JPS60117209A - Zoom lens having stopper - Google Patents

Abstract

PURPOSE:To suppress fluctuation in the full aperture value in the zoom position of an intermediate region during zooming and to improve spherical aberration by setting the full aperture F-number so that the axial luminous flux of said number passes the periphery of the aperture of a stopper in a specific zoom range. CONSTITUTION:Zooming is accomplished by moving the 1st lens group I and the 2nd lens group II on the optical axis and an aperture diaphram is provided in the 2nd lens group. A stopper is disposed between the 2nd lens group II and the 3rd lens group III. A full aperture F-number is so set that the axial luminous flux of said number passes the periphery of the aperture of the stopper in the entire zoom range from 0.9Z to Z where the zooming magnification is designated as Z. Since the full aperture F-No. is determined by the bore of the stopper in the range from 0.9Z to Z zooming magnification, the luminous flux for an error difference can be cut by the stopper and therefore the full aperture performance is satisfactorily maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a zoom lens having a stopper with a fixed aperture in addition to the aperture. Many proposals have been made.

For example, USP 4.367.92'i' is a so-called two-group zoom lens with two lens groups, a negative refractive power lens group and a positive refractive power lens group, and the i of these two lens groups is
A stopper is provided at 11 to limit a portion of the lower light beam among the off-axis light beams in the middle of the screen, thereby eliminating υ coma flare and restricting excessive vignetting. This stopper is called a flare stopper mainly because it eliminates coma flare. Ideally, the aperture of the flare diaphragm is changed during zooming without blocking multi-axis rays, that is, without affecting the F-number. Further, USP 4,190,323 has a two-group zoom lens structure, and a stopper is provided behind the second lens group, and the stopper is moved differently from the movement of the second lens group during zooming. That is, when the amount of movement of the second lens group is △x2 and the amount of movement of the stopper is △X3, the movement is as follows: △X 3 =0.5△x2.

However, in all of these conventional zoom lenses, the aperture stop moves in the same way as the second lens group. Therefore, when the open aperture value is the same during zooming, the maximum aperture diameter is determined by the zoom position at the telephoto end, and
Since the effective diameters of the lenses before and after the aperture in the second lens group are also determined by the telephoto end, the yjJ pattern diameters at zoom positions other than the telephoto end need to be determined by an aperture that is slightly narrower than the aperture.

Many of the current aperture mechanisms have manufacturing or adjustment errors in the aperture blades, as shown in Figures 1 to 3, and even if there is an error in the maximum aperture, the effective diameter of the lens before and after the aperture can be adjusted accurately. If you hold it well, the aperture value at the telephoto end will hardly change. However, at zoom positions other than the telephoto end, there is an error in the aperture blades, and when the aperture changes, the open aperture value changes by the amount of change. In many cases, the spherical aberration increases because of the brightness. The adverse effects of this phenomenon occur more frequently as the zoom magnification becomes higher, and at positions slightly zoomed from the telephoto end to the wide-angle end (between the intermediate range). FIG. 4 shows the general shape of spherical aberration due to zooming, which is seen in many zoom lenses. As shown in FIG. 4, when the open aperture value becomes somewhat brighter at a position between the intermediate position and the telephoto end, the spherical aberration deteriorates rapidly.

Such a phenomenon often occurs in zoom lenses having current aperture mechanisms.

SUMMARY OF THE INVENTION The present invention aims to provide a zoom lens that suppresses fluctuations in the aperture value at the maximum aperture value at an intermediate zoom position during one zooming, and further maintains good spherical aberration. The feature of 1 is that in a zoom lens that performs zooming by moving at least two lens groups along the optical axis, an aperture stop is arranged closer to the object side than the lens group L1 that moves during zooming closest to the image plane or the lens group 1. 45 on the image side from the frontage aperture
With the refractive system in between and a stopper whose aperture remains unchanged, when the zoom position at the wide-angle end is the reference and the L1 meme magnification is Z, the maximum aperture is at least F within the entire zoom range from 0.92 to Z.
The axial light beam of the number is set so as to pass around the aperture of the +m stopper.

As in the present invention, the aperture diaphragm is placed on the lens group closest to the image plane or on the object side of the lens group that moves during zooming,
In a zoom lens, the light flux that passes through the aperture diaphragm is further diffusely refracted by the refracting system at the rear.When the diaphragm is stopped down in a part of the zoom range, the aperture shape of the aperture is a perfect circle. Since it has a polygonal shape, it is extremely possible to limit the area of the aperture shape and the luminous flux of the outer component of a perfect circle with a corresponding area by placing a stopper with an unchanged aperture at the rear of the refracting system. It becomes effective.

