JPH06130298A - Compact zoom lens - Google Patents

Abstract

PURPOSE:To obtain an inexpensive and compact zoom lens with thin lens thickness by providing a negative refracting power on first and second lens components. CONSTITUTION:A first lens group G1 provided with a positive refracting power and a second lens group G2 provided with a negative refracting power are provided sequentially from a material side. The first lens group G1 is comprised of the first lens component L1 provided with the negative refracting power and formed in shape to face its convex surface to an object, the second lens component L2 provided with the negative refracting power, and a third lens component L3 comprised of a biconvex lens. The first group satisfies the conditions of equation I-III. In the equations, the refracting power of a plastic lens in the first lens group G is assumed as phip, the refracting power of a glass lens out of the first and second lens components L1, L2 in the first lens group G1 as phig, the focal distance of the first lens group G1 as fa, the paraxial radius of curvature on the material side surface of the plastic lens in the first lens group G1 as rp1, the paraxial radius of curvature on the image side surface of the plastic lens as rp2, and the thickness of the first lens group G1 from a lens surface nearest to the object side to the one nearest to the image side as Da.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens for a 35 mm size lens shutter, and more particularly to a compact and low cost zoom lens.

[0002]

2. Description of the Related Art In recent years, zoom lenses for lens shutter cameras have become smaller and higher in magnification. The simplest type of various zoom types suitable for this type of zoom lens includes a first lens group G ₁ having a positive refractive power and a second lens group G ₂ having a negative refractive power. It is a telephoto type zoom lens with two groups. This type of zoom lens is suitable for shortening the back focus to some extent to achieve miniaturization, and for example, the one disclosed in Japanese Patent Laid-Open No. 3-200912 is known.

As a low cost zoom lens, for example, Japanese Patent Laid-Open No. 3-127012 discloses a zoom lens in which the number of components is reduced by making it aspherical.
Further, Japanese Patent Laid-Open No. 3-200913 discloses a zoom lens which has been promoted to be plastic.

[0004]

SUMMARY OF THE INVENTION
According to Japanese Patent Laid-Open No. 3-200912, the first lens group G ₁ is composed of positive, negative, and positive refractive power arrangements, and the negative refractive power component therein has negative spherical aberration and positive distortion. In order to correct, the lens surface has a strong concave surface facing the object side. Further, since this lens surface faces the convex surface with respect to the diaphragm, it is difficult to correct the lower coma aberration, and a large shift of the lower coma aberration due to color occurs.

Further, in the zoom lens disclosed in Japanese Patent Laid-Open No. 3-127012, the first lens group G ₁ has a negative and positive refractive power arrangement, and aberrations are corrected by using many aspherical surfaces. Then, the off-axis aberration for a single color in the zoom lens disclosed in Japanese Patent Laid-Open No. 3-127012 was improved, but the chromatic aberration of magnification was not sufficiently corrected and the achromatization was insufficient due to the small number of constituent elements. Furthermore, since there is little freedom in aberration correction,
The lens thickness of each group (distance from the surface closest to the object side to the surface closest to the image side) cannot be reduced, and the size of the camera can be reduced.
It was not preferable in terms of weight reduction. Then, the distance between the concave refracting power component and the convex lens component forming the first lens group is large, and a large difference in astigmatism due to color occurs.

Further, in the zoom lens disclosed in Japanese Patent Laid-Open No. 3-200913, the first lens group G ₁ is constructed with a negative and positive refractive power arrangement, but a low dispersion glass material is used for the lens of the concave component. Therefore, it is necessary to excessively achromatize the convex component. Therefore, the number of the first lens group G ₁ is increased, which is insufficient for cost reduction. Therefore, the present invention is
An object of the present invention is to provide a compact zoom lens that is low in cost and has a small lens thickness.

