KR100458547B1 - zoom lens - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens, comprising: a first lens unit having positive refractive power in the form of a meniscus in which an object side is convex sequentially, a second lens unit having both surfaces concave and negative refractive power, and convex on both sides A first lens group comprising a third lens unit having positive refractive power and a fourth lens unit having positive refractive power convex on both surfaces thereof, and having a positive refractive power as a whole; A fifth lens unit having a convex positive refractive power of the image side and a sixth lens unit having at least one lens having negative refractive power of the meniscus shape of which the image is convex, and a second lens group having a negative refractive power as a whole. And the interval between the first lens group and the second lens group is changed at the time of shifting, the second lens group includes at least one aspherical surface, and the following conditions 0.88 <Lt / ft <0.93, 0.50 <┃ It satisfies fII / fw <0.70 and fII <0, aims to reduce the size and weight of the entire lens system, and has a ratio of about 2.0 times.

Description

zoom lens

This invention relates to a zoom lens, and more particularly, to a zoom lens.

In recent years, zoom lenses have been miniaturized, and at the same time, the brightness of the lenses is gradually becoming less bright, that is, the direction in which the aperture ratio becomes smaller. In addition, the number of lenses is gradually decreasing due to intensifying price competitiveness due to the shipment of many products, and the use of aspherical lenses is gradually increasing.

Conventionally, a zoom lens composed of a first lens group having a positive refractive power and a second lens group having a negative refractive power is sequentially provided from an object side, and a zoom lens for changing a distance by changing a distance between the first lens group and a second lens group is proposed. It became.

As the zoom lens of this type, the following technology is disclosed.

1) Japanese Patent Application Laid-Open No. 4-124607

2) Japanese Patent Application Laid-open No. Hei 4-161914

3) Japanese Patent Application Laid-Open No. 6-281860

4) Japanese Patent Application Laid-open No. Hei 7-146440

5) Japanese Patent Application Laid-Open No. 7-181382

6) Japanese Patent Application Laid-open No. Hei 7-261078

7) US Patent 5,459,626

8) US Patent 5,463,499

The above-described prior arts relate to a zoom lens for arranging positive and negative refractive powers sequentially from the object side to shorten the postfocal distance as much as possible and at the same time shortening the lens system electric field to have high optical performance.

In a zoom lens having a two-group configuration including a first lens group having a positive refractive power and a second lens group having a negative refractive power as described above, the entire lens system can be miniaturized and at the same time have a full magnification ratio of about 2 times. In order to obtain good optical performance over the area, the lens configuration of each lens group must be appropriately set.

However, the zoom lens described in 1) above has only 1.5 times of magnification ratio and three aspherical surfaces. In addition, the zoom lens described in 2) has only a double magnification ratio, adopts two aspherical surfaces, and consists of a total of seven lenses.

In addition, the zoom lens described in 3) uses at least two aspherical surfaces, the angle of view at the wide-angle end is 57.6 °, not wide-angle, and the focal length at the wide-angle end is f = 39 mm or more.

In addition, the zoom lens described in the above 4) uses an aspherical surface on one surface and is not wide-angle with an angle of view of 57.9 degrees. The zoom lens described in 5) and 6) has an angle of view of 59.3 ° and adopts at least three aspherical surfaces at the same time.

In addition, the zoom lens described in 5) has an angle of view of 57.6 degrees, a ratio of magnification of only 1.7 times, and one or more aspherical surfaces are used.

Further, the zoom lens described in 6) has an angle of view of 57.8 ° and employs about five aspherical surfaces.

As described above, the conventional techniques are not relatively wide-angle and have a disadvantage in that manufacturing cost is increased due to increased use of aspherical surfaces.

The present invention has been made to solve the above-mentioned drawbacks, and it is intended to provide a compact zoom lens having a good aberration performance over the entire variable range while having a variable ratio of about 2 times.

