JP3315671B2 - 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 suitable for a single-lens reflex camera, a video camera, and the like, and more particularly, a so-called negative lead type lens, which is preceded by a lens group having a negative refractive power. The present invention relates to a large-aperture zoom lens having a wide angle of view and a high zoom ratio.

[0002]

2. Description of the Related Art A negative lead type zoom lens, which is preceded by a lens group having a negative refractive power, has features such as a relatively wide angle of view and a short close-up distance. However, there are drawbacks such as an increase in the aperture diameter and difficulty in increasing the zoom ratio.

[0003] A zoom lens which has improved these drawbacks and has achieved miniaturization and high zoom ratio of the whole lens system is disclosed in, for example, JP-B-49-23912, JP-A-53-34539, and JP-A-57-34539. 163213, JP-A-58-4
No. 113, JP-A-63-241511, and JP-A-2-201310.

In each of these publications, a zoom lens is composed of four lens groups as a whole in order from the object side, that is, a lens group having negative, positive, negative, and positive refractive power, and a predetermined lens group is appropriately moved. Let me change the magnification.

[0005]

In recent years, as a standard zoom lens used for a single-lens reflex camera, a video camera, or the like, a zoom lens having a wide angle of view and a high zoom ratio has been demanded. For example, a single-lens reflex camera for 35 mm film already has a focal length of 35 mm to 70 mm or a focal length of 28 mm to 7 mm.
A zoom lens having a wide angle of view of about 0 mm is used as a standard zoom lens.

[0006] More recently, the focal length is 28 mm to 80 m.
There is a demand for a standard zoom lens having a large aperture ratio, which enlarges the zooming range to the telephoto side with a focal length of about 28 mm to 85 mm and achieves high zooming.

However, in general, when the photographing angle of view is as large as this and the zoom ratio is high, the entire length of the lens becomes long, and in zooming, a complicated zoom movement is required. There is a problem that the lens barrel becomes large and complicated.

According to the present invention, the zoom lens is composed of four lens groups as a whole, and the refracting power of each lens group and the moving conditions of each lens group for zooming are appropriately set.
The objective is to provide a zoom lens that has a relatively wide angle of view and high optical performance over the entire zoom range with a high zoom ratio, while reducing the overall length of the lens and preventing the lens barrel from becoming large and complicated. .

In particular, the present invention is a full zoom lens having an F-number of 2.8, a large aperture ratio, a wide angle of view of 80 ° or more at the wide angle end, and a high zoom ratio of about 3 at a zoom ratio. It is intended to provide a zoom lens having high optical performance over a range.

[0010]

According to a first aspect of the present invention, there is provided a zoom lens having 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. And a fourth lens unit having a positive refractive power and a fourth lens unit, wherein zooming is performed by changing the air spacing of each lens unit.
The group includes a meniscus negative 21st surface with the convex surface facing the object side.
A cemented lens in which a lens and a positive twenty-second lens having both lens surfaces joined together, and a positive twenty-third lens with a strong positive refraction surface facing the object side, and the twenty-first lens or The object-side surface of the twenty-third lens is an aspheric surface, the radius of curvature of the cemented lens surface of the cemented lens is R2,2, the lens outer diameter of the twenty-third lens is DE, the focal length of the second group is F2, The aspheric shape of the aspheric surface is such that the X axis is in the optical axis direction, the H axis is perpendicular to the optical axis, the traveling direction of light is positive, the paraxial radius of curvature is R, and the aspheric coefficients are A, B, C, D, As E,

(Equation 3) 0.6 <R2, 2 / F2 <1.0 (1a) B <0 (1b) B + C × (DE / 2) ² <0 (1c) It is characterized by satisfying certain conditions.

According to a fourth aspect of the present invention, in the zoom lens, a first unit having a negative refractive power, a second unit having a positive refractive power,
A zoom lens having four lens groups, a third lens group having a negative refractive power and a fourth lens group having a positive refractive power, and performing zooming by changing an air interval between the lens groups, wherein Is a cemented lens in which a negative meniscus twenty-first lens with a convex surface facing the object side and a positive twenty-second lens with both lens surfaces convex, and a positive lens with a strong positive refractive surface facing the object side. 23rd
A lens having an aspherical surface on the image side of the twenty-second lens, a radius of curvature of a cemented lens surface of the cemented lens being R2,2, a lens outer diameter of the twenty-third lens being DE, 2
The focal length of the group is F2, the aspheric shape of the aspheric surface is the X axis in the optical axis direction, the H axis is perpendicular to the optical axis, the traveling direction of the light is positive, the paraxial radius of curvature is R, the aspheric coefficient is A, B, C, D, and E

(Equation 4) It is characterized by satisfying the following condition: 0.6 <R2,2 / F2 <1.0 B> 0 B + C × (DE / 2) ² > 0

[0012]

1 to 4 are sectional views of numerical examples 1 to 4 of the present invention, respectively. FIGS. 5 and 6 are lens cross-sectional views of Numerical Examples 5 and 6, which are reference to the present invention. In the lens sectional view, L1 is the first negative refractive power.
L2 is a second group having a positive refractive power, L3 is a third group having a negative refractive power, L4 is a fourth group having a positive refractive power, and SP is a stop.

