JP3018803B2 - Zoom lens - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens, and more particularly to a zoom lens having a wide angle of view (zoom ratio) of about 2 to 3 at a wide angle of view (short focus) of about 62 to 75 degrees. The present invention relates to a zoom lens suitable for a small 35 mm single-lens reflex camera, a video camera, or the like having a simple lens configuration and high optical performance over the entire zoom range of the ratio.

[0002]

2. Description of the Related Art Conventionally, in a zoom lens including a wide angle of view, a first group having a negative refractive power is provided on the object side, and a position where an off-axis light beam passes through the first group in the wide angle of view is defined as an optical axis. And the outer diameter of the first lens unit is reduced to reduce the size of the entire lens system.

The applicant of the present invention has proposed a zoom lens having a high zoom ratio using such a zoom type having such a configuration, for example, in Japanese Patent Publication No. 63-58325.

In this publication, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, and a third lens unit having a negative refractive power are sequentially arranged from the object side.
A zoom lens having four lens groups, a fourth lens group having a negative refractive power, and a first, second, and third lens group being moved to perform zooming. (Hereinafter referred to as “A type zoom lens”).

The applicant of the present invention has disclosed in Japanese Patent Application Laid-Open Nos. Hei 3-240014 and Hei 3-265810 the first group of negative refractive power, the second group of positive refractive power, The zoom lens has four lens units, a third lens unit having a refractive power and a fourth lens unit having a negative refractive power. For zooming from the wide-angle end to the telephoto end,
There has been proposed a zoom lens in which the lens groups are moved so that the distance between the lens groups decreases, decreases, decreases, or increases in order (hereinafter, referred to as “B-type zoom lens”).

In Japanese Patent Application Laid-Open No. 60-87312 and Japanese Patent Publication No. 61-55094, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, and a negative lens having a negative refractive power are arranged in order from the object side. 3
Group, and a fourth lens group of positive refractive power. When zooming from the wide-angle end to the telephoto end, the lens units are moved so that the distance between the lens units decreases, increases, and decreases in order. The proposed zoom lens is referred to as a “C type zoom lens”.

In Japanese Patent Application Laid-Open No. Sho 62-153913, a first lens unit having a negative refractive power and a second lens unit having a positive refractive power are sequentially arranged from the object side.
It has five lens groups: a third lens group having a negative refractive power, a fourth lens group having a negative refractive power, and a fifth lens group having a positive refractive power. There has been proposed a zoom lens in which the lens groups are moved such that the distance between the lens groups decreases, increases, decreases, and increases or decreases in order (the distance between the fourth and fifth groups is maximum at an intermediate zoom position) (hereinafter referred to as “D”). Type zoom lens ”).

[0008]

In the case of the A type zoom lens, the zooming efficiency tends to decrease because aberration correction is performed by fixing the fourth lens unit during zooming.

The B-type zoom lens has an advantage that the overall length of the lens on the wide-angle side is short, but if the zoom ratio is to be increased, the amount of movement of the first, second, and third units tends to be large.

On the telephoto side, the distance between the first, second, and third lens units is reduced, and the entire lens system is not teletype.
Numbers tended to be dark.

In the C type zoom lens, the refractive power arrangement of each lens group is a continuous form of negative and positive, and since the principal point position of the entire system is located on the image plane side, the back focus becomes longer, and the total length of the lens becomes shorter. There was a tendency to increase.

Further, since the convergent light beam emitted from the second lens unit is diverged by the third lens unit and converged by the fourth lens unit, it is necessary to increase the refractive power of the fourth lens unit. The occurrence tended to increase.

The D-type zoom lens moves the fourth lens group so as to have a convex locus on the image surface side during zooming with respect to the divergent light beam emitted from the third lens group, from the wide-angle end to the telephoto end. The magnification with zooming to has increased and has since decreased.

The fifth lens unit is fixed during zooming, and the fourth lens unit is fixed.
An image point formed at a fixed position by the group is formed on an image plane (photosensitive surface), and does not contribute to zooming.

