JPH11174323A - Large-aperture telephoto zoom lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a large-aperture telephoto lens which is suitable for single- lens reflex cameras and made sufficiently large in aperture by constituting four lens groups so as to be in a specific relation. SOLUTION: First to fourth lens groups G1 to G4 which have positive, negative, positive, and positive refracting power are provided in order from the object side. At the time of variable power from the wide-angle end to the telephoto end, at least the 2nd and 3rd lens groups G2 and G3 are moved so that the interval between the 1st and 2nd lens groups G1 and G2 increases, the interval between the 2nd and 3rd lens groups G2 and G3 decreases, and the interval between the 3rd and 4th lens groups G3 and G4 varies. Further, the conditions 0.7<f1/fT<1.0, -2.6<f2/Ymax<-2.0, 1.0<f3/fW<1.4, 1.3<f4/fW<1.8, and -0.004<1/f1+1/f2+1/f3/+1/f4<0.001 are made satisfied, where f1 to f4 are the focal lengths of the 1st to 4th lens groups G1 to G4 respectively, fW and fT are the focal lengths of the zoom lens at the wide-angle end and telephoto end respectively, and Ymax is the image circle radius of the zoom lens.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a large-aperture telephoto zoom lens, and more particularly to a large-aperture telephoto zoom lens suitable for a single-lens reflex camera or the like.

[0002]

2. Description of the Related Art Conventionally, in the field of telephoto zoom lenses for single-lens reflex cameras, JP-A-53-131852, JP-A-62-108218, and JP-A-64-3
JP-A-9542, JP-A-2-244110, JP-A-5-215966 and the like have proposed zoom lenses with a large aperture.

[0003]

However, in each of the embodiments of the above publications, the F-number is 2.
The diameter was only about 8, and the increase in diameter was not sufficiently achieved.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a large-aperture telephoto zoom lens which is suitable for a single-lens reflex camera or the like and has a sufficiently large aperture.

[0005]

In order to solve the above-mentioned problems, according to the present invention, a first lens unit having a positive refractive power and a second lens unit having a negative refractive power are arranged in order from the object side. A third lens group having a positive refractive power, and a fourth lens group having a positive refractive power. The first lens group and the second lens group are used for zooming from the wide-angle end to the telephoto end. Is increased, the distance between the second lens group and the third lens group is reduced, and the distance between the third lens group and the fourth lens group is changed. And the third lens group moves, the focal length of the first lens group is f1, the focal length of the second lens group is f2, and the focal length of the third lens group is f
3, the focal length of the fourth lens group is f4, the focal length of the zoom lens at the wide-angle end is fW, the focal length of the zoom lens at the telephoto end is fT, and the image circle radius of the zoom lens is Ymax. 0.7 <f1 / fT <1.0-2.6 <f2 / Ymax <-2.0 1.0 <f3 / fW <1.4 1.3 <f4 / fW <1.8-0. 004 <1 / f1 + 1 / f2 + 1 / f3 + 1 / f4 <0.
001 is provided, and a large-aperture telephoto zoom lens is provided.

According to a preferred aspect of the present invention, the first
The lens group is fixed during zooming. Further, it is preferable that the fourth lens group is fixed during zooming. Further, it is more preferable that an aperture stop is provided between the third lens group and the fourth lens group, and the aperture stop is fixed during zooming.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, the zoom lens of the present invention has a positive, negative, positive and positive refractive power arrangement. Then, the distance between the first lens group and the second lens group is increased,
The distance between the second lens group and the third lens group is reduced,
By changing the distance between the lens group and the fourth lens group, zooming from the wide-angle end to the telephoto end is performed.

Further, in the present invention, in addition to the above-described basic configuration, the following conditional expressions (1) to (5) are satisfied. 0.7 <f1 / fT <1.0 (1) -2.6 <f2 / Ymax <-2.0 (2) 1.0 <f3 / fW <1.4 (3) 1.3 <f4 / fW <1.8 (4) -0.004 <1 / f1 + 1 / f2 + 1 / f3 + 1 / f4 <0.001 (5)

Here, f1 is the focal length of the first lens group, f2 is the focal length of the second lens group, f3 is the focal length of the third lens group, and f4 is the focal length of the fourth lens group. Distance. FW is the focal length of the zoom lens at the wide-angle end, and fT is the focal length of the zoom lens at the telephoto end. Further, Ymax is the radius of the image circle of the zoom lens.

Conditional expression (1) defines an appropriate range for the focal length f1 of the first lens group. Conditional expression (1)
If the lower limit of the condition (1) is not reached, the focal length of the first lens group becomes too short, and it becomes difficult to satisfactorily correct spherical aberration at the telephoto end. Conversely, when the value exceeds the upper limit of conditional expression (1), the focal length of the first lens unit becomes too long, which causes an increase in the overall length of the zoom lens and an increase in the effective diameter of the second lens unit.