[0007]

The compact zoom of the present invention
In order to achieve the above objectives, mullens is described below.
Have a configuration. Have positive refractive power in order from the object side
First lens group G₁And a second lens having a negative refractive power
Group G₂And the first lens group G₁And the second lens group G₂Between
And a diaphragm arranged in the first lens group G₁And the second
Group G₂By changing the air spacing between
For a compact zoom lens that changes the focal length of the system
By the way, the first lens group G₁Is a negative bend in order from the object side.
First lens component L having bending power ₁And has a negative refractive power
Second lens component L₂And a third lens having a positive refractive power
Component L₃And has a second lens group G₂Is from the object side
The fourth lens component L having a positive refractive power in order _Four And the negative
Fifth lens component L having refractive power_FiveWith and the first ren
Component L₁And the second lens component L₂Either one of
The other is a glass lens.
Configured to meet the following conditions
Is. (1) 0.29 <(φ_P+ Φ_g) ・ F_a<0.8
 φ_P<0, φ_g<0 (2) 0 <(rp₁-Rp₂) / (Rp₁+ Rp₂) <0.15 (3) 0.3 <D_a/ F_a<0.45 However, φ_p: First lens group G₁Refraction of plastic lens inside
Force, φ_g: First lens group G₁First lens component L in₁And the
2 lens component L₂Power of the glass lens of the, f_a: First lens group G₁Focal length of rp₁: First lens group G₁Plastic lens object inside
Side lens surface paraxial radius of curvature, rp₂: First lens group G₁Image side of the plastic lens inside
Paraxial radius of curvature of the lens surface, D_a: First lens group G₁Most object-side lens surface in
To the lens surface closest to the image side.

[0008]

According to the lens structure of the present invention as described above, the first
The first lens component L ₁ and the second lens component L _{2 are different from those in the case where the} lens group G ₁ is configured with a positive / negative / positive refractive power arrangement.
Has a negative refracting power, the principal point of the combination of the first lens component L ₁ and the second lens component L ₂ goes in a direction further away from the diaphragm toward the object side. Therefore, not only is positive distortion aberration mitigated, but the principal point position of this combination and the third
Since the distance from the lens component L ₃ is widened, it is possible to weaken the refractive power of each lens component, increase the degree of freedom of aberration correction, and further reduce the lens thickness of the first lens group G ₁ .

Since the distance between the second lens component L ₂ and the third lens component L ₃ can be reduced as the thickness of the first lens group G ₁ is reduced, the difference in color of coma aberration can be suppressed. be able to. Further, since the plastic lens is used in the first lens group G ₁ , the cost can be reduced.

Here, the first lens component L ₁ , the second lens component L ₂ , the fourth lens component L ₄ and the fifth lens component L ₅
Is positioned farther from the stop, and therefore it is desirable to have a bending shape in which aberrations with respect to off-axis rays are less likely to occur, and the third lens component L ₃ is configured to have a small amount of negative spherical aberration. Is desirable. The above conditional expressions in the present invention will be described in detail below.

Conditional expression (1) is a condition for achieving a balance between downsizing and on-axis aberrations and off-axis aberrations, and is a position of a combined principal point of the first lens component L ₁ and the second lens component L _2. To determine the proper position of. First, the first lens component L ₁
Consider the case where is a plastic lens. Here, the upper limit of conditional expression (1) is exceeded when (a) the refractive power ψ _{P of the} plastic lens becomes negatively large, and (b) the refractive power ψ _{g of the} glass lens becomes negatively large. There are two possible cases. In the case of (a), the plastic lens is
Since the temperature dependence of the refractive index is large, the fluctuations of the focus position and the curvature of field when the temperature changes become large, which is not preferable. Further, in the case of (b), the position of the principal point of the combination of the first lens component L ₁ and the second lens component L ₂ becomes closer to the diaphragm, and it becomes difficult to correct positive distortion. .

On the contrary, the lower limit of conditional expression (1) is exceeded when (c) the refractive power ψ _{P of the} plastic lens becomes negative and (d) the refractive power ψ _{g of the} glass lens becomes negative. When it becomes smaller, there are two possible ways. In the case of (c), the air distance between the second lens component L ₂ and the third lens component L ₃ must be widened in order to make the principal point positions of the first lens group G ₁ the same. It goes against miniaturization. Further, in the case of (d), since the position of the principal point of combining the first lens component L ₁ and the second lens component L ₂ is farther from the stop, positive distortion can be corrected well, but the g-line at the wide-angle end is good. It becomes difficult to correct the axial chromatic aberration at (435.8 nm).

Next, consider the case where the second lens component L ₂ is a plastic lens. Here, the upper limit of conditional expression (1) exceeds (e) the refractive power ψ _{P of the} plastic lens.
Can be negative, and (f) the refractive power ψ _{g of the} glass lens can be negative.
In the case of (e), since the plastic lens has a large temperature dependence of the refractive index, the fluctuation of the focal position and the field curvature becomes large when the temperature changes, which is not preferable. In the case of (f), the difference in height between the on-axis ray and the off-axis ray incident on the first lens component L ₁ becomes small, and the fluctuation of coma aberration due to the angle of view at the wide-angle end can be suppressed well. It gets harder.