In particular, in the zoom type described above, it is preferable to predetermine the diameter of the axial light beam and the aperture of the stopper in the entire zoom range from 0.9Z to Z.

In order to satisfactorily achieve the objective of the present invention, the stopper is designed to prevent the intersection of the axial light beam of the open F-number and the outer ray of the yC beam reaching the outermost periphery of the photographic field near the zoom position at the telephoto end. It is preferable to set it in a position where

In the present invention, a stopper is provided behind the aperture diaphragm to supplement the aperture diameter of the f aperture diaphragm.

In particular, when the aperture diaphragm (aperture diaphragm) moves together with zooming, the change in diameter is large, so the restriction by a stopper is effective.

Although it is preferable that the stopper be moved along with zooming, it is not necessary to move the stopper over the entire zoom range, and it may be moved only within a predetermined zoom range (as shown in the embodiment described later).

The digit of one stopper 1ife is [lη11'' - the outermost 76 beams 711 of the light beams (as long as the position passes around the stopper, it may change in any way during zooming).

Next, each embodiment of the present invention will be described.

FIG. 5 and FIG. 7 each show Example 1 of the present invention. Actual hDi example 2
FIG. 3 is a sectional view of the lens.

Actual Jm example 1 is drawn with three lens groups of negative, positive and negative refractive power, $4 lens detail 1 and second lens tjl I
Zooming is performed by moving the I on the optical axis, and the aperture is located inside the second lens, and the focal length is 229 ~.
82. The aperture value of UfJ radiation is 1:4.0, and the stopper is the second lens j? 'li II and third lens f
If 7! It is placed between I. Therefore, at the far end of gl in FIG. 5(d), there is an open axial ray, and Il'l+
Of the 70 off-axis bundles L2 at the top of the book, a stopper is placed at the position where it intersects with the upper beam, and the 1st diameter is +- from the optical axis at the intersection.
It is equal to twice 6. 1 for focus! ilJ (=
The position of the stopper is fixed in the range of 70 to 82, and moves toward the image plane as the focal point becomes from 70 to 29.

In this embodiment, when the spherical aberration near the focal length f = 70 fJ becomes most rapidly overcorrected near the maximum diameter, and the aperture diameter becomes somewhat large due to errors in the aperture and the aperture, Since the overcorrected component of spherical aberration increases rapidly and deteriorates the optical performance at full aperture, a stopper is arranged as described above to maintain high performance. Furthermore, since the upper part of the off-axis light flux from the top to the middle of the screen can be restricted, coma flare can be effectively removed.

Example 2 For example, a 4-group configuration consisting of 4 lens groups with stop, negative, positive, and positive refractive powers, f=36 to 1311F number F
/l'a = 4.0 zoom lens. During zooming, the aperture diaphragm U in the second lens group 1 and the middle lens group 14i in the third lens group move in the same way when the lenses j1 and 1 move on the optical axis. 2nd lens group] and 4th lens group 1
v is a fixed foot during zooming, and the third lens m moves on the optical axis during zooming. The stopper is the third lens fl
There is a reed between Y, III and the 4th lens detail 1v, and the axial light is opened at the telephoto end. axial force) et al.
! '71 is equal to 241°·1. The position of the stopper is fixed in the range of focal length f=7o to f=131, and moves toward the image plane as f='70 to f=36.

In this Example 2, the sphere 1-1 aberration in the vicinity of f=100 has the most positive excess of f<Ii near the most dog mouth, and the actual 11
produces the same effect as Example 1.

In Examples 1 and 2, the zoom magnification at which the two light beams from the open l/number axis pass around the mouth of the stopper is 0856.05:<4.
It is.

In this way, it is good to have a stopper to adjust the luminous flux in the entire range from 09Z to Z. Then, the opening I-1 shape of the diaphragm is already close to a perfect circle, so the effect of the stopper becomes low.

As described above, in the first and second embodiments, the aperture 1 and the number 1i' it= during zooming are the same, but they do not necessarily have to be the same. For example, with a zoom lens that increases by 1 as you move toward the multi-lens side, if you move the stopper toward the object side as it gets darker, it will always intersect with the off-axis light beam for 1 h:
Since the flare can be placed at the same time, flare can be removed more effectively.

As described above, in the present invention, if the aperture diameter becomes large at a zoom position other than the telephoto end due to manufacturing error or adjustment error of the aperture diaphragm, at least the zoom magnification is 0.
In the range from 97 to ZO), the opening angle is determined by the inner diameter of the stopper, so the light flux corresponding to the above error can be cut off by the stopper, so that the opening performance can be maintained satisfactorily. Roughly within the range of J2, g, the value of rjR radiation FA can be maintained at 4n'6, so it is possible to maintain a positive (itt) exposure value, especially in the C method of measuring persimmons with a -111 Ruff camera. You can decide.

