JP4653456B2 - Zoom lens and information device - Google Patents

Description

  The present invention relates to a zoom lens and an information device.

  In recent years, digital cameras that are remarkably widespread are required to have higher performance and smaller size, and zoom lenses used as photographing lenses are also required to have both higher performance and smaller size. In terms of miniaturization, the zoom lens must first reduce the overall lens length (distance from the lens surface closest to the object side to the image plane) when used, and the lens groups can be stored with a reduced thickness. Minimizing the overall length is also an important factor in achieving downsizing.

  In consideration of application to a high-end digital camera, it is necessary for the performance enhancement of the zoom lens to have a resolving power corresponding to an image sensor of at least 5 to 10 million pixels over the entire zoom range. It is also important to reduce distortion, which tends to increase especially at the wide-angle end, and it is desirable that the F number at the telephoto end is as small as 4 (bright).

  Furthermore, there are many users who desire a wider 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. A half angle of view of 38 degrees corresponds to a focal length of 28 mm in terms of a 35 mm silver salt camera (so-called Leica version).

There are many types of zoom lenses for digital cameras. However, when the number of lens groups is five or more, it is difficult to reduce the total thickness of the lens groups, and it is not suitable for miniaturization.
Well known as a type suitable for high zooming and large aperture, in order from the object side, a first lens group having a positive focal length, a second lens group having a negative focal length, a positive A lens unit having a third lens group having a focal length and a fourth lens group having a positive focal length is widely known.

Patent Documents 1 and 2 describe such a four-group configuration of positive, negative, positive, and positive in which the third lens group is composed of four lenses as in the zoom lens of the present invention.
The zoom lenses described in Patent Publications 1 and 2 are suitable for video cameras. In a specific embodiment, the zoom ratio is 8 times or more (Patent Document 1), 11 times or more (Patent Document 2). Although it is large, the half angle of view at the wide-angle end is about 25 degrees (Patent Document 1) and about 31 degrees (Patent Document 2), and the 38 degrees or more required for a digital camera can hardly be expected. . In the specific examples described in Patent Documents 1 and 2, distortion at the wide-angle end is as large as about 8%, which is insufficient as a zoom lens for high-performance digital camera specifications.

Japanese Patent No. 2859734 Japanese Patent No. 3008380

  In view of the above-described circumstances, the present invention is particularly suitable as a zoom lens for a small and high-performance digital camera. The half angle of view at the wide angle end: 38 degrees or more, the zoom ratio: about 3 times, and the F number at the telephoto end: 4 Distortion at the wide-angle end: within 3%, realization of a zoom lens capable of realizing a resolution corresponding to an image sensor of about 5 million to 10 million pixels, and realization of an information device using such a zoom lens Is an issue.

  The zoom lens according to 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, an aperture stop, a third lens group having a positive refractive power, a positive A fourth lens group having a refractive power is arranged, and when changing the magnification from the wide-angle end to the telephoto end, the distance between the first lens group and the second lens group increases, and the second lens group and the third lens group A zoom lens in which at least the first lens group and the third lens group move toward the object side so that the distance decreases and the distance between the third lens group and the fourth lens group increases.

The zoom lens according to claim 1 is characterized by the following points.
That is, the third lens group has a configuration in which four lenses of a positive lens, a negative lens, a positive lens, and a positive lens are arranged in the above order from the object side.
Then, the refractive index of the negative lens of the third lens group: N ₃₂ and Abbe number: [nu _32, the refractive index of the positive lens disposed adjacent to the image side of the negative lens: N ₃₃ and Abbe number: [nu ₃₃ is ,conditions:
_{(1) 0.15 <(N 32} -N 33) <0.40
(2) 25 <(ν ₃₃ −ν ₃₂ ) <50
Satisfied .

The zoom lens according to claim 1 is a distance from the vertex of the object side surface of the positive lens closest to the object side of the third lens group to the vertex of the image side surface of the negative lens of the third lens group: L _PN The thickness of the third lens group in the optical axis direction: L ₃ But the condition:
(4) 0.50 <(L _PN / L ₃ ) <0.75
Is preferably satisfied (claim 2).

The zoom lens according to claim 3, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, an aperture stop, a third lens group having a positive refractive power, A fourth lens group having a positive refractive power is disposed, and the distance between the first lens group and the second lens group is increased upon zooming from the wide-angle end to the telephoto end, and the second lens group and the third lens are increased. In the zoom lens in which at least the first lens group and the third lens group move toward the object side so that the distance between the groups decreases and the distance between the third lens group and the fourth lens group increases, the third lens group is A positive lens, a negative lens, a positive lens, and a positive lens are arranged in the above order from the object side, and the third lens group is negative from the apex of the object side surface of the positive lens closest to the object side in the third lens group. the distance to the vertex of the image side surface of the lens: L _PN, the third lens group The axial thickness: _{L 3} is the condition:
(4) 0.50 <(L _PN / L ₃ ) <0.75
It is characterized by satisfying .
The zoom lens according to any one of claims 1 to 3, wherein the third lens group has, in order from the object side, a positive lens having a large curvature surface facing the object side and a large curvature surface facing the image side. It is preferable that the negative lens, a positive meniscus lens having a convex surface facing the object side, and a positive lens having a large curvature surface facing the object side are arranged (claim 4) .
In the zoom lens according to claim 4, the radius of curvature of the object side surface of the positive lens closest to the object side in the third lens group : r _31F , the radius of curvature of the image side surface of the negative lens of the third lens group: r _32R , The curvature radius of the image side surface of the positive meniscus lens arranged adjacent to the image side of the negative lens in the lens group: r _33R , the maximum image height: Y ′, the condition:
(3) 1.80 <{(1 / r _31F ) + (1 / r _32R ) + (1 / r _33R )} × Y ′ <2.60
It is preferable to satisfy (Claim 5) .

