of the lens surface due to the temperature change.

In the invention according to claim 6, the first aspect
Since the Abbe number of the material of at least one of the second lens and the third lens constituting the lens group is set to 80 or more, it is possible to use a glass material having both abnormal partial dispersion and low dispersion. become able to.

Further, in the present invention, the Abbe number of the material of the second lens of the first lens group is set to 80 or more, and a thin resin layer is formed on the spherical surface. , The second lens can be made of a glass material having both an abnormal partial dispersion and a low dispersion, and the accuracy of the lens surface can be improved. become.

According to the tenth to sixteenth aspects of the present invention, the Abbe number of the material of the second lens and the third lens of the first lens group is set to 80 or more, and at least one of the third lens is used. Since a thin layer of resin is formed on the surface, the second lens and the third lens can be made of a glass material having both an abnormal partial dispersibility and a low dispersibility, and the accuracy of the lens surfaces is improved. Can be improved.

According to the seventeenth aspect of the present invention, the object-side surface of the seventh lens of the third lens group is formed by an aspherical surface, and the image-side surface of the tenth lens of the fourth lens group is non-spherical. Since these surfaces are composed of spherical surfaces and these surfaces have an aspheric shape that is shallower than the depth of the paraxial spherical surface in effective diameter,
Spherical aberration and coma on the wide-angle side can be favorably corrected, and correction of curvature of field and suppression of variations in various aberrations caused by movement of the fourth lens group can be effectively performed. Become like

According to the eighteenth aspect of the present invention, in the third lens group and the fourth lens group, νIII is an equivalent Abbe number of the third lens group, and νIV is an equivalent Abbe number of the fourth lens group. , −0.018 <1 / νIII <0.018 and −0.005 <1 / νIV <0.005, so that the intermediate focal point between the wide-angle end and the telephoto end from the wide-angle end. Various aberrations at the position can be corrected well.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a basic configuration according to an embodiment of a zoom lens of the present invention.

FIG. 2 shows Numerical Example 1 of the embodiment of the zoom lens according to the present invention, along with FIGS. 3 to 5, which is a view schematically showing a configuration of a first lens group.

FIG. 3 is a diagram illustrating spherical aberration, astigmatism, and distortion at a wide-angle end.

FIG. 4 is a diagram illustrating spherical aberration, astigmatism, and distortion at an intermediate focal position between a wide-angle end and a telephoto end.

FIG. 5 is a diagram showing spherical aberration, astigmatism, and distortion at the telephoto end.

6 shows Numerical Example 2 of the embodiment of the zoom lens of the present invention, together with FIGS. 7 to 9, and is a view schematically showing the configuration of the first lens group. FIG.

FIG. 7 is a diagram illustrating spherical aberration, astigmatism, and distortion at the wide-angle end.

FIG. 8 is a diagram illustrating spherical aberration, astigmatism, and distortion at an intermediate focal position between a wide-angle end and a telephoto end.

FIG. 9 is a diagram illustrating spherical aberration, astigmatism, and distortion at the telephoto end.

FIG. 10 shows Numerical Example 3 of the embodiment of the zoom lens of the present invention, together with FIGS. 11 to 13, and is a diagram schematically showing the configuration of the first lens group.

FIG. 11 is a diagram illustrating spherical aberration, astigmatism, and distortion at the wide-angle end.

FIG. 12 is a diagram illustrating spherical aberration, astigmatism, and distortion at an intermediate focal position between a wide-angle end and a telephoto end.

FIG. 13 is a diagram illustrating spherical aberration, astigmatism, and distortion at the telephoto end.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... zoom lens, 1A ... zoom lens, 1B ... zoom lens, GRI ... 1st lens group, GRII ... 2nd lens group, GRIII ... 3rd lens group, GRIV 4th lens group, L
1: 1st lens, L2: 2nd lens, L3: 3rd lens, L4: 4th lens, L5: 5th lens, L6: 6th
Lens, L7: Seventh lens, L8: Eighth lens, L9 ...
Ninth lens, L10: Tenth lens, L11: Eleventh lens

Claims (18)