The configuration of the present invention for achieving the above object,

From the object side sequentially,

A first lens unit having a positive refractive power of a meniscus shape in which an object side is convex, a second lens unit having a concave and negative refractive power on both sides, a third lens unit having a positive refractive power on both sides, and a convex definition on both sides A first lens group comprising a fourth lens unit having refractive power and having a positive refractive power as a whole;

A fifth lens unit having a convex positive refractive power of the image side and a sixth lens unit having at least one lens having negative refractive power of the meniscus shape of which the image is convex, and a second lens group having a negative refractive power as a whole. under,

The interval between the first lens group and the second lens group is changed at the time of shifting, and the second lens group includes at least one aspherical surface and satisfies the following conditions.

(Condition 1)

0.88 <Lt / ft <0.93

Lt represents the distance on the optical axis from the first lens plane to the image plane in the telephoto end of the entire lens system, and ft represents the focal length of the entire lens system in the telephoto end.

The constitution of this invention for achieving the above object satisfies further including the following conditions.

(Condition 2)

0.50 <┃fII┃ / fw <0.70

fⅡ <0

FII denotes a focal length of the second lens group, and fw denotes a focal length of the entire lens system at the wide-angle end.

The constitution of this invention for achieving the above object satisfies further including the following conditions.

(Condition 3)

1.90 <fI / fbw <2.5

(Condition 4)

1.0 <Ldw / fI <1.40

FI denotes the focal length of the first lens group, fbw denotes the postfocal distance of the entire lens system at the wide-angle end, and Ldw is the lens surface closest to the image side of the first lens surface at the wide-angle end. The distance on the optical axis is shown.

The constitution of this invention for achieving the above object satisfies further including the following conditions.

(Condition 5)

40 <fI × Zr <50

Zr represents a ratio of the entire lens system.

(Condition 6)

35 <┃fII × Zr┃ <45

LY represents the maximum height (image height) of the upper surface.

The constitution of this invention for achieving the above object satisfies further including the following conditions.

(Condition 7)

0.75 <fw / LY <0.90

The constitution of this invention for achieving the above object satisfies further including the following conditions.

(Condition 8)

0.55 <SUDw / LY <0.75

The SUDw represents an air gap between the first lens group and the second lens group in the telephoto end.

The above-described configuration will be described in detail with reference to the accompanying drawings the most preferred embodiment that can be easily implemented by those skilled in the art to which the present invention pertains.

1A to 1B are lens configuration diagrams at respective zoom positions of the zoom lens according to the first embodiment of the present invention.

2 is an aberration diagram at the wide-angle end of the zoom lens according to the first embodiment of the present invention;

3 is aberration diagrams at the telephoto end of the zoom lens according to the first embodiment of the present invention;

4A to 4B are lens configuration diagrams at respective zoom positions of the zoom lens according to the second embodiment of the present invention.

5 is an aberration diagram at the wide-angle end of the zoom lens according to the second embodiment of the present invention;

6 is aberration diagrams at the telephoto end of the zoom lens according to the second embodiment of the present invention;

7A to 7B are lens configuration diagrams at respective zoom positions of the zoom lens according to the third embodiment of the present invention.

8 is an aberration diagram at the wide-angle end of the zoom lens according to the third embodiment of the present invention;

9 is aberration diagrams at the telephoto end of the zoom lens according to the third embodiment of the present invention.

1A, 4A, and 7A, the zoom lens according to the embodiment of the present invention is constructed as follows.

From the object side sequentially,

A first lens unit 1 having positive meniscus-shaped positive refractive power in which the object side is convex, a second lens unit 2 having both surfaces concave and negative refractive power, and a third lens unit having positive refractive power in which both surfaces are convex A first lens group I composed of a fourth lens unit 4 having positive refractive power convex on both surfaces thereof, and having positive refractive power as a whole;

A fifth lens unit 5 having convex positive refractive power at the image side and a sixth lens unit 6 having at least one lens having negative refractive power in the meniscus shape at which the image side is convex, and having negative refractive power as a whole. And a second lens group II.

