JP2003131134A - Zoom lens and camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zoom lens having high performance though it is made very compact and having resolving power corresponding to an imaging device realizing 2,000,000 to 4,000,000 pixels. SOLUTION: This zoom lens has a 1st group G1 having a negative focal distance, a 2nd group G2 having a positive focal distance and a 3rd group G3 having a positive focal distance in this order from an object side, and has an aperture diaphragm S moving integrally with the 2nd group G2 on the object side of the 2nd group G2. In the case of variable power from a short focus end to a long focus end, the 2nd group G2 moves monotonously from an image side to the object side, and the 1st group G1 moves to correct the variation of the position of an image surface due to the variable power. The 2nd group G2 is constituted of four lenses, that is, a positive lens L4, a negative lens L5, a positive lens L6 and a positive lens L7 in order from the object side.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a digital camera,
The zoom photographing lens used for a video camera and the like, and the camera provided with the zoom photographing lens can be applied as a zoom photographing lens used for a silver halide camera.

[0002]

2. Description of the Related Art The market for digital cameras is extremely large, and users' demands for digital cameras are also diverse. Above all, high image quality and miniaturization are always desired by users, and the weight is great. Therefore, a zoom lens used as a taking lens is required to have both high performance and small size.

Here, in terms of miniaturization, first, it is necessary to shorten the total lens length (the distance from the lens surface closest to the object side to the image surface). Further, in terms of high performance, it is necessary to have at least a resolution corresponding to an image pickup device of 2 to 4 million pixels over the entire zoom range.

There are many types of zoom lenses for digital cameras, but as a type suitable for miniaturization,
In order from the object side, a first group having a negative focal length, a second group having a positive focal length, and a third group having a positive focal length are provided, and a second group is provided on the object side of the second group. Has a diaphragm that moves integrally with the zoom lens, the second lens unit moves monotonically from the image side to the object side during zooming from the short focal length end to the long focal length end, and the first lens unit has an image accompanying zooming. Some move to compensate for variations in surface position. For example, JP-A-10-39214 and JP-A-1
Nos. 1-287953 and 2000-89110.

Japanese Unexamined Patent Publication No. 10-39214 is the earliest application of the above type and discloses all the basic configurations, but does not have sufficient structural requirements in terms of downsizing. As improvements and miniaturization of this, JP-A-11-287953 and JP-A-2000-89110 are known.
There is an issue.

[0006]

However, in the conventional examples described in these publications, since the configuration of each group, particularly the second group, is not appropriate, sufficient aberration correction is not performed, and
It does not have the performance that can be applied to an image sensor of 0,000 to 4 million pixels. The present invention has been made in view of the above points, and the present invention is a zoom lens and a camera that are sufficiently small, yet have high performance, and have a resolving power corresponding to an image sensor having 2 to 4 million pixels. Is intended to provide.

[0007]

In a zoom lens composed of three groups of negative, positive, and positive lenses as in the present invention, generally, when zooming from the short focal end to the long focal end, the second lens unit is on the image side. From the object side to the object side, and the first group moves so as to correct the fluctuation of the image plane position due to the magnification change. Most of the zooming function is borne by the second lens group, and the third lens group is provided mainly for keeping the exit pupil away from the image plane.

In order to realize a zoom lens having various kinds of aberrations and high resolving power, it is necessary to suppress aberration fluctuations due to zooming to a small extent. Especially, the second zoom lens, which is the main zooming group, has a wide zooming range. The aberration must be corrected well. Therefore, it is conceivable to increase the number of constituent elements of the second lens group, but an increase in the number of constituent elements leads to an increase in the thickness of the second lens element in the optical axis direction. It also invites an increase.

The second group consisting of four or less lenses is composed of three lenses, a positive lens, a negative lens and a positive lens in order from the object side, a positive lens, a positive lens and a negative lens.
It is known that a single lens, a positive lens, a positive lens, a negative lens, and a positive lens, and a positive lens, a negative lens, a negative lens, and a positive lens. It is intended to realize the second group having the aberration correction capability that exceeds these.

That is, the present invention has, in order from the object side, a first group having a negative focal length, a second group having a positive focal length, and a third group having a positive focal length. , Has an aperture on the object side of the second lens group that moves integrally with the second lens group, and the second lens group monotonically moves from the image side to the object side during zooming from the short focus end to the long focus end. In the zoom lens that moves so as to correct the fluctuation of the image plane position due to zooming, the second lens group of the positive lens, the negative lens, the positive lens, and the positive lens in order from the object side. It consisted of 4 sheets. Because the aperture stop is arranged on the object side of the second lens group, in the second lens group, the off-axis ray passes through a place further away from the optical axis as the lens surface on the image side farther from the aperture stop, so that correction of off-axis aberrations occurs. Get deeply involved in. The second lens group has a symmetrical arrangement having positive power on both sides of negative power as a whole, but by dividing the positive power on the image side, which is deeply involved in the correction of off-axis aberrations, into two lenses. The degree of freedom is increased, and good correction of off-axis aberrations becomes possible.