On the contrary, the lower limit of the conditional expression (1) is to be satisfied when (g) the refractive power ψ _{P of the} plastic lens becomes negative and (h) the refractive power ψ _{g of the} glass lens becomes negative. When it becomes smaller, there are two possible ways. In the case of (g), it becomes difficult to balance the correction of chromatic aberration on-axis and off-axis. Further, in the case of (h), the axial chromatic aberration for the g-line (435.8 nm) at the wide-angle end is insufficiently corrected, which is not preferable.

Conditional expression (2) defines the bending shape of the plastic lens in the first lens group G ₁ and is a condition for achieving a balance between off-axis aberrations and on-axis aberrations. If the upper limit of conditional expression (2) is exceeded,
The object side lens surface of the plastic lens is concave to the object, and the difference between the incident height of the on-axis light rays and the incident height of the off-axis light rays on the plastic lens is reduced, and the variation of coma aberration due to the angle of view can be corrected. It is not preferable because it will disappear.

On the other hand, when the value is less than the lower limit, it works effectively for off-axis rays, but it is not preferable because negative spherical aberration cannot be suppressed. Conditional expression (3) defines an appropriate value of the lens thickness of the first lens group in order to downsize the zoom lens with good performance. If the upper limit of conditional expression (3) is exceeded, the lens thickness D _a of the first lens unit becomes large and the zoom lens becomes large, which is not preferable.

If the lower limit value of the conditional expression (3) is not reached, the lens thickness D _a of the first lens unit becomes small, which leads to downsizing, but the off-axis rays and the on-axis rays in each lens component. This is not preferable because there is no difference in passing height and it becomes impossible to suppress the variation of coma aberration due to the angle of view. And in the present invention, in addition to the above-mentioned configuration,
Furthermore, it is desirable to satisfy the following conditional expressions (4) and (5). (4) 0.04 <D ₂₃ / f _a <0.10 (5) 0.2 <| D _b / f _b | <0.4 where D ₂₃ : the second lens component L ₂ and the third lens Ingredient L ₃
Air space between, f _a: the focal length of the first lens group G _1, D _b: the total thickness of the lens system from the surface closest to the object side in the second lens group G ₂ to the surface on the most image side , F _b : focal length of the second lens group G ₂ .

If the upper limit of conditional expression (4) is exceeded, the air gap between the second lens component L ₂ and the third lens component L ₃ becomes large, which is contrary to the miniaturization. In addition, a large amount of color coma is generated, which is not preferable. If the lower limit of conditional expression (4) is not reached, the lens thickness of the first lens group G ₁ will be small, and size reduction will be achieved, but the refracting power of each lens component will be strong and correction of coma will be difficult. I will end up. Further, in manufacturing, the tolerance of the distance between the second lens component L ₂ and the third lens component L ₃ becomes strict, which makes it impossible to reduce the cost, which is not preferable.

Conditional expression (5) balances downsizing and correction of off-axis aberrations. When it exceeds the upper limit, it is not preferable because it is against size reduction. When the value is less than the lower limit, it is effective for downsizing, but it is not preferable because the refractive power of each lens component becomes large and the fluctuation of coma aberration due to the angle of view cannot be suppressed. Further, in the present invention, in addition to the above-mentioned configuration, the following conditional expressions (6) and (7)
It is desirable to satisfy. (6) | (ν ₁ φ ₁ + ν ₂ φ ₂ ) / (φ ₁ + φ ₂ ) | <
35 (7) | (N ₁ φ ₁ + N ₂ φ ₂ ) / (φ ₁ + φ ₂ ) |>
1.60 However, [nu _1: the first lens Abbe number of components L _1, phi _1: the first lens optical power component L _1, [nu _2: Abbe number of the second lens component L _2, phi _2: Refractive power of the second lens component L ₂ , N ₁ : Refractive index of the first lens component L ₁ with respect to d-line, N ₂ : Refractive index of the second lens component L ₂ with respect to d-line.

If the upper limit of conditional expression (6) is exceeded,
It is not preferable because coma aberration due to color increases. If the lower limit of conditional expression (7) is exceeded, the Petzval sum becomes negatively large, and positive field curvature and astigmatism cannot be corrected, which is not preferable.

