JP2000121941A - Zoom lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a zoom lens of a wide angle of view and a high variable magnification ratio which has five lens groups as a whole, executes focusing with the lens groups exclusive of the first group and is reduced in the size over the entire part of the lens system. SOLUTION: The zoom lens has five lens groups; successively from an object side, a first group L1 of positive refracting power, a second group L2 of negative refracting power, a third group L3 of positive refracting power, a fourth group L4 of positive refracting power and fifth group L5 of negative refracting power. The lens executes variable magnification and image plane fluctuation correction accompanying the variable magnification by moving the second group and the fourth group in an optical axis direction. The third group consists of one element of the positive lens of a meniscus shape of which the concave face is directed to the image side. The zoom lens satisfies the conditions 0.35<f3/fT<0.58 when the focal length of the third group is defined as f3 and the focal length of the entire system at a telephoto end as fT.

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 large aperture ratio of about F / 1.8 at a wide-angle end and a high zoom ratio of about 1.8 used in photographic cameras, video cameras and broadcast cameras. And a rear focus type zoom lens.

[0002]

2. Description of the Related Art Conventionally, there have been proposed various types of zoom lenses such as a photographic camera and a video camera which employ a so-called rear focus type in which a lens group other than the first group on the object side is moved to perform focusing. Have been.

In general, a rear-focus type zoom lens has a smaller effective diameter of the first lens group than a zoom lens which moves and focuses the first lens group on the object side, so that the entire lens system can be easily reduced in size. In addition, close-up photography, particularly very close-up photography, is facilitated. Further, since a relatively small and light lens group is moved, the driving force of the lens group is small, so that quick focusing can be performed.

In JP-A-9-159917, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, and a fourth lens unit having a positive refractive power are arranged in this order from the object side. And a fifth lens unit having a negative refractive power, a fifth lens unit. The second lens unit is moved to the image plane side to perform zooming from the wide-angle end to the telephoto end, and the image plane variation accompanying zooming is performed. Is corrected by moving the fourth group, and the fourth group is moved to perform focusing.

[0005]

Generally, when a rear focus system is employed in a zoom lens, the overall lens system can be reduced in size and quick focusing becomes possible as described above, and further advantages such as close-up photographing can be easily obtained. .

However, when trying to reduce the size of the entire lens, the power (refractive power) of each group is increased (increased), which increases the sensitivity of each group, resulting in a large defective rate in actual production. There has been a problem that the efficiency is reduced.

[0007] The sensitivity refers to the displacement of the imaging point on the image plane when each lens group or each lens changes by a unit amount Δx (eg, unit length (mm) or unit angle (minute, second)). It refers to the ratio Δy / Δx to the amount Δy.

For example, the zoom lens proposed in the above-mentioned Japanese Patent Application Laid-Open No. 9-159917 has a problem that the sensitivity of image plane tilt due to parallel eccentricity is large. Image height 0.4m when each group of Example 1 and Example 2 is parallel-eccentric by 0.01mm
The amount of tilt of the meridional image plane at m is as follows.

[0009]

[Table 1] The present invention has excellent optical performance over the entire zoom range from the wide-angle end to the telephoto end while suppressing the enlargement of the entire lens system, and over the entire object distance from an object at infinity to an object at a short distance, and It is an object of the present invention to provide a zoom lens having a simple configuration and a rear focus type zoom lens having a low sensitivity of image plane tilt due to eccentricity of a lens group and having a predetermined back focus.

[0010]

The zoom lens according to the present invention comprises: (1-1) a first group having a positive refractive power, a second group having a negative refractive power, and a third group having a positive refractive power in order from the object side. Group, fourth in positive refractive power
Group, and a fifth lens group having a negative refractive power. The fifth lens group has a negative refractive power. By moving the second group and the fourth group in the direction of the optical axis, zooming and correction of image plane fluctuation accompanying zooming are performed. The third unit is composed of a single meniscus positive lens with the concave surface facing the image side. The focal length of the _{third unit} is f ₃ , and the focal length of the entire system at the telephoto end is f _T. 0.35 <f ₃ / f _T <0.58 (1)

(1-2) A first lens unit having a fixed positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a fixed positive refractive power, and a third lens unit having a positive refractive power are arranged in order from the object side. The fifth lens group includes four lens groups, and a fifth lens group having a fixed negative refractive power.
The fourth lens group is moved to the image plane side to perform zooming from the wide-angle end to the telephoto end, and the image plane fluctuation caused by zooming is corrected by moving the fourth lens group. Of the meniscus shape
It is composed of one positive lens, and the focal length of the third group is f ₃ ,
The focal length of the entire system at the telephoto end is characterized by satisfying _{0.35 <f 3 / f T <} 0.58 ‥‥‥ (1) becomes a condition when the f _T.

