JP2000214380A - Shooting lens - Google Patents

Abstract

(57) [Summary] [Problem] To enable short-range shooting. SOLUTION: A first lens unit L having a positive refractive power from the object side.
1, the second lens unit L2 having a negative refractive power, and the third lens unit L2 having a positive refractive power
Lens unit L3, stop SP, fourth lens unit L having positive refractive power
4. A fifth lens unit L5 having a negative refractive power is arranged, and iP indicates an image plane. When focusing from an infinite object distance side to a short distance side, at least the second lens unit L2
To the image plane side on the optical axis, and the fourth lens unit L4
Is moved to the object side on the optical axis to enable short-distance shooting, and at the same time, enlarge the magnification of the shot image.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photographic lens which can be suitably used for a still camera such as a single-lens reflex camera and a video camera, and which can perform a close-up photographing with a photographic magnification of about 1: 1.

[0002]

2. Description of the Related Art Conventionally, as a focusing method for a macro lens for a single-lens reflex camera, a method of moving the entire lens system on the optical axis, for example, Japanese Patent Application Laid-Open No. H05-14247.
4 and JP-A-8-201692, an optical system of a negative lens group is disposed on the image plane side of the optical system of the positive lens group to correct aberration fluctuation at a short distance. There is proposed a method or the like of performing the movement by moving the object.

[0003]

However, in these cases, for example, when trying to perform macro photography with a photographing magnification of about 1: 1, the amount of movement of the focus lens group becomes too large, and in recent years, autofocusing has become mainstream. Therefore, it becomes difficult to drive the electric focus lens.

For example, Japanese Patent Application Laid-Open Nos. 3-278012 and 4-110811 propose a method in which a plurality of focus lens groups are inner-focused while keeping the entire lens length constant. However, in each case, the maximum photographing magnification is only 0.5 times in spite of a telephoto system having a focal length of about 180 mm.

An object of the present invention is to solve the above-mentioned problems,
It is an object of the present invention to provide a photographing lens capable of photographing at a close distance.

[0006]

In order to achieve the above object, a photographic lens according to the present invention comprises, in order from the object side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, and a positive lens unit. A third lens group having a refractive power, a fourth lens group having a positive refractive power, and a fifth lens group having a negative refractive power. When focusing from an infinite object distance side to a short distance side, at least the second lens group is used.
The lens group is moved to the image plane side on the optical axis, and the fourth lens group is moved to the object side on the optical axis.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the illustrated embodiment. 1 to 4 show configuration diagrams of Examples 1 to 4, respectively, and show a first lens unit L having a positive refractive power from the object side.
1, the second lens unit L2 having a negative refractive power, and the third lens unit L2 having a positive refractive power
Lens unit L3, stop SP, fourth lens unit L having positive refractive power
4. A fifth lens unit L5 having a negative refractive power is arranged, and iP indicates an image plane.

In focusing from the infinite object distance side to the short distance side, at least the second lens unit L2 is moved to the image plane side on the optical axis, and the fourth lens unit L4 is moved to the object side on the optical axis. Enables close-up photography, and at the same time enlarges the magnification of the photographed image.

The first and fifth lens units L1 and L5 may have a zooming function by moving the entire lens unit or a part of the lens units in the optical axis direction.

Here, the main focusing operation is performed by the second lens unit L2, and the fourth lens unit L4 performs secondary focusing operation and correction of aberration fluctuation due to focusing.

Further, a positive spherical aberration is generated by the third lens unit L3 having a positive refractive power, and a negative spherical aberration generated by the second lens unit L2 is corrected. The lens diameter of the group L4 is reduced. At this time, it is preferable that the third lens unit L3 be fixed on the optical axis for simplification of the mechanism.

[0012] The first, second, and
The combined focal length of the third lens units L1, L2, L3 is F12
When it is 3, it is preferable to satisfy the following conditional expressions. F123> 0 (1)

According to the conditional expression (1), the size of the lens system of the fourth lens unit L4 can be reduced, and at the same time, effective spherical aberration correction can be performed.

In order to satisfy better optical performance,
The composite focal length F123 is to satisfy the following condition in the following conditional expression (2) normalized by the focal length F of the entire lens system. F123 / F> 0.3 (2)

The first, third, and fifth lens units L1, L
2, L5 can be simplified on the optical axis during focusing by simplifying the mechanism. Further, if the stop SP is moved between the second and fourth lens units L2 and L4, or if there is no off-axis ray eccentricity at the time of a small stop, the fourth and fifth lens units L
It is desirable to be fixed on the optical axis between L4 and L5.