Since zooming is performed only in the first half of the entire zoom range of the first, second, third and fourth groups, the zooming efficiency is not very good.

Further, since the luminous flux diverged by the third and fourth groups is converged only by the fifth group, the number of lenses in the fifth group increases, and the entire lens system tends to become large.

According to the present invention, a lens unit having a negative refractive power is preceded by four lens units as a whole, and by appropriately setting a moving condition of each lens unit and a refractive power of each lens unit upon zooming. It is an object of the present invention to provide a small zoom lens having a high optical performance, including a wide angle of view region, a high zoom ratio of about 3 and a high zoom ratio, and a short overall lens length having high optical performance.

[0018]

The zoom lens according to the present invention comprises: (1-1) a first unit having a negative refractive power, a second unit having a positive refractive power, and a third unit having a negative refractive power in order from the object side. And a fourth lens unit having a negative refractive power and a fourth lens unit. Upon zooming from the wide-angle end to the telephoto end, the distance between the first and second units is reduced,
A zoom lens in which each lens group is moved so that the distance between the second group and the third group increases and the distance between the third group and the fourth group decreases, and When the focal length is fi and the focal length of the entire system at the wide-angle end is Fw, 0.5 <| f1 | / Fw <2.9 (1) f2 <| f1 |, | f3 |, | f4 | 2) It is characterized by satisfying the following conditions.

(1-2) From the object side, a first unit having a negative refractive power, a second unit having a positive refractive power, a third unit having a negative refractive power, and a fourth unit having a negative refractive power. When changing the magnification from the wide-angle end to the telephoto end, the distance between the first group and the second group decreases, and the distance between the second group and the third group increases. A zoom lens in which each lens group is moved so that the distance between the third group and the fourth group decreases, and when the distance between the i-th group and the i + 1-th group is Di, D2 + D3 = constant. Let the focal length of the i-th lens unit be f
i, when the focal length of the entire system at the wide-angle end is Fw, 0.5 <| f1 | / Fw <2.9 (1) f2 <| f1 |, | f3 |, | f4 | (2) It is characterized by satisfying the conditions.

(1-3) In order from the object side, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, a third lens unit having a negative refractive power, and a fourth lens unit having a negative refractive power. When changing the magnification from the wide-angle end to the telephoto end, the distance between the first group and the second group decreases, and the distance between the second group and the third group increases. Each lens group is moved so that the distance between the third group and the fourth group is reduced, and the second group moves the cemented lens surface by at least two.
The fourth group is a zoom lens having at least one cemented lens surface, and the focal length of the i-th group is f
i, when the focal length of the entire system at the wide-angle end is Fw, 0.5 <| f1 | / Fw <2.9 (1) f2 <| f1 |, | f3 |, | f4 | (2) It is characterized by satisfying the conditions.

[0021]

1 to 8 show numerical examples 1 to 8 of the present invention.
It is a lens sectional view of. 1, 4 and 7, (A) shows the zoom position at the wide angle end and (B) shows the zoom position at the telephoto end.

In the figure, L1 is a first lens unit having a negative refractive power, L2 is a second lens unit having a positive refractive power, L3 is a third lens unit having a negative refractive power, and L4 is a negative lens.
Denotes a fourth unit having a negative refractive power. SP is an aperture. Arrows indicate the moving direction of each lens unit when zooming from the wide-angle side to the telephoto side.

When zooming from the wide-angle end to the telephoto end, the zoom lens according to the present embodiment appropriately sets the refractive power, the zoom ratio, and the like of the first to fourth groups as shown in each figure. Each of the second to fourth units is independently moved in the object side direction, and the first unit is moved so as to have a locus convex toward the image plane side. The stop SP is moved integrally or independently of the third lens unit.

Thus, a predetermined zoom ratio (zooming ratio of 3) can be easily secured while miniaturizing the entire lens system, and the angle of view at the wide-angle end at which the fluctuation of aberration due to zooming is small is 62 to 73 degrees. Zoom lens with high optical performance and wide angle of view.