(1-3) In order from the object side, the positive refractive power
The first lens group includes a first lens unit, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, a fourth lens unit having a positive refractive power, and a fifth lens unit having a negative refractive power. The second unit and the fourth unit are moved in the optical axis direction to perform zooming and image plane fluctuation correction accompanying zooming, and the third unit has a meniscus shape with a concave surface facing the image side.
The fifth unit is composed of one negative lens, and the fifth unit is composed of one negative lens. The radius of curvature of the lens surface on the object side of the fifth unit is R _51,
When the radius of curvature of the lens surface on the image side and _{R 52, -2 <(R 52} + R 51) / (R 52 -R 51) <- satisfies the 0.7 ‥‥‥ (2) The condition Features.

(1-4) In order from the object side, a first group having a fixed positive refractive power, a second group having a negative refractive power, a third group having a fixed positive refractive power, and a third group having a positive refractive power. The fifth lens group includes four lens groups, and a fifth lens group having a fixed negative refractive power.
The fourth lens group is moved to the image plane side to perform zooming from the wide-angle end to the telephoto end, and the image plane fluctuation caused by zooming is corrected by moving the fourth lens group. Of the meniscus shape
The fifth unit is composed of one negative lens, and the fifth unit is composed of one negative lens. The radius of curvature of the lens surface on the object side of the fifth unit is R _51,
When the radius of curvature of the lens surface on the image side and _{R 52, -2 <(R 52} + R 51) / (R 52 -R 51) <- satisfies the 0.7 ‥‥‥ (2) The condition Features.

[0014]

FIG. 1 is a sectional view showing a numerical example 1 of a rear focus type zoom lens according to the present invention.
3 is a lens sectional view of Numerical Example 2, FIG. 3 is a lens sectional view of Numerical Example 3, FIG. 4 is a lens sectional view of Numerical Example 4, and FIG. 5 is a lens sectional view of Numerical Example 5.

FIGS. 6 to 8 are graphs showing various aberrations at the wide-angle end, a middle position, and a telephoto end according to Numerical Embodiment 1 of the present invention, which will be described later. 9 to 11 show a second embodiment of the present invention, which will be described later, at a wide-angle end, a middle position,
FIG. 7 is a diagram illustrating various aberrations at the telephoto end. 12 to 14 are graphs showing various aberrations at the wide-angle end, a middle position, and a telephoto end in Numerical Example 3 described later of the present invention. 15 to 17 are graphs showing various aberrations at a wide angle end, a middle position, and a telephoto end of a numerical example 4 of the present invention, which will be described later. FIG.
FIG. 20 is a diagram of various aberrations at a wide-angle end, a middle position, and a telephoto end according to Numerical Example 5 described later of the present invention.

In the figure, L1 is a first group having a positive refractive power, L2 is a second group having a negative refractive power, L3 is a third group having a positive refractive power, L4
Is a fourth unit having a positive refractive power, and L5 is a fifth unit having a negative refractive power. SP is an aperture stop, and FP is an image plane.

At the time of zooming from the wide-angle end to the telephoto end, the second lens unit is moved to the image plane side as indicated by an arrow, and the image plane fluctuation caused by zooming is corrected by moving the fourth lens unit. Also, the fourth
A rear focus system that moves the lens group on the optical axis for focusing is adopted.

A solid line curve 4a and a dotted line curve 4b of the fourth lens group shown in FIG. 3 are images when zooming from the wide-angle end to the telephoto end when focusing on an object at infinity and an object at a short distance, respectively. The movement locus for correcting the surface fluctuation is shown. The first
The group, the third group, and the fifth group are fixed during zooming and focusing.

