JP2000121938A - Zoom lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain excellent optical performance, to make sensitivity low and to obtain specified back focus by providing a zoom lens with 1st to 5th lens groups and making it satisfy a specified condition. SOLUTION: The 2nd and the 4th groups are moved in an optical axis direction so as to perform variable power and the automatic correction of an image surface associated with the variable power. Assuming that a distance from a 1st lens surface on an object side to a paraxial image surface is TD and the focal distance of an entire system at a telephoto end is fT, the zoom lens satisfies a conditional expression TD/fT<1.2. Assuming that the tertiary coma aberration coefficients of the 3rd group to the 5th group at the telephoto end in the case of setting that the initial value of the angle of an axial marginal light beam at a wide-angle end is 0, the initial value of the height thereof is 1, and the initial value of the angle of an off-axis principal light beam is -1 are II3r, II4r and II5r in order, and the tertiary astigmatism coefficients of the 3rd group to the 5th group at the telephoto end are III3r, III4r and III5r in order, the lens satisfies conditional expressions (II3r)2+(II4r)2 (II5r)2 <2 and (III3r)2+(III4r)2+(III5r)2 <2.

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.

Japanese Patent Application Laid-Open No. 9-068565 discloses a first group of positive refractive power and a second group of negative refractive power in order from the object side.
Group, a third group having a positive refractive power, a fourth group having a positive refractive power, and a fifth group having a negative refractive power. The second group is moved to the image plane side. Zooming from the wide-angle end to the telephoto end is performed, and the image plane fluctuation due to zooming is corrected by moving the fourth unit, and the fourth unit is moved to perform focusing.

[0006]

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, if the entire lens is reduced in size, the power (refractive power) of each group increases (increases), and therefore, the sensitivity increases, and defects such as one-sided blur occur in actual production. There has been a problem that the probability increases, and as a result, the production efficiency deteriorates.

The sensitivity is defined as the displacement of an image point on an image plane when each lens group or each lens changes by a unit amount Δx (for example, unit length (mm) or unit angle (minute, second)). It refers to the ratio Δy / Δx to the amount Δy.

Further, when the power of each group is reduced in order to suppress the sensitivity, there has been a problem that the total length becomes longer.

[0010] For example, in a zoom lens proposed in the aforementioned JP-A 9-159917 discloses, the ratio TD / f _T of the total length f _T of the full-length TD and the telephoto end 1.07 (Example 1), 1.01
(Example 2) is smaller. However, there is a problem that the sensitivity of the image plane to fall due to the parallel eccentricity is high. Each group of Example 1 and Example 2 in the publication is 0.01%.
The amount of inclination of the meridional image plane when mm is decentered in parallel is as follows.

[0011]

[Table 1] In the zoom lens proposed in the above-mentioned Japanese Patent Application Laid-Open No. 9-68653, the sensitivity of image plane tilt due to parallel eccentricity is small. The amount of tilt of the meridional image plane when each group of Example 2 in the publication is decentered in parallel by 0.01 mm is as follows. Examples 1 and 2 of JP-A-9-159917
It can be seen that the sensitivity is smaller than that of. The table below shows values when the focal length at the wide-angle end is normalized to 1.

[0012]

[Table 2] However, the zoom lens proposed in Japanese Patent Application Laid-Open No. 9-68653 has a total length TD and a focal length f _T at the telephoto end.
The ratio of the are has become relatively large TD / f _T = 1.48.

According to the present invention, 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 an object at a short distance, the size of the entire lens system is suppressed.
It is an object of the present invention to provide a simple configuration zoom lens and a rear focus type zoom lens having good optical performance, low sensitivity, and a predetermined back focus.

[0014]

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. When the distance from the first lens surface on the object side to the paraxial image plane is TD, and the focal length of the entire system at the telephoto end is f _T , the following condition is satisfied: TD / f _T <1.2 ‥‥‥ (1) When the initial value of the angle of the axial marginal ray at the wide-angle end is 0, the initial value of the height is 1, and the initial value of the angle of the off-axis chief ray is -1, the third and fourth groups at the telephoto end. , 5th group 3
The following coma aberration coefficients are II _3T , II _4T , II _5T, and the third-order astigmatism coefficients of the third, fourth, and fifth groups at the telephoto end are III _3T ,
When III _4T and III _5T are used, (II _3T ) ² + (II _4T ) ² + (II _5T ) ² <2 ‥‥‥ (2) (III _3T ) ² + (III _4T ) ² + (III _5T ) ² <2 こ と (3) A zoom lens characterized by satisfying the following condition:

(1-2) 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 fourth group having a positive refractive power. Group, and a fifth lens group of a fixed negative refractive power fifth group. The second group is moved to the image plane side to perform zooming from the wide-angle end to the telephoto end. When the fourth lens group is moved to correct the image plane variation, the distance from the first lens surface on the object side to the paraxial image plane is TD, and the focal length of the entire system at the telephoto end is f _T , TD / F _T <1.2 ‥‥‥ (1), the initial value of the angle of the axial marginal ray at the wide-angle end is 0, the initial value of the height is 1, and the initial value of the angle of the off-axis principal ray is −1. 3rd, 4th, 5th group 3 at the telephoto end
The following coma aberration coefficients are III _3T , II _4T , II _5T, and the third-order astigmatism coefficients of the third, fourth, and fifth groups at the telephoto end are III, respectively.
_{Assuming 3T} , III _4T , and III _5T , (II _3T ) ² + (II _4T ) ² + (II _5T ) ² <2 ‥‥‥ (2) (III _3T ) ² + (III _4T ) ² + (III _5T ) ² <2 ‥‥‥ (3) A zoom lens satisfying the following condition:

[0016]

FIG. 1 is a sectional view of a zoom lens using a rear focus type according to a first embodiment of the present invention, FIG. 2 is a sectional view of a zoom lens according to a second embodiment, and FIG. 3 is a third embodiment of the present invention. 4 is a lens cross-sectional view of Numerical Embodiment 4, FIG. 5 is a lens cross-sectional view of Numerical Embodiment 5, FIG. 6 is a lens cross-sectional view of Numerical Embodiment 6, and FIGS. FIG. 10 is a diagram illustrating various aberrations of the numerical example 1 described later at a wide angle end, a middle position, and a telephoto end.

FIGS. 10 to 12 are graphs showing various aberrations at a wide angle end, a middle position, and a telephoto end according to a second embodiment of the present invention, which will be described later.

FIGS. 13 to 15 are graphs showing various aberrations at the wide-angle end, a middle position, and a telephoto end according to a third embodiment of the present invention, which will be described later.

FIGS. 16 to 18 are graphs showing various aberrations at a wide angle end, a middle position, and a telephoto end according to a fourth embodiment of the present invention, which will be described later.

FIGS. 19 to 21 are graphs showing various aberrations at the wide-angle end, a middle position, and a telephoto end in a numerical example 5 described later of the present invention.

FIGS. 22 to 24 are graphs showing various aberrations at a wide angle end, a middle position, and a telephoto end according to a fifth embodiment of the present invention, which will be described later.

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 denotes an aperture stop, which is arranged between the second unit L2 and the third unit L3. 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 accompanying 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. 4 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 this embodiment, the fourth lens unit is moved to correct the image plane fluctuation caused by zooming, and the fourth lens unit is moved for 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, 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 and second inventions. And Next, the features of each invention will be described.

(A-1) In the first invention, in the basic configuration,
By moving the second group and the fourth group in the optical axis direction, magnification and image plane fluctuation correction accompanying magnification are corrected, and the distance from the first lens surface on the object side to the paraxial image plane is calculated by TD. , when the focal length of the entire system at the telephoto end and _{f T, TD / f T <} 1.2 satisfied ‥‥‥ (1) the condition, 0 initial price of the angle of an axial marginal ray at the wide angle end, the height 3 of the third, fourth, and fifth groups at the telephoto end when the initial value of is set to 1 and the initial value of the angle of the off-axis principal ray is set to -1.
The following coma aberration coefficients are III _3T , II _4T , II _5T, and the third-order astigmatism coefficients of the third, fourth, and fifth groups at the telephoto end are III, respectively.
_{Assuming 3T} , III _4T , and III _5T , (II _3T ) ² + (II _4T ) ² + (II _5T ) ² <2 ‥‥‥ (2) (III _3T ) ² + (III _4T ) ² + (III _5T ) ² <2 ‥‥‥ (3).