Conditional expression (2) defines an appropriate range for the focal length f2 of the second lens group. Conditional expression (2)
If the lower limit value is not reached, the focal length of the second lens group becomes too long, and it becomes difficult to obtain a zoom ratio (zoom ratio) of about three times. Conversely, when the value exceeds the upper limit of conditional expression (2), the focal length of the second lens group becomes too short, and it becomes difficult to satisfactorily correct spherical aberration, coma and astigmatism.

Conditional expression (3) defines an appropriate range for the focal length f3 of the third lens group. Conditional expression (3)
When the value is below the lower limit, the focal length of the third lens group becomes too short, and it becomes difficult to properly correct spherical aberration and coma. Conversely, when the value exceeds the upper limit of conditional expression (3), the third condition
Since the focal length of the lens group becomes too long, it becomes difficult to satisfactorily correct astigmatism over the entire zooming region.

Conditional expression (4) defines an appropriate range for the focal length f4 of the fourth lens group. Conditional expression (4)
When the value is below the lower limit, the focal length of the fourth lens group becomes too short, and it becomes difficult to satisfactorily correct spherical aberration and coma. Conversely, when the value exceeds the upper limit of conditional expression (4), the fourth condition
Since the focal length of the lens group becomes too long, it becomes difficult to satisfactorily correct astigmatism over the entire zooming region.

Condition (5) defines an appropriate range for the sum of the refractive powers of the first to fourth lens groups.
When the value falls outside the range defined by the upper limit and the lower limit of conditional expression (5), it becomes difficult to satisfactorily correct field curvature.

In the present invention, it is desirable that the first lens group is fixed during zooming. This is because if the largest and heaviest first lens group is moved during zooming, it is necessary to make the lens barrel structure more robust, and the weight of the lens system is significantly increased. Further, in order to simplify the lens barrel structure, it is desirable that the fourth lens group be fixed during zooming.

In order to secure a sufficient amount of peripheral light over the entire zooming region, it is preferable to dispose an aperture stop between the third lens unit and the fourth lens unit. In order to simplify the lens barrel structure, it is desirable to fix the aperture stop during zooming. Further, it is more preferable to fix both the aperture stop and the fourth lens unit during zooming, since the F-number does not change during zooming.

In order to effectively correct various aberrations including spherical aberration, the first lens group includes, in order from the object side, a negative meniscus lens having a convex surface facing the object side, and at least three object lenses. It is preferable to have a positive meniscus lens having a convex surface facing the side.

In order to effectively correct various aberrations such as spherical aberration and astigmatism, the second lens group includes, in order from the object side, a cemented lens formed by bonding a biconvex lens and a biconcave lens; It is preferable to have a cemented lens formed by bonding a biconcave lens and a positive meniscus lens having a convex surface facing the object side, and a negative meniscus lens having a concave surface facing the object side.

In order to effectively correct various aberrations such as spherical aberration and coma, the third lens group includes, in order from the object side, at least two biconvex lenses; It is preferable to have a cemented lens formed by bonding with a negative meniscus lens having a concave surface.

In order to effectively correct various aberrations such as spherical aberration, coma and distortion, the fourth lens group includes, in order from the object side, at least two positive meniscus lenses having convex surfaces facing the object side. A lens, a cemented lens formed by bonding a positive meniscus lens having a convex surface facing the object side and a negative meniscus lens having a convex surface facing the object side, a negative meniscus lens having a convex surface facing the object side, and a biconvex lens; It is preferable to have a positive meniscus lens having a convex surface facing the object side.

In the present invention, it is desirable that the following conditional expressions (6) to (9) are satisfied. 2.5 <fT / fW <4 (6) 3 <fW / Ymax <7 (7) FW <2 (8) FT <2 (9)

Here, as described above, fW is the focal length of the zoom lens at the wide-angle end, fT is the focal length of the zoom lens at the telephoto end, and Ymax is the image circle radius of the zoom lens. FW is the F number of the zoom lens at the wide angle end, and FT is the F number of the zoom lens at the telephoto end.

Any one of conditional expressions (6) to (9)
If the two conditional expressions cannot be satisfied, it is not preferable because it becomes difficult to achieve the large-aperture telephoto zoom lens aimed at by the present invention.

[0024]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram illustrating a lens configuration of a large-aperture telephoto zoom lens according to an embodiment of the present invention. The zoom lens according to the present embodiment includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a third lens group G3 having a positive refractive power. And a fourth lens group G4 having a positive refractive power.