The interval between the first lens group I and the second lens group II is changed at the time of shifting, and the second lens group I includes at least one aspherical surface.

The first, second, third, fourth, and fifth lens units 1 to 5 according to the exemplary embodiment of the present invention each include one lens, and the sixth lens unit 6 includes one sheet. Or two lenses.

The operation of the zoom lens according to the embodiment of the present invention by the above configuration is as follows.

Conditional Expression 1 above relates to a telephoto ratio.

In general, the larger the telephoto ratio, the longer the total length of the telephoto end, so that the telephoto ratio is not desirable for compactness. When the conditional expression 1 is satisfied, the length of the electric field becomes very short compared to the focal length of the telephoto end, and the amount of movement of the lens system becomes very small, making it easy to compact.

Therefore, the conditional formula 1 defines an appropriate range for the ultra-small telephoto ratio, and when the upper limit of the conditional formula 1 is exceeded, the telephoto ratio becomes large, making it difficult to compact the lens system.

On the contrary, in the case where the lower limit value of the conditional expression 1 is exceeded, the lens system becomes dark, that is, the aperture ratio becomes small or the aspherical surface of the lens must be increased more, which makes the lens processing difficult.

The conditional expression 2 relates to the refractive power of the second lens group II, and is intended to reduce the aberration fluctuations while attaining a reduction ratio of the entire lens system while simultaneously shifting and changing the whole lens system. .

When the lower limit value of Condition 2 is exceeded, the refractive power of the second lens group II becomes so strong that a desired variation ratio can be easily obtained, but it is difficult to properly correct image surface curvature and distortion over the entire variation region. .

When the upper limit value of the conditional expression 2 is exceeded, the refractive power of the second lens group II becomes too weak, and the postfocal distance of the entire lens system becomes too short, thereby increasing the second lens group II. In addition, the movement amount of the second lens group II is increased in order to secure a desired variable ratio, thereby increasing the overall length of the entire lens system.

Condition 3 is to properly set the positive refractive power of the first lens group I to properly correct the balance of all aberrations over the entire variation area, and Condition 4 is the first lens with respect to the thickness of the entire lens system. It is for setting the refractive power of group I suitably.

When the lower limit value of the conditional expression 3 and the upper limit value of the conditional expression 4 are exceeded, the refractive power of the first lens group I becomes so strong that aberration fluctuations during shifting, in particular, spherical aberration, coma aberration, and the like increase.

When the upper limit value of the conditional expression 3 and the lower limit value of the conditional expression 4 are exceeded, the refractive power of the first lens group I becomes too weak, and the back focal length at the wide-angle end becomes short. Therefore, the effective diameter of the second lens group II is increased.

Conditional Expression 5 is for the lens system to perform the focus adjustment function, and defines the relationship between the focal length and the magnification ratio of the first lens group I.

First, when the focal length of the first lens group I exceeds the upper limit of Conditional Expression 5, that is, the ratio of magnification is fixed, the focal length of the first lens group I is increased to exceed the upper limit of Conditional Expression 5 above. In this case, the variable ratio becomes relatively small. Therefore, the magnification by the second lens group II is reduced. As a result, the aberration performance can be corrected well, but the rear focus distance is shortened, so that the outer diameter of the lenses of the second lens group II, that is, the rear lens group, becomes large, making it difficult to compact.

In addition, when the variable ratio exceeds the upper limit of Condition 5, that is, when the ratio increases when the focal length of the first lens group I is fixed and exceeds the upper limit of Condition 5, the lens at the telephoto end. The brightness becomes dark, that is, the aperture ratio becomes small, and the correction of spherical aberration becomes difficult.

On the contrary, when the focal length of the first lens group I exceeds the lower limit of Condition 5, that is, the variable ratio is fixed, the focal length of the first lens group I is reduced to reduce the lower limit of Condition 5 If it exceeds, the magnification by the second lens group II becomes large. Therefore, the aperture ratio of the first lens group I becomes small, and it is difficult to correct the spherical aberration.

