JP2001004920A - Zoom lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zoom lens including a large angle of view that the maximum angle of view exceeds 76 deg., having an aperture ratio that an F number in a wide-angle end state is about F3.3 and having a large variable power ratio by specifying the constituting condition of a 1st lens group and an aspherical surface. SOLUTION: This zoom lens performs variable power by changing an air distance between 1st and 2nd lens groups G1 and G2. The 1st lens group G1 is composed of a negative lens component L11 having the aspherical surface on a concave side and a positive lens component L12. The aspherical surface satisfies the condition 1×10-7<=|C3|<=1×10-2 when a distance (sag amount) along an optical axis direction from the tangential plane of the apex of each aspherical surface at the height (y) in a perpendicular direction from an optical axis is defined as S(y), the paraxial radius of curvature is defined as R, a conical coefficient is defined as k, n-th order aspherical surface coefficient is defined as Cn and they are expressed by a following aspherical surface expression; S(y)=(y2/R)/[1+(1-k.y2/R2)1/2]+C3.|y|3+C4.y4+C5.|y|5+C6.y6+C8.y8+C 10.y10+C12.y12+C14.y14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a negative leading type zoom lens, and more particularly to an ultra-compact two-unit zoom lens.

[0002]

2. Description of the Related Art Conventionally, as a so-called standard zoom lens starting from a negative / positive group, many zoom lenses aiming at miniaturization and cost reduction have been proposed. In particular, as a zoom lens in which the first lens group is composed of only two lenses and achieves both miniaturization, low cost, and high performance, Japanese Patent Application Laid-Open No. Hei 5-88084 filed by the same applicant as the present invention. A lens disclosed in Japanese Patent Application Laid-Open No. Hei 5-249376 and a lens disclosed in Japanese Patent Application Laid-Open No. Hei 8-334694 are known as examples in which the number of components is large but the size is further reduced. Further, as an example in which an aspherical lens having a third-order aspherical term is provided, there is a lens disclosed in Japanese Patent Application Laid-Open No. Hei 10-325923 filed by the same applicant as the present invention.

However, in a standard zoom lens having a large angle of view and a large zoom ratio, further downsizing (miniaturization), cost reduction (cost reduction), and realization of high-performance image quality are desired. ing.

[0004]

Problems to be Solved by the Invention Japanese Patent Laid-Open No. 5-88084
In the zoom lens described in Japanese Patent Laid-Open Publication No.
An aspherical surface is provided for the first negative lens in the group, and aberration correction is performed mainly on distortion on the wide-angle side. However, in view of the angle of view, zoom ratio, size, and brightness in the wide-angle end state, these specifications need to be further improved.

The zoom lens described in Japanese Patent Application Laid-Open No. 5-249376 has advanced in view angle, zoom ratio, and brightness at the wide-angle end, but further improved in downsizing. is necessary. Also, regarding aberration, fluctuation of spherical aberration due to miniaturization, astigmatism,
It is necessary to further improve the correction of various aberrations such as distortion and chromatic aberration of magnification.

In the zoom lens described in Japanese Patent Application Laid-Open No. 8-334694, the angle of view at the wide-angle end state,
Although the zoom ratio, size, and brightness have advanced, the number of components is large, which is disadvantageous for cost reduction. For the purpose of cost reduction to the utmost, further reduction in the number of components is necessary.

In the zoom lens described in JP-A-10-325923, various aberrations are satisfactorily corrected by providing an aspherical surface on the first negative lens in the negative first group. The ultra-wide-angle zoom lens has a large size and a large number of components, largely deviating from the object of the invention, namely, downsizing, cost reduction, and maintaining high-performance image quality. Therefore, considerable downsizing is required, and it is impossible to achieve the object of the present application on an extension of the prior art.

The present invention has been made in view of the above problems, and has a large angle of view having a maximum angle of view exceeding 76 °, an F-number in a wide-angle end state having an aperture ratio of about F3.3, It is an object of the present invention to provide a high-performance, ultra-compact zoom lens having a relatively large zoom ratio of about 2.7 times.

