JP2002323655A - Super compact zoom lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a super compact zoom lens having the angle of view of about 2ω=74.1 deg. to 11.8 deg., having a variable power ratio of about 6.6, made small in diameter and small in size to a possible limit, constituted of small number of lenses, made excellent in cost performance and realizing high performance and high magnification. SOLUTION: This zoom lens has a 1st lens group G1 having positive refractive power, a 2nd lens group G2 having negative refractive power, at least one lens group and a lens group Gm having positive refractive power in this order from an object side, and power is varied by changing a distance between the 1st and the 2nd lens groups G1 and G2. Then, the lens group Gm is constituted of a positive lens component L1 whose convex surface faces to an image side and a negative lens component L2 whose concave surface faces to the object side in this order from the object side, and satisfies a specified condition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultra-compact zoom lens having high magnification, small size, light weight and excellent cost performance, and more particularly to an ultra-compact high-magnification standard zoom lens.

[0002]

2. Description of the Related Art At present, including a wide-angle end state, a zoom ratio of 3 to
The so-called standard zoom lens having a magnification of four times has been steadily reduced in size and cost. Since this lens is always carried while being mounted on the camera body, it is essential that the lens be small, lightweight, have sufficient imaging performance, and be inexpensive. In order to satisfy such a condition, it is necessary to configure each lens unit with strong power and to make each lens unit as thin as possible.

[0003] For example, Japanese Patent Application Laid-Open No. 1-222917,
JP-A-8-248319, JP-A-9-10145
9, JP-A-2000-75204, JP-A-20
A four-group zoom having a positive, negative, positive, and positive power arrangement as disclosed in, for example, JP-A-00-187161 has been proposed.

[0004]

However, most of the zoom lenses disclosed in the above publications have a zoom ratio of about 3 to 4 times. Further, even in a case having a large zoom ratio, the size is large and the number of components is large, and the performance is not satisfactory. As in the present invention, the zoom ratio of 28 to 200 mm in the Leica format exceeds 6.62 times,
And there is no ultra-compact zoom lens downsized to the limit.

The present invention has been made in view of the above problems, and has an angle of view of about 2ω = 74.1 ° to 11.8 °, and has a small diameter up to the limit having a magnification ratio of about 6.6. It is an object of the present invention to provide an ultra-compact zoom lens that is compact, miniaturized, has a small number of components, is excellent in cost performance, and has high performance and high magnification.

[0006]

In order to solve the above problems, the present invention provides, in order from the object side, a first lens group G1 having a positive refractive power and a second lens group G1 having a negative refractive power.
2, at least one lens group, and a lens group Gm having a positive refractive power. The magnification is changed by changing the air gap between the first lens group G1 and the second lens group G2. In the ultra-compact zoom lens, the lens group Gm includes, in order from the object side, a positive lens component L1 having a convex surface facing the image side and a negative lens component L2 having a concave surface facing the object side. Preferably, the lens group Gm is
It is desirable that only the positive lens component L1 and the negative lens component L2 be included. In the wide-angle end state of the lens group Gm, the length on the optical axis from the object side vertex of the lens component closest to the object side to the image side vertex of the lens component closest to the image (final lens) is Σdw, and the zoom lens is When the focal length of the entire system at the telephoto end is denoted by ft, it is desirable that the following condition be satisfied. (1) 0.10 <Σdw / ft <0.54

In a preferred aspect of the present invention, it is desirable that the following condition is satisfied when the focal length of the first lens group G1 is f1. (2) 0.20 <f1 / ft <0.55

In a preferred aspect of the present invention, it is preferable that the following condition is satisfied when the focal length of the second lens group G2 is f2. (3) 0.03 <| f2 | / ft <0.20

In a preferred aspect of the present invention, the length on the optical axis from the image-side vertex of the positive lens component L1 to the object-side vertex of the negative lens component L2 in the lens group Gm is dpn,
When the length on the optical axis from the object side vertex of the most object side lens component to the image side vertex of the most image side lens component in the lens group Gm is dm, the following condition may be satisfied. desirable. (4) 0.23 <dpn / dm <0.90

It is desirable that either the positive lens component L1 or the negative lens component L2 in the lens group Gm has at least one aspheric surface. In the case where the lens group Gm is made extremely thin and the minimum number of lenses that satisfies the conditions of achromatism and aberration correction is provided, the effect of the present invention can be sufficiently exerted by giving an aberration correction effect particularly by introducing an aspheric surface. Desirable.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A conventional zoom lens equivalent to 28 to 200 mm usually adopts a design method of increasing the power of each group and increasing the number of components for aberration correction in order to promote miniaturization. I have. However, according to this design method, each group becomes thicker due to the increase in the number of lenses, which causes an increase in weight. In addition, the dead space between the lens groups is reduced, and it tends to be painful and eventually larger. Therefore, further downsizing requires a completely different design approach.

Therefore, the present invention uses a new design method of killing useless lenses and minimizing the number of components in each group. By using the effect, each group can be made thinner, and the size can be reduced without setting an unreasonable power arrangement.

