JP5532405B2 - Zoom lens, camera, and portable information terminal device - Google Patents

Description

  The present invention relates to a zoom lens improved as a photographing optical system, a camera having the zoom lens as a photographing optical system, and a portable information terminal device.

In recent years, the market of digital cameras has become very large, and there are various demands for digital cameras by users. In particular, high image quality and miniaturization are always what users want, and the weight is great. Therefore, a zoom lens used as a photographing lens is also required to have both high performance and downsizing.
Here, in terms of miniaturization, it is first necessary to shorten the total lens length (distance from the lens surface closest to the object side to the image plane) during use, and reduce the thickness of each lens group. It is also important to reduce the overall length during storage. Furthermore, in terms of high performance, it is necessary to have at least a resolving power corresponding to an image sensor with 10 to 15 million pixels over the entire zoom range.
In addition, there are many users who desire a wide angle of view of the photographing lens, and it is desirable that the half angle of view at the wide angle end of the zoom lens is 38 degrees or more. The half angle of view of 38 degrees corresponds to 28 mm in terms of the focal length in terms of a 35 mm silver salt camera (so-called Leica version).
Furthermore, it is desired that the zoom ratio is as large as possible. A zoom lens equivalent to about 28 to 200 mm (about 7.1 times) with a focal length equivalent to a 35 mm silver salt camera is considered to be able to cope with most general photographing.

There are many types of zoom lenses for digital cameras, but as a type suitable for high zoom ratio, in order from the object side, a first lens group having a positive focal length and a second lens having a negative focal length. A lens group, a third lens group having a positive focal length, and a fourth lens group having a positive focal length, and at the time of zooming from the wide-angle end to the telephoto end, the first lens group and the second lens group In some cases, the distance increases, the distance between the second lens group and the third lens group decreases, and the distance between the third lens group and the fourth lens group changes.
As a conventional example of this type of zoom lens, there is a type in which the first lens unit is fixed at the time of zooming or the first lens unit is reciprocated in a convex arc shape on the image side. If the movement amount of the second lens group that bears a large amount is to be secured, the diaphragm disposed in the vicinity of the third lens group is separated from the first lens group even at the wide-angle end, and wide-angle / high zooming is achieved. Therefore, the first lens unit becomes very large. Therefore, in order to realize a wide-angle, high-magnification, and compact zoom lens, it is desirable that the first lens unit be moved so that it is positioned closer to the object side at the telephoto end than at the wide-angle end. In addition, by making the total lens length at the wide-angle end shorter than that at the telephoto end, it is possible to sufficiently widen the angle while suppressing an increase in the size of the first lens unit.

  On the other hand, it is known that use of a lens having anomalous dispersion is effective in correcting chromatic aberration that tends to occur with higher zoom ratio and longer focal length. In order from the object side, there are a first lens group having a positive focal length, a second lens group having a negative focal length, a third lens group having a positive focal length, and a fourth lens group having a positive focal length. In zooming from the wide-angle end to the telephoto end, the distance between the first lens group and the second lens group increases, the distance between the second lens group and the third lens group decreases, and the third lens group As conventional examples in which a lens having anomalous dispersion is used as a zoom lens whose distance from the fourth lens group changes, Patent Document 1 (Japanese Patent Laid-Open No. 08-248317) and Patent Document 2 (Japanese Patent Laid-Open No. 2001-194590). ), Patent Document 3 (Japanese Patent Laid-Open No. 2004-333768), Patent Document 4 (Japanese Patent Laid-Open No. 2008-026837), and the like.

However, in the zoom lens disclosed in Patent Document 1, since the first lens group is fixed at the time of zooming, no widening is achieved, and the half angle of view at the wide-angle end is only 25 degrees. . The zoom lens disclosed in Patent Document 2 also has an angle of view at the wide-angle end of about 29 to 32 degrees in the four-group configuration examples (Examples 1, 2, and 6) of positive, negative, positive, and positive. It is insufficient in terms of widening the angle. The zoom lens disclosed in Patent Document 3 has a wide half-angle of view at the wide-angle end of about 37 degrees. However, the total number of the 14 lenses is complicated, and the size is reduced (when stored). There is a problem in terms of cost reduction. The zoom lens disclosed in Patent Document 4 achieves a wide angle and a high zoom ratio with a relatively simple configuration, but it cannot be said that the total length at the telephoto end is sufficiently short. This is another step.
The present invention has been made in view of the above-described circumstances, and the invention according to claim 1 has a half angle of view at a wide angle end of 38 degrees or more and a sufficiently wide angle of view while being 6.5 times or more. It has a zoom ratio, the number of components is as small as about 10, and it can correct spherical aberration and coma better. It is small and has high resolution that can handle 10 to 15 million pixels. It aims to provide a zoom lens.

The invention according to claim 2 has a zoom ratio of 6.5 times or more while the half angle of view at the wide-angle end is sufficiently wide as 38 degrees or more, and the number of components is as small as about ten, An object of the present invention is to provide a high-performance zoom lens that can correct spherical aberration and coma aberration better, is small, and has a resolving power corresponding to an image sensor with 10 to 15 million pixels.
In the third aspect of the invention, the half angle of view at the wide-angle end is a sufficiently wide angle of 38 degrees or more, but has a zoom ratio of 6.5 times or more, and the number of components is as small as about 10 sheets. It is an object of the present invention to provide a means for realizing a zoom lens having a resolving power corresponding to an image sensor with a size of 10 to 15 million pixels with higher quality and lower cost.
The invention according to claim 4, was better correct the chromatic aberration, and its object is to provide a high-performance zoom lens.
The invention according to claim 5, and more favorably correct each aberration, and its object is to provide a high-performance zoom lens compact.
請 Motomeko 6 to the invention of claim 9, the aberrations were further excellently corrected, and its object is to provide a high-performance zoom lens.

The invention according to claim 10 has a zoom ratio of 6.5 to 10 times or more while the half angle of view at the wide angle end is a sufficiently wide angle of 38 degrees or more, and the number of components is about ten. It is an object of the present invention to provide a small and high-quality camera using a zoom lens having a resolving power corresponding to an image sensor with 10 to 15 million pixels as a photographic optical system.
According to the eleventh aspect of the present invention, the half angle of view at the wide-angle end has a zoom ratio of 6.5 to 10 times while having a sufficiently wide angle of view of 38 degrees or more, and the number of components is 10 PROBLEM TO BE SOLVED: To provide a small-sized and high-quality portable information terminal device using a zoom lens having a resolving power corresponding to an image sensor with a size of 10 to 15 million pixels as a photographing optical system of a camera function unit. It is aimed.

The zoom lens according to any one of claims 1 to 9 of the present invention includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a positive refractive power. a third lens group having made a fourth lens group having positive refractive power, upon zooming from the wide-angle end to the telephoto end, the distance between the second lens group and the third lens group increases The distance between the second lens group and the third lens group decreases, the distance between the third lens group and the fourth lens group increases, and the first lens group and the third lens group are wide-angle. The zoom lens moves so as to be positioned closer to the object side at the telephoto end than at the end, and further has the following characteristics, respectively.
In order to achieve the above object, a zoom lens according to claim 1 is provided.
The first lens group has two positive lenses;
A negative lens with a strong concave surface facing the image side is disposed on the most image side of the third lens group, and the following conditional expression is satisfied:
0.6 <| r _3R | / f _W <1.3 (6)
While aperture stop disposed between the second lens group and the third lens group has a positive lens made of optical glass to said first lens group, the refractive optical glass constituting the positive lens n _d Ν _d is the Abbe number of the optical glass constituting the positive lens, P _{g and F} are partial dispersion ratios of the optical glass constituting the positive lens , and r _3R is the curvature of the most image side surface of the third lens group. When the radius, _fw is the focal length of the entire system at the wide angle end , the following conditional expression is satisfied.
_{1.52 <n d <1.62 (1} )
65.0 <ν _d <75.0 (2)
0.015 <P _{g, F} − (− 0.001802 × ν _d +0.6483) <0.050 (3)
_Here, P _{g, F =} a _{(n g -n F) / (} n F -n C), n g, n F, n C , respectively, of the optical glass constituting the positive lens, g line , F line, C line.

The zoom lens according to claim 2,
In order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens having a positive refractive power And a fifth lens group having a positive refracting power, the distance between the first lens group and the second lens group increases upon zooming from the wide-angle end to the telephoto end, and the second lens The distance between the third lens group and the third lens group decreases, the distance between the third lens group and the fourth lens group increases, and the first lens group and the third lens group are at the telephoto end rather than at the wide-angle end. In the zoom lens that moves so that it is located on the object side with
The first lens group has two positive lenses;
A negative lens having a strong concave surface facing the image side is disposed on the most image side of the third lens group, and the following conditional expression is satisfied:
0.6 <| r _3R | / f _w <1.3 (6)
An aperture stop is disposed between the second lens group and the third lens group, and the first lens group has a positive lens made of optical glass, and the positive lens satisfies the following conditional expression: It is characterized by.
_{1.52 <n d <1.62 (1} )
65.0 <ν _d <75.0 (2)
0.015 <P _{g, F} − (− 0.001802 × ν _d +0.6483) <0.050 (3)
Where n _d is the refractive index of the optical glass constituting the positive lens, ν _d is the Abbe number of the optical glass constituting the positive lens, and P _{g and F} are the portions of the optical glass constituting the positive lens. variance ratio, r _3R is, the curvature of the most image side surface of the third lens group, f _w represents the focal length of the entire system at the wide-angle end.
_Here, P _{g, F =} a _{(n g -n F) / (} n F -n C), n g, n F, n C , respectively, of the optical glass constituting the positive lens, g line , F-line, C-line refractive index.
In the zoom lens according to claim 3 , in the zoom lens according to claim 1 or 2 , when F _A is a degree of wear of the optical glass constituting the positive lens, the following conditional expression (4) is satisfied: It is characterized by satisfaction.
30 <F _A <500 (4)
The zoom lens according to claim 4, in the zoom lens according to any one of claims 1 to claim 3, the optical of the first lens group satisfies the conditional expression according to f _ap to claim 1 When the focal length, f _W , of the positive lens made of glass is the focal length of the entire system at the wide angle end, the following conditional expression is satisfied.
5.0 <f _ap / f _W <15.0 (5)
The zoom lens according to claim 5 is the zoom lens according to any one of claims 1 to 4 , wherein at least one of the positive lenses in the first lens group has an aspherical surface. The positive lens having the aspherical surface satisfies the conditional expression described in claim 1 .