[0009]

In order to solve the above problems, the present invention provides, in order from the object side, a first lens having a negative refractive power.
A lens group G1 and a second lens group G2 having a positive refractive power
Wherein the first lens group G1 is a negative lens having an aspherical surface on the concave surface side in a zoom lens that changes magnification by changing the air gap between the first lens group G1 and the second lens group G2. The aspheric surface includes a lens component L11 and a positive lens component L12, and the distance (sag amount) along the optical axis direction from the tangent plane of the apex of each aspheric surface at a height y in the vertical direction from the optical axis is S ( y), a paraxial radius of curvature R, the conical coefficient kappa, the n-th order aspherical coefficient is Cn, the following aspheric expression, S (y) = (y 2 / R) / [1+ (1-κ · y ² / R ^2)
1/2 ] + C3 · | y | ³ + C4 · y ⁴ + C5 · | y | ⁵ + C6
^{· Y 6 + C8 · y 8} + C10 · y 10 + C12 · y 12 + C14 · y
When expressed in ^{14, (1) 1 × 10} -7 ≦ | provide a zoom lens which satisfies the ≦ 1 × 10 ^-2 conditions | C3.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings. First, a basic lens configuration of a zoom lens according to an embodiment of the present invention will be described.
The present invention basically realizes miniaturization of a zoom lens type having two negative and positive lens groups to the limit, cost reduction to the limit by reducing the number of components, a large angle of view, and high zoom ratio, and extremely small size. A feature of the present invention is to provide a zoom lens that achieves higher image quality while realizing high performance and cost reduction. In particular, distortion, coma flare, and spherical aberration at the telephoto end state are corrected very well, despite the fact that the optical system is very small and has a small number of components compared to zoom lenses of the same class. Is a major feature. This feature can be realized by giving the aspherical surface introduced to the lens component L11 in the negative first lens group G1 an aberration correction effect which was not known at all in the prior art.

Usually, in the case of a two-unit zoom lens of this class, the first lens unit and the second
It is necessary to extremely increase the mutual power (refractive power) with the lens group. At this time, the variation due to zooming of the spherical aberration and the corrected shape of the spherical aberration at the telephoto end in the opposite direction pose a particular problem in correcting the aberration. That is, the lens design ability is insufficient for the brightness (increase the F number) required for the lens. According to the present invention, it is possible to achieve a zoom lens that has been downsized as never before, with the minimum number of components so far, while maintaining the above-described spherical aberration correction favorably.

Next, the relationship between the aspherical surface, in particular, the aspherical surface coefficient of the odd-order term and the aberration correction will be described. Generally, an aspherical surface is represented by the sum of a series of even-order terms because the optical system is rotationally symmetric. However, in the present invention, an odd-order term is introduced into this series, which is more effectively used for aberration correction. When the aspherical surface is considered in the meridional plane, the image height Y
It seems that the value of the sag amount X differs depending on the sign of, and no symmetry is established. However, if the orthogonal coordinate system (X, Y, Z) with the optical axis as the X axis is considered as ρ = (Y ² + Z ² ) ^1/2 , the symmetry is established because the signs match.

[0013] 3-order aberration, even in spherical system, even in the aspherical surface having an aspherical surface coefficients of the even order terms, refracting surface following formulas (A), (A) X = C2 · ρ 2 + C4 · ρ 4 + C6 · Since it is an even order term of ρ as shown by ρ ⁶ +.
The fact that the refraction surface includes odd-order terms means that even-order aberrations such as second-order aberrations and fourth-order aberrations which do not exist in the past occur. Also, assuming a single curved surface and an aspherical surface, the spherical aberration exactly corresponds to the aspherical coefficient. Therefore,
By introducing an odd-order aspherical coefficient, it is possible to obtain an aberration correction effect that cannot be obtained with a spherical system and further with an aspherical surface having no third-order aspherical term.

In general, X can also be represented by the following equation (B). (B) X = ρ ² · 1 / 2r + C4 · ρ ⁴ + C6 · ρ ⁶ +... The following equation (C) is obtained by adding the third-order term C3 and the fifth-order term C5 to the equation (B). ^{(C) X = ρ 2 ·} 1 / 2r + C3 · ρ 3 + C4 · ρ 4 + C5
Ρ ⁵ + C 6 ρ ⁶ +... For example, when a second-order spherical aberration is derived, the following equation (D) is obtained.