In order to perform more sufficient aberration correction, it is desirable to satisfy the following conditional expression (claim 2). 0.9 <(L _PN / Y ') <1.4 where L _PN is the vertex of the image side of the negative lens second from the object side of the second lens group, from the vertex of the object side of the positive lens closest to the object side. The distance to Y, Y'represents the maximum image height. In the second group, both the object side surface of the positive lens closest to the object side and the image side surface of the second negative lens from the object side have small curvatures, exchanging large aberrations with each other, and most contributing to aberration correction. There is. The height of light rays passing through these two surfaces is important for good aberration correction. (L _PN / Y ')
Is 1.4 or more, the axial marginal ray height at the image side surface of the second negative lens from the object side becomes too small, and it becomes difficult to correct spherical aberration. In addition, it is also disadvantageous in reducing the size of the second group. On the other hand, if (L _{P N} / Y ') is 0.9 or less, the height of the off-axis chief ray on the image side of the second negative lens from the object side becomes too small, making it difficult to correct astigmatism and coma. Become.

In order to perform better aberration correction, it is desirable that the second lens unit has two or more aspherical surfaces (claim 3). It is possible to improve the degree of freedom of aberration correction by using the two aspherical surfaces at the positions where the light rays pass differently. In order to perform the most effective aberration correction, it is desirable that the most object-side surface and the most image-side surface of the second lens unit be aspherical (claim 4). Since the most object-side surface of the second lens group is in the vicinity of the diaphragm, the on-axis and off-axis light beams pass through with almost no separation, and the aspherical surface provided here mainly contributes to correction of spherical aberration and coma. . Meanwhile, the second
Since the most image-side surface of the group is away from the diaphragm, the on-axis and off-axis light beams pass through to some extent, and the aspherical surface provided here contributes to correction of astigmatism and the like. By using two aspherical surfaces for the most object-side surface and the most image-side surface in this way, the respective aspherical surfaces have sufficiently different effects, and the degree of freedom in aberration correction is dramatically increased. It will increase.

In the zoom lens of the present invention, in order to correct each aberration better, the first lens group is arranged in order from the object side, and at least one negative lens having a large curvature surface facing the image side, It is desirable to have a positive lens having a surface with a large curvature facing the object side, and the image side surface of the negative lens should be an aspherical surface (claim 5). By configuring the first group with such a configuration, it is possible to reduce the field curvature, and by making the surface having a large refraction angle of the off-axis rays an aspherical surface, distortion aberration particularly at the short focal point end can be achieved. It becomes possible to suppress.

More specifically, in order from the object side of the first unit, a negative meniscus lens having a convex surface facing the object side, a negative lens having a surface having a large curvature facing the image side, and a large curvature facing the object side. It can be configured such that it is composed of three positive lenses each having a surface facing, and the image side surface of the negative lens is an aspherical surface (claim 6). With such a configuration, the aberration correction capability is further enhanced, which is advantageous for widening the angle of view.

In the zoom lens of the present invention, the second lens group can be composed of, in order from the object side, a positive lens, a negative lens cemented to the positive lens, a positive lens, and a positive lens in three groups (four elements). Item 7). In the second group, it has already been described that the object side surface of the positive lens closest to the object side and the image side surface of the second negative lens from the object side largely exchange aberrations with each other. The assembly error (eccentricity, etc.) tends to greatly affect the imaging performance. By cementing these two lenses together, it is possible to reduce the assembly error itself.

In the zoom lens according to the present invention, the second lens group can be composed of, in order from the object side, a positive lens, a negative lens, a positive lens cemented to the negative lens, and a positive lens in three groups and four lenses. Item 8). In the second group, when the image side surface of the second negative lens from the object side and the object side surface of the third positive lens from the object side are designed so that the difference in their mutual curvatures is small, it becomes large. It comes to exchange aberrations. In such a case, the assembling error (such as decentering) of these two lenses has a great influence on the imaging performance, but by assembling these two lenses, the assembling error itself can be suppressed to a small level.

Further, by incorporating the zoom lens as a photographing optical system of a camera, a compact camera with high image quality can be obtained. This camera may be a portable information terminal with a communication function.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 1 to 5 are sectional views showing a configuration of a zoom lens of a numerical example according to the present invention, FIG. 1 is a configuration of the numerical example 1, FIG. 2 is a configuration of the numerical example 2, and FIG.
Shows the configuration of the numerical example 3, FIG. 4 shows the configuration of the numerical example 4, and FIG. 5 shows the configuration of the numerical example 5.

As shown in FIGS. 1 to 5, in Numerical Embodiment 1 to Numerical Embodiment 5 of the present invention, a first group G1 having a negative focal length and a positive focal length are arranged in this order from the object side. Second group G2
And a third group G3 having a positive focal length, and a second group G3
On the object side of 2, there is an aperture stop S that moves integrally with the second lens group G2, and when zooming from the short focus end to the long focus end,
The second group G2 is a zoom lens that moves monotonically from the image side to the object side, and the first group G1 is a zoom lens that moves so as to correct the change in the image plane position due to zooming. It has unique characteristics.

In the zoom lenses of Numerical Examples 1 to 5, the second lens group G2 is composed of four lenses, in order from the object side, a positive lens L4, a negative lens L5, a positive lens L6 and a positive lens L7. It is characterized by Since the aperture stop S is arranged on the object side of the second group G2, in the second group G2, the lens surface on the image side farther from the aperture stop S passes the off-axis light rays away from the optical axis. It becomes deeply involved in the correction of external aberration. The second group G2 is a symmetrical arrangement having positive power on both sides of the negative power as a whole, but the positive power on the image side, which is deeply involved in the correction of off-axis aberrations, is generated by the two lenses (the positive lens L6). , The positive lens L7) increases the degree of freedom, and good correction of off-axis aberrations becomes possible.