請 Motomeko zoom lens according to 6, in the zoom lens according to any one of claims 1 to 5, wherein the first lens group when the X ₁ to zooming from the wide-angle end to the telephoto end the total amount of movement, when the focal length of the entire system at the telephoto end of the f _T, and satisfies the following conditional expression.
_{0.20 <X 1 / f T <} 0.45 (7)
The zoom lens according to claim 7, in the zoom lens according to any one of claims 1 to 6, of the third lens group when the X ₃ in zooming from the wide-angle end to the telephoto end when the total amount of movement, characterized by satisfying the following conditional expression.
0.15 <X ₃ / f _T <0.40 (8)
The zoom lens according to claim 8, in the zoom lens according to any one of claims 1 to 7, the focal length of the f ₂ the second lens group, of f ₃ the third lens group when the focal length, and satisfies the following conditional expression.

0.50 <| f ₂ | / f ₃ <0.85 (9)
The zoom lens according to claim 9 satisfies the following conditional expression when f ₁ is a focal length of the first lens group in the zoom lens according to any one of claims 1 to 8. It is characterized by doing.
5.0 <f ₁ / f _W <8.0 (10)
The camera of claim 10 of the present invention, the zoom lens according to claims 1 or one of claims 9, characterized in that it has as a photographing optical system.
Portable information terminal device according to claim 11 of the present invention, the zoom lens according to claims 1 or one of claims 9, characterized in that it has a photographic optical system of a camera functional part.

According to the first and second aspects of the present invention, the half angle of view at the wide-angle end is 38 degrees or more, and has a zoom ratio of 6.5 or more while being a sufficiently wide angle of view, and the number of components is It is possible to provide a high-performance zoom lens that can reduce spherical aberration and coma aberration better and has a resolving power corresponding to an image sensor with 10 to 15 million pixels. Therefore, it is possible to realize a camera and a portable information terminal device that are small in size and high in image quality and have a zooming range that sufficiently covers a normal photographing region.
According to the third aspect of the present invention, the half angle of view at the wide-angle end is 38 degrees or more and has a zoom ratio of 6.5 times or more while being a sufficiently wide angle of view, and the number of components is about ten. It is possible to provide a means to realize a zoom lens having a resolution that is small and small and capable of resolving an image sensor with 10 to 15 million pixels at a higher quality and at a lower cost. In addition, a camera and a portable information terminal device having a zooming range that sufficiently covers a normal shooting area can be supplied more stably with good cost performance.
According to the invention described in claim 4 , it is possible to provide a high-performance zoom lens in which chromatic aberration is corrected more favorably. As a result, color misregistration at the periphery of the screen at the wide-angle end and screen at the telephoto end. It is possible to realize a camera and a portable information terminal device that can achieve good depiction while further suppressing color bleeding and the like over the entire image.

According to the fifth aspect of the present invention, it is possible to provide a small and high-performance zoom lens in which each aberration is corrected more favorably. A small camera and a portable information terminal device can be realized .
According to the invention described in 請 Motomeko 6 to claim 9, the aberrations were better corrected, it is possible to provide a high-performance zoom lens, by extension, high quality camera having a higher resolution And a portable information terminal device can be realized.
According to the tenth aspect of the present invention, the half angle of view at the wide angle end is a wide angle of 38 degrees or more, but has a zoom ratio of 6.5 to 10 times or more, and the number of components is ten. It is possible to provide a small, high-quality camera using a zoom lens having a resolving power corresponding to an image sensor with 10 to 15 million pixels that is small and small as a photographing optical system. High quality images can be taken with a portable camera.

According to the eleventh aspect of the present invention, the half angle of view at the wide angle end is a wide angle of view of 38 degrees or more, and has a zoom ratio of 6.5 to 10 times or more, and the number of components is ten. It is possible to provide a small and high-quality portable information terminal device that uses a zoom lens having a resolving power corresponding to an image sensor with a size of 10 to 15 million pixels as a photographing optical system of a camera function unit. In addition, the user can take a high-quality image with a portable information terminal device excellent in portability, and transmit the image to the outside.

FIG. 2 is a cross-sectional view showing a configuration of an optical system of a zoom lens according to Numerical Example 1 of the present invention and a zoom locus accompanying zooming, in which (a) is a wide angle end, (b) is an intermediate focal length, and (c). These are sectional views along the optical axis at each of the telephoto ends. FIG. 7 is a diagram illustrating a configuration of an optical system of a zoom lens according to Numerical Example 2 of the present invention and a zoom locus associated with zooming, where (a) is a wide angle end, (b) is an intermediate focal length, and (c) is a telephoto end. It is sectional drawing along the optical axis in each. FIG. 7 is a diagram illustrating the configuration of an optical system of a zoom lens according to Numerical Example 3 of the present invention and a zoom locus associated with zooming, where (a) is a wide angle end, (b) is an intermediate focal length, and (c) is a telephoto end. It is sectional drawing along the optical axis in each. It is a figure which shows the structure of the optical system of the zoom lens based on Numerical Example 4 of this invention, and the zoom locus | trajectory accompanying zooming, (a) is a wide angle end, (b) is an intermediate focal length, (c) is a telephoto end. It is sectional drawing along the optical axis in each. FIG. 3 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the wide angle end of the zoom lens according to Numerical Example 1 of the present invention shown in FIG. 1. FIG. 3 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the intermediate focal length of the zoom lens according to Example 1 of the present invention shown in FIG. 1. FIG. 3 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the telephoto end of the zoom lens according to Example 1 of the present invention shown in FIG. 1. FIG. 6 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the wide angle end of the zoom lens according to Embodiment 2 of the present invention shown in FIG. 2. FIG. 5 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the intermediate focal length of the zoom lens according to Example 2 of the present invention shown in FIG. 2. FIG. 6 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the telephoto end of the zoom lens according to Example 2 of the present invention shown in FIG. 2. FIG. 6 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the wide angle end of the zoom lens according to Embodiment 3 of the present invention shown in FIG. 3. FIG. 6 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the intermediate focal length of the zoom lens according to Embodiment 3 of the present invention shown in FIG. 3. FIG. 6 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the telephoto end of the zoom lens according to Embodiment 3 of the present invention shown in FIG. 3. FIG. 5 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the wide angle end of the zoom lens according to Embodiment 4 of the present invention shown in FIG. 4. FIG. 5 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the intermediate focal length of the zoom lens according to Embodiment 4 of the present invention shown in FIG. 4. FIG. 6 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the telephoto end of the zoom lens according to Embodiment 4 of the present invention shown in FIG. 4. It is the perspective view seen from the object side which shows the appearance composition of the camera concerning one embodiment of the present invention typically, (a) is the state where the photographing lens is buried in the body of the camera, (b) Indicates a state in which the taking lens protrudes from the body of the camera. It is the perspective view seen from the photographer side which shows typically the external appearance structure of the camera of FIG. It is a block diagram which shows typically the function structure of the camera of FIG.

Hereinafter, based on an embodiment of the present invention, a zoom lens, a camera, and a portable terminal device according to the present invention will be described in detail with reference to the drawings. Before describing specific examples, first, a fundamental embodiment of the present invention will be described.
In general, the zoom lens composed of four positive, negative, positive, and positive lens groups or the zoom lens composed of five positive, negative, positive, positive, and positive lens groups as in the present invention is mainly composed of the second lens group. It is configured as a so-called variator that bears a variable magnification action. However, in the present invention, the third lens group also shares the zooming action, reduces the burden on the second lens group, and provides the degree of freedom of aberration correction that becomes difficult with widening and high zooming. Secured. Further, when zooming from the wide-angle end to the telephoto end, the height of the light beam passing through the first lens group is lowered at the wide-angle end by moving the first lens unit largely toward the object side, and the first lens unit accompanying the widening of the angle. In addition to suppressing an increase in size of one lens unit, a long distance is achieved by ensuring a large distance between the first lens unit and the second lens unit at the telephoto end.
During zooming from the wide-angle end to the telephoto end, the distance between the first lens group and the second lens group is increased, and the distance between the second lens group and the third lens group is decreased, so that the second lens group and the third lens group are Both magnifications (absolute values) of the lens group increase and share the zooming action.

Furthermore, in the zoom lens of the present invention, the first lens group includes a positive lens made of optical glass so that the following conditional expression is satisfied .
_{1.52 <n d <1.62 (1} )
65.0 <ν _d <75.0 (2)
0.015 <P _{g, F} − (− 0.001802 × ν _d +0.6483) <0.050
(3)
Where n _d is the refractive index of the optical glass constituting the positive lens, ν _d is the Abbe number of the optical glass constituting the positive lens, and P _{g and F} are the portions of the optical glass constituting the positive lens. Represents the dispersion ratio.
_Here, P _{g, F =} a _{(n g -n F) / (} n F -n C), n g, n F, n C , respectively, of the optical glass constituting the positive lens, g line , F-line, C-line refractive index.
If an attempt is made to increase the zoom ratio, particularly to increase the focal length at the telephoto end, it becomes difficult to correct the secondary spectrum of longitudinal chromatic aberration on the telephoto side. In addition, if the focal length at the wide angle end is shortened to make the angle wider, it is difficult to correct the secondary spectrum of lateral chromatic aberration on the wide angle side.

