JPS5984212A - Lens system equipped with auxiliary lens - Google Patents

Abstract

PURPOSE:To expand the range of a distance capable of short-distance photographing by making a focus adjustment by extending a main lens for a predetermined short-distance object or moving an auxiliary lens for a shorter-distance object when the auxiliary lens is mounted. CONSTITUTION:This lens system consists of the main lens and auxiliary lens mounted detachably between the main lens and an image surface. When the auxiliary lens is mounted, the focus adjustment is made by extending the main lens to the object side for the predetermined short-distance object. Then, for the shorter-distance object the auxiliary lens is moved to make the focus adjustment.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a lens system equipped with an auxiliary lens that can be attached or detached between the main lens and the film surface to change the focal length of the entire system, and particularly relates to a lens system that is equipped with an auxiliary lens that changes the focal length of the entire system by attaching and detaching the auxiliary lens between the main lens and the film surface. The present invention relates to a lens system equipped with an auxiliary lens having features for focusing on an object.

It is generally known that a converter lens is attached to the object world side or the image field side of a photographic lens to expand or reduce the focal length of the photographic lens while keeping the position of the focal plane constant. . In this case, the front converter lens system (d) attached to the object side of the photographic lens increases the size of the core converter lens, especially the diameter of the front lens, making it difficult to downsize the lens system. A rear converter lens system in which a converter lens is disposed on the image field side of a photographic lens is more advantageous in reducing the lens diameter than the front converter lens system.

As an example of taking advantage of this type of advantage, the present applicant has
7-46224, which proposes that by reducing the number of lenses that make up the converter lens, the storage space will be reduced when the converter lens is stored, and the camera body will be made more compact. .

Attach the auxiliary lens between the main lens and the film surface 1
When considering the focusing method for close-range objects when shooting..., in a lens system where the aperture mechanism or shutter mechanism is placed between the main lens and the auxiliary lens, the main lens, the auxiliary lens, and the aperture mechanism or shutter The so-called overall focus method, in which mechanisms and the like are moved together, complicates the mechanical structure. In general, partial focusing methods are used, such as front group focusing in which only the main lens is extended toward the object side, and rear group focusing in which only the auxiliary lens is extended toward the film surface.

However, the above-mentioned partial image magnification β-
For objects at close distances of about -0.2 or more, a short amount of lens movement is required, resulting in a significant decrease in the amount of peripheral light. For this reason, in a lens system whose outer diameter is made small for the purpose of downsizing the lens system,
Due to the decrease in the amount of peripheral light, the distance to objects that can be photographed at close range is limited.

The object of the present invention is to provide a lens system in which the focal length of the entire system can be changed by attaching and detaching an auxiliary lens between the main lens and the film surface.
To provide a lens system equipped with an auxiliary lens capable of expanding an object distance capable of close-up photography when the auxiliary lens is attached.

In order to achieve the above object, the present invention performs focusing when an auxiliary lens is attached to an object at a certain short distance by extending the main lens toward the object side. Furthermore, for objects at a closer distance, focusing is performed by moving the auxiliary lens.

By adopting such a focusing method, it is possible to obtain a lens system having good performance over a wide photographing distance, and it is also preferable in terms of eliminating unnecessary fuzzing at the periphery of the screen and correcting aberrations.

Furthermore, in the present invention, it is preferable that the auxiliary lens be installed between the f lens and the image plane at the same time as the main lens is moved toward the object side. This reduces wasted space in the lens system, which is advantageous for downsizing the lens system.

More preferably, the auxiliary lens is composed of a first positive lens, a second negative lens, and a third positive lens in order from the object side in order to perform good aberration correction. By configuring the auxiliary lens using positive and negative lenses in this way, aberrations can be corrected well over a wide object distance even when focusing on a close object.

In the present invention, focusing may be performed by moving the main lens and the auxiliary lens together at a normal object distance.

Next, numerical example 1 of the main lens to which the auxiliary lens of the present invention is to be attached will be shown below. Ri is the radius of curvature of the lens surface, Di
is the lens thickness or the distance between lens surfaces, Ni is the refractive index of the first lens material for the d-line, and νi is the Abbe number.

Numerical Example 1 Main lens F=100 FNO=1 : 2.8 2(l
+=55.3゜Curvature radius Lens thickness, spacing Refractive index Atsbe number R1= 36.4.19 D1=
15.58 N1=1.77250 ν1=49
．． 6R2='96.024 D2=2.
37R3=-128,393D3=4.67 N2=
1.72151 ν2=29.2R4= 32.4
70 D4=3.15R5=163.054
D5= 1.89 N5=1.58144 C3=
40.7R6=33.081 D6=10.1
9 N4=1.80610 ν4=40.9R7
= -73,705D7= 2.90R8= 0
．． 0 (aperture) Back focus b, f=73.71 Numerical Example 2 is shown in which an auxiliary lens is attached to the above-mentioned main lens.

In addition, in the following examples, when attaching the auxiliary lens,
The main lens is moved toward the object side so that the position of the imaging plane matches the position of the imaging plane when only the main lens is used.