In particular, the first lens unit has a negative refractive power, the effective beam diameter on the wide-angle side is reduced, and the widening of the angle of view is facilitated while reducing the size of the entire lens system.

On the wide-angle side, the first group having negative refractive power is set as a front group, and the second to fourth groups as a whole are rear groups with positive refractive power, and the front group (first group). And rear group (2nd
The distance between the group (fourth group) and the fourth group is widened so that the entire lens system becomes a retrofocus type.

Thus, a wide angle of view such as a photographic angle of view of about 62 to 73 degrees on the wide angle side is achieved while reducing the size of the entire lens system.

Further, on the telephoto side, the first and second units are collectively a front unit having a positive refractive power, and the third and fourth units are entirely a rear unit having a negative refractive power. The lens group and the rear lens group are located at a predetermined interval, so that the entire lens system is of a telephoto type.

In particular, both the third and fourth lens units have a negative refractive power, so that the negative refractive power of the entire rear lens unit becomes stronger and the entire lens system becomes a stronger telephoto lens. I have.

As a result, the back focus does not become too long, and the focal length on the telephoto side is effectively increased while shortening the overall length of the lens.

In the present embodiment, upon zooming from the wide-angle end to the telephoto end, the second lens unit moves toward the object side so as to reduce the distance from the first lens unit. The multiplier effect is always provided.

The third lens unit having a negative refractive power is moved to the object side so as to increase the distance between the second lens unit and the second lens unit at the time of zooming, so that the third lens unit and the fourth lens unit are formed to have a strong telephoto type on the telephoto side.

The fourth lens unit moves toward the object side so as to reduce the distance from the third lens unit, and moves away from the image point of the third lens unit on the image plane side of the fourth lens unit. The doubling effect is effectively performed.

In the present embodiment, zooming is effectively performed by moving the second to fourth units on the optical axis so as to satisfy the above-described conditions, thereby facilitating high zooming.

In the first to third numerical examples, the second and fourth lens units are arranged such that the distance D2 between the second and third lens units and the distance D3 between the third and fourth lens units become D2 + D3 = constant during zooming. Are moved together.

Thus, a predetermined zoom ratio can be effectively obtained while simplifying the lens barrel structure when moving each lens unit with zooming.

In Numerical Examples 7 and 8, the second lens unit has at least two cemented lens surfaces, and the fourth lens unit has at least one cemented lens surface.

In this manner, various aberrations, particularly spherical aberration and chromatic aberration, associated with zooming when the second and fourth units are moved much on the optical axis in order to secure a predetermined zooming ratio are satisfactorily corrected. are doing.

In particular, at the time of zooming from the wide-angle end to the telephoto end, at least two cemented lens surfaces are provided in the second lens unit in which on-axis rays pass through positions distant from the optical axis. Variations in aberrations and chromatic aberrations are well corrected.

The zoom lens according to the present invention satisfies the following conditions in order to reduce the size of the entire lens system and maintain good optical performance of the entire screen.

(2-1) The focal length of the i-th lens unit is fi,
When the focal length of the entire system at the wide-angle end is Fw, 0.5 <| f1 | / Fw <2.9 (1) f2 <| f1 |, | f3 |, | F4 |... (2) is to satisfy the following condition.

Conditional expression (1) relates to the refractive power of the first lens unit with respect to the focal length at the wide-angle end. If the refractive power of the first lens unit becomes too weak beyond the upper limit, the effective beam diameter of the first lens unit on the wide-angle side is reduced. Will increase. On the other hand, if the refractive power of the first lens unit becomes too strong beyond the lower limit, a large amount of negative distortion will occur on the wide-angle side, which is not good.

Conditional expression (2) appropriately sets the refractive powers of the first, third, and fourth groups with respect to the second group, so that the entire lens system becomes a retrofocus type at the wide-angle end and a telefocus at the telephoto end. This is to secure a predetermined zoom ratio while reducing the size of the entire lens system by making it a mold.