The zoom lens according to claim 6, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, an aperture stop, a third lens group having a positive refractive power, A fourth lens group having a positive refractive power is disposed, and the distance between the first lens group and the second lens group is increased upon zooming from the wide-angle end to the telephoto end, and the second lens group and the third lens are increased. In the zoom lens in which at least the first lens group and the third lens group move toward the object side so that the distance between the groups decreases and the distance between the third lens group and the fourth lens group increases, the third lens group is In order from the object side, a positive lens with a large curvature on the object side, a negative lens with a large curvature on the image side, a positive meniscus lens with a convex surface on the object side, and a surface with a large curvature on the object side The fourth lens group is composed of four positive lenses facing the third lens group. Most of curvature of the object side surface on the object side of the positive lens radius: r _31F , Radius of curvature of image side surface of negative lens of third lens group: r _32R The radius of curvature of the image side surface of the positive meniscus lens arranged adjacent to the image side of the negative lens of the third lens group: r _33R Maximum image height: Y ′, conditions:
  (3) 1.80 <{(1 / r _31F ) + (1 / r _32R ) + (1 / r _33R )} × Y ′ <2.60
It is characterized by satisfying.

The third lens group in the zoom lens according to any one of claims 1 to 6 includes, in order from the object side, a positive lens having a large curvature surface facing the object side and a negative lens having a large curvature surface facing the image side. A three-group four-lens configuration including a lens, a positive meniscus lens cemented to the negative lens, and a positive lens having a surface with a large curvature facing the object side is preferable .

The zoom lens according to any one of claims 1 to 7, wherein “the curvature of the image side surface of the negative lens of the third lens group is the largest curvature among all the surfaces of the third lens group” is preferable. (Claim 8).

In the zoom lens according to any one of claims 1 to 8, it is preferable that the “most object side surface and most image side surface” of the third lens group be aspherical surfaces (claim 9).

As a reference technique, the third lens group includes at least three positive lenses and at least one negative lens, and the most object side surface and the most image side surface of the third lens group are aspherical surfaces. It is conceivable to arrange “two positive lenses adjacent to each other” on the most image side of the third lens group .

The first lens group in the zoom lens according to any one of claims 1 to 9, wherein “the configuration includes at least one negative lens and at least one positive lens, and the negative lens is disposed on the object side”. (Claim 10)

In the case of the tenth aspect , the first lens group can be composed of “two lenses in order from the object side, 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” ( Claim 11 ).

The second lens group in the zoom lens according to any one of claims 1 to 11 "in order from the object side, composed of three negative lenses, a negative lens, a positive lens" It is preferable that the (claim 12) in this case, it is possible to join the second lens and the third lens from the object side in the first lens group (claim 13).

It is preferable that the fourth lens group in the zoom lens according to any one of claims 1 to 13 is composed of “one positive lens” ( claim 14 ). In this case, “when focusing to a finite distance, it is preferable to configure only the fourth lens group as "move (claim 15).

The zoom lens described above is to constitute the first to fourth lens groups so that the half angle of view at the wide angle end is 38 degrees or more and the zoom ratio is about 3 times, and the F number at the telephoto end is about 4. preferable.

An information apparatus according to the present invention is characterized in that the zoom lens according to any one of claims 1 to 15 "has as a photographing optical system" ( claim 16 ). The information device according to claim 16 can be implemented as a silver salt camera, but as an information device such as a digital camera or a video camera in which an “object image by a zoom lens is formed on a light receiving surface of an image sensor”. The present invention can also be implemented as an “information device having a photographing function” ( claim 17 ).

The information device according to claim 17 may be an information device having “the number of pixels of the image sensor is 5 million pixels or more” ( claim 18 ). The information device according to claim 17 or 18 can be implemented as a “portable information terminal device” ( claim 19 ).

The following is supplementary explanation.
As in the zoom lens of the present invention, a “zoom lens composed of four lens groups of positive, negative, positive, and positive” is generally a so-called “variator” in which the second lens group bears the main zooming action. Configured as

  However, in the zoom lens according to the present invention, the third lens group also shares the zooming function, thereby reducing the burden on the second lens group and correcting for “aberration correction that becomes difficult with widening and high zooming. The degree of freedom of correction is secured.

  Further, when zooming from the wide-angle end to the telephoto end, the first lens unit is moved to the object side, so that the height of the light beam passing through the first lens unit is reduced at the wide-angle end, and the “first with widening of the angle” is set. In addition to suppressing the increase in the size of the lens group, at the telephoto end, “a certain distance between the first lens group and the second lens group is ensured” so that the F number on the long focal point side does not increase.

During zooming from the wide-angle end to the telephoto end, the first lens group and the third lens group move monotonously toward the object side, the distance between the first lens group and the second lens group increases, and the second lens and the third lens group increase. The distance from the lens group becomes smaller, the magnification of the second lens group and the third lens group both increase, and the zooming action is shared with each other.
The second lens group can be “fixed with respect to the image plane” or can be “moved so that the telephoto end is positioned closer to the image side than the wide-angle end”. Also, when zooming from the wide-angle end to the telephoto end, it is possible to “draw a U-turn trajectory that moves once to the image side and then moves to the object side”. By such movement of the second lens group, it is possible to “assign to each group with a high degree of freedom” the functions of zooming and image plane position compensation.

  Further, the fourth lens group can be “moved so that it is positioned closer to the image side than the wide-angle end at the telephoto end”. Due to such movement of the fourth lens group, when changing the magnification from the wide-angle end to the telephoto end, it becomes a “direction in which the magnification of the fourth lens group also increases”, and the zooming action can be borne. Can be effectively scaled within. " Of course, the fourth lens group may be “fixed upon zooming”.