[Claims] 1. A zoom lens having a multi-group configuration having a plurality of lens groups, wherein a first lens group located closest to the object side is a first meniscus lens having a concave meniscus lens having a convex surface facing the object side in order from the object side. It is composed of a cemented lens of the convex lens with the second lens and a third lens of a convex meniscus lens having a convex surface facing the object side, and a glass material having a wear degree of 300 or more is used as a material of the second lens.
A zoom lens having a thin resin layer formed on at least one surface thereof. 2. A zoom lens having a multi-group configuration having a plurality of lens groups, wherein a first lens group located closest to the object side is a first lens of a concave meniscus lens whose convex surface faces the object side in order from the object side. It is composed of a cemented lens of the convex lens with the second lens and a third lens of a convex meniscus lens having a convex surface facing the object side, and a glass material having a wear degree of 300 or more is used as a material of the third lens.
A zoom lens having a thin resin layer formed on at least one surface thereof. 3. A first lens group which has a positive refractive power and is always fixed, a second lens group which has a negative refractive power and is movable mainly for zooming, and A third lens group having a constant refractive power, and a fourth lens group having a positive refractive power and movable for correction of focusing position and focusing by zooming, The first lens group includes a first meniscus lens having a convex surface facing the object side in order from the object side, and a second lens having a convex meniscus lens.
The second lens group includes a cemented lens with a lens and a third lens of a convex meniscus lens having a convex surface facing the object side. The second lens group includes a fourth lens of a concave meniscus lens having a convex surface facing the object side in order from the object side. The third lens group is constituted by a cemented lens of a seventh lens of a convex lens and an eighth lens of a concave lens in order from the object side, and the third lens group is constituted by a cemented lens of a fifth lens of a biconcave lens and a sixth lens of a convex lens. The fourth lens group includes a ninth lens of a concave meniscus lens having a convex surface facing the object side in order from the object side and a first lens of a convex lens.
A lens composed of a cemented lens with a zero lens and an eleventh lens of a convex lens, at least one surface of each lens constituting the first lens group is composed of an aspheric surface, and the surface composed of the aspheric surface is a convex surface A zoom lens having an aspherical shape having a smaller effective surface diameter than the depth of the paraxial spherical surface, and a concave surface having an aspherical shape having a larger effective diameter than the paraxial spherical surface. 4. The zoom lens according to claim 3, wherein the aspherical surface is a composite aspherical surface formed by forming a thin layer of resin on the surface of the spherical surface. 5. The distribution of the thickness of the resin layer is uniform without becoming monotonically increasing or decreasing within the effective diameter by adapting the radius of curvature of the glass spherical surface forming the composite aspherical surface to the aspherical shape. 5. The apparatus according to claim 4, wherein the apparatus is approached.
A zoom lens according to claim 1. 6. The zoom lens according to claim 3, wherein at least one of the second lens and the third lens constituting the first lens group has an Abbe number of 80 or more. 7. The zoom lens according to claim 1, wherein the Abbe number of the material of the second lens of the first lens group is set to 80 or more, and the surface on the image side is formed by a compound aspherical surface. . 8. A composite lens comprising a second lens of the first lens group having an Abbe number of 80 or more, and having an image-side surface formed by forming a thin resin layer on a spherical surface. The zoom lens according to claim 3, wherein the zoom lens has a spherical surface. 9. A composite lens comprising a second lens of the first lens group having an Abbe number of 80 or more and having an image-side surface formed by forming a thin resin layer on a spherical surface. The zoom lens according to claim 4, wherein the zoom lens has a spherical surface. 10. The method according to claim 1, wherein the Abbe number of the material of the second lens and the third lens of the first lens group is 80 or more, and a thin layer of resin is formed on at least one surface of the third lens. The zoom lens according to claim 1. 11. The second lens and the third lens of the first lens group have an Abbe number of 80 or more, and a thin layer of resin is formed on at least one surface of the third lens. The zoom lens according to claim 2. 12. The method according to claim 1, wherein the Abbe number of the material of the second lens and the third lens of the first lens group is 80 or more, and a thin layer of resin is formed on at least one surface of the third lens. The zoom lens according to claim 3. 13. The method according to claim 1, wherein the Abbe number of the material of the second lens and the third lens of the first lens group is 80 or more, and a thin layer of resin is formed on at least one surface of the third lens. The zoom lens according to claim 6. 14. A method according to claim 1, wherein the Abbe number of the material of the second lens and the third lens of the first lens group is 80 or more, and a thin layer of resin is formed on at least one surface of the third lens. The zoom lens according to claim 7. 15. The method according to claim 1, wherein the Abbe number of the material of the second lens and the third lens of the first lens group is 80 or more, and a thin layer of resin is formed on at least one surface of the third lens. The zoom lens according to claim 8. 16. The material of the second lens and the third lens of the first lens group has an Abbe number of 80 or more, and a thin layer of resin is formed on at least one surface of the third lens. The zoom lens according to claim 9. 17. The object-side surface of the seventh lens of the third lens group is constituted by an aspherical surface, and the first lens of the fourth lens group is formed by an aspheric surface.
4. The zoom lens according to claim 3, wherein the image-side surfaces of the zero lens are formed of aspherical surfaces, and these surfaces have an aspherical shape whose effective diameter is smaller than the depth of the paraxial spherical surface. 18. The zoom lens according to claim 3, wherein the third lens group and the fourth lens group satisfy the following condition. −0.018 <1 / νIII <0.018 −0.005 <1 / νIV <0.005, where νIII: equivalent Abbe number of the third lens group, and νIV: equivalent Abbe number of the fourth lens group. .