In order to perform more sufficient aberration correction, it is desirable to satisfy the following conditional expression. 0.9 <(L _PN / Y ') <1.4 However, L _PN is the positive lens L4 closest to the object in the second lens group G2.
From the apex of the object side surface to the apex of the image side surface of the negative lens L5 that is the second lens from the object side of the second group G2, and Y ′ represents the maximum image height. In the second group G2, both the object side surface of the positive lens L4 closest to the object side and the image side surface of the second negative lens L5 from the object side have small curvatures, and large aberrations are exchanged with each other, which is the most effective for aberration correction. Have contributed. The height of light rays passing through these two surfaces is important for good aberration correction. If (L _{P N} / Y ') is 1.4 or more, the axial marginal ray height at the image side surface of the second negative lens L5 from the object side becomes too small, and it becomes difficult to correct spherical aberration. In addition, it is also disadvantageous in reducing the size of the second group G2. On the other hand, if (L _PN / Y ') is 0.9 or less, the height of the off-axis chief ray on the image side surface of the second negative lens L5 from the object side becomes too small, and it is difficult to correct astigmatism and coma. Become.

In order to perform better aberration correction, it is desirable that the second lens group G2 has two or more aspherical surfaces, as shown in FIGS. 1, 2, 4, and 5. It is possible to improve the degree of freedom of aberration correction by using the two aspherical surfaces at the positions where the light rays pass differently.

In order to perform the most effective aberration correction, it is desirable that the most object-side surface and the most image-side surface of the second group G2 be aspherical. Since the most object-side surface of the second group G2 is in the vicinity of the aperture stop S, the on-axis and off-axis light flux passes with almost no separation, and the aspherical surface provided here mainly corrects spherical aberration and coma. Contribute to. On the other hand, since the most image-side surface of the second group G2 is apart from the aperture stop S, the on-axis and off-axis light fluxes pass through to some extent, and the aspherical surface provided here is for correcting astigmatism and the like. Contribute. Thus, the second group G
By using the two aspherical surfaces provided in 2 for the most object-side surface and the most image-side surface, the respective aspherical surfaces have sufficiently different effects, and the degree of freedom in aberration correction is dramatically increased. It will increase.

On the assumption that two aspherical surfaces are used for the second lens group G2, in order to achieve more sufficient miniaturization and higher performance,
It is desirable to satisfy the following conditional expressions. 1.5 <(L _G2 / Y ') <2.5 where L _G2 is the thickness of the second lens unit G2 in the optical axis direction, and Y'is the maximum image height. When (L _G2 / Y ') is 2.5 or more, the thickness of the second lens group G2 in the optical axis direction increases, and it becomes impossible to achieve sufficient miniaturization. On the other hand, when (L _G2 / Y ') becomes 1.5 or less, the most image-side surface of the second group G2 approaches the aperture stop S,
The effect of the aspherical surface cannot be sufficiently exerted, and it becomes difficult to correct various aberrations.

In the zoom lens of the present invention, in order to better correct each aberration, as shown in FIGS. 1 to 5, the first group G1 is sequentially curved from the object side to at least one image side. Of the negative lenses L1 and L2 having a large surface facing each other, and at least one positive lens L3 having a surface having a large curvature facing the object side, at least one negative lens (negative lens L2 in the embodiment) It is desirable that the image side surface be an aspherical surface. By making the first group G1 have such a configuration,
The field curvature can be reduced, and by making the surface having a large refraction angle of the off-axis rays an aspherical surface, it becomes possible to suppress distortion especially at the short focus end. Instead of providing an aspherical surface on the image side surface of the negative lens L2, an aspherical surface may be provided on the image side surface of the negative lens L1, and the image side surface of each of the negative lens L1 and the negative lens L2. May be provided with an aspherical surface.

More specifically, as shown in FIGS. 1 to 5, the first group G1 is arranged in order from the object side, a negative lens L1 which is a negative meniscus lens having a convex surface facing the object side, and a curvature toward the image side. Of the negative lens L2 having a large surface facing toward the object side and a positive lens L3 having a surface having a large curvature facing toward the object side, and the image side surface of the negative lens L2 can be aspherical. . With such a configuration, the aberration correction capability is further enhanced, which is advantageous for widening the angle of view.

As shown in FIGS. 2 and 3, the zoom lens according to the present invention includes, in order from the object side, the second lens group, the positive lens L4, the negative lens L5 cemented to the positive lens L4, and the positive lens L.
6 and the positive lens L7 can be composed of 4 elements in 3 groups.
In the second group G2, the object side surface of the positive lens L4 closest to the object side and the image side surface of the second negative lens L5 from the object side are
As described above, the aberrations are largely exchanged with each other. Therefore, the error in assembling these two lenses (such as decentering) tends to have a large influence on the imaging performance.
By cementing these two lenses together, it is possible to reduce the assembly error itself.