It is particularly important in the present invention that the rear (master) group of the positive (convex) leading zoom lens, which is represented by positive, negative, positive, and positive, is designed to have the minimum number of achromatic and aberration correction lenses. (Roughness) This is a configuration composed of only two elements. This configuration is a basic configuration of a telephoto type. The configuration like the present invention is extremely rear group (master group)
This is an essential condition for reducing the thickness of the lens and shortening the back focus. With this configuration, it was possible to minimize the filter size, the lens diameter, and the overall length.

The features of the present invention will be described below according to each conditional expression. The conditional expression (1) is obtained by standardizing the back focus, that is, the total thickness of the optical system, from the total optical length of the zoom lens by the focal length on the telephoto side. When the value exceeds the upper limit of conditional expression (1), the entire thickness of the optical system of the zoom lens becomes thick. As a result, miniaturization, which is the object of the present invention,
It cannot be satisfied with the lens configuration of the present invention. In addition, the weight including the lens barrel becomes heavy, and the cost of materials increases, which makes the lens unattractive as a regular high-power zoom lens.

If the upper limit of conditional expression (1) is set to 0.50 or less, a general high-power zoom lens can be realized at lower cost. In addition, the upper limit of conditional expression (1) is set to 0.47.
With the following settings, a common high-power zoom lens can be realized at a lower cost. Further, when the upper limit value of conditional expression (1) is set to 0.45 or less, the effect of the present invention can be maximized.

On the other hand, if the lower limit of conditional expression (1) is not reached, the total thickness of the optical system of the zoom lens will be extremely thin.
For this reason, first, the back focus becomes short, and it becomes virtually impossible to use it as an interchangeable lens for a single-lens reflex camera. Further, it is necessary to give each group a remarkably strong power, so that it becomes difficult to correct aberrations, and as a result, it becomes impossible to increase the zoom ratio, which is not preferable.
When the lower limit of conditional expression (1) is set to 0.20 or more, the effects of the present invention can be maximized.

Next, conditional expression (2) will be described. Conditional expression (2) is obtained by normalizing the focal length of the first lens unit with the focal length on the telephoto side. Optimization of the focal length of the first lens group is an important condition in determining good aberration correction and size. When the value exceeds the upper limit of conditional expression (2), it means that the power of the first lens unit is weakened, and as a result, the whole zoom lens system is undesirably enlarged. Further, in the case of a high-magnification zoom as in the present invention, a significant change in the overall length is caused at the time of telephoto, making it difficult to carve a cam curve in the lens barrel, which cannot be realized. In the case of an extremely small configuration as in the present invention, setting of an optimal Petzval sum becomes more important. Reducing the power of the first lens unit reduces the Petzval sum, which makes it difficult to correct curvature of field and astigmatism, which is not preferable.

If the upper limit of conditional expression (2) is set to 0.50 or less, it is possible to set a more optimal Petzval sum. If the upper limit value of conditional expression (2) is set to 0.48 or less, the effects of the present invention can be maximized.

On the other hand, when the value goes below the lower limit of conditional expression (2), it means that the power of the first lens unit becomes extremely large. The remarkable increase in the power of the first lens group has the effect of lowering the light beam having a large angle of view incident on the front lens to the peripheral portion of the lens. For this reason, the amount of peripheral light decreases, resulting in an increase in the front lens diameter and an increase in the filter size, which is not preferable. In addition, in terms of aberration correction, peripheral coma is deteriorated on the wide angle side, and spherical aberration is deteriorated on the telephoto side. When the lower limit of conditional expression (2) is set to 0.30 or more, the effects of the present invention can be maximized.

Next, the conditional expression (3) will be described. Conditional expression (3) is obtained by normalizing the absolute value of the focal length of the second lens unit with the focal length on the telephoto side. When the value exceeds the upper limit of conditional expression (3), it means that the power of the negative second lens unit becomes weak. In this case, the amount of movement of the second lens group increases, resulting in an increase in size. Further, since the light beam having a large angle of view incident on the front lens is further reduced to the peripheral portion of the lens, the peripheral light amount is reduced, and as a result, the diameter of the front lens and the filter size are increased, which is not preferable.

If the upper limit of conditional expression (3) is set to 0.10 or less, further miniaturization can be realized. When the upper limit of conditional expression (3) is set to 0.085 or less, the effects of the present invention can be maximized.

On the other hand, when the value goes below the lower limit of conditional expression (3), it means that the power of the negative second lens unit becomes extremely strong. In this case, the Petzval sum becomes smaller than an appropriate value, and it becomes difficult to correct the curvature of field and astigmatism. Also, including distortion at the wide-angle end,
Correction of off-axis aberration becomes difficult, which is not preferable.

It is preferable that either the positive lens component L1 or the negative lens component L2 in the lens group Gm has at least one aspheric surface. Extremely lens group Gm
When the thickness of the lens is reduced and the number of lenses is set to the minimum number of conditions for achromatism and aberration correction, it is desirable to provide an aberration correction effect by introducing an aspherical surface in order to sufficiently exert the effects of the present invention. In particular, in the case of a high-magnification zoom lens as in the present invention, it is important to correct spherical aberration on the telephoto side and upper coma aberration by using an aspheric surface for miniaturization and high performance.