The greatest feature of the zoom lens according to claim 1 resides in the configuration of the third lens group.
That is, in the zoom lens according to the first aspect, the third lens group is configured by arranging four lenses “a positive lens, a negative lens, a positive lens, and a positive lens in order from the object side”.

  Due to the fact that the aperture stop is disposed on the object side of the third lens group, off-axis rays pass through a position farther from the optical axis in the third lens group, as “the lens surface on the image side farther from the aperture stop”. “Involvement in correction of off-axis aberration” is deepened. The power arrangement of the third lens group is “a symmetrical arrangement in which positive power is arranged on both sides of the negative power”, but two “image side positive powers” that are deeply involved in the correction of off-axis aberrations. By dividing into lenses, the degree of freedom of correction increases, and good correction of off-axis aberrations becomes possible.

5. As in the case of claim 4 , the third lens group is arranged in order from the object side: “a positive lens having a large curvature surface facing the object side, a negative lens having a large curvature surface facing the image side, and a convex surface facing the object side” 4 lenses, a positive meniscus lens facing the surface and a positive lens facing the surface with a large curvature toward the object side, but the "curvature of the object side surface of the most positive lens on the object side" in the third lens group By setting the “curvature of the image side surface of the second negative lens from the object side” to be relatively large, “the necessary amount of aberration is exchanged” on these surfaces, while the third positive lens from the object side is moved to the meniscus By making the shape and giving negative power to the side surface of the image, the negative power in the third lens group is "shared with other than the negative lens", and "excessive aberration occurs on a specific surface" Prevent the entire third lens group and Reduction of reducing the manufacturing error sensitivity of the aberration of Te can both be achieved.

Further, as in the case of claim 7 , the third lens unit is arranged in order from the object side “a positive lens having a surface with a large curvature facing the object side, a negative lens having a surface with a large curvature facing the image side, In addition to the effect of the second aspect, the second negative lens from the object side includes the positive meniscus lens cemented to the lens and the positive lens having a large curvature facing the object side. By joining the third positive lens, the effect of “suppressing assembly eccentricity and reducing assembly man-hours” can be obtained.

In the condition (1) according to claim 1 , if the parameter (N ₃₂ −N ₃₃ ) is smaller than 0.15, it becomes difficult to correct the curvature of field. Conversely, if the parameter (N ₃₂ -N ₃₃ ) is larger than 0.4, a negative meniscus lens is required to be “expensive glass material with a very high refractive index”, resulting in an increase in cost.
The parameter (N ₃₂ -N ₃₃ ) more preferably satisfies the following conditions.
_{(1a) 0.20 <(N 32} -N 33) <0.40.

In the condition (2) according to claim 1 , if the parameter: (ν ₃₃ −ν ₃₂ ) is smaller than 25, “chromatic aberration cannot be sufficiently controlled” and “correction of axial chromatic aberration and correction of lateral chromatic aberration are compatible. To make it difficult. On the other hand, if the parameter: (ν ₃₃ −ν ₃₂ ) is larger than 50, the positive meniscus lens is required to be “an expensive glass material with very small dispersion”, resulting in an increase in cost. The parameter (ν ₃₃ −ν ₃₂ ) more preferably satisfies the following conditions.
(2a) 30 <(ν ₃₃ −ν ₃₂ ) <50.

  The condition (3) according to claim 5 is that the third lens group is: “a positive lens having a surface with a large curvature directed toward the object side, a negative lens having a surface with a large curvature directed toward the image side, in order from the object side; This is a condition for improving curvature of field on the premise that the lens is composed of a positive meniscus lens having a convex surface on the side and a positive lens having a large curvature surface on the object side.

Parameter: {(1 / r _31F ) + (1 / r _32R ) + (1 / r _33R )} × Y ′ is set to a value larger than the lower limit of 1.80, the field curvature of the third lens group is sufficient. Thus, the flatness of the image plane can be maintained over the entire zoom range. However, if the value of this parameter is increased beyond the upper limit of 2.60, the aberration generated on each surface of the third lens group will increase, resulting in increased “aberration exchange” and increased manufacturing error sensitivity. .

Note that the parameter: {(1 / r _31F ) + (1 / r _32R ) + (1 / r _33R )} × Y ′ preferably satisfies the following conditions.

(3a) 1.95 <{(1 / r _31F ) + (1 / r _32R ) + (1 / r _33R )} × Y ′ <2.45.

The condition (4) described in claims 2 and 3 is a condition for satisfactorily improving spherical aberration, astigmatism, and coma. In the third lens group, the object side surface of the positive lens closest to the object side and the image side surface of the negative lens both have large curvatures, so these surfaces "contribute large aberrations to each other" and contribute most to aberration correction. Yes. In order to perform good aberration correction, the height of the light beam passing through these two surfaces is important.

Parameter: When (L _PN / L ₃ ) is smaller than 0.50, the height of the off-axis chief ray on the image side surface of the negative lens becomes too small, and “the correction of astigmatism and coma is insufficient”. Arise. On the other hand, when the parameter: (L _PN / L ₂ ) is larger than 0.75, the axial marginal ray height on the image side surface of the negative lens becomes too small, resulting in “a case where correction of spherical aberration is insufficient”. The parameter (L _PN / L ₃ ) more preferably satisfies the following conditions.

(4a) 0.55 <(L _PN / L ₂ ) <0.70.

  In order to achieve a better balance between monochromatic aberration and chromatic aberration, as described in claim 7, “the curvature of the image side surface of the negative lens of the third lens group is the highest among all the surfaces of the third lens group. “Big” is better. If there is a “surface having a larger curvature than the image side surface of the negative lens” in the third lens group, it will be difficult to achieve “balance between axial chromatic aberration and lateral chromatic aberration” with good correction of monochromatic aberration.

