JPH012011A - shooting lens - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a photographic lens that utilizes floating and is suitable for photographic cameras, video cameras, etc., and particularly relates to a photographic lens that utilizes floating that is suitable for photographic cameras, video cameras, etc. This relates to the photographic lens used.

[Prior art]

Utility Model No. 48-2 as a conventional lens system with variable image surface characteristics
There is one disclosed in Japanese Patent No. 823.

This allows the image plane characteristics to be varied by making it possible to manually move the floating mechanism found in bright retrofocus ultra-wide-angle lenses. In addition, as a lens system with variable image surface characteristics, JP-A-52-3
There is one presented in Publication No. 7445. This applies to lens systems that do not have the above-mentioned image plane characteristic deterioration correction means, and for lens systems that do have an image plane characteristic variable means independent of such image plane characteristic deterioration correction means. Met.

Furthermore, both are lens systems that have variable image retention at normal object distances.

For close-up objects, the magnification is high (and the depth of field becomes extremely shallow. For example, when photographing flowers at high magnification, the aperture must be narrowed down to capture the petals and flower core clearly). Therefore, it becomes impossible to obtain a photographic effect in which the background is greatly blurred and only the petals and flower core stand out.

Therefore, although the aperture of macro lenses is increasing, it is not possible to take full advantage of the large aperture of the serica lens.

The present invention utilizes the advantage of a large aperture, especially when photographing objects at close range, while also changing the image plane by utilizing the air gap obtained by floating so that the entire object is in focus, even for objects other than flat objects. The objective is to provide a photographic lens that allows

FIGS. 1 and 3 are cross-sectional views of lenses corresponding to numerical example 1°2 of the present invention, respectively. In the figure, I, n, and Ill are the 11th, second, and third lens groups, all of which have positive refractive power. IV is a fourth lens group with negative refractive power. or,
The arrows indicate the movement direction of each lens group when focusing from an object at infinity to an object at a short distance, and each group moves simultaneously.

In this example, as described above, the three first, second, and third lens groups with positive refractive power are arranged in order from the object side, and the fourth lens group with negative refractive power is arranged behind them, As a whole, the photographic lens is composed of four lens groups. In particular, by arranging the fourth lens group with negative refractive power, the degree of freedom in refractive power arrangement of the three lens groups with positive refractive power placed on the object side is increased, and various aberrations can be corrected effectively in the standard state. I'm going to

Furthermore, by increasing the combined positive refractive power of all three lens groups, the overall amount of movement of the three lens groups during focusing is reduced, and the overall length of the lens is shortened.

When focusing from an object at infinity to an object at a short distance, the four lens groups LI
So-called floating is performed in which I, m, and IV are each independently moved toward the object side.

As a result, compared to the case where two lens groups, or particularly three lens groups, are simply moved and floated, aberration fluctuations due to changes in imaging magnification are further reduced (and a wide range of objects from infinity to close objects can be seen). This enables excellent aberration correction for objects such as

FIGS. 2 and 4 are cross-sectional views of the photographic lenses shown in FIGS. 1 and 3 when focused on a short-distance object. In the figure, the arrow below the fourth lens group IV indicates the direction in which the fourth lens group is moved manually or the like in order to change the image plane characteristics. For example, if the fourth lens group IV is moved in the direction A, the height of the light incident on the fourth lens group will be lowered, and the image plane can be tilted in the direction opposite to the object side. This makes it possible to clearly photograph convex objects such as buds by reducing the amount of aperture. On the other hand, when the fourth lens group IV is moved in direction B, the height of the light incident on the fourth lens group increases, the image plane tilts toward the object side, and the aperture is narrowed from the petals to the flower core. It becomes possible to take pictures with a small aperture amount.

Moreover, it is possible to obtain special effects not only for such subjects.

On the other hand, although all the lens groups were moved in the embodiments described above, some of the lens groups may be fixed if a moving space is formed by floating. It is also effective to apply this method even when the number of lens groups is 4 or less.