In addition, when the variable ratio exceeds the lower limit of Condition 5, that is, when the ratio is reduced while the focal length of the first lens group I is fixed and exceeds the lower limit of Condition 5, the optical system becomes large. This makes it difficult to compact the entire lens system.

The conditional expression 6 above defines the relationship between the ratio and the focal length of the second lens group II.

First, when the focal length of the second lens group II exceeds the upper limit of the conditional expression 6, that is, the ratio of the magnification ratio is fixed and the focal length of the second lens group II increases to exceed the upper limit of the conditional expression 6 above. In this case, the length of the entire lens system becomes larger than the distance that the second lens group II moves, which is undesirable.

In addition, when the variable ratio exceeds the upper limit of Condition 6, that is, when the ratio is increased while the focal length of the second lens group II is fixed and exceeds the upper limit of Condition 6, the second lens group ( II) should be high magnification, or asymmetrical component of coma aberration according to angle of view, curvature of top, distortion, etc. occur.

On the contrary, when the focal length of the second lens group II exceeds the lower limit of Condition 6, that is, the shift ratio is fixed, the focal length of the second lens group II decreases to reduce the lower limit of Condition 6 If it exceeds, the shift amount of the first lens group I due to the shift becomes small and the lens length becomes short. However, at the same time, the postfocal distance becomes short, and the lens mirror of the second lens group II becomes too large.

In addition, when the shift ratio exceeds the lower limit of Condition 6, that is, when the shift ratio decreases while the focal length of the second lens group II is fixed and exceeds the lower limit of Condition 6, the overall length of the entire lens system is reduced. This becomes large and compactness becomes difficult.

The conditional equation 7 relates to the ratio of the focal length at the wide-angle end and the diagonal length of the effective screen. The conditional lens 7 is a zoom lens composed of two groups, which enables miniaturization of the whole, and at the same time, corrects aberrations over the entire variation area, and improves the wide angle. This is to appropriately set the photographing angle of view at the stage to the wide angle.

When the upper limit value of the above Conditional Expression 7 is exceeded, the focal length of the wide-angle end becomes too long, and the overall length of the entire lens system becomes long. On the contrary, when the lower limit value of Condition 7 is exceeded, the focal length at the wide-angle end becomes too short and the lens diameter becomes large, and at the same time, the variation of all aberrations around the screen increases at the time of change, which is very correct. Becomes difficult.

The conditional expression 8 above defines the distance on the optical axis from the first lens surface (lens surface closest to the object side) of the entire lens system to the final surface (lens surface closest to the image side) at the wide-angle end so as to be suitable for miniaturization of the entire lens system. It is.

When the upper limit of Conditional Expression 8 is exceeded, the overall length of the lens system at the wide-angle end is increased, making it difficult to miniaturize. On the contrary, when the lower limit value of the conditional expression 8 is exceeded, when the axial thickness of the lens system is reduced, the distance between the first lens group I and the second lens group II becomes too narrow or the second lens group ( The thickness on the optical axis of II) becomes small. Therefore, the thickness of the meniscus-shaped lens having the positive refractive power of the second lens group II and the meniscus-shaped lens having the negative refractive power becomes thin.

Since the formula for the aspherical surface of the zoom lens according to the embodiment of the present invention is a widely used formula, the description of the specific formula is omitted.

Next, a number of embodiments of the present invention having the above configuration and satisfying the above conditional expressions 1 to 12 will be described.

The zoom lens according to the first exemplary embodiment of the present invention is a case in which the sixth lens unit 6 of the second lens group II is composed of one lens, as shown in FIG. 1. A diaphragm 10 is attached to the upper side of the

F is the focal length, ri (i = 1 to 13, 14) is the radius of curvature of the refractive surface, di (i = 1 to 13,14) is the thickness of the lens or the distance between the lenses, N is the The d-line refractive index, v represents the Abbe's number of the lens.