In order to further correct the monochromatic aberration, it is desirable that “the third lens group has two or more aspheric surfaces”. It is possible to improve the degree of freedom of aberration correction by using the two aspherical surfaces at “locations where the way of light rays are different”, respectively, but in order to perform the most effective aberration correction, it is described in claim 9 . As described above, it is effective that “the most object side surface and the most image side surface of the third lens group are aspherical surfaces”.

  Since the surface on the most object side of the third lens group is in the vicinity of the stop, the on-axis and off-axis light beams pass through almost without separation. Therefore, the aspherical surface provided at this position contributes to correction of “mainly spherical aberration and coma”. On the other hand, since “the most image side surface of the third lens group” is away from the stop, “on-axis and off-axis light beams are separated to some extent” and pass. For this reason, the aspheric surface provided at this position effectively contributes to “correction of astigmatism and the like”. Thus, by using the two aspherical surfaces for the “most object side surface and the most image side surface” of the third lens group, each aspherical surface has a sufficiently different effect, and correction of aberrations is achieved. The degree of freedom increases dramatically.

Preferably , the first lens group has at least one negative lens and at least one positive lens from the object side. More specifically, in order from the object side, 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 ( claim 11 ), or from the object side In order, it is preferable to form a negative meniscus lens having a convex surface facing the object side, a positive lens having a strong convex surface facing the object side, and a positive lens having a strong convex surface facing the object side.

As in claim 12, the second lens group in order from the object side, a negative lens, a negative lens, better to configure three positive lenses, and the second lens from the object side as in claim 13 3 The second lens may be cemented appropriately.
As in the fourteenth aspect , it is desirable that the fourth lens group is composed of a single positive lens. When focusing to a finite distance, the fourth lens group is a method of moving only the fourth lens group as in the fifteenth aspect. The “weight of the object to be moved” may be the smallest. The fourth lens group has a small movement amount at the time of zooming, and has an advantage that “a moving mechanism for zooming and a moving mechanism for focusing can be combined”.

  An aspherical surface is indispensable in order to further advance “miniaturization of the zoom lens” while maintaining good aberration correction, and it is desirable that at least the second lens group has “one or more aspherical surfaces”. If the “most object-side surface” in the second lens group is an aspherical surface, a high effect can be obtained in correcting distortion aberration, astigmatism, etc., which tend to increase as the angle increases.

  As an aspheric lens, optical glass or optical plastic molded (glass molded aspheric surface, plastic molded aspheric surface) or “a thin resin layer is molded on the surface of the glass lens, and the surface is aspherical. Can be used (referred to as hybrid aspherical surface, replica aspherical surface, etc.).

  Although it may be simple in terms of mechanism that the “aperture open diameter” is constant regardless of zooming, it can be accompanied by zooming by making the open diameter of the long focal end larger than that of the short focal end. The change in the F number can be reduced. Further, when it is necessary to reduce the amount of light reaching the image plane, the aperture may be reduced in diameter. It is preferable to reduce the amount of light by inserting an ND filter or the like without greatly changing the aperture diameter, since it is possible to prevent a decrease in resolution due to a diffraction phenomenon.

  As described above, according to the present invention, a “new zoom lens and information device” can be realized. The zoom lens according to the present invention is, as in the following specific examples, “compact, sufficiently corrected for aberrations, capable of dealing with light receiving elements of 5 to 10 million pixels, and distortion aberrations. A zoom lens that is as small as ± 3% within the entire zoom range can be realized. Therefore, by using such a zoom lens, it is possible to realize a “information device such as a digital camera” that is small and has good performance.

  As the best mode for carrying out the invention, four specific examples of zoom lenses will be described below. As illustrated in FIG. 1 representing the first embodiment, in each embodiment, the parallel plate FT disposed on the image plane side of the fourth lens group IV includes various filters such as an optical low-pass filter and an infrared cut filter, Assuming a cover glass (seal glass) of a light receiving element such as a CCD sensor, a transparent parallel plate equivalent to these is shown.

Example 1 is an example of “fixing the second lens unit during zooming”, and Example 4 is an example of “fixing the fourth lens unit during zooming”. In Example 2 and Example 3, all lens groups are moved during zooming.
In all the examples, the maximum image height (Y ′) is 4.70 mm.

The meanings of the symbols in the examples are as follows.
f: Focal length of entire system F: F number ω: Half angle of view R: Radius of curvature D: Surface spacing N _d : Refractive index ν _d : Abbe number K: Conic constant of aspheric surface A ₄ : Fourth-order aspheric coefficient A ₆ : 6th-order aspheric coefficient A ₈ : 8th-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 Aspherical coefficient A ₁₈ : 18th-order aspherical coefficient.

An aspherical surface is defined by the following equation, where C is the reciprocal of the paraxial radius of curvature (paraxial curvature) and H is the height from the optical axis.
X = CH ² / {1 + √ (1- (1 + K) C ² H ² )}
+ A ₄ · H ⁴ + A ₆ · H ⁶ + A ₈ · H ⁸ + A ₁₀ · H ¹⁰ + A ₁₂ · H ^{12
_{+ A 14 · H 14 + A}} 16 · H 16 + A 18 · H 18

f = 5.97 to 17.37, F = 2.87 to 4.01, ω = 38.83 to 14.98
Surface number RDN _d ν _d Remarks
01 28.155 1.20 1.84666 23.80 1st lens
02 15.319 0.64
03 15.782 5.17 1.83481 42.70 Second lens
04 135.423 Variable (A)
05 * 42.414 1.04 1.83481 42.70 3rd lens
06 5.835 3.32
07 -15.059 0.90 1.48749 70.20 4th lens
08 10.548 1.24
09 13.251 1.67 1.84666 23.80 5th lens
10 176.662 Variable (B)
11 ∞ (Aperture) Variable (C)
12 * 8.538 1.78 1.67790 54.90 6th lens
13 -37.800 1.61
14 25.043 3.00 1.84666 23.80 7th lens
15 5.000 1.60 1.58913 61.20 8th lens
16 6.321 0.24
17 7.769 1.77 1.58913 61.15 9th lens
18 * -50.000 variable (D)
19 * 12.436 2.38 1.58913 61.15 10th lens
20 225.974 Variable (E)
21 ∞ 0.90 1.51680 64.20 Various filters
22 ∞
Surfaces marked with “*” in the surface numbers are aspherical.