[0021]

EXAMPLES Examples of the present invention will be described in detail below. Figure
1, FIG. 5 and FIG. 9 respectively show a first embodiment according to the present invention.
It is a lens block diagram about ~ 3. Examples 1 to 3
Regarding the basic configuration, a diagram showing a lens configuration diagram of Example 1.
As represented by 1, the positive refractive power is sequentially provided from the object side.
First lens group G₁And a second lens having a negative refractive power
Group G₂And, when changing the magnification from the wide-angle end to the telephoto end,
The first lens group so as to reduce the air gap between both lens groups.
G₁And the second lens group G ₂And move to the object side. these
First lens group G₁And the second lens group G₂Between
S is placed. Then, the first lens group G₁Is negative
A meniscus with a refractive power and a convex surface facing the object side
First lens component L of the negative lens element₁And has a negative refractive power
Second lens component L₂And the third lens component of the biconvex lens
Minute L₃Composed of and. In addition, the second lens group G₂Is a thing
In order from the body side, it has a positive refractive power and the concave surface was directed toward the object side
The fourth lens component of the positive meniscus lens and the negative refractive power
5th lens of negative meniscus lens with concave surface facing the object side
Ingredient L_FiveComposed of and. And the above-mentioned first lens
Component L₁Is composed of a plastic lens.

Here, in the first and third embodiments, the second lens component L ₂ is composed of a meniscus negative lens having a convex surface facing the object side. Further, in the second embodiment, the second lens component L ₂ is composed of a biconcave lens having a gentle concave surface facing the object side. 13, FIG. 17, and FIG.
1 shows the lens block diagrams of Examples 4 to 6 of the present invention, respectively.

The basic structure of the fourth to sixth embodiments is almost the same as that of the first to third embodiments, and only the differences will be described below. In Examples 4 to 6, the second lens component L ₂ is a meniscus negative lens which is made of plastic and has a convex surface facing the object side. Then, in Example 4 and Example 6, the first lens component L
₁ is composed of a negative meniscus lens with a convex surface facing the object side. Further, in the fifth embodiment, the first lens component L
₁ is composed of a negative meniscus lens with a gentle concave surface facing the object side.

Then, in Examples 1 to 6, the first lens component L ₁ , the second lens component L ₂ , and the fourth lens component L
_{Since the fourth} and fifth lens components L ₅ are located apart from the diaphragm S, they have a bending shape in which aberration is less likely to occur with respect to off-axis rays. Further, the third lens component L ₃ has a shape in which the amount of negative spherical aberration generated is small.

The data values of each embodiment of the present invention are listed below. The leftmost number in the specification table of the example represents the order from the object side of the lens surface, that is, the surface number, r is the radius of curvature of the lens surface, d is the lens surface interval, refractive index n and Abbe number ν are It is a value for the d line (λ = 587.6 nm). In addition,
In the specifications table, * is attached to the surface number of the lens surface having an aspherical shape. This aspherical shape is a position of height y on the tangent plane with the origin at the position where the optical axis passes on the tangent plane and the traveling direction of light being positive, considering the tangent plane at the aspherical surface vertex. When the displacement of the aspherical surface in the direction of the optical axis at is defined as x with the aspherical vertex as a reference, it is expressed by the following equation.