(A-2) In the second invention, in the basic structure,
The second lens unit is moved to the image plane side to change the magnification from the wide-angle end to the telephoto end, and the image plane fluctuation due to the zooming is corrected by moving the fourth unit, and the first lens on the object side is corrected. when the distance from the surface to the paraxial image plane TD, the focal length of the entire system at the telephoto end and f _T, satisfies the _{TD / f T <1.2 ‥‥‥ (} 1) becomes a condition, on the wide-angle end shaft When the initial value of the angle of the marginal ray is 0, the initial value of the height is 1, and the initial value of the angle of the off-axis chief ray is -1, the third, fourth, and fifth groups at the telephoto end are set.
The following coma aberration coefficients are III _3T , II _4T , II _5T, and the third-order astigmatism coefficients of the third, fourth, and fifth groups at the telephoto end are III, respectively.
_{Assuming 3T} , III _4T , and III _5T , (II _3T ) ² + (II _4T ) ² + (II _5T ) ² <2 ‥‥‥ (2) (III _3T ) ² + (III _4T ) ² + (III _5T ) ² <2 ‥‥‥ (3).

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 covers an entire zoom range from the wide-angle end to the telephoto end, and an object distance from an object at infinity to a very close object. A compact zoom lens having good optical performance over the whole, and small sensitivity is obtained.

Next, the technical meaning of the conditional expression (1) will be described. If the upper limit of conditional expression (1) is exceeded, the power of each lens unit can be weakened, so that the sensitivity is lowered and aberration correction is facilitated, but the overall length of the lens is undesirably increased.

Next, the technical meaning of conditional expressions (2) and (3) will be described. First, regarding the relationship between the parallel eccentricity of the lens group and the sensitivity of image plane tilt, Yoshiya Matsui's third-order aberration theory of optical systems with eccentricity (JOEM technical course text)
This will be described with reference to FIG.

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

[0035]

(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.

As shown in FIG. 25, it is assumed 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.

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.

[0039]

(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 (Eν) = (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 ′,

[0043]

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

[0044]

(Equation 5) Becomes

From the above expressions of ΔM (Eν) and ΔS (Eν), if the absolute values of (IIIE) ν and (PE) ν can be reduced, it is possible to reduce the inclination of the image plane due to parallel eccentricity. it can. Regarding (PE) ν, the above expansion formula of (PE) ν shows that the absolute value of (PE) ν decreases as the power of each group decreases, but the overall length increases as the power of each group decreases. Therefore, it is difficult to reduce the absolute value of (PE) ν in all groups. Therefore, it is important to reduce the absolute value of (IIIE) v in each group in order to reduce the image plane tilt due to parallel eccentricity. To reduce the absolute value of (IIIE) ν in each group, the above (IIIE) ν It can be seen from the above expansion equation that the absolute values of the coma aberration coefficient and the astigmatism coefficient of each group should be reduced. Here, the coma of each group at the telephoto end in Example 2 of JP-A-09-159917, the astigmatism coefficient, (P
E) ν and (IIIE) ν are shown in the table below.

[0046]

[Table 3] As can be seen from the above table, the coma and astigmatism coefficients cancel each other in the first and second groups with large absolute values, and cancel out in the third, fourth and fifth groups with small absolute values. Although the overall performance is improved, the absolute value of the aberration coefficient of each group, especially the coma aberration coefficient is large,
IE) ν Has increased and the sensitivity has increased.

Here, if the absolute values of the coma aberration coefficients of the third, fourth, and fifth groups can be reduced so as to satisfy the conditional expression (2), the eccentric astigmatism coefficient (IIIE) of the second and subsequent groups ν
IIμ in parentheses in the equation The sum of IIIμ can be reduced, and as a result, the sensitivity of each group can be reduced.

The radius of the ν plane is rν, the refractive index is Nν,
The height hν of the on-axis marginal ray, its incident angle is aν,

[0049]

(Equation 6) It is expressed as

That is, the smaller the absolute value of the coma aberration coefficient, the smaller the absolute value of the astigmatism coefficient. This makes it possible to reduce the inclination of the image plane due to parallel eccentricity. The initial value of the angle of the on-axis marginal ray at the wide-angle end is 0, the initial value of the height is 1, and the initial value of the angle of the off-axis principal ray is −1.
When the coma aberration coefficient II _2T of the second group at the telephoto end when a, it is desirable in the first and second invention is a _{II 2T <6 ‥‥‥ (4)} .

By decreasing the coma aberration coefficient of the second group, the astigmatism coefficient of the second group can also be reduced. As a result, the eccentric astigmatism coefficient (IIIE) 2 of the second group is obtained.
Can be reduced, and thus the eccentric sensitivity of the second group can be 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) At least each of the second, third and fourth groups
It is characterized by having one aspherical surface. To reduce the coma and astigmatism coefficients of each group without increasing the number of lenses in each group, the second and third
It is necessary to increase the design freedom of each group by using at least one aspheric surface for each of the group and the fourth group.