"Aspherical surface"
5th page
K = 0.0, A ₄ = 1.26782 × 10 ^-4 , A ₆ = 2.47534 × 10 ^-6 , A ₈ = -4.17712 × 10 ^-7 ,
A ₁₀ = 2.00807 × 10 ^-8 , A ₁₂ = -4.18260 × 10 ^-10 , A ₁₄ = 1.41388 × 10 ^-12 ,
A ₁₆ = 7.48396 × 10 ^-14 , A ₁₈ = -8.14824 × 10 ^-16
12th page
K = 0.0, A ₄ = -2.10209 × 10 ^-4 , A ₆ = -5.13296 × 10 ^-6 , A ₈ = 5.484 × 10 ^-7 ,
A ₁₀ = -3.20947 × 10 ^-8
18th page
K = 0.0, A ₄ = 2.92734 × 10 ^-4 , A ₆ = -2.03844 × 10 ^-5 , A ₈ = 2.33939 × 10 ^-6 ,
A ₁₀ = -1.21562 × 10 ^-7
19th page
K = 0.0, A ₄ = -1.94587 × 10 ^-5 , A ₆ = 7.09576 × 10 ^-6 , A ₈ = -1.82438 × 10 ^-7 ,
A ₁₀ = 2.67843 × 10 ^-9 .

"Variable amount"
Short focal end Intermediate focal length Long focal end
f = 5.974 f = 10.190 f = 17.366
A 0.600 4.360 12.418
B 9.526 4.980 2.361
C 1.000 1.000 1.000
D 4.372 9.812 12.429
E 3.132 2.238 2.240.

"Parameter values for each condition"
Condition (1) N ₃₂ -N ₃₃ = 0.258
Condition (2) ν ₃₃ -ν ₃₂ = 37.4
Condition (3) {(1 / r _31F ) + (1 / r _33F ) + (1 / r _33R )} × Y '= 2.23
Condition (4) L _PN / L ₃ = 0.639.

FIG. 1 shows the lens configuration and the position of each lens group at the wide angle end (upper diagram), intermediate focal length (middle diagram), and telephoto end (lower diagram).
In FIG. 1, symbols I to IV sequentially indicate the first lens group to the fourth lens group, and symbol S indicates an aperture stop. The code plate FT is a transparent parallel plate equivalent to various filters. The same applies to FIGS.

f = 5.97 to 17.35, F = 2.89 to 4.02, ω = 38.85 to 14.82
Surface number RDN _d ν _d Remarks
01 30.783 1.20 1.84666 23.80 1st lens
02 20.000 4.04 1.77250 49.60 Second lens
03 195.272 Variable (A)
04 * 33.137 1.04 1.83400 37.20 3rd lens
05 5.622 3.66
06 -12.159 0.90 1.48749 70.20 4th lens
07 16.480 0.74
08 16.657 2.15 1.84666 23.80 5th lens
09 -72.393 Variable (B)
10 ∞ (Aperture) Variable (C)
11 * 8.057 1.65 1.69100 54.80 6th lens
12 -51.023 1.62
13 25.556 2.97 1.84666 23.80 7th lens
14 5.000 1.58 1.51633 64.10 8th lens
15 7.002 0.12
16 7.441 1.73 1.48749 70.20 9th lens
17 * -30.003 Variable (D)
18 * 7.506 2.42 1.58913 61.15 10th lens
19 12.526 Variable (E)
20 ∞ 0.90 1.51680 64.20 Various filters
21 ∞
Surfaces marked with “*” in the surface numbers are aspherical.

"Aspherical surface"
4th page
K = 0.0, A ₄ = 1.45982 × 10 ^-4 , A ₆ = 1.91973 × 10 ^-6 , A ₈ = -3.960553 × 10 ^-7 ,
A ₁₀ = 1.98770 × 10 ^-8 , A ₁₂ = -4.19184 × 10 ^-10 , A ₁₄ = 1.41321 × 10 ^-12 ,
A ₁₆ = 7.41967 × 10 ^-14 , A ₁₈ = -7.96811 × 10 ^-16
11th page
K = 0.0, A ₄ = -2.25487 × 10 ^-4 , A ₆ = -3.41814 × 10 ^-6 , A ₈ = 4.24876 × 10 ^-7 ,
A ₁₀ = -3.16270 × 10 ^-8
17th page
K = 0.0, A ₄ = 4.82802 × 10 ^-4 , A ₆ = -1.30163 × 10 ^-5 , A ₈ = 2.84611 × 10 ^-6 ,
A ₁₀ = -1.10948 × 10 ^-7
18th page
K = 0.0, A ₄ = -1.64380 × 10 ^-4 , A ₆ = 9.30665 × 10 ^-6 , A ₈ = -3.27824 × 10 ^-7 ,
A ₁₀ = 5.70769 × 10 ^-9 .

"Variable amount"
Short focal end Intermediate focal length Long focal end
f = 5.971 f = 10.186 f = 17.350
A 0.600 7.146 13.481
B 9.382 4.385 1.000
C 1.000 0.800 0.800
D 3.935 6.861 11.289
E 2.560 2.758 2.270.