In order to maximize the effect of the present invention, it is preferable that the zoom lens has a basic structure of a positive / negative / positive / positive four-group zoom lens in view of a balance between miniaturization and high performance.

Next, conditional expression (4) will be described. This conditional expression appropriately defines the magnitude of the distance between the two lens elements in the lens group Gm.
In the case of comprising a positive lens element and a negative lens element as in the present invention, the air space controls the principal point as a group, and secures a dead space with the group immediately before it,
In addition, the back focus is set to an optimum value, thereby achieving both miniaturization and high magnification, maintaining the power of both lens elements at an optimum, and fulfilling the role of achieving good aberration correction.

When the value exceeds the upper limit of conditional expression (4), the total length of the zoom lens becomes large, and the back focus becomes short.

Conversely, when the value goes below the lower limit of conditional expression (4), it means that the power of both lens elements becomes strong. In this case, correction of various aberrations including spherical aberration is deteriorated at both the wide-angle end and the telephoto end, which is not preferable. Further, as a problem in manufacturing, a lens element having an extremely small eccentric tolerance is generated, which makes manufacturing difficult, which is not preferable. Further, the image-side surface of the final lens becomes significantly concave with respect to the image surface. For this reason, unless a back focus significantly larger than the specified value is achieved, mechanical interference occurs with a so-called single-lens reflex quick return mirror, and the lens cannot be used.

If the lower limit of conditional expression (4) is set to 0.30 or more, various aberrations such as spherical aberration can be corrected more favorably. If the lower limit of conditional expression (4) is set to 0.58 or more, the effects of the present invention can be maximized.

In a preferred aspect of the present invention, the at least one lens group includes only a third lens group G3 having a positive refractive power, the focal length of the third lens group G3 being f3, Assuming that the focal length of the group Gm is fm, it is preferable that the following conditional expression (5) is satisfied. (5) 0.2 <f3 / fm <1.0

Next, the conditional expression (5) will be described. This conditional expression (5) is a condition that defines the power ratio between the third lens unit and the fourth lens unit. It is necessary for the correction of various aberrations that the power of the third lens group is stronger than the power of the fourth lens group, and it is desirable to satisfy this condition especially for spherical aberration correction at the telephoto end.

If the upper limit of conditional expression (5) is exceeded, the third condition
This means that the power of the fourth lens group is higher than that of the lens group. In this case, spherical aberration and coma aberration particularly on the telephoto side are significantly deteriorated, and a super-compact high-magnification zoom as in the present invention cannot be achieved. When the upper limit of conditional expression (5) is set to 0.8 or less, various aberrations such as spherical aberration can be corrected more favorably. Also, the upper limit value of conditional expression (5) is set to 0.6.
By setting the following, the effects of the present invention can be maximized.

If the lower limit of conditional expression (5) is not reached, it means that the power of the third lens unit is stronger than that of the fourth lens unit. In this case, correction of various aberrations including spherical aberration is deteriorated on both the wide-angle side and the telephoto side, which is not preferable. Further, as a problem in manufacturing, the allowable eccentricity of a part of the lens element becomes extremely small, which makes manufacturing difficult, which is not preferable.

If the lower limit of conditional expression (5) is set to 0.3 or more, various aberrations such as spherical aberration can be corrected more favorably. When the lower limit of conditional expression (5) is set to 0.35 or more, the effects of the present invention can be maximized.

Next, the aspherical surface introduced into the present invention will be described. In order to maximize the effect of the present invention, both the positive lens component L1 and the negative lens component L2 in the lens group Gm have at least one positive surface of the lens as it goes from the optical axis toward the periphery. It is desirable to have an aspherical surface having a shape in which the refractive power is weakened or a shape in which the negative refractive power of the lens unit is increased.

This is an effective technique particularly for a zoom lens having an ultra-compact and high magnification as in the present invention. As described above, the lens group Gm is extremely thinned,
In the present invention, which is configured with the minimum number of achromatic and aberration correction conditions, an aspheric surface is introduced into both the positive lens component L1 and the negative lens component L2, so that off-axis such as spherical aberration and coma aberration can be obtained. Various aberrations can be improved, and a degree of freedom in designing an optimum back focus and a dead space between groups can be obtained.

In addition, having a shape in which the positive refractive power of a single lens decreases as going from the optical axis to the periphery of the lens, or a shape in which the negative refractive power of a single lens increases,
That is, the shape shows that the negative spherical aberration can be further corrected. This is because the spherical aberration of the lens group Gm alone is favorably corrected, and a large F number can be handled.

Further, in order to further exert the effect of the present invention, the positive lens component L1 in the lens group Gm is composed of a double-sided aspherical surface, and the image-side aspherical surface of the double-sided aspherical lens is located on the optical axis. It is desirable to have a shape in which the curvature of the peripheral portion of the effective diameter is larger than the curvature of. This is because, as described above, the spherical aberration of the lens group Gm alone is favorably corrected, and the effect of correcting various off-axis aberrations is also enhanced. Since the surfaces of the two aspheric surfaces are separated from each other by the thickness of the lens, the incident height and the declination of each ray are different on each surface. A plurality of aberrations can be corrected at the same time by designing the shape of each aspheric surface using the difference between the incident height and the declination.