In the present invention, zooming is performed by moving a predetermined lens group so that the air gap between the lens groups changes.

In particular, when changing the magnification from the wide-angle end to the telephoto end, the air gap between the first and second groups is reduced, the air gap between the second and third groups is increased, and the third and fourth groups are changed. At least the first, second, and fourth groups are moved so that the air gap between the groups is reduced. Specifically, zooming from the wide-angle end to the telephoto end is performed by moving the first unit to the image plane side, moving the second unit to the object side, and moving the fourth unit to the object side.

At this time, the second lens unit and the fourth lens unit may be independently moved to the object side, or may be integrally moved to simplify the lens barrel. Focusing is performed by moving the entire first group, and the first group is divided into two lens groups, a 11th group and a twelfth group, from the object side, and the twelfth group is moved. .

Next, the features of the numerical embodiments shown in FIGS. 1 to 4 will be described in order.

(1-1) In numerical embodiments 1 and 2 shown in FIGS. 1 and 2, zooming is performed by changing the air spacing of each lens unit, and the second unit is a meniscus having a convex surface facing the object side. A cemented lens in which a negative twenty-first lens having a convex shape and a positive twenty-second lens whose both lens surfaces are convex, and a positive twenty-third lens having a strong positive refractive surface facing the object side, The second
The radius of curvature of the cemented lens surface of the cemented lens having the aspherical surface on the object side of the first lens or the twenty-third lens is R
If the aspherical shape of 2, 2, aspherical surface is also expressed by the above equation
When the aspheric coefficients of the aspheric surface are B and C, the lens outer diameter of the 23rd lens is DE, and the focal length of the second group is F2, 0.6 <R2, 2 / F2 <1.0. {(1-a) B <0} (1-b) B + C × (DE / 2) ² <0 ‥‥‥ (1-c) As a result, various aberrations associated with zooming are favorably corrected while shortening the overall length of the lens, and high optical performance is obtained over the entire zoom range.

In this embodiment, a divergent light beam enters the second group from the first group having a negative refractive power. For this reason, when the F number is increased, a light beam is incident at a high position from the optical axis of the second lens unit. As a result, a remarkably large aberration occurs in the peripheral portion of the second lens unit, and the optical performance is reduced.

On the other hand, there are methods of increasing the number of lenses in the second group and weakening the refractive power of the second group. However, these methods are not preferable because the overall length of the lens becomes longer and the outer diameter of the first lens unit increases.

Therefore, in the present embodiment, various aberrations, particularly spherical aberration and coma, which frequently occur in the second lens unit are determined by the above-mentioned conditional expression (1-1).
a), the three lenses satisfying (1-b) and (1-c) and the aspherical surface are satisfactorily corrected to obtain high optical performance.

Conditional expression (1-a) is mainly for correcting coma. If the lower limit of conditional expression (1-a) is exceeded, coma will be over-corrected. If the upper limit is exceeded, the remaining coma will be corrected by another lens surface, and good with spherical aberration and astigmatism. It becomes difficult to correct for Furthermore, it becomes difficult to correct various aberrations of the entire system in a well-balanced manner.

The conditional expressions (1-b) and (1-c) are for appropriately setting the aspherical shape, and in particular for favorably correcting spherical aberration and coma. Conditional expression (1-b) is
Represents the next-order aberration component, which is negative, that is, has an action of weakening the positive refractive power in the peripheral portion, and makes the spherical aberration and the coma aberration excessively corrected. Aberration and coma are well corrected.

Conditional expression (1-c) appropriately determines the aspherical shape including the fifth-order aberration component, and in particular, the amount of the aspherical surface at the position of the lens outer diameter DE is a direction in which the refractive power is weakened in the peripheral portion. I have to. This reduces the occurrence of various aberrations while giving the second group a relatively strong positive refractive power. This also allows the first lens unit to have a strong negative refractive power, thereby shortening the overall length of the lens.

In this embodiment, the first unit has a positive lens and at least two negative lenses.
As a result, mainly astigmatism and distortion are favorably corrected.

The first lens unit includes an eleventh lens unit and a twelfth lens unit in order from the object side.
It has two lens groups, and the twelfth group is moved on the optical axis for focusing. Thus, even when focusing is performed, the entire length of the lens is kept constant, the lens is prevented from protruding to the outside, and the relatively lightweight and small twelfth lens group is moved, for example, when performing automatic focusing. Drive control is easy.