Here, n is the refractive index, u is the angle formed with the optical axis, C3i is the cubic term of the aspherical coefficient on each surface, h is the entrance height, and R is the entrance pupil radius. Third-order spherical aberration is proportional to the fourth power of the entrance height and proportional to the third power of the pupil radius, whereas second-order spherical aberration is proportional to the third power of the entrance height and proportional to the second power of the pupil radius. ing. Therefore, by introducing the third-order term of the aspherical coefficient, it is possible to correct a low-order aberration which has conventionally been difficult to correct, so that it is possible to further improve specifications and achieve higher performance. Although the spherical aberration has been described above, other aberrations such as distortion and coma can be similarly corrected.

In particular, when the aspheric surface is used for the lens component L11 in the negative first lens group G1 of the zoom lens as in the present invention, the ability to correct low-order negative distortion on the wide-angle side increases. For this reason, in the past, the inclination (differential value) of the distortion with respect to the image height was large, and a so-called jinkasa shape was used.
The introduction of the next section can improve the situation significantly. Also,
Similarly, coma and spherical aberrations can be corrected for lower-order aberrations more, so it is possible to correct the negative aberration of a relatively low incident height caused by, for example, increasing the aperture, and reduce the circle of least confusion. it can. This is particularly effective on the telephoto side, and enables a large aperture. In the present invention, when the aspherical surface is introduced on a surface having a large declination α with respect to an axially parallel ray on the telephoto side (a ray having the largest numerical aperture emitted from an object point on the axis at infinity), the effect is great. Therefore, it is desirable to introduce the above-mentioned aspherical surface on the surface with the concave surface facing the image surface side. By distributing this effect to the improvement of the design ability at the time of further downsizing as described above,
Optical performance higher than that of a conventional zoom lens can be obtained.

Next, conditional expression (1) will be described. Conditional expression (1) defines an appropriate range of the aspherical coefficient of the third order term of the aspherical surface introduced into the lens component L11 in the negative first lens group G1. Correction of distortion and coma on the wide-angle side and correction of spherical aberration and coma on the telephoto side by setting appropriate conditions of the third-order terms on the aspheric surface expressed by the above-mentioned aspheric expression specified in the present invention. Can be satisfactorily corrected.

When the value exceeds the upper limit of the conditional expression (1), it means that the third order term of the aspherical coefficient becomes very large. In particular, the spherical aberration of the portion where the incident height is relatively low due to the influence of the second order spherical aberration. (Lower-order spherical aberration) is greatly displaced, and as a result, the slope (differential value) of the spherical aberration becomes large, so-called undulation becomes remarkable, and the performance deteriorates, which is not preferable. Further, as described above, various aberrations such as coma aberration and distortion are also overcorrected, which results in worsening. Note that the upper limit of conditional expression (1) is set to 1
If the value is set to × 10 ⁻³ or less, better aberration correction can be performed. More preferably, the upper limit value of conditional expression (1) is set to 5
It is preferable to set the value to × 10 ⁻⁴ or less because the effects of the present invention can be maximized.

Conversely, if the lower limit of conditional expression (1) is not reached, the effect of correcting each aberration as described above will be weakened, and the effect of the present invention will not be able to be fully utilized. If the lower limit of conditional expression (1) is set to 5 × 10 ⁻⁶ or more, better aberration correction can be performed. It is more preferable to set the lower limit of conditional expression (1) to 1 × 10 ⁻⁶ or more, since the effects of the present invention can be maximized. Further, when the aspherical surface is represented by the aspherical expression specified in the present invention, the third-order aspherical surface term C3 takes a value opposite to the sign of κ (cone coefficient), which is a viewpoint of aberration correction. Is preferred.

In the present invention, it is preferable that the conic coefficient κ of the aspherical surface expressed by the aspherical surface formula satisfies the following condition: (2) −1 <κ <1.

Conditional expression (2) satisfies the negative first lens group G
1 defines an appropriate range of κ (cone coefficient) of the aspherical surface introduced into the lens component L11. When the aspherical surface is represented by the aspherical expression defined in the present invention, better aberration correction can be performed by optimizing the κ term in addition to the appropriate value of the third-order term. In the case of the present invention, by using an aspheric surface based on a quadratic surface other than a spherical surface for κ (cone coefficient), correction of distortion and coma aberration particularly on the wide-angle side is assisted.

When the value exceeds the upper limit of the conditional expression (2), the κ (cone coefficient) of the aspherical surface exceeds the spherical surface, and the aspherical surface has an elliptical shape having a weak curvature near the optical axis and a strong curvature at the periphery,
On the other hand, it is not preferable because it adversely affects the correction of distortion and coma on the wide-angle side. If the upper limit of conditional expression (2) is set to 0.9 or less, favorable aberration correction can be performed.