As shown in FIG. 5, the zoom lens of the present invention comprises, in order from the object side, the second lens group G2 including a positive lens L4, a negative lens L5, a positive lens L6 cemented to the negative lens L5, and a positive lens L7. It can be composed of 4 sheets in 3 groups. In the second group G2, the difference in curvature between the image side surface of the negative lens L5 that is the second lens from the object side and the object side surface of the positive lens L6 that is the third lens from the object side is small. With such a design, large amounts of aberration will be exchanged. In such a case, the assembling error (such as decentering) of these two lenses has a great influence on the imaging performance, but by assembling these two lenses, the assembling error itself can be suppressed to a small level.

Specific numerical examples of the zoom lens of the present invention will be shown below. The maximum image height of Numerical Examples 1 to 3 is 3.50 mm, and the maximum image height of Numerical Examples 4 and 5 is 4.65 mm. The aberrations of the numerical examples are sufficiently corrected, and it is possible to deal with a light receiving element having 2 to 4 million pixels. It is apparent from the examples that by configuring the zoom lens as in the present invention, it is possible to secure a very small size while ensuring a very good image performance.

The meanings of the symbols in the numerical examples are as follows. f is the focal length of the entire system, F is the F number, ω is the half angle of view, R is the radius of curvature, D is the surface spacing, Nd is the refractive index, νd is the Abbe number, K is the aspherical conical constant, and A ₄ is Aspherical coefficient of 4th order, A ₆ is aspherical coefficient of 6th order, A ₈ is aspherical coefficient of 8th order, A
₁₀ is an aspherical coefficient of 10th order, A ₁₂ is an aspherical coefficient of 12th order, A ₁₄ is an aspherical coefficient of 14th order, A ₁₆ is an aspherical coefficient of 16th order, and A ₁₈ is an aspherical coefficient of 18th order. . Further, * represents an aspherical surface. However, the aspherical surface used here is defined by the following formula, 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

Numerical Example 1 f = 4.33 to 10.18, F = 2.73 to 4.00, ω = 40.30 to 19.19 Surface number RD Nd νd Remark 01 29.593 1.25 1.77250 49.62 1st lens: 1st group 02 7.058 1.20 03 17.247 1.10 1.74330 49.33 2nd lens: 1st group 04 * 4.563 1.30 05 8.485 2.16 1.72825 28.32 3rd lens: 1st group 06 ∞ Variable (A) 07 Aperture 1.00 08 * 5.283 2.61 1.72342 37.99 4th lens: 2nd group 09 -20.081 0.29 10 -12.075 0.81 1.80518 25.46 5th lens: 2nd group 11 5.253 0.31 12 8.812 1.35 1.58913 61.25 6th lens: 2nd group 13 20.251 0.10 14 12.502 1.73 1.48749 70.44 7th lens: 2nd group 15 * -8.992 Variable ( B) 16 * 13.337 1.65 1.48749 70.44 eighth lens: third group 17 463.779 variable (C) 18 ∞ 3.25 1.51680 64.20 aspherical coefficients of the various filters 19 ∞ fourth _{surface; K = 0.0, a 4 =} -1.29720 × 10 - ³ , A ₆ = -5.09824 × 10 ^-5 , A ₈ = 1.81023 × 10 ^-6 , A ₁₀ = -2.10769 × 10 ^-7 , A ₁₂ = -4.76553 × 10 ^-9 , A ₁₄ = 8.28677 × 10 ^-10 , A ₁₆ = -2.46 190 × 10 ^-11 , A ₁₈ = -4.19978 × 10 ^-13 No. Aspherical coefficient of 8 surfaces; K = 0.0, A ₄ = -1.98718 × 10 ^-4 , A ₆ = -9.47779 × 10 ^-6 , A ₈ = 2.05528 × 10 ^-6 , A ₁₀ = -1.77908 × 10 ^-7 Aspherical coefficient of 15 surfaces; K = 0.0, A ₄ = 5.86592 × 10 ^-4 , A ₆ = 3.85335 × 10 ^-5 , A ₈ = -2.22078 × 10 ^-6 , A ₁₀ = 1.73297 × 10 ^-7 16th surface Aspherical coefficient of K; 0.0, A ₄ = -1.97840 × 10 ^-4 , A ₆ = 1.55183 × 10 ^-5 , A ₈ = -1.27195 × 10 ^-6 , A ₁₀ = 4.39912 × 10 ^-8 Variable interval short focus Edge Intermediate focal length Long focus edge f = 4.33 f = 6.63 f = 10.18 A 11.860 5.530 1.400 B 1.450 5.230 10.810 C 3.570 3.241 2.731 Conditional expression value (L _PN / Y ') = 1.06 (L _G2 / Y') = 2.06