"Parameter values for each condition"
Condition (1) N ₃₂ -N ₃₃ = 0.330
Condition (2) ν ₃₃ -ν ₃₂ = 40.3
Condition (3) {(1 / r _31F ) + (1 / r _33F ) + (1 / r _33R )} × Y ′ = 2.19
Condition _{(4) L PN / L 3} = 0.645.

  FIG. 2 shows the lens configuration and the position of each lens group at the wide-angle end (upper diagram), the intermediate focal length (middle diagram), and the telephoto end (lower diagram).

f = 5.98 to 17.38, F = 2.84 to 4.08, ω = 38.83 to 14.94
Surface number RDN _d ν _d Remarks
01 30.011 1.20 1.84666 23.80 1st lens
02 20.000 0.42
03 20.327 3.79 1.77250 49.60 Second lens
04 122.719 Variable (A)
05 * 38.331 1.04 1.83481 42.70 3rd lens
06 5.663 4.88
07 -9.560 0.98 1.48749 70.20 4th lens
08 14.709 0.10
09 14.861 2.25 1.90366 31.31 5th lens
10 -44.197 Variable (B)
11 ∞ (Aperture) Variable (C)
12 * 7.952 1.64 1.73400 51.50 6th lens
13 -63.075 1.10
14 26.309 3.00 1.84666 23.80 7th lens
15 5.001 1.72 1.58913 61.20 8th lens
16 5.894 0.20
17 6.876 1.76 1.48749 70.20 9th lens
18 * -29.623 Variable (D)
19 * 13.117 2.22 1.49700 81.60 10th lens
20 ∞ Variable (E)
21 ∞ 0.90 1.51680 64.20 Various filters
22 ∞
Surfaces marked with “*” in the surface numbers are aspherical.

"Aspherical surface"
5th page
K = 0.0, A ₄ = 2.07911 × 10 ^-4 , A ₆ = -3.56339 × 10 ^-6 , A ₈ = -1.94764 × 10 ^-8 ,
A ₁₀ = 7.55632 × 10 ^-9 , A ₁₂ = -2.94766 × 10 ^-10 , A ₁₄ = 4.38582 × 10 ^-12 ,
A ₁₆ = -1.24957 × 10 ^-14 , A ₁₈ = -1.76603 × 10 ^-16
12th page
K = 0.0, A ₄ = -2.27270 × 10 ^-4 , A ₆ = -4.14175 × 10 ^-6 , A ₈ = 4.52158 × 10 ^-7 ,
A ₁₀ = -2.88961 × 10 ^-8
18th page
K = 0.0, A ₄ = 5.49045 × 10 ^-4 , A ₆ = -6.43555 × 10 ^-6 , A ₈ = 1.86841 × 10 ^-6 ,
A ₁₀ = -1.00285 × 10 ^-7
19th page
K = 0.0, A ₄ = 1.54198 × 10 ^-5 , A ₆ = 9.45191 × 10 ^-6 , A ₈ = -2.77995 × 10 ^-7 ,
A ₁₀ = 4.37061 × 10 ^-9 .

"Variable amount"
Short focal end Intermediate focal length Long focal end
f = 5.978 f = 10.199 f = 17.380
A 0.600 7.746 14.536
B 9.246 3.344 1.014
C 0.800 1.400 0.800
D 3.819 6.564 12.074
E 3.131 3.518 2.039.

"Parameter values for each condition"
Condition (1) N ₃₂ -N ₃₃ = 0.258
Condition (2) ν ₃₃ -ν ₃₂ = 37.4
Condition (3) {(1 / r _31F ) + (1 / r _33F ) + (1 / r _33R )} × Y '= 2.33
Condition _{(4) L PN / L 3} = 0.609.

  FIG. 3 shows the lens configuration and the position of each lens group at the wide-angle end (upper diagram), the intermediate focal length (middle diagram), and the telephoto end (lower diagram).

f = 5.97 to 17.37, F = 2.77 to 4.14, ω = 38.83 to 14.98
Surface number RDN _d ν _d Remarks
01 31.210 1.20 1.84666 23.80 1st lens
02 20.000 0.30
03 21.029 3.81 1.83481 42.70 Second lens
04 174.224 Variable (A)
05 * 58.159 1.11 1.84666 23.80 3rd lens
06 5.883 4.31
07 -9.625 1.84 1.48749 70.20 4th lens
08 15.314 1.96 1.84666 23.80 5th lens
09 -27.380 Variable (B)
10 ∞ (Aperture) Variable (C)
11 * 7.385 1.90 1.67790 54.90 6th lens
12 -34.073 3.35
13 -40.426 0.80 1.84666 23.80 7th lens
14 5.001 1.72 1.60311 60.70 8th lens
15 8.642 0.17
16 7.854 1.56 1.67790 54.90 9th lens
17 * 210.203 Variable (D)
18 * 11.329 2.72 1.58913 61.15 10th lens
19 ∞ Variable (E)
20 ∞ 0.90 1.51680 64.20 Various filters
21 ∞
Surfaces marked with “*” in the surface numbers are aspherical.

"Aspherical surface"
5th page
K = 0.0, A ₄ = 1.56811 × 10 ^-4 , A ₆ = 2.12294 × 10 ^-6 , A ₈ = -3.98541 × 10 ^-7 ,
A ₁₀ = 1.94205 × 10 ^-8 , A ₁₂ = -4.15052 × 10 ^-10 , A ₁₄ = 1.57096 × 10 ^-12 ,
A ₁₆ = 7.57451 × 10 ^-14 , A ₁₈ = -8.67768 × 10 ^-16
11th page
K = 0.0, A ₄ = -2.43739 × 10 ^-4 , A ₆ = 4.58973 × 10 ^-8 , A ₈ = -3.14606 × 10 ^-7 ,
A ₁₀ = 1.03961 × 10 ^-8
17th page
K = 0.0, A ₄ = 7.52428 × 10 ^-4 , A ₆ = 8.99571 × 10 ^-6 , A ₈ = 7.08199 × 10 ^-7 ,
A ₁₀ = -2.14022 × 10 ^-8
18th page
K = 0.0, A ₄ = 2.15365 × 10 ^-5 , A ₆ = 3.42576 × 10 ^-6 , A ₈ = -6.65305 × 10 ^-8 ,
A ₁₀ = 7.88618 × 10 ⁻¹⁰ .