Conversely, if the lower limit of conditional expression (2) is not reached, the κ (cone coefficient) of the aspheric surface becomes very small.
The curvature of the peripheral portion is significantly reduced. Therefore, when such an aspheric surface is introduced into the negative lens relatively on the object side as in the present invention, the refractive power in the peripheral portion is weakened, the incident height of oblique rays is increased, and the diameter of the front lens can be increased. Is not preferred. If the lower limit of conditional expression (2) is set to −0.5 or more, further miniaturization can be realized.

In the present invention, the distance along the optical axis from the vertex of the most object side surface of the first lens group G1 to the image plane in the telephoto end state is TL, and the entire zoom lens system in the wide-angle end state is TL. Where fo is the focal length of the zoom lens and ft is the focal length of the entire zoom lens system at the telephoto end, it is preferable that the following condition is satisfied: 0.3 ≦ (TL · fw) / ft ² ≦ 2 .

Conditional expression (3) is a condition for miniaturization of the optical system, and the total length TL of the entire optical system in the telephoto end state.
And the focal length in the wide-angle end state and in the telephoto end state. When the value exceeds the upper limit of conditional expression (3), the size of the zoom lens with respect to the focal length region becomes extremely large, and portability deteriorates, which is not preferable as a so-called standard zoom lens. If the upper limit of conditional expression (3) is set to 1 or less, better aberration correction and miniaturization can be realized, and the effects of the present invention can be maximized.

On the other hand, if the lower limit value of conditional expression (3) is not reached, the size of the zoom lens with respect to the focal length region becomes extremely small, and the correction of the various aberrations is undesirably deteriorated. Further, it is difficult to provide a structure such as a zoom moving cam when designing the lens barrel, which is not preferable.

The present invention also provides: (4) 0.3 ≦ f2 / ft, where f2 is the focal length of the second lens group G2 and ft is the focal length of the entire zoom lens system in the telephoto end state. It is desirable to satisfy the condition of ≦ 0.6.

Conditional expression (4) defines an appropriate power balance of the second lens group G2. As described above, the present invention proposes an optimal solution for an ultra-small zoom lens, and an appropriate power balance of the positive second lens group is a balance between a good aberration balance of the entire optical system and a practical size. It is desirable to satisfy conditional expression (4) in setting appropriately. If the upper limit of conditional expression (4) is exceeded, the second lens group G2 will be composed of weak power. Accordingly, the size of the second lens group G2 is increased, the amount of movement at the time of zooming is increased, and as a result, the back focus BF is lengthened, so that the entire system is enlarged. If the upper limit value of conditional expression (4) is set to 0.55 or less, a practical solution regarding the size of the optical system can be obtained. More preferably, setting the upper limit of conditional expression (4) to 0.49 or less is preferable because the effects of the present invention can be maximized.

On the other hand, if the lower limit of conditional expression (4) is not reached, the second lens group G2 will have a strong power. Therefore, in the case of a zoom lens having a small number of components as in the present invention, the correction of spherical aberration, coma and astigmatism particularly on the telephoto side deteriorates as described above, which is not preferable. It is preferable to set the lower limit of conditional expression (4) to 0.4 or more, because better aberration correction can be achieved. More preferably, setting the lower limit of conditional expression (4) to 0.42 or more is preferable because the effects of the present invention can be maximized.

In the present invention, when the back focus of the zoom lens in the wide-angle end state is BF, and the maximum image height allowed by the entire zoom lens system is y, (5) 1.7 ≦ BF / y It is desirable to satisfy the condition of ≦ 2.5.

Conditional expression (5) is a condition for the back focus BF of the entire optical system in the wide-angle end state, and corresponds to the maximum image height corresponding to the maximum allowable angle of view of the entire optical system, in other words, the format size of the image plane. An appropriate range of the value standardized by the radius y of the image circle is defined. If the value exceeds the upper limit value of conditional expression (5), the back focus becomes extremely large, which is not preferable in spite of miniaturization.

On the other hand, if the lower limit of conditional expression (5) is not reached, the back focus becomes extremely small, which is not preferable because it interferes with the mirror of a so-called single-lens reflex camera.

In order to realize a compact, low-cost and high-performance zoom lens as in the present invention, the second lens unit must have at least positive, negative and positive lens components from the object side. Is desirable. More preferably, it is desirable to be constituted only by four lens components of positive, positive, negative and positive.