In zooming from the wide-angle end to the telephoto end, the distance between the first lens group G1 and the second lens group G2 increases, and the distance between the second lens group G2 and the third lens group G3 decreases. Then, the second lens group G2 and the third lens group G3 are moved so that the distance between the third lens group and the fourth lens group changes. Note that the first lens group G1 and the fourth lens group G4 are fixed during zooming.

As shown in FIG. 1, the first lens group G1 is
In order from the object side, it is composed of a negative meniscus lens having a convex surface facing the object side and three positive meniscus lenses having a convex surface facing the object side. The second lens group G2 is
In order from the object side, a cemented lens formed by bonding a biconvex lens and a biconcave lens, a cemented lens formed by bonding a biconcave lens and a positive meniscus lens having a convex surface facing the object side, and a concave surface facing the object side And a negative meniscus lens.

The third lens group G3 is composed of, in order from the object side, two biconvex lenses and a cemented lens formed by bonding a biconvex lens and a negative meniscus lens having a concave surface facing the object side. I have. The fourth lens group G
Reference numeral 4 indicates, in order from the object side, two positive meniscus lenses having a convex surface facing the object side, a positive meniscus lens having a convex surface facing the object side, and a negative meniscus lens having a convex surface facing the object side. It is composed of a cemented lens, a negative meniscus lens having a convex surface facing the object side, a biconvex lens, and a positive meniscus lens having a convex surface facing the object side.

The third lens group G3 and the fourth lens group G
4, an aperture stop S is provided, and the aperture stop S is fixed together with the fourth lens group G4 during zooming. Also,
FIG. 1 shows a lens arrangement at the wide-angle end. When zooming to the telephoto end, the second lens group G2 moves to the image side.
The third lens group G3 once moves to the image side and then moves to the object side.

Table 1 below summarizes the data values of the present embodiment. In [Overall Specifications] of Table (1), f is the focal length, Bf is the back focus, FNO is the F-number,
2ω represents the angle of view. Also, in [Lens Specifications] of Table (1), the first column is the number of the lens surface from the object side, r in the second column is the radius of curvature of the lens surface, and d in the third column is d of the lens surface. The interval, ν in the fourth column is the Abbe number, and n in the fifth column is the d-line (λ = 587.
6 nm).

[0030]

Table 1 [Overall Specifications] f = 100.00 to 200.00 to 300.00 Bf = 76.11 FNO = 1.81 to 1.81 to 1.82 2ω = 24.50 to 12.32 to 8.19 ° [Lens specifications] rd ν n 1 319.2930 5.5000 25.50 1.804581 2 188.0570 1.5000 3 185.4550 25.5000 82.52 1.497820 4 827.2400 0.5000 5 196.8650 25.5000 82.52 1.497820 6 1797.6000 0.2000 7 174.9630 16.5000 82.52 1.497820 8 369.1290 (d8 = variable) 9 260.7180 14.0000 35.70 1.625882 10 -145.0840 5.0000 60.69 1.563840 11 62.4900 15.0000 12 -277.3740 4.0000 64.10 1.516800 13 71.6450 16.0000 26.05 1.784702 14 187.0970 24.0000 15 -67.2930 4.5000 53.93 1.713000 16 -474.0621 (d16 = variable) 17 1559.7300 12.0000 64.10 1.50 19 448.3910 11.0000 60.69 1.563840 20 -425.4470 0.2000 21 692.1900 15.0000 60.69 1.563840 22 -91.8050 5.0000 26.05 1.784702 23 -236.5516 (d23 = variable) 24 ∞ 1.3000 (Aperture stop S) 25 101.5590 10.0000 82.52 1.497820 2 6 306.4470 0.5000 27 87.7990 12.0000 82.52 1.497 820 28 125.7550 0.5000 29 80.8330 14.0000 64.10 1.516800 30 162.6040 5.0000 26.05 1.784702 31 77.4270 6.5000 32 254.6730 6.0000 60.69 1.563840 33 58.0440 17.0000 34 18 108.0000 8.0000 60.14 1.620409 35 -166.5200 0.5000 36.80 8.840 8.000 840 Variable interval in zooming] Wide-angle end Intermediate focal length Telephoto end f 100.0000 200.0000 300.0000 d8 5.8009 69.4662 88.2368 d16 43.5113 22.4747 1.5238 d23 46.1102 3.4815 5.6618 [Values for conditional expressions] (1) f1 / fT = 0.8246 (2) f2 / Ymax = −2.263 (3) f3 / fW = 1.228 (4) f4 / fW = 1.516 (5) 1 / f1 + 1 / f2 + 1 / f3 + 1 / f4 = −0.00168 (6) fT / fW = 3.000 (7) fW / Ymax = 4.630 (8) FW = 1.81 (9) FT = 1.81