Numerical Example 2 Combination of main lens and auxiliary lens F=163.92 FNO=1:4.7 2ω
=35.4°R1=36.419 D1=15
．． 58 N 1 = 1.77250 ν 1 = 49
．． 6R2=96.024D2=2.37R
3=-128,393D 3=4.67 N 2=1
．． 72151 ν2=29.2R, 42 32.47
0 D 4= 3.15R5= 163.054
D 5 = 1.89 N 3 = 1.58144 C 3 =
40.7R6=33.081D6=10.1
9 N 4=1.80610 ν4=40.9R7=
-73,705D 7= 2.90R8=
0.0 (iI intersection) D 8= 5.08R9=-1
99,103D 9= 4゜55 N 5=1.688
93 ν5=31.1R10=-36,190D10
= 2.64R11= -32,460D11= 1.
94 N 6=1.88300 Shiro=40.8R1
2-99,261D12=0.24R13=63
．． 474 D13=5.88 N7=1.532
56 Shift = 45.9 R14 = -115,048 Back focus l), f = 97.70 Similarly, Numerical Example 3 of the main lens to which the auxiliary lens of the present invention should be attached and the auxiliary lens on the main lens of Numerical Example 3 Numerical Example 4 when equipped is shown below.

Numerical Example 3 Main lens F=100 FNO=1:2.8 20)=5
9.3°R1= 34.594 D1=10.72
N1=1.77250ν1=49.6R2=109
．． 663 D2= 3.09R3=-1,58,800
D3=5.27 N2=1.72151 C2=29.
2R4=32.754. D4= 3.55R5=
260.1f'i0 D5=2.05 N5=1.
58144ν3 = 40.7R6 = 38.412
D6 = 8.58 N4 = 1.80610 shi4 =
40.917=-77,983D7=4.21R8
= Back focus b around 0.0, f=74.54 Numerical Example 4 Combination of main lens and auxiliary lens F=154.28 FNO=1:44 2ω-
40.5゜■E1. = 34.594 DI=1
．． 0.72 N ], = 1.77250 Si1 = 49
．． 6R2= 109.663 D2= 3.09R
3shi 158.8001) 3=5.27 N 2=1
．． 72151shi2=29.2R4=32.754
D4=3.55R5=260.160D
5=2.05 N 3=1.58144 ν3=4
0.7R6= 38.412 D6= 8.58
N4=1.80filOν4=40.9R7=-
77,983D 7= 4.21RR= o,
o@su)D FI= 4.48R9= 0. O
D 9 = 5.74 N 5 = 1.59270 ν5
=35.3R1(1=-36,6'/7 D10=
2゜26R11=-33,599D]1=2.1
6 N 6=1.77250 Shiro=49.6R12
= 93.495 DI2= 0.26R13=
67.145 D13= 6.85 N 7=1.
49831 Shift=65.0R14-633453 Pack focus b, f=89.76 FIG. 1 shows a sectional view of the main lens of Numerical Example 1 of the present invention, and FIG. 2 shows various aberration diagrams for an object at infinity. FIG. 3 is a sectional view of the lens when an auxiliary lens is attached to the main lens of FIG. 1, and FIG. 4 is a diagram of various aberrations for an object at infinity in the lens system of FIG. 3.

Figure 5 shows the imaging magnification β--0 of the lens system shown in Figure 3.
075. In this case, focusing is performed only by the main lens, and the air distance D7 is 7.53.

FIGS. 6 and 7 show a cross-sectional view of the lens and various aberration diagrams when the object is at a closer distance than the lens state shown in FIG. 5, β-0,2. Focusing in this case is performed only with the auxiliary lens, and the air distance at this time is D7=7.53.
D8=19.60.

FIG. 8 shows a sectional view of the main lens of Numerical Example 3 of the present invention, and FIG. 9 shows various aberration diagrams for an object at infinity. FIG. 10 shows a sectional view of the lens when an auxiliary lens is attached to the main lens of FIG. 8, and FIG. 11 shows various aberration diagrams for an object at infinity.

Figure 12 shows β-0,06 of the lens system shown in Figure 10.
5, focusing is performed only by the main lens and D7==8.27.

FIGS. 13 and 14 show lens cross-sectional views and various aberration diagrams when an object is closer than the state shown in FIG. 12, and when β=-0, 15. Focusing in this case is performed using an auxiliary lens, and the air spacing at this time is D7=8.27 and D7, respectively.
8=15.0.

[Brief explanation of the drawing]

Figures 1 and 2 are cross-sectional views of the lens and various aberrations of Numerical Example 1 of the present invention. Figures 3, 4, and 5 are cross-sectional views of the lens and various aberrations of Numerical Example 2 of the present invention. 6 and 7 are photographic magnification β=
8 and 9 are lens sectional views and various aberration diagrams for Numerical Example 3 of the present invention, 10, 11, and 12 is numerical example 4 of the present invention
FIGS. 13 and 14 are lens sectional views and various aberration diagrams when the imaging magnification is β-0, 15 in Numerical Example 4 of the present invention. Patent applicant Canon Corporation Spherical articulation extension aberration Distortion psychology c%] 8th mouth q wath 10 μs Required//eye function/? ρ 1,,-*””to 4, 11-r/

Claims (1)

[Claims] (1) In a lens system including a main lens and an auxiliary lens that is attached between the main lens and the image plane and is removable, when the auxiliary lens is attached, Focus adjustment is performed for a determined close object by extending the main lens toward the object side, and focus adjustment is performed for an even closer object by moving the auxiliary lens. A lens system equipped with an auxiliary lens. (2) The auxiliary lens according to claim 1, wherein the auxiliary lens is installed between the main lens and the image plane at the same time as the main lens is moved toward the object side. Lens system. (8) A lens system equipped with an auxiliary lens according to claim 1, wherein the auxiliary lens comprises, in order from the object side, a first positive lens, a second negative lens, and a third positive lens.