In the present invention, it is desirable that the aspheric lens L11 is formed of a composite member of a glass material and a resin material. As a result, cost can be reduced. Further, it is desirable that the aperture stop is provided on the object side of the second lens group or in the second lens group. Also,
The focusing operation is desirably performed by extending (moving) the first lens group G1, but is not limited to this. The second lens group or a part of the lens components constituting the second lens group is moved. You may focus by doing. Also,
It is not necessary to limit the amount of extension by the focusing operation between the wide-angle end state and the telephoto end state to the same amount. For example, macro photography can be performed by protruding the vicinity of the telephoto end significantly compared to the wide-angle end.

[0035]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIGS. 1A to 1C show the lens configuration and the movement locus of the zoom lens according to the first and second examples, respectively. FIG. 1A shows a wide-angle end state, and FIG.
Shows the lens configuration in the intermediate focal length state, and (c) shows the lens configuration in the telephoto end state. In order from the object side, the first lens group G1 has a negative refractive power and the second lens group G2 has a positive refractive power.

The first lens group G1 includes, in order from the object side, a composite negative meniscus aspheric lens L11 having a convex surface facing the object side and a composite of a resin material and a glass material having an aspheric surface on the concave surface on the image side. A positive meniscus lens L12 having a convex surface facing the object side, and the second lens group G2 includes:
In order from the object side, it is composed of a positive lens component L21, a negative lens component L22, and a positive lens component L23. The positive lens component L21 has two positive lenses, and has an aperture between the two positive lenses. An aperture S is provided.

On the image side of the second lens group G2, there is provided a flare stopper SF whose air gap changes during zooming. The zooming operation is performed by moving the first lens group G1 and the second lens group G2 such that the air gap between the first lens group G1 and the second lens group G2 decreases from the wide-angle end state to the telephoto end state. This is done by moving. The short-distance focusing operation is performed by moving the first lens group G1, which is the front group, toward the object.

(First Embodiment) Table 1 below shows data values of the first embodiment. In the lens data, the surface number is the order of the lens surfaces counted from the object side, r is the radius of curvature of the lens surface, d is the surface interval on the optical axis of the lens surface, and n is the d line (λ = 5).
87.56 nm), and ν represents the Abbe number. D0 is the distance from the object to the first surface along the optical axis, f is the focal length, Fno is the F number,
2ω is the angle of view, BF is the back focus (d14 + d1
5) are shown respectively. The aspheric surface has a distance along the optical axis direction from the tangent plane of the apex of each aspheric surface at a height y in the vertical direction from the optical axis as S (y), a paraxial radius of curvature R, a cone coefficient κ, When the n-th order aspherical coefficient is Cn, it is given by the following aspherical expression.

[0039]

S (y) = (y ² / R) / [1+ (1−κ · y ²⁾
/ R ² ) ^1/2 ] + C3 · | y | ³ + C4 · y ⁴ + C5 · | y |
^{5 + C6 · y 6 + C8} · y 8 + C10 · y 10 + C12 · y 12 + C1
4 ・ y ¹⁴

In the specification table, asterisks are attached to the left of the surface numbers for the aspheric surfaces, and the paraxial radius of curvature is described in the r column. Note that the same reference numerals as those of the present embodiment are used in the specification values and the aspheric surfaces of all the embodiments below.

[0041]