(1-2) In the numerical examples 3 and 4 shown in FIGS. 3 and 4, zooming is performed by changing the air spacing of each lens unit, and the second unit is a meniscus having a convex surface facing the object side. A cemented lens in which a negative twenty-first lens having a convex shape and a positive twenty-second lens whose both lens surfaces are convex, and a positive twenty-third lens having a strong positive refractive surface facing the object side, The second
The image side surface of the two lenses is an aspheric surface, the radius of curvature of the cemented lens surface of the cemented lens is R2,2, and the aspheric surface is an aspheric surface
When the shape is expressed by the above equation, when the aspheric coefficients of the aspheric surface are B and C, the lens outer diameter of the 23rd lens is DE, and the focal length of the second group is F2, 0.6 <R2. 2 / F2 <1.0 ‥‥‥ (2-a) B> 0 ‥‥‥ (2-b) B + C × (DE / 2) ² > 0 ‥‥‥ (2-c) I have to. As a result, as in Numerical Examples 1 and 2 described above, while reducing the overall length of the lens, various aberrations associated with zooming are satisfactorily corrected, and high optical performance is obtained over the entire zoom range.

In this embodiment, a divergent light beam from the first group having negative refractive power enters the second group. Therefore, when the F-number is increased, a light beam enters a position higher than the optical axis of the second lens unit. As a result, a remarkably large aberration occurs in the periphery of the second lens unit, and the optical performance is reduced.

On the other hand, there are methods of increasing the number of lenses in the second group and weakening the refractive power of the second group. However, these methods are not preferable because the overall length of the lens becomes longer and the outer diameter of the first lens unit increases.

Therefore, in the present embodiment, various aberrations, particularly spherical aberration and coma, which frequently occur in the second lens unit are corrected by the conditional expression (2-
a), three lenses satisfying (2-b) and (2-c) and an aspheric surface are satisfactorily corrected to obtain high optical performance.

Conditional expression (2-a) is mainly for correcting coma. If the lower limit of conditional expression (2-a) is exceeded, coma will be over-corrected. If the upper limit is exceeded, the remaining coma will be corrected by another lens surface, and good with spherical aberration and astigmatism. It becomes difficult to correct for Furthermore, it becomes difficult to correct various aberrations of the entire system in a well-balanced manner.

The conditional expressions (2-b) and (2-c) are for appropriately setting the aspherical shape, and particularly for favorably correcting spherical aberration and coma. Of these, conditional expression (2-b) is 3
Represents the next-order aberration component, which is negative, that is, has an action of weakening the positive refractive power at the peripheral portion, and makes the spherical aberration and the coma aberration excessively corrected. Aberration and coma are well corrected.

Conditional expression (2-c) appropriately determines the aspherical shape including the fifth-order aberration component, and in particular, the amount of the aspherical surface at the position of the lens outer diameter DE is such that the refractive power is weakened in the peripheral portion. I have to. This reduces the occurrence of various aberrations while giving the second group a relatively strong positive refractive power. This also allows the first lens unit to have a strong negative refractive power, thereby shortening the overall length of the lens.

In addition, in the present embodiment, the first unit has a positive lens and at least two negative lenses, as in the first and second numerical embodiments. As a result, mainly astigmatism and distortion are favorably corrected.

The first unit has, in order from the object, two lens units, an eleventh unit and a twelfth unit. The twelfth unit is moved on the optical axis to perform focusing. As a result, even when focusing is performed, the entire length of the lens is kept constant, the lens is prevented from protruding to the outside, and the relatively light and small first lens is used.
By moving the two lens groups, for example, drive control when performing automatic focusing is facilitated.

Next, Numerical Examples 5 and 6, which are reference to the present invention, will be described.

(1-3) In the numerical examples 5 and 6 shown in FIGS. 5 and 6, zooming from the wide-angle end to the telephoto end is performed by reducing the air gap between the first and second units. This is performed by increasing the air gap between the second group and the third group and decreasing the air gap between the third group and the fourth group. The fourth group is composed of at least one negative lens and at least one positive lens. The lens has at least one aspherical surface, the refractive power of the aspherical surface is φ4a, the radius of curvature formed by the intersection of the optical axis and the aspherical surface and the maximum radius position of the aspherical surface is Rmax, and the optical axis and the aspherical surface are Where RH is the radius of curvature formed by the intersection of the two and the aspherical position at height H from the optical axis (| Rmax |-| RH |) .phi.4a <0}
The condition (3-a) is satisfied. As a result, high optical performance is secured over the entire zoom range while achieving a high zoom ratio and a large aperture ratio.

In this embodiment, the first lens unit has a negative refractive power, has a lens structure advantageous for widening the angle of view, and has a variable power in the third lens unit and the fourth lens unit in addition to the first lens unit and the second lens unit. , Thereby facilitating a high zoom ratio.

In general, it is necessary to increase the refractive power of each lens unit in order to reduce the size of the entire lens system while increasing the zoom ratio and increasing the aperture ratio. As a result, the occurrence of aberration increases, and it is necessary to increase the number of lenses and correct the aberration.

Therefore, in this embodiment, the lens arrangement of the fourth group is appropriately set as described above, and various aberrations such as spherical aberration and astigmatism are favorably corrected with a small number of lenses by using an aspheric surface in particular. ing.