In the present embodiment, the fourth lens unit is moved to correct the image plane fluctuation accompanying zooming, and the fourth lens unit is moved to perform focusing. In particular, curve 4 in FIG.
When zooming from the wide-angle end to the telephoto end, the lens is moved so as to have a convex trajectory toward the object side as shown in FIGS.
Thereby, the space between the third and fourth units is effectively used, and the overall length of the lens is effectively reduced.

In this embodiment, for example, when focusing from an object at infinity to an object at a short distance at the telephoto end,
This is performed by extending the fourth lens group forward as indicated by the straight line 4c in FIG.

In this embodiment, focusing may be performed by a lens group other than the fourth group (for example, one of the first, third, and fifth groups).

In the present embodiment, as described above, the lens system is composed of five lens units having a predetermined refractive power, and moving the second and fourth units during zooming and focusing is a basic configuration of the first to fourth inventions. And

Next, the features of each invention will be described.

(A-1) The second unit and the fourth unit are moved in the direction of the optical axis to perform zooming and image plane fluctuation correction accompanying zooming, and the third unit is concave on the image side. consists of one positive lens of meniscus shape, the focal length of the third group f _3, 0.35 when the focal length of the entire system at the telephoto end and _{f T <f 3 / f T} <0.58 ‥‥ Satisfies the following condition (1).

(A-2) In the second invention, the first, third, and fifth units are fixed in the basic configuration, and the second unit is moved to the image plane side to change the magnification from the wide-angle end to the telephoto end. The fourth lens group is moved to correct the image plane fluctuation caused by zooming, and the third lens group is composed of one meniscus positive lens having a concave surface facing the image side. Assuming that the focal length is f ₃ and the focal length of the entire system at the telephoto end is f _T , the condition 0.35 <f ₃ / f _T <0.58 (1) is satisfied.

(A-3) The third invention has a basic structure
By moving the second unit and the fourth unit in the optical axis direction, zooming and image plane variation correction accompanying zooming are performed.
The group consists of a single meniscus positive lens with the concave surface facing the image side, the fifth group consists of a single negative lens, and the radius of curvature of the object-side lens surface of the fifth group is R _51, when the radius of curvature of the lens surface on the image side and _{R 52, -2 <(R 52} + R 51) / (R 52 -R 51) <- 0.7 ‥‥‥ (2) becomes by satisfying the conditions is there.

(A-4) In a fourth aspect of the present invention, the first, third, and fifth units are fixed in the basic configuration, and the second unit is moved to the image plane side to change the magnification from the wide-angle end to the telephoto end. The fourth group is moved to correct the image plane fluctuation caused by zooming, and the third group is composed of a single meniscus positive lens having a concave surface facing the image side. consists of one negative lens, when the radius of curvature of the lens surface on the object side of the fifth group R _51, the radius of curvature of the lens surface on the image plane side and _{R 52, -2 <(R 52} + R 51 ) / (R ₅₂ −R ₅₁ ) <− 0.7 ‥‥‥ (2)

Next, the features of each of the above-described inventions will be described. The shape of the third group is reduced by reducing the power of the third group.
When the principal point of the relay system after the group moves to the image side, the zooming range of the second group moves to the telephoto side, and the second group approaches the image plane side. Accordingly, it is necessary to move the principal point of the third lens group toward the object side in order to ensure a sufficient air gap between the second lens group and the third lens group at the telephoto end.

Thus, the zoom lens has an F-number of about 1.8 at the wide-angle end and a zoom ratio of about 10, and extends over the entire zoom range from the wide-angle end to the telephoto end, and over the entire object distance from an object at infinity to a very close object. A zoom lens having excellent optical performance and low sensitivity to image plane tilt due to eccentricity of the lens group is obtained.

Next, the technical meaning of the conditional expression (1) will be described. If the lower limit of conditional expression (1) is exceeded, it is possible to reduce the overall length of the lens, but the power of the third lens unit becomes too strong, which increases sensitivity and also makes aberration correction strict, which is not preferable. Conversely, if the upper limit is exceeded, the power of the third lens group becomes weaker, lowering the sensitivity and making it easier to correct aberrations, but it is difficult to reduce the overall length of the lens, and the lens diameter of the fourth lens group, which is the moving lens group, becomes undesirably large. .