X = cy ² / {1+ (1-κc ² y ² ) ^1/2 } + C ₄ y ⁴ + C ₆ y ⁶ + C ₈ y ⁸ + C ₁₀ y ¹⁰ However, c is the curvature of the aspherical surface at the aspherical vertex. (Reciprocal of curvature radius r), κ is a quadric surface parameter, C ₄ , C ₆ ,
C ₈ and C ₁₀ are aspherical surface coefficients, respectively. [Example 1] f = 39.0 to 50.0 to 78.0 F _NO = 4.1 to 5.3 to 8.2 2ω = 51.2 to 46.6 to 31.0 ° rd n ν 1 * 14.599 2.45 1.58518 30.2 (plastic) 2 * 12.503 1.20 3 158.198 2.30 1.67270 32.2 4 20.606 1.70 5 24.337 3.40 1.51680 64.1 6 -11.353 2.20 7 0.000 11.65 〜 7.35 〜 1.89 (Aperture) 8 * -24.650 2.30 1.58518 30.2 (Plastic) 9 -16.799 4.10 10 -10.402 1.50 1.77279 49.5 11 -31.885 1st surface 2nd surface 8th surface _{κ -0.9568 1.0000 0.0000 C 4 -0.1041 ×} 10 -3 -0.8133 × 10 -4 0.4625 × 10 -4 C 6 -0.2961 × 10 -5 -0.3151 × 10 -5 0.1689 × 10 -6 C 8 - 0.4347 × 10 ⁻⁷ −0.4498 × 10 ⁻⁷ 0.4595 × 10 ⁻⁸ C ₁₀ 0.4559 × 10 ⁻⁹ 0.1079 × 10 ⁻⁸ −0.1134 × 10 ⁻¹⁰ The values corresponding to the conditions according to this embodiment are shown below. _{(1) (φ p + φ} g) · f a = 0.661 (2) (rp 1 -rp 2) / (rp 1 + rp 2) = 0.074 (3) D a / f a = 0.406 ( _{4) D 23 / f a =} 0.063 (5) | D b / f b | = 0.282 (6) | (ν 1 φ 1 + ν 2 φ 2) / (φ 1 + φ 2) | =
31.9 (7) | (N ₁ φ ₁ + N ₂ φ ₂ ) / (φ ₁ + φ ₂ ) | =
1.662 [Example 2] f = 39.0 to 65.0 to 102.0 F _NO = 4.0 to 6.7 to 10.5 2ω = 57.0 to 36.6 to 24.0 ° rd n ν 1 * 16.802 2.50 1.58518 30.2 (plastic) 2 * 14.513 1.20 3- 114.534 1.80 1.74000 28.2 4 60.723 1.80 5 43.568 4.00 1.51680 64.1 6 -11.897 1.40 7 0.000 14.6 to 6.48 to 2.06 (Aperture) 8 * -28.587 2.50 1.58518 30.2 (Plastic) 9 -18.823 4.20 10 -10.859 1.50 1.77279 49.5 11 -35.639 No. 1st surface 2nd surface 8th surface κ -3.7580 0.4319 -7.4250 C ₄ 0.0000 0.0000 0.0000 C ₆ -0.3302 × 10 ^-5 -0.1997 × 10 ^-5 0.6561 × 10 ^-6 C ₈ -0.2866 × 10 ^-8 -0.1194 × 10 ^-7 -0.1741 x 10 ^-8 C ₁₀ -0.1307 x 10 ^-9 0.859 2 x 10 ^-10 0.1857 x 10 ^-10 The values corresponding to the conditions according to the present invention are shown below. _{(1) (φ p + φn} ) · f a = 0.404 (2) (rp 1 -rp 2) / (rp 1 + rp 2) = 0.073 (3) D a / f a = 0.396 (4 _{) D 23 / f a = 0.063} (5) | D b / f b | = 0.293 (6) | (ν 1 φ 1 + ν 2 φ 2) / (φ 1 + φ 2) | =
28.5 (7) | (N ₁ φ ₁ + N ₂ φ ₂ ) / (φ ₁ + φ ₂ ) | =
1.717 [Example 3] f = 33.0 to 48.0 to 63.0 F _NO = 4.1 to 6.0 to 7.9 2ω = 65.4 to 48.4 to 38.0 ° rd n ν 1 * 13.026 2.17 1.58518 30.2 (plastic) 2 * 10.335 1.20 3 75.845 1.77 1.68893 31.1 4 20.100 1.65 5 23.407 2.87 1.51680 64.1 7 0.000 10.39 〜 4.80 〜 1.87 (Aperture) 8 * -22.201 2.02 1.58518 30.2 (Plastic) 9 -16.557 4.65 10 -9.783 1.31 1.77279 49.5 11 -29.750 1st surface 2nd surface Eighth surface κ -0.9583 1.0000 0.0000 C ₄ -0.2181 × 10 ^-3 -0.2286 × 10 ^-3 0.5175 × 10 ^-4 C ₆ -0.7734 × 10 ^-5 -0.8288 × 10 ^-5 0.3974 × 10 ^-6 C ₈ 0.3222 × 10 ⁻⁷ 0.920 4 × 10 ⁻⁷ 0.3259 × 10 ⁻⁸ C ₁₀ −0.1341 × 10 ⁻⁹ 0.3038 × 10 ⁻⁹ −0.3015 × 10 ⁻¹¹ The values corresponding to the conditions according to the present invention are shown below. _{(1) (φ p + φ} g) · f a = 0.393 (2) (rp 1 -rp 2) / (rp 1 + rp 2) = 0.115 (3) D a / f a = 0.403 ( _{4) D 23 / f a =} 0.069 (5) | D b / f b | = 0.326 (6) | (ν 1 φ 1 + ν 2 φ 2) / (φ 1 + φ 2) | =
30.9 (7) | (N ₁ φ ₁ + N ₂ φ ₂ ) / (φ ₁ + φ ₂ ) | =