Conditional expression (3-a) is to mainly reduce spherical aberration and astigmatism by making the aspherical shape used in the fourth lens unit weaker as the positive refracting power moves away from the center of the optical axis. Corrected well. If conditional expression (3-a) is not satisfied, spherical aberration and astigmatism will increase. To correct them, the number of lenses in the fourth unit must be increased. As a result, the overall length of the lens becomes longer. Absent.

In this embodiment, the first unit has a positive lens and at least two negative lenses.
As a result, the focal length on the wide-angle side is shortened, the angle of view is widened, and the outer diameter of the first lens unit is reduced. Also, astigmatism and distortion are well corrected.

The second lens unit includes a negative meniscus twenty-first lens having a convex surface facing the object side and a positive twenty-second lens having both convex lens surfaces.
A cemented lens cemented with the lens and a positive twenty-third lens with a strong positive refractive surface facing the object side, and the radius of curvature of the cemented lens surface of the cemented lens is R
When the focal length of the second lens unit is F2, the following condition is satisfied: 0.6 <R2,2 / F2 <1.0 ‥‥‥ (3-b)

In this embodiment, since the first lens unit has a negative refractive power, the axial light beam incident on the second lens unit is incident on a position higher on the optical axis than the first lens unit. For this reason, various aberrations are likely to occur. Therefore, the second lens unit is configured as described above, and various aberrations are satisfactorily corrected.

Conditional expression (3-b) is intended to appropriately set the radius of curvature of the cemented lens surface of the cemented lens and to satisfactorily correct coma mainly. When the radius of curvature R2,2 is smaller than the lower limit of conditional expression (3-b), the coma aberration is over-corrected. On the contrary, when the radius of curvature R2,2 is larger than the upper limit, the remaining coma aberration is reduced. It becomes difficult to correct on the lens surface.

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.

The aspheric surface has an X-axis in the optical axis direction, an H-axis in a direction perpendicular to the optical axis, a positive traveling direction of light, R is a paraxial radius of curvature,
When A, B, C, D, and E are each aspheric coefficients

[0047]

(Equation 1)

This is represented by the following equation. Numerical Example 1 F = 28.8 to 77.49 FNO = 1: 2.8 2ω = 73.8 ° to 31.2 ° R 1 = 90.266 D 1 = 2.00 N 1 = 1.77250 ν 1 = 49.6 R 2 = 38.296 D 2 = 9.00 R 3 = -461.888 D 3 = 4.50 N 2 = 1.69895 ν 2 = 30.1 R 4 = -96.235 D 4 = 0.12 R 5 = -179.098 D 5 = 1.80 N 3 = 1.77250 ν 3 = 49.6 R 6 = 59.711 D 6 = 1.70 R 7 = 39.696 D 7 = 2.90 N 4 = 1.84666 ν 4 = 23.9 R 8 = 48.254 D 8 = Variable R 9 = 61.886 D 9 = 1.50 N 5 = 1.84666 ν 5 = 23.8 R10 = 36.536 D10 = 7.00 N 6 = 1.71300 ν 6 = 53.8 R11 = -92.015 D11 = 0.10 R12 = 43.139 Aspheric surface D12 = 5.50 N 7 = 1.77250 ν 7 = 49.6 R13 = -469.393 D13 = 1.50 N 8 = 1.84666 ν 8 = 23.8 R14 = 129.333 D14 = Variable R15 = (Aperture) D15 = 1.00 R16 = 805.385 D16 = 4.10 N 9 = 1.84666 ν 9 = 23.8 R17 = -23.912 D17 = 1.10 N10 = 1.77250 ν10 = 49.6 R18 = 56.787 D18 = 2.80 R19 = -32.304 D19 = 1.10 N11 = 1.83481 ν11 = 42.7 R20 = -279.112 D20 = Variable R21 = -61.974 D21 = 1.20 N12 = 1.84666 ν12 = 23.8 R22 = 82.543 D22 = 3.80 N13 = 1.71300 ν13 = 53.8 R23 = -34.909 D23 = 0.10 R24 = 49.546 D24 = 1.80 N14 = 1.76182 ν14 = 26.5 R25 = 39.572 D25 = 3.50 R26 = -706.308 D26 = 2.80 N15 = 1.69680 ν15 = 55.5 R27 = -64.519 D27 = 0.10 R28 = 77.104 D28 = 4.80 N16 = 1.71300 ν16 = 53.8 R29 = -104.361 D29 = 1.40 N17 = 1.84666 ν10 = 23.8 R30 = -193.661

[0049]

[Table 1]