Further, if high image quality is desired, it is preferable that at least one of the following conditional expressions is satisfied, where F is the focal length of the entire lens system and Fi is the focal length of the i-th lens unit Li. 0.3 <F1 / F <0.95 (3) 0.3 <| F2 / F | <0.7 (4) 0.25 <F4 / F <0.65 (5)

Conditional expression (3) relates to the refractive power of the first lens unit L1 and is a condition for maintaining a balance between miniaturization of the lens system and optical performance. Exceeding this upper limit is not preferable because the refractive power of the first lens unit L1 becomes weak and the overall length of the lens system becomes large. Conversely, if the refractive power exceeds the lower limit and the refractive power becomes too strong, it will be difficult to secure the back focus, and at the same time, many positive spherical aberrations will occur. It becomes difficult to do.

Conditional expression (4) relates to the refracting power of the second lens unit L2 which performs the main focusing action, and is used to achieve a good balance between the amount of movement of the second lens unit L2 during focusing and the correction of aberration variation accompanying the movement. Things. If the negative refractive power of the second lens unit L2 becomes too weak beyond the upper limit,
Since the amount of focus movement for securing a constant photographing magnification is large, the overall length of the lens is large. Also,
If the lower limit value is exceeded, fluctuations of various aberrations due to focusing become large, so that it becomes difficult to obtain high image quality over the entire photographing magnification.

Conditional expression (5) relates to the refracting power of the fourth lens unit L4 in order to shorten the overall length of the lens system while securing the back focus and to favorably correct off-axis aberrations. If the refractive power of the fourth lens unit L4 becomes too small beyond the upper limit, the overall length of the lens increases, and the off-axis aberration correction action is weakened, which is not good. On the other hand, conditional expression (5)
If the refractive power of the fourth lens unit L4 becomes too large beyond the lower limit of the above, the effect of the telefort system becomes too large,
At the same time, it is difficult to secure a predetermined back focus, and at the same time, high-order coma is generated, and it is difficult to correct this.

Further, when the combined focal length of the second, third, and fourth lens units L2, L3, and L4 at the time of infinite object distance photographing is F234, the following conditional expression normalized by the focal length F is satisfied. It is desirable to obtain higher image quality. 0.2 <F234 / F <0.55 (6)

Conditional expression (6) is the second condition in the infinite object distance state.
When the combined refractive power of the third and fourth lens units L2, L3, and L4 exceeds the upper limit of conditional expression (6), the focusing action of the second lens unit L2 is weakened, and the focus movement for obtaining a constant photographing magnification is performed. Since the amount becomes large, the lens system becomes large, and the Petzval sum becomes too small. On the other hand, when the refractive power exceeds the lower limit and becomes too large, a large positive spherical aberration occurs, and at the same time, it becomes difficult to correct aberration fluctuation during focusing.

The configuration of the lens system of this embodiment is as follows.
The lens unit L1 preferably has at least one negative lens and one positive lens, and preferably has a plurality of positive lenses. Further, it is preferable to have at least one cemented lens of a positive lens and a negative lens.

The second lens unit L2 preferably has at least one negative lens and one positive lens, and preferably has a plurality of negative lenses. Further, it is preferable to have at least one cemented lens of a positive lens and a negative lens.

The third lens unit L3 preferably has at least one positive lens with a convex surface facing the object side, and it is desirable to use a single lens structure for miniaturization of the optical system. Therefore, a plurality of lens configurations may be used. The fourth lens unit L4 preferably includes at least a negative lens having a concave surface facing the object side and a positive lens having a convex surface facing the image plane. It is desirable to use a plurality of positive lenses for high image quality.

The fifth lens unit L5 preferably has at least a negative lens with a concave surface facing the object side and a positive lens with a convex surface facing the image surface. desirable.

It is desirable that the stop SP is fixed on the optical axis at a position where the stop SP does not interfere with the movable lens group. Then, in order to further improve the optical performance, it is preferable to introduce an aspherical surface, a diffractive optical element, and a refractive index type optical material into the lens system. Further, the image displacement may be performed by decentering a part of the optical system to be used for image blur correction at the time of photographing.