Here, the reason why the sensitivity of the image plane falling due to the parallel eccentricity of the lens groups is reduced will be described below. This is explained using Yoshiya Matsui's theory of third-order aberrations in optical systems with eccentricity (JOEM technical course text).

Assuming that the optical system is composed of k elements, the lateral aberration when there is eccentricity is developed as follows.

[0033]

(Equation 3) In these equations, the first square on the right side is a term representing the original aberration of the optical system when there is no eccentricity. If eccentricity exists, the aberration term caused by the eccentricity is added. In these equations, N is the refractive index of the object field, and a 'is the value in the image space of the paraxial ray of the object used in calculating the aberration coefficient. The index ν represents an element number.

The eccentricity of the element includes a form in which the element moves parallel to a direction perpendicular to the reference axis of the optical system and a form in which the element tilts with respect to the reference axis. Expressed as a term. This time, we consider only the case of parallel movement.

Assume that the optical axis of the ν-th element has moved by a value Eν in parallel with the reference axis (optical axis) of the optical system as shown in FIG.

Assuming that an arbitrary νth element in the optical system has been translated by Eν in the Y direction with respect to the reference axis,
The additional terms of lateral aberration due to Eν are ΔY (Eν) and Δ
When written as Z (Eν), they are expressed as follows.

[0037]

(Equation 4) These are eccentric aberration coefficients representing the influence of eccentricity, and serve to represent imaging defects having the following contents, respectively.

(ΔE) ν : Prism effect (lateral displacement of image) (VE1) ν (VE2) ν: rotationally asymmetric distortion (IIIE) ν (PE) ν : Rotationally asymmetric astigmatism, image plane tilt (IIE) ν : Rotationally asymmetrical coma aberration also appearing on the axis The deviation of the meridian and the sphere missing image point in the optical axis direction due to the inclination of the image plane is written as ΔM (E ν) ΔS (E ν) as follows. Is represented.

ΔM (E ν) = (N ′ / a ′ ² ) ｛[3
(IIIE) ν + (PE) ν] tan ω｝ EνΔS (Eν) = (N ′ / a ′ ² ) ｛[(IIIE) ν + (P
E) ν] tan ω｝ E ν It can be seen that if the absolute values of (IIIE) ν and (PE) ν in this equation are reduced, the image plane tilt due to parallel eccentricity is reduced.

Here, (IIIE) ν and (PE) ν are modified.
Let h be the height of the axial marginal ray in the principal plane of the ν group
ν, its incident angle is aν, its outgoing angle is aν ′,

[0041]

[Outside 1] The power of the ν group is φν, and the average refractive index of the ν group is Nν.

[0042]

(Equation 5) Becomes

With respect to (PE) ν, it can be seen from the expanded expression of (PE) ν in the above equation that the absolute value decreases as the power of each group is reduced. However, it is not preferable to reduce the power of all the groups because the total length becomes long. Since the first and second lens groups are portions that perform zooming, if the power is reduced, the moving distance increases and the overall length becomes longer, which is not preferable. In the relay systems of the third group and thereafter, weakening the power of the third group, which is a problem at the telephoto end in the second embodiment of JP-A-9-159917, is effective to lower the sensitivity of the third group. .

With respect to (IIIE) ν, it can be understood from the above expression that the sensitivity can be reduced by reducing the coma and astigmatism coefficient of each group from the expanded expression of (IIIE) ν in the above expression.

Next, the features of the third and fourth inventions will be described. In the third and fourth inventions, as described above, the radius of curvature of the object side lens surface of the fifth lens unit is R51, and the radius of curvature of _the image surface side lens surface is _R52.
Where the shape factor of the fifth group is conditional expression (2)
Are satisfied.

When the power of the third lens unit is reduced, the power of the fourth lens unit is increased, and the principal point of the combining system of the third and fourth lens units moves to the image side. In order to enhance the effect of the telephoto type of the relay system after the third group, it is better that the principal point of the fifth group is separated to some extent from the principal point of the combined system of the third and fourth groups. Within the range of conditional expression (2), the power of the image-side lens surface of the fifth lens unit becomes larger than the power of the object-side lens surface. The effect increases.

If the upper limit of conditional expression (2) is exceeded, the principal point of the fifth group moves to the object side, and the effect of the telephoto type is weakened, and the total length is undesirably increased. If the lower limit of conditional expression (2) is exceeded, the radius of curvature of both surfaces will be small, so that aberration correction will be strict, making it difficult to apply to a video camera or the like.