R12: Aspherical surface coefficient A = 0 B = −1.67796 × 10 ⁻⁷ C = −1.68935 × 10 ⁻⁹ D = −1.43301 × 10 ⁻¹² Numerical Example 2 F = 28.8 to 77.63 FNO = 1: 2.82Ω = 73.8 ° -31.1 ° R 1 = 107.701 Aspherical surface D 1 = 2.20 N 1 = 1.83481 ν 1 = 42.7 R 2 = 43.329 D 2 = 16.00 R 3 = -663.644 D 3 = 2.00 N 2 = 1.83481 ν 2 = 42.7 R 4 = 35.965 D 4 = 5.00 N 3 = 1.84666 ν 3 = 23.8 R 5 = 96.556 D 5 = 1.50 R 6 = 56.255 D 6 = 2.50 N 4 = 1.84666 ν 4 = 23.8 R 7 = 62.609 D 7 = Variable R 8 = 78.988 Aspheric D 8 = 1.50 N 5 = 1.84666 ν 5 = 23.8 R 9 = 39.104 D 9 = 7.50 N 6 = 1.71300 ν 6 = 53.8 R10 = -85.722 D10 = 0.10 R11 = 41.699 D11 = 7.00 N 7 = 1.77250 ν 7 = 49.6 R12 = -136.277 D12 = 1.50 N 8 = 1.84666 ν 8 = 23.8 R13 = 183.298 D13 = Variable R14 = (Aperture) D14 = 1.00 R15 = 413.138 D15 = 4.10 N 9 = 1.84666 ν 9 = 23.8 R16 = -27.684 D16 = 1.10 N10 = 1.77250 ν10 = 49.6 R17 = 53.170 D17 = 2.80 R18 = -32.983 D18 = 1.10 N11 = 1.83481 ν11 = 42.7 R19 = -4847.456 D19 = Variable R20 = -80.792 D20 = 1.20 N12 = 1.84666 ν12 = 23.8 R21 =- 461.613 D21 = 3.50 N13 = 1.71300 ν13 = 53.8 R2 2 = -36.396 D22 = 0.10 R23 = 45.586 D23 = 1.80 N14 = 1.76182 ν14 = 26.5 R24 = 37.053 D24 = 3.50 R25 = -159.162 D25 = 2.50 N15 = 1.69680 ν15 = 55.5 R26 = -56.467 D26 = 0.10 R27 = 95.167 D27 = 5.00 N16 = 1.71300 ν16 = 53.8 R28 = -47.606 D28 = 1.40 N17 = 1.84666 ν17 = 23.8 R29 = -121.554

[0051]

[Table 2]

R1: Aspherical surface coefficient A = 0 B = 7.15543 × 10 ⁻⁷ C = −2.445904 × 10 ⁻¹⁰ D = −1.41751 × 10 ⁻¹³ R8: Aspherical surface coefficient A = 0 B = 3.12771 × 10 ⁻⁷ C = 9.59892 × 10 ^-11 Numerical example 3 F = 28.8 to 77.43 FNO = 1: 2.8 2ω = 73.8 ° to 31.2 ° R 1 = 72.775 D 1 = 2.00 N 1 = 1.77250 ν 1 = 49.6 R 2 = 37.706 D 2 = 9.00 R 3 = -474.784 D 3 = 4.50 N 2 = 1.69895 ν 2 = 30.1 R 4 = -94.031 D 4 = 0.12 R 5 = -151.662 D 5 = 1.80 N 3 = 1.77250 ν 3 = 49.6 R 6 = 60.031 D 6 = 1.70 R 7 = 40.187 D 7 = 2.90 N 4 = 1.84666 ν 4 = 23.9 R 8 = 46.071 D 8 = Variable R 9 = 77.426 D 9 = 1.50 N 5 = 1.84666 ν 5 = 23.8 R10 = 35.026 D10 = 7.00 N 6 = 1.71300 ν 6 = 53.8 R11 = -89.434 Aspherical surface D11 = 0.10 R12 = 39.339 D12 = 5.50 N 7 = 1.77250 ν 7 = 49.6 R13 = 244.065 D13 = 1.50 N 8 = 1.84666 ν 8 = 23.8 R14 = 139.168 D14 = Variable R15 = (Aperture) D15 = 1.00 R16 = 289.330 D16 = 4.10 N 9 = 1.84666 ν 9 = 23.8 R17 = -24.625 D17 = 1.10 N10 = 1.77250 ν10 = 49.6 R18 = 54.408 D18 = 2.80 R19 = -31.708 D19 = 1.10 N11 = 1.83481 ν11 = 42.7 R20 = -632.173 D20 = Variable R21 =- 58.935 D21 = 1.20 N12 = 1.84666 ν12 = 23.8 R22 = 83.573 D22 = 3.80 N13 = 1.71300 ν13 = 53.8 R23 = -33.512 D23 = 0.10 R24 = 48.387 D24 = 1.80 N14 = 1.76182 ν14 = 26.5 R25 = 39.391 D25 = 3.50 R26 = 263.616 D26 = 2.80 N15 = 1.69680 ν15 = 55.5 R27 = -73.712 D27 = 0.10 R28 = 79.107 D28 = 4.80 N16 = 1.71300 ν16 = 53.8 R29 = -103.977 D29 = 1.40 N17 = 1.84666 ν17 = 23.8 R30 = -302.891