The following table shows numerical examples of Examples 1 to 4.
Here, ri is the radius of curvature of the ith surface, di is the distance between the vertices of the lens surface on the ith optical axis, and Ni and νi are the refractive power and Abbe number of the ith lens, respectively.

Numerical Example 1 f = 70.00 Fno = 2.8 2ω = 34.4 ° r 1 = 103.257 d 1 = 5.00 N 1 = 1.677900 ν1 = 55.3 r 2 = -294.231 d 2 = 0.15 r 3 = 41.601 d 3 = 1.40 N 2 = 1.834807 ν2 = 42.7 r 4 = 21.808 d 4 = 10.00 N 3 = 1.638539 ν3 = 55.4 r 5 = 298.953 d 5 = 2.32 r 6 = -254.776 d 6 = 1.50 N 4 = 1.698947 ν4 = 30.1 r 7 = 33.985 d 7 = 1.11 r 8 = 53.236 d 8 = 1.50 N 5 = 1.511121 ν5 = 60.5 r 9 = 18.884 d 9 = 2.80 N 6 = 1.846659 ν6 = 23.8 r10 = 28.001 d10 = 12.81 r11 = 26.249 d11 = 2.50 N 7 = 1.846659 ν7 = 23.8 r12 = 32.341 d12 = 4.50 r13 = Aperture d13 = 15.76 r14 = -29.051 d14 = 1.20 N 8 = 1.761821 ν8 = 26.5 r15 = 35.323 d15 = 6.00 N 9 = 1.607292 ν9 = 59.4 r16 = -35.799 d16 = 0.20 r17 = -506.312 d17 = 3.50 N10 = 1.772499 ν10 = 49.6 r18 = -48.484 d18 = 0.20 r19 = 74.638 d19 = 4.00 N11 = 1.772499 ν11 = 49.6 r20 = -92.234 d20 = 2.37 r21 = -55.852 d21 = 1.20 N12 = 1.511121 ν12 = 60.5 r22 = 56.980 d22 = 7.74 r23 = -26.627 d23 = 1.40 N13 = 1.487490 ν13 = 70.2 r24 = -57.805 d24 = 0.15 r25 = -620.579 d25 = 6.00 N14 = 1.834000 ν14 = 37.2 r26 = -38.506

[0029] Lens group interval Shooting magnification d5 d10 d13 d20 0.25x 7.06 8.06 9.83 8.30 0.5x 13.19 1.93 4.34 13.79

Numerical Example 2 f = 99.50 Fno = 2.9 2ω = 24.5 ° r 1 = 121.481 d 1 = 1.80 N 1 = 1.846659 ν 1 = 23.8 r 2 = 35.224 d 2 = 9.50 N 2 = 1.589130 ν 2 = 61.2 r 3 = -103.354 d 3 = 0.15 r 4 = 42.836 d 4 = 3.80 N 3 = 1.772499 ν 3 = 49.6 r 5 = 181.410 d 5 = 2.12 r 6 = 1267.163 d 6 = 1.50 N 4 = 1.800999 ν 4 = 35.0 r 7 = 59.736 d 7 = 2.47 r 8 = -238.564 d 8 = 1.50 N 5 = 1.568728 ν 5 = 63.2 r 9 = 24.806 d 9 = 3.50 N 6 = 1.846659 ν 6 = 23.8 r10 = 38.947 d10 = 17.55 r11 = 116.501 d11 = 3.80 N 7 = 1.846659 ν 7 = 23.8 r12 = -111.340 d12 = 1.00 r13 = Aperture d13 = 26.44 r14 = -37.507 d14 = 1.20 N 8 = 1.761821 ν 8 = 26.5 r15 = 59.479 d15 = 4.30 N 9 = 1.516330 ν 9 = 64.2 r16 = -41.024 d16 = 0.30 r17 = -1664.108 d17 = 2.50 N10 = 1.834807 ν10 = 42.7 r18 = -63.601 d18 = 0.20 r19 = 48.620 d19 = 3.00 N11 = 1.772499 ν11 = 49.6 r20 = -224.720 d20 = 1.81 r21 = 323.985 d21 = 1.20 N12 = 1.581439 ν12 = 40.8 r22 = 22.235 d22 = 4.92 r23 = -45.736 d23 = 1.40 N13 = 1.487490 ν13 = 70.2 r24 = 83.821 d24 = 3.75 r25 = 42.177 d25 = 6.30 N14 = 1.487490 ν14 = 70.2 r26 = -92.652