1.662 [Example 4] f = 39.0 to 50.0 to 78.0 F _NO = 4.1 to 5.3 to 8.2 2ω = 57.8 to 46.2 to 31.0 ° rd n ν 1 400.000 1.50 1.67270 32.2 2 31.549 0.30 3 * 19.640 3.30 1.58518 30.2 ( Plastic) 4 * 17.037 2.30 5 59.105 3.40 1.51860 70.0 6 -10.847 2.20 7 0.000 11.77 〜 7.48 〜 2.01 (Aperture) 8 * -39.761 2.30 1.58518 30.2 (Plastic) 9 -20.501 4.25 10 -11.178 1.50 1.71700 48.0 11 -62.820 3rd Surface 4th Surface 8th Surface κ 0.4034 0.2157 0.2991 C ₄ -0.3019 × 10 ^-3 -0.1532 × 10 ^-3 0.3928 × 10 ^-4 C ₆ -0.4545 × 10 ^-5 -0.3449 × 10 ^-5 0.3371 × 10 ^-6 C ₈ −0.4977 × 10 ⁻⁹ −0.4114 × 10 ⁻⁷ −0.2399 × 10 ⁻⁸ C ₁₀ −0.1860 × 10 ⁻⁹ 0.3417 × 10 ⁻¹⁰ 0.280 5 × 10 ⁻¹⁰ The values corresponding to the conditions according to the present invention are shown below. _{(1) (φ p + φ} g) · f a = 0.467 (2) (rp 1 -rp 2) / (rp 1 + rp 2) = 0.071 (3) D a / f a = 0.397 ( _{4) D 23 / f a =} 0.085 (5) | D b / f b | = 0.288 (6) | (ν 1 φ 1 + ν 2 φ 2) / (φ 1 + φ 2) | =
31.9 (7) | (N ₁ φ ₁ + N ₂ φ ₂ ) / (φ ₁ + φ ₂ ) | =
1.663 [Example 5] f = 39.0 to 50.0 to 78.0 F _NO = 4.1 to 5.3 to 8.2 2ω = 56.8 to 46.2 to 31.0 ° rd n ν 1 -330.236 1.50 1.61750 30.8 2 44.061 0.30 3 * 20.849 3.20 1.58518 30.2 (Plastic) 4 * 17.251 2.35 5 71.943 3.20 1.5186 70.0 6 -10.925 2.20 7 0.000 11.6 to 7.34 to 1.88 (Aperture) 8 * -38.225 2.30 1.58518 30.2 (Plastic) 9 -20.408 4.25 10 -11.063 1.50 1.71700 48.0 11 -56.855 No. 1st surface 2nd surface 8th surface κ 0.3691 0.2144 0.2991 C ₄ -0.3043 × 10 ^-3 -0.1649 × 10 ^-3 0.4087 × 10 ^-4 C ₆ -0.4079 × 10 ^-5 -0.3011 × 10 ^-5 0.4031 × 10 ^-6 C ₈ -0.9347 × 10 ^-8 0.2809 × 10 ^-7 -0.3068 × 10 ^-8 C ₁₀ -0.1064 × 10 ^-10 0.1755 × 10 ^-9 0.3344 × 10 ^-10 The values corresponding to the conditions of the present invention are shown below. _{(1) (φ p + φ} g) · f a = 0.325 (2) (rp 1 -rp 2) / (rp 1 + rp 2) = 0.094 (3) D a / f a = 0.388 ( _{4) D 23 / f a =} 0.086 (5) | D b / f b | = 0.288 (6) | (ν 1 φ 1 + ν 2 φ 2) / (φ 1 + φ 2) | =
30.7 (7) | (N ₁ φ ₁ + N ₂ φ ₂ ) / (φ ₁ + φ ₂ ) | =
1.611 [Example 6] f = 39.0 to 50.0 to 78.0 F _NO = 4.1 to 5.3 to 8.2 2ω = 56.8 to 46.2 to 31.0 ° r d n ν 1 1301.444 1.50 1.67270 32.2 2 41.200 0.30 3 * 20.740 3.10 1.58518 30.2 ( 4 * 16.753 2.50 5 56.506 3.40 1.51860 70.0 6 -11.147 2.20 7 0.000 11.27 〜 7.11 〜 1.82 (Aperture) 8 * -35.824 3.00 1.58518 30.2 (Plastic) 9 -21.250 4.50 10 -10.894 1.50 1.71700 48.0 11 -46.601 3rd Surface 4th surface 8th surface κ 0.4034 0.2157 0.2991 C ₄ -0.2903 × 10 ^-3 -0.1521 × 10 ^-3 0.4787 × 10 ^-4 C ₆ -0.4319 × 10 ^-5 -0.3218 × 10 ^-5 0.1128 × 10 ^-6 C ₈ 0.1737 × 10 ⁻⁷ 0.4413 × 10 ⁻⁷ 0.4851 × 10 ⁻⁸ C ₁₀ −0.3966 × 10 ⁻⁹ −0.9904 × 10 ⁻¹⁰ −0.2668 × 10 ⁻¹⁰ The condition corresponding values according to the present invention are shown below. _{(1) (φ p + φ} g) · f a = 0.296 (2) (rp 1 -rp 2) / (rp 1 + rp 2) = 0.107 (3) D a / f a = 0.401 ( _{4) D 23 / f a =} 0.093 (5) | D b / f b | = 0.328 (6) | (ν 1 φ 1 + ν 2 φ 2) / (φ 1 + φ 2) | =
31.7 (7) | (N ₁ φ ₁ + N ₂ φ ₂ ) / (φ ₁ + φ ₂ ) | =
1.698 FIGS. 2 to 4 are diagrams showing various aberrations of Example 1 of the present invention, FIGS. 6 to 8 are diagrams of various aberrations of Example 2 of the present invention, and FIGS. 10 to 12 are diagrams showing various aberrations of Example 3 of the present invention. 14 to 16 are aberration diagrams of Example 4 of the present invention, FIGS. 18 to 20 are aberration diagrams of Example 5 of the present invention, and FIGS. Aberration diagrams are shown respectively.