[0032] [Numerical Example 2] f = 4.33 to 10.28, F = 2.75 to 4.08, ω = 40.30 to 19.03   Surface number R D Nd νd Remarks      01 18.512 1.00 1.77250 49.62 1st lens: 1st group      02 6.948 0.99      03 13.261 1.00 1.74330 49.33 2nd lens: 1st group      04 * 4.130 1.63      05 7.992 1.76 1.84666 23.78 3rd lens: 1st group      06 21.770 Variable (A)      07 Aperture 1.00      08 * 5.666 3.23 1.72342 37.99 4th lens: 2nd group      09 -10.575 0.80 1.80518 25.46 5th lens: 2nd group      10 5.648 0.31      11 11.807 1.70 1.51680 64.20 6th lens: 2nd group      12 -11.807 0.10      13 ∞ 1.34 1.51680 64.20 7th lens: 2nd group      14 * -15.216 Variable (B)      15 * 11.050 1.64 1.48749 70.44 8th lens: 3rd group      16 47.539 Variable (C)      17 ∞ 3.25 1.51680 64.20 Various filters      18 ∞ Aspherical coefficient of the 4th surface; K = 0.0, A_Four = -1.36732 × 10^-3, A₆ = -6.93407 x 10^-Five, A₈ = -7.84082 x 10^-7, A_Ten = 2.83825 × 10^-7, A₁₂ = -5.78120 × 10^-8, A₁₄ = -7.22128 × 10^-Ten, A₁₆= 4.13152 x 10^-Ten, A₁₈= -1.85992 x 10^-11 Aspherical surface coefficient of the 8th surface; K = 0.0, A_Four = -4.08236 x 10^-Four, A₆ = -7.50989 x 10^-6, A₈ = 7.45071 x 10^-7, A _Ten  = -9.85596 x 10^-8 14th surface aspherical coefficient; K = 0.0, A_Four = 6.16408 x 10^-Five, A₆ = 4.52472 x 10^-6, A₈ = 2.22316 x 10^-7, A_Ten  = -1.94698 x 10^-8 Aspherical surface coefficient of the 15th surface; K = 0.0, A_Four = -2.44412 × 10^-Four, A₆ = 1.88531 x 10^-Five, A₈ = -1.48017 x 10^-6, A _Ten  = 4.92294 x 10^-8 Variable interval      Short focal length Intermediate focal length Long focal length      f = 4.33 f = 6.64 f = 10.28 A 10.380 5.120 1.400 B 1.450 5.600 10.980 C 3.442 2.939 2.873 Conditional expression value (L_PN / Y ') = 1.15 (L_G2 / Y ') = 2.14

Numerical Example 3 f = 4.33 to 10.19, F = 2.67 to 4.01, ω = 40.70 to 19.11 Surface number RD Nd νd Remark 01 53.342 1.03 1.77250 49.62 1st lens: 1st group 02 8.037 0.73 03 13.775 1.00 1.74330 49.33 2nd lens: 1st group 04 * 4.214 1.45 05 8.951 1.99 1.74077 27.76 3rd lens: 1st group 06 ∞ Variable (A) 07 Aperture 1.00 08 * 5.685 3.04 1.80610 33.27 4th lens: 2nd group 09 -12.982 0.80 1.84666 23.78 5th lens: 2nd group 10 5.150 0.35 11 12.099 1.66 1.49700 81.61 6th lens: 2nd group 12 -12.099 0.12 13 -71.229 1.30 1.49700 81.61 7th lens: 2nd group 14 -14.821 Variable (B) 15 * 10.924 1.81 1.49700 81.61 8th lens: 3rd group 16 273.119 Variable (C) 17 ∞ 3.25 1.51680 64.20 Various filters 18 ∞ Aspherical coefficient of 4th surface; K = 0.0, A ₄ = -1.78480 × 10 ^-3 , A ₆ = 2.57794 × 10 ^-6 , A ₈ = -1.85124 × 10 ^-5 , A ₁₀ = 2.70432 × 10 ^-6 , A ₁₂ = -2.20540 × 10 ^-7 , A ₁₄ = 4.63624 × 10 ^-9 , A ₁₆ = 3.18005 × 10 ^-10 , A ₁₈ = -1.58854 × 10 ^-11 Aspherical surface of the 8th surface Coefficient; K = 0.0, A ₄ = -2.95071 × 10 ^-4 , A ₆ = -3.13869 × 10 ^-5 , A ₈ = 5.35642 × 10 ^-6 , A ₁₀ = -4.09858 × 10 ^-7 Aspheric surface of the 15th surface Coefficient; K = 0.0, A ₄ = -3.31876 × 10 ^-4 , A ₆ = 2.64955 × 10 ^-5 , A ₈ = -1.99490 × 10 ^-6 , A ₁₀ = 5.74717 × 10 ^-8 Variable spacing Short focus edge Intermediate focus Distance Long focal end f = 4.33 f = 6.64 f = 10.19 A 11.820 5.240 1.400 B 1.440 5.660 11.330 C 3.250 2.889 2.748 Conditional expression value (L _PN / Y ') = 1.10 (L _G2 / Y') = 2.08