[Table 1] f = 28.8-77.6 mm Fno = F3.3-5.8 2ω = 76.5-30.9 ゜ (lens data) Surface number rd Abbe number n 1) 111.5622 2.2000 49.61 1.772500 2) 19.8000 0.0300 37.50 1.558040 ★ 3) 16.7400 7.6000 1.000000 4) 27.2997 4.2000 25.43 1.805180 5) 46.6621 d5 1.000000 6) 28.4256 3.8000 60.29 1.620410 7) -254.6431 1.6000 1.000000 8> Aperture stop 0.5000 1.000000 9) 20.6834 4.0000 64.10 1.516800 10) -751.6620 0.6000 1.000000 11) -71.9589 6.8500 28.56 1.795040 12 ) 18.2538 1.3500 1.000000 13) 98.4420 3.0000 33.80 1.647690 14) -33.3001 d14 1.000000 15) flare stopper c゜ｰd15 1.000000 (aspherical data) third surface κ = -0.0877 C 3 = 0.78533 × 10 - ⁵ C 4 = 1.12030 × 10 ^-5 C 5 = 0.75286 × 10 ^-6 C 6 = -4.74760 × 10 ^-8 C 8 = 1.87130 × 10 ^-10 C10 = -5.53870 × 10 ^-13 C12 = 0.63397 × 10 ^-15 C14 = 0.00000 (variable interval data) 1-POS 2-POS 3-POS 1'-POS 2'-POS 3'-POS F & β 28.80000 50.00000 77.60000 -0.03333 -0. 03333 -0.03333 D0 ∞ ∞ ∞ 818.2574 1454.2575 2282.2598 d5 38.55293 13.23248 0.99831 41.10964 14.70515 1.94719 d14 0.00000 4.95176 11.39837 0.00000 4.95176 11.39837 d15 42.59522 54.14931 69.19143 42.59523 54.14931 69.19143 -0.1-0.1-β2 -0.12 D0 224.9617 234.0411 224.5080 d5 46.71312 21.12786 9.17220 d14 0.00000 4.95176 11.39837 d15 42.59522 54.14931 69.19142 Here, symbols such as 1'-POS, 2 ''-POS are used when focusing on a short distance at a focal length equivalent to 1-POS to 3-POS. Shows the data. (Conditional value) (1) | C3 | = 0.78533 × 10 ⁻⁵ (2) κ = −0.0877 (3) (TL · fw) / ft ² = 0.561 (4) f2 / ft = 0. 472 (5) BF / y = 1.974

FIG. 2 is a diagram showing various aberrations of the present embodiment in the wide-angle end state when focusing on infinity, and FIG. 3 is a diagram showing various aberrations in the telephoto end state when focusing on infinity. In the aberration diagrams, FNO represents the F number, Y represents the image height, d and g represent the d-line (λ = 587.56 nm) and the g-line (λ = 435.
84 nm). In the astigmatism, a solid line indicates a sagittal image plane, and a dotted line indicates a meridional image plane. The same reference numerals as those in the present embodiment are used in the aberration diagrams of all the embodiments below. As is clear from these aberration diagrams, it can be seen that the aberration is properly corrected.

(Second Embodiment) Table 2 shows the specification values of the second embodiment.

[0044]

[Table 2] f = 28.8-77.6mm Fno = F3.3-5.8 2ω = 76.5-30.9 ゜ (lens data) Surface number rd Abbe number n 1) 81.6076 2.2000 46.63 1.816000 2) 19.6999 0.0300 56.34 1.495210 ★ 3) 17.0087 7.9500 1.000000 4) 25.8422 4.0000 23.78 1.846660 5) 37.9967 d5 1.000000 6) 22.9906 3.8000 65.47 1.603000 7) -151.7022 1.0000 1.000000 8> Aperture stop 0.8000 1.000000 9) 18.9906 3.3500 69.98 1.518601 10) 73.5829 1.100000000 11) -62.3212 4.6500 28.56 1.795040 12) 17.3022 1.3000 1.000000 13) 107.7478 2.5000 32.11 1.672700 14) -30.0016 d14 1.000000 15) Flair Stocker d15 1.000000 (Aspherical surface data) Third surface κ = 0.7608 C 3 = -0.80603 × 10 ^-5 C 4 = -8.98010 × 10 ^-6 C 5 = 0.14058 × 10 ^-5 C 6 = -1.557520 × 10 ^-7 C 8 = 4.96060 × 10 ^-10 C10 = -1.39820 × 10 ^-12 C12 = 0.90064 × 10 ^-15 C14 = -0.43594 × 10 ^-18 (variable interval data) 1-POS 2-POS 3-POS 1'-POS 2'-POS 3'-POS F & β 28.80000 50.00000 77.60000 -0. 03333 -0.03333 -0.03333 D0 ∞ ∞ ∞ 817.4568 1453.4497 2281.4505 d5 37.41226 12.84823 0.97952 39.96895 14.32090 1.92840 d14 0.00000 4.80383 11.05787 0.00000 4.80383 11.05787 d15 41.99336 53.20230 67.79506 41.99336 53.20-71.04-31.04-31.04-0.17 -0.28112 D0 229.9245 238.7222 229.4850 d5 45.40209 20.59166 8.98208 d14 0.00000 4.80383 11.05787 d15 41.99336 53.20230 67.79505 where 1'-POS, 2 ''-POS etc. signifies the short distance at the focal length corresponding to 1-POS to 3-POS. The data at the time of focus is shown. (Conditional value) (1) | C3 | = 0.80603 × 10 ^-5 (2) κ = 0.7608 (3) (TL · fw) / ft ² = 0.548 (4) f2 / ft = 0.457 (5) BF / y = 1.907