Here, FIGS. 2, 6, 10, 14, 18, 2
2 is an aberration diagram in the shortest focal length state at the wide-angle end, and FIGS. 3, 7, 11, 15, 19, 23 are aberration diagrams in the intermediate focal length state, FIGS.
6, 20 and 24 are various aberration diagrams in the longest focal length state at the telephoto end. In each astigmatism diagram of each aberration diagram, the meridional image plane is shown by a broken line and the sagittal image plane is shown by a solid line.

From comparison of each aberration diagram, the zoom lens according to the present invention is a compact zoom lens having a relatively small number of constituent elements and a thin lens thickness, but has excellent image forming performance from the wide-angle end to the telephoto end. You can see that

[0029]

As described above, according to the present invention, it is possible to realize a compact and low-cost zoom lens for a compact camera having a relatively small number of components. In addition, the present invention can employ a focusing method by the first group feeding, the second group feeding, and floating in addition to the whole feeding.

Further, the entire first lens group or the second lens group is decentered with respect to the optical axis, or a part of the first lens group or the second lens group is decentered with respect to the optical axis. The effect of shaking can be obtained.

[Brief description of drawings]

FIG. 1 is a lens configuration diagram of Example 1. FIG.

FIG. 2 is a diagram of various types of aberration at the wide-angle end of Example 1.

FIG. 3 is a diagram of various types of aberration in the intermediate focal length state of Example 1.

FIG. 4 is a diagram of various types of aberration at the telephoto end of the first example.

FIG. 5 is a lens configuration diagram of Example 2.

FIG. 6 is a diagram of various types of aberration at the wide-angle end of Example 2.

FIG. 7 is a diagram of various types of aberration in the intermediate focal length state of Example 2.

FIG. 8 is a diagram of various types of aberration at the telephoto end of the second example.

FIG. 9 is a lens configuration diagram of Example 3.

FIG. 10 is a diagram of various types of aberration at the wide angle end of Example 3;

FIG. 11 is a diagram of various types of aberration in the intermediate focal length state of Example 3.