In this embodiment, the aperture stop SP is connected to the second group.
By arranging it between L2 and the third lens unit L3, an increase in the front lens diameter is reduced.

The present invention determines each element as described above,
While reducing the sensitivity while reducing the size of the lens system and correcting various aberrations well, in order to further reduce the sensitivity and ensure good optical performance, at least one of the following conditions
Good to satisfy one. (B-1) The radius of curvature of the lens surface on the object side of the third group is R31 _,
When the radius of curvature of the lens surface on the image side and R _32, is to satisfy _{1.0 <(R 32 + R 31} ) / (R 32 -R 31) <2.6 ‥‥‥ (3) becomes a condition.

The third lens unit has a meniscus shape in order to reduce the overall length of the lenses of the third lens unit and thereafter. If the upper limit of conditional expression (3) is exceeded, the radius of curvature of both surfaces of the third lens unit becomes small, so that aberration correction becomes severe. If the lower limit is exceeded, the object-side principal point of the third lens unit moves to the image side, so that the distance between the second lens unit and the third lens unit becomes too small at the telephoto end.

(A-2) When the zoom ratio is Z and the lateral magnification of the second lens unit at the telephoto end is β _2T

[0052]

(Equation 6) Satisfying the following conditions.

If the upper limit of conditional expression (4) is exceeded, it is difficult to increase the focal length at the telephoto end unless the absolute value of the lateral magnification of the relay systems of the third and subsequent groups is increased. Must be moved to the object side, which increases the power of the third group. This makes it possible to reduce the overall length of the lens, but undesirably increases the sensitivity of the third lens unit. Conversely, if the lower limit is exceeded, the amount of movement of the conjugate point on the object side of the second lens unit increases, so that the amount of movement of the fourth lens unit increases and the fourth lens unit approaches the image plane side at the telephoto end, so that the back focus is sufficient. It is not preferable because it cannot be removed.

(A-3) The focal length of the second lens unit is f ₂ ,
When the imaging magnification of the fifth group is β ₅ and the focal length of the entire system at the wide-angle end is f _W ,

[0055]

(Equation 7) Satisfying the following conditions.

The conditional expressions (5) and (6) are mainly for shortening the overall length of the lens while maintaining good optical performance. Of these, the conditional expression (5) relates to the negative refracting power of the second lens unit, and is mainly for effectively obtaining a predetermined zoom ratio while reducing aberration fluctuation due to zooming. If the refractive power of the second lens unit becomes too strong beyond the lower limit, miniaturization of the entire lens system becomes easy, but the Petzval sum increases in the negative direction, the curvature of field increases, and aberration fluctuations accompanying zooming occur. Becomes larger. Also, if the negative refractive power of the second group becomes too weak beyond the upper limit, the fluctuation of aberration due to zooming decreases,
The amount of movement of the second lens unit for obtaining a predetermined zoom ratio increases, and the overall length of the lens becomes longer.

Condition (6) relates to the imaging magnification of the fifth lens unit. If the magnification of the fifth lens unit is reduced below the lower limit of conditional expression (6), a sufficient effect of shortening the entire lens length cannot be obtained. Conversely, if the magnification exceeds the upper limit and the magnification increases, it is advantageous for shortening the overall length of the lens, but the Petzval sum increases in the negative direction, making it difficult to correct the curvature of field and considerably deteriorating the telecentricity. It becomes difficult to apply.

(A-4) The second, third, and fourth groups each have at least one aspheric surface.

The expansion formula of (IIIE) v above

[0060]

(Equation 8) As can be seen from the above, in order to reduce the absolute value of (IIIE) in each group, the absolute values of the coma aberration coefficient and the astigmatism coefficient of each group may be reduced. The number of lenses in the entire system is 1
To reduce the overall length, reduce the sensitivity, and maintain good optical performance while reducing the number to about 0, the second, third,
By using at least one aspheric surface for each of the four groups, the coma and astigmatism coefficient can be reduced by increasing the degree of freedom of each group.

(A-5) The first unit is composed of a cemented lens in which a negative lens and a positive lens are cemented, and a meniscus-shaped positive lens having a convex surface facing the object side.