FIGS. 2 to 4 are graphs showing various aberrations of the present embodiment. That is, FIG. 2 is a diagram of various aberrations at the wide-angle end,
FIG. 3 is a diagram of various aberrations in the intermediate focal length state, and FIG.
FIG. 4 is a diagram of various aberrations at the telephoto end. In each aberration diagram,
FNO is the F number, Y is the image height, d is the d-line (λ = 58
7.6 nm), and g indicates the g-line (λ = 435.8 nm). In the aberration diagram showing astigmatism, a solid line indicates a sagittal image plane, and a broken line indicates a meridional image plane. As is clear from the aberration diagrams, in this embodiment, various aberrations are favorably corrected in each focal length state, and excellent imaging performance is secured.

[0032]

As described above, according to the present invention,
Suitable for single-lens reflex cameras, etc., has a zoom ratio of about 3 times,
A large-aperture telephoto zoom lens having an angle of view of about 25 ° at the wide-angle end and an F-number of about 1.8 can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a lens configuration of a zoom lens according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating various aberrations of the present embodiment at a wide-angle end.

FIG. 3 is a diagram illustrating various aberrations of the present embodiment in an intermediate focal length state.

FIG. 4 is a diagram illustrating various aberrations at the telephoto end according to the present exemplary embodiment.

[Explanation of symbols]

 G1 first lens group G2 second lens group G3 third lens group G4 fourth lens group S aperture stop

Claims (9)

[Claims] 1. A first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a positive refractive power, in order from the object side. A fourth lens group having a distance between the first lens group and the second lens group at the time of zooming from the wide-angle end to the telephoto end, and the second lens group and the third lens group And at least the second lens group and the third lens group move so that the distance between the first lens group and the third lens group changes, so that the distance between the third lens group and the fourth lens group changes. The focal length is f1, the focal length of the second lens group is f2, the focal length of the third lens group is f3, the focal length of the fourth lens group is f4, and the focal length of the zoom lens at the wide-angle end. Is fW, and the focus of the zoom lens at the telephoto end is When the distance is fT and the radius of the image circle of the zoom lens is Ymax, 0.7 <f1 / fT <1.0-2.6 <f2 / Ymax <-2.0 1.0 <f3 / fW <1 1.4 1.3 <f4 / fW <1.8-0.004 <1 / f1 + 1 / f2 + 1 / f3 + 1 / f4 <0.
001. A large-aperture telephoto zoom lens which satisfies condition 001. 2. The large-aperture telephoto zoom lens according to claim 1, wherein the first lens group is fixed at the time of zooming. 3. The large-aperture telephoto zoom lens according to claim 1, wherein the fourth lens group is fixed during zooming. 4. The apparatus according to claim 1, wherein an aperture stop is provided between the third lens group and the fourth lens group, and the aperture stop is fixed during zooming. The large-aperture telephoto zoom lens described in the paragraph. 5. The first lens group includes, in order from the object side,
The large-aperture telephoto lens according to any one of claims 1 to 4, comprising a negative meniscus lens having a convex surface facing the object side and at least three positive meniscus lenses having a convex surface facing the object side. Zoom lens. 6. The second lens group includes, in order from the object side,
A cemented lens formed by bonding a biconvex lens and a biconcave lens, a cemented lens formed by bonding a biconcave lens and a positive meniscus lens having a convex surface facing the object side, and a negative meniscus lens having a concave surface facing the object side The large-aperture telephoto zoom lens according to any one of claims 1 to 5, further comprising: 7. The third lens group includes, in order from the object side,
The lens according to any one of claims 1 to 6, further comprising at least two biconvex lenses, and a cemented lens formed by bonding the biconvex lenses and a negative meniscus lens having a concave surface facing the object side. Large aperture telephoto zoom lens. 8. The fourth lens group includes, in order from the object side,
At least two positive meniscus lenses having a convex surface facing the object side, a cemented lens formed by bonding a positive meniscus lens having a convex surface facing the object side and a negative meniscus lens having a convex surface facing the object side, 2. A negative meniscus lens having a convex surface, a biconvex lens, and a positive meniscus lens having a convex surface facing the object side.
A large-aperture telephoto zoom lens according to any one of claims 1 to 7. 9. The focal length of the zoom lens at the wide-angle end is fW, the focal length of the zoom lens at the telephoto end is fT, and the image circle radius of the zoom lens is Yma.
x, and the F-number of the zoom lens at the wide-angle end is F
W, and the F-number of the zoom lens at the telephoto end is F
9. The method according to claim 1, wherein when T is satisfied, the following condition is satisfied: 2.5 <fT / fW <43 3 <fW / Ymax <7 FW <2 FT <2. Large aperture telephoto zoom lens.