The present invention intends to correct these chromatic aberrations using an anomalous dispersion material (a material having a large anomalous dispersion), but has a great feature in its optical characteristics.
In order to reduce the secondary spectrum of axial chromatic aberration, special low-dispersion glass is highly effective for a lens group having a high axial ray height. In particular, at least on the telephoto side, the first lens group has the highest axial ray height, and the use of special low dispersion glass makes it possible to sufficiently reduce the secondary spectrum of axial chromatic aberration. However, special low-dispersion glass generally has a low refractive index, resulting in a reduction in monochromatic aberration correction capability. Therefore, when it is intended to reduce monochromatic aberration and chromatic aberration in a well-balanced manner while configuring the first lens group with a small number of lenses, the use of special low dispersion glass does not necessarily give a sufficient effect.
Therefore, in the present invention, at least one positive lens in the first lens group has a refractive index, an Abbe number, and an anomalous dispersion within a range that satisfies the conditional expressions (1), (2), and (3). It consisted of optical glass. As a result, even when the first lens group is a small number of three or less, the secondary spectrum of chromatic aberration can be reduced and sufficient correction of monochromatic aberration can be achieved.
1.52 _{<n d <n} d is 1.52 or less and the monochromatic aberration corrected for 1.62 condition: (1) becomes insufficient, 65.0 <ν _d <75.0 conditional expression ( When ν _{d of} 2) is 65.0 or less, correction of chromatic aberration is insufficient, and P _{g, F} − (− 0.001802 × ν _d +0.6483) of conditional expression (3) is 0.015 or less. If so, correction of the secondary spectrum of chromatic aberration is insufficient.

On the other hand, there is no optical glass that exceeds the upper limit for all conditional expressions (1), (2), and (3), or even if it exists, it is very special and expensive, and is not practical.
In the zoom lens of the present invention, the optical glass constituting the positive lens of the first lens group that satisfies the conditional expressions (1), (2), and (3) according to claim 1 is worn in the conditional expression (4). degrees _{F a} exceeds 30, not to want to be less than 500.
In general, optical glasses having relatively low dispersion and anomalous dispersion often have a high degree of wear. Particularly, optical glasses having a wear level exceeding 500 have high accuracy in lens processing processes such as polishing, centering, and cleaning. There are problems such as being difficult to remove and being easily scratched, leading to a decrease in quality and an increase in cost. _A positive lens of the third lens group is configured by optical glass having a wear degree FA of Conditional Expression (4) of less than 500 while satisfying Conditional Expressions (1), (2), and (3) of Claim 1. This is very important in terms of maintaining high quality at a low cost. On the other hand, if the degree of wear F _A is 30 or less, it takes a long time for polishing, which is also not preferable because it increases the cost.
Here, the degree of wear F _A means that a sample having a measurement area of 9 cm ² is held at a fixed position of 80 mm from the center of a flat plate made of cast iron that rotates horizontally 60 minutes per minute, and 10 g of alumina abrasive grains having an average particle diameter of 20 μm The same amount of wear loss m when wrapping with a load of 9.807 N and the standard sample (BSC7) specified by the Japan Optical Glass Industry Association are supplied. The ratio of the weight loss m ₀ when tested under conditions is measured, and the following equation is calculated.

F _A = {(m / d) / (m ₀ / d ₀ )} × 100 (4) ′
Here, d represents the specific gravity of the sample, and d ₀ represents the specific gravity of the standard sample.
In the zoom lens of the present invention, at least one of the positive lenses made of optical glass of the first lens group that satisfies the conditional expressions (1), (2), and (3) according to claim 1 is the following conditional expression: it was desired to have a refractive power that satisfies.
5.0 <f _ap / f _W <15.0 (5)
However, f _ap is the focal length of the positive lens made of the optical glass of the first lens group that satisfies the conditional expressions (1), (2), and (3) according to claim 1, and f _W is at the wide angle end. Represents the focal length of the entire system.
If f _ap / f _{W in} conditional expression (5) is 15.0 or more, the refractive power of the lens using the anomalous dispersion material is not sufficient to sufficiently reduce the secondary spectrum, and sufficient chromatic aberration correction cannot be performed. There is a case. On the other hand, if f _ap / f _W in conditional expression (5) is 5.0 or less, it becomes difficult to balance chromatic aberration correction and spherical aberration correction, and the curvature of each surface of the lens increases. This is also disadvantageous in terms of processing accuracy.

In order to increase the degree of freedom of aberration correction, at least one of the positive lenses in the first lens group can be configured to have an aspherical surface. condition (1), (2), it has to desired to satisfy (3).
As an optical glass having anomalous dispersion that satisfies the conditional expressions (1), (2), and (3) according to claim 1, those suitable for aspherical molding by glass molding technology have been developed. By using this, it is possible to obtain an aspheric lens having stable performance at low cost.
In that case, the first lens group has to desired to have two positive lenses.
Since one positive lens can be a spherical lens, the selection range of the refractive index and the Abbe number is wide, and the aberration correction can be optimized by sharing the positive power between the two lenses. In particular, by selecting a material having a higher refractive index, chromatic aberration correction and monochromatic aberration correction can be balanced in a high dimension.
In addition, even when a lens using optical glass having anomalous dispersion is produced by glass mold technology, cold processing such as polishing is often required for forming a preform as a base material before molding. The point that the degree of wear of the material is important remains the same.

For better aberration correction, it is desirable to dispose a negative lens having a strong concave surface on the image side closest to the image side of the third lens group and satisfy the following conditional expression (6). Yes.
0.6 <| r _3R | / f _W <1.3 (6)
Here, r _3R represents the radius of curvature of the most image-side surface of the third lens group , and fw represents the focal length of the entire system at the wide angle end .
When | r _3R | / f _{W in} conditional expression (6) is 0.6 or less, spherical aberration tends to be overcorrected, and | r _3R | / f _W in conditional expression (6) is 1.3 or more. Conversely, spherical aberration tends to be undercorrected. Further, outside the range of conditional expression (6), it is difficult to balance coma as well as spherical aberration, and outward or inward coma tends to occur in the off-axis peripheral part.
Furthermore, in relation to the movement of the first lens group important for the wider angle and a length focusing, by satisfying the following conditional expression, that Do is possible to sufficiently correct aberrations.
_{0.20 <X 1 / f T <} 0.45 (7)
However, X ₁ is the total amount of movement of the first lens group when changing magnification from the wide-angle end to the telephoto end, f _T represents the focal length of the entire system at the telephoto end.

If X ₁ / f _T in conditional expression (7) is 0.20 or less, the contribution of the second lens group to the zooming is reduced and the burden on the third lens group is increased, or the first lens group and the second lens group are increased. The refractive power of the two lens groups must be increased, and in any case, various aberrations are deteriorated. In addition, the total lens length at the wide-angle end is increased, and the height of light passing through the first lens group is increased, leading to an increase in size of the first group. On the other hand, if X ₁ / f _T in conditional expression (7) is 0.45 or more, the total length at the wide-angle end becomes too short, or the total length at the telephoto end becomes too long. If the total length at the wide-angle end becomes too short, the moving space of the third lens group is limited, the contribution of the third lens group to zooming becomes small, and it becomes difficult to correct the entire aberration. If the total length at the telephoto end becomes too long, it will not only hinder downsizing in the full-length direction, but the radial direction will be enlarged to secure the amount of peripheral light at the telephoto end, and the lens barrel will be tilted. Degradation of image performance due to errors is also likely to occur.
It is more desirable to satisfy the following conditional expression (7) ′.
_{0.25 <X 1 / f T <} 0.40 (7) '
For the moving amount of the third lens group share the changing magnification function second lens group, not to desirable to satisfy the following condition (8).
0.15 <X ₃ / f _T <0.40 (8)
However, X ₃ represents the total amount of movement of the third lens group when changing magnification from the wide-angle end to the telephoto end.

If X ₃ / f _T in conditional expression (8) is less than or equal to the lower limit of 0.15, the contribution of the third lens group to zooming will be reduced, increasing the burden on the second lens group, The refractive power of the lens group itself must be increased, and in any case, various aberrations are deteriorated. On the other hand, if X ₃ / f _T in conditional expression (8) is 0.40 or more, which is the upper limit value, the total lens length at the wide-angle end increases, and the height of light passing through the first lens group increases. This increases the size of the lens group.
More preferably, the following conditional expression (8) ′ should be satisfied.
0.20 <X ₃ / f _T <0.35 (8) ′
In addition, from the top of the aberration correction, the following condition concerning the refractive power of each group (9), has to desired to satisfy (10).
0.50 <| f ₂ | / f ₃ <0.85 (9)
5.0 <f ₁ / f _W <8.0 (10)
Where f ₁ is the focal length of the first lens group, f ₂ is the focal length of the second lens group, f ₃ is the focal length of the third lens group, and f _W is the focal length of the entire system at the wide angle end. Represent.
If conditional expression (9) | f ₂ | / f ₃ is 0.50 or less, the refractive power of the second lens group becomes too strong, and if | f ₂ | / f ₃ is 0.85 or more, the third lens The refractive power of the group becomes too strong, and in any case, the aberration fluctuation during zooming tends to increase.