If conditional expression (2) is not satisfied, it becomes difficult to make the entire lens system a good retrofocus type on the wide-angle side and a good telephoto type on the telephoto side.

[0045] (2-2) When the zoom ratio caused by zooming of the i-th group was _{Z n Z 3 <Z 2 ········} (3) 1 ≦ Z 4 ···· ... (4) The following condition must be satisfied.

Conditional expression (3) defines the zoom ratio of the second and third lens groups with zooming, and conditional expression (4) defines the zooming ratio of the fourth lens group with zooming. .

Conditional expression (3) is equivalent to f2 <| f in conditional expression (2).
This is for effectively changing the magnification under the condition of 3 |. That is, it becomes difficult to increase the amount of movement of the second lens group as compared with the third lens group and to effectively obtain a predetermined zoom ratio.

Conditional expression (4) is designed so that the zoom ratio of the fourth lens unit is always 1 or more. If conditional expression (4) is not satisfied, the aberration fluctuation accompanying zooming increases, and This is not good because the amount of movement of each lens group increases.

(2-3) The third lens unit may be fixed with zooming, which is preferable because the lens barrel is simplified.

Next, numerical examples of the present invention will be described. In the numerical examples, Ri is the radius of curvature of the i-th lens surface in order from the object side, Di is the i-th lens thickness and air spacing from the object side, and Ni and νi are the i-th lens surfaces in order from the object side. The refractive index and Abbe number of glass.

Table 1 shows the relationship between the above-mentioned conditional expressions and various numerical values in the numerical examples.

<Numerical Example 1> f = 36.10 to 10.2 fNO = 1: 4.66 to 7.25 2 ω = 62.0 to 24.1 R 1 = -163.69 D 1 = 1.80 N 1 = 1.69680 ν 1 = 55.5 R 2 = 23.39 D 2 = 2.80 R 3 = 26.30 D 3 = 2.50 N 2 = 1.84666 ν 2 = 23.9 R 4 = 40.25 D 4 = Variable R 5 = 27.29 D 5 = 1.00 N 3 = 1.84666 ν 3 = 23.9 R 6 = 16.92 D 6 = 4.10 N 4 = 1.48749 ν 4 = 70.2 R 7 = -63.46 D 7 = 0.12 R 8 = 15.35 D 8 = 2.90 N 5 = 1.48749 ν 5 = 70.2 R 9 = 47.32 D 9 = Variable R10 = (Aperture) D 10 = 1.87 R11 = 51.59 D 11 = 5.21 N 6 = 1.62004 ν 6 = 36.3 R12 = -38.64 D 12 = 1.00 N 7 = 1.71300 ν 7 = 53.8 R 13 = 33.79 D 13 = Variable R14 = 155.87 D 14 = 2.39 N 8 = 1.48749 ν 8 = 70.2 R15 = -22.66 D 15 = 2.30 R16 = -10.66 D 16 = 1.20 N 9 = 1.60311 ν 9 = 60.7 R17 = -35.83

[0053]

[Table 1] <Numerical Example 2> f = 29.03 to 77.5 fNO = 1: 4.67 to 7.25 2ω = 73.4 to 31.2 R 1 = -244.89 D 1 = 1.80 N 1 = 1.69680 ν 1 = 55.5 R 2 = 20.38 D 2 = 3.21 R 3 = 24.66 D 3 = 2.50 N 2 = 1.84666 ν 2 = 23.9 R 4 = 37.43 D 4 = Variable R 5 = 24.07 D 5 = 1.00 N 3 = 1.84666 ν 3 = 23.9 R 6 = 16.65 D 6 = 3.50 N 4 = 1.51633 ν 4 = 64.2 R 7 = -27.53 D 7 = 1.00 N 5 = 1.84666 ν 5 = 23.9 R 8 = -38.96 D 8 = 0.12 R 9 = 16.75 D 9 = 2.00 N 6 = 1.48749 ν 6 = 70.2 R10 = 46.34 D 10 = Variable R11 = (Aperture) D 11 = 1.87 R12 = 40.74 D 12 = 2.50 N 7 = 1.60342 ν 7 = 38.0 R13 = -25.71 D 13 = 1.00 N 8 = 1.71300 ν 8 = 53.8 R14 = 34.19 D 14 = Variable R15 = -59.25 D 15 = 2.39 N 9 = 1.48749 ν 9 = 70.2 R16 = -22.76 D 16 = 3.25 R17 = -9.94 D 17 = 1.20 N10 = 1.60311 ν10 = 60.7 R18 = -20.89