Numerical Example 4 f = 5.97 to 16.88, F = 2.62 to 4.36, ω = 39.23 to 15.52 Surface number RD Nd νd Remark 01 70.388 1.20 1.77250 49.62 1st lens: 1st group 02 10.023 1.26 03 17.180 1.20 1.74330 49.33 2nd lens: 1st group 04 * 7.054 2.98 05 15.475 2.49 1.71736 29.50 3rd lens: 1st group 06 -592.689 Variable (A) 07 Aperture 1.00 08 * 8.278 1.84 1.69350 53.20 4th lens: 2nd group 09 48.706 2.86 10 12.452 1.00 1.84666 23.78 5th lens: 2nd group 11 5.338 0.16 12 5.761 1.67 1.48749 70.44 6th lens: 2nd group 13 10.083 0.62 14 25.534 1.64 1.58913 61.25 7th lens: 2nd group 15 * -33.377 Variable (B ) 16 * 15.427 1.76 1.58913 61.25 8th lens: 3rd group 17 42.788 Variable (C) 18 ∞ 3.33 1.51680 64.20 Various filters 19 ∞ Aspherical coefficient of 4th surface; K = 0.0, A ₄ = -3.90444 × 10 ^-4 , A ₆ = -8.14745 × 10 ^-6 , A ₈ = 4.05425 × 10 ^-7 , A ₁₀ = -2.37422 × 10 ^-8 , A ₁₂ = 4.83887 × 10 ^-10 , A ₁₄ = -3.00058 × 10 ^-13 , A ^{_{16 = -1.47703 × 10 -13, A}} 18 = 1.35176 × 10 - ¹⁵ Aspherical coefficient of the 8th surface; K = 0.0, A ₄ = -1.19781 × 10 ^-4 , A ₆ = -9.57080 × 10 ^-7 , A ₈ = -1.21055 × 10 ^-8 , A ₁₀ = -4.74520 × 10 ^-10 aspherical coefficients of the fifteenth _{surface; K = 0.0, a 4 =} 6.26695 × 10 -5, a 6 = -1.53604 × 10 -6, a 8 = 2.74416 × 10 -7, a 10 = -2.31852 × 10 - ⁸ Aspherical coefficient of the 16th surface; K = 0.0, A ₄ = -4.48058 × 10 ^-5 , A ₆ = 4.63819 × 10 ^-6 , A ₈ = -2.28407 × 10 ^-7 , A ₁₀ = 4.37430 × 10 ^-9 Variable distance Short focal length Medium focal length Long focal length f = 5.97 f = 10.04 f = 16.88 A 20.636 8.566 1.584 B 2.137 8.266 18.481 C 5.240 4.611 3.042 Conditional expression value (L _PN / Y ') = 1.23 (L _G2 / Y') ) = 2.11

Numerical Example 5 f = 5.97 to 16.88, F = 2.68 to 4.42, ω = 39.20 to 15.52 Surface number RD Nd νd Remark 01 51.310 1.20 1.74330 49.22 1st lens: 1st group 02 9.499 1.12 03 14.486 1.20 1.80610 40.74 2nd lens: 1st group 04 * 6.911 3.47 05 15.461 2.06 1.84666 23.78 3rd lens: 1st group 06 56.433 Variable (A) 07 Aperture 1.00 08 * 8.571 1.81 1.74330 49.33 4th lens: 2nd group 09 38.021 2.22 10 10.292 1.00 1.84666 23.78 5th lens: 2nd group 11 4.918 1.83 1.48749 70.44 6th lens: 2nd group 12 8.816 0.57 13 22.000 1.61 1.48749 70.44 7th lens: 2nd group 14 * -33.647 Variable (B) 15 * 13.767 1.83 1.51680 64.20 8th lens: 3rd group 16 39.344 Variable (C) 17 ∞ 3.33 1.51680 64.20 Various filters 18 ∞ Aspheric coefficient of 4th surface; K = 0.0, A ₄ = -3.502 130 × 10 ^-4 , A ₆ = -8.45461 x 10 ^-6 , A ₈ = 3.87166 x 10 ^-7 , A ₁₀ = -2.37791 x 10 ^-8 , A ₁₂ = 4.86388 x 10 ^-10 , A ₁₄ = -3.79112 x 10 ^-13 , A ₁₆ = -1.52048 _{^{× 10 -13, a 18 = 1.32883}} × 10 -15 eighth surface non of Surface _{coefficient; K = 0.0, A 4 =} -9.80638 × 10 -5, A 6 = -3.44779 × 10 -7, A 8 = -4.47522 × 10 -8, A 10 = -8.37430 × 10 -10 of the fourteenth surface Aspheric coefficient; K = 0.0, A ₄ = 1.83538 × 10 ^-4 , A ₆ = 6.09812 × 10 ^-7 , A ₈ = 3.72360 × 10 ^-7 , A ₁₀ = -1.70939 × 10 ^-8 Aspheric surface of the 15th surface Coefficient; K = 0.0, A ₄ = -4.21513 × 10 ^-5 , A ₆ = 2.95947 × 10 ^-6 , A ₈ = -1.23500 × 10 ^-7 , A ₁₀ = 2.32351 × 10 ^-9 Variable interval short focus edge Intermediate focus Distance Long focal end f = 5.97 f = 10.05 f = 16.88 A 20.111 8.930 2.078 B 4.759 10.445 19.078 C 3.457 3.056 3.054 Conditional expression value (L _PN / Y ') = 1.08 (L _G2 / Y') = 1.94

FIG. 6 to FIG. 8 sequentially show aberration curve diagrams of Numerical Example 1. 6 is for the short focal end, FIG. 7 is for the intermediate focal length, and FIG. 8 is for the long focal end. 9 to 11
The aberration curve figure regarding Numerical example 2 is shown sequentially in FIG. Figure 9
Is for the short focal end, FIG. 10 is for the intermediate focal length, and FIG. 11 is for the long focal end. 12 to 14 sequentially show aberration curve diagrams of Numerical Example 3. FIG. 12 is for the short focal length, FIG. 13 is for the intermediate focal length, and FIG. 14 is for the long focal length. 15 to 17 sequentially show aberration curve diagrams regarding Numerical Example 4. FIG. 15 is for the short focal length, FIG. 16 is for the intermediate focal length, and FIG. 17 is for the long focal length. 18-
FIG. 20 sequentially shows aberration curve diagrams for Numerical Example 5. FIG. 18 is a short focal end, FIG. 19 is an intermediate focal length, and FIG.
Relates to the long focus end. In addition, in the spherical aberration diagrams of the aberration curve diagrams of FIGS. 6 to 20, the broken line represents the sine condition. Further, in the astigmatism diagrams of the aberration curve diagrams of FIGS. 6 to 20, the solid line represents sagittal and the broken line represents meridional.