Further, if f ₁ / f _W in conditional expression (10) is 5.0 or less, the imaging magnification of the second lens unit approaches the same magnification and the zooming efficiency increases, which is advantageous for high zooming. However, each lens of the first lens group requires a large refractive power, and not only has adverse effects such as deterioration of chromatic aberration at the telephoto end, but also the first lens group becomes thicker and larger in diameter, In particular, it is disadvantageous in realizing miniaturization in the storage state. On the other hand, if f ₁ / f _W in conditional expression (10) is 8.0 or more, the contribution of the second lens group to zooming becomes small, and high zooming becomes difficult.
In the zoom lens of the present invention, an aperture stop is disposed between the second lens group and the third lens group, and the aperture stop can be moved independently of the adjacent lens group. With such a configuration, it is possible to select a more optimal ray path at any position in a large zooming region of 6.5 times or more, and in particular, there is a degree of freedom in correcting coma aberration, field curvature, and the like. And off-axis performance can be improved.
The distance between the aperture stop and the third lens group is desirably wider at the wide angle end than at the telephoto end. The third lens group using the anomalous dispersion material moves away from the aperture stop at the wide-angle end and approaches the aperture stop at the telephoto end, so that the anomalous dispersion is effective in correcting the secondary spectrum of lateral chromatic aberration at the wide-angle end. It works effectively at the telephoto end to correct the secondary spectrum of axial chromatic aberration. Therefore, chromatic aberration can be corrected more satisfactorily in the entire zoom range. In addition, the aperture stop can be brought closer to the first lens group at the wide-angle end, and the height of the light beam passing through the first lens group can be made lower, thereby further reducing the size of the first group. Born.

For the reasons described above, when the distance between the aperture stop and the third lens group is wider than the telephoto end at the wide angle end, it is desirable to satisfy the following conditional expression (11) with respect to the distance.
0.05 <d _SW / f _T <0.20 (11)
Here, d _SW represents the axial distance between the aperture stop at the wide-angle end and the most object side surface of the third lens group.
When d _SW / f _T in conditional expression (11) is 0.05 or less, the height of the light beam passing through the third lens group at the wide angle end becomes small, and the reduction of the secondary spectrum of lateral chromatic aberration at the wide angle side is effective. Cannot be performed. Similarly, the height of the light beam passing through the first lens group at the wide-angle end becomes too large, leading to an increase in size of the first lens group. On the other hand, if d _SW / f _T in conditional expression (11) is 0.20 or more, the height of the light beam passing through the third lens group at the wide angle end becomes too large, the image surface falls over, As distortion becomes large, it becomes difficult to ensure performance particularly in a wide angle region.
The first lens group preferably has at least one negative lens and at least one positive lens from the object side. More specifically, either a negative meniscus lens having a convex surface facing the object side and a positive lens having a strong convex surface facing the object side in order from the object side, or in order from the object side to the object side A negative meniscus lens having a convex surface, a positive lens having a strong convex surface on the object side, and a positive lens having a strong convex surface on the object side may be used.

In order to increase the zoom ratio, in particular to increase the focal length at the telephoto end, it is necessary to increase the combined magnification of the second lens group, the third lens group, and the fourth lens group at the telephoto end. The aberration generated in the lens group is magnified on the image plane. For this reason, in order to advance the zooming ratio, it is necessary to sufficiently reduce the amount of aberration generated in the first lens group. For this purpose, the first lens group is preferably configured as described above.
The second lens group includes, in order from the object side, a negative lens having a large curvature surface facing the image side, a positive lens having a large curvature surface facing the image side, and a negative lens having a large curvature surface facing the object side. It is desirable to consist of three sheets.
As a variable power group having a negative refractive power, in the case where this is constituted by three lenses, an arrangement of a negative lens, a negative lens, and a positive lens in order from the object side is well known. Thus, the above configuration is excellent in the ability to correct lateral chromatic aberration associated with widening the angle. Here, the second lens and the third lens from the object side may be appropriately joined.
At this time, it is desirable that each lens of the second lens group satisfies the following conditional expressions (12), (13), and (14).
1.75 <n ₂₁ <2.10, 25 <ν ₂₁ <55 (12)
1.75 <n ₂₂ <2.10, 15 <ν ₂₂ <35 (13)
1.75 <n ₂₃ <2.10, 25 <ν ₂₃ <55 (14)
Here, n _2i represents the refractive index of the i-th lens counted from the object side in the second group, and ν _2i represents the Abbe number of the i-th lens counted from the object side in the second group.

By selecting such a glass type, it is possible to correct chromatic aberration more satisfactorily while keeping monochromatic aberration sufficiently small.
The third lens group is preferably composed of three lenses in order from the object side: a positive lens, a positive lens, and a negative lens. Here, the second lens and the third lens from the object side may be appropriately joined.
In the zoom lens of the present invention, the fourth lens group is provided mainly for securing an exit pupil distance (telecentricity) and focusing by moving the fourth lens group. In order to reduce the size of the lens system, the fourth lens group needs to be as simple as possible, and is preferably composed of one positive lens.
The zoom lens of the present invention is not limited to the four-group configuration. Since it is necessary to increase the degree of freedom in order to ensure performance, such as suppressing fluctuations in aberrations during zooming, a configuration in which the fifth lens group is provided on the image side of the fourth lens group may be employed.
In order to further reduce the size while maintaining good aberration correction, an aspheric surface is indispensable, and at least the second lens group and the third lens group each preferably have one or more aspheric surfaces. In particular, in the second lens group, if both the most object-side surface and the most image-side surface are aspherical surfaces, it is highly effective in correcting distortion and astigmatism that tend to increase as the angle of view increases. Is obtained.

In addition, as an aspherical lens, optical glass or optical plastic molded (glass molded aspherical surface, plastic molded aspherical surface), or a thin resin layer is molded on the surface of the glass lens, and the surface is aspherical. A thing (it is called a hybrid aspherical surface, a replica aspherical surface, etc.) etc. can be used.
It may be simplified in terms of the mechanism that the aperture diameter of the aperture is constant regardless of zooming. However, the change in the F number accompanying zooming can be reduced by increasing the length of the long focal point compared to the short focal point having an open diameter. Further, when it is necessary to reduce the amount of light reaching the image plane, the diameter of the stop may be reduced. However, if the amount of light is reduced by inserting an ND filter or the like without greatly changing the diameter of the stop, it is caused by the diffraction phenomenon. It is preferable because a decrease in resolution can be prevented.
Hereinafter, a specific numerical example 4 will be described together with an embodiment of the zoom lens of the present invention. In all of the examples, the maximum image height is 4.05 mm. Hereinafter, numerical examples may be simply referred to as “examples”.
The first embodiment has a five-group configuration of positive / negative / positive / positive / positive, and the second to fourth embodiments have a four-group configuration of positive / negative / positive / positive.

In each embodiment, the parallel plate disposed on the image plane side of the fourth lens group G4 or the fifth lens group G5 includes various optical filters such as an optical low pass filter and an infrared cut filter, and a light receiving element such as a CCD sensor. Cover glass (seal glass) is assumed, and here it will be referred to as various filters FM. In the figure, FP represents an image plane. The unit of the quantity having a length dimension is “mm” unless otherwise specified.
The materials of the lenses are all optical glass except that the positive lens of the fourth lens group G4 in all the embodiments is an optical plastic.
The aberration in each example is sufficiently corrected, and can correspond to a light receiving element having 10 to 15 million pixels. It is clear from the embodiments that the zoom lens is configured as in the present invention, and a very good image performance can be ensured while achieving a sufficiently small size.
The meanings of symbols common to Examples 1 to 4 are as follows.

f: Focal length of the entire system F: F number (F value)
ω: Half angle of view (degrees)
R: radius of curvature (for aspheric surfaces, paraxial radius of curvature)
D: Spacing between surfaces n _d : Refractive index ν _d : Abbe number K: Aspherical conic constant A ₄ : Fourth-order aspheric coefficient A ₆ : Sixth-order aspheric coefficient A ₈ : Eighth-order aspheric coefficient A ₁₀ : 10th-order aspheric coefficient A ₁₂ : 12th-order aspheric coefficient A ₁₄ : 14th-order aspheric coefficient A ₁₆ : 16th-order aspheric coefficient A ₁₈ : 18th-order aspheric coefficient The spherical shape is defined by the reciprocal of the paraxial radius of curvature (paraxial curvature) as C, the height from the optical axis as H, and the conic constant as K, using the aspheric coefficients of the above orders, and the optical axis direction of X. Is defined by the following equation (15), and a shape is specified by giving a paraxial radius of curvature, a conic constant, and an aspheric coefficient.

  FIG. 1 schematically shows a lens configuration of a zoom lens according to Embodiment 1 of the present invention and a zoom locus associated with zooming from a wide-angle end to a telephoto end through a predetermined intermediate focal length. ) Is a schematic cross-sectional view at the wide-angle end (Wide), (b) is a schematic cross-sectional view at a predetermined intermediate focal length (Mean), and (c) is a schematic cross-sectional view at the telephoto end (Tele). In FIG. 1 showing the lens group arrangement of Example 1, the left side is the object side.

The zoom lens shown in FIG. 1 includes a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a positive refractive power in order from the object side along the optical axis. A third lens group G3 having a positive refractive power, a fifth lens group G5 having a positive refractive power, and a second lens group G2 and a third lens group G3. An aperture stop AD is arranged between the two. In this case, the first lens group G1 includes a first lens E1, a second lens E2, and a third lens E3, and the second lens group G2 includes a fourth lens E4, a fifth lens E5, and a sixth lens. E6, the third lens group G3 has a seventh lens E7, an eighth lens E8 and a ninth lens E9, and the fourth lens group G4 has a tenth lens E10. Thus, the fifth lens group G5 includes an eleventh lens E11.
The first lens group G1 to the fifth lens group G5 are supported by a common support frame or the like that is appropriate for each group. When zooming or the like, the first lens group G1 to the fifth lens group G5 operate for each group except for the fifth group. , Operate independently of each group. FIG. 1 also shows surface numbers (first surface to twenty-second surface) of each optical surface.
At the time of zooming from the wide angle end (short focal end) to the telephoto end (long focal end), the first lens group G1 to the fourth lens group G4 are moved, and the first lens group G1 and the second lens group are moved. The distance between the group G2 increases, the distance between the second lens group G2 and the third lens group G3 decreases, and the distance between the third lens group G3 and the fourth lens group G4 increases.