"Variable amount"
Short focal end Intermediate focal length Long focal end
f = 5.975 f = 10.191 f = 17.367
A 0.600 6.845 13.752
B 8.552 5.009 1.000
C 3.137 0.800 0.800
D 2.993 6.565 10.410
E 3.090 3.090 3.090.

"Parameter values for each condition"
Condition (1) N ₃₂ -N ₃₃ = 0.244
Condition (2) ν ₃₃ -ν ₃₂ = 36.9
Condition (3) {(1 / r _31F ) + (1 / r _33F ) + (1 / r _33R )} × Y ′ = 2.12
Condition (4) L _PN / L ₃ = 0.637.

FIG. 4 shows the lens configuration and the position of each lens group at the wide-angle end (upper diagram), the intermediate focal length (middle diagram), and the telephoto end (lower diagram) in Example 4.
Finally, an embodiment of the information device will be described with reference to FIGS.
In this embodiment, the information device is implemented as a “portable information terminal device”.

  As shown in FIGS. 17 and 18, the portable information terminal device 30 includes a photographing lens 31 and a light receiving element (area sensor) 45, and forms an “image of the photographing object” on the light receiving element 45 by the photographing lens 31. Thus, the light receiving element 45 is configured to read.

As the photographic lens 31, one described in any one of claims 1 to 15 , specifically, any one of the above embodiments 1 to 4 is used. As the light receiving element 45, for example, a diagonal length of the light receiving area: 9.1 mm, a pixel pitch: 2.35 μm, a number of pixels: approximately 7 million pixels, a diagonal length of the light receiving area: 9.1 mm. A CCD area sensor having a pixel pitch of 2 μm and a number of pixels of approximately 10 million pixels can be used.

  As shown in FIG. 18, the output from the light receiving element 45 is processed by the signal processing device 42 under the control of the central processing unit 40 and converted into digital information. The image information digitized by the signal processing device 42 is recorded in the semiconductor memory 44 after undergoing predetermined image processing in the image processing device 41 under the control of the central processing unit 40. The “monitored image” can be displayed on the liquid crystal monitor 38, and the “image recorded in the semiconductor memory 44” can also be displayed. The image recorded in the semiconductor memory 44 can be transmitted to the outside using the communication card 43 or the like.

  As shown in FIG. 17A, the photographing lens 31 is in the “collapsed state” when the apparatus is carried, and when the user turns on the power by operating the power switch 36, as shown in FIG. Is paid out. At this time, each group of the zoom lens in the lens barrel is, for example, “arrangement of the short focal point”, and the arrangement of each group is changed by operating the zoom lever 34, and zooming to the long focal point is performed. It can be performed. At this time, the viewfinder 33 also zooms in conjunction with the change in the angle of view of the photographic lens 31.

  Focusing is performed by half-pressing the shutter button 35. Focusing can be performed by moving the second lens group or the fourth lens group, or by moving the light receiving element 45. When the shutter button 35 is further pressed, shooting is performed, and thereafter, the processing described above is performed.

  When the image recorded in the semiconductor memory 44 is displayed on the liquid crystal monitor 38 or transmitted to the outside using the communication card 43 or the like, the operation button 37 is scanned. The semiconductor memory 44 and the communication card 43 are inserted into dedicated or general-purpose slots 39A and 39B, respectively.

  When the photographing lens 31 is in the retracted state, each group of zoom lenses does not necessarily have to be aligned on the optical axis. For example, if the third lens group is retracted from the optical axis and “stored in parallel with other lens groups”, the information device can be made thinner.

  In the portable information terminal device as described above, the zoom lens according to the first to fourth embodiments can be used as the photographing lens 31, and it is small in size with high image quality using a light receiving element of 5 to 10 million pixel class. A portable information terminal device can be realized.

FIG. 3 is a diagram illustrating a lens configuration of Example 1 and movement of each lens group. FIG. 6 is a diagram illustrating a lens configuration of Example 2 and movement of each lens group. FIG. 6 is a diagram illustrating a lens configuration of Example 3 and movement of each lens group. FIG. 6 is a diagram illustrating a lens configuration of Example 4 and movement of each lens group. FIG. 6 is a diagram illustrating aberrations at the short focal end of Example 1. FIG. 6 is a diagram illustrating aberrations at the intermediate focal length of Example 1. FIG. 4 is a diagram illustrating aberrations at the telephoto end according to the first exemplary embodiment. FIG. 10 is a diagram illustrating aberrations at the short focal end of Example 2. FIG. 6 is a diagram illustrating aberrations at the intermediate focal length of Example 2. FIG. 10 is a diagram illustrating aberrations at the telephoto end according to the second embodiment. FIG. 10 is a diagram illustrating aberrations at the short focal end of Example 3. 6 is a diagram illustrating aberrations at an intermediate focal length in Example 3. FIG. FIG. 10 is a diagram illustrating aberrations at the telephoto end according to Example 3. FIG. 10 is a diagram illustrating aberrations at the short focal end of Example 4. FIG. 10 is a diagram showing aberrations at the intermediate focal length of Example 4. FIG. 10 is a diagram illustrating aberrations at the telephoto end of Example 4. It is a figure for demonstrating one Embodiment of an information device. It is a figure for demonstrating the system of the information device of FIG.