[0054]

[Table 2] <Numerical Example 3> f = 39.30 to 16.29 fNO = 1: 4.66 to 7.74 2 ω = 57.67 to 23.01 R 1 = -161.98 D 1 = 1.80 N 1 = 1.69680 ν 1 = 55.5 R 2 = 23.16 D 2 = 3.11 R 3 = 26.32 D 3 = 2.50 N 2 = 1.84666 ν 2 = 23.9 R 4 = 39.72 D 4 = Variable R 5 = 27.45 D 5 = 1.00 N 3 = 1.84666 ν 3 = 23.9 R 6 = 17.26 D 6 = 4.10 N 4 = 1.48749 ν 4 = 70.2 R 7 = -69.23 D 7 = 0.12 R 8 = 15.25 D 8 = 2.90 N 5 = 1.48749 ν 5 = 70.2 R 9 = 46.64 D 9 = Variable R10 = (Aperture) D 10 = 1.87 R11 = 54.47 D 11 = 5.28 N 6 = 1.62004 ν 6 = 36.3 R12 = -46.76 D 12 = 1.00 N 7 = 1.71300 ν 7 = 53.8 R13 = 36.54 D 13 = Variable R14 = 164.46 D 14 = 2.46 N 8 = 1.48749 ν 8 = 70.2 R15 = -24.84 D 15 = 2.18 R16 = -10.66 D 16 = 1.20 N 9 = 1.60311 ν 9 = 60.7 R17 = -31.74

[0055]

[Table 3] <Numerical example 4> f = 36.00 to 101.0 fNO = 1: 4.66 to 7.25 2ω = 62.0 to 24.1 R 1 = -116.74 D 1 = 1.80 N 1 = 1.69680 ν 1 = 55.5 R 2 = 23.32 D 2 = 2.37 R 3 = 25.90 D 3 = 2.50 N 2 = 1.84666 ν 2 = 23.9 R 4 = 41.51 D 4 = Variable R 5 = 28.87 D 5 = 1.00 N 3 = 1.84666 ν 3 = 23.9 R 6 = 17.03 D 6 = 4.10 N 4 = 1.48749 ν 4 = 70.2 R 7 = -43.42 D 7 = 0.12 R 8 = 15.80 D 8 = 2.90 N 5 = 1.48749 ν 5 = 70.2 R 9 = 50.31 D 9 = Variable R10 = (Aperture) D 10 = 1.50 R11 = 55.01 D 11 = 4.00 N 6 = 1.62004 ν 6 = 36.3 R12 = -28.73 D 12 = 1.00 N 7 = 1.71300 ν 7 = 53.8 R13 = 30.98 D 13 = Variable R14 = -261.77 D 14 = 2.50 N 8 = 1.48749 ν 8 = 70.2 R15 = -19.46 D 15 = 3.95 R16 = -10.98 D 16 = 1.20 N 9 = 1.60311 ν 9 = 60.7 R17 = -31.40

[0056]