Finally, referring to FIGS. 21 and 22,
An example of a digital camera as a portable information terminal device is shown. The digital camera has a taking lens 1 and a light receiving element (area sensor) 2, and is configured to read an image of an object to be photographed formed by the taking lens 1 on the light receiving element 2. As the photographing lens 1, any one of the zoom lenses of Numerical Examples 1 to 5 can be used.

The output from the light receiving element 2 is processed by the signal processing device 5 under the control of the central processing unit 3 and converted into digital information. The image information digitized by the signal processing device 5 is subjected to predetermined image processing in the image processing device 4 under the control of the central processing unit 3, and then recorded in the semiconductor memory 6. The liquid crystal monitor 7 can display the image being captured, or the image recorded in the semiconductor memory 6. Further, the image recorded in the semiconductor memory 6 can be transmitted to the outside by using the communication card 8 or the like.

The taking lens 1 is shown in FIG. 21 when the camera is carried.
When the user is in the retracted state as shown in (A) and the user operates the power switch 11 to turn on the power as shown in FIG. 21 (C), the lens barrel is extended as shown in FIG. 21 (B). At this time, each group of the zoom lenses is arranged, for example, at the short focus end inside the lens barrel of the taking lens 1, and the arrangement of each group is changed by operating the zoom lever 12.
It is possible to change the magnification to the long focus end. At this time, the viewfinder 13 also changes its magnification in conjunction with the change in the angle of view of the taking lens 1.

Focusing is performed by pressing the shutter button 14 halfway. In the zoom lens of the taking lens 1, focusing can be performed by moving the first group G1 or the third group G3 or moving the light receiving element 2. When the shutter button 14 is pushed further down, a picture is taken, and thereafter the above-mentioned processing is carried out.

The operation button 9 is used to display the image recorded in the semiconductor memory 6 on the liquid crystal monitor 7 or to send it to the outside using the communication card 8 or the like. The semiconductor memory 6, the communication card 8 and the like are used by inserting them into dedicated or general-purpose slots. In this embodiment, a memory card slot 6a for inserting the semiconductor memory 6 and a communication card slot 8a for inserting the communication card 8 are provided. Reference numeral 15 indicates a flash.

In the camera (portable information terminal device) as described above, the zoom lenses of Numerical Examples 1 to 5 can be used as a taking lens. Therefore, it is possible to realize a high-quality and small-sized camera (portable information terminal device) using the light receiving element 2 of 2 to 4 million pixel class. As a result, the user can take a high-quality image with the portable information terminal device having excellent portability and send the image to the outside. The present invention is not limited to the above embodiment. That is, various modifications can be made without departing from the gist of the present invention.

[0043]

As described above, according to the invention as set forth in claim 1, it is sufficiently small in size and high in performance.
Since it is possible to provide a zoom lens having a resolving power corresponding to an image sensor having 2 to 4 million pixels, it is possible to realize a small-sized camera (mobile information terminal device) with high image quality.

According to the second aspect of the present invention, spherical aberration, astigmatism, and coma can be corrected well, so that a higher performance zoom lens can be provided.
It is possible to realize a camera (mobile information terminal device) with higher image quality.

According to the third aspect of the present invention, since the aspherical surfaces are used for the different surfaces of the second lens unit, the degree of freedom in aberration correction can be improved, and a zoom lens with higher performance is provided. Therefore, a camera (mobile information terminal device) having higher image quality can be realized.

According to the fourth aspect of the present invention, the degree of freedom in aberration correction can be dramatically increased, so that it is possible to provide a zoom lens capable of improving performance in a more effective manner. Therefore, a compact and high-quality camera (portable information terminal device) can be realized with good cost performance.

According to the fifth aspect of the present invention, the field curvature can be reduced and the distortion aberration at the single focal point can be suppressed, so that a smaller and high-performance zoom lens can be provided. It is possible to realize a compact and high-quality camera (portable information terminal device).

According to the sixth aspect of the invention, since the aberration correction capability can be further enhanced, a compact and high-performance zoom lens suitable for widening the angle of view can be provided. It is possible to realize a small camera (portable information terminal device) that can capture images.

According to the seventh and eighth aspects of the present invention, it is possible to provide a zoom lens which has high performance, is sufficiently small, is less affected by an assembly error, and has stable performance. Further, a high-performance and low-cost camera (portable information terminal device) can be realized.

According to the ninth aspect of the invention, a zoom lens having a sufficiently small size and high performance and having a resolution corresponding to an image pickup device having 2 to 4 million pixels is used as an optical system for photographing. Since a compact and high-quality camera can be provided, the user can take a high-quality image with a camera having excellent portability.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration of a zoom lens according to Numerical Example 1.