Further, the negative lens component L2 in the lens group Gm has at least one aspherical surface, and the aspherical surface has a shape in which the negative part of the effective diameter at the outermost periphery of the effective diameter becomes stronger than on the optical axis. It is desirable to have. This works favorably for correcting off-axis aberrations such as field curvature at the wide-angle end and coma aberrations at the telephoto end.

In a preferred aspect of the present invention, the second lens group G2 has at least one negative lens component and a positive lens component, and has a refractive index np of the positive lens component with respect to d-line and an Abbe number. When νp is satisfied, it is desirable that the following conditional expressions (6) and (7) are satisfied. (6) np <1.85 (7) νp <27

Next, conditional expressions (6) and (7) will be described.
Conditional expressions (6) and (7) are conditions indicating the optimum glass material of the positive lens in the second lens group. Conditional expression (6) shows the setting of the optimum refractive index for the d-line.

When the value exceeds the upper limit of conditional expression (6), the positive (convex) refractive index becomes too high, and when the second lens group is used with relatively high power, it is difficult to optimally set the Petzval sum. Is not preferred. When the upper limit value of conditional expression (6) is set to 1.84 or less, further 1.83 or less, the effect of the present invention can be maximized.

Conditional expression (7) shows an appropriate setting of the Abbe number. If the conditional expression (7) is not satisfied, the fluctuations due to the zooming of the longitudinal chromatic aberration and the lateral chromatic aberration cannot be completely corrected, which is not preferable.

[0043]

Embodiments of the present invention will be described below with reference to the accompanying drawings. (First Embodiment) FIG. 1 shows a lens configuration of the first embodiment and the movement locus thereof. The ultra-compact zoom lens according to the first example has, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a positive refractive power. The third lens group G3 and the fourth lens group Gm having a positive refractive power include four positive, negative, positive, and positive groups.

The first lens group G1 includes, in order from the object side, a cemented positive lens L11 composed of a cemented negative meniscus lens having a convex surface facing the object side and a positive lens, and a positive meniscus lens L12 having a convex surface facing the object side. It is composed of Second
The lens group G2 has, in order from the object side, a negative meniscus lens L21 having an aspheric surface on the object side, made of a composite of a resin and a glass member, a biconcave negative lens L22, and a biconvex positive lens L23. , And a biconcave negative lens L24. The third lens group G3 includes, in order from the object side, an aperture stop S, a biconvex positive lens L31, a positive meniscus lens L32, and a negative meniscus lens L33 having a concave surface facing the object side. The fourth lens group Gm includes, in order from the object side, a double-sided aspherical positive lens L1 having an aspheric surface on both surfaces and having a biconvex shape, a fixed stop SF, and a non-aperture made of a composite of a resin and a glass member on the object side. An aspherical negative lens L2 having a spherical surface.

In zooming, from the wide-angle end state to the telephoto end state, the air gap between the first lens group G1 and the second lens group G2 increases, and the second lens group G2 and the third lens group. This is performed by moving all the lens groups independently so that the air gap between the lens group G3 and the third lens group G3 and the fourth lens group Gm is reduced. In addition, short-distance focusing is performed by moving the second lens group G2 in the object direction.

Table 1 shows the specification values of this embodiment. In the overall specifications, f is the focal length, FNO is the F number, 2ω
Indicates an angle of view. In the lens data,
ri is the radius of curvature of the lens surface Ri, di is the distance between the lens surfaces Ri and Ri + 1 on the optical axis, and ni is the refraction of the d-line of the medium between the lens surfaces Ri and Ri + 1. The ratio, νi, is the Abbe number of the medium between the lens surface Ri and the lens surface Ri + 1, and BF is the back focus. Further, “ ^En ” in the aspherical surface data represents “× 10 ⁻ⁿ ”.

For the aspherical surface shown in the specification table, the distance (sag amount) along the optical axis direction from the tangent plane of the apex of each aspherical surface at the height y in the vertical direction from the optical axis is defined as S (y). Let R be the radius of curvature, κ be the conic coefficient, and Cn be the n-th order aspherical coefficient.

[0048]

## EQU1 ## 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

In the aspherical surface in the specification table (lens data),
The surface number is marked with a star, and the paraxial radius of curvature is entered in the r column. In the specification table (variable interval data), β indicates the imaging magnification between the object and the image, 1-POS indicates infinity focusing at the wide angle end, and 2-POS indicates infinity at the intermediate focal length state. 3-POS indicates focusing at infinity at the telephoto end, 4-POS indicates focusing at β = −0.03333 at the wide angle end, and 5-POS indicates β = − at the intermediate focal length state. When focusing at 0.03333, 6-POS indicates focusing at the telephoto end at β = −0.03333, 7-POS indicates focusing at close range at the wide-angle end, and 8-POS.
POS is a 9-PO
S indicates the state at the telephoto end when focusing on a short distance. In addition, the unit of the focal length, radius of curvature, surface spacing and other lengths of the specification table are generally `` mm '', but the same optical performance can be obtained even if the optical system is proportionally enlarged or reduced, It is not limited to this. The above description is the same in other embodiments.