The first lens group G1 includes, in order from the object side, a first lens E1 composed of a negative meniscus lens having a convex surface facing the object side, a second lens E2 composed of a positive meniscus lens having a convex surface facing the object side, and an object A third lens E3 made of a positive meniscus lens having a convex surface facing the side is disposed. The two lenses of the first lens E1 and the second lens E2 are closely bonded to each other and bonded together to form a cemented lens composed of two lenses.
The second lens group G2 is a negative meniscus lens having a convex surface directed toward the object side sequentially from the object side, and a fourth lens formed of an aspheric lens having a convex surface facing the object side and forming an aspheric surface. E4, a fifth lens E5 including a biconvex positive lens having a stronger convex surface on the image side, and a negative meniscus lens having a convex surface on the image side, and an aspheric surface forming an aspheric surface on the image side A sixth lens E6 made of a lens is disposed. The two lenses, the fifth lens E5 and the sixth lens E6, are closely bonded to each other and bonded together to form a cemented lens composed of two lenses.
The aperture stop AD is interposed between the second lens group G2 and the third lens group G3.
The third lens group G3 has, from the object side, a seventh lens E7 which is a positive lens having a biconvex shape with a strong convex surface facing the object side and aspheric surfaces on both sides, and a strong convex surface on the image side. An eighth lens E8 composed of a biconvex positive lens and a ninth lens E9 composed of a biconcave negative lens with a strong concave surface facing the image side are arranged. The two lenses of the eighth lens E8 and the ninth lens E9 are closely bonded to each other and joined together to form a cemented lens composed of two lenses.

The fourth lens group G4 includes solely a tenth lens E10, which is a positive meniscus lens having a convex surface directed toward the object side and an aspheric surface facing the object side. The fifth lens group G5 comprises solely an eleventh lens E11 comprising a positive meniscus lens having a convex surface directed toward the object side.
In this case, as shown in FIG. 1, the first lens group G1 and the third lens group G3 are moved from the image side to the object side with zooming from the wide-angle end (short focal end) to the telephoto end (long focal end). The second lens group G2 moves along a locus convex toward the image side, and the fourth lens group G4 moves along a locus convex toward the object side. The fifth lens group G5 does not move.
In Example 1, the focal length f, F number F, and half angle of view ω of the entire optical system are f = 5.07 to 34.46 and F = 3. It changes in the range of 43 to 5.79 and ω = 39.82 to 6.53. The optical characteristics of each optical element are as shown in the following table.

In Table 1, the surface number lens with “*” (asterisk) added to the surface number is an aspheric surface, and the glass manufacturer name is HOYA (HOYA Corporation) before the glass type name as follows. ), And abbreviated as OHARA (Ohara Inc.). The same applies to the other embodiments.
That is, in Table 1, the optical surfaces of the sixth surface, the tenth surface, the twelfth surface, the thirteenth surface, and the seventeenth surface marked with “*” are aspheric surfaces, and The spherical parameters are as follows.
Aspheric surface; 6th surface K = 0.0,
A ₄ = −2.11567 × 10 ⁻⁵ ,
A ₆ = 1.02684 × 10 ⁻⁷ ,
A ₈ = −4.62111 × 10 ⁻⁸ ,
A ₁₀ = 7.002968 × 10 ⁻¹⁰

Aspheric surface: 10th surface K = 0.0,
A ₄ = −6.556577 × 10 ⁻⁴ ,
A ₆ = −6.552956 × 10 ⁻⁶ ,
A ₈ = −1.05912 × 10 ⁻⁶ ,
A ₁₀ = −5.775774 × 10 ⁻⁸
Aspherical surface; twelfth surface K = 0.0,
A ₄ = −8.54494 × 10 ⁻⁴ ,
A ₆ = 5.353710 × 10 ⁻⁶ ,
A ₈ = −8.26341 × 10 ⁻⁷ ,
A ₁₀ = −5.09750 × 10 ⁻⁸

Aspheric surface: 13th surface K = 0.0,
A ₄ = 3.54458 × 10 ⁻⁴ ,
A ₆ = 6.338751 × 10 ⁻⁶ ,
A ₈ = −7.66232 × 10 ⁻⁷ ,
A ₁₀ = −5.58192 × 10 ⁻⁸
Aspherical surface: 17th surface K = 0.0,
A ₄ = −3.04703 × 10 ⁻⁵ ,
A ₆ = 1.04070 × 10 ⁻⁵ ,
A ₈ = −4.676045 × 10 ⁻⁷ ,
A ₁₀ = 9.37621 × 10 ⁻⁹

The variable distance DA between the first lens group G1 and the second lens group G2, the variable distance DB between the second lens group G2 and the aperture stop AD, and the variable distance between the aperture stop AD and the third lens group G3. The distance DC, the variable distance DD between the third lens group G3 and the fourth lens group G4, and the variable distance DE between the fourth lens group G4 and the fifth lens group G5 are as follows. It can be changed as follows.

  FIGS. 5, 6 and 7 show aberration diagrams of spherical aberration, astigmatism, distortion, and coma aberration at the wide-angle end, the intermediate focal length, and the telephoto end, respectively, according to the first embodiment. In these drawings, a broken line in spherical aberration represents a sine condition, a solid line in astigmatism represents sagittal, and a broken line represents meridional. In addition, g and d in the respective aberration diagrams of spherical aberration, astigmatism, and coma aberration represent g-line and d-line, respectively. The same applies to the aberration diagrams of the other examples.

The values of conditional expressions (1) to (11) of the zoom lens according to Example 1 described above are as follows:
(1) n _d = 1.59282
(2) ν _d = 68.63
(3) P _{g, F} − (− 0.001802 × ν _d +0.6483)
= 0.0195 ... HOYA FCD505
(4) F _A = 460 ... HOYA FCD505
(5) f _ap / f _W = 8.59
(6) | r _3R | / f _W = 0.940
_{(7) X 1 / f T} = 0.336
(8) X ₃ / f _T = 0.224
(9) | f ₂ | / f ₃ = 0.668
(10) f ₁ / f _W = 5.85
(11) d _SW / f _T = 0.135
Thus, conditional expressions (1) to (11) are satisfied.

  FIGS. 5, 6 and 7 show aberration diagrams of spherical aberration, astigmatism, distortion, and coma aberration at the wide-angle end, the intermediate focal length, and the telephoto end, respectively, according to the first embodiment. In these drawings, a broken line in spherical aberration represents a sine condition, a solid line in astigmatism represents sagittal, and a broken line represents meridional. In addition, g and d in the respective aberration diagrams of spherical aberration, astigmatism, and coma aberration represent g-line and d-line, respectively. The same applies to the aberration diagrams of the other examples.

FIG. 2 schematically shows a lens configuration of a zoom lens according to Embodiment 2 of the present invention and a zoom locus associated with zooming from the wide-angle end to the telephoto end through a predetermined intermediate focal length. (B) is a schematic cross-sectional view at a predetermined intermediate focal length, and (c) is a schematic cross-sectional view at the telephoto end. In FIG. 2 showing the arrangement of the lens groups of Example 2, the left side is the object side.
The zoom lens shown in FIG. 2 includes, in order from the object side along the optical axis, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a positive refractive power. And a fourth lens group G4 having a positive refractive power, and an aperture stop AD is disposed between the second lens group G2 and the third lens group G3. In this case, the first lens group G1 includes a first lens E1, a second lens E2, and a third lens E3, and the second lens group G2 includes a fourth lens E4, a fifth lens E5, and a sixth lens. E6, the third lens group G3 has a seventh lens E7, an eighth lens E8 and a ninth lens E9, and the fourth lens group G4 has a tenth lens E10. Become.

The first lens group G1 to the fourth lens group G4 are each supported by a common support frame or the like appropriate for each group, and operate simultaneously for each group during zooming or the like. Works independently. FIG. 2 also shows the surface number of each optical surface. 2 are also used independently for each embodiment in order to avoid complication of explanation due to an increase in the number of digits of the reference code. Therefore, the same reference numerals as those of the drawings according to the other embodiments are used. Even if attached, they are not necessarily a common configuration with other embodiments.
During zooming from the wide-angle end to the telephoto end, all the first lens group G1 to the fourth lens group G4 move, and the distance between the first lens group G1 and the second lens group G2 increases. The distance between the second lens group G2 and the third lens group G3 decreases, and the distance between the third lens group G3 and the fourth lens group G4 increases.
The first lens group G1 includes, in order from the object side, a first lens E1 composed of a negative meniscus lens having a convex surface facing the object side, a second lens E2 composed of a positive meniscus lens having a convex surface facing the object side, and an object A third lens E3 made of a positive meniscus lens having a convex surface facing the side is disposed. The two lenses of the first lens E1 and the second lens E2 are closely bonded to each other and bonded together to form a cemented lens composed of two lenses.

The second lens group G2 is a negative meniscus lens having a convex surface directed toward the object side sequentially from the object side, and a fourth lens E4 including an aspheric lens forming an aspheric surface on the object side, and an image A fifth lens E5 composed of a biconvex positive lens having a stronger convex surface on the side, and a negative meniscus lens having a convex surface on the image side, and an aspheric lens forming an aspheric surface on the image side. Six lenses E6 are arranged. The two lenses, the fifth lens E5 and the sixth lens E6, are closely bonded to each other and bonded together to form a cemented lens composed of two lenses.
The aperture stop AD is interposed between the second lens group G2 and the third lens group G3.

The third lens group G3 has, from the object side, a seventh lens E7 which is a positive lens having a biconvex shape with a strong convex surface facing the object side and aspheric surfaces on both sides, and a strong convex surface on the object side. An eighth lens E8 composed of a biconvex positive lens and a ninth lens E9 composed of a biconcave negative lens with a strong concave surface facing the image side are arranged. The two lenses of the eighth lens E8 and the ninth lens E9 are closely bonded to each other and joined together to form a cemented lens composed of two lenses.
The fourth lens group G4 comprises solely a tenth lens E10, which is a biconvex lens having a strong convex surface facing the object side and an aspheric surface facing the object side.