[0053]

[Table 3]

R11: Aspherical coefficient A = 0 B = −3.75089 × 10 ⁻⁷ C = 2.89669 × 10 ⁻¹⁰ D = 6.62424 × 10 ⁻¹³ Numerical Example 4 F = 28.8 to 77.4 FNO = 1: 2.8 2ω = 73.8 ° ~ 31.2 ° R 1 = 112.318 Aspherical surface D 1 = 2.20 N 1 = 1.83481 ν 1 = 42.7 R 2 = 43.560 D 2 = 16.00 R 3 = -1512.328 D 3 = 2.00 N 2 = 1.83481 ν 2 = 42.7 R 4 = 35.617 D 4 = 5.00 N 3 = 1.84666 ν 3 = 23.8 R 5 = 88.280 D 5 = 1.50 R 6 = 53.563 D 6 = 2.50 N 4 = 1.84666 ν 4 = 23.8 R 7 = 60.304 D 7 = Variable R 8 = 79.550 D 8 = 1.50 N 5 = 1.84666 ν 5 = 23.8 R 9 = 39.269 D 9 = 7.50 N 6 = 1.71300 ν 6 = 53.8 R10 = -88.346 D10 = 0.10 R11 = 41.335 D11 = 7.00 N 7 = 1.77250 ν 7 = 49.6 R12 = -147.232 D12 = 1.50 N 8 = 1.84666 ν 8 = 23.8 R13 = 188.635 Aspherical surface D13 = Variable R14 = (Aperture) D14 = 1.00 R15 = 662.981 D15 = 4.10 N 9 = 1.84666 ν 9 = 23.8 R16 = -26.757 D16 = 1.10 N10 = 1.77250 ν10 = 49.6 R17 = 55.441 D17 = 2.80 R18 = -33.069 D18 = 1.10 N11 = 1.83481 ν11 = 42.7 R19 = -7905.451 D19 = Variable R20 = -83.147 D20 = 1.20 N12 = 1.84666 ν12 = 23.8 R21 = 833.745 D21 = 3.50 N13 = 1.71300 ν13 = 53.8 R22 = -36.241 D22 = 0.10 R23 = 45.804 D23 = 1.80 N14 = 1.76182 ν14 = 26.5 R24 = 37.229 D24 = 3.50 R25 = -182.280 D25 = 2.50 N15 = 1.69680 ν15 = 55.5 R26 = -57.812 D26 = 0.10 R27 = 87.431 D27 = 5.00 N16 = 1.71300 ν16 = 53.8 R28 = -56.322 D28 = 1.40 N17 = 1.84666 ν17 = 23.8 R29 = -149.333

[0055]

[Table 4]

R1: Aspherical surface coefficient A = 0 B = 5.77891 × 10 ⁻⁷ C = −4.6210 × 10 ⁻¹¹ D = 1.60066 × 10 ⁻¹⁴ R13: Aspherical surface coefficient A = 0 B = 3.56175 × 10 ⁻⁷ C = -1.61754 × 10 ^-11 D = 1.481666 × 10 ^-13 Numerical example 5 F = 28.8 to 77.46 FNO = 1: 2.8 2ω = 73.8 ° to 31.2 ° R 1 = 75.223 Aspherical surface D 1 = 2.20 N 1 = 1.83481 ν 1 = 42.7 R 2 = 37.278 D 2 = 16.00 R 3 = -1600.958 D 3 = 2.00 N 2 = 1.83481 ν 2 = 42.7 R 4 = 32.493 D 4 = 5.50 N 3 = 1.84666 ν 3 = 23.8 R 5 = 71.677 D 5 = 1.50 R 6 = 50.112 D 6 = 3.00 N 4 = 1.84666 ν 4 = 23.8 R 7 = 61.032 D 7 = Variable R 8 = 74.083 D 8 = 1.50 N 5 = 1.84666 ν 5 = 23.8 R 9 = 32.486 D 9 = 7.50 N 6 = 1.71300 ν 6 = 53.8 R10 = -289.769 D10 = 0.10 R11 = 76.844 D11 = 5.50 N 7 = 1.77250 ν 7 = 49.6 R12 = -151.673 D12 = 1.40 N 8 = 1.84666 ν 8 = 23.8 R13 = 340.344 D13 = 0.10 R14 = 54.698 D14 = 4.50 N 9 = 1.77250 ν 9 = 49.6 R15 = 1076.398 D15 = Variable R16 = (Aperture) D16 = 1.00 R17 = 179.919 D17 = 4.10 N10 = 1.84666 ν10 = 23.8 R18 = -29.320 D18 = 1.10 N11 = 1.77250 ν11 = 49.6 R19 = 55.441 D19 = 2.90 R20 = -32.601 D20 = 1.10 N12 = 1.83481 ν12 = 42.7 R21 = 199.184 D21 = Variable R22 = -146.326 D22 = 1.40 N13 = 1.84666 ν13 = 23.8 R23 = -238.520 D23 = 3.80 N14 = 1.71300 ν14 = 53.8 R24 = -31.546 D24 = 0.10 R25 = -92.279 D25 = 2.80 N15 = 1.69680 ν15 = 55.5 R26 = -56.757 D26 = 0.10 R27 = 125.405 Aspheric surface D27 = 5.00 N16 = 1.71300 ν16 = 53.8 R28 = -38.566 D28 = 1.40 N17 = 1.84666 ν17 = 23.8 R29 = -373.726