[0050]

(Table 1) (Overall specifications) f = 29.1 to 192 mm 2ω = 74.1 ° to 11.8 ° FNO = 3.6 to 5.9 (lens data) rd ν n 1) 85.2964 1.8000 23.78 1.846660 2 52.3479 6.8000 60.09 1.640000 3) -11096.9620 0.1000 1.000000 4) 57.2728 3.8500 82.52 1.497820 5) 232.6502 D5 1.000000 6) ★ 113.7061 0.0500 38.09 1.553890 7) 98.4767 1.6000 42.72 1.834810 8) 15.1317 4.8000 1.000000 9) -49.0060 0.9000 49.61 1.500 0.1000 1.000000 11) 25.8325 3.5000 22.76 1.808090 12) -56.8121 0.9500 1.000000 13) -25.2334 0.9000 49.61 1.772500 14) 500.0000 D14 1.000000 15> Aperture stop 0.5000 1.000000 16) 24.4453 4.3000 82.52 1.497820 17) -38.9608 0.1000 1.000000 18) 23.8212 2.0500 82.52 1.497820 19) 46.3499 2.7000 1.000000 20) -24.7866 1.0000 23.78 1.846660 21) -55.6820 D21 1.000000 22) ★ 103.4624 3.5000 64.10 1.516800 23) ★ -29.2538 0.0000 1.000000 24) Fixed throttle 7.8500 1.000000 25) ★ -311.1355 0.2000 38.09 1.553890 26) -10 0.0000 1.3000 46.58 1.804000 27) 125.3392 BF 1.000000 (Aspheric coefficient) Surface κ C3 C4 C6 6 6.2788 -0.11851E-5 1.41700E-6 -9.06140E-9 C8 C10 C12 -8.32020E-11 1.34880E-12 -0.38798E -14 surface κ C3 C4 C6 22 -99.9999 -0.23379E-5 -1.61500E-5 -2.10980E-7 C8 C10 7.43050E-10 1.73820E-11 surface κ C3 C4 C6 23 2.1022 -0.35074E-5 -1.26210E -5 -5.83470E-8 C8 C10 C12 -4.50420E-10 2.23330E-11 -0.32891E-14 surface κ C3 C4 C5 25 576.7229 -0.69399E-5 -3.82770E-5 0.65412E-7 C6 C8 C10 -5.66570 E-9 -7.01160E-10 3.79140E-12 C12 0.16919E-13 (Variable interval data) 1-POS 2-POS 3-POS f 29.1 50 192 D0 ∞ ∞ ∞ D5 2.16928 9.21209 38.15808 D14 19.14864 12.10583 0.80311 D21 5.75080 3.31464 1.46943 4-POS 5-POS 6-POS β -0.03333 -0.03333 -0.03333 D0 825.2688 1429.7337 5065.4811 D5 1.59450 8.75909 36.58228 D14 19.72342 12.55883 2.37891 D21 5.75080 3.31464 1.46943 7-POS 8-POS 9-POS β -0.08067 -0.13669 -0.31493 0 314.9335 299.9877 259.2589 D5 0.79962 7.41055 29.9014 2 D14 20.51830 13.90737 9.05977 D21 5.75080 3.31464 1.46943 (Conditional value) (1) Σdw / ft = 0.395 (2) f1 / ft = 0.418 (3) | f2 | /ft=0.0768 (4) dpn /Dm=0.611 (5) f3 / fm = 0.391 (6) np = 1.80909 (7) vp = 22.76

FIGS. 2, 3 and 4 are aberration diagrams of the first embodiment when focused on infinity at the wide-angle end state, aberration diagrams on focusing on infinity at the intermediate focal length state, and infinity at the telephoto end state. It is an aberration figure at the time of focusing. In the aberration diagram, FNO is the F number, Y
Indicates an image height, and d and g indicate aberration curves of d-line and g-line, respectively. Regarding astigmatism, a solid line indicates a sagittal image plane, and a dotted line indicates a meridional image plane. Hereinafter, the same applies to the aberration diagrams of all the examples. As is clear from the aberration diagrams, in the present embodiment, in each state of the wide-angle end state, the intermediate focal length state, and the telephoto end state, various aberrations are well corrected while covering up to a large angle of view. .

(Second Embodiment) FIG. 5 shows the configuration of an ultra-compact zoom lens according to the second embodiment and the locus of movement thereof. In order from the object side, a first lens group G1 having a positive refractive power and a second lens group G2 having a negative refractive power
, A third lens group G3 having a positive refractive power, and a fourth lens group Gm having a positive refractive power.