[Table 4] <Numerical example 5> f = 29.01 to 77.5 fNO = 1: 4.67 to 7.25 2 ω = 73.4 to 31.2 R 1 = -150.46 D 1 = 1.80 N 1 = 1.69680 ν 1 = 55.5 R 2 = 20.99 D 2 = 3.04 R 3 = 23.93 D 3 = 2.50 N 2 = 1.84666 ν 2 = 23.9 R 4 = 37.71 D 4 = Variable R 5 = 24.24 D 5 = 1.00 N 3 = 1.84666 ν 3 = 23.9 R 6 = 15.86 D 6 = 3.50 N 4 = 1.51633 ν 4 = 64.2 R 7 = -28.43 D 7 = 1.00 N 5 = 1.84666 ν 5 = 23.9 R 8 = -39.28 D 8 = 0.12 R 9 = 15.50 D 9 = 2.00 N 6 = 1.48749 ν 6 = 70.2 R10 = 43.98 D 10 = Variable R11 = (Aperture) D 11 = 2.00 R12 = 38.88 D 12 = 2.50 N 7 = 1.60342 ν 7 = 38.0 R13 = -23.57 D 13 = 1.00 N 8 = 1.71300 ν 8 = 53.8 R14 = 30.54 D 14 = Variable R15 = -42.83 D 15 = 2.39 N 9 = 1.48749 ν 9 = 70.2 R16 = -19.40 D 16 = 3.63 R17 = -9.58 D 17 = 1.20 N10 = 1.60311 ν10 = 60.7 R18 = -18.61

[0057]

[Table 5] <Numerical example 6> f = 39.30 to 106.3 fNO = 1: 4.66 to 7.74 2ω = 57.67 to 23.01 R 1 = -199.97 D 1 = 1.80 N 1 = 1.69680 ν 1 = 55.5 R 2 = 23.01 D 2 = 4.00 R 3 = 26.92 D 3 = 2.50 N 2 = 1.84666 ν 2 = 23.9 R 4 = 38.85 D 4 = Variable R 5 = 25.73 D 5 = 1.00 N 3 = 1.84666 ν 3 = 23.9 R 6 = 17.21 D 6 = 4.10 N 4 = 1.48749 ν 4 = 70.2 R 7 = -97.50 D 7 = 0.12 R 8 = 16.23 D 8 = 2.90 N 5 = 1.48749 ν 5 = 70.2 R 9 = 45.49 D 9 = Variable R10 = (Aperture) D 10 = 2.00 R11 = 45.67 D 11 = 5.00 N 6 = 1.60342 ν 6 = 38.0 R12 = -189.41 D 12 = 1.00 N 7 = 1.71300 ν 7 = 53.8 R13 = 36.20 D 13 = Variable R14 = 94.54 D 14 = 2.07 N 8 = 1.51633 ν 8 = 64.2 R15 = -35.28 D 15 = 2.20 R16 = -11.23 D 16 = 1.20 N 9 = 1.60311 ν 9 = 60.7 R17 = -32.10

[0058]

[Table 6] <Numerical example 7> f = 29.0 to 101.0 fNO = 1: 4.66 to 7.23 2 ω = 73.4 to 24.2 R 1 = -368.71 D 1 = 1.80 N 1 = 1.71300 ν 1 = 53.8 R 2 = 19.44 D 2 = 2.60 R 3 = 21.22 D 3 = 3.30 N 2 = 1.84666 ν 2 = 23.9 R 4 = 31.89 D 4 = Variable R 5 = 19.84 D 5 = 1.00 N 3 = 1.84666 ν 3 = 23.9 R 6 = 13.67 D 6 = 4.60 N 4 = 1.48749 ν 4 = 70.2 R 7 = -36.96 D 7 = 1.00 N 5 = 1.84666 ν 5 = 23.9 R 8 = -54.39 D 8 = 0.12 R 9 = 19.31 D 9 = 2.70 N 6 = 1.60311 ν 6 = 60.7 R10 = 86.07 D 10 = Variable R11 = (Aperture) D 11 = 1.50 R12 = 32.92 D 12 = 2.50 N 7 = 1.59551 ν 7 = 39.2 R13 = -24.43 D 13 = 1.00 N 8 = 1.69680 ν 8 = 55.5 R14 = 20.84 D 14 = Variable R15 = 115.92 D 15 = 1.00 N 9 = 1.69680 ν 9 = 55.5 R16 = 20.36 D 16 = 3.70 N10 = 1.53172 ν10 = 48.9 R17 = -53.35 D 17 = 4.10 R18 = -10.09 D 18 = 1.00 N11 = 1.71300 ν11 = 53.8 R19 = -15.35 D 19 = -16.62