FIG. 4 is a diagram showing various aberrations at the wide-angle end state when focusing on infinity according to the present embodiment, and FIG. 5 is a diagram showing various aberrations at a telephoto end state when focusing on infinity. As is clear from these aberration diagrams, it can be seen that the aberration is properly corrected.

[0046]

As described above, according to the present invention,
The angle of view 2ω = 76.5-30.9 °, the F-number has an aperture ratio of approximately F3.3-5.8, and a relatively large zoom ratio of approximately 2.7 times. It is possible to provide an ultra-small zoom lens having extremely small number of lens components with high performance.

[Brief description of the drawings]

FIGS. 1A to 1C are diagrams illustrating a lens configuration and a movement locus common to the first and second embodiments.

FIG. 2 is a diagram illustrating various aberrations of the first embodiment in a wide-angle end state upon focusing on infinity.

FIG. 3 is a diagram illustrating various aberrations of the first embodiment in a telephoto end state upon focusing on infinity.

FIG. 4 is a diagram illustrating various aberrations of the second embodiment at the wide-angle end state upon focusing on infinity.

FIG. 5 is a diagram illustrating various aberrations of the second embodiment in a telephoto end state upon focusing on infinity.

[Explanation of symbols]

 G1 First lens group G2 Second lens group L11 Aspheric negative lens component in first lens group L12 Positive lens component in first lens group L21 First positive lens component in second lens group L22 In second lens group L23 The second positive lens component in the second lens group S Aperture stop SF Flare stopper

Claims (7)

[Claims] 1. A first lens group G1 having a negative refractive power and a second lens group G having a positive refractive power in order from the object side.
2, the first lens group G1 and the second lens group G2
Wherein the first lens group G1 comprises a negative lens component L11 having a concave aspheric surface and a positive lens component L12; Distance along the optical axis direction from the tangent plane of the apex of each aspheric surface at the height y in the vertical direction from the axis (sag amount)
Where S (y), R is the paraxial radius of curvature, κ is the conic coefficient, and Cn is the nth order aspherical coefficient, the following aspherical expression: S (y) = (y ² / R) / [1+ (1 −κ · y ² / R ² )
^1/2 ] + C3 · | y | ³ + C4 · y ⁴ + C5 · | y | ⁵ + C6
^{· Y 6 + C8 · y 8} + C10 · y 10 + C12 · y 12 + C14 · y
^14. A zoom lens characterized by satisfying the following condition: 1 × 10 ⁻⁷ ≦ | C3 | ≦ 1 × 10 ⁻² . 2. The zoom lens according to claim 1, wherein a cone coefficient κ of the aspheric surface represented by the aspheric surface expression satisfies the following condition: (2) −1 <κ <1. 3. The first lens group G in a telephoto end state.
1, the distance along the optical axis from the vertex of the surface closest to the object side to the image plane is TL, the focal length of the entire zoom lens system in the wide-angle end state is fw, and the focal length of the entire zoom lens system in the telephoto end state is 3. The zoom lens according to claim 1, wherein the following condition is satisfied: 0.3 ≦ (TL · fw) / ft ² ≦ 2. 4. The focal length of the second lens group G2 is f
2. When the focal length of the entire zoom lens system at the telephoto end state is ft, the following condition is satisfied: (4) 0.3 ≦ f2 / ft ≦ 0.6. The zoom lens according to any one of the above items. 5. When the back focus of the zoom lens in the wide-angle end state is BF, and the maximum image height allowed by the entire zoom lens system is y, (5) 1.7 ≦ BF / y ≦ 2.5 The zoom lens according to any one of claims 1 to 4, wherein the following condition is satisfied. 6. The second lens group G2 according to claim 1, wherein the second lens group G2 has at least a positive lens component, a negative lens component, and a positive lens component from the object side. Zoom lens. 7. The method according to claim 1, wherein the negative lens component L11 having an aspheric surface in the first lens group G1 is formed of a member made of a composite of a glass material and a resin material. The zoom lens according to claim 1.