(B-2) When the lateral magnification of the second lens unit at the telephoto end is β _2T

[0054]

(Equation 7) Satisfying the following conditions.

If the upper limit of conditional expression (5) 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 units is increased. It is necessary to move the principal point to the object side.
The group's power goes up. 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, and the amount of movement of the fourth lens unit approaches the image plane side at the telephoto end. .

(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 ,

[0057]

(Equation 8) Satisfying the following conditions.

The conditional expressions (6) and (7) are mainly for shortening the overall length of the lens while maintaining good optical performance. Of these, the conditional expression (6) 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. If the negative refractive power of the second lens unit becomes too weak beyond the upper limit, the fluctuation of aberration due to zooming is reduced, but the amount of movement of the second lens unit to obtain a predetermined zoom ratio increases, It is not good because the total length becomes longer.

Conditional expression (7) relates to the imaging magnification of the fifth lens unit.
If the lower limit of conditional expression (7) is exceeded and the magnification of the fifth lens unit is reduced, the effect of sufficiently shortening the overall length of the lens 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) In order to secure a moving space necessary for zooming of the second unit, the first unit is negative in order from the object side so that the image-side principal point is located as close to the image side as possible. It is desirable to be composed of a cemented lens in which a lens and a positive lens are cemented, and a meniscus lens having a convex surface facing the object side.

(A-5) The second unit is the third unit at the telephoto end.
It is desirable that a negative lens having a concave surface facing the image surface side in order from the object side, and a cemented lens in which a biconcave negative lens and a positive lens are cemented, so that a sufficient air gap from the group is obtained.

(A-6) The third lens unit is composed of a single meniscus negative lens having a concave surface facing the image plane in order to ensure a sufficient air gap with the second lens unit at the telephoto end. It is desirable.

(A-7) In order to favorably correct spherical aberration and chromatic aberration, it is preferable that 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) It is desirable that the fifth unit is composed of one negative lens in order to obtain a sufficient back focus.

(A-9) The aperture for adjusting the light amount is
It is desirable that the front lens is disposed between the second group and the third group in order to reduce the effective diameter of the front 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 shape 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, R is a paraxial radius of curvature, and B, C, D, and E are aspherical coefficients, respectively. And when

[0068]

(Equation 9) It is represented by the following expression. "E-X" 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 coma and astigmatism coefficients at the telephoto end of each embodiment. Table 3 shows the amount of tilt of the meridional image plane at an image height of 70% when each lens group is decentered by 0.01 mm at the wide-angle end and the telephoto end in each example. Table 4 shows the values of (PE) v and (IIIE) v for each group at the telephoto end.

[0070]

[Table 4]

[0071]

[Table 5] (Numerical Example 1)

[0072]

[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 (Numerical example 2)

[0073]

[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 (Numerical example 3)

[0074]

[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 (Numerical example 4)

[0075]

[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 (Numerical example 5)

[0076]

[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 (Numerical example 6)

[0077]

[Outside 7] no 1 2 3 asph 8 r -1.10892D + 00 k 4.38735D-02 B 2.27651D-02 4 5 6 C 2.13695D-02 D -9.58830D-02 E 2.29844D-02 no 1 2 3 asph 12 r 1.57019D +00 k -1.00063D + 00 B 8.55899D-02 4 5 6 C -3.03216D-02 D 6.71575D-03 E 3.75452D-02 no 1 2 3 asph 13 r -9.45828D + 02 k 0 B 1.25334D- 01 4 5 6 C 5.63002D-03 D -1.02458D-01 E 1.36106D-01 no 1 2 3 asph 16 r -2.34713D + 00 k -1.74867D + 01 B -1.14106D-01 4 5 6 C 2.11751D -01 D -2.22618D-01 E 1.05613D-01

[0078]

By adopting the above-described structure, it is possible to realize a zoom lens which is compact, has a small number of lenses, and has very small image plane tilt due to eccentricity of each group in all the groups. . In particular, it is possible to achieve a zoom lens that is suitable for a digital camera or a video camera in which the sensitivity is significantly increased due to the reduction in the image size and that can greatly improve the production efficiency.

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

FIG. 8 is an intermediate aberration diagram of the numerical example 1 of the present invention.

FIG. 9 is an aberration diagram at a telephoto end in Numerical Example 1 of the present invention;

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

FIG. 11 is an intermediate aberration diagram of the numerical example 2 of the present invention.

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

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

FIG. 14 is an intermediate aberration diagram of the numerical example 3 of the present invention.