[0059]

[Table 7] <Numerical example 8> f = 29.0 to 101.0 fNO = 1: 4.66 to 7.23 2ω = 73.4 to 24.2 R 1 = -486.49 D 1 = 1.80 N 1 = 1.71300 ν 1 = 53.8 R 2 = 19.54 D 2 = 3.01 R 3 = 21.62 D 3 = 3.30 N 2 = 1.84666 ν 2 = 23.9 R 4 = 31.83 D 4 = Variable R 5 = 19.73 D 5 = 1.00 N 3 = 1.84666 ν 3 = 23.9 R 6 = 13.69 D 6 = 4.50 N 4 = 1.48749 ν 4 = 70.2 R 7 = -86.88 D 7 = 0.12 R 8 = 20.43 D 8 = 2.80 N 5 = 1.60311 ν 5 = 60.7 R 9 = -339.24 D 9 = 1.00 N 6 = 1.84666 ν 6 = 23.9 R10 = 155.97 D 10 = Variable R11 = (Aperture) D 11 = 1.50 R12 = 32.71 D 12 = 2.50 N 7 = 1.59551 ν 7 = 39.2 R13 = -22.53 D 13 = 1.00 N 8 = 1.69680 ν 8 = 55.5 R14 = 20.89 D 14 = Variable R15 = 117.95 D 15 = 1.00 N 9 = 1.69680 ν 9 = 55.5 R16 = 20.78 D 16 = 3.70 N10 = 1.53172 ν10 = 48.9 R17 = -53.40 D 17 = 4.10 R18 = -10.19 D 18 = 1.00 N11 = 1.71300 ν11 = 53.8 R19 = -15.10 D 19 = -16.85

[0060]

[Table 8]

[0061]

As described above, according to the present invention, a lens unit having a negative refractive power is preceded by four lens units as a whole.
By appropriately setting the moving conditions of each lens unit and the refracting power of each lens unit during zooming, the zoom ratio including the wide angle of view region is high, and the zoom ratio is as high as about 3 and high over the entire zoom range. A compact zoom lens having optical performance and a short overall lens length can be achieved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a lens according to a numerical example 1 of the present invention.

FIG. 2 is a sectional view of a lens according to a numerical example 2 of the present invention.

FIG. 3 is a sectional view of a lens according to a numerical example 3 of the present invention.

FIG. 4 is a sectional view of a lens according to a numerical example 4 of the present invention.

FIG. 5 is a sectional view of a lens according to a numerical example 5 of the present invention.

FIG. 6 is a sectional view of a lens according to a sixth numerical example of the present invention;

FIG. 7 is a sectional view of a lens according to a numerical example 7 of the present invention.

FIG. 8 is a sectional view of a lens according to a numerical example 8 of the present invention.

FIG. 9 is an aberration diagram at a wide-angle end according to Numerical Embodiment 1 of the present invention.

FIG. 10 is an intermediate aberration diagram of the numerical example 1 of the present invention.

FIG. 11 is an aberration diagram at a telephoto end in Numerical Example 1 of the present invention;

FIG. 12 is an aberration diagram at a wide angle end according to Numerical Example 2 of the present invention.

FIG. 13 is an intermediate aberration diagram of the numerical example 2 of the present invention.

FIG. 14 is an aberration diagram at a telephoto end in Numerical Example 2 of the present invention;

FIG. 15 is an aberration diagram at a wide angle end according to Numerical Example 3 of the present invention.

FIG. 16 is an intermediate aberration diagram of the numerical example 3 of the present invention.

FIG. 17 is an aberration diagram at a telephoto end in Numerical Example 3 of the present invention.

FIG. 18 is an aberration diagram at a wide angle end according to Numerical Example 4 of the present invention.

FIG. 19 is an intermediate aberration diagram of the numerical example 4 of the present invention.

FIG. 20 is an aberration diagram at a telephoto end in Numerical Example 4 of the present invention.