That is, the second embodiment has a four-group configuration different from the first embodiment described above. Also in this case, as shown in FIG. 2, the first lens group G1 and the third lens group G3 monotonously move from the image side to the object side in accordance with the zooming from the wide angle end to the telephoto end. The second lens group G2 moves along a locus convex toward the image side, and the fourth lens group G4 moves along a locus convex toward the object side.
In Example 2, the focal length f, F number F, and half angle of view ω of the entire optical system are f = 5.07 to 34.53, F = 3.45 to 5.61, ω, respectively, by zooming. It varies in the range of 39.75 to 6.55. The optical characteristics of each optical element are as shown in the following table.

In Table 3, the optical surfaces of the sixth surface, the tenth surface, the twelfth surface, the thirteenth surface, and the seventeenth surface marked with “*” are aspheric surfaces, and each of the aspheric surfaces in Expression (15) The parameters are as follows:
Aspherical parameters Aspherical surface; 6th surface K = 0.0,
A ₄ = 4.38118 × 10 ⁻⁵ ,
A ₆ = −3.28212 × 10 ⁻⁶ ,
A ₈ = 1.678801 × 10 ⁻⁷ ,
A ₁₀ = −4.332537 × 10 ⁻⁹ ,
A ₁₂ = −1.266659 × 10 ⁻¹¹ ,
A ₁₄ = 1.27763 × 10 ⁻¹²

Aspheric surface: 10th surface K = 0.0,
A ₄ = −4.80018 × 10 ⁻⁴ ,
A ₆ = −4.53081 × 10 ⁻⁶ ,
A ₈ = −2.73503 × 10 ⁻⁷ ,
A ₁₀ = −5.07166 × 10 ⁻⁸
Aspherical surface; twelfth surface K = 0.0,
A ₄ = −8.77604 × 10 ⁻⁴ ,
A ₆ = 1.71719 × 10 ⁻⁵ ,
A ₈ = −1.39333 × 10 ⁻⁶ ,
A ₁₀ = 9.31505 × 10 ⁻⁸

Aspheric surface: 13th surface K = 0.0,
A ₄ = 5.889357 × 10 ⁻⁴ ,
A ₆ = 3.03606 × 10 ⁻⁵ ,
A ₈ = −2.25267 × 10 ⁻⁶ ,
A ₁₀ = 1.54591 × 10 ⁻⁷
Aspherical surface: 17th surface K = 0.0,
A ₄ = −5.88625 × 10 ⁻⁵ ,
A ₆ = 1.08911 × 10 ⁻⁵ ,
A ₈ = −4.32420 × 10 ⁻⁷ ,
A ₁₀ = 7.334514 × 10 ⁻⁹
The variable distance DA between the first lens group G1 and the second lens group G2, the variable distance DB between the second lens group G2 and the aperture stop AD, and the variable distance between the aperture stop AD and the third lens group G3. The distance DC, the variable distance DD between the third lens group G3 and the fourth lens group G4, and the variable distance DE between the fourth lens group G4 and the various filters FM are as shown in the following table along with zooming. Can be changed.

The values of conditional expressions (1) to (11) of the zoom lens according to Example 2 described above are as follows:
(1) n _d = 1.59282
(2) ν _d = 68.63
(3) P _{g, F} − (− 0.001802 × ν _d +0.6483)
= 0.0195 ... HOYA FCD505
(4) F _A = 460 ... HOYA FCD505
(5) f _ap / f _W = 7.75
(6) | r _3R | / f _W = 0.885
_{(7) X 1 / f T} = 0.335
(8) X ₃ / f _T = 0.245
(9) | f ₂ | / f ₃ = 0.716
(10) f ₁ / f _W = 6.06
(11) d _SW / f _T = 0.129
Thus, conditional expressions (1) to (11) are satisfied.
8, FIG. 9, and FIG. 10 show aberration diagrams of spherical aberration, astigmatism, distortion, and coma aberration at the wide-angle end, intermediate focal length, and telephoto end, respectively, in Example 2.

FIG. 3 schematically shows a lens configuration of a zoom lens according to Embodiment 3 of the present invention and a zoom locus associated with zooming from the wide-angle end to the telephoto end through a predetermined intermediate focal length, and FIG. (B) is a schematic cross-sectional view at a predetermined intermediate focal length, and (c) is a schematic cross-sectional view at the telephoto end. In FIG. 3 showing the arrangement of the lens groups of Example 3, the left side is the object side.
The zoom lens shown in FIG. 3 includes, in order from the object side along the optical axis, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a positive refractive power. And a fourth lens group G4 having a positive refractive power, and an aperture stop AD is disposed between the second lens group G2 and the third lens group G3. In this case, the first lens group G1 includes a first lens E1, a second lens E2, and a third lens E3, and the second lens group G2 includes a fourth lens E4, a fifth lens E5, and a sixth lens. E6, the third lens group G3 has a seventh lens E7, an eighth lens E8 and a ninth lens E9, and the fourth lens group G4 has a tenth lens E10. Become.

The first lens group G1 to the fourth lens group G4 are each supported by a common support frame or the like appropriate for each group, and operate simultaneously for each group during zooming or the like. Works independently. FIG. 3 also shows the surface number of each optical surface. Note that each reference symbol in FIG. 3 is also used independently for each embodiment in order to avoid complication of explanation due to an increase in the number of digits of the reference symbol. Therefore, a reference symbol common to the drawings according to the other embodiments. Even if attached, they are not necessarily a common configuration with other embodiments.
During zooming from the wide-angle end to the telephoto end, all the first lens group G1 to the fourth lens group G4 move, and the distance between the first lens group G1 and the second lens group G2 increases. The distance between the second lens group G2 and the third lens group G3 decreases, and the distance between the third lens group G3 and the fourth lens group G4 increases.
The first lens group G1 includes, in order from the object side, a first lens E1 composed of a negative meniscus lens having a convex surface facing the object side, a second lens E2 composed of a positive meniscus lens having a convex surface facing the object side, and an object A positive meniscus lens having a convex surface on the side and a third lens E3 made of an aspherical lens forming an aspherical surface on the image surface side is disposed. The two lenses of the first lens E1 and the second lens E2 are closely bonded to each other and bonded together to form a cemented lens composed of two lenses.

The second lens group G2 is a negative meniscus lens having a convex surface directed toward the object side sequentially from the object side, and a fourth lens E4 including an aspheric lens forming an aspheric surface on the object side, and an image A fifth lens E5 composed of a biconvex positive lens having a stronger convex surface on the side, and a negative meniscus lens having a convex surface on the image side, and an aspheric lens forming an aspheric surface on the image side. Six lenses E6 are arranged. The two lenses, the fifth lens E5 and the sixth lens E6, are closely bonded to each other and bonded together to form a cemented lens composed of two lenses.
The aperture stop AD is interposed between the second lens group G2 and the third lens group G3.
The third lens group G3 has, from the object side, a seventh lens E7 which is a positive lens having a biconvex shape with a strong convex surface facing the object side and aspheric surfaces on both sides, and a strong convex surface on the object side. An eighth lens E8 composed of a biconvex positive lens and a ninth lens E9 composed of a biconcave negative lens having a stronger concave surface on the image side are disposed. The two lenses of the eighth lens E8 and the ninth lens E9 are closely bonded to each other and joined together to form a cemented lens composed of two lenses.
The fourth lens group G4 comprises solely a tenth lens E10 consisting of a biconvex lens with the strong convex surface facing the image surface side and the object side aspherical.

That is, the third embodiment has substantially the same configuration as that of the second embodiment described above. Also in this case, as shown in FIG. 3, the first lens group G1 and the third lens group G3 monotonously move from the image side to the object side in accordance with the zooming from the wide angle end to the telephoto end. The second lens group G2 moves substantially monotonically from the object side to the image side, and the fourth lens group G4 moves along a locus convex toward the object side.
In Example 3, the focal length f, F number F, and half angle of view ω of the entire optical system are f = 5.07 to 34.45 and F = 3.44 to 5.57, ω, respectively, by zooming. = Varies between 39.77 and 6.81. The optical characteristics of each optical element are as shown in the following table.

Also in Table 5, the optical surfaces of the fourth surface, the sixth surface, the tenth surface, the twelfth surface, the thirteenth surface, and the seventeenth surface marked with “*” are aspherical surfaces. The parameters of each aspheric surface are as follows.
Aspheric parameters Aspheric surface: 4th surface K = 0.0,
A ₄ = −2.61959 × 10 ⁻⁶ ,
A ₆ = −4.61000 × 10 ⁻⁸ ,
A ₈ = 4.102097 × 10 ⁻¹⁰ ,
A ₁₀ = −2.83406 × 10 ⁻¹²
Aspheric surface; 6th surface K = 0.0,
A ₄ = 4.669989 × 10 ⁻⁵ ,
A ₆ = −6.000298 × 10 ⁻⁶ ,
A ₈ = 2.85972 × 10 ⁻⁷ ,
A ₁₀ = −4.667475 × 10 ⁻⁹ ,
A ₁₂ = −8.207307 × 10 ⁻¹¹ ,
A ₁₄ = 2.46454 × 10 ⁻¹²

Aspheric surface: 10th surface K = 0.0,
A ₄ = −5.17867 × 10 ⁻⁴ ,
A ₆ = −9.91338 × 10 ⁻⁶ ,
A ₈ = −2.02961 × 10 ⁻⁷ ,
A ₁₀ = −5.3862 × 10 ⁻⁸
Aspherical surface; twelfth surface K = 0.0,
A ₄ = −7.44563 × 10 ⁻⁴ ,
A ₆ = 1.45957 × 10 ⁻⁵ ,
A ₈ = −1.41743 × 10 ⁻⁶ ,
A ₁₀ = 1.11141 × 10 ⁻⁷

Aspheric surface: 13th surface K = 0.0,
A ₄ = 7.0916 × 10 ⁻⁴ ,
A ₆ = 2.59719 × 10 ⁻⁵ ,
A ₈ = −2.44987 × 10 ⁻⁶ ,
A ₁₀ = 1.776570 × 10 ⁻⁷
Aspherical surface: 17th surface K = 0.0,
A ₄ = −2.49031 × 10 ⁻⁵ ,
A ₆ = 6.74925 × 10 ⁻⁶ ,
A ₈ = −2.886346 × 10 ⁻⁷ ,
A ₁₀ = 4.04476 × 10 ⁻⁹
The variable distance DA between the first lens group G1 and the second lens group G2, the variable distance DB between the second lens group G2 and the aperture stop AD, and the variable distance between the aperture stop AD and the third lens group G3. The distance DC, the variable distance DD between the third lens group G3 and the fourth lens group G4, and the variable distance DE between the fourth lens group G4 and the various filters FM are as shown in Table 6 along with zooming. Can be changed.