The aperture value Fno of the zoom lens according to the first embodiment of the present invention is 4.50 to 8.31, the focal length f is 36.40 to 67.21, and the embodiment values are shown in Table 1 below.

* Denotes an aspherical surface, and aspheric coefficients are shown in Table 2 below.

In the zoom lens according to the second exemplary embodiment of the present invention, as shown in FIGS. 3A and 3B, when the sixth lens unit 6 of the second lens group II includes two lenses 6 and 61. The other lens configuration is the same as that of the above-described first embodiment. An aperture diaphragm 10 is mounted between the first lens group I and the second lens group II.

The aperture value Fno of the zoom lens according to the second embodiment of the present invention is 4.70 to 9.67, the focal length f is 36.53 to 75.16, and the embodiment values are shown in Table 3 below.

Aspheric coefficients are shown in Table 4 below.

As shown in FIG. 7, the zoom lens according to the third embodiment of the present invention has the same configuration as that of the first embodiment, and has an aperture diameter between the first lens group I and the second lens group II. 10) and the light shielding mirror 11 are mounted.

The aperture Fno of the zoom lens according to the third exemplary embodiment of the present invention is 4.50 to 8.48, the focal length f is 36.10 to 68.00, and the exemplary values are shown in Table 5 below.

The aspherical surface coefficient is shown in Table 6 below.

Conditional expression values according to the above embodiments (1 to 3) are shown in Table 7 below.

As described above, according to the exemplary embodiment of the present invention, the lens configuration of each lens group is appropriately set, so that the entire lens system can be reduced in size and at the same time have a ratio of about 2.0 times. It is possible to provide a zoom lens that can be easily compacted.

In addition, since only one surface of the second lens group is composed of aspherical surfaces, it is possible to prevent an increase in manufacturing cost due to an increase in aspherical surface, and to maintain good performance and shorten the overall length of the telephoto end, the first lens group and the second lens group. The movement amount of the lens system can be made very simple at the time of zoom movement, that is, at the time of shifting by making the amount of movement relatively short.

1A to 1B are lens configuration diagrams at respective zoom positions of the zoom lens according to the first embodiment of the present invention.

2 is an aberration diagram at the wide-angle end of the zoom lens according to the first embodiment of the present invention;

3 is aberration diagrams at the telephoto end of the zoom lens according to the first embodiment of the present invention;

4A to 4B are lens configuration diagrams at respective zoom positions of the zoom lens according to the second embodiment of the present invention.

5 is an aberration diagram at the wide-angle end of the zoom lens according to the second embodiment of the present invention;

6 is aberration diagrams at the telephoto end of the zoom lens according to the second embodiment of the present invention;

7A to 7B are lens configuration diagrams at respective zoom positions of the zoom lens according to the third embodiment of the present invention.

8 is an aberration diagram at the wide-angle end of the zoom lens according to the third embodiment of the present invention;

9 is aberration diagrams at the telephoto end of the zoom lens according to the third embodiment of the present invention.

Claims (9)