Lens group interval Shooting magnification d5 d10 d13 d20 0.5x 7.44 12.22 18.45 9.80 1.0x 16.98 2.68 10.98 17.27

Numerical Example 3 f = 100.00 Fno = 3.5 2ω = 24.4 ° r 1 = 146.162 d 1 = 1.80 N 1 = 1.846659 ν 1 = 23.8 r 2 = 43.952 d 2 = 7.50 N 2 = 1.487490 ν 2 = 70.2 r 3 = -104.880 d 3 = 0.15 r 4 = 49.924 d 4 = 4.20 N 3 = 1.772499 ν 3 = 49.6 r 5 = 248.765 d 5 = 2.26 r 6 = -623.705 d 6 = 1.40 N 4 = 1.723420 ν 4 = 38.0 r 7 = 22.066 d 7 = 4.50 N 5 = 1.846659 ν 5 = 23.8 r 8 = 47.590 d 8 = 2.54 r 9 = -438.010 d 9 = 1.20 N 6 = 1.605620 ν 6 = 43.7 r10 = 73.943 d10 = 24.64 r11 = 75.773 d11 = 3.00 N 7 = 1.846659 ν 7 = 23.8 r12 = -402.249 d12 = 1.00 r13 = Aperture d13 = 25.54 r14 = -41.396 d14 = 1.30 N 8 = 1.698947 ν 8 = 30.1 r15 = 54.427 d15 = 4.80 N 9 = 1.487490 ν 9 = 70.2 r16 = -41.602 d16 = 0.30 r17 = 726.713 d17 = 2.80 N10 = 1.804000 ν10 = 46.6 r18 = -68.632 d18 = 0.20 r19 = 52.070 d19 = 3.00 N11 = 1.772499 ν11 = 49.6 r20 = -679.217 d20 = 1.66 r21 =- 265.959 d21 = 1.20 N12 = 1.620041 ν12 = 36.3 r22 = 25.840 d22 = 4.78 r23 = -39.616 d23 = 1.40 N13 = 1.487490 ν13 = 70.2 r24 = 120.123 d24 = 0.15 r25 = 48.135 d25 = 4.50 N14 = 1.712995 ν14 = 53.8 r26 =- 92.530

Lens group interval Shooting magnification d 5 d10 d13 d20 0.5 times 12.41 14.49 18.43 8.77 1.0 times 25.38 1.51 10.97 16.23

Numerical Example 4 f = 100.00 Fno = 4.0 2ω = 12.3 ° r 1 = 153.939 d 1 = 1.80 N 1 = 1.846659 ν 1 = 23.8 r 2 = 47.643 d 2 = 11.00 N 2 = 1.503779 ν 2 = 66.8 r 3 = -154.320 d 3 = 0.15 r 4 = 50.493 d 4 = 5.50 N 3 = 1.772499 ν 3 = 49.6 r 5 = 140.979 d 5 = 3.28 r 6 = 932.438 d 6 = 1.80 N 4 = 1.717362 ν 4 = 29.5 r 7 = 36.800 d 7 = 9.50 N 5 = 1.846659 ν 5 = 23.8 r 8 = -598.416 d 8 = 0.39 r 9 = 240.943 d 9 = 1.80 N 6 = 1.834000 ν 6 = 37.2 r10 = 37.934 d10 = 18.61 r11 = 52.295 d11 = 4.00 N 7 = 1.846659 ν 7 = 23.8 r12 = 140.273 d12 = 2.50 r13 = Aperture d13 = 23.91 r14 = -182.400 d14 = 1.20 N 8 = 1.749497 ν 8 = 35.3 r15 = 41.267 d15 = 4.00 N 9 = 1.487490 ν 9 = 70.2 r16 = -123.253 d16 = 0.15 r17 = 67.458 d17 = 4.00 N10 = 1.487490 ν10 = 70.2 r18 = -143.336 d18 = 0.20 r19 = 40.890 d19 = 3.50 N11 = 1.487490 ν11 = 70.2 r20 = 215.388 d20 = 1.50 r21 = 55.721 d21 = 1.20 N12 = 1.772499 ν12 = 49.6 r22 = 23.112 d22 = 2.55 r23 = -707.354 d23 = 1.40 N13 = 1.772499 ν13 = 49.6 r24 = 38.080 d24 = 31.56 r25 = 47.427 d25 = 5.50 N14 = 1.487490 ν14 = 70.2 r26 = 24100.020

Lens group interval Shooting magnification d 5 d10 d13 d20 0.5 times 8.81 13.08 12.86 12.56 1.0 times 17.86 4.03 4.23 21.18

The following table shows each conditional expression according to Numerical Examples 1-4.
It shows the numerical values in (1) to (6).