FIGS. 11, 12, and 13 show aberration diagrams of spherical aberration, astigmatism, distortion, and coma aberration at the wide-angle end, intermediate focal length, and telephoto end, respectively, in Example 3.
The values of conditional expressions (1) to (11) of the zoom lens according to Example 3 described above are as follows:
(1) n _d = 1.55332
(2) ν _d = 71.68
(3) P _{g, F} − (− 0.001802 × ν _d +0.6483)
= 0.0211 ... HOYA M-FCD500
(4) F _A = 430 ... HOYA M-FCD500
(5) f _ap / f _W = 9.88
(6) | r _3R | / f _W = 0.970
_{(7) X 1 / f T} = 0.335
(8) X ₃ / f _T = 0.231
(9) | f ₂ | / f ₃ = 0.713
(10) f ₁ / f _W = 6.26
(11) d _SW / f _T = 0.142
Thus, the conditional expressions (1) to (11) are satisfied.

FIG. 4 schematically shows a lens configuration of a zoom lens according to Embodiment 4 of the present invention and a zoom locus associated with zooming from the wide-angle end to the telephoto end through a predetermined intermediate focal length. (B) is a schematic cross-sectional view at a predetermined intermediate focal length, and (c) is a schematic cross-sectional view at the telephoto end. In FIG. 4 showing the arrangement of the lens groups of Example 4, the left side is the object side.
The zoom lens shown in FIG. 4 includes a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a positive refractive power in order from the object side along the optical axis. And a fourth lens group G4 having a positive refractive power, and an aperture stop AD is disposed between the second lens group G2 and the third lens group G3. In this case, the first lens group G1 includes a first lens E1, a second lens E2, and a third lens E3, and the second lens group G2 includes a fourth lens E4, a fifth lens E5, and a sixth lens. E6, the third lens group G3 has a seventh lens E7, an eighth lens E8 and a ninth lens E9, and the fourth lens group G4 has a tenth lens E10. Become.

The first lens group G1 to the fourth lens group G4 are each supported by a common support frame or the like appropriate for each group, and operate simultaneously for each group during zooming or the like. Works independently. FIG. 4 also shows the surface number of each optical surface. Note that each reference symbol in FIG. 4 is also used independently for each embodiment in order to avoid complication of explanation due to an increase in the number of digits of the reference symbol. Therefore, a reference symbol common to the drawings according to the other embodiments. Even if attached, they are not necessarily a common configuration with other embodiments.
During zooming from the wide-angle end to the telephoto end, all the first lens group G1 to the fourth lens group G4 move, and the distance between the first lens group G1 and the second lens group G2 increases. The distance between the second lens group G2 and the third lens group G3 decreases, and the distance between the third lens group G3 and the fourth lens group G4 increases.
The first lens group G1 includes, in order from the object side, a first lens E1 composed of a negative meniscus lens having a convex surface facing the object side, a second lens E2 composed of a positive meniscus lens having a convex surface facing the object side, and an object A positive meniscus lens having a convex surface on the side and a third lens E3 made of an aspherical lens forming an aspherical surface on the object side is disposed. The two lenses of the first lens E1 and the second lens E2 are closely bonded to each other and bonded together to form a cemented lens composed of two lenses.

The second lens group G2 is a negative meniscus lens having a convex surface directed toward the object side sequentially from the object side, and a fourth lens E4 including an aspheric lens forming an aspheric surface on the object side, and an image A fifth lens E5 composed of a biconvex positive lens having a stronger convex surface on the side, and a negative meniscus lens having a convex surface on the image side, and an aspheric lens forming an aspheric surface on the image side. Six lenses E6 are arranged. The two lenses, the fifth lens E5 and the sixth lens E6, are closely bonded to each other and bonded together to form a cemented lens composed of two lenses.
The aperture stop AD is interposed between the second lens group G2 and the third lens group G3.
The third lens group G3 is composed of a biconvex positive lens having a biconvex shape with a strong convex surface directed toward the object side and an aspheric object side surface, and a stronger convex surface on the object side. An eighth lens E8 composed of a biconvex positive lens facing the lens and a ninth lens E9 composed of a biconcave negative lens facing a strong concave surface on the image side. The two lenses of the eighth lens E8 and the ninth lens E9 are closely bonded to each other and joined together to form a cemented lens composed of two lenses.
The fourth lens group G4 comprises solely a tenth lens E10 consisting of a biconvex lens with the strong convex surface facing the image side and an aspherical surface on the object side.

That is, the fourth embodiment has a four-group configuration different from the first embodiment described above. Also in this case, as shown in FIG. 4, the first lens group G1 and the third lens group G3 monotonously move from the image side to the object side with the zooming from the wide-angle end to the telephoto end. The second lens group G2 moves along a locus convex toward the image side, and the fourth lens group G4 moves along a locus convex toward the object side.
In Example 4, the focal length f, F number F, and half angle of view ω of the entire optical system are f = 5.06 to 34.50, F = 3.49 to 5.67, ω, respectively, by zooming. It varies in the range of = 39.85 to 6.77. The optical characteristics of each optical element are as shown in the following table.

In Table 7, the optical surfaces of the fourth surface, the sixth surface, the tenth surface, the twelfth surface, and the seventeenth surface marked with “*” are aspherical surfaces. The parameters are as follows:
Aspheric parameters Aspheric surface: 4th surface K = 0.0,
A ₄ = −2.193930 × 10 ⁻⁶ ,
A ₆ = −5.668815 × 10 ⁻⁸ ,
A ₈ = 5.09447 × 10 ⁻¹⁰ ,
A ₁₀ = −3.52370 × 10 ⁻¹²
Aspheric surface; 6th surface K = 0.0,
A ₄ = 6.998920 × 10 ⁻⁵ ,
A ₆ = −6.551267 × 10 ⁻⁶ ,
A ₈ = 3.05288 × 10 ⁻⁷ ,
A ₁₀ = −4.99734 × 10 ⁻⁹ ,
A ₁₂ = −7.66420 × 10 ⁻¹¹ ,
A ₁₄ = 2.31453 × 10 ⁻¹²

Aspheric surface: 10th surface K = 0.0,
A ₄ = −4.84852 × 10 ⁻⁴ ,
A ₆ = −1.06293 × 10 ⁻⁵ ,
A ₈ = 1.65811 × 10 ⁻⁸ ,
A ₁₀ = −5.727223 × 10 ⁻⁸
Aspherical surface; twelfth surface K = 0.0,
A ₄ = −7.1335 × 10 ⁻⁴ ,
A ₆ = 1.119186 × 10 ⁻⁵ ,
A ₈ = −1.35662 × 10 ⁻⁶ ,
A ₁₀ = 1.20507 × 10 ⁻⁷

Aspheric surface: 13th surface K = 0.0,
A ₄ = 6.51905 × 10 ⁻⁴ ,
A ₆ = 2.55564 × 10 ⁻⁵ ,
A ₈ = −2.41458 × 10 ⁻⁶ ,
A ₁₀ = 1.89127 × 10 ⁻⁷
Aspherical surface: 17th surface K = 0.0,
A ₄ = −9.004702 × 10 ⁻⁵ ,
A ₆ = 9.88666 × 10 ⁻⁶ ,
A ₈ = −4.20068 × 10 ⁻⁷ ,
A ₁₀ = 6.42194 × 10 ⁻⁹
The variable distance DA between the first lens group G1 and the second lens group G2, the variable distance DB between the second lens group G2 and the aperture stop AD, and the variable distance between the aperture stop AD and the third lens group G3. The distance DC, the variable distance DD between the third lens group G3 and the fourth lens group G4, and the variable distance DE between the fourth lens group G4 and the various filters FM are as shown in the following table along with zooming. Can be changed.