Furthermore, in order to properly correct various aberrations of the entire screen in this embodiment, in order from the object side, the lens group consists of three lenses: a positive lens, a meniscus-shaped positive lens, a negative lens, and a second lens. The group is a composite lens of a negative lens and a positive lens, the 3-element lens in 2 groups of positive lenses, the 3rd lens group is at least one positive lens, and the 4th lens group is a meniscus-shaped negative lens with a convex surface facing the object side. One method is to construct it from

As explained above, by moving the fourth lens group independently of the other lens groups when photographing a close object, the image surface characteristics can be changed.

Next, numerical examples of the present invention will be shown. In numerical examples,
R4 is the radius of curvature of the i-th lens surface from the object side, Di
is the thickness or air gap of the i-th lens from the object side, and Ni and Vi are the refractive index and Abbe number of the i-th glass from the object side, respectively.

Numerical Example 1 F=52. OFNO=1: 2.55 2W=4
6゜R1= 376.13 D1=2.23 N
1=1.72000 V1=50.2R2=-64,
2602=0.15 R3= 21.91 D3=3.04 N2=
1.78590 V2=44.2R4=76.5
5 D4=1.05R5=-169,06D5=1.
19 N5=1.60342 V3=38.0R
6= 18.86 D6= R7= 0. OD7=4.05 R8=-15,86D8=1.62 N4=1.
69895 V4=30. IRQ = -78,7
5D9=3.71 N5=1.77250 V5
=49.6RIO=-19,72D10=0.15R
11=-185, 31D11=2.52 N6=1.
77250 V6=49.6R12=-40,37
D12= R13= 128.95 013=2.53 N7=
1.48749 V7=70.2R14=-145,
10D14=R15=102.15 D15=1.82
N8=1.51633 V8=64. lR16=
46.36 Numerical Example 2 F=50.4 FNO=1: 2.55 2
W=46°R1=-238, 11DI=2.20
N1=1.77250 V1=49.6R2=-6
3,62D2=0.15 R3= 21.61 D3=2.79 N2=
1.80610 V2=40.9R4=73.2
4 D4=0.68R5=-384,71D5=2.
37 N5=1.60342 V3=38. OR
6= 18.31 D6= R7= 0. OD7=4.0O R8=-15,34D8=1.23 N4=1.
68893 V4=31.1R9=292.73
D9=4.17 N5=1.71300
V5=53.8R10=-18,76D10=0.1
5R11=-167, 69D11=2.54 N6
=1.88300 V6=40.8R12=-
43,81D12= R13= 182.74 013=2.50'
N7=1.54814 V7=45.8R1
4=-250,96DI4=R15=54.54 D15=1.80
N8=1.51633 V8=64. lR16=
39.64

[Brief explanation of the drawing]

Figures 1 and 3 are cross-sectional views of the lens in Example 1.2 of the present invention, and Figures 2 and 4 are cross-sectional views of the lens when focusing on a short-distance object in Numerical Example 1.2. Figures 5, 6, 7, and 8 are aberration diagrams for an infinite object distance in Numerical Example 1, aberration diagrams for a short-distance object, and 4th lens group for a short-distance object, respectively. 9, 10, 11, and 12 are aberration diagrams when the fourth lens group is moved toward the image side for a close object.
, an aberration diagram at an infinite object distance, an aberration diagram for a close object, an aberration diagram when the fourth lens group is moved toward the object side for a close object, and an aberration diagram when the fourth lens group is moved toward the image side for a close object. FIG. In the figure, 1. n, III, and IV are the first, second, and
The third and fourth lens groups and arrows indicate the moving direction of each lens group when focusing from an object at infinity to an object at a short distance.

Claims (4)

[Claims] (1) In a lens system that is composed of multiple lens groups and in which focusing is performed by moving all or some of the lens groups, the air spacing obtained by focusing at least one of the lens groups is A photographic lens characterized by changing the image plane characteristics by moving the lens. (2) The photographic lens according to claim 1, wherein the photographic lens is capable of photographing with a magnification exceeding 0.1 times. (3) The photographing lens according to claim 1, wherein the lens group closest to the image side among the plurality of lens groups has negative refractive power and is moved to change image surface characteristics. (4) The photographic lens according to claim 3, wherein among the plurality of lens groups, all but the lens group closest to the image side have positive refractive power.