FIG. 12 is a diagram of various types of aberration at the telephoto end of Example 3;

FIG. 13 is a lens configuration diagram of Example 4.

FIG. 14 is a diagram of various types of aberration at the wide angle end of Example 4;

FIG. 15 is a diagram of various types of aberration in the intermediate focal length state of Example 4.

FIG. 16 is a diagram of various types of aberration at the telephoto end of the fourth example.

FIG. 17 is a lens configuration diagram of Example 5.

FIG. 18 is a diagram of various types of aberration at the wide angle end of Example 5;

FIG. 19 is a diagram of various types of aberration in the fifth example of the intermediate focal length state.

FIG. 20 is a diagram of various types of aberration at the telephoto end of the fifth example.

FIG. 21 is a lens configuration diagram of Example 6.

FIG. 22 is a diagram of various types of aberration at the wide-angle end of Example 6;

FIG. 23 is a diagram of various types of aberration in the intermediate focal length state of Example 6.

FIG. 24 is a diagram of various types of aberration at the telephoto end of the sixth example.

[Explanation of symbols]

G ₁ --- 1st lens group, G ₂ --- 2nd lens group, L ₁ --- 1st lens component, L ₂ --- 2nd lens component, L ₃ --- 3rd lens component, L ₄ --- 4 lens components, L ₅ ... 5th lens component, S ... Aperture,

Claims (3)

[Claims] 1. A first lens element having a positive refractive power in order from the object side.
The lens group G ₁ and the second lens group G ₂ having a negative refractive power
When the first has lens group G ₁ and a diaphragm disposed between the second lens group G _2, the air between the first lens group G ₁ and the second lens group G ₂ In a compact zoom lens in which the focal length of the entire system is changed by changing the distance, the first lens group G ₁ includes, in order from the object side, a first lens component L ₁ having a negative refractive power and a negative lens component L ₁ . It has a second lens component L ₂ having a refractive power and a third lens component L ₃ having a positive refractive power, and the second lens group G ₂ has a positive refractive power in order from the object side. It has a fourth lens component L ₄ and a fifth lens component L ₅ having a negative refractive power, and one of the first lens component L ₁ and the second lens component L ₂ is a plastic lens. The other is composed of a glass lens and is characterized by satisfying the following conditions. Compact zoom lens. _{(1) 0.29 <(φ P} + φ g) · f a <0.8
_{φ P <0, φ g <} 0 (2) 0 <(rp 1 -rp 2) / (rp 1 + rp 2) <0.15 (3) 0.3 <D a / f a <0.45 However, phi _p: the refractive power of the plastic lens in the first lens group G _1, phi _g: the first lens component L of the first lens group G _1
1 and the refractive power of the glass lens of the second lens component L _2, f _a: the object of the plastic lens of the first lens group G _1: the focal length of the first lens group G _1, rp ₁ paraxial radius of curvature of the lens surface side, rp _2: the paraxial curvature of the lens surface on the image side of the plastic lens in the first lens group G ₁ radius, D _a: the most object in the first lens group G ₁ From the lens surface on the side to the lens surface on the most image side. 2. The compact zoom lens according to claim 1, wherein the zoom lens satisfies the following conditions. (4) 0.04 <D ₂₃ / f _a <0.10 (5) 0.2 <| D _b / f _b | <0.4 where D ₂₃ : the second lens component L ₂ and the third lens Ingredient L ₃
Air space between, f _a: the focal length of the first lens group G _1, D _b: the total thickness of the lens system from the surface closest to the object side in the second lens group G ₂ to the surface on the most image side , F _b : focal length of the second lens group G ₂ . 3. The compact zoom lens according to claim 1, wherein the zoom lens satisfies the following conditions. (6) | (ν ₁ φ ₁ + ν ₂ φ ₂ ) / (φ ₁ + φ ₂ ) | <
35 (7) | (N ₁ φ ₁ + N ₂ φ ₂ ) / (φ ₁ + φ ₂ ) |>
1.60 However, [nu _1: the first lens Abbe number of components L _1, phi _1: the first lens optical power component L _1, [nu _2: Abbe number of the second lens component L _2, phi _2: Refractive power of the second lens component L ₂ , N ₁ : Refractive index of the first lens component L ₁ with respect to d-line, N ₂ : Refractive index of the second lens component L ₂ with respect to d-line.