The values of conditional expressions (1) to (11) of the zoom lens according to Example 4 described above are as follows:
(1) n _d = 1.55332
(2) ν _d = 71.68
(3) P _{g, F} − (− 0.001802 × ν _d +0.6483)
= 0.0211 ... HOYA M-FCD500
(4) F _A = 430 ... HOYA M-FCD500
(5) f _ap / f _W = 10.43
(6) | r _3R | / f _W = 0.959
_{(7) X 1 / f T} = 0.328
(8) X ₃ / f _T = 0.241
(9) | f ₂ | / f ₃ = 0.718
(10) f ₁ / f _W = 6.26
(11) d _SW / f _T = 0.137
Thus, conditional expressions (1) to (11) are satisfied.
FIGS. 14, 15 and 16 show aberration diagrams of spherical aberration, astigmatism, distortion and coma aberration at the wide-angle end, intermediate focal length and telephoto end, respectively, in Example 4.
[Embodiment]
Next, referring to FIGS. 17 to 19 for an embodiment of the present invention in which the zoom lens according to the present invention as shown in the first to fourth embodiments described above is employed as a photographing optical system to constitute a camera. To explain. FIG. 17 is a perspective view showing the external appearance of the camera as seen from the front side that is the object, that is, the subject side. Of these, (a) shows a state in which the taking lens is retracted in the body of the camera, (b ) Shows a state in which the photographing lens protrudes from the camera body. FIG. 18 is a perspective view showing the appearance of the camera viewed from the back side, which is the photographer side, and FIG. 19 is a block diagram showing the functional configuration of the camera. Although a camera is described here, a camera in which a camera function is incorporated in a personal digital assistant such as a so-called PDA (personal data assistant) or a mobile phone has recently appeared. Such a portable information terminal device also includes substantially the same function and configuration as a camera although the appearance is slightly different. Even if the zoom lens according to the present invention is adopted in such a portable information terminal device, Good.
As shown in FIGS. 17 and 18, the camera 1 includes a photographing lens 2, a shutter button 3, a zoom lever 4, a finder 5, a strobe 6, a liquid crystal monitor 7, an operation button 8, a power switch 9, a memory card slot, and a communication card. A slot 10 and the like are provided.
Further, as shown in FIG. 19, the camera also includes a light receiving element 12, a signal processing device 13, an image processing device 14, a central processing unit (CPU) 15, a semiconductor memory 16, a communication card 17 and the like.

The camera 1 includes a photographing lens 2 and a light receiving element 12 as an area sensor such as a CCD (charge coupled device) imaging element, and is an object to be photographed formed by the photographing lens 2 that is a photographing optical system, that is, An image of the subject is read by the light receiving element 12. The photographing lens 2 of the camera 1, Ru using the zoom lens according to the present invention as described in Examples 1-4.
The output of the light receiving element 12 is processed by the signal processing device 13 controlled by the central processing unit 15 and converted into digital image information. The image information digitized by the signal processing device 13 is subjected to predetermined image processing in the image processing device 14 which is also controlled by the central processing unit 15 and then recorded in the semiconductor memory 16 such as a nonvolatile memory. In this case, the semiconductor memory 16 may be a memory card loaded in the memory card slot 10 or a semiconductor memory 16 built in the camera body. On the liquid crystal monitor 7, an image being photographed can be displayed, and an image recorded in the semiconductor memory 16 can be displayed. The image recorded in the semiconductor memory 16 can also be transmitted to the outside via a communication card 17 or the like loaded in the communication card slot 10.

When the camera is carried, the photographic lens 2 is in the retracted state and buried in the body of the camera as shown in FIG. 17A. When the user operates the power switch 9 to turn on the power, FIG. (B), the lens barrel is extended and protrudes from the camera body. At this time, in the lens barrel of the photographing lens 2, the optical systems of the respective groups constituting the zoom lens are, for example, arranged at the wide-angle end. By operating the zoom lever 4, the arrangement of the optical systems of the respective groups is arranged. Is changed, and the zooming operation to the telephoto end can be performed. It is desirable that the optical system of the finder 5 is also scaled in conjunction with the change in the angle of view of the photographic lens 2.
In many cases, focusing is performed by half-pressing the shutter button 3. Focusing in the zoom lens according to the present invention (the zoom lens defined in claims 1 to 9 or shown in the first to fourth embodiments) is performed by moving the first lens group G1 or the third lens. This can be done by moving the group G3 or moving the light receiving element. When the shutter button 3 is further pushed down to the fully depressed state, photographing is performed, and then the processing as described above is performed.

When the image recorded in the semiconductor memory 16 is displayed on the liquid crystal monitor 7 or transmitted to the outside via the communication card 17 or the like, the operation button 8 is operated in a predetermined manner. The semiconductor memory 16 and the communication card 17 are used by being loaded into dedicated or general-purpose slots such as the memory card slot and the communication card slot 10, respectively.
When the photographing lens 2 is in the retracted state, each group of zoom lenses does not necessarily have to be aligned on the optical axis. For example, if at least one of the second lens group G2 and the third lens group G3 is retracted from the optical axis and retracted in parallel with the other lens groups when retracted, the camera can be made thinner. Can be realized.
As described above, in the above-described camera or portable information terminal device, it is possible to use the photographing lens 2 configured using the zoom lens as shown in the first to fourth embodiments as a photographing optical system. it can. Therefore, it is possible to realize a small camera or portable information terminal device with high image quality using a light receiving element of 10 million to 15 million pixel class.

G1 1st lens group G2 2nd lens group G3 3rd lens group G4 4th lens group E1-E11 1st lens-11th lens AD Aperture stop FM Various filters FP Imaging surface

Japanese Patent Laid-Open No. 08-248317 JP 2001-194590 A JP 2004-333768 A JP 2008-026837 A

Claims (11)

In order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens having a positive refractive power consists of a group, upon zooming from the wide-angle end to the telephoto end, the distance between the second lens group and the first lens group increases, a distance between the third lens group and the second lens group decreases A zoom lens in which the distance between the third lens group and the fourth lens group is increased so that the first lens group and the third lens group are positioned closer to the object side at the telephoto end than at the wide angle end. In
The first lens group has two positive lenses;
A negative lens having a strong concave surface facing the image side is disposed on the most image side of the third lens group, and the following conditional expression is satisfied:
0.6 <| r _3R | / f _W <1.3
An aperture stop is disposed between the second lens group and the third lens group, and the first lens group has a positive lens made of optical glass, and the positive lens satisfies the following conditional expression: Zoom lens characterized by.
1.52 _<n d _<1.62
65.0 <ν _d <75.0
0.015 <P _{g, F} − (− 0.001802 × ν _d +0.6483) <0.050
However, r _3R is, the curvature of the most image side surface of the third lens group, f _w is the focal length of the wide-angle end, n _d is the refractive index of the optical glass constituting the positive lens, [nu _d represents the Abbe number of the optical glass constituting the positive lens, and P _{g, F} represents the partial dispersion ratio of the optical glass constituting the positive lens.
_Here, P _{g, F =} a _{(n g -n F) / (} n F -n C), n g, n F, n C , respectively, of the optical glass constituting the positive lens, g line , F-line, C-line refractive index. In order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens having a positive refractive power And a fifth lens group having a positive refracting power, the distance between the first lens group and the second lens group increases upon zooming from the wide-angle end to the telephoto end, and the second lens The distance between the third lens group and the third lens group decreases, the distance between the third lens group and the fourth lens group increases, and the first lens group and the third lens group are at the telephoto end rather than at the wide-angle end. In the zoom lens that moves so that it is located on the object side with
The first lens group has two positive lenses;
A negative lens having a strong concave surface facing the image side is disposed on the most image side of the third lens group, and the following conditional expression is satisfied:
0.6 <| r _3R | / F _W <1.3
An aperture stop is disposed between the second lens group and the third lens group, and the first lens group has a positive lens made of optical glass, and the positive lens satisfies the following conditional expression: Zoom lens characterized by.
1.52 <n _d <1.62
65.0 <ν _d <75.0
0.015 <P _{g, F} − (− 0.001802 × ν _d +0.6483) <0.050
Where r _3R Is the radius of curvature of the most image-side surface of the third lens group, f _w Is the focal length of the entire system at the wide-angle end, n _d Is the refractive index of the optical glass constituting the positive lens, ν _d Is the Abbe number of the optical glass constituting the positive lens, P _{g, F} Represents the partial dispersion ratio of the optical glass constituting the positive lens.
Where P _{g, F} = (N _g -N _F ) / (N _F -N _C ) And n _g , N _F, n _C Are the refractive indices of the optical glass constituting the positive lens with respect to g-line, F-line, and C-line, respectively. The zoom lens according to claim 1 or 2 ,
A zoom lens satisfying the following conditional expression:
30 <F _A <500
However, F _A represents the degree of wear of the optical glass constituting the positive lens of the first lens group that satisfies the conditional expression of claim 1. The zoom lens according to any one of claims 1 to 3 ,
A zoom lens satisfying the following conditional expression:
5.0 <f _ap / f _W <15.0
However, f _ap represents the focal length of the positive lens made of the optical glass of the first lens group that satisfies the conditional expression of claim 1, and f _W represents the focal length of the entire system at the wide angle end. The zoom lens according to any one of claims 1 to 4 ,
2. The zoom lens according to claim 1, wherein at least one of the positive lenses in the first lens group has an aspheric surface, and the positive lens having the aspheric surface satisfies the conditional expression according to claim 1. The zoom lens according to any one of claims 1 to 5 ,
A zoom lens satisfying the following conditional expression:
_{0.20 <X 1 / f T <} 0.45
However, X ₁ is the total amount of movement of the first lens group when changing magnification from the wide-angle end to the telephoto end, f _T represents the focal length of the entire system at the telephoto end. The zoom lens according to any one of claims 1 to 6 ,
A zoom lens satisfying the following conditional expression:
0.15 <X ₃ / f _T <0.40
However, X ₃ represents the total amount of movement of the third lens group when changing magnification from the wide-angle end to the telephoto end. The zoom lens according to any one of claims 1 to 7 ,
A zoom lens satisfying the following conditional expression:
0.50 <| f ₂ | / f ₃ <0.85
However, f ₂ is the focal length of the second lens group, f ₃ represents the focal length of the third lens group. The zoom lens according to any one of claims 1 to 8 ,
A zoom lens satisfying the following conditional expression:
5.0 <f ₁ / f _W <8.0
Here, f ₁ represents the focal length of the first lens group. The zoom lens according to claims 1 or one of claims 9, a camera, characterized in that it comprises a photographic optical system. The zoom lens according to claims 1 or one of claims 9, a portable information terminal apparatus, characterized in that it comprises a photographic optical system of a camera functional part.

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