Next, numerical examples of the present invention will be described. In the numerical implementation θ, ILi is the radius of curvature of the first lens surface in order from the object side, Di is the first lens thickness and air gap in order from the object side, and Ni and νi are the i-th lens surfaces in order from the object side, respectively. These are the JHI refractive index and Atsube b of the glass of the IJ lens.

Numerical real IKII example 1 f=29~82 1'lhl: 4. , :5 2t=7
3.45°-V29.56°R13-Aperture-Re D13
-0.5 (JR17-79, 63D1'7-117 R], 8--4531.89 D18-Tomo 4.2 N
9-104666 9-23.9R19--90,4
71) 19-1.50 N 10-], 80518
1/No-25,4n2o-17,28020-3,0
9 R21-109, 23D21-3.30 N1.1. −
1.74.950 I'1l-35,3R22--53
, 17D22-ilJ Table I (23-diaphragm part 0-1J variation R13: rJF'r mouth aperture R23: stopper f = 36 ~ 131 1'/16 = 4.0 2* = 62
°〜18.76゜1ζl-140,85D I-2,5
0N 1-1.80518 ν1-25.412- 5
4.6'7 D 2-9.30 N 2-1.65B4
4 C2-50.91ζ3--2123.39 D3
-012R4-56, 28D 4-b, 97 N 3-
1.69680 shi3-55.515-270.49
D 5-iiJ odd R6-214, 21D 6-150
N 4-1.88300 C4-40.8R7-21
,30D 7-5.58 R8--59,61D B-1,20N 5-1.8B
300 shi 5-40.8rt 9- 73.22 D
9-2.32RIO-44,56DIO-4,54N
6-1.84666 Jiro 23', 91L11- -
41.57 Dll-1,81R12--32,131
)12-1.05 N 7-1.11:<400 ν
7-37.2I113- -177.59 1J13-
u1'd; ε■ζ14- Aperture I) 14-'iff change] H5-130, 3, 6D15-2.45 N B-1
, 65844ν B-50,9It16- -224.
31 1316-0.12Itl'i'-60,439
1'7-2.4.5 N 9-1.65844 ν 9
-50.9R18-145,241,118-0,12
R19-39,251319-2,26Nl0-]-,
72342shi10-38.0R20-89,121J2
0-0.12R21-25,861)21-7.44
NIL-1,51742shi11-52.4R22--2
47,59D22-5.90 N12-1.84666
ν12-23.9R23-19,58D2r5-4.
921ζ24- 143.91 1) 24-3.32
N13-], (i7003 shi13-4'i', 3R2
5--48, 33D25-variable (26-diaphragm D26-variable R27--52, 381J27-1.4 N14-1.
77250 Shi14-49.6R28-486,72D
2B-2, 48N15-1.51742 ν15-52
．． 4I also 29- -332.31 D29-2.45R
30-128'i'o IJ30-4.83 N16-
1.62299 1'16-58.21 is also 31- -5
3.21 n] 4: Aperture diaphragm 1tZ6: Stopper

[Brief explanation of the drawing]

Figures 1, 2, and 3 are explanatory diagrams of conventional aperture diaphragms. Figure 4 is an explanatory diagram showing typical variations in spherical aberration at each zoom position of a general zoom lens. Figure 5 , and FIG. 7 are diagrams of various aberrations at each zoom position in Examples 1 and 2 of the present invention. In the figure, I, l, m, and IV are respectively 1st. Second
．． The third and fourth lenses f7N1L+, I, 2 represent a luminous flux. Patent applicant: Canon Co., Ltd. '9. Yumi Nasaku): Inferior←Iku? E issue

Claims (2)

[Claims] (1) In a zoom lens that performs zooming by moving at least two lens groups along the optical axis, an aperture diaphragm is arranged on the lens group L that moves by the zoom lens closest to the image plane, or on the object side of the lens group. , when the aperture diaphragm is on the image plane side and the stopper whose aperture does not change across the refracting system is based on the zoom position at the wide-angle end, and the zoom magnification is Z, the entire zoom range from at least 0.92 to Z is provided. 1. A zoom lens having a stopper, wherein the axial light beam having an open F-number passes around the aperture of the stopper. (2) The stopper is located near the telephoto end zoom position,
2. A zoom lens having a stopper according to claim 1, wherein the stopper is set at a position where the axial light beam of the open FF member intersects with the outer light beam reaching the outermost periphery of the photographing screen.