[0057]

[Table 5]

R1: Aspherical surface coefficient A = 0 B = 3.778122 × 10 ^-7 C = 2.31162 × 10 ^-10 D = -7.07093 × 10 ^-14 R27: Aspherical surface coefficient A = 0 B = -1.9333 × 10 ^-6 C = −4.86862 × 10 ⁻⁹ D = 3.0832 × 10 ⁻¹² Numerical Example 6 F = 28.8 to 77.35 FNO = 1: 2.8 2ω = 73.8 ° to 31.2 ° R 1 = 82.212 Aspherical surface D 1 = 2.20 N 1 = 1.83481 ν 1 = 42.7 R 2 = 40.145 D 2 = 16.00 R 3 = -734.079 D 3 = 2.00 N 2 = 1.83481 ν 2 = 42.7 R 4 = 32.424 D 4 = 5.50 N 3 = 1.84666 ν 3 = 23.8 R 5 = 65.788 D 5 = 1.50 R 6 = 49.287 D 6 = 3.00 N 4 = 1.84666 ν 4 = 23.8 R 7 = 61.693 D 7 = Variable R 8 = 77.960 D 8 = 1.50 N 5 = 1.84666 ν 5 = 23.8 R 9 = 31.802 D 9 = 7.50 N 6 = 1.71300 ν 6 = 53.8 R10 = -198.781 D10 = 0.10 R11 = 77.219 D11 = 5.50 N 7 = 1.77250 ν 7 = 49.6 R12 = -168.989 D12 = 1.40 N 8 = 1.84666 ν 8 = 23.8 R13 = 357.536 D13 = 0.10 R14 = 50.032 D14 = 4.50 N 9 = 1.77250 ν 9 = 49.6 R15 = 1036.923 D15 = Variable R16 = (Aperture) D16 = 1.00 R17 = 159.183 D17 = 4.10 N10 = 1.84666 ν10 = 23.8 R18 = -28.287 D18 = 1.10 N11 = 1.77250 ν11 = 49.6 R19 = 53.088 D19 = 2.90 R20 =- 34.394 D20 = 1.10 N12 = 1.83481 ν12 = 42.7 R21 = 122.601 D21 = Variable R22 = -152.863 D22 = 1.40 N13 = 1.84666 ν13 = 23.8 R23 = -275.361 D23 = 3.80 N14 = 1.71300 ν14 = 53.8 R24 = -31.874 D24 = 0.10 R25 = -92.992 D25 = 2.80 N15 = 1.69680 ν15 = 55.5 R26 = -57.447 D26 = 0.10 R27 = 126.107 D27 = 5.00 N16 = 1.71300 ν16 = 53.8 R28 = -38.422 D28 = 1.40 N17 = 1.84666 ν17 = 23.8 R29 = -550.494 Aspheric

[0059]

[Table 6]

R1: Aspherical surface coefficient A = 0 B = 1.90348 × 10 ^-7 C = 2.999605 × 10 ^-10 D = -1.28883 × 10 ^-13 R29: Aspherical surface coefficient A = 0 B = 1.86774 × 10 ^-6 C = 6.79916 × 10 ^-9 D = -7.60901 × 10 ^-12

[0061]

According to the present invention, the total length of the lens is reduced and the lens barrel structure is reduced by specifying the refracting power of the four lens units and the moving conditions of each lens unit upon zooming as described above. It is possible to achieve a zoom lens which has a relatively wide angle of view and high optical performance over the entire zoom range with a high zoom ratio while being simple.

[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 lens cross-sectional view of Numerical Example 5 serving as a reference of the present invention.

FIG. 6 is a lens sectional view of Numerical Example 6 serving as a reference of the present invention.

FIG. 7 is an aberration diagram at a zoom position at a wide-angle end according to Numerical Embodiment 1 of the present invention.

FIG. 8 is an aberration diagram at a zoom position in a numerical example 1 of the present invention.

FIG. 9 is an aberration diagram at a telephoto end zoom position according to Numerical Embodiment 1 of the present invention.

FIG. 10 is an aberration diagram at a zoom position at a wide-angle end according to Numerical Embodiment 2 of the present invention.

FIG. 11 is an aberration diagram at a zoom position in a numerical example 2 of the present invention.

FIG. 12 is an aberration diagram at a zoom position at a telephoto end in Numerical Example 2 of the present invention;

FIG. 13 is an aberration diagram at a zoom position at a wide-angle end according to Numerical Embodiment 3 of the present invention.