Numerical Example 1 Numerical Example 2 Numerical Example 3 Numerical Example 4 (1) F123 244.6 95.8 122.1 99.8 (2) F123 / FL 3.49 0.96 1.22 0.50 (3) F234 / F 0.43 0.27 0.27 0.29 (4) F1 / F 0.79 0.52 0.67 0.42 (5) | F2 / F 0.54 0 .38 0.43 0.41 (6) F4 / F 0.54 0.42 0.43 0.34

FIGS. 5A and 5B are aberration diagrams of Numerical Example 1, wherein (A) shows an infinite shooting distance and (B) shows a shooting magnification of 0.25.
(C) indicates that the photographing magnification is 0.5.

6 to 8 are aberration diagrams of Numerical Examples 2 to 4, in which (A) shows an infinite shooting distance, (B) shows a shooting magnification of 0.5, and (C) shows a shooting magnification of 1. 0.0 times.

FIG. 9 shows an embodiment of a camera using the photographing lens shown in the above-mentioned first to fourth embodiments. The lens barrel 10 incorporates the photographing lens 11 shown in the first to fourth embodiments. I have. Inside the camera body 20, a mirror 21 for reflecting the light flux taken in by the taking lens 11 upward,
Focusing plate 2 on which subject image is formed by taking lens 11
2. A penta roof prism 23 for converting a light beam from the focusing screen 22 into an erect image, an eyepiece 24 for observing a subject image formed on the focusing screen 22 and a silver halide film 25 are provided.

FIG. 9 shows the observation state, that is, the photographing standby state. When the release button is operated by the photographer, the mirror 21 is retracted from the optical path shown in FIG. It is captured. in this way,
By using the photographing lens described in Embodiments 1 to 4 for a camera, a camera capable of short-range photographing can be realized.

[0042]

As described above, the photographic lens according to the present invention can achieve an optical system with good optical performance capable of photographing at a photographic magnification of about 1: 1.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first embodiment.

FIG. 2 is a configuration diagram of a second embodiment.

FIG. 3 is a configuration diagram of a third embodiment.

FIG. 4 is a configuration diagram of a fourth embodiment.

FIG. 5 is an aberration diagram of Numerical Example 1.

FIG. 6 is an aberration diagram of Numerical Example 2.

FIG. 7 is an aberration diagram of Numerical Example 3.

FIG. 8 is an aberration diagram of Numerical Example 4.

FIG. 9 is a schematic configuration diagram of a camera using the photographing lenses of Examples 1 to 4.

[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 dd Line gg Line g. C Curve satisfying the sine condition ΔS Sagittal image plane ΔM Meridional image plane

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H087 KA02 KA03 MA09 PA11 PA20 PB14 QA02 QA07 QA14 QA17 QA21 QA22 QA25 QA32 QA34 QA42 QA46 RA32

Claims (5)

[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, a fourth lens group having a positive refractive power, and a negative lens in order from the object side. When focusing from an infinite object distance side to a short distance side, at least the second lens group is moved to the image plane side on the optical axis, and the fourth lens group is moved to the optical axis. A photographing lens characterized by being moved to an upper object side. 2. The photographic lens according to claim 1, wherein said first, third, and fifth lens groups are fixed on an optical axis during focusing. 3. The method according to claim 1, wherein the first,
The photographing lens according to claim 1, wherein the following conditional expression is satisfied, where F123 is a combined focal length of the second and third lens groups. F123> 0 4. The photographing method according to claim 1, wherein the following conditional expression is satisfied, where F is the focal length of the entire lens system and Fi is the focal length of the i-th lens unit. lens. 0.3 <F1 / F <0.95 0.3 <| F2 / F | <0.7 0.25 <F4 / F <0.65 5. The method according to claim 2, wherein the second,
The photographic lens according to any one of claims 1 to 9, wherein the following conditional expression is satisfied when the combined focal length of the third and fourth lens units is F234. 0.2 <F234 / F <0.55