The first lens group G1 includes, in order from the object side, a cemented positive lens L11 composed of a cemented negative meniscus lens having a convex surface facing the object side and a positive lens, and a positive meniscus lens L12 having a convex surface facing the object side. It is composed of Second
The lens group G2 has, in order from the object side, a negative meniscus lens L21 having an aspheric surface on the object side, made of a composite of a resin and a glass member, a biconcave negative lens L22, and a biconvex positive lens L23. , And a biconcave negative lens L24. The third lens group G3 includes, in order from the object side, an aperture stop S, a biconvex positive lens L31, a biconvex positive lens L32, and a biconcave negative lens L33. The fourth lens group Gm includes, in order from the object side, a double-sided aspheric positive lens L1 having an aspheric surface on both surfaces and an aspheric negative lens L2 having an aspheric surface on the object side surface.

During zooming, the air gap between the first lens group G1 and the second lens group G2 increases from the wide-angle end state to the telephoto end state, and the second lens group G2 and the third lens group G3 Is performed by moving all the lens groups independently so that the air gap between the third lens group G3 and the fourth lens group Gm is reduced. In addition, short-distance focusing is performed by moving the second lens group G2 in the object direction.
Table 2 shows the specification values of the second embodiment.

[0055]

[Table 2] (Overall specifications) f = 29.1 to 192 mm 2ω = 75.72 ° to 12.2 ° FNo = 3.6 to 5.9 (lens data) rd ν n 1) 87.5279 1.8000 23.78 1.846660 2 ) 53.1253 6.5000 58.54 1.651600 3) -5701.5805 0.1000 1.000000 4) 57.4865 4.0000 82.52 1.497820 5) 226.2795 D5 1.000000 6) 234.4399 0.1000 38.09 1.553890 7) 200.0000 1.6000 46.58 1.804000 8) 15.4471 4.5000 1.000000 9) -41.8184 0.8000 46.58 1.80 0.2000 1.000000 11) 25.9036 3.8000 25.43 1.805180 12) -34.9386 0.6000 1.000000 13) -24.6319 0.8000 46.58 1.804000 14) 93.9444 D14 1.000000 15> Aperture stop 0.5000 1.000000 16) 32.9805 2.8000 70.41 1.487490 17) -96.6873 0.1000 1.000000 18) 22.2785 5.0000 65.47 1.603000 19) -26.7618 0.3000 1.000000 20) -24.6754 0.8000 34.96 1.801000 21) 62.9378 D21 1.000000 22) ★ 36.7066 4.5000 64.10 1.516800 23) ★ -126.1978 9.3824 1.000000 24) ★ -49.8973 1.6000 49.61 1.772500 25) -74.7878 BF 1.000000 (Aspherical) Number) surface κ C4 C6 C8 C10 6 1.0000 1.74130E-6 -3.42140E-8 3.14560E-10 -6.55690E-13 22 5.8537 2.59170E-5 2.64070E-7 2.05700E-9 1.98630E-11 23 141.6794 6.12670E -5 3.95820E-7 5.44070E-10 7.23820E-11 24 1.2657 -2.35230E-5 -5.14680E-8 -3.57100E-10 3.87290E-12 (Variable interval data) 1-POS 2-POS 3-POS f 29.1 50 192 D0 ∞ ∞ ５ D5 2.33792 11.58687 38.76375 D14 19.38779 12.74116 0.95866 D21 5.25943 2.96326 0.99363 4-POS 5-POS 6-POS β -0.03333 -0.03333 -0.03333 D0 819.1429 1414.9776 5002.932 D5 1.76314 11.08415 37.03206 3.208388. 0.99363 7-POS 8-POS 9-POS β -0.08146 -0.13528 -0.30970 D0 305.3047 289.9969 251.0323 D5 0.95506 9.61720 30.20712 D14 20.77065 14.71083 9.51529 D21 5.25943 2.96326 0.99363 (Conditional value) (1) Σdw / ft = 0.400 (2) ) F1 / ft = 0.418 (3) | f2 | /ft=0.0768 (4) dpn / dm = 0.606 (5) f3 / fm = 0.491 (6) np = 1.80518 (7) vp = 25.43

FIGS. 6, 7 and 8 are aberration diagrams of the second embodiment when focused on infinity at the wide-angle end state, aberration diagrams on focusing on infinity at the intermediate focal length state, and infinity at the telephoto end state. It is an aberration figure at the time of focusing. As is clear from the aberration diagrams, in the present embodiment, in each state of the wide-angle end state, the intermediate focal length state, and the telephoto end state, various aberrations are well corrected while covering up to a large angle of view. .

(Third Embodiment) FIG. 9 shows a lens configuration of an ultra-compact zoom lens according to a third embodiment and the movement locus thereof. In order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, a third lens group G3 having a positive refractive power, and a positive refractive power The fourth lens group Gm is composed of four groups: positive, negative, positive, and positive.