FIG. 14 is an aberration diagram at a zoom position in a numerical example 3 of the present invention.

FIG. 15 is an aberration diagram at a zoom position at a telephoto end according to Numerical Example 3 of the present invention;

FIG. 16 is an aberration diagram at a zoom position at a wide angle end according to Numerical Embodiment 4 of the present invention.

FIG. 17 is an aberration diagram at a zoom position in a numerical example 4 of the present invention.

FIG. 18 is an aberration diagram at a telephoto end zoom position in Numerical Example 4 of the present invention.

FIG. 19 is an aberration diagram at a zoom position at a wide-angle end according to Numerical Example 5 serving as a reference of the present invention.

FIG. 20 is an aberration diagram at a zoom position in Numerical Example 5 serving as a reference of the present invention;

FIG. 21 is an aberration diagram at a zoom position at a telephoto end in Numerical Example 5 which is a reference of the present invention.

FIG. 22 is an aberration diagram at a zoom position at a wide-angle end according to Numerical Example 6 serving as a reference of the present invention.

FIG. 23 is an aberration diagram at a zoom position in Numerical Example 6 serving as a reference of the present invention;

FIG. 24 is an aberration diagram at a zoom position at a telephoto end in Numerical Example 6 which is a reference of the present invention.

[Explanation of symbols]

 L1 First group L2 Second group L3 Third group L4 Fourth group SP Aperture d Spherical aberration at Fraunhofer d-line g Spherical aberration at Fraunhofer g-line S, C Unsatisfactory amount under sine condition S Sagittal section Image plane M Image plane in meridional section

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-19169 (JP, A) JP-A-5-134184 (JP, A) JP-A-59-229517 (JP, A) JP-A-61- 62013 (JP, A) JP-A-62-63909 (JP, A) JP-A-2-136812 (JP, A) JP-A-4-163415 (JP, A) JP-A-2-201310 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) G02B 9/00-17/08 G02B 21/02-21/04 G02B 25/00-25/04

Claims (6)

(57) [Claims] A first group having a negative refractive power , in order from the object side;
Second lens unit of positive refractive power, a third lens unit of negative refractive power and a four lens groups of the fourth lens unit of positive refractive power, intends row zooming by changing the air space between the lens units a zoom lens, the second group, alignment adhered 21st lens and both lens surfaces of the negative meniscus form convex toward the object side are joined and the negative second lens 22 of the convex lenses and the object side, A positive twenty-third lens with a strong positive refracting surface facing the lens, the object-side surface of the twenty-first lens or the twenty-third lens being an aspheric surface, and a radius of curvature of a cemented lens surface of the cemented lens. To R2,2,
The lens outer diameter of the 23rd lens is DE, and the focal length of the second group is
The separation is F2, the aspherical shape of the aspherical surface is the X axis in the optical axis direction,
H axis perpendicular to the optical axis, positive in the light traveling direction, half paraxial curvature
Assuming that the diameter is R and the aspheric coefficients are A, B, C, D, and E, A zoom lens characterized by satisfying the following condition : 0.6 <R2, 2 / F2 <1.0 B <0 B + C × (DE / 2) ² <0 2. The first group includes a positive lens and at least two lenses.
2. The apparatus according to claim 1 , further comprising a negative lens.
Zoom lens. 3. The first lens unit includes two lens units, an eleventh lens unit and a twelfth lens unit, in order from the object side, and focuses by moving the twelfth lens unit on the optical axis. Feature
The zoom lens according to claim 1 . 4. A first group having a negative refractive power in order from the object side,
Second lens unit of positive refractive power, a third lens unit of negative refractive power and a four lens groups of the fourth lens unit of positive refractive power, intends row zooming by changing the air space between the lens units A zoom lens , wherein the second group includes a cemented lens formed by joining a negative meniscus twenty-first lens with a convex surface facing the object side and a positive twenty-second lens with both lens surfaces convex, and an object-side lens. A positive 23rd lens with a strong positive refracting surface facing the lens .
The surface on the image side of the lens is an aspheric surface, the radius of curvature of the cemented lens surface of the cemented lens is R2,2, and the lens of the 23rd lens is
Is the outer diameter of the lens, the focal length of the second group is F2,
X-axis in the optical axis direction, H-axis in the direction perpendicular to the optical axis,
The light traveling direction is positive, the paraxial radius of curvature is R, and the aspheric coefficient is
As A, B, C, D, and E, A zoom lens characterized by satisfying the following condition : 0.6 <R2,2 / F2 <1.0 B> 0 B + C × (DE / 2) ² > 0 5. The first group includes a positive lens and at least two lenses.
5. The image forming apparatus according to claim 4 , further comprising a negative lens.
Zoom lens. Wherein said first group comprises, in order from the object side, a 11
The zoom lens according to claim 4 , further comprising two lens groups, a group and a twelfth group, wherein the twelfth group is moved on the optical axis to perform focusing.