FIG. 15 is an aberration diagram at a telephoto end in Numerical Example 3 of the present invention.

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

FIG. 17 is an intermediate aberration diagram of the numerical example 4 of the present invention.

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

FIG. 19 is an aberration diagram at a wide angle end according to Numerical Example 5 of the present invention.

FIG. 20 is an intermediate aberration diagram of the numerical example 5 of the present invention.

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

FIG. 22 is an aberration diagram at a wide angle end according to Numerical Example 6 of the present invention.

FIG. 23 is an intermediate aberration diagram of the numerical example 6 of the present invention.

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

FIG. 25 is an explanatory diagram of eccentric aberration in the optical system according to the present invention.

[Explanation of symbols]

 L1 First lens group L2 Second lens group L3 Third lens group L4 Fourth lens group L5 Fifth lens group SP Aperture FP Image plane

Continued on the front page F-term (reference) 2H087 KA02 KA03 MA15 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 SB14 SB001 SB33 HB DD9 JJ48 KK16 KK42 KZ54

Claims (13)

[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. By moving the second group and the fourth group in the optical axis direction, zooming and image plane variation correction accompanying zooming are corrected. when the distance from the first lens surface to the paraxial image plane TD, the focal length of the entire system at the telephoto end and f _T, satisfies the TD / f _T <1.2 condition: angle of an axial marginal ray at the wide angle end Of the third, fourth, and fifth groups at the telephoto end when the initial value of is 0, the initial value of the height is 1, and the initial value of the angle of the off-axis chief ray is -1.
The following coma aberration coefficients are II _3T , II _4T , II _5T, and the third-order astigmatism coefficients of the third, fourth, and fifth groups at the telephoto end are III _3T ,
When III _4T and III _5T are used, the condition of (II _3T ) ² + (II _4T ) ² + (II _5T ) ² <2 (III _3T ) ² + (III _4T ) ² + (III _5T ) ² <2 A zoom lens characterized by satisfaction. 2. A first fixed positive refractive power in order from the object side.
Group, second group with negative refractive power, third group with fixed positive refractive power,
It has five lens groups, a fourth lens group with positive refractive power and a fifth lens group with fixed negative refractive power, and moves the second lens group toward the image plane 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 distance from the first lens surface on the object side to the paraxial image plane is TD, and the focal length of the entire system at the telephoto end is when the f _T, satisfies the TD / f _T <1.2 condition: 0 first price angle of an axial marginal ray at the wide angle end, 1 the height of the initial price, the opening price of the angle of off-axis principal ray -1 3rd group, 4th group, 5th group at telephoto end
The following coma aberration coefficients are III _3T , II _4T , II _5T, and the third-order astigmatism coefficients of the third, fourth, and fifth groups at the telephoto end are III, respectively.
_{Assuming 3T} , III _4T , and III _5T , (II _3T ) ² + (II _4T ) ² + (II _5T ) ² <2 (III _3T ) ² + (III _4T ) ² + (III _5T ) ² <2 A zoom lens that satisfies the conditions. 3. The initial value of the angle of the on-axis marginal ray at the wide-angle end is 0, the initial value of the height is 1, and the initial value of the angle of the off-axis principal ray is-.
When the coma aberration coefficient of the second group at the telephoto end when the one and II _2T, claim 1 or 2 of the zoom lens satisfies the II _2T <6 following condition. 4. The zoom lens according to claim 1, wherein each of the second group, the third group, and the fourth group has at least one aspheric surface. 5. When the zoom ratio is Z, the lateral magnification β _2T of the second lens unit at the telephoto end is given by 4. The method according to claim 1, wherein the following condition is satisfied.
Or 4 zoom lenses. 6. The lens system according to claim 6, wherein a focal length of said 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 5, wherein the following condition is satisfied. 7. 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. 8. The lens system according to claim 1, wherein the first unit includes a cemented lens in which a negative lens and a positive lens are cemented, and a meniscus lens having a convex surface facing the object side.
The zoom lens of any one of the above. 9. 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 both the negative and positive lenses are cemented.
9. The zoom lens according to any one of items 1 to 8. 10. The zoom lens according to claim 1, wherein the third unit includes a single meniscus positive lens having a concave surface facing the image surface side. 11. 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. . 12. The zoom lens according to claim 1, wherein said fifth lens unit includes a single negative lens. 13. The zoom lens according to claim 1, wherein a stop for adjusting a light amount is disposed between the second group and the third group.