(A-6) The second unit is composed of a negative lens having a concave surface facing the image surface side and a cemented lens in which a biconcave negative lens and a positive lens are cemented from the object side.

(A-7) The fourth unit is composed of a cemented lens in which a negative lens having a concave surface facing the image surface side and a positive lens are cemented.

(A-8) The fifth unit is composed of one negative lens.

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. In addition, R19 and R20 in the numerical examples indicate an optical filter, a face plate, and the like, but these may be omitted as necessary.

The aspherical 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 represents a paraxial radius of curvature, and B, C, D, and E represent aspherical coefficients. And when

[0067]

(Equation 9) It is represented by the following expression. “DX” means “10-X”.

Table 1 shows the relationship between the above-described conditional expressions and various numerical values in the numerical examples. Table 2 shows the image height when each group was decentered by 0.01 mm at the wide-angle end and telephoto end in each example.
The amount of tilt of the meridional image plane at 0.4 mm is shown.

[0069]

[Table 2]

[0070]

[Outside 2] no 1 2 3 asph 8 r -1.15329D + 00 k -9.16983D-02 B 2.39807D-02 4 5 6 C 1.99940D-02 D -8.73559D-02 E 2.03904D-02 no 1 2 3 asph 12 r 1.72241 D + 00 k -8.83833D-01 B 8.41015D-02 4 5 6 C -2.83735D-02 D 6.11850D-03 E 3.33079D-02 no 1 2 3 asph 13 r 4.88624D + 00 k 0 B 1.18602D- 01 4 5 6 C 5.26977D-03 D -9.33460D-02 E 1.20745D-01 no 1 2 3 asph 16 r -2.24309D + 00 k -1.73880D + 01 B -1.12318D-01 4 5 6 C 1.98122D -01 D -2.02820D-01 E 9.36941D-02

[0071]

[Outside 3] no 1 2 3 asph 8 r -1.13700D + 00 k -1.97957D-02 B 2.34603D-02 4 5 6 C 1.96955D-02 D -8.55351D-02 E 1.98456D-02 no 1 2 3 asph 12 r 1.56872 D + 00 k -9.42034D-01 B 8.23761D-02 4 5 6 C -2.79498D-02 D 5.99097D-03 E 3.24180D-02 no 1 2 3 asph 13 r 6.87807D + 00 k 0 B 1.18320D- 01 4 5 6 C 5.19106D-03 D -9.14003D-02 E 1.17519D-01 no 1 2 3 asph 16 r -2.33263D + 00 k -1.73965D + 01 B -1.11260D-01 4 5 6 C 1.95164D -01 D -1.98592D-01 E 9.11908D-02

[0072]

[Outside 4] no 1 2 3 asph 8 r -1.15113D + 00 k -1.04274D-01 B 2.41321D-02 4 5 6 C 2.00910D-02 D -8.79497D-02 E 2.05688D-02 no 1 2 3 asph 12 r 1.83286 D + 00 k -8.69276D-01 B 8.46516D-02 4 5 6 C -2.85111D-02 D 6.16009D-03 E 3.35993D-02 no 1 2 3 asph 13 r 4.15762D + 00 k 0 B 1.18699D- 01 4 5 6 C 5.29532D-03 D -9.39805D-02 E 1.21801D-01 no 1 2 3 asph 16 r -2.23422D + 00 k -1.73875D + 01 B -1.12879D-01 4 5 6 C 1.99083D -01 D -2.04199D-01 E 9.45138D-02

[0073]

[Outside 5] no 1 2 3 asph 4 r 2.64994D + 00 k 1.49985D-01 B -1.02989D-03 4 5 6 C -1.53753D-04 D -4.72016D-05 E 0 no 1 2 3 asph 6 r 3.27626D + 00 k 2.04048D + 00 B 9.70004D-03 4 5 6 C 1.47115D-02 D -5.10136D-02 E 3.66631D-02 no 1 2 3 asph 11 r 2.06849D + 00 k -9.72013D-01 B 8.39947D- 02 4 5 6 C 1.82724D-02 D 4.15479D-02 E 7.77601D-02 no 1 2 3 asph 12 r 2.35206D + 02 k 0 B 1.14020D-01 4 5 6 C 5.24969D-02 D -3.44411D- 02 E 2.12667D-01 no 1 2 3 asph 16 r -2.03212D + 00 k -1.65928D + 01 B -1.29019D-01 4 5 6 C 3.35600D-01 D -5.98003D-01 E 4.96987D-01 no 1 2 3 asph 17 r -1.14512D + 01 k -1.26841D + 02 B 2.27399D-02 4 5 6 C -2.77474D-02 D -7.20694D-02 E -5.52461D-04