FIG. 21 is an aberration diagram at a wide angle end according to Numerical Example 5 of the present invention.

FIG. 22 is an intermediate aberration diagram of the numerical example 5 of the present invention.

FIG. 23 is an aberration diagram at a telephoto end in Numerical Example 5 of the present invention.

FIG. 24 is an aberration diagram at a wide angle end according to Numerical Example 6 of the present invention.

FIG. 25 is an intermediate aberration diagram of the numerical example 6 of the present invention.

FIG. 26 is an aberration diagram at a telephoto end in Numerical Example 6 of the present invention.

FIG. 27 is an aberration diagram at a wide angle end according to Numerical Example 7 of the present invention.

FIG. 28 is an intermediate aberration diagram of the numerical example 7 of the present invention.

FIG. 29 is an aberration diagram at a telephoto end in Numerical Example 7 of the present invention;

FIG. 30 is an aberration diagram at a wide angle end according to Numerical Example 8 of the present invention.

FIG. 31 is an intermediate aberration diagram of the numerical example 8 of the present invention.

FIG. 32 is an aberration diagram at a telephoto end in Numerical Example 8 of the present invention;

[Explanation of symbols]

 L1 First group L2 Second group L3 Third group L4 Fourth group SP stop S Sagittal image plane M Meridional image plane d d-line g g-line

Claims (6)

(57) [Claims] 1. A first lens unit having a negative refractive power, a second lens unit having a positive refractive power, a third lens unit having a negative refractive power, and a fourth lens unit having a negative refractive power in order from the object side. During zooming from the wide-angle end to the telephoto end, the distance between the first and second groups decreases, the distance between the second and third groups increases, and A zoom lens in which each lens group is moved so as to decrease the distance from the fourth group , wherein the focal length of the i-th group is f
i, satisfying a condition of 0.5 <| f1 | / Fw <2.9 f2 <| f1 |, | f3 |, | f4 |, where Fw is the focal length of the entire system at the wide-angle end. Zoom lens. 2. The zoom ratio according to the zooming of the i-th lens unit is Zn
_2. The zoom lens according to claim 1 , wherein the following condition is satisfied: Z ₃ <Z 21 ≦ Z ₄ . 3. Four lens groups of a first group having a negative refractive power, a second group having a positive refractive power, a third group having a negative refractive power, and a fourth group having a negative refractive power in order from the object side. In zooming from the wide-angle end to the telephoto end, the distance between the first and second units decreases, the distance between the second and third units increases, and A zoom lens in which each lens group is moved so as to decrease the distance from the fourth lens group, and D2 + D3 = constant when the distance between the i-th lens group and the (i + 1) -th lens lens is Di ; Let f be the focal length of the group
i, satisfying a condition of 0.5 <| f1 | / Fw <2.9 f2 <| f1 |, | f3 |, | f4 |, where Fw is the focal length of the entire system at the wide-angle end. Zoom lens. 4. The zoom ratio according to the zooming of the i-th lens unit is Zn
And then Z ₃ <zoom lens according to claim 3, characterized by satisfying the Z ₂ 1 ≦ Z ₄ following condition when the. 5. Four lens groups of a first group having a negative refractive power, a second group having a positive refractive power, a third group having a negative refractive power, and a fourth group having a negative refractive power in order from the object side. In zooming from the wide-angle end to the telephoto end, the distance between the first and second units decreases, the distance between the second and third units increases, and Each lens group is moved so that the distance from the fourth group is reduced, and the second group has at least two cemented lens surfaces;
Figure fourth group has at least one cemented lens surface
Wherein the focal length of the i-th lens unit is fi
A zoom lens characterized by satisfying a condition of 0.5 <| f1 | / Fw <2.9 f2 <| f1 |, | f3 |, | f4 | when the focal length of the entire system at the end is Fw. . 6. The zoom ratio according to the zooming of the i-th lens unit is Zn
And then Z ₃ <zoom lens according to claim 5, characterized by satisfying the Z ₂ 1 ≦ Z ₄ following condition when the.