The first lens group G1 includes, in order from the object side, a cemented positive lens L11 composed of a cemented negative meniscus lens having a convex surface facing the object side and a positive lens, and a positive meniscus lens L12 having a convex surface facing the object side. It is composed of Second
The lens group G2 has, in order from the object side, a negative meniscus lens L21 having an aspheric surface on the object side, made of a composite of a resin and a glass member, a biconcave negative lens L22, and a biconvex positive lens L23. , And a biconcave negative lens L24. The third lens group G3 includes, in order from the object side, an aperture stop S, a biconvex positive lens L31, and a cemented positive lens L32 formed by joining a biconvex positive lens and a biconcave negative lens. You. The fourth lens group Gm includes, in order from the object side, a double-sided aspherical positive lens L1 having an aspheric surface on both surfaces and a biconvex shape, and an aspherical negative meniscus lens L2 having an aspheric surface on the object side surface. Consists of

In zooming, the air gap between the first lens group G1 and the second lens group G2 increases from the wide-angle end state to the telephoto end state, and the second lens group G2 and the third lens group G3
Is performed by moving all the lens groups independently so that the air gap between the third lens group G3 and the fourth lens group Gm is reduced. In addition, short-distance focusing is performed by moving the second lens group G2 in the object direction.

[0060]

[Table 3] (Overall specifications) f = 29.1 to 192 mm 2ω = 75.98 to 12.21 ° FNo = 3.6 to 5.9 (lens data) rd ν n 1) 76.7545 1.8000 23.78 1.846660 2) 48.6074 6.4000 58.54 1.651600 3) 1026.1021 0.1000 1.000000 4) 59.9580 3.8000 82.52 1.497820 5) 235.0890 D5 1.000000 6) ★ 128.8373 0.0500 38.09 1.553890 7) 120.0000 1.6000 42.72 1.834810 8) 15.2404 4.6000 1.000000 9) -41.5181 0.8000 52.67 1.741000 1000000 11) 27.4299 3.2000 23.78 1.846660 12) -57.7463 1.0000 1.000000 13) -26.3624 0.8000 49.61 1.772500 14) 6663.8990 D14 1.000000 15> Aperture stop 0.5000 1.000000 16) 30.7236 3.0000 64.10 1.516800 17) -90.0392 0.1000 1.000000 18) 22.8071 5.2000 65.47 1.603000 19) -23.2674 1.5000 37.17 1.834000 20) 56.1488 D20 1.000000 21) ★ 45.7569 3.0000 64.10 1.516800 22) ★ -55.8518 3.0000 1.000000 23) Fixed aperture 7.0401 1.000000 24) -21.0825 1.6000 42.24 1.799520 25) -27.3149 BF 1.000000 (non-spherical) Coefficient) Surface κ C4 C6 C8 C10 6 1.0000 1.08270E-6 -3.32900E-8 2.73850E-10 -6.80120E-13 21 -0.3603 -7.05470E-7 2.38510E-8 -3.20800E-12 -7.27680E-12 22 1.0000 -3.71520E-6 -5.71920E-8 -3.30780E-10 -5.13670E-12 24 1.2657 -2.93730E-5 -1.08010E-7 -1.18720E-9 -1.08530E-12 (Variable interval data) 1 -POS 2-POS 3-POS f 29.1 50 192 D0 ∞ ∞ ５ D5 2.17796 11.42691 38.60379 D14 19.49011 12.84348 1.06098 D20 5.27034 2.97417 1.00454 4-POS 5-POS 6-POS β -0.03333 -0.03333 -0.03333 D0 819.1429 1414.9776 5002.932 D5 1.60318 10.92419 36.87210 D14 20.06489 13.34620 2.79267 D20 5.27034 2.97417 1.00454 7-POS 8-POS 9-POS β -0.08146 -0.13528 -0.30970 DO 305.3047 289.9969 251.0323 D5 0.79510 9.45724 30.04716 D14 20.87297 14.81315 9.61761 974 5.100 Σdw / ft = 0.297 (2) f1 / ft = 0.418 (3) | f2 | /ft=0.0768 (4) dpn dm = 0.686 (5) f3 / fm = 0.491 (7) νp = 23.78

FIGS. 10, 11, and 12 are aberration diagrams at the wide-angle end state when focused on infinity, in the intermediate focal length state when focused on infinity, and at the telephoto end state, respectively. It is an aberration figure at the time of far focus. As is clear from the aberration diagrams, in the present embodiment, in each state of the wide-angle end state, the intermediate focal length state, and the telephoto end state, various aberrations are well corrected while covering up to a large angle of view. .

Although the aperture stop in each of the above embodiments is provided immediately before the third lens group G3, it may be disposed inside the third lens group G3 or immediately before the fourth lens group Gm. Also,
The aspherical surface introduced in the present invention is composed of an element which produces the same effect as a result, for example, a gradient index optical element or a diffractive optical element, a hybrid of a diffractive element and a refractive element. It goes without saying that the present invention is within the scope of the present invention even if it is replaced with a diffraction hybrid type optical element.

[0063]

As described above, according to the present invention,
It has an angle of view of 2ω = 74.1 ° to 11.8 °, has a small diameter and size down to the limit with a zoom ratio of about 6.6, has a small number of components, and has excellent cost performance.
In addition, an ultra-compact zoom lens with high performance and high magnification can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing a lens configuration and a movement locus of an ultra-compact zoom lens according to a first embodiment of the present invention.

FIG. 2 is an aberration diagram for focusing on infinity in the wide-angle end state of the first embodiment.

FIG. 3 is an aberration diagram for focusing on infinity in the intermediate focal length state according to the first embodiment.