[0074]

[Outside 6] no 1 2 3 asph 4 r 2.66071D + 00 k 9.83605D-02 B -5.46397D-04 4 5 6 C -2.29039D-04 D 6.16041D-08 E 0 no 1 2 3 asph 6 r 3.06149D + 00 k 5.83760D + 00 B -1.42163D-02 4 5 6 C 1.36945D-02 D -6.07012D-02 E 3.49804D-02 no 1 2 3 asph 12 r 1.81589D + 00 k -7.76120D-01 B 6.73261D- 02 4 5 6 C 1.98585D-02 D 6.08651D-03 E 4.69889D-02 no 1 2 3 asph 13 r 7.85525D + 00 k 0 B 9.92925D-02 4 5 6 C 1.77899D-02 D -9.08348D- 02 E 1.29887D-01 no 1 2 3 asph 16 r -2.25056D + 00 k -1.77664D + 01 B -1.04049D-01 4 5 6 C 2.08692D-01 D -2.36417D-01 E 1.24455D-01 no 1 2 3 asph 17 r -3.07822D + 01 k 1.04752D + 03 B 1.16160D-02 4 5 6 C -9.42693D-03 D 1.58929D-02 E 1.04702D-02

[0075]

According to the present invention, by setting the lens configuration as described above, it is possible to suppress the enlargement of the entire lens system while covering the entire zoom range from the wide-angle end to the telephoto end, and from the object at infinity to the near end. Over the entire object distance to the distance object,
It is possible to achieve a zoom lens having a predetermined back focus and a rear focus type zoom lens having excellent optical performance, low sensitivity to image plane tilt due to eccentricity of a lens group, and a low focus.

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

FIG. 7 is an intermediate aberration diagram of the numerical example 1 of the present invention.

FIG. 8 is an aberration diagram at a telephoto end in Numerical Example 1 of the present invention;

FIG. 9 is an aberration diagram at a wide-angle end according to Numerical Example 2 of the present invention.

FIG. 10 is a diagram showing aberrations in the middle of the numerical example 2 of the present invention.

FIG. 11 is an aberration diagram at a telephoto end in Numerical Example 2 of the present invention.

FIG. 12 is an aberration diagram at a wide angle end according to Numerical Example 3 of the present invention.

FIG. 13 is an intermediate aberration diagram of the numerical example 3 of the present invention.

FIG. 14 is an aberration diagram at a telephoto end in Numerical Example 3 of the present invention.

FIG. 15 is an aberration diagram at a wide angle end according to Numerical Example 4 of the present invention.

FIG. 16 is an intermediate aberration diagram of the numerical example 4 of the present invention.

FIG. 17 is an aberration diagram at a telephoto end in Numerical Example 4 of the present invention.

FIG. 18 is an aberration diagram at a wide angle end according to Numerical Example 5 of the present invention.

FIG. 19 is an intermediate aberration diagram of the numerical example 5 of the present invention.

FIG. 20 is an aberration diagram at a telephoto end in Numerical Example 5 of the present invention.

FIG. 21 is an explanatory diagram of an eccentric aberration in the optical system according to the present invention.

[Explanation of symbols]

 L1: First group L2: Second group  L3: Third group  L4: 4th group  L5: Group 5  SP: Aperture  FP: Image plane

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H087 KA02 KA03 MA12 MA14 MA15 MA16 PA07 PA20 PB10 QA02 QA06 QA17 QA21 QA25 QA37 QA39 QA41 QA46 RA05 RA12 RA13 RA32 RA42 SA43 SA47 SA49 SA52 SA56 SA63 SA65 SA72 SA74 SA76 SB04 SB34 SB42 9A001 KK16

Claims (14)