From the object side sequentially, A first lens unit having a positive refractive power of a meniscus shape in which an object side is convex, a second lens unit having a concave and negative refractive power on both sides, a third lens unit having a positive refractive power on both sides, and a convex definition on both sides A first lens group comprising a fourth lens unit having refractive power and having a positive refractive power as a whole; A fifth lens unit having a convex positive refractive power of the image side and a sixth lens unit having at least one lens having negative refractive power of the meniscus shape of which the image is convex, and a second lens group having a negative refractive power as a whole. under, A zoom lens in which a distance between the first lens group and the second lens group is changed at the time of shifting, wherein the second lens group includes at least one aspherical surface, and satisfies the following conditions. 0.88 <Lt / ft <0.93 0.50 <┃fII┃ / fw <0.70 fⅡ <0 fII: Focal length of the second lens group fw: focal length of the entire lens system at the wide end ft: Focal length of the entire lens system from the telephoto end. Lt: Distance on the optical axis from the first lens surface to the image surface in the telephoto end of the entire lens system The zoom lens according to claim 1, further comprising the following condition. 1.90 <fI / fbw <2.5 fI: focal length of the first lens group fbw: post focal length of whole lens system from wide angle end The zoom lens according to claim 1, further comprising the following condition. 35 <┃fII × Zr┃ <45 Zr: Variable ratio of the entire lens system. From the object side sequentially, A first lens unit having a positive refractive power of a meniscus shape in which an object side is convex, a second lens unit having a concave and negative refractive power on both sides, a third lens unit having a positive refractive power on both sides, and a convex definition on both sides A first lens group comprising a fourth lens unit having refractive power and having a positive refractive power as a whole; A fifth lens unit having a convex positive refractive power of the image side and a sixth lens unit having at least one lens having negative refractive power of the meniscus shape of which the image is convex, and a second lens group having a negative refractive power as a whole. under, A zoom lens in which a distance between the first lens group and the second lens group is changed at the time of shifting, wherein the second lens group includes at least one aspherical surface, and satisfies the following conditions. 0.88 <Lt / ft <0.93 1.90 <fI / fbw <2.5 fI: focal length of the first lens group fbw: post focal length of whole lens system from wide angle end ft: Focal length of the entire lens system from the telephoto end. Lt: Distance on the optical axis from the first lens surface to the image surface in the telephoto end of the entire lens system The zoom lens of claim 4, further comprising and satisfying the following condition. 1.0 <Ldw / fI <1.40 Ldw: Distance on the optical axis from the wide-angle end to the lens surface closest to the image side of the first lens surface. The zoom lens of claim 4, further comprising and satisfying the following condition. 0.75 <fw / LY <0.90 LY: maximum appeal of the upper surface fw: focal length of the entire lens system at the wide end From the object side sequentially, A first lens unit having a positive refractive power of a meniscus shape in which an object side is convex, a second lens unit having a concave and negative refractive power on both sides, a third lens unit having a positive refractive power on both sides, and a convex definition on both sides A first lens group comprising a fourth lens unit having refractive power and having a positive refractive power as a whole; A fifth lens unit having a convex positive refractive power of the image side and a sixth lens unit having at least one lens having negative refractive power of the meniscus shape of which the image is convex, and a second lens group having a negative refractive power as a whole. under, A zoom lens in which a distance between the first lens group and the second lens group is changed at the time of shifting, wherein the second lens group includes at least one aspherical surface, and satisfies the following conditions. 0.88 <Lt / ft <0.93 1.0 <Ldw / fI <1.40 ft: Focal length of the entire lens system from the telephoto end. fI: focal length of the first lens group Lt: Distance on the optical axis from the first lens surface to the image surface in the telephoto end of the entire lens system Ldw: Distance on the optical axis from the wide-angle end to the lens surface closest to the image side of the first lens surface. 8. The zoom lens according to claim 7, further comprising the following conditions. 40 <fI × Zr <50 Zr: Variable ratio of the entire lens system. fI: focal length of the first lens group From the object side sequentially, A first lens unit having a positive refractive power of a meniscus shape in which an object side is convex, a second lens unit having a concave and negative refractive power on both sides, a third lens unit having a positive refractive power on both sides, and a convex definition on both sides A first lens group comprising a fourth lens unit having refractive power and having a positive refractive power as a whole; A fifth lens unit having a convex positive refractive power of the image side and a sixth lens unit having at least one lens having negative refractive power of the meniscus shape of which the image is convex, and a second lens group having a negative refractive power as a whole. under, A zoom lens in which a distance between the first lens group and the second lens group is changed at the time of shifting, wherein the second lens group includes at least one aspherical surface, and satisfies the following conditions. 0.88 <Lt / ft <0.93 40 <fI × Zr <50 ft: Focal length of the entire lens system from the telephoto end. Lt: Distance on the optical axis from the first lens surface to the image surface in the telephoto end of the entire lens system Zr: Variable ratio of the entire lens system. fI: focal length of the first lens group

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