FIG. 2 is a sectional view showing a configuration of a zoom lens according to Numerical Example 2.

FIG. 3 is a sectional view showing a configuration of a zoom lens according to Numerical Example 3.

FIG. 4 is a sectional view showing a configuration of a zoom lens according to Numerical Example 4.

FIG. 5 is a sectional view showing a configuration of a zoom lens according to Numerical Example 5.

FIG. 6 is an aberration curve diagram at a short focal end of the zoom lens according to Numerical Example 1.

7 is an aberration curve diagram at an intermediate focal length of the zoom lens of Numerical Example 1. FIG.

FIG. 8 is an aberration curve diagram at a long focal length end of the zoom lens according to Numerical Example 1.

FIG. 9 is an aberration curve diagram at a short focus end of a zoom lens according to Numerical Example 2.

FIG. 10 is an aberration curve diagram at an intermediate focal length of the zoom lens of Numerical Example 2.

11 is an aberration curve diagram at a long focal length end of a zoom lens according to Numerical Example 2. FIG.

FIG. 12 is an aberration curve diagram at a short focus end of a zoom lens according to Numerical Example 3.

FIG. 13 is an aberration curve diagram at an intermediate focal length of the zoom lens of Numerical Example 3.

FIG. 14 is an aberration curve diagram at a long focal length end of a zoom lens according to a numerical example 3.

FIG. 15 is an aberration curve diagram at a short focus end of the zoom lens of Numerical Example 4.

16 is an aberration curve diagram at an intermediate focal length of the zoom lens of Numerical Example 4. FIG.

FIG. 17 is an aberration curve diagram at a long focal length end of the zoom lens of Numerical Example 4.

FIG. 18 is an aberration curve diagram at a short focus end of the zoom lens of Numerical Example 5.

FIG. 19 is an aberration curve diagram at an intermediate focal length of the zoom lens of Numerical Example 5.

FIG. 20 is an aberration curve diagram at a long focal length end of a zoom lens according to Numerical Example 5.

FIG. 21 is an external view of a digital camera showing one embodiment of a camera (portable information terminal device) according to the present invention, where (A) is a perspective view of a front side when being carried, and (B).
Is a diagram showing a state where the lens barrel is extended, and (C) is a perspective view of the back surface side.

22 is a block diagram showing a circuit configuration of the digital camera shown in FIG. 21.

[Explanation of symbols]

G1 first group G2 second group G3 Third group L1 negative meniscus lens (first lens) L2 negative meniscus lens (second lens) L3 positive lens (third lens) L4 Positive lens (4th lens) L5 negative lens (5th lens) L6 Positive lens (6th lens) L7 Positive lens (7th lens)

Continued front page    F term (reference) 2H087 KA02 KA03 MA12 MA14 PA07                       PA08 PA17 PA18 PB08 QA02                       QA06 QA17 QA22 QA25 QA32                       QA41 QA45 RA05 RA12 RA13                       RA36 RA43 SA14 SA16 SA19                       SA62 SA63 SA64 SB04 SB15                       SB22                 5C022 AB66 AC42 AC54

Claims (9)

[Claims] 1. A second group having, in order from the object side, a first group having a negative focal length, a second group having a positive focal length, and a third group having a positive focal length. Has an aperture on the object side, which moves integrally with the second lens unit, and upon zooming from the short focus end to the long focus end, the second lens unit moves monotonically from the image side to the object side, The first group is a zoom lens that moves so as to correct the fluctuation of the image plane position due to zooming, and the second group includes four lenses in order from the object side: a positive lens, a negative lens, a positive lens, and a positive lens. This is a zoom lens. 2. The zoom lens according to claim 1, wherein the zoom lens is arranged second from the object side apex of the positive lens arranged closest to the object side of the second group, from the object side of the second group. The zoom lens is characterized by satisfying the following conditional expression, 0.9 <(L _PN / Y ') <1.4, where L _{PN is} the distance to the image-side vertex of the negative lens and _Y'is the maximum image height. . 3. The zoom lens according to claim 1, wherein the second group has at least two aspherical surfaces. 4. The zoom lens according to claim 3, wherein the most object-side surface and the most image-side surface of the second group are aspherical surfaces. 5. The zoom lens according to claim 1, wherein the first group comprises, in order from the object side, at least one negative lens having a large curvature surface facing the image side;
A zoom lens comprising: a positive lens having a large curvature surface facing the object side, and the image side surface of the negative lens is an aspherical surface. 6. The zoom lens according to claim 1, wherein the first group comprises, in order from the object side, a negative meniscus lens having a convex surface facing the object side and a negative lens having a surface having a large curvature facing the image side. A zoom lens comprising three positive lenses each having a surface having a large curvature facing the object side, and an image side surface of the negative lens being an aspherical surface. 7. The zoom lens according to claim 1, wherein the second group comprises, in order from the object side, a positive lens, a negative lens cemented to the positive lens, a positive lens, and a positive lens in three groups and four lenses. This is a zoom lens. 8. The zoom lens according to claim 1, wherein the second lens group includes, in order from the object side, a positive lens, a negative lens, a positive lens joined to the negative lens, and a positive lens.
A zoom lens characterized by being made up of 4 groups. 9. A camera comprising the zoom lens according to claim 1 as a photographing optical system.