FIG. 4 is an aberration diagram for focusing on infinity in the telephoto end state of the first embodiment.

FIG. 5 is a diagram illustrating a lens configuration and a movement locus of an ultra-compact zoom lens according to a second embodiment of the present invention.

FIG. 6 is an aberration diagram for focusing on infinity at the wide-angle end in the second embodiment.

FIG. 7 is an aberration diagram for focusing on infinity in the intermediate focal length state according to the second embodiment.

FIG. 8 is an aberration diagram for focusing on infinity in the telephoto end state of the second embodiment.

FIG. 9 is a diagram showing a lens configuration and a movement locus of an ultra-compact zoom lens according to a third embodiment of the present invention.

FIG. 10 is an aberration diagram for focusing on infinity at the wide-angle end in the third embodiment.

FIG. 11 is an aberration diagram for focusing on infinity in an intermediate focal length state according to the third embodiment.

FIG. 12 is an aberration diagram for focusing on infinity in the telephoto end state of the third embodiment.

[Explanation of symbols]

 G1 ... first lens group G2 ... second lens group G3 ... third lens group Gm ... lens group S ... aperture stop SF ... fixed aperture

Continued on the front page F term (reference) 2H087 KA02 MA13 PA10 PA11 PA17 PA18 PB12 QA02 QA06 QA07 QA17 QA21 QA25 QA37 QA39 QA41 QA46 RA05 RA12 RA13 RA32 SA23 SA27 SA29 SA32 SA62 SA63 SA64 SA65 SB04 SB15 SB24 SB25 SB32 SB33

Claims (10)

[Claims] 1. A first lens having a positive refractive power in order from the object side.
A lens group G1 and a second lens group G2 having negative refractive power
And at least one lens group, and a lens group Gm having a positive refractive power as a whole. The magnification is changed by changing the air gap between the first lens group G1 and the second lens group G2. In the ultra-compact zoom lens, the lens group Gm includes, in order from the object side, a positive lens component L1 having a convex surface facing the image side and a negative lens component L2 having a concave surface facing the object side. Is the length on the optical axis from the object side vertex of the lens component closest to the object side to the image side vertex of the lens component closest to the image side is Σdw, and the focal length of the entire zoom lens system at the telephoto end is ft.
An ultra-compact zoom lens that satisfies the following conditions. (1) 0.10 <Σdw / ft <0.54 2. The ultra-compact zoom lens according to claim 1, wherein the following condition is satisfied when the focal length of said first lens group G1 is f1. (2) 0.20 <f1 / ft <0.55 3. The ultra-compact zoom lens according to claim 1, wherein the following condition is satisfied when the focal length of said second lens group G2 is f2. (3) 0.03 <| f2 | / ft <0.20 4. The length on the optical axis from the image-side vertex of the positive lens component L1 in the lens group Gm to the object-side vertex of the negative lens component L2 is dpn, and the lens closest to the object side in the lens group Gm. 4. The following condition is satisfied when a length on the optical axis from the object-side vertex of the component to the image-side vertex of the lens component closest to the image is defined as dm. 2. An ultra-compact zoom lens according to item 1. (4) 0.23 <dpn / dm <0.90 5. The method according to claim 1, wherein at least one of the aspheric surfaces is provided in one of the positive lens component L1 and the negative lens component L2 in the lens group Gm. The ultra-compact zoom lens described. 6. The at least one lens group comprises only a third lens group G3 having a positive refractive power, wherein the focal length of the third lens group G3 is f3, and the focal length of the lens group Gm is fm. Wherein the following conditions are satisfied:
An ultra-compact zoom lens according to any one of the preceding claims. (5) 0.2 <f3 / fm <1.0 7. The positive lens component L1 in the lens group Gm
And both the negative lens component L2 and the negative lens component L2 have at least one aspheric surface, and at least one of the aspheric surfaces has a positive lens unit positive as going from the optical axis toward the lens periphery. The ultra-compact zoom lens according to any one of claims 1 to 6, wherein the zoom lens has a shape in which a refractive power is weakened or a shape in which a negative refractive power of a single lens is increased. 8. The positive lens component L1 in the lens group Gm is constituted by a double-sided aspherical surface, and the aspherical surface on the image side of the double-sided aspherical lens has a portion around the effective diameter as compared with the curvature on the optical axis. The ultra-compact zoom lens according to any one of claims 1 to 7, wherein the zoom lens has a shape having a large curvature. 9. The negative lens component L2 in the lens group Gm has at least one aspherical surface, and the aspherical surface has a negative refractive power at an outermost peripheral portion of an effective diameter than on the optical axis. The ultra-compact zoom lens according to any one of claims 1 to 8, wherein the zoom lens has a shape. 10. The lens system according to claim 1, wherein the second lens group includes at least one lens.
10. A lens system according to claim 1, comprising: a negative lens component and a positive lens component, wherein when the refractive index of the positive lens component with respect to d-line is np and the Abbe number is νp, the following conditions are satisfied. An ultra-compact zoom lens according to any one of the preceding claims. (6) np <1.85 (7) νp <27