Explanation of symbols

I First lens group II Second lens group III Third lens group IV Fourth lens group S Aperture stop

Claims (19)

In order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, an aperture stop, a third lens group having a positive refractive power, and a fourth lens having a positive refractive power When the zooming is performed 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. In a zoom lens in which at least the first lens group and the third lens group move to the object side so that the distance between the lens group and the fourth lens group is increased,
The third lens group has a configuration in which four lenses of a positive lens, a negative lens, a positive lens, and a positive lens are arranged in the above order from the object side,
The refractive index of the negative lens of the third lens group: N ₃₂ and the Abbe number: ν ₃₂ , the refractive index of the positive lens arranged adjacent to the image side of the negative lens: N ₃₃ and the Abbe number: ν ₃₃ are the conditions. :
_{(1) 0.15 <(N 32} -N 33) <0.40
(2) 25 <(ν ₃₃ −ν ₃₂ ) <50
A zoom lens characterized by satisfying The zoom lens according to claim 1.
Distance from the vertex of the object side surface of the positive lens closest to the object side of the third lens group to the vertex of the image side surface of the negative lens of the third lens group: L _PN The thickness of the third lens group in the optical axis direction: L ₃ But the condition:
(4) 0.50 <(L _PN / L ₃ ) <0.75
A zoom lens characterized by satisfying In order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, an aperture stop, a third lens group having a positive refractive power, and a fourth lens having a positive refractive power When the zooming is performed 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. In a zoom lens in which at least the first lens group and the third lens group move to the object side so that the distance between the lens group and the fourth lens group is increased,
  The third lens group has a configuration in which four lenses of a positive lens, a negative lens, a positive lens, and a positive lens are arranged in the above order from the object side,
  Distance from the vertex of the object side surface of the positive lens closest to the object side of the third lens group to the vertex of the image side surface of the negative lens of the third lens group: L _PN The thickness of the third lens group in the optical axis direction: L ₃ But the condition:
  (4) 0.50 <(L _PN / L ₃ ) <0.75
A zoom lens characterized by satisfying The zoom lens according to any one of claims 1 to 3,
The third lens group, in order from the object side, is a positive lens having a large curvature surface facing the object side, a negative lens having a large curvature surface facing the image side, a positive meniscus lens having a convex surface facing the object side, and the object side A zoom lens having a configuration in which four positive lenses having a large curvature surface are arranged on the lens . The zoom lens according to claim 4.
The radius of curvature of the object side surface of the positive lens closest to the object side in the third lens group: r _31F , the radius of curvature of the image side surface of the negative lens of the third lens group: r _32R , adjacent to the image side of the negative lens of the third lens group The radius of curvature of the image side surface of the positive meniscus lens arranged as follows: r _33R , maximum image height: Y ′, conditions:
(3) 1.80 <{(1 / r _31F ) + (1 / r _32R ) + (1 / r _33R )} × Y ′ <2.60
A zoom lens characterized by satisfying In order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, an aperture stop, a third lens group having a positive refractive power, and a fourth lens having a positive refractive power When the zooming is performed 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. In a zoom lens in which at least the first lens group and the third lens group move to the object side so that the distance between the lens group and the fourth lens group is increased,
The third lens group, in order from the object side, is a positive lens having a large curvature surface facing the object side, a negative lens having a large curvature surface facing the image side, a positive meniscus lens having a convex surface facing the object side, and the object side With four positive lenses with a large curvature facing the surface,
The radius of curvature of the object side surface of the positive lens closest to the object side in the third lens group: r _31F , the radius of curvature of the image side surface of the negative lens of the third lens group : r _32R , adjacent to the image side of the negative lens of the third lens group The radius of curvature of the image side surface of the positive meniscus lens arranged as follows: r _33R , maximum image height: Y ′, conditions:
(3) 1.80 <{(1 / r _31F ) + (1 / r _32R ) + (1 / r _33R )} × Y ′ <2.60
Zumuren's, characterized in that to satisfy. The zoom lens according to any one of claims 1 to 6,
The third lens group, in order from the object side, is a positive lens having a large curvature surface facing the object side, a negative lens having a large curvature surface facing the image side, a positive meniscus lens cemented to the negative lens, and the object side A zoom lens characterized by having a four-group configuration of four positive lenses having a surface with a large curvature . The zoom lens according to any one of claims 1 to 7,
A zoom lens, wherein the curvature of the image side surface of the negative lens of the third lens group is the largest curvature among all the surfaces of the third lens group . The zoom lens according to any one of claims 1 to 8,
A zoom lens, wherein the most object side surface and the most image side surface of the third lens group are aspherical surfaces . The zoom lens according to any one of claims 1 to 9,
A zoom lens, wherein the first lens group includes at least one negative lens and at least one positive lens, and the negative lens is disposed on the object side . The zoom lens according to claim 10.
  A zoom lens, wherein the first lens group includes, in order from the object side, 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. The zoom lens according to any one of claims 1 to 11,
  A zoom lens, wherein the second lens group includes three lenses of a negative lens, a negative lens, and a positive lens in order from the object side. The zoom lens according to claim 12, wherein
A zoom lens, wherein a second lens and a third lens from the object side in the second lens group are cemented . The zoom lens according to any one of claims 1 to 13,
A zoom lens, wherein the fourth lens group is composed of one positive lens . The zoom lens according to claim 14.
A zoom lens, wherein only the fourth lens group is moved during focusing to a finite distance . An information device having a photographing function, comprising the zoom lens according to any one of claims 1 to 15 as a photographing optical system . The information device according to claim 16, wherein
An information device having a photographing function, wherein an object image formed by a zoom lens is formed on a light receiving surface of an image sensor . 18. The information device according to claim 17,
An information device having a photographing function, wherein the number of pixels of an image sensor is 5 million pixels or more . The information device according to claim 17 or 18,
An information device having a photographing function, characterized by being configured as a portable information terminal device .

Images