[Claims] 1. A first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, a fourth lens unit having a positive refractive power, and a negative refractive power in order from the object side. The fifth lens group includes a fifth lens group, and the second lens group and the fourth lens group are moved in the optical axis direction to perform zooming and image plane variation correction accompanying zooming. There consists of one positive meniscus lens having a concave surface facing the image side, 0.35 when the focal length of the third group f _3, a focal length of the entire system at the telephoto end and f _T <f ₃ / f A zoom lens that satisfies the condition of _T <0.58. 2. The first positive refractive power, which is fixed in order from the object side.
Group, second group with negative refractive power, second group with fixed positive refractive power
The zoom lens has five lens groups: three groups, a fourth group having a positive refractive power, and a fifth group having a fixed negative refractive power.The second group is moved to the image plane side to move from the wide-angle end to the telephoto end. The fourth group is moved to correct the image plane fluctuation accompanying the zooming, and the third group is composed of one meniscus-shaped positive lens having a concave surface facing the image side. A zoom lens characterized by satisfying the following condition: 0.35 <f ₃ / f _T <0.58, where f _{3 is} the focal length of the _third lens unit and f _T is the focal length of the entire system at the telephoto end. 3. A first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, a fourth lens unit having a positive refractive power, and a negative refractive power in order from the object side. The fifth lens group includes a fifth lens group, and the second lens group and the fourth lens group are moved in the optical axis direction to perform zooming and image plane variation correction accompanying zooming. Consists of a single meniscus positive lens with the concave surface facing the image side, and the fifth group consists of a single negative lens.
When the radius of curvature of the lens surface on the object side of the fifth group R _51, the radius of curvature of the lens surface on the image plane side and _{R 52, -2 <(R 52} + R 51) / (R 52 -R 51 ) <-0.7. A zoom lens characterized by satisfying the following condition. 4. A first positive refractive power which is fixed in order from the object side.
Group, second group with negative refractive power, second group with fixed positive refractive power
The zoom lens has five lens groups: three groups, a fourth group having a positive refractive power, and a fifth group having a fixed negative refractive power.The second group is moved to the image plane side to move from the wide-angle end to the telephoto end. The fourth group is moved to correct the image plane fluctuation accompanying the zooming, and the third group is composed of one meniscus-shaped positive lens having a concave surface facing the image side. The fifth group includes one negative lens,
When the radius of curvature of the lens surface on the object side of the fifth group R _51, the radius of curvature of the lens surface on the image plane side and _{R 52, -2 <(R 52} + R 51) / (R 52 -R 51 ) <-0.7. A zoom lens characterized by satisfying the following condition. 5. When the radius of curvature of the lens surface on the object side of the third lens unit is R _{31 and the} radius of curvature of the lens surface on the image surface side is R ₃₂ , 1.0 <(R ₃₂ + R ₃₁ ) / (R ₃₂ -R ₃₁₎ <any one of the zoom lens of claims 1 to 4, characterized by satisfying 2.6 following condition. 6. When the zoom ratio is Z and the lateral magnification at the telephoto end of the second group is β _2T , The zoom lens according to any one of claims 1 to 5, wherein the following condition is satisfied. 7. An apparatus according to claim 1, further comprising an aperture stop between said second group and said third group.
Term zoom lens. 8. The focal length of the second lens unit is f ₂ ,
When the imaging magnification of the group is β ₅ and the focal length of the entire system at the wide-angle end is f _W , The zoom lens according to any one of claims 1 to 7, wherein the following condition is satisfied. 9. The zoom lens according to claim 1, wherein each of the second, third, and fourth units has at least one aspheric surface. 10. The zoom lens according to claim 1, wherein the fourth lens unit is moved in an optical axis direction to correct a focus position with respect to a change in an object distance. 11. The lens system according to claim 1, wherein the first group includes a cemented lens in which a negative lens and a positive lens are cemented and a meniscus-shaped positive lens having a convex surface facing the object side. Item 1. Zoom lens. 12. The second lens unit according to claim 1, wherein the second lens unit includes a negative lens having a concave surface facing the image surface side and a cemented lens in which a biconcave negative lens and a positive lens are cemented from the object side.
To 11 zoom lenses. 13. The zoom lens according to claim 1, wherein the fourth unit includes a cemented lens in which a negative lens having a concave surface facing the image surface and a positive lens are cemented. . 14. The zoom lens according to claim 1, wherein the fifth group includes one negative lens.